Publications
2022 |
Kandemir, Ayse Cagil; Donmez, Fatma; Davut, Kemal; Can, Hatice Kaplan: Design and fabrication of polymer micro/nano composites with two-level
mechanical reinforcing procedure. POLYMER COMPOSITES, 43 (7), pp. 4609-4625, 2022, ISSN: 0272-8397. (Type: Journal Article | Abstract | Links | BibTeX) @article{WOS:000791768700001b, title = {Design and fabrication of polymer micro/nano composites with two-level mechanical reinforcing procedure}, author = {Ayse Cagil Kandemir and Fatma Donmez and Kemal Davut and Hatice Kaplan Can}, doi = {10.1002/pc.26717}, issn = {0272-8397}, year = {2022}, date = {2022-07-01}, journal = {POLYMER COMPOSITES}, volume = {43}, number = {7}, pages = {4609-4625}, publisher = {WILEY}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {Biocompatible composite production was accomplished by utilizing two-level hierarchical approach for mechanical reinforcement. A well-known commodity polymer; low-density polyethylene (LDPE), which has high-fracture toughness, yet low strength and modulus was used as the main matrix material. As the first step of hierarchy, ductile LDPE was blended with brittle polyvinylpyrrolidone (PVP), which is an eco-friendly, nontoxic and biocompatible polymer. This resulted in slight decrease of strength and drastic reduction of toughness (%70), yet modulus was increased by 78%. As the second level of hierarchy, PVP composites were introduced in LDPE. Nano-scaled Halloysite clay and micro-scaled spherical Silica particles were utilized as additives in the aforementioned PVP composites. The reason for the choice of these particles is that they are nontoxic, low-cost and in the case of Halloysite; abundant in nature. Owing to the implementation of the second level; modulus improvement was further enhanced to 150%, with additional benefits of strength increase up to 17% and less reduction in fracture toughness (minimum 51% reduction). Dynamic mechanical analysis also supported these outcomes that storage modulus of composites are higher than both LDPE and LDPE-PVP blend. The proposed biocompatible composites in the end of this study would be utilized in biomedical applications necessitating mechanical improvements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Biocompatible composite production was accomplished by utilizing two-level hierarchical approach for mechanical reinforcement. A well-known commodity polymer; low-density polyethylene (LDPE), which has high-fracture toughness, yet low strength and modulus was used as the main matrix material. As the first step of hierarchy, ductile LDPE was blended with brittle polyvinylpyrrolidone (PVP), which is an eco-friendly, nontoxic and biocompatible polymer. This resulted in slight decrease of strength and drastic reduction of toughness (%70), yet modulus was increased by 78%. As the second level of hierarchy, PVP composites were introduced in LDPE. Nano-scaled Halloysite clay and micro-scaled spherical Silica particles were utilized as additives in the aforementioned PVP composites. The reason for the choice of these particles is that they are nontoxic, low-cost and in the case of Halloysite; abundant in nature. Owing to the implementation of the second level; modulus improvement was further enhanced to 150%, with additional benefits of strength increase up to 17% and less reduction in fracture toughness (minimum 51% reduction). Dynamic mechanical analysis also supported these outcomes that storage modulus of composites are higher than both LDPE and LDPE-PVP blend. The proposed biocompatible composites in the end of this study would be utilized in biomedical applications necessitating mechanical improvements. |
Dogu, Merve Nur; Davut, Kemal; Obeidi, Muhannad Ahmed; Yalcin, Mustafa Alp; Gu, Hengfeng; Low, Thaddeus Song En; Ginn, Jon; Brabazon, Dermot: Recrystallization and grain growth kinetics of IN718 manufactured by
laser powder bed fusion. JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 19 , pp. 4242-4257, 2022, ISSN: 2238-7854. (Type: Journal Article | Abstract | Links | BibTeX) @article{WOS:000852777600001, title = {Recrystallization and grain growth kinetics of IN718 manufactured by laser powder bed fusion}, author = {Merve Nur Dogu and Kemal Davut and Muhannad Ahmed Obeidi and Mustafa Alp Yalcin and Hengfeng Gu and Thaddeus Song En Low and Jon Ginn and Dermot Brabazon}, doi = {10.1016/j.jmrt.2022.06.157}, issn = {2238-7854}, year = {2022}, date = {2022-07-01}, journal = {JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T}, volume = {19}, pages = {4242-4257}, publisher = {ELSEVIER}, address = {RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS}, abstract = {The recrystallization and grain growth behaviour of IN718 alloy additively manufactured by laser powder bed fusion (L-PBF) is presented herein. The effects of three different temperatures (1050, 1150 and 1250 degrees C) and holding times (15, 45 and 90 min) were investigated. The texture evolution of the samples was recorded via electron backscatter diffraction (EBSD). The as-built sample is composed of bowl-shaped melt pools, a chessboard-like grain pattern and has a cube texture 100<001>. Recrystallized grains were observed in the samples treated at 1150 degrees C for 15 min, as well as the samples treated for longer periods and at higher temperatures. Recrystallization was observed to start from high dislocation density regions, including the overlapping melt pools and the borders of the chessboard-like pattern. The initial cube texture transforms into a first-generation cube-twin texture 122<212> via a twinning-assisted recrystallization mechanism. Then, those recrystallization nuclei sweep through the high defect density matrix; during which almost no new twins are formed. The samples treated at 1250 degrees C are almost completely recrystallized, which forms a weaker cube texture and a stronger P-orientation 011<112>. However, the growth of recrystallized grains is very limited due to the presence of non-coherent precipitates. (C) 2022 The Author(s). Published by Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The recrystallization and grain growth behaviour of IN718 alloy additively manufactured by laser powder bed fusion (L-PBF) is presented herein. The effects of three different temperatures (1050, 1150 and 1250 degrees C) and holding times (15, 45 and 90 min) were investigated. The texture evolution of the samples was recorded via electron backscatter diffraction (EBSD). The as-built sample is composed of bowl-shaped melt pools, a chessboard-like grain pattern and has a cube texture 100<001>. Recrystallized grains were observed in the samples treated at 1150 degrees C for 15 min, as well as the samples treated for longer periods and at higher temperatures. Recrystallization was observed to start from high dislocation density regions, including the overlapping melt pools and the borders of the chessboard-like pattern. The initial cube texture transforms into a first-generation cube-twin texture 122<212> via a twinning-assisted recrystallization mechanism. Then, those recrystallization nuclei sweep through the high defect density matrix; during which almost no new twins are formed. The samples treated at 1250 degrees C are almost completely recrystallized, which forms a weaker cube texture and a stronger P-orientation 011<112>. However, the growth of recrystallized grains is very limited due to the presence of non-coherent precipitates. (C) 2022 The Author(s). Published by Elsevier B.V. |
Aktarer, Semih Mahmut; Kucukomeroglu, Tevfik; Davut, Kemal: Texture Evolution of Friction Stir-Processed Dual-Phase Steel. METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND
MATERIALS SCIENCE, 53 (5), pp. 1889-1905, 2022, ISSN: 1073-5623. (Type: Journal Article | Abstract | Links | BibTeX) @article{WOS:000770727700001, title = {Texture Evolution of Friction Stir-Processed Dual-Phase Steel}, author = {Semih Mahmut Aktarer and Tevfik Kucukomeroglu and Kemal Davut}, doi = {10.1007/s11661-022-06644-y}, issn = {1073-5623}, year = {2022}, date = {2022-05-01}, journal = {METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, volume = {53}, number = {5}, pages = {1889-1905}, publisher = {SPRINGER}, address = {ONE NEW YORK PLAZA, SUITE 4600, NEW YORK, NY, UNITED STATES}, abstract = {Evolution of crystallographic texture and local strains in different zones of a dual-phase steel subjected to severe plastic deformation by friction stir process was examined by electron backscatter diffraction technique. Misorientations, which were expressed by the values of grain orientation spread and kernel average misorientation (KAM), increased from the thermomechanical affected zone (TMAZ) to pin-affected stir zone (PE-SZ). KAM maps showed that the highest local strain appeared in the PE-SZ. Misorientation distributions were found to be consistent with microhardness distributions in the processed region. The crystallographic texture of base metal, heat-affected zone, and TMAZ was similar. Recrystallization and deformation texture components were observed at stir zones, and recrystallization texture components decreased drastically at PE-SZ. Rotated cube, goss and rotated goss texture components were detected at PE-SZ. Rotated cube texture component indicates partial recrystallization after plastic deformation. Shear texture components were determined using shear direction (SD) as reference. Different shear texture components (111), (112), and (101) || SD were found in the processed region revealing the differences in material flow and plastic deformation at each zone. Some other texture components were found to be resulting from transformation of austenite into ferrite/martensite, by taking orientation relationship between those parent and product phases. Taylor factor values of all zones were calculated in order to understand the influence of texture on mechanical properties. The results indicate that crystallographic texture has a minor influence on hardness compared to grain refinement and dislocation density.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Evolution of crystallographic texture and local strains in different zones of a dual-phase steel subjected to severe plastic deformation by friction stir process was examined by electron backscatter diffraction technique. Misorientations, which were expressed by the values of grain orientation spread and kernel average misorientation (KAM), increased from the thermomechanical affected zone (TMAZ) to pin-affected stir zone (PE-SZ). KAM maps showed that the highest local strain appeared in the PE-SZ. Misorientation distributions were found to be consistent with microhardness distributions in the processed region. The crystallographic texture of base metal, heat-affected zone, and TMAZ was similar. Recrystallization and deformation texture components were observed at stir zones, and recrystallization texture components decreased drastically at PE-SZ. Rotated cube, goss and rotated goss texture components were detected at PE-SZ. Rotated cube texture component indicates partial recrystallization after plastic deformation. Shear texture components were determined using shear direction (SD) as reference. Different shear texture components (111), (112), and (101) || SD were found in the processed region revealing the differences in material flow and plastic deformation at each zone. Some other texture components were found to be resulting from transformation of austenite into ferrite/martensite, by taking orientation relationship between those parent and product phases. Taylor factor values of all zones were calculated in order to understand the influence of texture on mechanical properties. The results indicate that crystallographic texture has a minor influence on hardness compared to grain refinement and dislocation density. |
Mustafa Neşet Çınar Aleandro Antidormi, Viet-Hung Nguyen Alessandro Kovtun Samuel Lara-Avila Andrea Liscio Jean-Christophe Charlier Stephan Roche ; Sevinçli, Hâldun: Toward Optimized Charge Transport in Multilayer Reduced Graphene Oxides. Nano Letters, 22 (6), pp. 2202-2208, 2022, ISSN: 1530-6984. (Type: Journal Article | Links | BibTeX) @article{Çınar2022, title = {Toward Optimized Charge Transport in Multilayer Reduced Graphene Oxides}, author = { Mustafa Neşet Çınar, Aleandro Antidormi, Viet-Hung Nguyen, Alessandro Kovtun, Samuel Lara-Avila, Andrea Liscio, Jean-Christophe Charlier, Stephan Roche, and Hâldun Sevinçli}, url = {https://doi.org/10.1021/acs.nanolett.1c03883}, doi = {10.1021/acs.nanolett.1c03883}, issn = {1530-6984}, year = {2022}, date = {2022-03-23}, journal = {Nano Letters}, volume = {22}, number = {6}, pages = {2202-2208}, publisher = {American Chemical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sousa, L; Alves, A C; Costa, N A; Gemini-Piperni, S; Rossi, A L; Ribeiro, A R; Simões, S; Toptan, F: Preliminary tribo-electrochemical and biological responses of the Ti-TiB-TiCx in-situ composites intended for load-bearing biomedical implants. Journal of Alloys and Compounds, 896 , pp. 162965, 2022, ISSN: 0925-8388. (Type: Journal Article | Abstract | Links | BibTeX) @article{SOUSA2022162965, title = {Preliminary tribo-electrochemical and biological responses of the Ti-TiB-TiCx in-situ composites intended for load-bearing biomedical implants}, author = {L Sousa and A C Alves and N A Costa and S Gemini-Piperni and A L Rossi and A R Ribeiro and S Simões and F Toptan}, url = {https://www.sciencedirect.com/science/article/pii/S0925838821043759}, doi = {https://doi.org/10.1016/j.jallcom.2021.162965}, issn = {0925-8388}, year = {2022}, date = {2022-01-01}, journal = {Journal of Alloys and Compounds}, volume = {896}, pages = {162965}, abstract = {Poor tribocorrosion resistance of Ti and its alloys remains as a concern for load-bearing biomedical implants. Despite being an effective method to improve tribocorrosion resistance, titanium matrix composites (TMCs) have yet to be used in this type of applications. In-situ TiB (titanium boride) and TiC (titanium carbide) reinforcement phases have been considered as one of the best options to produce TMCs once these phases present high compatibility and strong interfacial bonding with Ti. Although the effect of these phases on the mechanical properties of Ti has been thoroughly researched in the last years, their effect on corrosion, tribocorrosion and biocompatibility of Ti is yet to be fully understood. In this work, in-situ Ti-TiB-TiCx composites obtained by reactive hot pressing showed identical corrosion response compared to the unreinforced Ti but displayed improved tribocorrosion behaviour. Under 0.5 N load, composites presented as average a reduction of 51% in wear volume loss and under 10 N the reduction was up to 93%. Early biological tests showed promising results, as composites were biocompatible and induced osteoblasts spreading and possibly proliferation most probably due to composite chemistry and surface hardness.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Poor tribocorrosion resistance of Ti and its alloys remains as a concern for load-bearing biomedical implants. Despite being an effective method to improve tribocorrosion resistance, titanium matrix composites (TMCs) have yet to be used in this type of applications. In-situ TiB (titanium boride) and TiC (titanium carbide) reinforcement phases have been considered as one of the best options to produce TMCs once these phases present high compatibility and strong interfacial bonding with Ti. Although the effect of these phases on the mechanical properties of Ti has been thoroughly researched in the last years, their effect on corrosion, tribocorrosion and biocompatibility of Ti is yet to be fully understood. In this work, in-situ Ti-TiB-TiCx composites obtained by reactive hot pressing showed identical corrosion response compared to the unreinforced Ti but displayed improved tribocorrosion behaviour. Under 0.5 N load, composites presented as average a reduction of 51% in wear volume loss and under 10 N the reduction was up to 93%. Early biological tests showed promising results, as composites were biocompatible and induced osteoblasts spreading and possibly proliferation most probably due to composite chemistry and surface hardness. |
Gökbulut, Belkıs; Inanç, Arda; Topcu, Gokhan; Ozcelik, Serdar; Demir, Mustafa M; Inci, Naci M: Hybrid photonic-plasmonic mode-coupling induced enhancement of the spontaneous emission rate of CdS/CdSe quantum emitters. Physica E: Low-dimensional Systems and Nanostructures, 136 , pp. 115017, 2022, ISSN: 1386-9477. (Type: Journal Article | Abstract | Links | BibTeX) @article{GOKBULUT2022115017, title = {Hybrid photonic-plasmonic mode-coupling induced enhancement of the spontaneous emission rate of CdS/CdSe quantum emitters}, author = {Belkıs Gökbulut and Arda Inanç and Gokhan Topcu and Serdar Ozcelik and Mustafa M Demir and Naci M Inci}, url = {https://www.sciencedirect.com/science/article/pii/S1386947721003799}, doi = {https://doi.org/10.1016/j.physe.2021.115017}, issn = {1386-9477}, year = {2022}, date = {2022-01-01}, journal = {Physica E: Low-dimensional Systems and Nanostructures}, volume = {136}, pages = {115017}, abstract = {In this paper, a hybrid photonic-plasmonic resonator, which comprises an electrospun polymer fiber with a micrometer diameter and a core/shell nanostructure with a gold nanoparticle core, is constructed to investigate the dynamics of the coupled spontaneous emission of CdS/CdSe quantum dots (QDs). The gold nanoparticle core; covered with a silica shell, anchored with individual CdS/CdSe QDs, is placed inside a hollow cylindrical nanocavity formed on the surface of the microfiber to enable integration of the optical mode with the plasmonic effect, which is induced by the localized surface plasmons of the metal nanoparticle being present in the vicinity of the dipoles. The spontaneous emission rate of the QDs, coupled into the hybrid photonic-plasmonic mode, is measured to enhance by a factor of 23 via a time-resolved experimental technique. This result suggests that the regeneration of the optical mode-field inside the photonic-plasmonic resonator through the interaction of the dipoles with the localized surface plasmons of a metal nanoparticle strongly enhances the density of the electromagnetic states of the quantum emitters to facilitate an enhanced spontaneous emission within the host medium of the proposed polymer based-photonic structure.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, a hybrid photonic-plasmonic resonator, which comprises an electrospun polymer fiber with a micrometer diameter and a core/shell nanostructure with a gold nanoparticle core, is constructed to investigate the dynamics of the coupled spontaneous emission of CdS/CdSe quantum dots (QDs). The gold nanoparticle core; covered with a silica shell, anchored with individual CdS/CdSe QDs, is placed inside a hollow cylindrical nanocavity formed on the surface of the microfiber to enable integration of the optical mode with the plasmonic effect, which is induced by the localized surface plasmons of the metal nanoparticle being present in the vicinity of the dipoles. The spontaneous emission rate of the QDs, coupled into the hybrid photonic-plasmonic mode, is measured to enhance by a factor of 23 via a time-resolved experimental technique. This result suggests that the regeneration of the optical mode-field inside the photonic-plasmonic resonator through the interaction of the dipoles with the localized surface plasmons of a metal nanoparticle strongly enhances the density of the electromagnetic states of the quantum emitters to facilitate an enhanced spontaneous emission within the host medium of the proposed polymer based-photonic structure. |
Yuce, Hurriyet; Perini, Carlo A R; Hidalgo, Juanita; Castro-Méndez, Andrés-Felipe; Evans, Caria; Betancur, Pablo Franco; Vagott, Jacob N; An, Yu; Bairley, Kathryn; Demir, Mustafa M; Correa-Baena, Juan-Pablo: Understanding the impact of SrI2 additive on the properties of Sn-based halide perovskites. Optical Materials, 123 , pp. 111806, 2022, ISSN: 0925-3467. (Type: Journal Article | Abstract | Links | BibTeX) @article{YUCE2022111806, title = {Understanding the impact of SrI2 additive on the properties of Sn-based halide perovskites}, author = {Hurriyet Yuce and Carlo A R Perini and Juanita Hidalgo and Andrés-Felipe Castro-Méndez and Caria Evans and Pablo Franco Betancur and Jacob N Vagott and Yu An and Kathryn Bairley and Mustafa M Demir and Juan-Pablo Correa-Baena}, url = {https://www.sciencedirect.com/science/article/pii/S0925346721010065}, doi = {https://doi.org/10.1016/j.optmat.2021.111806}, issn = {0925-3467}, year = {2022}, date = {2022-01-01}, journal = {Optical Materials}, volume = {123}, pages = {111806}, abstract = {Organic-inorganic halide perovskites have been identified as favorable candidates for the next generation of photovoltaics. Adding alkali metal halides to perovskite films has been shown to be a viable option to improve the perovskite film quality and to modulate their fundamental properties. In this work, we perform optical and electron-beam based characterizations of mixed Sn/Pb based perovskite films to investigate the effect of the addition of the alkaline metal halide SrI2. By analyzing structural (X-ray diffraction), morphological (Scanning Electron Microscopy), optical (photoluminescence), and chemical properties (X-ray photoelectron spectroscopy), we show a complex interplay of effects upon addition of Sr2+ into the perovskite solution. Low concentrations of Sr2+ increases lattice strain, which hints at incorporation of the additive into the perovskite lattice and improves the film optoelectronic properties. As the additive concentration increases beyond 0.5 mol %, microstrain decreases. At concentrations >0.5 mol %, Sr2+ induces significant reduction of the average domain size, which impacts both structural and optical properties of the perovskite film.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Organic-inorganic halide perovskites have been identified as favorable candidates for the next generation of photovoltaics. Adding alkali metal halides to perovskite films has been shown to be a viable option to improve the perovskite film quality and to modulate their fundamental properties. In this work, we perform optical and electron-beam based characterizations of mixed Sn/Pb based perovskite films to investigate the effect of the addition of the alkaline metal halide SrI2. By analyzing structural (X-ray diffraction), morphological (Scanning Electron Microscopy), optical (photoluminescence), and chemical properties (X-ray photoelectron spectroscopy), we show a complex interplay of effects upon addition of Sr2+ into the perovskite solution. Low concentrations of Sr2+ increases lattice strain, which hints at incorporation of the additive into the perovskite lattice and improves the film optoelectronic properties. As the additive concentration increases beyond 0.5 mol %, microstrain decreases. At concentrations >0.5 mol %, Sr2+ induces significant reduction of the average domain size, which impacts both structural and optical properties of the perovskite film. |
Demir, Eralp; Sas, Hatice S; Isik, Murat; Gungor, Eda Aydogan; Davut, Kemal: A numerical methodology for monitoring stress distributions and experimental proof of the concept on metal embedded thin polymer-matrix composites using X-ray Diffraction. Thin-Walled Structures, 173 , pp. 108942, 2022, ISSN: 0263-8231. (Type: Journal Article | Abstract | Links | BibTeX) @article{DEMIR2022108942, title = {A numerical methodology for monitoring stress distributions and experimental proof of the concept on metal embedded thin polymer-matrix composites using X-ray Diffraction}, author = {Eralp Demir and Hatice S Sas and Murat Isik and Eda Aydogan Gungor and Kemal Davut}, url = {https://www.sciencedirect.com/science/article/pii/S0263823122000349}, doi = {https://doi.org/10.1016/j.tws.2022.108942}, issn = {0263-8231}, year = {2022}, date = {2022-01-01}, journal = {Thin-Walled Structures}, volume = {173}, pages = {108942}, abstract = {In this study, a numerical methodology is developed to monitor stress distributions and an experimental technique is investigated to measure stresses on metal embedded polymer matrix fiber-reinforced composite materials using X-ray diffraction (XRD) method. The numerical method successfully predicts the stress distributions using only a few data points with an average accuracies of 11.6% and 11.8%, respectively for tapered and open hole tensile sample geometries. Experimental part of this study investigates different methodologies to measure stresses on surfaces of polymer composites materials of thin walled structures by XRD. For this reason, metallic materials were integrated onto the surface and near-surface of polymer matrix composites in three different configurations as in the forms of metal foil, metal powder, and metal wire mesh. In-situ experiments of measured and applied stresses revealed metal powder embedded composite materials as a promising material configuration for reliable monitoring of stresses.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, a numerical methodology is developed to monitor stress distributions and an experimental technique is investigated to measure stresses on metal embedded polymer matrix fiber-reinforced composite materials using X-ray diffraction (XRD) method. The numerical method successfully predicts the stress distributions using only a few data points with an average accuracies of 11.6% and 11.8%, respectively for tapered and open hole tensile sample geometries. Experimental part of this study investigates different methodologies to measure stresses on surfaces of polymer composites materials of thin walled structures by XRD. For this reason, metallic materials were integrated onto the surface and near-surface of polymer matrix composites in three different configurations as in the forms of metal foil, metal powder, and metal wire mesh. In-situ experiments of measured and applied stresses revealed metal powder embedded composite materials as a promising material configuration for reliable monitoring of stresses. |
Ozer, Seren; Bilgin, Güney Mert; Davut, Kemal; Esen, Ziya; Dericioglu, Arcan F: Effect of post fabrication aging treatment on the microstructure, crystallographic texture and elevated temperature mechanical properties of IN718 alloy fabricated by selective laser melting. Journal of Materials Processing Technology, 306 , pp. 117622, 2022, ISSN: 0924-0136. (Type: Journal Article | Abstract | Links | BibTeX) @article{OZER2022117622, title = {Effect of post fabrication aging treatment on the microstructure, crystallographic texture and elevated temperature mechanical properties of IN718 alloy fabricated by selective laser melting}, author = {Seren Ozer and Güney Mert Bilgin and Kemal Davut and Ziya Esen and Arcan F Dericioglu}, url = {https://www.sciencedirect.com/science/article/pii/S0924013622001340}, doi = {https://doi.org/10.1016/j.jmatprotec.2022.117622}, issn = {0924-0136}, year = {2022}, date = {2022-01-01}, journal = {Journal of Materials Processing Technology}, volume = {306}, pages = {117622}, abstract = {The effect of building direction and post fabrication aging treatment on the microstructure, crystallographic texture and high temperature mechanical properties of Inconel 718 (IN718) alloy fabricated by selective laser melting (SLM) method was investigated. After aging, arc-shaped structures seen in as-fabricated samples disappeared and converted into a mixture of columnar and equiaxed grains. Nano-sized γ″ and/or γ′ precipitates were formed upon aging; however, MC type carbides and Laves phase encountered in as-fabricated samples were not dissolved completely after aging. Moreover, aging did not alter the texture ((001)//building direction (BD)) of as-fabricated samples. Mechanical properties of the alloys under tension were influenced by the build direction, aging time and test temperature. As-fabricated samples produced in vertical direction exhibited higher room temperature strengths with lower ductility due to orientation of overlapped prior melt pools. Room temperature tensile test results revealed that peak aging caused a significant improvement in ultimate tensile strength (UTS), from 1066.5 MPa and 998.4 MPa to 1408.5 MPa and 1330.4 MPa whereas elongation values decreased from 27.5% and 32.2% to 19.6% and 23.7% in vertically and horizontally built samples, respectively. Peak-aged samples (aged at 700 °C for 8 h) tested at 600 °C displayed serrated regions in their stress-strain curves due to dynamic strain aging (DSA). Although strength values of the samples displayed an expected decrease by temperature, ductility of the samples reduced to minimum at temperatures around 700–800 °C, which was attributed to intermediate temperature embrittlement.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of building direction and post fabrication aging treatment on the microstructure, crystallographic texture and high temperature mechanical properties of Inconel 718 (IN718) alloy fabricated by selective laser melting (SLM) method was investigated. After aging, arc-shaped structures seen in as-fabricated samples disappeared and converted into a mixture of columnar and equiaxed grains. Nano-sized γ″ and/or γ′ precipitates were formed upon aging; however, MC type carbides and Laves phase encountered in as-fabricated samples were not dissolved completely after aging. Moreover, aging did not alter the texture ((001)//building direction (BD)) of as-fabricated samples. Mechanical properties of the alloys under tension were influenced by the build direction, aging time and test temperature. As-fabricated samples produced in vertical direction exhibited higher room temperature strengths with lower ductility due to orientation of overlapped prior melt pools. Room temperature tensile test results revealed that peak aging caused a significant improvement in ultimate tensile strength (UTS), from 1066.5 MPa and 998.4 MPa to 1408.5 MPa and 1330.4 MPa whereas elongation values decreased from 27.5% and 32.2% to 19.6% and 23.7% in vertically and horizontally built samples, respectively. Peak-aged samples (aged at 700 °C for 8 h) tested at 600 °C displayed serrated regions in their stress-strain curves due to dynamic strain aging (DSA). Although strength values of the samples displayed an expected decrease by temperature, ductility of the samples reduced to minimum at temperatures around 700–800 °C, which was attributed to intermediate temperature embrittlement. |
2021 |
Sargın, Koray Sevim Burak Özdamar Gizem Kurt Mustafa Neşet Çınar Gözde Özbal; Sevinçli, Hâldun: Ballistic thermoelectric transport properties of two-dimensional group III-VI monolayers. Phys. Rev. B, 103 , pp. 165422, 2021. (Type: Journal Article | Links | BibTeX) @article{PhysRevB.103.165422, title = {Ballistic thermoelectric transport properties of two-dimensional group III-VI monolayers}, author = {Koray Sevim Burak Özdamar Gizem Kurt Mustafa Neşet Çınar Gözde Özbal Sargın and Hâldun Sevinçli}, url = {https://link.aps.org/doi/10.1103/PhysRevB.103.165422}, doi = {10.1103/PhysRevB.103.165422}, year = {2021}, date = {2021-04-01}, journal = {Phys. Rev. B}, volume = {103}, pages = {165422}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Karakaya, Merve; Adem, Umut: Enhanced room temperature energy storage density of Bi(Li1/3Ti2/3)O3 substituted Bi0.5Na0.5TiO3–BaTiO3 ceramics. Journal of Physics D: Applied Physics, 54 (27), pp. 275501, 2021. (Type: Journal Article | Abstract | Links | BibTeX) @article{Karakaya_2021, title = {Enhanced room temperature energy storage density of Bi(Li1/3Ti2/3)O3 substituted Bi0.5Na0.5TiO3–BaTiO3 ceramics}, author = {Merve Karakaya and Umut Adem}, url = {https://doi.org/10.1088/1361-6463/abf789}, doi = {10.1088/1361-6463/abf789}, year = {2021}, date = {2021-04-01}, journal = {Journal of Physics D: Applied Physics}, volume = {54}, number = {27}, pages = {275501}, publisher = {IOP Publishing}, abstract = {For high power electronics applications, relaxor ferroelectrics are promising materials due to their superior energy storage properties. In this study, we investigate the energy storage properties of novel lead free relaxor ferroelectric ceramics (1−x)(0.92Bi0.5Na0.5TiO3–0.08BaTiO3)–xBi(Li1/3Ti2/3)O3 (abbreviated as BNT–8BT–xBLT). BNT–8BT composition which is close to morphotropic phase boundary was chosen as the base due to its large maximum polarization (P m) and higher ratio of weakly polar tetragonal phase which is expected to facilitate ergodic relaxor behavior and improve energy storage density. The substitution of BLT to the BNT–8BT strongly disrupts the correlations between the polar nanoregions and the transition from nonergodic to ergodic relaxor state occurs already at x = 0.02 BLT at room temperature. Largest energy density (W rec) at 61 kV cm−1 was obtained for x = 0.02 sample (0.656 J cm−3), followed by x = 0.03 (W rec = 0.614 J cm−3) and x = 0.05 (W rec= 0.559 J cm−3). The x = 0.02 sample keeps its energy storage density at high temperatures (i.e. W rec= 0.88 J cm−3, η = 97%, E m= 65 kV cm−1 at 125 °C), while larger electric field (up to 89 kV cm−1) could be applied to the x = 0.05 sample with the smallest grain size and energy density of 1.03 J cm−3 was reached at room temperature. Energy storage density values of BLT substituted materials normalized per unit applied electric field are promising among BNT-based materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } For high power electronics applications, relaxor ferroelectrics are promising materials due to their superior energy storage properties. In this study, we investigate the energy storage properties of novel lead free relaxor ferroelectric ceramics (1−x)(0.92Bi0.5Na0.5TiO3–0.08BaTiO3)–xBi(Li1/3Ti2/3)O3 (abbreviated as BNT–8BT–xBLT). BNT–8BT composition which is close to morphotropic phase boundary was chosen as the base due to its large maximum polarization (P m) and higher ratio of weakly polar tetragonal phase which is expected to facilitate ergodic relaxor behavior and improve energy storage density. The substitution of BLT to the BNT–8BT strongly disrupts the correlations between the polar nanoregions and the transition from nonergodic to ergodic relaxor state occurs already at x = 0.02 BLT at room temperature. Largest energy density (W rec) at 61 kV cm−1 was obtained for x = 0.02 sample (0.656 J cm−3), followed by x = 0.03 (W rec = 0.614 J cm−3) and x = 0.05 (W rec= 0.559 J cm−3). The x = 0.02 sample keeps its energy storage density at high temperatures (i.e. W rec= 0.88 J cm−3, η = 97%, E m= 65 kV cm−1 at 125 °C), while larger electric field (up to 89 kV cm−1) could be applied to the x = 0.05 sample with the smallest grain size and energy density of 1.03 J cm−3 was reached at room temperature. Energy storage density values of BLT substituted materials normalized per unit applied electric field are promising among BNT-based materials. |
Calcabrini, Mariano; ç, Aziz Gen; Liu, Yu; Kleinhanns, Tobias; Lee, Seungho; Dirin, Dmitry N; Akkerman, Quinten A; Kovalenko, Maksym V; Arbiol, Jordi; ñ, Maria Ibá: Exploiting the Lability of Metal Halide Perovskites for Doping Semiconductor Nanocomposites. ACS Energy Letters, 6 (2), pp. 581-587, 2021. (Type: Journal Article | Links | BibTeX) @article{Calcabrini2021, title = {Exploiting the Lability of Metal Halide Perovskites for Doping Semiconductor Nanocomposites}, author = {Mariano Calcabrini and Aziz Gen{ç} and Yu Liu and Tobias Kleinhanns and Seungho Lee and Dmitry N Dirin and Quinten A Akkerman and Maksym V Kovalenko and Jordi Arbiol and Maria Ibá{ñ}ez}, url = {https://doi.org/10.1021/acsenergylett.0c02448}, doi = {10.1021/acsenergylett.0c02448}, year = {2021}, date = {2021-02-12}, journal = {ACS Energy Letters}, volume = {6}, number = {2}, pages = {581-587}, publisher = {American Chemical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Gören, Yağmur A; Topcu, Gokhan; Demir, Mustafa M; Baba, Alper: Effect of high salinity and temperature on water--volcanic rock interaction. Environmental Earth Sciences, 80 (3), pp. 74, 2021, ISSN: 1866-6299. (Type: Journal Article | Abstract | Links | BibTeX) @article{Gören2021, title = {Effect of high salinity and temperature on water--volcanic rock interaction}, author = {Yağmur A Gören and Gokhan Topcu and Mustafa M Demir and Alper Baba}, url = {https://doi.org/10.1007/s12665-020-09352-1}, doi = {10.1007/s12665-020-09352-1}, issn = {1866-6299}, year = {2021}, date = {2021-01-17}, journal = {Environmental Earth Sciences}, volume = {80}, number = {3}, pages = {74}, abstract = {In order to understand the processes occurring in natural hydrothermal systems, it was carried out a series of water--volcanic rock interaction studies in the laboratory and an intermediate volcanic rock samples from geothermal production wells in Tuzla geothermal field (TGF) in western Turkey. A high-pressure autoclave was used to conduct water--rock interaction experiments under similar conditions of the field. Rainwater and seawater were treated with volcanic rocks at 140 textdegreeC (reservoir temperature) and 4.5 bar pressure. The change in the ionic content of the resulting fluids was examined in terms of the type of volcanic rocks and mineral saturation index. The results indicate that talc and diopside minerals in geothermal systems may cause scaling at high temperatures depending on the geothermal fluid and pH.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In order to understand the processes occurring in natural hydrothermal systems, it was carried out a series of water--volcanic rock interaction studies in the laboratory and an intermediate volcanic rock samples from geothermal production wells in Tuzla geothermal field (TGF) in western Turkey. A high-pressure autoclave was used to conduct water--rock interaction experiments under similar conditions of the field. Rainwater and seawater were treated with volcanic rocks at 140 textdegreeC (reservoir temperature) and 4.5 bar pressure. The change in the ionic content of the resulting fluids was examined in terms of the type of volcanic rocks and mineral saturation index. The results indicate that talc and diopside minerals in geothermal systems may cause scaling at high temperatures depending on the geothermal fluid and pH. |
Arica, Tugce A; Guzelgulgen, Meltem; Yildiz, Ahu Arslan; Demir, Mustafa M: Electrospun GelMA fibers and p(HEMA) matrix composite for corneal tissue engineering. Materials Science and Engineering: C, 120 , pp. 111720, 2021, ISSN: 0928-4931. (Type: Journal Article | Abstract | Links | BibTeX) @article{ARICA2021111720, title = {Electrospun GelMA fibers and p(HEMA) matrix composite for corneal tissue engineering}, author = {Tugce A Arica and Meltem Guzelgulgen and Ahu Arslan Yildiz and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S0928493120336390}, doi = {https://doi.org/10.1016/j.msec.2020.111720}, issn = {0928-4931}, year = {2021}, date = {2021-01-01}, journal = {Materials Science and Engineering: C}, volume = {120}, pages = {111720}, abstract = {The development of biocompatible and transparent three-dimensional materials is desirable for corneal tissue engineering. Inspired from the cornea structure, gelatin methacryloyl-poly(2-hydroxymethyl methacrylate) (GelMA-p(HEMA)) composite hydrogel was fabricated. GelMA fibers were produced via electrospinning and covered with a thin layer of p(HEMA) in the presence of N,N′-methylenebisacrylamide (MBA) as cross-linker by drop-casting. The structure of resulting GelMA-p(HEMA) composite was characterized by spectrophotometry, microscopy, and swelling studies. Biocompatibility and biological properties of the both p(HEMA) and GelMA-p(HEMA) composite have been investigated by 3D cell culture, red blood cell hemolysis, and protein adsorption studies (i.e., human serum albumin, human immunoglobulin and egg white lysozyme). The optical transmittance of the GelMA-p(HEMA) composite was found to be approximately 70% at 550 nm. The GelMA-p(HEMA) composite was biocompatible with tear fluid proteins and convenient for cell adhesion and growth. Thus, as prepared hydrogel composite may find extensive applications in future for the development of corneal tissue engineering as well as preparation of stroma of the corneal material.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The development of biocompatible and transparent three-dimensional materials is desirable for corneal tissue engineering. Inspired from the cornea structure, gelatin methacryloyl-poly(2-hydroxymethyl methacrylate) (GelMA-p(HEMA)) composite hydrogel was fabricated. GelMA fibers were produced via electrospinning and covered with a thin layer of p(HEMA) in the presence of N,N′-methylenebisacrylamide (MBA) as cross-linker by drop-casting. The structure of resulting GelMA-p(HEMA) composite was characterized by spectrophotometry, microscopy, and swelling studies. Biocompatibility and biological properties of the both p(HEMA) and GelMA-p(HEMA) composite have been investigated by 3D cell culture, red blood cell hemolysis, and protein adsorption studies (i.e., human serum albumin, human immunoglobulin and egg white lysozyme). The optical transmittance of the GelMA-p(HEMA) composite was found to be approximately 70% at 550 nm. The GelMA-p(HEMA) composite was biocompatible with tear fluid proteins and convenient for cell adhesion and growth. Thus, as prepared hydrogel composite may find extensive applications in future for the development of corneal tissue engineering as well as preparation of stroma of the corneal material. |
Costa, A I; Viana, F; Toptan, F; Geringer, J: Highly porous Ti as a bone substitute: Triboelectrochemical characterization of highly porous Ti against Ti alloy under fretting-corrosion conditions. Corrosion Science, 190 , pp. 109696, 2021, ISSN: 0010-938X. (Type: Journal Article | Abstract | Links | BibTeX) @article{COSTA2021109696, title = {Highly porous Ti as a bone substitute: Triboelectrochemical characterization of highly porous Ti against Ti alloy under fretting-corrosion conditions}, author = {A I Costa and F Viana and F Toptan and J Geringer}, url = {https://www.sciencedirect.com/science/article/pii/S0010938X21004625}, doi = {https://doi.org/10.1016/j.corsci.2021.109696}, issn = {0010-938X}, year = {2021}, date = {2021-01-01}, journal = {Corrosion Science}, volume = {190}, pages = {109696}, abstract = {Highly porous Ti was investigated under fretting-corrosion conditions as a function of load and amplitude. To obtain a correlation between mechanical and electrochemical responses according to amplitude, a new representative master curve was suggested: the A ratio (dissipated energy over total energy) vs. 1st OCP drop that fitted well the fretting-corrosion behaviour. Fretting-corrosion mechanisms were presented and a fretting map was illustrated. There was a significant load- and amplitude-dependent response, showing gross slip and partial slip regimes can occur with expected OCP variations. The promising structure of highly porous Ti was preserved after 16 h of fretting-corrosion under severe solicitations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Highly porous Ti was investigated under fretting-corrosion conditions as a function of load and amplitude. To obtain a correlation between mechanical and electrochemical responses according to amplitude, a new representative master curve was suggested: the A ratio (dissipated energy over total energy) vs. 1st OCP drop that fitted well the fretting-corrosion behaviour. Fretting-corrosion mechanisms were presented and a fretting map was illustrated. There was a significant load- and amplitude-dependent response, showing gross slip and partial slip regimes can occur with expected OCP variations. The promising structure of highly porous Ti was preserved after 16 h of fretting-corrosion under severe solicitations. |
Çaha, Ihsan; Alves, Alexandra C; Chirico, Caterina; Pinto, Ana Maria; Tsipas, Sophia; Gordo, Elena; Toptan, Fatih: Improved tribocorrosion behavior on bio-functionalized β-type titanium alloy by the pillar effect given by TiN reinforcements. Surface and Coatings Technology, 415 , pp. 127122, 2021, ISSN: 0257-8972. (Type: Journal Article | Abstract | Links | BibTeX) @article{CAHA2021127122, title = {Improved tribocorrosion behavior on bio-functionalized β-type titanium alloy by the pillar effect given by TiN reinforcements}, author = {Ihsan Çaha and Alexandra C Alves and Caterina Chirico and Ana Maria Pinto and Sophia Tsipas and Elena Gordo and Fatih Toptan}, url = {https://www.sciencedirect.com/science/article/pii/S0257897221002966}, doi = {https://doi.org/10.1016/j.surfcoat.2021.127122}, issn = {0257-8972}, year = {2021}, date = {2021-01-01}, journal = {Surface and Coatings Technology}, volume = {415}, pages = {127122}, abstract = {A novel multi-functional material was developed by hard TiN particle reinforcement addition to a β-type Ti alloy, following by bio-functionalization of its surface through Ca and P rich oxide layer. Corrosion and tribocorrosion behavior of this multi-functional material was investigated in phosphate buffer solution at body temperature. Bio-functionalization drastically improved the corrosion and tribocorrosion behavior of the unreinforced and reinforced samples, where the bio-functionalized β-type titanium alloy matrix composite presented the best tribocorrosion behavior due to the load-carrying role of the hard reinforcement phase that gave a support to the functionalized surface layer.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A novel multi-functional material was developed by hard TiN particle reinforcement addition to a β-type Ti alloy, following by bio-functionalization of its surface through Ca and P rich oxide layer. Corrosion and tribocorrosion behavior of this multi-functional material was investigated in phosphate buffer solution at body temperature. Bio-functionalization drastically improved the corrosion and tribocorrosion behavior of the unreinforced and reinforced samples, where the bio-functionalized β-type titanium alloy matrix composite presented the best tribocorrosion behavior due to the load-carrying role of the hard reinforcement phase that gave a support to the functionalized surface layer. |
Icin, Oyku; Vakifahmetoglu, Cekdar: Dye removal by polymer derived ceramic nanobeads. Ceramics International, 47 (19), pp. 27050-27057, 2021, ISSN: 0272-8842. (Type: Journal Article | Abstract | Links | BibTeX) @article{ICIN202127050, title = {Dye removal by polymer derived ceramic nanobeads}, author = {Oyku Icin and Cekdar Vakifahmetoglu}, url = {https://www.sciencedirect.com/science/article/pii/S0272884221018630}, doi = {https://doi.org/10.1016/j.ceramint.2021.06.118}, issn = {0272-8842}, year = {2021}, date = {2021-01-01}, journal = {Ceramics International}, volume = {47}, number = {19}, pages = {27050-27057}, abstract = {Emulsion processed polymer derived ceramic (PDC) nanobeads are used for Methylene Blue dye removal from aqueous solutions. The PDC nanobeads, produced at 600 °C and 1200 °C pyrolysis, are subsequently coated with titania (anatase). Titania-coated nanobeads show less than 35%, i.e., limited dye adsorption capability in dark. Instead, enhanced total removal efficiency (∼97%) is obtained when the initial adsorption is succeeded by photodegradation under UV. Direct reusability tests show that even after the third cycle, very high regeneration efficiencies being above 92% are observed for titania-coated nanobeads.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Emulsion processed polymer derived ceramic (PDC) nanobeads are used for Methylene Blue dye removal from aqueous solutions. The PDC nanobeads, produced at 600 °C and 1200 °C pyrolysis, are subsequently coated with titania (anatase). Titania-coated nanobeads show less than 35%, i.e., limited dye adsorption capability in dark. Instead, enhanced total removal efficiency (∼97%) is obtained when the initial adsorption is succeeded by photodegradation under UV. Direct reusability tests show that even after the third cycle, very high regeneration efficiencies being above 92% are observed for titania-coated nanobeads. |
Sousa, L; Basilio, L; Alves, A C; Toptan, F: Tribocorrosion-resistant biofunctionalized Ti-Al2O3 composites. Surface and Coatings Technology, 420 , pp. 127329, 2021, ISSN: 0257-8972. (Type: Journal Article | Abstract | Links | BibTeX) @article{SOUSA2021127329, title = {Tribocorrosion-resistant biofunctionalized Ti-Al2O3 composites}, author = {L Sousa and L Basilio and A C Alves and F Toptan}, url = {https://www.sciencedirect.com/science/article/pii/S025789722100503X}, doi = {https://doi.org/10.1016/j.surfcoat.2021.127329}, issn = {0257-8972}, year = {2021}, date = {2021-01-01}, journal = {Surface and Coatings Technology}, volume = {420}, pages = {127329}, abstract = {Recent studies have shown that titanium matrix composites have potential for load-bearing biomedical implants due to their improved tribocorrosion behaviour compared to Ti and its alloys. However, lack of bioactivity remains as a concern due to bioinert Ti matrix and the fact that most reinforcement phases are also bioinert. In this work, biofunctionalized Ti-Al2O3 composites were produced by performing micro-arc oxidation treatment on the Ti-Al2O3 composites processed by hot-pressing technique. The overall microstructure consisted of Al2O3 particles dispersed within a biofunctionalized Ti matrix having a micro-porous structure rich in Ca and P elements. The corrosion behaviour of the composites was greatly improved after MAO treatment, whereas the tribocorrosion behaviour of the composites was also further improved after MAO treatment.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent studies have shown that titanium matrix composites have potential for load-bearing biomedical implants due to their improved tribocorrosion behaviour compared to Ti and its alloys. However, lack of bioactivity remains as a concern due to bioinert Ti matrix and the fact that most reinforcement phases are also bioinert. In this work, biofunctionalized Ti-Al2O3 composites were produced by performing micro-arc oxidation treatment on the Ti-Al2O3 composites processed by hot-pressing technique. The overall microstructure consisted of Al2O3 particles dispersed within a biofunctionalized Ti matrix having a micro-porous structure rich in Ca and P elements. The corrosion behaviour of the composites was greatly improved after MAO treatment, whereas the tribocorrosion behaviour of the composites was also further improved after MAO treatment. |
Aouadja, Fayçal; Bouzerara, Ferhat; Guvenc, Cetin Meric; Demir, Mustafa M: Fabrication and properties of novel porous ceramic membrane supports from the (Sig) diatomite and alumina mixtures. Boletín de la Sociedad Española de Cerámica y Vidrio, 2021, ISSN: 0366-3175. (Type: Journal Article | Abstract | Links | BibTeX) @article{AOUADJA2021, title = {Fabrication and properties of novel porous ceramic membrane supports from the (Sig) diatomite and alumina mixtures}, author = {Fayçal Aouadja and Ferhat Bouzerara and Cetin Meric Guvenc and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S0366317521000339}, doi = {https://doi.org/10.1016/j.bsecv.2021.04.002}, issn = {0366-3175}, year = {2021}, date = {2021-01-01}, journal = {Boletín de la Sociedad Española de Cerámica y Vidrio}, abstract = {In this paper, the manufacturing of macro-porous tubular ceramic supports for membranes is described. The novel supports are fabricated from natural diatomite and alumina raw materials using the extrusion method. The structure was analyzed by X-ray diffraction (XRD) and mercury porosimetry techniques; the presence of possible defects was investigated by scanning electron microscopy (SEM). The permeability has been measured from water flux in standard experiments. Experimental results show that the open porosity, the average pore size (APS), the pore size distribution, the strength, and the permeability of sintered supports, have been found to depend, mainly on the concentration of alumina (Al2O3) additive. Supports prepared with the addition of 10wt.% of alumina and sintered at 1200°C, can be considered as the most optimized; they have a porosity ratio of about 46%, an APS is around 7.7μm, a flexural strength value of about 28MPa, and water permeability of around 15m3h−1m−2bar−1. Such materials could be of great interest in the supports fabrication for membrane application, for instance, water filtration. Resumen En este trabajo se describe la fabricación de soportes cerámicos tubulares macroporosos para membranas. Los nuevos soportes se fabrican a partir de materias primas de diatomita natural y alúmina mediante el método de extrusión. La estructura se analizó por medio de técnicas de difracción de rayos X (XRD) y porosimetría de mercurio; la presencia de posibles defectos se investigó mediante microscopía electrónica de barrido (SEM). La permeabilidad se ha medido a partir del flujo de agua en experimentos estándar. Los resultados experimentales muestran que se ha encontrado que la porosidad abierta, el tamaño medio de poro (APS), la distribución del tamaño de poro, la resistencia y la permeabilidad de los soportes sinterizados dependen, principalmente, de la concentración de aditivo de alúmina (Al2O3). Los soportes preparados con la adición de 10% en peso de alúmina y sinterizados a 1.200°C, pueden considerarse como los más optimizados; tienen una relación de porosidad de alrededor del 46%, un APS es de alrededor de 7,7 μm, un valor de resistencia a la flexión de alrededor de 28 MPa y una permeabilidad al agua de alrededor de 15 m3.h-1.m-2. bar-1. Dichos materiales podrían ser de gran interés en la fabricación de soportes para la aplicación de membranas, por ejemplo, filtración de agua.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, the manufacturing of macro-porous tubular ceramic supports for membranes is described. The novel supports are fabricated from natural diatomite and alumina raw materials using the extrusion method. The structure was analyzed by X-ray diffraction (XRD) and mercury porosimetry techniques; the presence of possible defects was investigated by scanning electron microscopy (SEM). The permeability has been measured from water flux in standard experiments. Experimental results show that the open porosity, the average pore size (APS), the pore size distribution, the strength, and the permeability of sintered supports, have been found to depend, mainly on the concentration of alumina (Al2O3) additive. Supports prepared with the addition of 10wt.% of alumina and sintered at 1200°C, can be considered as the most optimized; they have a porosity ratio of about 46%, an APS is around 7.7μm, a flexural strength value of about 28MPa, and water permeability of around 15m3h−1m−2bar−1. Such materials could be of great interest in the supports fabrication for membrane application, for instance, water filtration. Resumen En este trabajo se describe la fabricación de soportes cerámicos tubulares macroporosos para membranas. Los nuevos soportes se fabrican a partir de materias primas de diatomita natural y alúmina mediante el método de extrusión. La estructura se analizó por medio de técnicas de difracción de rayos X (XRD) y porosimetría de mercurio; la presencia de posibles defectos se investigó mediante microscopía electrónica de barrido (SEM). La permeabilidad se ha medido a partir del flujo de agua en experimentos estándar. Los resultados experimentales muestran que se ha encontrado que la porosidad abierta, el tamaño medio de poro (APS), la distribución del tamaño de poro, la resistencia y la permeabilidad de los soportes sinterizados dependen, principalmente, de la concentración de aditivo de alúmina (Al2O3). Los soportes preparados con la adición de 10% en peso de alúmina y sinterizados a 1.200°C, pueden considerarse como los más optimizados; tienen una relación de porosidad de alrededor del 46%, un APS es de alrededor de 7,7 μm, un valor de resistencia a la flexión de alrededor de 28 MPa y una permeabilidad al agua de alrededor de 15 m3.h-1.m-2. bar-1. Dichos materiales podrían ser de gran interés en la fabricación de soportes para la aplicación de membranas, por ejemplo, filtración de agua. |
Piskin, Cerem; Karacasulu, Levent; Bortolotti, Mauro; Vakifahmetoglu, Cekdar: Synthesis of potassium–sodium niobate (KNN) from NbO2. Open Ceramics, 7 , pp. 100159, 2021, ISSN: 2666-5395. (Type: Journal Article | Abstract | Links | BibTeX) @article{PISKIN2021100159, title = {Synthesis of potassium–sodium niobate (KNN) from NbO2}, author = {Cerem Piskin and Levent Karacasulu and Mauro Bortolotti and Cekdar Vakifahmetoglu}, url = {https://www.sciencedirect.com/science/article/pii/S266653952100105X}, doi = {https://doi.org/10.1016/j.oceram.2021.100159}, issn = {2666-5395}, year = {2021}, date = {2021-01-01}, journal = {Open Ceramics}, volume = {7}, pages = {100159}, abstract = {KxNa1-xNbO3 (0 < x < 1) were synthesized via hydrothermal method using niobium dioxide (NbO2) as the niobium source instead of the most common one, Nb2O5. Potassium-rich KxNa1-xNbO3 (x > 0.5) was obtained from 8 M total hydroxide concentration after 6 h of reaction at 200 °C. Rietveld refinement of the XRD data revealed that all samples exhibited the secondary NaNbO3 phase. However, the lowest amount (3.74 vol%) was obtained for 24 h of reaction under 10 M alkaline solution. After 3 h of reaction, dodecahedra shaped hexaniobate phase (KxNa8-xNb6O19.nH2O) was observed. Those structures were, subsequently, replaced by ~3 μm cube shaped KNN crystals, obtained under 10 M reaction in 24 h time period.}, keywords = {}, pubstate = {published}, tppubtype = {article} } KxNa1-xNbO3 (0 < x < 1) were synthesized via hydrothermal method using niobium dioxide (NbO2) as the niobium source instead of the most common one, Nb2O5. Potassium-rich KxNa1-xNbO3 (x > 0.5) was obtained from 8 M total hydroxide concentration after 6 h of reaction at 200 °C. Rietveld refinement of the XRD data revealed that all samples exhibited the secondary NaNbO3 phase. However, the lowest amount (3.74 vol%) was obtained for 24 h of reaction under 10 M alkaline solution. After 3 h of reaction, dodecahedra shaped hexaniobate phase (KxNa8-xNb6O19.nH2O) was observed. Those structures were, subsequently, replaced by ~3 μm cube shaped KNN crystals, obtained under 10 M reaction in 24 h time period. |
Arica, Tugce A; Isık, Tugba; Guner, Tugrul; Horzum, Nesrin; Demir, Mustafa M: Advances in Electrospun Fiber-Based Flexible Nanogenerators for Wearable Applications. Macromolecular Materials and Engineering, 306 (8), pp. 2100143, 2021. (Type: Journal Article | Abstract | Links | BibTeX) @article{https://doi.org/10.1002/mame.202100143, title = {Advances in Electrospun Fiber-Based Flexible Nanogenerators for Wearable Applications}, author = {Tugce A Arica and Tugba Isık and Tugrul Guner and Nesrin Horzum and Mustafa M Demir}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/mame.202100143}, doi = {https://doi.org/10.1002/mame.202100143}, year = {2021}, date = {2021-01-01}, journal = {Macromolecular Materials and Engineering}, volume = {306}, number = {8}, pages = {2100143}, abstract = {Abstract In today's digital age, the need and interest in personal and portable electronics shows a dramatic growth trend in daily life parallel to the developments in sensors technologies and the internet. Wearable electronics that can be attached to clothing, accessories, and the human body are one of the most promising subfields. The energy requirement for the devices considering the reduction in device sizes and the necessity of being flexible and light, the existing batteries are insufficient and nanogenerators have been recognized a suitable energy source in the last decade. The mechanical energy created by the daily activities of the human body is an accessible and natural energy source for nanogenerators. Fiber-structured functional materials contribute to the increase in energy efficiency due to their effective surface to volume ratio while providing the necessary compatibility and comfort for the movements in daily life with its flexibility and lightness. Among the potential solutions, electrospinning stands out as a promising technique that can meet these requirements, allowing for simple, versatile, and continuous fabrication. Herein, wearable electronics and their future potential, electrospinning, and its place in energy applications are overviewed. Moreover, piezoelectric, triboelectric, and hybrid nanogenerators fabricated or associated with electrospun fibrous materials are presented.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract In today's digital age, the need and interest in personal and portable electronics shows a dramatic growth trend in daily life parallel to the developments in sensors technologies and the internet. Wearable electronics that can be attached to clothing, accessories, and the human body are one of the most promising subfields. The energy requirement for the devices considering the reduction in device sizes and the necessity of being flexible and light, the existing batteries are insufficient and nanogenerators have been recognized a suitable energy source in the last decade. The mechanical energy created by the daily activities of the human body is an accessible and natural energy source for nanogenerators. Fiber-structured functional materials contribute to the increase in energy efficiency due to their effective surface to volume ratio while providing the necessary compatibility and comfort for the movements in daily life with its flexibility and lightness. Among the potential solutions, electrospinning stands out as a promising technique that can meet these requirements, allowing for simple, versatile, and continuous fabrication. Herein, wearable electronics and their future potential, electrospinning, and its place in energy applications are overviewed. Moreover, piezoelectric, triboelectric, and hybrid nanogenerators fabricated or associated with electrospun fibrous materials are presented. |
Vakifahmetoglu, Cekdar; Semerci, Tugce; Gurlo, Aleksander; Soraru, Gian Domenico: Polymer derived ceramic aerogels. Current Opinion in Solid State and Materials Science, 25 (4), pp. 100936, 2021, ISSN: 1359-0286. (Type: Journal Article | Abstract | Links | BibTeX) @article{VAKIFAHMETOGLU2021100936, title = {Polymer derived ceramic aerogels}, author = {Cekdar Vakifahmetoglu and Tugce Semerci and Aleksander Gurlo and Gian Domenico Soraru}, url = {https://www.sciencedirect.com/science/article/pii/S1359028621000395}, doi = {https://doi.org/10.1016/j.cossms.2021.100936}, issn = {1359-0286}, year = {2021}, date = {2021-01-01}, journal = {Current Opinion in Solid State and Materials Science}, volume = {25}, number = {4}, pages = {100936}, abstract = {Aerogels are unique porous solids having exceptional low relative density together with high specific surface area, making them very attractive materials for scientific research and industrial applications. Polymer derived ceramic aerogels are a new class of materials obtained through the pyrolysis of sol-gel/preceramic polymers. Herein this review, some of the representative formation methods and applications of polymer derived ceramic aerogels are highlighted with a specific focus on the thermal, electrical, and adsorbent related properties.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Aerogels are unique porous solids having exceptional low relative density together with high specific surface area, making them very attractive materials for scientific research and industrial applications. Polymer derived ceramic aerogels are a new class of materials obtained through the pyrolysis of sol-gel/preceramic polymers. Herein this review, some of the representative formation methods and applications of polymer derived ceramic aerogels are highlighted with a specific focus on the thermal, electrical, and adsorbent related properties. |
Karacasulu, Levent; Ogur, Ezgi; Piskin, Cerem; Vakifahmetoglu, Cekdar: Cold sintering of soda-lime glass. Scripta Materialia, 192 , pp. 111-114, 2021, ISSN: 1359-6462. (Type: Journal Article | Abstract | Links | BibTeX) @article{KARACASULU2021111, title = {Cold sintering of soda-lime glass}, author = {Levent Karacasulu and Ezgi Ogur and Cerem Piskin and Cekdar Vakifahmetoglu}, url = {https://www.sciencedirect.com/science/article/pii/S135964622030662X}, doi = {https://doi.org/10.1016/j.scriptamat.2020.10.015}, issn = {1359-6462}, year = {2021}, date = {2021-01-01}, journal = {Scripta Materialia}, volume = {192}, pages = {111-114}, abstract = {Ordinary recycled soda lime glass powder was densified via cold sintering process with the aid of concentrated NaOH solution. Increase in processing time, temperature and concentration of the NaOH solution resulted in the formation of monolithic glass artifacts with higher relative densities. The sample densified the most (95.2%) was obtained when the sintering was performed at 250˚C with a 20 min dwell time using 15 M NaOH solution.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ordinary recycled soda lime glass powder was densified via cold sintering process with the aid of concentrated NaOH solution. Increase in processing time, temperature and concentration of the NaOH solution resulted in the formation of monolithic glass artifacts with higher relative densities. The sample densified the most (95.2%) was obtained when the sintering was performed at 250˚C with a 20 min dwell time using 15 M NaOH solution. |
Tonkul, Serhat; Baba, Alper; Demir, Mustafa M; Regenspurg, Simona: Characterization of Sb scaling and fluids in saline geothermal power plants: A case study for Germencik Region (Büyük Menderes Graben, Turkey). Geothermics, 96 , pp. 102227, 2021, ISSN: 0375-6505. (Type: Journal Article | Abstract | Links | BibTeX) @article{TONKUL2021102227, title = {Characterization of Sb scaling and fluids in saline geothermal power plants: A case study for Germencik Region (Büyük Menderes Graben, Turkey)}, author = {Serhat Tonkul and Alper Baba and Mustafa M Demir and Simona Regenspurg}, url = {https://www.sciencedirect.com/science/article/pii/S037565052100184X}, doi = {https://doi.org/10.1016/j.geothermics.2021.102227}, issn = {0375-6505}, year = {2021}, date = {2021-01-01}, journal = {Geothermics}, volume = {96}, pages = {102227}, abstract = {Turkey is located on the seismically active Alpine-Himalayan belt. Although tectonic activity causes seismicity in the Anatolian plate, it also constitutes an important geothermal energy resource. Today, geothermal energy production is heavily concentrated in Turkey's Western Anatolia region. Graben systems in this region are very suitable for geothermal resources. The Büyük Menderes Graben (BMG) is an area of complex geology with active tectonics and high geothermal potential power. Germencik (Aydın) is located in the BMG, where the geothermal waters include mainly Na-Cl-HCO3 water types. This study examined the stibnite scaling formed in the preheater system of the Germencik Geothermal Field (GGF). The formation of the stibnite scaling on the preheater system dramatically reduces the energy harvesting of the GGF. Considering the stibnite scaling in the surface equipment, the optimum reinjection temperature was determined as 95 °C to prevent stibnite scaling in the GGF.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Turkey is located on the seismically active Alpine-Himalayan belt. Although tectonic activity causes seismicity in the Anatolian plate, it also constitutes an important geothermal energy resource. Today, geothermal energy production is heavily concentrated in Turkey's Western Anatolia region. Graben systems in this region are very suitable for geothermal resources. The Büyük Menderes Graben (BMG) is an area of complex geology with active tectonics and high geothermal potential power. Germencik (Aydın) is located in the BMG, where the geothermal waters include mainly Na-Cl-HCO3 water types. This study examined the stibnite scaling formed in the preheater system of the Germencik Geothermal Field (GGF). The formation of the stibnite scaling on the preheater system dramatically reduces the energy harvesting of the GGF. Considering the stibnite scaling in the surface equipment, the optimum reinjection temperature was determined as 95 °C to prevent stibnite scaling in the GGF. |
Sousa, L; Alves, A C; Guedes, A; Toptan, F: Corrosion and tribocorrosion behaviour of Ti-B4C composites processed by conventional sintering and hot-pressing technique. Journal of Alloys and Compounds, 885 , pp. 161109, 2021, ISSN: 0925-8388. (Type: Journal Article | Abstract | Links | BibTeX) @article{SOUSA2021161109, title = {Corrosion and tribocorrosion behaviour of Ti-B4C composites processed by conventional sintering and hot-pressing technique}, author = {L Sousa and A C Alves and A Guedes and F Toptan}, url = {https://www.sciencedirect.com/science/article/pii/S0925838821025184}, doi = {https://doi.org/10.1016/j.jallcom.2021.161109}, issn = {0925-8388}, year = {2021}, date = {2021-01-01}, journal = {Journal of Alloys and Compounds}, volume = {885}, pages = {161109}, abstract = {In this work, low volume reinforcement ex-situ Ti-B4C composites were produced using two different routes: conventional powder metallurgy (PM) and hot-pressing (HP). The effect of reinforcement phases and processing method on corrosion and tribocorrosion behaviour were studied. Composites processed by PM lost the typical passive behaviour of Ti matrix, while composites processed by HP presented similar behaviour to unreinforced Ti. Tribocorrosion tests showed that both composite groups presented two times decrease in corrosion kinetics under sliding compared to pure titanium. An antagonistic effect between wear and corrosion was observed for composites with at least two times decrease in wear volume compared to titanium.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, low volume reinforcement ex-situ Ti-B4C composites were produced using two different routes: conventional powder metallurgy (PM) and hot-pressing (HP). The effect of reinforcement phases and processing method on corrosion and tribocorrosion behaviour were studied. Composites processed by PM lost the typical passive behaviour of Ti matrix, while composites processed by HP presented similar behaviour to unreinforced Ti. Tribocorrosion tests showed that both composite groups presented two times decrease in corrosion kinetics under sliding compared to pure titanium. An antagonistic effect between wear and corrosion was observed for composites with at least two times decrease in wear volume compared to titanium. |
Gökbulut, Belkıs; Topcu, Gokhan; Demir, Mustafa M; Inci, Naci M: Plasmon-induced spectral tunability of Perovskite nanowires. Optical Materials, 122 , pp. 111702, 2021, ISSN: 0925-3467. (Type: Journal Article | Abstract | Links | BibTeX) @article{GOKBULUT2021111702, title = {Plasmon-induced spectral tunability of Perovskite nanowires}, author = {Belkıs Gökbulut and Gokhan Topcu and Mustafa M Demir and Naci M Inci}, url = {https://www.sciencedirect.com/science/article/pii/S0925346721009022}, doi = {https://doi.org/10.1016/j.optmat.2021.111702}, issn = {0925-3467}, year = {2021}, date = {2021-01-01}, journal = {Optical Materials}, volume = {122}, pages = {111702}, abstract = {In this paper, plasmon-assisted spectral tunability in random media, composed of Perovskite (CsPbBr3) nanowires surrounded by Au nanoparticle clusters in polystyrene matrix, is achieved. The interaction between the surface plasmons and the quantum sources is observed to generate photoluminescence from the higher excited state energy levels of the excited semiconductor nanowires, which results in a blueshifted fluorescence emission of 50 nm. The localized surface plasmon properties are also determined to be tuned by plasmonic pumping of the quantum sources at different resonant frequencies. Thus, the first observation of the tunable blueshifted fluorescence emission of the semiconductor nanocrystals surrounded by plasmonic nanoparticle aggregates is achieved. The dramatic changes in the spectral profiles of the fluorescent nanowires are attributed to be due to the fast dynamics surface enhanced fluorescence mechanism.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, plasmon-assisted spectral tunability in random media, composed of Perovskite (CsPbBr3) nanowires surrounded by Au nanoparticle clusters in polystyrene matrix, is achieved. The interaction between the surface plasmons and the quantum sources is observed to generate photoluminescence from the higher excited state energy levels of the excited semiconductor nanowires, which results in a blueshifted fluorescence emission of 50 nm. The localized surface plasmon properties are also determined to be tuned by plasmonic pumping of the quantum sources at different resonant frequencies. Thus, the first observation of the tunable blueshifted fluorescence emission of the semiconductor nanocrystals surrounded by plasmonic nanoparticle aggregates is achieved. The dramatic changes in the spectral profiles of the fluorescent nanowires are attributed to be due to the fast dynamics surface enhanced fluorescence mechanism. |
Ertuş, Burak E; Vakifahmetoglu, Cekdar; Öztürk, Abdullah: Enhanced methylene blue removal efficiency of TiO2 embedded porous glass. Journal of the European Ceramic Society, 41 (2), pp. 1530-1536, 2021, ISSN: 0955-2219. (Type: Journal Article | Abstract | Links | BibTeX) @article{ERTUS20211530, title = {Enhanced methylene blue removal efficiency of TiO2 embedded porous glass}, author = {Burak E Ertuş and Cekdar Vakifahmetoglu and Abdullah Öztürk}, url = {https://www.sciencedirect.com/science/article/pii/S0955221920307743}, doi = {https://doi.org/10.1016/j.jeurceramsoc.2020.09.047}, issn = {0955-2219}, year = {2021}, date = {2021-01-01}, journal = {Journal of the European Ceramic Society}, volume = {41}, number = {2}, pages = {1530-1536}, abstract = {A porous glass (PG) embedded with titanium dioxide (TiO2) was produced via impregnation of the PG with Titanium (IV) Isopropoxide solution followed by crystallization. N2 sorption analyses revealed that the specific surface area (SSA) and total pore volume of the PG reached to 358 m2/g and 0.370 cm3/g, respectively. The adsorption capacity of methylene blue (MB) for the glasses was measured in the dark, instead the photocatalytic MB removal efficiency was evaluated by the degradation of MB under UV light illumination using a UV–vis spectrometer. The MB removal efficiency of the TiO2 synthesized anatase powder was only 32.3 % whereas, for TiO2 embedded PG (TiPG) it was 91.6 %, and nearly complete (> 99 %) efficacy was achieved for TiO2 embedded alkaline leached PG (TiPG-AL) under UV illumination 3 h period. Better MB removal efficiency was attributed to high SSA and dispersion of nano size anatase TiO2 crystallites within the porous structure.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A porous glass (PG) embedded with titanium dioxide (TiO2) was produced via impregnation of the PG with Titanium (IV) Isopropoxide solution followed by crystallization. N2 sorption analyses revealed that the specific surface area (SSA) and total pore volume of the PG reached to 358 m2/g and 0.370 cm3/g, respectively. The adsorption capacity of methylene blue (MB) for the glasses was measured in the dark, instead the photocatalytic MB removal efficiency was evaluated by the degradation of MB under UV light illumination using a UV–vis spectrometer. The MB removal efficiency of the TiO2 synthesized anatase powder was only 32.3 % whereas, for TiO2 embedded PG (TiPG) it was 91.6 %, and nearly complete (> 99 %) efficacy was achieved for TiO2 embedded alkaline leached PG (TiPG-AL) under UV illumination 3 h period. Better MB removal efficiency was attributed to high SSA and dispersion of nano size anatase TiO2 crystallites within the porous structure. |
Altindag, Iffet Akkus; Akdogan, Yasar: Spectrophotometric characterization of plasticizer migration in poly(vinyl chloride)-based artificial leather. Materials Chemistry and Physics, 258 , pp. 123954, 2021, ISSN: 0254-0584. (Type: Journal Article | Abstract | Links | BibTeX) @article{ALTINDAG2021123954, title = {Spectrophotometric characterization of plasticizer migration in poly(vinyl chloride)-based artificial leather}, author = {Iffet Akkus Altindag and Yasar Akdogan}, url = {https://www.sciencedirect.com/science/article/pii/S0254058420313146}, doi = {https://doi.org/10.1016/j.matchemphys.2020.123954}, issn = {0254-0584}, year = {2021}, date = {2021-01-01}, journal = {Materials Chemistry and Physics}, volume = {258}, pages = {123954}, abstract = {Plasticized polyvinyl chloride (PVC) is one of the most commonly used material in the manufacture of artificial leather because of its flexibility, high durability and low cost. While hundreds of plasticizers have been produced to obtain PVC films and artificial leathers, it is important to choose the correct plasticizer to produce the desired products. Therefore, here five non-phthalate type plasticizers with three levels (40 phr, 60 phr and 80 phr); trioctyl trimelliate (TOTM), tributyl trimelliate (TBTM), dioctyl terephthalate (DOTP), dioctyl adipate (DOA) and dioctyl succinate (BIO) were used to prepare plasticized PVC films. They were studied in terms of their compabilities with PVC polymer chains, and their effects on mechanical properties of PVC films. Although, linear plasticizers e.g. BIO and DOA have higher compabilities with PVC, a branched plasticizer e.g. TOTM showed higher mechanical properties. Moreover, a new spectrophotometric method for determination of plasticizer migration from PVC polymer matrix to the surface of artifical leather was developed. According to lightness change on the surface of PVC artifical leather before and after heat treatment at 70 °C, the migration rates of used plasticizers increase in this order: TOTM < TBTM < DOTP < BIO < DOA.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Plasticized polyvinyl chloride (PVC) is one of the most commonly used material in the manufacture of artificial leather because of its flexibility, high durability and low cost. While hundreds of plasticizers have been produced to obtain PVC films and artificial leathers, it is important to choose the correct plasticizer to produce the desired products. Therefore, here five non-phthalate type plasticizers with three levels (40 phr, 60 phr and 80 phr); trioctyl trimelliate (TOTM), tributyl trimelliate (TBTM), dioctyl terephthalate (DOTP), dioctyl adipate (DOA) and dioctyl succinate (BIO) were used to prepare plasticized PVC films. They were studied in terms of their compabilities with PVC polymer chains, and their effects on mechanical properties of PVC films. Although, linear plasticizers e.g. BIO and DOA have higher compabilities with PVC, a branched plasticizer e.g. TOTM showed higher mechanical properties. Moreover, a new spectrophotometric method for determination of plasticizer migration from PVC polymer matrix to the surface of artifical leather was developed. According to lightness change on the surface of PVC artifical leather before and after heat treatment at 70 °C, the migration rates of used plasticizers increase in this order: TOTM < TBTM < DOTP < BIO < DOA. |
Seçil Sevim Ünlütürk, Yaşar Akdoğan ; Özçelik, Serdar: Mn2+ ions incorporated into ZnSxSe1−x colloidal quantum dots: controlling size and composition of nanoalloys and regulating magnetic dipolar interactions. Nanotechnology, 32 (16), pp. 165701, 2021. (Type: Journal Article | Abstract | Links | BibTeX) @article{Sevim_nl_t_rk_2021b, title = {Mn2+ ions incorporated into ZnSxSe1−x colloidal quantum dots: controlling size and composition of nanoalloys and regulating magnetic dipolar interactions}, author = {Seçil Sevim Ünlütürk, Yaşar Akdoğan and Serdar Özçelik}, url = {https://doi.org/10.1088/1361-6528/abdb65}, doi = {10.1088/1361-6528/abdb65}, year = {2021}, date = {2021-01-01}, journal = {Nanotechnology}, volume = {32}, number = {16}, pages = {165701}, publisher = {IOP Publishing}, abstract = {A facile synthesis method is introduced how to prepare magnetically active ultraviolet emitting manganese ions incorporated into ZnS x Se1−x colloidal quantum dot (nanoalloy) at 110 °C in aqueous solutions. The reaction time is the main factor to control the hydrodynamic size from 3 to 10 nm and the precursor ratio is significant to tune the alloy composition. ZnS shell layer on the ZnS x Se1−x core was grown to passivate environmental effects. The nanoalloy has ultraviolet emission at 380 nm having a lifetime of 80 ns and 7% quantum yield. The incorporation of Mn2+ ions into the nanoalloys induced magnetic activity but did not modify the structure and photophysical properties of the nanoalloys. Colloidal and powdery samples were prepared and analyzed by electron paramagnetic resonance (EPR) spectroscopy. In the colloidal dispersions, EPR spectra showed hyperfine line splitting regardless of the Mn2+ ion fractions, up to 6%, indicating that Mn2+ ions incorporated into the nanoalloys were isolated. EPR signals of the powdery samples were broadened when the fraction of Mn2+ ions was higher than 0.1%. The EPR spectra were simulated to reveal the locations and interactions of Mn2+ ions. The simulations suggest that the Mn2+ ions are located on the nanoalloy surfaces. These findings infer that the magnetic dipolar interactions are regulated by the initial mole ratio of Mn/Zn and the physical state of the nanoalloys adjusted by preparation methods.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A facile synthesis method is introduced how to prepare magnetically active ultraviolet emitting manganese ions incorporated into ZnS x Se1−x colloidal quantum dot (nanoalloy) at 110 °C in aqueous solutions. The reaction time is the main factor to control the hydrodynamic size from 3 to 10 nm and the precursor ratio is significant to tune the alloy composition. ZnS shell layer on the ZnS x Se1−x core was grown to passivate environmental effects. The nanoalloy has ultraviolet emission at 380 nm having a lifetime of 80 ns and 7% quantum yield. The incorporation of Mn2+ ions into the nanoalloys induced magnetic activity but did not modify the structure and photophysical properties of the nanoalloys. Colloidal and powdery samples were prepared and analyzed by electron paramagnetic resonance (EPR) spectroscopy. In the colloidal dispersions, EPR spectra showed hyperfine line splitting regardless of the Mn2+ ion fractions, up to 6%, indicating that Mn2+ ions incorporated into the nanoalloys were isolated. EPR signals of the powdery samples were broadened when the fraction of Mn2+ ions was higher than 0.1%. The EPR spectra were simulated to reveal the locations and interactions of Mn2+ ions. The simulations suggest that the Mn2+ ions are located on the nanoalloy surfaces. These findings infer that the magnetic dipolar interactions are regulated by the initial mole ratio of Mn/Zn and the physical state of the nanoalloys adjusted by preparation methods. |
Alp, Emre; İmamoğlu, Rizvan; Savacı, Umut; Turan, Servet; Kazmanlı, M.Kürşat; Genç, Aziz: Plasmon-enhanced photocatalytic and antibacterial activity of gold nanoparticles-decorated hematite nanostructures. Journal of Alloys and Compounds, 852 , pp. 157021, 2021, ISSN: 0925-8388. (Type: Journal Article | Abstract | Links | BibTeX) @article{ALP2021157021, title = {Plasmon-enhanced photocatalytic and antibacterial activity of gold nanoparticles-decorated hematite nanostructures}, author = {Emre Alp and Rizvan İmamoğlu and Umut Savacı and Servet Turan and M.Kürşat Kazmanlı and Aziz Genç}, url = {https://www.sciencedirect.com/science/article/pii/S0925838820333855}, doi = {https://doi.org/10.1016/j.jallcom.2020.157021}, issn = {0925-8388}, year = {2021}, date = {2021-01-01}, journal = {Journal of Alloys and Compounds}, volume = {852}, pages = {157021}, abstract = {Hematite (α-Fe2O3) nanoparticles have received significant attention from the researchers due to their favorable and desirable properties in diverse applications. In the present study, single-crystalline hematite pseudo-nanocubes and porous nanorods were synthesized by the hydrothermal route without the usage of any surfactant agents, which were then decorated with gold nanoparticles hidrothermally in an aqueous solution in order to increase the solar energy conversion efficiency. The photocatalytic activities of synthesized nanoparticles were studied against Rhodamine B (RhB) under the illumination of AM 1.5 solar simulator. The excellent photocatalytic efficiency was obtained by changing morphological features of hematite nanostructures, along with the photocatalytic performance enhancement up to 25% thanks to the surface plasmon resonances for the gold nanoparticles-decorated hematite nanostructures. For instance, gold-nanoparticles decorated hematite pseudo-nanocubes almost completely degraded all the RhB after 30 min of illumination. It was also observed that all hematite products, with and without gold decoration, exhibited an impressive antibacterial effect and showed the lethal effect in E.coli. The same nanoparticles being photocatalytically active for organic pollutant degradation and having antibacterial effect may have a good potential for waste water remediation applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hematite (α-Fe2O3) nanoparticles have received significant attention from the researchers due to their favorable and desirable properties in diverse applications. In the present study, single-crystalline hematite pseudo-nanocubes and porous nanorods were synthesized by the hydrothermal route without the usage of any surfactant agents, which were then decorated with gold nanoparticles hidrothermally in an aqueous solution in order to increase the solar energy conversion efficiency. The photocatalytic activities of synthesized nanoparticles were studied against Rhodamine B (RhB) under the illumination of AM 1.5 solar simulator. The excellent photocatalytic efficiency was obtained by changing morphological features of hematite nanostructures, along with the photocatalytic performance enhancement up to 25% thanks to the surface plasmon resonances for the gold nanoparticles-decorated hematite nanostructures. For instance, gold-nanoparticles decorated hematite pseudo-nanocubes almost completely degraded all the RhB after 30 min of illumination. It was also observed that all hematite products, with and without gold decoration, exhibited an impressive antibacterial effect and showed the lethal effect in E.coli. The same nanoparticles being photocatalytically active for organic pollutant degradation and having antibacterial effect may have a good potential for waste water remediation applications. |
Özsoylu, Dua; Isık, Tuğba; Demir, Mustafa M; Schöning, Michael J; Wagner, Torsten: Cryopreservation of a cell-based biosensor chip modified with elastic polymer fibers enabling ready-to-use on-site applications. Biosensors and Bioelectronics, 177 , pp. 112983, 2021, ISSN: 0956-5663. (Type: Journal Article | Abstract | Links | BibTeX) @article{OZSOYLU2021112983, title = {Cryopreservation of a cell-based biosensor chip modified with elastic polymer fibers enabling ready-to-use on-site applications}, author = {Dua Özsoylu and Tuğba Isık and Mustafa M Demir and Michael J Schöning and Torsten Wagner}, url = {https://www.sciencedirect.com/science/article/pii/S0956566321000191}, doi = {https://doi.org/10.1016/j.bios.2021.112983}, issn = {0956-5663}, year = {2021}, date = {2021-01-01}, journal = {Biosensors and Bioelectronics}, volume = {177}, pages = {112983}, abstract = {An efficient preservation of a cell-based biosensor chip to achieve a ready-to-use on-site system is still very challenging as the chip contains a living component such as adherent mammalian cells. Herein, we propose a strategy called on-sensor cryopreservation (OSC), which enables the adherent cells to be preserved by freezing (−80 °C) on a biosensor surface, such as the light-addressable potentiometric sensor (LAPS). Adherent cells on rigid surfaces are prone to cryo-injury; thus, the surface was modified to enhance the cell recovery for OSC. It relies on i) the integration of elastic electrospun fibers composed of polyethylene vinyl acetate (PEVA), which has a high thermal expansion coefficient and low glass-transition temperature, and ii) the treatment with O2 plasma. The modified sensor is integrated into a microfluidic chip system not only to decrease the thermal mass, which is critical for fast thawing, but also to provide a precisely controlled micro-environment. This novel cryo-chip system is effective for keeping cells viable during OSC. As a proof-of-concept for the applicability of a ready-to-use format, the extracellular acidification of cancer cells (CHO-K1) was evaluated by differential LAPS measurements after thawing. Results show, for the first time, that the OSC strategy using the cryo-chip allows label-free and quantitative measurements directly after thawing, which eliminates additional post-thaw culturing steps. The freezing of the chips containing cells at the manufacturing stage and sending them via a cold-chain transport could open up a new possibility for a ready-to-use on-site system.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An efficient preservation of a cell-based biosensor chip to achieve a ready-to-use on-site system is still very challenging as the chip contains a living component such as adherent mammalian cells. Herein, we propose a strategy called on-sensor cryopreservation (OSC), which enables the adherent cells to be preserved by freezing (−80 °C) on a biosensor surface, such as the light-addressable potentiometric sensor (LAPS). Adherent cells on rigid surfaces are prone to cryo-injury; thus, the surface was modified to enhance the cell recovery for OSC. It relies on i) the integration of elastic electrospun fibers composed of polyethylene vinyl acetate (PEVA), which has a high thermal expansion coefficient and low glass-transition temperature, and ii) the treatment with O2 plasma. The modified sensor is integrated into a microfluidic chip system not only to decrease the thermal mass, which is critical for fast thawing, but also to provide a precisely controlled micro-environment. This novel cryo-chip system is effective for keeping cells viable during OSC. As a proof-of-concept for the applicability of a ready-to-use format, the extracellular acidification of cancer cells (CHO-K1) was evaluated by differential LAPS measurements after thawing. Results show, for the first time, that the OSC strategy using the cryo-chip allows label-free and quantitative measurements directly after thawing, which eliminates additional post-thaw culturing steps. The freezing of the chips containing cells at the manufacturing stage and sending them via a cold-chain transport could open up a new possibility for a ready-to-use on-site system. |
Liu, Yu; Calcabrini, Mariano; Yu, Yuan; Genç, Aziz; Chang, Cheng; Costanzo, Tommaso; Kleinhanns, Tobias; Lee, Seungho; Llorca, Jordi; Cojocaru-Mirédin, Oana; Ibáñez, Maria: The Importance of Surface Adsorbates in Solution-Processed Thermoelectric Materials: The Case of SnSe. Advanced Materials, 33 (52), pp. 2106858, 2021. (Type: Journal Article | Abstract | Links | BibTeX) @article{https://doi.org/10.1002/adma.202106858, title = {The Importance of Surface Adsorbates in Solution-Processed Thermoelectric Materials: The Case of SnSe}, author = {Yu Liu and Mariano Calcabrini and Yuan Yu and Aziz Genç and Cheng Chang and Tommaso Costanzo and Tobias Kleinhanns and Seungho Lee and Jordi Llorca and Oana Cojocaru-Mirédin and Maria Ibáñez}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202106858}, doi = {https://doi.org/10.1002/adma.202106858}, year = {2021}, date = {2021-01-01}, journal = {Advanced Materials}, volume = {33}, number = {52}, pages = {2106858}, abstract = {Abstract Solution synthesis of particles emerges as an alternative to prepare thermoelectric materials with less demanding processing conditions than conventional solid-state synthetic methods. However, solution synthesis generally involves the presence of additional molecules or ions belonging to the precursors or added to enable solubility and/or regulate nucleation and growth. These molecules or ions can end up in the particles as surface adsorbates and interfere in the material properties. This work demonstrates that ionic adsorbates, in particular Na+ ions, are electrostatically adsorbed in SnSe particles synthesized in water and play a crucial role not only in directing the material nano/microstructure but also in determining the transport properties of the consolidated material. In dense pellets prepared by sintering SnSe particles, Na remains within the crystal lattice as dopant, in dislocations, precipitates, and forming grain boundary complexions. These results highlight the importance of considering all the possible unintentional impurities to establish proper structure–property relationships and control material properties in solution-processed thermoelectric materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract Solution synthesis of particles emerges as an alternative to prepare thermoelectric materials with less demanding processing conditions than conventional solid-state synthetic methods. However, solution synthesis generally involves the presence of additional molecules or ions belonging to the precursors or added to enable solubility and/or regulate nucleation and growth. These molecules or ions can end up in the particles as surface adsorbates and interfere in the material properties. This work demonstrates that ionic adsorbates, in particular Na+ ions, are electrostatically adsorbed in SnSe particles synthesized in water and play a crucial role not only in directing the material nano/microstructure but also in determining the transport properties of the consolidated material. In dense pellets prepared by sintering SnSe particles, Na remains within the crystal lattice as dopant, in dislocations, precipitates, and forming grain boundary complexions. These results highlight the importance of considering all the possible unintentional impurities to establish proper structure–property relationships and control material properties in solution-processed thermoelectric materials. |
Cadavid, Doris; Wei, Kaya; Liu, Yu; Zhang, Yu; Li, Mengyao; Genç, Aziz; Berestok, Taisiia; Ibáñez, Maria; Shavel, Alexey; Nolas, George S; Cabot, Andreu: Synthesis, Bottom up Assembly and Thermoelectric Properties of Sb-Doped PbS Nanocrystal Building Blocks. Materials, 14 (4), 2021, ISSN: 1996-1944. (Type: Journal Article | Links | BibTeX) @article{ma14040853, title = {Synthesis, Bottom up Assembly and Thermoelectric Properties of Sb-Doped PbS Nanocrystal Building Blocks}, author = {Doris Cadavid and Kaya Wei and Yu Liu and Yu Zhang and Mengyao Li and Aziz Genç and Taisiia Berestok and Maria Ibáñez and Alexey Shavel and George S Nolas and Andreu Cabot}, url = {https://www.mdpi.com/1996-1944/14/4/853}, doi = {10.3390/ma14040853}, issn = {1996-1944}, year = {2021}, date = {2021-01-01}, journal = {Materials}, volume = {14}, number = {4}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Levanyuk, Arkady P; Minyukov, Sergey A; Misirlioglu, Burc I; Okatan, Baris M: Effects of interphase boundaries in Ginzburg–Landau one-dimensional model of two-phase states in clamped systems. Journal of Applied Physics, 129 (4), pp. 044102, 2021. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/5.0029144, title = {Effects of interphase boundaries in Ginzburg–Landau one-dimensional model of two-phase states in clamped systems}, author = {Arkady P Levanyuk and Sergey A Minyukov and I Burc Misirlioglu and M Baris Okatan}, url = {https://doi.org/10.1063/5.0029144}, doi = {10.1063/5.0029144}, year = {2021}, date = {2021-01-01}, journal = {Journal of Applied Physics}, volume = {129}, number = {4}, pages = {044102}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Çaha, I; Alves, A C; Affonço, L J; da Silva, J H D; Rodrigues, I R; Grandini, C R; Rocha, L A; Pinto, A M P; Lisboa-Filho, P N; Toptan, F: Degradation behaviour of Ti-12Nb alloy coated with ZnO/TiN double layer. Surface and Coatings Technology, 413 , pp. 127104, 2021, ISSN: 0257-8972. (Type: Journal Article | Abstract | Links | BibTeX) @article{CAHA2021127104, title = {Degradation behaviour of Ti-12Nb alloy coated with ZnO/TiN double layer}, author = {I Çaha and A C Alves and L J Affonço and J H D da Silva and I R Rodrigues and C R Grandini and L A Rocha and A M P Pinto and P N Lisboa-Filho and F Toptan}, url = {https://www.sciencedirect.com/science/article/pii/S0257897221002784}, doi = {https://doi.org/10.1016/j.surfcoat.2021.127104}, issn = {0257-8972}, year = {2021}, date = {2021-01-01}, journal = {Surface and Coatings Technology}, volume = {413}, pages = {127104}, abstract = {Ti and its alloys have attracted attention for biomedical applications, but their low tribocorrosion resistance, lack of bioactivity and antimicrobial properties are still major clinical concerns. In this study a ZnO coating, intended to act as an antibacterial agent, was deposited on a Ti-12Nb alloy, which was previously coated with a TiN hard coating, for improving tribocorrosion resistance. The idea behind is the proof-of -concept that ZnO is able to provide interesting tribological properties to the surface, thus inspiring new ZnO-containing surfaces that can combine antimicrobial properties and tribocorrosion resistance. Thus, the corrosion behaviour was studied by open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization tests in phosphate buffered solution at body temperature. The tribocorrosion behaviour was carried out at open circuit potential under 0.5 N of normal load, 1 Hz frequency, during 3600 s sliding in phosphate buffered solution at body temperature. The results indicated that duplex coating sample showed better corrosion resistance and drastically better tribocorrosion resistance compared to uncoated and single TiN coating samples.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ti and its alloys have attracted attention for biomedical applications, but their low tribocorrosion resistance, lack of bioactivity and antimicrobial properties are still major clinical concerns. In this study a ZnO coating, intended to act as an antibacterial agent, was deposited on a Ti-12Nb alloy, which was previously coated with a TiN hard coating, for improving tribocorrosion resistance. The idea behind is the proof-of -concept that ZnO is able to provide interesting tribological properties to the surface, thus inspiring new ZnO-containing surfaces that can combine antimicrobial properties and tribocorrosion resistance. Thus, the corrosion behaviour was studied by open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization tests in phosphate buffered solution at body temperature. The tribocorrosion behaviour was carried out at open circuit potential under 0.5 N of normal load, 1 Hz frequency, during 3600 s sliding in phosphate buffered solution at body temperature. The results indicated that duplex coating sample showed better corrosion resistance and drastically better tribocorrosion resistance compared to uncoated and single TiN coating samples. |
Aldulaimi, W A S; Akaoglu, C; Sendur, K; Okatan, M B; Misirlioglu, I B: Chirality Switching in Ferromagnetic Nanostructures Via Nanosecond Electric Pulses. Annalen der Physik, 533 (10), pp. 2100167, 2021. (Type: Journal Article | Abstract | Links | BibTeX) @article{https://doi.org/10.1002/andp.202100167, title = {Chirality Switching in Ferromagnetic Nanostructures Via Nanosecond Electric Pulses}, author = {W A S Aldulaimi and C Akaoglu and K Sendur and M B Okatan and I B Misirlioglu}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/andp.202100167}, doi = {https://doi.org/10.1002/andp.202100167}, year = {2021}, date = {2021-01-01}, journal = {Annalen der Physik}, volume = {533}, number = {10}, pages = {2100167}, abstract = {Abstract The stability of magnetism in reduced dimensions has become a major scientific agenda in the pursuit of implementing magnetic nanostructures as functional components in spintronic devices. Methods to probe and control magnetization states of such structures in a deterministic manner include use of spin polarized currents, photon absorption, and relatively recently, electric fields that tailor magnetoelectric coupling in multiferroic based structures. In theory, a short electric pulse is able to generate localized magnetic fields that can couple to the local magnetic dipoles electrodynamically. Here, using the Landau–Lifshitz–Gilbert formalism of magnetism dynamics combined with continuum Maxwell relations, the response of a ferromagnetic permalloy nanodisc to nanosecond electric field pulses is studied. The dynamics of the magnetic order of the nanodiscs during this process are examined and discussed. Ferromagnet nanodiscs, when below a critical size and in the absence of any external field, relax to a vortex phase as the ground state due to the demagnetizing field. Simulations demonstrate that the planar chirality of such a ferromagnet nanodisc can be switched via a time-wise asymmetric electric field pulse on the order of a few ns duration that generates radially varying tangential magnetic fields. These fields couple to the vortex state of the nanodisc ferromagnet electrodynamically, revealing an effective and robust method to control chirality.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract The stability of magnetism in reduced dimensions has become a major scientific agenda in the pursuit of implementing magnetic nanostructures as functional components in spintronic devices. Methods to probe and control magnetization states of such structures in a deterministic manner include use of spin polarized currents, photon absorption, and relatively recently, electric fields that tailor magnetoelectric coupling in multiferroic based structures. In theory, a short electric pulse is able to generate localized magnetic fields that can couple to the local magnetic dipoles electrodynamically. Here, using the Landau–Lifshitz–Gilbert formalism of magnetism dynamics combined with continuum Maxwell relations, the response of a ferromagnetic permalloy nanodisc to nanosecond electric field pulses is studied. The dynamics of the magnetic order of the nanodiscs during this process are examined and discussed. Ferromagnet nanodiscs, when below a critical size and in the absence of any external field, relax to a vortex phase as the ground state due to the demagnetizing field. Simulations demonstrate that the planar chirality of such a ferromagnet nanodisc can be switched via a time-wise asymmetric electric field pulse on the order of a few ns duration that generates radially varying tangential magnetic fields. These fields couple to the vortex state of the nanodisc ferromagnet electrodynamically, revealing an effective and robust method to control chirality. |
Unsal, E; Senger, R T; mbox ç}else çfi{, Sevinifmmode H: Enhancement of thermoelectric efficiency of $Ttextensuremath-mathrmHfSe_2$ via nanostructuring. Phys. Rev. B, 103 , pp. 014104, 2021. (Type: Journal Article | Links | BibTeX) @article{PhysRevB.103.014104, title = {Enhancement of thermoelectric efficiency of $Ttextensuremath-mathrmHfSe_2$ via nanostructuring}, author = {E Unsal and R T Senger and H Sevinifmmode mbox{ç}else çfi{}li}, url = {https://link.aps.org/doi/10.1103/PhysRevB.103.014104}, doi = {10.1103/PhysRevB.103.014104}, year = {2021}, date = {2021-01-01}, journal = {Phys. Rev. B}, volume = {103}, pages = {014104}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
E. Unsal R. T. Senger, ; Sevinçli, H: Enhancement of thermoelectric efficiency of T−HfSe2 via nanostructuring. Phys. Rev. B, 103 , pp. 014104, 2021. (Type: Journal Article | Links | BibTeX) @article{PhysRevB.103.014104b, title = {Enhancement of thermoelectric efficiency of T−HfSe2 via nanostructuring}, author = {E. Unsal, R. T. Senger, and H. Sevinçli}, url = {https://link.aps.org/doi/10.1103/PhysRevB.103.014104}, doi = {10.1103/PhysRevB.103.014104}, year = {2021}, date = {2021-01-01}, journal = {Phys. Rev. B}, volume = {103}, pages = {014104}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2020 |
Kurt, G; Sevinçli, H: First-Principles Investigation of Photoisomeric Switching of Vibrational Heat Current across Molecular Junctions. Phys. Rev. Applied, 14 , pp. 064045, 2020. (Type: Journal Article | Links | BibTeX) @article{PhysRevApplied.14.064045, title = {First-Principles Investigation of Photoisomeric Switching of Vibrational Heat Current across Molecular Junctions}, author = {G Kurt and H Sevinçli}, url = {https://link.aps.org/doi/10.1103/PhysRevApplied.14.064045}, doi = {10.1103/PhysRevApplied.14.064045}, year = {2020}, date = {2020-12-01}, journal = {Phys. Rev. Applied}, volume = {14}, pages = {064045}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Semerci, Tugce; de Innocentini, Murilo Daniel Mello; Marsola, Gabriel Antonio; Lasso, Paulo Renato Orlandi; Soraru, Gian Domenico; Vakifahmetoglu, Cekdar: Hot Air Permeable Preceramic Polymer Derived Reticulated Ceramic Foams. ACS Applied Polymer Materials, 2 (9), pp. 4118-4126, 2020. (Type: Journal Article | Links | BibTeX) @article{Semerci2020, title = {Hot Air Permeable Preceramic Polymer Derived Reticulated Ceramic Foams}, author = {Tugce Semerci and Murilo Daniel de Mello Innocentini and Gabriel Antonio Marsola and Paulo Renato Orlandi Lasso and Gian Domenico Soraru and Cekdar Vakifahmetoglu}, url = {https://doi.org/10.1021/acsapm.0c00734}, doi = {10.1021/acsapm.0c00734}, year = {2020}, date = {2020-09-11}, journal = {ACS Applied Polymer Materials}, volume = {2}, number = {9}, pages = {4118-4126}, publisher = {American Chemical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Çiftçi, Celal; Karaburun, Emre; Tonkul, Serhat; Baba, Alper; Demir, Mustafa M; Yeşilnacar, Mehmet İrfan: Testing the Performance of Various Polymeric Antiscalants for Mitigation of Sb-Rich Precipitates Mimicking Stibnite-Based Geothermal Deposits. Geofluids, 2020 , pp. 8867084, 2020, ISSN: 1468-8115. (Type: Journal Article | Abstract | Links | BibTeX) @article{Çiftçi2020, title = {Testing the Performance of Various Polymeric Antiscalants for Mitigation of Sb-Rich Precipitates Mimicking Stibnite-Based Geothermal Deposits}, author = {Celal Çiftçi and Emre Karaburun and Serhat Tonkul and Alper Baba and Mustafa M Demir and Mehmet İrfan Yeşilnacar}, url = {https://doi.org/10.1155/2020/8867084}, doi = {10.1155/2020/8867084}, issn = {1468-8115}, year = {2020}, date = {2020-08-01}, journal = {Geofluids}, volume = {2020}, pages = {8867084}, publisher = {Hindawi}, abstract = {Scaling is frequently observed in geothermal fields and reduces the energy harvesting of power plants. Recently, Sb-rich deposits have developed in many fields around the world. Various polymeric macromolecules have been used as antiscalants to mitigate the formation of scale. Testing potential commercial antiscalants in field conditions is a tedious and costly process. The artificial synthesis of geothermal deposits in the lab is a more practical and economical way to test the performance of antiscalants. This study obtained a Sb-rich deposit by refluxing SbCl_{3} and Na_{2}S·3H_{2}O in 18 h. The product was found to be a mixture of Sb_{2}O_{3} and Sb_{2}S_{3}. We examined the performance of antiscalants such as poly(ethylene glycol), poly(vinyl pyrrolidone), Gelatin, and poly(vinyl alcohol) of various molecular weights at 5 to 100 ppm. The formation of Sb_{2}S_{3} is suppressed in the presence of the polymeric antiscalants. The dosage was found to be critical for the solubilization of Sb-rich deposits. Gelatin of 5 ppm showed the highest performance under the conditions employed in this study. While low dosages improve the concentration of [Sb^{3+}], high dosages are required to increase the solubility of [S^{2-}]. Moreover, the amount of deposit is reduced by 12.4% compared to the reference (in the absence of any polymeric molecules). Thus, comparatively, Gelatin shows the most promising performance among the molecules employed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Scaling is frequently observed in geothermal fields and reduces the energy harvesting of power plants. Recently, Sb-rich deposits have developed in many fields around the world. Various polymeric macromolecules have been used as antiscalants to mitigate the formation of scale. Testing potential commercial antiscalants in field conditions is a tedious and costly process. The artificial synthesis of geothermal deposits in the lab is a more practical and economical way to test the performance of antiscalants. This study obtained a Sb-rich deposit by refluxing SbCl3 and Na2S·3H2O in 18 h. The product was found to be a mixture of Sb2O3 and Sb2S3. We examined the performance of antiscalants such as poly(ethylene glycol), poly(vinyl pyrrolidone), Gelatin, and poly(vinyl alcohol) of various molecular weights at 5 to 100 ppm. The formation of Sb2S3 is suppressed in the presence of the polymeric antiscalants. The dosage was found to be critical for the solubilization of Sb-rich deposits. Gelatin of 5 ppm showed the highest performance under the conditions employed in this study. While low dosages improve the concentration of [Sb3+], high dosages are required to increase the solubility of [S2-]. Moreover, the amount of deposit is reduced by 12.4% compared to the reference (in the absence of any polymeric molecules). Thus, comparatively, Gelatin shows the most promising performance among the molecules employed. |
Çınar, Neşet M; Sevinçli, H: Dimensional Crossover and Enhanced Thermoelectric Efficiency Due to Broken Symmetry in Graphene Antidot Lattices. Phys. Rev. Applied, 14 , pp. 024075, 2020. (Type: Journal Article | Links | BibTeX) @article{PhysRevApplied.14.024075, title = {Dimensional Crossover and Enhanced Thermoelectric Efficiency Due to Broken Symmetry in Graphene Antidot Lattices}, author = {M. Neşet Çınar and H. Sevinçli}, url = {https://link.aps.org/doi/10.1103/PhysRevApplied.14.024075}, doi = {10.1103/PhysRevApplied.14.024075}, year = {2020}, date = {2020-08-01}, journal = {Phys. Rev. Applied}, volume = {14}, pages = {024075}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Mustafa Polat Hâldun Sevinçli, ; Güçlü, A D: Collapse of the vacuum in hexagonal graphene quantum dots: A comparative study between tight-binding and mean-field Hubbard models. Phys. Rev. B, 101 , pp. 205429, 2020. (Type: Journal Article | Links | BibTeX) @article{PhysRevB.101.205429, title = {Collapse of the vacuum in hexagonal graphene quantum dots: A comparative study between tight-binding and mean-field Hubbard models}, author = {Mustafa Polat, Hâldun Sevinçli, and A. D. Güçlü}, url = {https://link.aps.org/doi/10.1103/PhysRevB.101.205429}, doi = {10.1103/PhysRevB.101.205429}, year = {2020}, date = {2020-05-01}, journal = {Phys. Rev. B}, volume = {101}, pages = {205429}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Inci, Ezgi; Topcu, Gokhan; Guner, Tugrul; Demirkurt, Merve; Demir, Mustafa M: Recent developments of colorimetric mechanical sensors based on polymer composites. J. Mater. Chem. C, 8 , pp. 12036-12053, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{D0TC02600J, title = {Recent developments of colorimetric mechanical sensors based on polymer composites}, author = {Ezgi Inci and Gokhan Topcu and Tugrul Guner and Merve Demirkurt and Mustafa M Demir}, url = {http://dx.doi.org/10.1039/D0TC02600J}, doi = {10.1039/D0TC02600J}, year = {2020}, date = {2020-01-01}, journal = {J. Mater. Chem. C}, volume = {8}, pages = {12036-12053}, publisher = {The Royal Society of Chemistry}, abstract = {Colorimetric mechanical (force, pressure, strain, and impact) sensors allow naked-eye visualization of existing structural deformations of a system occurring upon application of a mechanical action. The combination of mechanochromic materials with polymers offers a practical approach to designing and fabricating these sensors. Polymers as matrices can tolerate a wide range of forces and permits reusability of the sensors. On the other hand, mechanochromic materials provide unique colour properties depending on the type of mechanical action. They have also been frequently employed for the quantification of mechanical forces. As an example, non-centrosymmetric crystals are combined with polymers for sensing impact forces. Structures with photoluminescence and scattering and plasmonic resonances can be used to fabricate strain and pressure responsive composite materials, respectively. This study reviews recent advances in colorimetric mechanical sensor systems prepared using polymers and inorganic and organic mechanochromic materials working under a wide range of forces.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Colorimetric mechanical (force, pressure, strain, and impact) sensors allow naked-eye visualization of existing structural deformations of a system occurring upon application of a mechanical action. The combination of mechanochromic materials with polymers offers a practical approach to designing and fabricating these sensors. Polymers as matrices can tolerate a wide range of forces and permits reusability of the sensors. On the other hand, mechanochromic materials provide unique colour properties depending on the type of mechanical action. They have also been frequently employed for the quantification of mechanical forces. As an example, non-centrosymmetric crystals are combined with polymers for sensing impact forces. Structures with photoluminescence and scattering and plasmonic resonances can be used to fabricate strain and pressure responsive composite materials, respectively. This study reviews recent advances in colorimetric mechanical sensor systems prepared using polymers and inorganic and organic mechanochromic materials working under a wide range of forces. |
Inci, Ezgi; Topcu, Gokhan; Demir, Mustafa M: Colloidal films of SiO2 in elastomeric polyacrylates by photopolymerization: A strain sensor application. Sensors and Actuators B: Chemical, 305 , pp. 127452, 2020, ISSN: 0925-4005. (Type: Journal Article | Abstract | Links | BibTeX) @article{INCI2020127452, title = {Colloidal films of SiO2 in elastomeric polyacrylates by photopolymerization: A strain sensor application}, author = {Ezgi Inci and Gokhan Topcu and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S092540051931651X}, doi = {https://doi.org/10.1016/j.snb.2019.127452}, issn = {0925-4005}, year = {2020}, date = {2020-01-01}, journal = {Sensors and Actuators B: Chemical}, volume = {305}, pages = {127452}, abstract = {Thin layer SiO2 colloidal films show angle-dependent coloration (iridescence) based on constructive interference, rather than absorption, without the existence of pigments. The transfer of thin layered colloidal film into a transparent elastomeric matrix maintaining its color may allow the fabrication of colorimetric strain sensors. In this study, trilayer SiO2 colloidal films were prepared by Langmuir-Blodgett deposition using a binary solvent system (chloroform/methanol) and this structure is successfully transferred into poly(ethylene glycol) phenyl ether acrylate elastomer via lateral capillary force. The resulting composite films exhibit iridescence depending on the particle size, therefore, film thickness as similar in mere colloidal films with a slight difference due to change in efficient refractive index (neff). Uniaxial extension of the composite film up to 50 % strain causes a remarkable linear shift in reflection signal from 568 to 496 nm. The change in thickness of the composite film accordingly intercolloidal distance normal to the application of mechanical stretching causes variation of the reflection of light.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thin layer SiO2 colloidal films show angle-dependent coloration (iridescence) based on constructive interference, rather than absorption, without the existence of pigments. The transfer of thin layered colloidal film into a transparent elastomeric matrix maintaining its color may allow the fabrication of colorimetric strain sensors. In this study, trilayer SiO2 colloidal films were prepared by Langmuir-Blodgett deposition using a binary solvent system (chloroform/methanol) and this structure is successfully transferred into poly(ethylene glycol) phenyl ether acrylate elastomer via lateral capillary force. The resulting composite films exhibit iridescence depending on the particle size, therefore, film thickness as similar in mere colloidal films with a slight difference due to change in efficient refractive index (neff). Uniaxial extension of the composite film up to 50 % strain causes a remarkable linear shift in reflection signal from 568 to 496 nm. The change in thickness of the composite film accordingly intercolloidal distance normal to the application of mechanical stretching causes variation of the reflection of light. |
Ertuş, Burak E; Vakifahmetoglu, Cekdar; Öztürk, Abdullah: Production and properties of phase separated porous glass. Ceramics International, 46 (4), pp. 4947-4951, 2020, ISSN: 0272-8842. (Type: Journal Article | Abstract | Links | BibTeX) @article{ERTUS20204947, title = {Production and properties of phase separated porous glass}, author = {Burak E Ertuş and Cekdar Vakifahmetoglu and Abdullah Öztürk}, url = {https://www.sciencedirect.com/science/article/pii/S0272884219331062}, doi = {https://doi.org/10.1016/j.ceramint.2019.10.232}, issn = {0272-8842}, year = {2020}, date = {2020-01-01}, journal = {Ceramics International}, volume = {46}, number = {4}, pages = {4947-4951}, abstract = {A sodium borosilicate glass (SBG) was produced by conventional melt-quenching. As cast glass was heat treated to induce phase separation (SBG-HT), followed by acid leaching with HCl to dissolve one of the separated phases; i.e. alkali rich borate phase, so that a porous glass (PG) was obtained. In order to alter the pore structure, produced PG was subsequently alkali (NaOH) leached or alternatively heat treated. The samples were characterized by techniques including XRD, SEM, N2 adsorption/desorption. The total pore volume for PG was found to be 0.314 cm3/g, reached to 0.370 cm3/g by alkali leaching, instead decreased to 0.227 cm3/g by heat treatment. The microhardness and tribological properties of SBG-HT and all PGs were evaluated by Vickers hardness and by pin on disk tribometer. For all PGs the microhardness values were lower, instead the wear rates were higher than that of the parent SBG-HT.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A sodium borosilicate glass (SBG) was produced by conventional melt-quenching. As cast glass was heat treated to induce phase separation (SBG-HT), followed by acid leaching with HCl to dissolve one of the separated phases; i.e. alkali rich borate phase, so that a porous glass (PG) was obtained. In order to alter the pore structure, produced PG was subsequently alkali (NaOH) leached or alternatively heat treated. The samples were characterized by techniques including XRD, SEM, N2 adsorption/desorption. The total pore volume for PG was found to be 0.314 cm3/g, reached to 0.370 cm3/g by alkali leaching, instead decreased to 0.227 cm3/g by heat treatment. The microhardness and tribological properties of SBG-HT and all PGs were evaluated by Vickers hardness and by pin on disk tribometer. For all PGs the microhardness values were lower, instead the wear rates were higher than that of the parent SBG-HT. |
Karacasulu, Levent; Tokkan, Melike; Bortolotti, Mauro; Ischia, Gloria; Adem, Umut; Vakifahmetoglu, Cekdar: Electrical characteristics of low temperature densified barium titanate. Ceramics International, 46 (10, Part B), pp. 16670-16676, 2020, ISSN: 0272-8842. (Type: Journal Article | Abstract | Links | BibTeX) @article{KARACASULU202016670, title = {Electrical characteristics of low temperature densified barium titanate}, author = {Levent Karacasulu and Melike Tokkan and Mauro Bortolotti and Gloria Ischia and Umut Adem and Cekdar Vakifahmetoglu}, url = {https://www.sciencedirect.com/science/article/pii/S0272884220308889}, doi = {https://doi.org/10.1016/j.ceramint.2020.03.240}, issn = {0272-8842}, year = {2020}, date = {2020-01-01}, journal = {Ceramics International}, volume = {46}, number = {10, Part B}, pages = {16670-16676}, abstract = {A low temperature densification technique, i.e. reactive hydrothermal liquid-phase densification (rHLPD) was followed to obtain highly dense BaTiO3 components at temperatures ≤ 240 °C. The formed ceramics were characterized concerning not only the structural features but also the electrical properties. The increase of both reaction time and temperature resulted in enhanced densification of BaTiO3 components reaching about 90% of theoretical density. The presence of the tetragonal BaTiO3 was demonstrated by both XRD and TEM analysis. Despite the low reaction temperatures, the samples showed promising dielectric, ferroelectric and piezoelectric functionality without additional annealing. A broad dielectric peak was observed around 135 °C at the Curie temperature; saturated hysteresis loops and corresponding butterfly-shaped strain-electric field loops were obtained. BaTiO3 sample subjected to hydrothermal reaction at 240 °C for 72 h yielded a piezoelectric coefficient of 84 pC/N.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A low temperature densification technique, i.e. reactive hydrothermal liquid-phase densification (rHLPD) was followed to obtain highly dense BaTiO3 components at temperatures ≤ 240 °C. The formed ceramics were characterized concerning not only the structural features but also the electrical properties. The increase of both reaction time and temperature resulted in enhanced densification of BaTiO3 components reaching about 90% of theoretical density. The presence of the tetragonal BaTiO3 was demonstrated by both XRD and TEM analysis. Despite the low reaction temperatures, the samples showed promising dielectric, ferroelectric and piezoelectric functionality without additional annealing. A broad dielectric peak was observed around 135 °C at the Curie temperature; saturated hysteresis loops and corresponding butterfly-shaped strain-electric field loops were obtained. BaTiO3 sample subjected to hydrothermal reaction at 240 °C for 72 h yielded a piezoelectric coefficient of 84 pC/N. |
Vakifahmetoglu, Cekdar; Karacasulu, Levent: Cold sintering of ceramics and glasses: A review. Current Opinion in Solid State and Materials Science, 24 (1), pp. 100807, 2020, ISSN: 1359-0286. (Type: Journal Article | Abstract | Links | BibTeX) @article{VAKIFAHMETOGLU2020100807, title = {Cold sintering of ceramics and glasses: A review}, author = {Cekdar Vakifahmetoglu and Levent Karacasulu}, url = {https://www.sciencedirect.com/science/article/pii/S1359028620300048}, doi = {https://doi.org/10.1016/j.cossms.2020.100807}, issn = {1359-0286}, year = {2020}, date = {2020-01-01}, journal = {Current Opinion in Solid State and Materials Science}, volume = {24}, number = {1}, pages = {100807}, abstract = {Traditionally ceramic artifacts are processed at high temperatures (>1000 °C) by classical sintering techniques such as solid state, liquid phase and pressure-assisted sintering. Recently, inspired from the geology, novel sintering approaches that allow the densification of ceramic components at relatively low temperatures ≤400 °C have been proposed. While initial efforts for such low temperature densification concept were developed in the mid-70s, the topic has become increasingly prominent in the last decade. Currently, these low temperature methods can be classified into four main groups: (i) hydrothermal reaction sintering (HRS), (ii) hydrothermal hot pressing (HHP), (iii) pressure-assisted densification techniques: room-temperature densification (RTD), cold sintering (CS), warm press (WP), and finally no-pressure assisted method called (iv) reactive hydrothermal liquid phase densification (rHLPD). Above named techniques are commonly assisted by an aqueous solution used as either reactant or transient liquid phase to assist densification. Starting from the background in traditional sintering processes, this review aims to explore in depth the existing literature about low temperature densification approaches along with their advantages & disadvantages, and probable application areas.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Traditionally ceramic artifacts are processed at high temperatures (>1000 °C) by classical sintering techniques such as solid state, liquid phase and pressure-assisted sintering. Recently, inspired from the geology, novel sintering approaches that allow the densification of ceramic components at relatively low temperatures ≤400 °C have been proposed. While initial efforts for such low temperature densification concept were developed in the mid-70s, the topic has become increasingly prominent in the last decade. Currently, these low temperature methods can be classified into four main groups: (i) hydrothermal reaction sintering (HRS), (ii) hydrothermal hot pressing (HHP), (iii) pressure-assisted densification techniques: room-temperature densification (RTD), cold sintering (CS), warm press (WP), and finally no-pressure assisted method called (iv) reactive hydrothermal liquid phase densification (rHLPD). Above named techniques are commonly assisted by an aqueous solution used as either reactant or transient liquid phase to assist densification. Starting from the background in traditional sintering processes, this review aims to explore in depth the existing literature about low temperature densification approaches along with their advantages & disadvantages, and probable application areas. |
Lova, Paola; Olivieri, Marco; Surace, Alba; Topcu, Gokhan; Emirdag-Eanes, Mehtap; Demir, Mustafa M; Comoretto, Davide: Polymeric Planar Microcavities Doped with a Europium Complex. Crystals, 10 (4), 2020, ISSN: 2073-4352. (Type: Journal Article | Links | BibTeX) @article{cryst10040287, title = {Polymeric Planar Microcavities Doped with a Europium Complex}, author = {Paola Lova and Marco Olivieri and Alba Surace and Gokhan Topcu and Mehtap Emirdag-Eanes and Mustafa M Demir and Davide Comoretto}, url = {https://www.mdpi.com/2073-4352/10/4/287}, doi = {10.3390/cryst10040287}, issn = {2073-4352}, year = {2020}, date = {2020-01-01}, journal = {Crystals}, volume = {10}, number = {4}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Yildiz, Remziye; Ozen, Sercan; Sahin, Hasan; Akdogan, Yasar: The effect of DOPA hydroxyl groups on wet adhesion to polystyrene surface: An experimental and theoretical study. Materials Chemistry and Physics, 243 , pp. 122606, 2020, ISSN: 0254-0584. (Type: Journal Article | Abstract | Links | BibTeX) @article{YILDIZ2020122606, title = {The effect of DOPA hydroxyl groups on wet adhesion to polystyrene surface: An experimental and theoretical study}, author = {Remziye Yildiz and Sercan Ozen and Hasan Sahin and Yasar Akdogan}, url = {https://www.sciencedirect.com/science/article/pii/S0254058419314166}, doi = {https://doi.org/10.1016/j.matchemphys.2019.122606}, issn = {0254-0584}, year = {2020}, date = {2020-01-01}, journal = {Materials Chemistry and Physics}, volume = {243}, pages = {122606}, abstract = {Mussels wet adhesive performance has been arousing curiosity for a long time. It is found that 3,4-dihydroxyphenylalanine (DOPA) is responsible for adhesive properties of mussels. Despite a large body of research characterizing the interactions DOPA with hydrophilic surfaces, relatively few works have addressed the mechanism of interactions with hydrophobic surfaces. The benzene ring of DOPA is the main attributor to the adhesion on hydrophobic polystyrene (PS) surface. However, here we showed that two hydroxyl groups of catechol have also effects on wet adhesion. We studied wet adhesive properties of DOPA, tyrosine and phenylalanine functionalized PEG polymers, PEG-(N-Boc-l-DOPA)4, PEG-(N-Boc-l-Tyrosine)4, PEG-(N-Boc-l-Phenylalanine)4, on spin labeled PS nanobeads (SL-PS) by electron paramagnetic resonance (EPR) spectroscopy. Surface coverage ratio of SL-PS upon additions of PEG-(N-Boc-l-DOPA)4, PEG-(N-Boc-l-Tyrosine)4 and PEG-(N-Boc-l-Phenylalanine)4 showed that SL-PS was covered with 70%, 50% and 0%, respectively. This showed that spontaneous wet adhesion on PS increases with the number of amino acids hydroxyl groups. This is also supported with the density functional theory (DFT) energy calculations and ab-initio molecular dynamics (AIMD) simulations. In water, interactions between water molecules and hydroxyl groups on the catechol induce catechol adhesion via π-π stacking between the catechol and double styrene rings which were already tilted out with water.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mussels wet adhesive performance has been arousing curiosity for a long time. It is found that 3,4-dihydroxyphenylalanine (DOPA) is responsible for adhesive properties of mussels. Despite a large body of research characterizing the interactions DOPA with hydrophilic surfaces, relatively few works have addressed the mechanism of interactions with hydrophobic surfaces. The benzene ring of DOPA is the main attributor to the adhesion on hydrophobic polystyrene (PS) surface. However, here we showed that two hydroxyl groups of catechol have also effects on wet adhesion. We studied wet adhesive properties of DOPA, tyrosine and phenylalanine functionalized PEG polymers, PEG-(N-Boc-l-DOPA)4, PEG-(N-Boc-l-Tyrosine)4, PEG-(N-Boc-l-Phenylalanine)4, on spin labeled PS nanobeads (SL-PS) by electron paramagnetic resonance (EPR) spectroscopy. Surface coverage ratio of SL-PS upon additions of PEG-(N-Boc-l-DOPA)4, PEG-(N-Boc-l-Tyrosine)4 and PEG-(N-Boc-l-Phenylalanine)4 showed that SL-PS was covered with 70%, 50% and 0%, respectively. This showed that spontaneous wet adhesion on PS increases with the number of amino acids hydroxyl groups. This is also supported with the density functional theory (DFT) energy calculations and ab-initio molecular dynamics (AIMD) simulations. In water, interactions between water molecules and hydroxyl groups on the catechol induce catechol adhesion via π-π stacking between the catechol and double styrene rings which were already tilted out with water. |
Sevim, K; Sevinçli, H: Structural, electronic, and magnetic properties of point defects in polyaniline (C3N) and graphene monolayers: A comparative study. Journal of Applied Physics, 127 (19), pp. 195102, 2020. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/5.0004373, title = {Structural, electronic, and magnetic properties of point defects in polyaniline (C3N) and graphene monolayers: A comparative study}, author = {K Sevim and H Sevinçli}, url = {https://doi.org/10.1063/5.0004373}, doi = {10.1063/5.0004373}, year = {2020}, date = {2020-01-01}, journal = {Journal of Applied Physics}, volume = {127}, number = {19}, pages = {195102}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Levanyuk, Arkady P; Misirlioglu, Burc I; Okatan, Baris M: Landau, Ginzburg, Devonshire and others. Ferroelectrics, 569 (1), pp. 310-323, 2020. (Type: Journal Article | Links | BibTeX) @article{doi:10.1080/00150193.2020.1822684, title = {Landau, Ginzburg, Devonshire and others}, author = {Arkady P Levanyuk and Burc I Misirlioglu and Baris M Okatan}, url = {https://doi.org/10.1080/00150193.2020.1822684}, doi = {10.1080/00150193.2020.1822684}, year = {2020}, date = {2020-01-01}, journal = {Ferroelectrics}, volume = {569}, number = {1}, pages = {310-323}, publisher = {Taylor & Francis}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sozer, Sumeyra Cigdem; Egesoy, Tugce Ozmen; Basol, Merve; Cakan-Akdogan, Gulcin; Akdogan, Yasar: A simple desolvation method for production of cationic albumin nanoparticles with improved drug loading and cell uptake. Journal of Drug Delivery Science and Technology, 60 , pp. 101931, 2020, ISSN: 1773-2247. (Type: Journal Article | Abstract | Links | BibTeX) @article{SOZER2020101931, title = {A simple desolvation method for production of cationic albumin nanoparticles with improved drug loading and cell uptake}, author = {Sumeyra Cigdem Sozer and Tugce Ozmen Egesoy and Merve Basol and Gulcin Cakan-Akdogan and Yasar Akdogan}, url = {https://www.sciencedirect.com/science/article/pii/S177322472031220X}, doi = {https://doi.org/10.1016/j.jddst.2020.101931}, issn = {1773-2247}, year = {2020}, date = {2020-01-01}, journal = {Journal of Drug Delivery Science and Technology}, volume = {60}, pages = {101931}, abstract = {The transport protein albumin has been used as a drug nanocarrier for a long time due to its versatility. Albumin is negatively charged at physiological conditions limiting its anionic drug loading capacity. However, loading of anionic drugs in the albumin nanoparticles (NPs), can be facilitated by albumin cationization. Here, we postulate a simple desolvation method for preparation of cationic albumin NPs with improved anionic drug loading. First, bovine serum albumin was cationized with ethylenediamine. Next, salicylic acid (SA) was added to the cationic bovine serum albumin (cBSA) solution prior to the desolvation. Among different desolvating agents tested, acetonitrile allowed the highest nanoparticle formation yield. The SEM analyses showed that the average size of cBSA NPs decreased from ~200 nm to ~100 nm upon SA loading. Moreover, the drug loading capacity of cBSA NPs was found to increase ~2 fold, and drug release was slower compared to BSA NPs. Finally, a significant increase in cellular uptake of cBSA NPs compared to that of native BSA NPs showed the potential for improved drug delivery.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The transport protein albumin has been used as a drug nanocarrier for a long time due to its versatility. Albumin is negatively charged at physiological conditions limiting its anionic drug loading capacity. However, loading of anionic drugs in the albumin nanoparticles (NPs), can be facilitated by albumin cationization. Here, we postulate a simple desolvation method for preparation of cationic albumin NPs with improved anionic drug loading. First, bovine serum albumin was cationized with ethylenediamine. Next, salicylic acid (SA) was added to the cationic bovine serum albumin (cBSA) solution prior to the desolvation. Among different desolvating agents tested, acetonitrile allowed the highest nanoparticle formation yield. The SEM analyses showed that the average size of cBSA NPs decreased from ~200 nm to ~100 nm upon SA loading. Moreover, the drug loading capacity of cBSA NPs was found to increase ~2 fold, and drug release was slower compared to BSA NPs. Finally, a significant increase in cellular uptake of cBSA NPs compared to that of native BSA NPs showed the potential for improved drug delivery. |
Santhosh, Balanand; Vakifahmetoglu, Cekdar; Ionescu, Emanuel; Reitz, Andreas; Albert, Barbara; Sorarù, Gian Domenico: Processing and thermal characterization of polymer derived SiCN(O) and SiOC reticulated foams. Ceramics International, 46 (5), pp. 5594-5601, 2020, ISSN: 0272-8842. (Type: Journal Article | Abstract | Links | BibTeX) @article{SANTHOSH20205594, title = {Processing and thermal characterization of polymer derived SiCN(O) and SiOC reticulated foams}, author = {Balanand Santhosh and Cekdar Vakifahmetoglu and Emanuel Ionescu and Andreas Reitz and Barbara Albert and Gian Domenico Sorarù}, url = {https://www.sciencedirect.com/science/article/pii/S0272884219331815}, doi = {https://doi.org/10.1016/j.ceramint.2019.11.003}, issn = {0272-8842}, year = {2020}, date = {2020-01-01}, journal = {Ceramics International}, volume = {46}, number = {5}, pages = {5594-5601}, abstract = {Highly porous polymer-derived SiCN(O) and SiOC ceramics with low thermal conductivity were developed by replicating polyurethane (PU) foams. The PU templates were impregnated with polysilazane or polysiloxane precursor, followed by pyrolysis at different temperatures (1200 °C - 1500 °C) yielding SiCN(O) or SiOC ceramic foams, respectively. The swelling and cross-linking behavior of the used precursors had a significant impact on the morphology of the prepared foams. The samples had bulk densities ranging from 0.03 g.cm-3 to 0.56 g.cm-3 and a total porosity in the range from 75 to 98 vol%. Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) were employed to follow the structural evolution together with morphological characterization by scanning electron microscopy (SEM). The obtained ceramics were thermally stable up to 1400 °C, and the linear thermal expansion coefficient values of the porous SiCN(O) and SiOC components in the temperature range from 30 to 850 °C were found to be ~1.72 x 10-6.K-1 and ~1.93 x 10-6.K-1, respectively. Thermal conductivity (λ) as low as 0.03 W.m-1 K-1 was measured for the SiCN(O) and SiOC foams at room temperature (RT). The λ of the ceramic struts were also assessed by using the Gibson-Ashby model and estimated to be 2.1 W.m-1 K-1 for SiCN(O), and 1.8 W.m-1 K-1 for SiOC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Highly porous polymer-derived SiCN(O) and SiOC ceramics with low thermal conductivity were developed by replicating polyurethane (PU) foams. The PU templates were impregnated with polysilazane or polysiloxane precursor, followed by pyrolysis at different temperatures (1200 °C - 1500 °C) yielding SiCN(O) or SiOC ceramic foams, respectively. The swelling and cross-linking behavior of the used precursors had a significant impact on the morphology of the prepared foams. The samples had bulk densities ranging from 0.03 g.cm-3 to 0.56 g.cm-3 and a total porosity in the range from 75 to 98 vol%. Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) were employed to follow the structural evolution together with morphological characterization by scanning electron microscopy (SEM). The obtained ceramics were thermally stable up to 1400 °C, and the linear thermal expansion coefficient values of the porous SiCN(O) and SiOC components in the temperature range from 30 to 850 °C were found to be ~1.72 x 10-6.K-1 and ~1.93 x 10-6.K-1, respectively. Thermal conductivity (λ) as low as 0.03 W.m-1 K-1 was measured for the SiCN(O) and SiOC foams at room temperature (RT). The λ of the ceramic struts were also assessed by using the Gibson-Ashby model and estimated to be 2.1 W.m-1 K-1 for SiCN(O), and 1.8 W.m-1 K-1 for SiOC. |
Mensur-Alkoy, Ebru; Okatan, Baris M; Aydin, Ecem; Kilic, Yusuf; Misirlioglu, Burc I; Alkoy, Sedat: Effect of texture on the electrical and electrocaloric properties of 0.90Pb(Mg1/3Nb2/3)O3–0.10PbTiO3 relaxor ceramics. Journal of Applied Physics, 128 (8), pp. 084102, 2020. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/5.0003296, title = {Effect of texture on the electrical and electrocaloric properties of 0.90Pb(Mg1/3Nb2/3)O3–0.10PbTiO3 relaxor ceramics}, author = {Ebru Mensur-Alkoy and Baris M Okatan and Ecem Aydin and Yusuf Kilic and Burc I Misirlioglu and Sedat Alkoy}, url = {https://doi.org/10.1063/5.0003296}, doi = {10.1063/5.0003296}, year = {2020}, date = {2020-01-01}, journal = {Journal of Applied Physics}, volume = {128}, number = {8}, pages = {084102}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Vakifahmetoglu, Cekdar; Semerci, Tugce; Soraru, Gian Domenico: Closed porosity ceramics and glasses. Journal of the American Ceramic Society, 103 (5), pp. 2941-2969, 2020. (Type: Journal Article | Abstract | Links | BibTeX) @article{https://doi.org/10.1111/jace.16934, title = {Closed porosity ceramics and glasses}, author = {Cekdar Vakifahmetoglu and Tugce Semerci and Gian Domenico Soraru}, url = {https://ceramics.onlinelibrary.wiley.com/doi/abs/10.1111/jace.16934}, doi = {https://doi.org/10.1111/jace.16934}, year = {2020}, date = {2020-01-01}, journal = {Journal of the American Ceramic Society}, volume = {103}, number = {5}, pages = {2941-2969}, abstract = {Abstract In the last three decades, considerable effort has been devoted to obtain both open and closed porosity ceramics & glasses in order to benefit from unique combination of properties such as mechanical strength, thermal and chemical stability at low-relative density. Most of these investigations were directed to the production and the analysis of the properties for open porosity materials, and regrettably quite a few compositions and manufacturing methods were documented for closed porosity ceramics & glasses in the scientific literature so far. This review focuses on the processing strategies, the properties and the applications of closed porosity ceramics & glasses with total porosity higher than 25%. The ones below such level are intentionally left out and the paper is set out to demonstrate the porous components with deliberately generated closed pores/cells. The processing strategies are categorized into five different groups, namely sacrificial templating, high-temperature bonding of hollow structures, casting, direct foaming, and emulsions. The principles underlying these methods are given, with particular emphasis on the critical issues that affect the pore characteristics, mechanical, thermal and electrical properties of the produced components.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract In the last three decades, considerable effort has been devoted to obtain both open and closed porosity ceramics & glasses in order to benefit from unique combination of properties such as mechanical strength, thermal and chemical stability at low-relative density. Most of these investigations were directed to the production and the analysis of the properties for open porosity materials, and regrettably quite a few compositions and manufacturing methods were documented for closed porosity ceramics & glasses in the scientific literature so far. This review focuses on the processing strategies, the properties and the applications of closed porosity ceramics & glasses with total porosity higher than 25%. The ones below such level are intentionally left out and the paper is set out to demonstrate the porous components with deliberately generated closed pores/cells. The processing strategies are categorized into five different groups, namely sacrificial templating, high-temperature bonding of hollow structures, casting, direct foaming, and emulsions. The principles underlying these methods are given, with particular emphasis on the critical issues that affect the pore characteristics, mechanical, thermal and electrical properties of the produced components. |
Arica, Tugce A; Topcu, Gokhan; Pala, Atamert; Demir, Mustafa M: Experimental apparatus for simultaneous measurement of triboelectricity and triboluminescence. Measurement, 152 , pp. 107316, 2020, ISSN: 0263-2241. (Type: Journal Article | Abstract | Links | BibTeX) @article{ARICA2020107316, title = {Experimental apparatus for simultaneous measurement of triboelectricity and triboluminescence}, author = {Tugce A Arica and Gokhan Topcu and Atamert Pala and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S0263224119311807}, doi = {https://doi.org/10.1016/j.measurement.2019.107316}, issn = {0263-2241}, year = {2020}, date = {2020-01-01}, journal = {Measurement}, volume = {152}, pages = {107316}, abstract = {Triboelectricity is a phenomenon caused by the accumulation of opposite electric charges on the surfaces of two different materials as a result of contact with each other. The phenomenon of emitting cold light when the material is subjected to physical deformation is called triboluminescence. This paper presents an experimental apparatus that allows simultaneous measurement of both triboelectricity and triboluminescence of a model composite system based on poly (vinylidene fluoride) (PVDF) and europium tetrakis (dibenzoylmethide) triethylammonium (EuD4TEA). While the former component was studied in contact-separation mode giving triboelectricity, the latter emits triboluminescence upon application of mechanical impact. The device was operated at varying range of frequencies from 0.5 to 4.8 Hz and the force in the range of 5.4–9.5 N.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Triboelectricity is a phenomenon caused by the accumulation of opposite electric charges on the surfaces of two different materials as a result of contact with each other. The phenomenon of emitting cold light when the material is subjected to physical deformation is called triboluminescence. This paper presents an experimental apparatus that allows simultaneous measurement of both triboelectricity and triboluminescence of a model composite system based on poly (vinylidene fluoride) (PVDF) and europium tetrakis (dibenzoylmethide) triethylammonium (EuD4TEA). While the former component was studied in contact-separation mode giving triboelectricity, the latter emits triboluminescence upon application of mechanical impact. The device was operated at varying range of frequencies from 0.5 to 4.8 Hz and the force in the range of 5.4–9.5 N. |
Yuce, Hurriyet; Guner, Tugrul; Dartar, Suay; Kaya, Beraat U; Emrullahoglu, Mustafa; Demir, Mustafa M: BODIPY-based organic color conversion layers for WLEDs. Dyes and Pigments, 173 , pp. 107932, 2020, ISSN: 0143-7208. (Type: Journal Article | Abstract | Links | BibTeX) @article{YUCE2020107932, title = {BODIPY-based organic color conversion layers for WLEDs}, author = {Hurriyet Yuce and Tugrul Guner and Suay Dartar and Beraat U Kaya and Mustafa Emrullahoglu and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S0143720819302864}, doi = {https://doi.org/10.1016/j.dyepig.2019.107932}, issn = {0143-7208}, year = {2020}, date = {2020-01-01}, journal = {Dyes and Pigments}, volume = {173}, pages = {107932}, abstract = {The usage of organic dyes in phosphor conversion layer of WLED is an attractive approach since they have high molar extinction coefficient and photostability. Various types of organic pigments have been employed for this purpose such as BODIPY, perylene diimide, Rhodamine B, pyrene, Nile red, etc. Among those, BODIPY-based organic dyes appear to be promising candidate for white light generation. In this work, for the first time, red and green emitting BODIPY-based organic molecules have been used as colour conversion layer. These molecules were associated with PMMA in DMF solution and the resulting solution was subjected to electrospinning. Colorful electrospun mats were embedded into PDMS matrix and their free-standing PDMS composite films were used as color conversion layers over blue LED to produce white light such that CRI of 95 and CCT of 4200 K was achieved. These values show that BODIPY-based organic molecules containing fiber composites are promising candidates to be used as color conversion layers for white light applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The usage of organic dyes in phosphor conversion layer of WLED is an attractive approach since they have high molar extinction coefficient and photostability. Various types of organic pigments have been employed for this purpose such as BODIPY, perylene diimide, Rhodamine B, pyrene, Nile red, etc. Among those, BODIPY-based organic dyes appear to be promising candidate for white light generation. In this work, for the first time, red and green emitting BODIPY-based organic molecules have been used as colour conversion layer. These molecules were associated with PMMA in DMF solution and the resulting solution was subjected to electrospinning. Colorful electrospun mats were embedded into PDMS matrix and their free-standing PDMS composite films were used as color conversion layers over blue LED to produce white light such that CRI of 95 and CCT of 4200 K was achieved. These values show that BODIPY-based organic molecules containing fiber composites are promising candidates to be used as color conversion layers for white light applications. |
Şanlı, Keriman; Adem, Umut: Electrocaloric properties of Ba0.8Sr0.2Ti1-xZrxO3 (0≤x≤0.1) system: The balance between the nature of the phase transition and phase coexistence. Ceramics International, 46 (2), pp. 2213-2219, 2020, ISSN: 0272-8842. (Type: Journal Article | Abstract | Links | BibTeX) @article{SANLI20202213, title = {Electrocaloric properties of Ba0.8Sr0.2Ti1-xZrxO3 (0≤x≤0.1) system: The balance between the nature of the phase transition and phase coexistence}, author = {Keriman Şanlı and Umut Adem}, url = {https://www.sciencedirect.com/science/article/pii/S0272884219327439}, doi = {https://doi.org/10.1016/j.ceramint.2019.09.206}, issn = {0272-8842}, year = {2020}, date = {2020-01-01}, journal = {Ceramics International}, volume = {46}, number = {2}, pages = {2213-2219}, abstract = {We investigate the electrocaloric effect of Ba0.8Sr0.2Ti1-xZrxO3 (0 ≤ x ≤ 0.1) system by comparing the electrocaloric temperature change (ΔT) of different compositions belonging to the different regions of the phase diagram. We show that as the amount of Zr increases, electrocaloric temperature change initially decreases as the phase transition gets diffuse then increases again as the composition of the samples are located closer to the critical point where different ferroelectric phases coexist. Since the critical point is reached at relatively low Zr substitution levels (i.e. around x = 0.07), the phase transition doesn't get too diffuse and thefore the compositions between x = 0 and x = 0.10 (which contains higher Zr than the critical point composition) have comparable ΔT values. Electrocaloric efficiency of these compositions (x = 0.03, 0.05 and 0.07) is around 0.20 K mm/kV at 20 kV/cm. We discuss the results in terms of the balance between the nature of the phase transition and proximity to the critical point, based on the phase diagram.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate the electrocaloric effect of Ba0.8Sr0.2Ti1-xZrxO3 (0 ≤ x ≤ 0.1) system by comparing the electrocaloric temperature change (ΔT) of different compositions belonging to the different regions of the phase diagram. We show that as the amount of Zr increases, electrocaloric temperature change initially decreases as the phase transition gets diffuse then increases again as the composition of the samples are located closer to the critical point where different ferroelectric phases coexist. Since the critical point is reached at relatively low Zr substitution levels (i.e. around x = 0.07), the phase transition doesn't get too diffuse and thefore the compositions between x = 0 and x = 0.10 (which contains higher Zr than the critical point composition) have comparable ΔT values. Electrocaloric efficiency of these compositions (x = 0.03, 0.05 and 0.07) is around 0.20 K mm/kV at 20 kV/cm. We discuss the results in terms of the balance between the nature of the phase transition and proximity to the critical point, based on the phase diagram. |
Kurnia, Arif; Emriadi, ; Mufti, Nandang; Zulhadjri, ; Adem, Umut: Electrocaloric effect of alkali co-substituted Sr0.6Ba0.4Nb2O6 ceramics. Journal of Alloys and Compounds, 844 , pp. 156132, 2020, ISSN: 0925-8388. (Type: Journal Article | Abstract | Links | BibTeX) @article{KURNIA2020156132, title = {Electrocaloric effect of alkali co-substituted Sr0.6Ba0.4Nb2O6 ceramics}, author = {Arif Kurnia and Emriadi and Nandang Mufti and Zulhadjri and Umut Adem}, url = {https://www.sciencedirect.com/science/article/pii/S0925838820324968}, doi = {https://doi.org/10.1016/j.jallcom.2020.156132}, issn = {0925-8388}, year = {2020}, date = {2020-01-01}, journal = {Journal of Alloys and Compounds}, volume = {844}, pages = {156132}, abstract = {We have investigated the electrocaloric properties of K+ and Na+ co-substituted Sr0.6Ba0.4Nb2O6 (SBN) ceramics using the indirect method. Tetragonal tungsten bronze (K0.5Na0.5)2x(Sr0.6Ba0.4)5-xNb10O30 (KNSBN) with x = 0.24 was synthesized using dual-step sintering. Despite the low amount, K+ and Na+ co-substitution resulted in normal ferroelectric behaviour, showing no significant shift in the dielectric maximum temperature of 111 °C with increasing frequency. Maximum electrocaloric temperature change (ΔT) of 0.3 K was observed at an electric field of 30 kV/cm (ΔE) yielding the largest electrocaloric responsivity (ΔT/ΔE) among SBN based ceramics. This relatively large value is in agreement with the larger pyroelectric coefficient of KNSBN compared to SBN based ceramics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We have investigated the electrocaloric properties of K+ and Na+ co-substituted Sr0.6Ba0.4Nb2O6 (SBN) ceramics using the indirect method. Tetragonal tungsten bronze (K0.5Na0.5)2x(Sr0.6Ba0.4)5-xNb10O30 (KNSBN) with x = 0.24 was synthesized using dual-step sintering. Despite the low amount, K+ and Na+ co-substitution resulted in normal ferroelectric behaviour, showing no significant shift in the dielectric maximum temperature of 111 °C with increasing frequency. Maximum electrocaloric temperature change (ΔT) of 0.3 K was observed at an electric field of 30 kV/cm (ΔE) yielding the largest electrocaloric responsivity (ΔT/ΔE) among SBN based ceramics. This relatively large value is in agreement with the larger pyroelectric coefficient of KNSBN compared to SBN based ceramics. |
2019 |
Guvenc, Meric C; Yalcinkaya, Yenal; Ozen, Sercan; Sahin, Hasan; Demir, Mustafa M: Gd3+-Doped $alpha$-CsPbI3 Nanocrystals with Better Phase Stability and Optical Properties. The Journal of Physical Chemistry C, 123 (40), pp. 24865-24872, 2019, ISSN: 1932-7447. (Type: Journal Article | Links | BibTeX) @article{Guvenc2019b, title = {Gd3+-Doped $alpha$-CsPbI3 Nanocrystals with Better Phase Stability and Optical Properties}, author = {Meric C Guvenc and Yenal Yalcinkaya and Sercan Ozen and Hasan Sahin and Mustafa M Demir}, url = {https://doi.org/10.1021/acs.jpcc.9b05969}, doi = {10.1021/acs.jpcc.9b05969}, issn = {1932-7447}, year = {2019}, date = {2019-10-10}, journal = {The Journal of Physical Chemistry C}, volume = {123}, number = {40}, pages = {24865-24872}, publisher = {American Chemical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Ozcan, Mehmet; Ozen, Sercan; Topcu, Gokhan; Demir, Mustafa M; Sahin, Hasan: Color-Tunable All-Inorganic CsPbBr3 Perovskites Nanoplatelet Films for Photovoltaic Devices. ACS Appl. Nano Mater., 2 (8), pp. 5149-5155, 2019. (Type: Journal Article | Links | BibTeX) @article{Ozcan2019, title = {Color-Tunable All-Inorganic CsPbBr3 Perovskites Nanoplatelet Films for Photovoltaic Devices}, author = {Mehmet Ozcan and Sercan Ozen and Gokhan Topcu and Mustafa M Demir and Hasan Sahin}, url = {https://doi.org/10.1021/acsanm.9b01035}, doi = {10.1021/acsanm.9b01035}, year = {2019}, date = {2019-08-23}, journal = {ACS Appl. Nano Mater.}, volume = {2}, number = {8}, pages = {5149-5155}, publisher = {American Chemical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Gökbulut, Belįs; ç, Arda Inan; Topcu, Gokhan; ç, Se; Ozcelik, Serdar; Demir, Mustafa M; Inci, Naci M: Enhanced Spontaneous Emission Rate in a Low-Q Hybrid Photonic-Plasmonic Nanoresonator. The Journal of Physical Chemistry C, 123 (32), pp. 19862-19870, 2019, ISSN: 1932-7447. (Type: Journal Article | Links | BibTeX) @article{Gökbulut2019, title = {Enhanced Spontaneous Emission Rate in a Low-Q Hybrid Photonic-Plasmonic Nanoresonator}, author = {Belįs Gökbulut and Arda Inan{ç} and Gokhan Topcu and Se{ç}il S Unluturk and Serdar Ozcelik and Mustafa M Demir and Naci M Inci}, url = {https://doi.org/10.1021/acs.jpcc.9b05289}, doi = {10.1021/acs.jpcc.9b05289}, issn = {1932-7447}, year = {2019}, date = {2019-08-15}, journal = {The Journal of Physical Chemistry C}, volume = {123}, number = {32}, pages = {19862-19870}, publisher = {American Chemical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Özbal, G; Senger, R T; Sevik, C; mbox ç}else çfi{, Sevinifmmode H: Ballistic thermoelectric properties of monolayer semiconducting transition metal dichalcogenides and oxides. Phys. Rev. B, 100 , pp. 085415, 2019. (Type: Journal Article | Links | BibTeX) @article{PhysRevB.100.085415, title = {Ballistic thermoelectric properties of monolayer semiconducting transition metal dichalcogenides and oxides}, author = {G Özbal and R T Senger and C Sevik and H Sevinifmmode mbox{ç}else çfi{}li}, url = {https://link.aps.org/doi/10.1103/PhysRevB.100.085415}, doi = {10.1103/PhysRevB.100.085415}, year = {2019}, date = {2019-08-01}, journal = {Phys. Rev. B}, volume = {100}, pages = {085415}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sevinçli, H; Roche, S; Cuniberti, G; Brandbyge, M; Gutierrez, R; Sandonas, Medrano L: Green function, quasi-classical Langevin and Kubo–Greenwood methods in quantum thermal transport. Journal of Physics: Condensed Matter, 31 (27), pp. 273003, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{sevincli2019, title = {Green function, quasi-classical Langevin and Kubo–Greenwood methods in quantum thermal transport}, author = {H Sevinçli and S Roche and G Cuniberti and M Brandbyge and R Gutierrez and Medrano L Sandonas}, url = {https://doi.org/10.1088%2F1361-648x%2Fab119a}, doi = {10.1088/1361-648x/ab119a}, year = {2019}, date = {2019-04-01}, journal = {Journal of Physics: Condensed Matter}, volume = {31}, number = {27}, pages = {273003}, publisher = {IOP Publishing}, abstract = {With the advances in fabrication of materials with feature sizes at the order of nanometers, it has been possible to alter their thermal transport properties dramatically. Miniaturization of device size increases the power density in general, hence faster electronics require better thermal transport, whereas better thermoelectric applications require the opposite. Such diverse needs bring new challenges for material design. Shrinkage of length scales has also changed the experimental and theoretical methods to study thermal transport. Unsurprisingly, novel approaches have emerged to control phonon flow. Besides, ever increasing computational power is another driving force for developing new computational methods. In this review, we discuss three methods developed for computing vibrational thermal transport properties of nano-structured systems, namely Green function, quasi-classical Langevin, and Kubo–Green methods. The Green function methods are explained using both nonequilibrium expressions and the Landauer-type formula. The partitioning scheme, decimation techniques and surface Green functions are reviewed, and a simple model for reservoir Green functions is shown. The expressions for the Kubo–Greenwood method are derived, and Lanczos tridiagonalization, continued fraction and Chebyshev polynomial expansion methods are discussed. Additionally, the quasi-classical Langevin approach, which is useful for incorporating phonon–phonon and other scatterings is summarized.}, keywords = {}, pubstate = {published}, tppubtype = {article} } With the advances in fabrication of materials with feature sizes at the order of nanometers, it has been possible to alter their thermal transport properties dramatically. Miniaturization of device size increases the power density in general, hence faster electronics require better thermal transport, whereas better thermoelectric applications require the opposite. Such diverse needs bring new challenges for material design. Shrinkage of length scales has also changed the experimental and theoretical methods to study thermal transport. Unsurprisingly, novel approaches have emerged to control phonon flow. Besides, ever increasing computational power is another driving force for developing new computational methods. In this review, we discuss three methods developed for computing vibrational thermal transport properties of nano-structured systems, namely Green function, quasi-classical Langevin, and Kubo–Green methods. The Green function methods are explained using both nonequilibrium expressions and the Landauer-type formula. The partitioning scheme, decimation techniques and surface Green functions are reviewed, and a simple model for reservoir Green functions is shown. The expressions for the Kubo–Greenwood method are derived, and Lanczos tridiagonalization, continued fraction and Chebyshev polynomial expansion methods are discussed. Additionally, the quasi-classical Langevin approach, which is useful for incorporating phonon–phonon and other scatterings is summarized. |
Yuce, Hurriyet; Guner, Tugrul; Balci, Sinan; Demir, Mustafa M: Phosphor-based white LED by various glassy particles: control over luminous efficiency. Opt. Lett., 44 (3), pp. 479–482, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{yuce19, title = {Phosphor-based white LED by various glassy particles: control over luminous efficiency}, author = {Hurriyet Yuce and Tugrul Guner and Sinan Balci and Mustafa M Demir}, url = {http://ol.osa.org/abstract.cfm?URI=ol-44-3-479}, doi = {10.1364/OL.44.000479}, year = {2019}, date = {2019-02-01}, journal = {Opt. Lett.}, volume = {44}, number = {3}, pages = {479--482}, publisher = {OSA}, abstract = {Generating white light through a mainstream remote phosphor design suffers from phosphor conversion efficiency loss due to a backscattering of light. Such a loss also reduces luminous efficiency of the resulting white light. To overcome this issue, various glassy scatterers with different morphologies such as glass bubbles, glass beads, and nanosized silica particles were employed as scatterers, together with a fixed amount of yellow phosphor (YAG:Ce3$+$) and a poly(dimethylsiloxane) (PDMS) matrix. In addition, the simulation of the system validates the rigorous multiple scattering of the incoming light most probably due to refractive index mismatch between the glass bubbles and surrounding PDMS matrix along with the internal reflections.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Generating white light through a mainstream remote phosphor design suffers from phosphor conversion efficiency loss due to a backscattering of light. Such a loss also reduces luminous efficiency of the resulting white light. To overcome this issue, various glassy scatterers with different morphologies such as glass bubbles, glass beads, and nanosized silica particles were employed as scatterers, together with a fixed amount of yellow phosphor (YAG:Ce3$+$) and a poly(dimethylsiloxane) (PDMS) matrix. In addition, the simulation of the system validates the rigorous multiple scattering of the incoming light most probably due to refractive index mismatch between the glass bubbles and surrounding PDMS matrix along with the internal reflections. |
Gökbulut, Belkıs; Inanç, Arda; Topcu, Gokhan; Guner, Tugrul; Demir, Mustafa M; Inci, Naci M: Enhancement of the Spontaneous Emission Rate of Perovskite Nanowires Coupled into Cylindrical Hollow Nanocavities Formed on the Surface of Polystyrene Microfibers. The Journal of Physical Chemistry C, 123 (14), pp. 9343-9351, 2019. (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.jpcc.8b12114, title = {Enhancement of the Spontaneous Emission Rate of Perovskite Nanowires Coupled into Cylindrical Hollow Nanocavities Formed on the Surface of Polystyrene Microfibers}, author = {Belkıs Gökbulut and Arda Inanç and Gokhan Topcu and Tugrul Guner and Mustafa M Demir and Naci M Inci}, url = {https://doi.org/10.1021/acs.jpcc.8b12114}, doi = {10.1021/acs.jpcc.8b12114}, year = {2019}, date = {2019-01-01}, journal = {The Journal of Physical Chemistry C}, volume = {123}, number = {14}, pages = {9343-9351}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Satilmis, Bekir; Isık, Tuğba; Demir, Mustafa M; Uyar, Tamer: Amidoxime functionalized Polymers of Intrinsic Microporosity (PIM-1) electrospun ultrafine fibers for rapid removal of uranyl ions from water. Applied Surface Science, 467-468 , pp. 648 - 657, 2019, ISSN: 0169-4332. (Type: Journal Article | Abstract | Links | BibTeX) @article{satilmis2019648, title = {Amidoxime functionalized Polymers of Intrinsic Microporosity (PIM-1) electrospun ultrafine fibers for rapid removal of uranyl ions from water}, author = {Bekir Satilmis and Tuğba Isık and Mustafa M Demir and Tamer Uyar}, url = {http://www.sciencedirect.com/science/article/pii/S0169433218329908}, doi = {https://doi.org/10.1016/j.apsusc.2018.10.210}, issn = {0169-4332}, year = {2019}, date = {2019-01-01}, journal = {Applied Surface Science}, volume = {467-468}, pages = {648 - 657}, abstract = {The Polymers of Intrinsic Microporosity (PIM-1) is considered as one of the most promising polymer candidates for adsorption applications owing to its high surface area and the ability to tailor the functionality for the targeted species. This study reports a facile method for the preparation of amidoxime functionalized PIM-1 fibrous membrane (AF-PIM-FM) by electrospinning technique and its practical use for the extraction of U(VI) ions from aqueous systems via column sorption under continuous flow. Fibrous membrane form of amidoxime functionalized PIM-1 (AF-PIM-FM) was prepared by electrospinning method owing to its excellent processability in dimethylformamide. Bead-free and uniform fibers were obtained as confirmed by SEM imaging and average fiber diameter was 1.69 ± 0.34 μm for AF-PIM-FM. In addition, electrospun PIM-1 fibrous membrane (PIM-FM) was prepared as a control group. Structural and thermal characterization of powder and membrane forms of the materials were performed using FT-IR, 1H NMR, XPS, Elemental analyses, TGA, and DSC. The porosity of the samples was measured by N2 sorption isotherms confirming amidoxime PIM-1 still maintain their porosity after functionalization. Amidoxime functionality along with membrane structure makes AF-PIM-FM a promising material for uranyl adsorption. First, a comparison between powder and membrane form of amidoxime functionalized PIM-1 was investigated using batch adsorption process. Although membrane form has shown slightly lower adsorption performance in the batch adsorption process, the advantage of using the membrane in column adsorption processes makes membrane form more feasible for real applications. In addition, amidoxime modification enhanced the uranium adsorption ability of PIM-FM up to 20 times. The effect of initial concentration and pH were investigated along with regeneration of the adsorbents. AF-PIM-FM was successfully used for five adsorption-desorption cycles without having any damage on the fibrous structure.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Polymers of Intrinsic Microporosity (PIM-1) is considered as one of the most promising polymer candidates for adsorption applications owing to its high surface area and the ability to tailor the functionality for the targeted species. This study reports a facile method for the preparation of amidoxime functionalized PIM-1 fibrous membrane (AF-PIM-FM) by electrospinning technique and its practical use for the extraction of U(VI) ions from aqueous systems via column sorption under continuous flow. Fibrous membrane form of amidoxime functionalized PIM-1 (AF-PIM-FM) was prepared by electrospinning method owing to its excellent processability in dimethylformamide. Bead-free and uniform fibers were obtained as confirmed by SEM imaging and average fiber diameter was 1.69 ± 0.34 μm for AF-PIM-FM. In addition, electrospun PIM-1 fibrous membrane (PIM-FM) was prepared as a control group. Structural and thermal characterization of powder and membrane forms of the materials were performed using FT-IR, 1H NMR, XPS, Elemental analyses, TGA, and DSC. The porosity of the samples was measured by N2 sorption isotherms confirming amidoxime PIM-1 still maintain their porosity after functionalization. Amidoxime functionality along with membrane structure makes AF-PIM-FM a promising material for uranyl adsorption. First, a comparison between powder and membrane form of amidoxime functionalized PIM-1 was investigated using batch adsorption process. Although membrane form has shown slightly lower adsorption performance in the batch adsorption process, the advantage of using the membrane in column adsorption processes makes membrane form more feasible for real applications. In addition, amidoxime modification enhanced the uranium adsorption ability of PIM-FM up to 20 times. The effect of initial concentration and pH were investigated along with regeneration of the adsorbents. AF-PIM-FM was successfully used for five adsorption-desorption cycles without having any damage on the fibrous structure. |
Topçu, Gökhan; Çelik, Aslı; Kandemir, Ali; Baba, Alper; Şahin, Hasan; Demir, Mustafa M: Increasing solubility of metal silicates by mixed polymeric antiscalants. Geothermics, 77 , pp. 106 - 114, 2019, ISSN: 0375-6505. (Type: Journal Article | Abstract | Links | BibTeX) @article{topcu2019106, title = {Increasing solubility of metal silicates by mixed polymeric antiscalants}, author = {Gökhan Topçu and Aslı Çelik and Ali Kandemir and Alper Baba and Hasan Şahin and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S0375650518300865}, doi = {https://doi.org/10.1016/j.geothermics.2018.09.002}, issn = {0375-6505}, year = {2019}, date = {2019-01-01}, journal = {Geothermics}, volume = {77}, pages = {106 - 114}, abstract = {The increase of silicate solubility is a big challenge for both hot and cold water because it reduces the deposition of metal silicates frequently observed in such systems and causes operational obstacles. The deposition of silicate coats the inner surface of the pipelines in an uncontrolled manner and reduces the harvesting of energy from brines. In this work, the solubility performance of two commercial water-soluble polymeric agents (poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA)) of various molecular weights employing dosage from 25 to 100 mg/L was examined. Along with dispersant-type antiscalant, poly(acrylamide) (PAM), poly(vinylsulfonic acid, sodium salt) (PVSA), and poly(vinylphosphonic acid) (PVPA) having chelating acidic groups were employed. Metal silicate deposits were obtained artificially in the lab-scale pressurized reactor. The experimental conditions employed were quite similar to a model power plant located in Çanakkale, Turkey. The concentration of dissolved silica was increased from 130 to 420 mg/L when 100 mg/L PEG 1500 and 25 mg/L PVSA were employed as a mixture. For the atomic-level understanding of the interaction of chelating groups with metal cations, DFT calculations were performed too.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The increase of silicate solubility is a big challenge for both hot and cold water because it reduces the deposition of metal silicates frequently observed in such systems and causes operational obstacles. The deposition of silicate coats the inner surface of the pipelines in an uncontrolled manner and reduces the harvesting of energy from brines. In this work, the solubility performance of two commercial water-soluble polymeric agents (poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA)) of various molecular weights employing dosage from 25 to 100 mg/L was examined. Along with dispersant-type antiscalant, poly(acrylamide) (PAM), poly(vinylsulfonic acid, sodium salt) (PVSA), and poly(vinylphosphonic acid) (PVPA) having chelating acidic groups were employed. Metal silicate deposits were obtained artificially in the lab-scale pressurized reactor. The experimental conditions employed were quite similar to a model power plant located in Çanakkale, Turkey. The concentration of dissolved silica was increased from 130 to 420 mg/L when 100 mg/L PEG 1500 and 25 mg/L PVSA were employed as a mixture. For the atomic-level understanding of the interaction of chelating groups with metal cations, DFT calculations were performed too. |
Guner, Tugrul; Aksoy, Erkan; Demir, Mustafa M; Varlikli, Canan: Perylene-embedded electrospun PS fibers for white light generation. Dyes and Pigments, 160 , pp. 501 - 508, 2019, ISSN: 0143-7208. (Type: Journal Article | Abstract | Links | BibTeX) @article{guner2019501, title = {Perylene-embedded electrospun PS fibers for white light generation}, author = {Tugrul Guner and Erkan Aksoy and Mustafa M Demir and Canan Varlikli}, url = {http://www.sciencedirect.com/science/article/pii/S0143720818313524}, doi = {https://doi.org/10.1016/j.dyepig.2018.08.040}, issn = {0143-7208}, year = {2019}, date = {2019-01-01}, journal = {Dyes and Pigments}, volume = {160}, pages = {501 - 508}, abstract = {Perylene dyes have been employed in the fabrication of white light due to their superior photophysical properties and relatively easy synthetic methods. However, their molecular aggregation in solid state is one of the main handicaps since it causes deviation in their optical properties and quenches photoluminescence quantum yields (Φf). Investigation of the photophysical properties of a green (PTE), a yellow (PDI) and a new red (DiPhAPDI) emitting perylene derivative in solution, drop-casted films, polystyrene (PS) fibers and PS fibers embedded in poly (dimethyl siloxane) (PDMS) showed that PS:dye fibers prevent aggregation to some extend and allows high Φf of dyes. The Φf values of PTE, PDI and DiPhAPDI were all higher than 93.0% in solution and 84.8%, 94.3% and 73.6%, respectively in PS:dye fibers. Embedding the fibers in PDMS improved the photostabilities of the dyes two folds compared to their solution phases. The prepared dye containing fibers were combined together into a single PDMS film and utilized as a frequency conversion layer on a blue LED. Fabricated samples were found to show high color rendering index (≥90), adjustable CCT (7500 K–5000 K), and power efficiency values exceeding 200 l m/W depending on the used fiber amount in mass.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Perylene dyes have been employed in the fabrication of white light due to their superior photophysical properties and relatively easy synthetic methods. However, their molecular aggregation in solid state is one of the main handicaps since it causes deviation in their optical properties and quenches photoluminescence quantum yields (Φf). Investigation of the photophysical properties of a green (PTE), a yellow (PDI) and a new red (DiPhAPDI) emitting perylene derivative in solution, drop-casted films, polystyrene (PS) fibers and PS fibers embedded in poly (dimethyl siloxane) (PDMS) showed that PS:dye fibers prevent aggregation to some extend and allows high Φf of dyes. The Φf values of PTE, PDI and DiPhAPDI were all higher than 93.0% in solution and 84.8%, 94.3% and 73.6%, respectively in PS:dye fibers. Embedding the fibers in PDMS improved the photostabilities of the dyes two folds compared to their solution phases. The prepared dye containing fibers were combined together into a single PDMS film and utilized as a frequency conversion layer on a blue LED. Fabricated samples were found to show high color rendering index (≥90), adjustable CCT (7500 K–5000 K), and power efficiency values exceeding 200 l m/W depending on the used fiber amount in mass. |
Guvenc, Meric C; Adem, Umut: Influence of aging on electrocaloric effect in Li+ doped BaTiO3 ceramics. Journal of Alloys and Compounds, 791 , pp. 674 - 680, 2019, ISSN: 0925-8388. (Type: Journal Article | Abstract | Links | BibTeX) @article{guvenc2019674, title = {Influence of aging on electrocaloric effect in Li+ doped BaTiO3 ceramics}, author = {Meric C Guvenc and Umut Adem}, url = {http://www.sciencedirect.com/science/article/pii/S0925838819312009}, doi = {https://doi.org/10.1016/j.jallcom.2019.03.356}, issn = {0925-8388}, year = {2019}, date = {2019-01-01}, journal = {Journal of Alloys and Compounds}, volume = {791}, pages = {674 - 680}, abstract = {Aging creates significant changes in the properties of the ferroelectric materials such as dielectric and piezoelectric properties. However, the influence of aging on the electrocaloric effect (ECE) has not yet been investigated. In this work, we investigate the effect of the aging on the ECE in acceptor (Li+) doped BaTiO3 ceramics. We observe that aging induced defect polarization (PD) reduces the saturation polarization of the doped samples until Tc = 115 °C. Above that temperature PD loses its effectiveness and material behaves like a fresh sample. Suppression of polarization below TC due to aging effect results in a sharper slope change in the temperature dependence of electrical polarization in aged samples which causes an increase in the electrocaloric temperature change of Li+ doped BaTiO3 ceramics up to 23% at TC. Above a critical Li doping amount, both negative and positive electrocaloric effect are observed in the same sample.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Aging creates significant changes in the properties of the ferroelectric materials such as dielectric and piezoelectric properties. However, the influence of aging on the electrocaloric effect (ECE) has not yet been investigated. In this work, we investigate the effect of the aging on the ECE in acceptor (Li+) doped BaTiO3 ceramics. We observe that aging induced defect polarization (PD) reduces the saturation polarization of the doped samples until Tc = 115 °C. Above that temperature PD loses its effectiveness and material behaves like a fresh sample. Suppression of polarization below TC due to aging effect results in a sharper slope change in the temperature dependence of electrical polarization in aged samples which causes an increase in the electrocaloric temperature change of Li+ doped BaTiO3 ceramics up to 23% at TC. Above a critical Li doping amount, both negative and positive electrocaloric effect are observed in the same sample. |
Olcer, Yekta Arya; Tascon, Marcos; Eroglu, Ahmet E; Boyacı, Ezel: Thin film microextraction: Towards faster and more sensitive microextraction. TrAC Trends in Analytical Chemistry, 113 , pp. 93 - 101, 2019, ISSN: 0165-9936. (Type: Journal Article | Abstract | Links | BibTeX) @article{olcer2019, title = {Thin film microextraction: Towards faster and more sensitive microextraction}, author = {Yekta Arya Olcer and Marcos Tascon and Ahmet E Eroglu and Ezel Boyacı}, url = {http://www.sciencedirect.com/science/article/pii/S0165993618305752}, doi = {https://doi.org/10.1016/j.trac.2019.01.022}, issn = {0165-9936}, year = {2019}, date = {2019-01-01}, journal = {TrAC Trends in Analytical Chemistry}, volume = {113}, pages = {93 - 101}, abstract = {Thin film microextraction (TFME) is an analytical tool that has been proven to be suitable for integrated sampling and sample preparation of a wide variety of routine and on-site applications. Compared to the traditional microextraction techniques, the most important advantage of TFME is its enhanced sensitivity due to the relatively larger extractive phase spread over a larger surface area. The technique, in this way, facilitates fast extraction kinetics and high extractive capacity. Moreover, TFME offers high versatility for device development over classical SPME technologies due to the plethora of available extractive phases, coating methods and geometry options. The goal of this review is to provide a comprehensive summary of the contemporary advances in this exciting field covering novel extractive phases, technological and methodological developments, and relevant cutting-edge applications. Finally, a critical discussion of the future trends on TFME is also presented.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thin film microextraction (TFME) is an analytical tool that has been proven to be suitable for integrated sampling and sample preparation of a wide variety of routine and on-site applications. Compared to the traditional microextraction techniques, the most important advantage of TFME is its enhanced sensitivity due to the relatively larger extractive phase spread over a larger surface area. The technique, in this way, facilitates fast extraction kinetics and high extractive capacity. Moreover, TFME offers high versatility for device development over classical SPME technologies due to the plethora of available extractive phases, coating methods and geometry options. The goal of this review is to provide a comprehensive summary of the contemporary advances in this exciting field covering novel extractive phases, technological and methodological developments, and relevant cutting-edge applications. Finally, a critical discussion of the future trends on TFME is also presented. |
Kahraman, Z; Kandemir, A; Yagmurcukardes, M; Sahin, H: Single-Layer Janus-Type Platinum Dichalcogenides and Their Heterostructures. The Journal of Physical Chemistry C, 123 (7), pp. 4549-4557, 2019. (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.jpcc.8b11837, title = {Single-Layer Janus-Type Platinum Dichalcogenides and Their Heterostructures}, author = {Z Kahraman and A Kandemir and M Yagmurcukardes and H Sahin}, url = {https://doi.org/10.1021/acs.jpcc.8b11837}, doi = {10.1021/acs.jpcc.8b11837}, year = {2019}, date = {2019-01-01}, journal = {The Journal of Physical Chemistry C}, volume = {123}, number = {7}, pages = {4549-4557}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Kandemir, A; Iyikanat, F; Sahin, H: Monitoring the crystal orientation of black-arsenic via vibrational spectra. J. Mater. Chem. C, 7 , pp. 1228-1236, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{C8TC05167D, title = {Monitoring the crystal orientation of black-arsenic via vibrational spectra}, author = {A Kandemir and F Iyikanat and H Sahin}, url = {http://dx.doi.org/10.1039/C8TC05167D}, doi = {10.1039/C8TC05167D}, year = {2019}, date = {2019-01-01}, journal = {J. Mater. Chem. C}, volume = {7}, pages = {1228-1236}, publisher = {The Royal Society of Chemistry}, abstract = {In this study, the structural, mechanical, and vibrational properties of a recently discovered anisotropic ultra-thin material, black-arsenic (b-As), are investigated by using density functional theory. Direction dependent elastic constants such as in-plane stiffness, Young's modulus and Poisson's ratio of single-layer b-As are calculated and compared with those of the structural cousin black-phosphorus (b-P). The calculated Poisson's ratio of b-As for the zigzag direction is nearly 1, which is quite higher than that of b-P, 0.65. Besides, it is found that all the three elastic constants are highly anisotropic and their values in the zigzag direction are almost three times higher than that of the armchair direction. The mechanical strength of the material is also calculated and high-toughness is seen in both armchair and zigzag directions. It is revealed that the material is quite stiff against straining along the zigzag direction; in contrast, it is quite flexible along the armchair direction. Vibrational stability analysis shows that the material is stable up to 9% biaxially applied strain, and 12% and 45% uniaxially applied strain in the zigzag and armchair directions, respectively. Furthermore, the prominent Raman active peaks of the b-As structure show strong anisotropy in the strain dependent vibrational spectra and they can also be used for easy-determination of the crystal orientation of b-As from Raman measurements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, the structural, mechanical, and vibrational properties of a recently discovered anisotropic ultra-thin material, black-arsenic (b-As), are investigated by using density functional theory. Direction dependent elastic constants such as in-plane stiffness, Young's modulus and Poisson's ratio of single-layer b-As are calculated and compared with those of the structural cousin black-phosphorus (b-P). The calculated Poisson's ratio of b-As for the zigzag direction is nearly 1, which is quite higher than that of b-P, 0.65. Besides, it is found that all the three elastic constants are highly anisotropic and their values in the zigzag direction are almost three times higher than that of the armchair direction. The mechanical strength of the material is also calculated and high-toughness is seen in both armchair and zigzag directions. It is revealed that the material is quite stiff against straining along the zigzag direction; in contrast, it is quite flexible along the armchair direction. Vibrational stability analysis shows that the material is stable up to 9% biaxially applied strain, and 12% and 45% uniaxially applied strain in the zigzag and armchair directions, respectively. Furthermore, the prominent Raman active peaks of the b-As structure show strong anisotropy in the strain dependent vibrational spectra and they can also be used for easy-determination of the crystal orientation of b-As from Raman measurements. |
Yardimci, Atike Ince; Aypek, Hande; Ozturk, Ozgur; Yilmaz, Selahattin; Ozcivici, Engin; Mese, Gulistan; Selamet, Yusuf: CNT Incorporated Polyacrilonitrile/Polypyrrole Nanofibers as Keratinocytes Scaffold. Journal of Biomimetics, Biomaterials and Biomedical Engineering, 41 , pp. 69–81, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{inceyardimci2019, title = {CNT Incorporated Polyacrilonitrile/Polypyrrole Nanofibers as Keratinocytes Scaffold}, author = {Atike Ince Yardimci and Hande Aypek and Ozgur Ozturk and Selahattin Yilmaz and Engin Ozcivici and Gulistan Mese and Yusuf Selamet}, doi = {10.4028/www.scientific.net/JBBBE.41.69}, year = {2019}, date = {2019-01-01}, journal = {Journal of Biomimetics, Biomaterials and Biomedical Engineering}, volume = {41}, pages = {69--81}, abstract = {Polypyrrole (PPy) is an attractive scaffold material for tissue engineering with its non-toxic and electrically conductive properties. There has not been enough information about PPy usage in skin tissue engineering. The aim of this study is to investigate biocompatibility of polyacrilonitrile (PAN)/PPy nanofibrous scaffold for human keratinocytes. PAN/PPy bicomponent nanofibers were prepared by electrospinning, in various PPy concentrations and with carbon nanotube (CNT) incorporation. The average diameter of electrospun nanofibers decreased with increasing PPy concentration. Further, agglomerated CNTs caused beads and disordered parts on the surface of nanofibers. Biocompatibility of these PAN/PPy and PAN/PPy/CNT scaffolds were analyzed in vitro. Both scaffolds provided adhesion and proliferation of keratinocytes. Nanofiber diameter did not significantly influence the morphology of cells. However, with increasing number of cells, cells stayed among nanofibers and this affected their shape and size. In this study, we demonstrated that PAN/PPy and PAN/PPy/CNT scaffolds enabled the growth of keratinocytes, showing their biocompatibility.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Polypyrrole (PPy) is an attractive scaffold material for tissue engineering with its non-toxic and electrically conductive properties. There has not been enough information about PPy usage in skin tissue engineering. The aim of this study is to investigate biocompatibility of polyacrilonitrile (PAN)/PPy nanofibrous scaffold for human keratinocytes. PAN/PPy bicomponent nanofibers were prepared by electrospinning, in various PPy concentrations and with carbon nanotube (CNT) incorporation. The average diameter of electrospun nanofibers decreased with increasing PPy concentration. Further, agglomerated CNTs caused beads and disordered parts on the surface of nanofibers. Biocompatibility of these PAN/PPy and PAN/PPy/CNT scaffolds were analyzed in vitro. Both scaffolds provided adhesion and proliferation of keratinocytes. Nanofiber diameter did not significantly influence the morphology of cells. However, with increasing number of cells, cells stayed among nanofibers and this affected their shape and size. In this study, we demonstrated that PAN/PPy and PAN/PPy/CNT scaffolds enabled the growth of keratinocytes, showing their biocompatibility. |
Arica, Tugce A; Kuman, Merve; Gercel, Ozgul; Ayas, Erhan: Poly(dopamine) grafted bio-silica composite with tetraethylenepentamine ligands for enhanced adsorption of pollutants. Chemical Engineering Research and Design, 141 , pp. 317 - 327, 2019, ISSN: 0263-8762. (Type: Journal Article | Abstract | Links | BibTeX) @article{ARICA2019317, title = {Poly(dopamine) grafted bio-silica composite with tetraethylenepentamine ligands for enhanced adsorption of pollutants}, author = {Tugce A Arica and Merve Kuman and Ozgul Gercel and Erhan Ayas}, url = {http://www.sciencedirect.com/science/article/pii/S0263876218305835}, doi = {https://doi.org/10.1016/j.cherd.2018.11.003}, issn = {0263-8762}, year = {2019}, date = {2019-01-01}, journal = {Chemical Engineering Research and Design}, volume = {141}, pages = {317 - 327}, abstract = {In this study, diatomite fossil particles (i.e., bio-silica) was treated with strong acid solution and coated with polydopamine (bio-silica-PDA) using aqueous-based bioinspired coating method. The bio-silica-PDA was grafted with tetraethylenepentamine (TEPA) ligand to increase binding sites on the material surfaces. The biosilica-PDA-TEPA particles was characterized using Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), X-Ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET) method. The adsorption performance of the biosilica-PDA-TEPA particles was studied using a model dye (i.e., Direct Blue 74; DB-74) from aqueous solutions using biosilica-PDA as a control system. Batch system was used to optimize experimental conditions for the removal of DB-74 dye on the sorbents. The adsorption of DB-74 on the biosilica-PDA-TEPA particles was studied in the pH range of 2.0–8.0. The amount adsorbed DB-74 dye on the biosilica-PDA-TEPA was 363.3mgg−1 (using initial dye concentration 1200mgL−1, pH 3.0 and temperature 25°C). Adsorption of DB-74 dye on biosilica-PDA-TEPA particles fitted well Langmuir model. The equilibrium adsorption time was completed within 10min and the experimental data was defined well by the pseudo-second-order model. In addition, the biosilica-PDA-TEPA particles presented a good performance after regeneration. This result show that the presented low-cost porous biosilica-PDA-TEPA particles can be a good candidate as a novel sorbent system for removal of micro-pollutants from wastewaters.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, diatomite fossil particles (i.e., bio-silica) was treated with strong acid solution and coated with polydopamine (bio-silica-PDA) using aqueous-based bioinspired coating method. The bio-silica-PDA was grafted with tetraethylenepentamine (TEPA) ligand to increase binding sites on the material surfaces. The biosilica-PDA-TEPA particles was characterized using Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), X-Ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET) method. The adsorption performance of the biosilica-PDA-TEPA particles was studied using a model dye (i.e., Direct Blue 74; DB-74) from aqueous solutions using biosilica-PDA as a control system. Batch system was used to optimize experimental conditions for the removal of DB-74 dye on the sorbents. The adsorption of DB-74 on the biosilica-PDA-TEPA particles was studied in the pH range of 2.0–8.0. The amount adsorbed DB-74 dye on the biosilica-PDA-TEPA was 363.3mgg−1 (using initial dye concentration 1200mgL−1, pH 3.0 and temperature 25°C). Adsorption of DB-74 dye on biosilica-PDA-TEPA particles fitted well Langmuir model. The equilibrium adsorption time was completed within 10min and the experimental data was defined well by the pseudo-second-order model. In addition, the biosilica-PDA-TEPA particles presented a good performance after regeneration. This result show that the presented low-cost porous biosilica-PDA-TEPA particles can be a good candidate as a novel sorbent system for removal of micro-pollutants from wastewaters. |
Topcu, Gokhan; Guner, Tugrul; Inci, Ezgi; Demir, Mustafa M: Colorimetric and plasmonic pressure sensors based on polyacrylamide/Au nanoparticles. Sensors and Actuators A: Physical, 295 , pp. 503-511, 2019, ISSN: 0924-4247. (Type: Journal Article | Abstract | Links | BibTeX) @article{TOPCU2019503, title = {Colorimetric and plasmonic pressure sensors based on polyacrylamide/Au nanoparticles}, author = {Gokhan Topcu and Tugrul Guner and Ezgi Inci and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S0924424719304108}, doi = {https://doi.org/10.1016/j.sna.2019.06.038}, issn = {0924-4247}, year = {2019}, date = {2019-01-01}, journal = {Sensors and Actuators A: Physical}, volume = {295}, pages = {503-511}, abstract = {Colorimetric stimuli-responsive nanomaterials have emerged as an eminent tool for sensor applications. Among this class of sensing elements, gold nanoparticle-based (Au NP) nanostructures are promising materials due to their plasmonic features. In this study, free-standing flexible polymeric films having intense optical response upon application of mechanical pressure were fabricated based on polyacrylamide (PAAm) and Au NPs. Pressure may cause plasmonic shift most probably due to the disassembly of the clusters from blue to reddish individual particles depending on the extent of pressure. Temperature, time, and extent of pressure were examined in terms of spectral change of Au particles. The sensor films depict working range up to 160 MPa, which shows minor change at elevated temperatures probably due to the stress induced crystallization of PAAm. For practical applications, a simple red-green-blue (RGB) space-based algorithm was presented for smartphone-assisted detection of applied pressure. Moreover, the PAAm/Au composite structure shows self-healing without any additive under ambient conditions even after divided into pieces.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Colorimetric stimuli-responsive nanomaterials have emerged as an eminent tool for sensor applications. Among this class of sensing elements, gold nanoparticle-based (Au NP) nanostructures are promising materials due to their plasmonic features. In this study, free-standing flexible polymeric films having intense optical response upon application of mechanical pressure were fabricated based on polyacrylamide (PAAm) and Au NPs. Pressure may cause plasmonic shift most probably due to the disassembly of the clusters from blue to reddish individual particles depending on the extent of pressure. Temperature, time, and extent of pressure were examined in terms of spectral change of Au particles. The sensor films depict working range up to 160 MPa, which shows minor change at elevated temperatures probably due to the stress induced crystallization of PAAm. For practical applications, a simple red-green-blue (RGB) space-based algorithm was presented for smartphone-assisted detection of applied pressure. Moreover, the PAAm/Au composite structure shows self-healing without any additive under ambient conditions even after divided into pieces. |
Ozen, S; Guner, T; Topcu, G; Ozcan, M; Demir, M M; Sahin, H: Experimental and first-principles investigation of Cr-driven color change in cesium lead halide perovskites. Journal of Applied Physics, 125 (22), pp. 225705, 2019. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/1.5092779, title = {Experimental and first-principles investigation of Cr-driven color change in cesium lead halide perovskites}, author = {S Ozen and T Guner and G Topcu and M Ozcan and M M Demir and H Sahin}, url = {https://doi.org/10.1063/1.5092779}, doi = {10.1063/1.5092779}, year = {2019}, date = {2019-01-01}, journal = {Journal of Applied Physics}, volume = {125}, number = {22}, pages = {225705}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Shukla, S K; Kushwaha, Chandra Shekhar; Guner, Tugrul; Demir, Mustafa M: Chemically modified optical fibers in advanced technology: An overview. Optics & Laser Technology, 115 , pp. 404-432, 2019, ISSN: 0030-3992. (Type: Journal Article | Abstract | Links | BibTeX) @article{SHUKLA2019404, title = {Chemically modified optical fibers in advanced technology: An overview}, author = {S K Shukla and Chandra Shekhar Kushwaha and Tugrul Guner and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S0030399218309903}, doi = {https://doi.org/10.1016/j.optlastec.2019.02.025}, issn = {0030-3992}, year = {2019}, date = {2019-01-01}, journal = {Optics & Laser Technology}, volume = {115}, pages = {404-432}, abstract = {In recent years, chemically modified optical fibers have widely used for development of several advanced chemical and biosensors, biomedical technology and environmental monitoring. The chemically modified optical fiber bears several valuable properties like energy loss, catalytic behaviour, refractive index, and mechanical strength to advance the optical fiber technology. In this article, we reviewed the chemically-modified optical fiber and their applications in different optical fiber-based technologies. The basics of optical fiber and their modification are discussed along with the adopted methodologies. The advancements in different optical fiber based technologies viz sensing, imaging, tomography, magnetic resonance imaging, photodynamic therapy, optogenics, surgery and environmental monitoring are discussed in the light of the contribution of chemically modified optical fibers. In conclusion, success and challenges for the use of chemically modified-optical fiber are presented on the basis of existing literature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In recent years, chemically modified optical fibers have widely used for development of several advanced chemical and biosensors, biomedical technology and environmental monitoring. The chemically modified optical fiber bears several valuable properties like energy loss, catalytic behaviour, refractive index, and mechanical strength to advance the optical fiber technology. In this article, we reviewed the chemically-modified optical fiber and their applications in different optical fiber-based technologies. The basics of optical fiber and their modification are discussed along with the adopted methodologies. The advancements in different optical fiber based technologies viz sensing, imaging, tomography, magnetic resonance imaging, photodynamic therapy, optogenics, surgery and environmental monitoring are discussed in the light of the contribution of chemically modified optical fibers. In conclusion, success and challenges for the use of chemically modified-optical fiber are presented on the basis of existing literature. |
Su, He-Ping; Li, Shu-Fang; Han, Yifeng; Wu, Mei-Xia; Gui, Churen; Chang, Yanfen; Croft, Mark; Ehrlich, Steven; Khalid, Syed; Adem, Umut; Dong, Shuai; Sun, Young; Huang, Feng; Li, Man-Rong: Predicted polymorph manipulation in an exotic double perovskite oxide. J. Mater. Chem. C, 7 , pp. 12306-12311, 2019. (Type: Journal Article | Abstract | Links | BibTeX) @article{C9TC03367J, title = {Predicted polymorph manipulation in an exotic double perovskite oxide}, author = {He-Ping Su and Shu-Fang Li and Yifeng Han and Mei-Xia Wu and Churen Gui and Yanfen Chang and Mark Croft and Steven Ehrlich and Syed Khalid and Umut Adem and Shuai Dong and Young Sun and Feng Huang and Man-Rong Li}, url = {http://dx.doi.org/10.1039/C9TC03367J}, doi = {10.1039/C9TC03367J}, year = {2019}, date = {2019-01-01}, journal = {J. Mater. Chem. C}, volume = {7}, pages = {12306-12311}, publisher = {The Royal Society of Chemistry}, abstract = {Predicted polymorph manipulation offers a cutting-edge route to design function-oriented materials in an exotic double perovskite-related oxide A2BB′O6 with small A-site cations. Herein, first-principles density functional theory calculations in light of the equation of state for solid, for the first time, was used to predict the Mg3TeO6 (R̄)-to-perovskite (P21/n) type phase transition in Mn3TeO6 at around 5 GPa, regardless of the deployment of magnetic interactions. The high-pressure synthesis and synchrotron diffraction crystal structure analysis corroborated experimentally the polymorph variation in Mn22+Mn2+Te6+O6, which was accompanied by a 13 K increase in the antiferromagnetic ordering temperature (37 K) in the high-pressure perovskite polymorph compared to that of the ambient-pressure R̄ phase (24 K). The magnetodielectric coupling remains up to 50 K with the maximum being around the magnetic ordering temperature in the perovskite Mn3TeO6. Thus, the predicted polymorph manipulation here offers the possibility of discovering accelerated materials by inverse design in exotic perovskite oxides.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Predicted polymorph manipulation offers a cutting-edge route to design function-oriented materials in an exotic double perovskite-related oxide A2BB′O6 with small A-site cations. Herein, first-principles density functional theory calculations in light of the equation of state for solid, for the first time, was used to predict the Mg3TeO6 (R̄)-to-perovskite (P21/n) type phase transition in Mn3TeO6 at around 5 GPa, regardless of the deployment of magnetic interactions. The high-pressure synthesis and synchrotron diffraction crystal structure analysis corroborated experimentally the polymorph variation in Mn22+Mn2+Te6+O6, which was accompanied by a 13 K increase in the antiferromagnetic ordering temperature (37 K) in the high-pressure perovskite polymorph compared to that of the ambient-pressure R̄ phase (24 K). The magnetodielectric coupling remains up to 50 K with the maximum being around the magnetic ordering temperature in the perovskite Mn3TeO6. Thus, the predicted polymorph manipulation here offers the possibility of discovering accelerated materials by inverse design in exotic perovskite oxides. |
Topcu, Gokhan; Koç, Gonca A; Baba, Alper; Demir, Mustafa M: The injection of CO2 to hypersaline geothermal brine: A case study for Tuzla region. Geothermics, 80 , pp. 86-91, 2019, ISSN: 0375-6505. (Type: Journal Article | Abstract | Links | BibTeX) @article{TOPCU201986, title = {The injection of CO2 to hypersaline geothermal brine: A case study for Tuzla region}, author = {Gokhan Topcu and Gonca A Koç and Alper Baba and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S037565051830395X}, doi = {https://doi.org/10.1016/j.geothermics.2019.02.011}, issn = {0375-6505}, year = {2019}, date = {2019-01-01}, journal = {Geothermics}, volume = {80}, pages = {86-91}, abstract = {Scaling is a serious issue for geothermal power plants since it remarkably decreases the harvesting of energy. The reduction of pH by organic acids whose structure is close to CO2 for instance formic acid has been an effective solution for the minimization of scaling. Herein, the effect of CO2 injection on the formation of scaling particularly metal-silicates was investigated for the model case of Tuzla Geothermal Field (TGF) located in the northwest of Turkey. CO2 has an acidic character in aqueous systems because it leads to the formation of carbonic acid. The injection of 20.6 m3/s CO2 (approximately 88 ppm) to hypersaline brine of TGF is a promising green approach for both mitigation of scaling by reducing pH from 7.2 to 6.2 at the well-head and the minimization of potential corrosion compared to the use of formic acid (55 ppm).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Scaling is a serious issue for geothermal power plants since it remarkably decreases the harvesting of energy. The reduction of pH by organic acids whose structure is close to CO2 for instance formic acid has been an effective solution for the minimization of scaling. Herein, the effect of CO2 injection on the formation of scaling particularly metal-silicates was investigated for the model case of Tuzla Geothermal Field (TGF) located in the northwest of Turkey. CO2 has an acidic character in aqueous systems because it leads to the formation of carbonic acid. The injection of 20.6 m3/s CO2 (approximately 88 ppm) to hypersaline brine of TGF is a promising green approach for both mitigation of scaling by reducing pH from 7.2 to 6.2 at the well-head and the minimization of potential corrosion compared to the use of formic acid (55 ppm). |
Demirkurt, Begüm; Cakan-Akdogan, Gulcin; Akdogan, Yasar: Preparation of albumin nanoparticles in water-in-ionic liquid microemulsions. Journal of Molecular Liquids, 295 , pp. 111713, 2019, ISSN: 0167-7322. (Type: Journal Article | Abstract | Links | BibTeX) @article{DEMIRKURT2019111713, title = {Preparation of albumin nanoparticles in water-in-ionic liquid microemulsions}, author = {Begüm Demirkurt and Gulcin Cakan-Akdogan and Yasar Akdogan}, url = {https://www.sciencedirect.com/science/article/pii/S0167732219336049}, doi = {https://doi.org/10.1016/j.molliq.2019.111713}, issn = {0167-7322}, year = {2019}, date = {2019-01-01}, journal = {Journal of Molecular Liquids}, volume = {295}, pages = {111713}, abstract = {Ionic liquids (ILs) with a variety of properties have been considered a unique class of solvents. Using ILs in microemulsions as oil substitutes provides environmentally benign media for various applications including nanoparticle synthesis. Here, bovine serum albumin nanoparticles (BSA NPs) widely used in drug delivery studies were prepared in nano-sized water droplets of water-in-IL (W/IL) microemulsion systems. A hydrophobic IL of 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) was used as oil component in place of oils (castor oil, olive oil, etc.) and/or conventional organic solvents (cyclohexane, dichloromethane, etc.) in an emulsification method. In order to obtain spherical BSA NPs, high speed homogenizer treatment was applied followed by glutaraldehyde addition. Effects of glutaraldehyde, speed of homogenizer, type of surfactants and compositional fractions of the microemulsion components on the formation of water droplets and/or preparation of BSA NPs were studied using FTIR, EPR, DLS, and SEM techniques. Optimization of these preparation parameters showed that 3 wt% of BSA in a water/Tween 20/BmimPF6 microemulsion with 20:50:30 wt% yielded ~100 nm average sized BSA NPs based on the SEM analysis. Although, water droplet size strongly depends on the water content, BSA nanoparticle size did not show a significant dependency on the water content. On the other hand, surfactant/IL weight ratio is more crucial for obtaining more uniformly size distributed albumin nanoparticles. A significant cellular uptake of BSA NPs prepared in IL based microemulsions with high cell viability showed the potential of this technique in preparation of albumin nanoparticles that can be used also in drug delivery studies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ionic liquids (ILs) with a variety of properties have been considered a unique class of solvents. Using ILs in microemulsions as oil substitutes provides environmentally benign media for various applications including nanoparticle synthesis. Here, bovine serum albumin nanoparticles (BSA NPs) widely used in drug delivery studies were prepared in nano-sized water droplets of water-in-IL (W/IL) microemulsion systems. A hydrophobic IL of 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) was used as oil component in place of oils (castor oil, olive oil, etc.) and/or conventional organic solvents (cyclohexane, dichloromethane, etc.) in an emulsification method. In order to obtain spherical BSA NPs, high speed homogenizer treatment was applied followed by glutaraldehyde addition. Effects of glutaraldehyde, speed of homogenizer, type of surfactants and compositional fractions of the microemulsion components on the formation of water droplets and/or preparation of BSA NPs were studied using FTIR, EPR, DLS, and SEM techniques. Optimization of these preparation parameters showed that 3 wt% of BSA in a water/Tween 20/BmimPF6 microemulsion with 20:50:30 wt% yielded ~100 nm average sized BSA NPs based on the SEM analysis. Although, water droplet size strongly depends on the water content, BSA nanoparticle size did not show a significant dependency on the water content. On the other hand, surfactant/IL weight ratio is more crucial for obtaining more uniformly size distributed albumin nanoparticles. A significant cellular uptake of BSA NPs prepared in IL based microemulsions with high cell viability showed the potential of this technique in preparation of albumin nanoparticles that can be used also in drug delivery studies. |
Baba, A; Şaroğlu, F; Akkuş, I; Özel, N; Yeşilnacar, M İ; Nalbantçılar, M T; Demir, M M; Gökçen, G; Arslan, Ş; Dursun, N; Uzelli, T; Yazdani, H: Geological and hydrogeochemical properties of geothermal systems in the southeastern region of Turkey. Geothermics, 78 , pp. 255-271, 2019, ISSN: 0375-6505. (Type: Journal Article | Abstract | Links | BibTeX) @article{BABA2019255, title = {Geological and hydrogeochemical properties of geothermal systems in the southeastern region of Turkey}, author = {A Baba and F Şaroğlu and I Akkuş and N Özel and M İ Yeşilnacar and M T Nalbantçılar and M M Demir and G Gökçen and Ş Arslan and N Dursun and T Uzelli and H Yazdani}, url = {https://www.sciencedirect.com/science/article/pii/S0375650518300749}, doi = {https://doi.org/10.1016/j.geothermics.2018.12.010}, issn = {0375-6505}, year = {2019}, date = {2019-01-01}, journal = {Geothermics}, volume = {78}, pages = {255-271}, abstract = {The Anatolia region is one of the most seismically active regions in the world. It has a considerably high level of geothermal energy potential thanks to its geological and tectonic settings. The Southeastern Anatolia Region (GAP) is located in the south of Bitlis-Zagros Suture Zone (BZSZ) which is in the Arabian foreland. During the neotectonic period, the folded structures have been developed under the influence of tectonic compression from the Upper Miocene in the GAP Region where it is closely related to active tectonics. These tectonic activities produce more geothermal resources. Few studies have been carried out in this region for geothermal energy. Limited portions of the geothermal resources have been used both for thermal tourism and greenhouses in the GAP region. The aim of this study is to determine geological, tectonic and hydrogeochemical properties of a geothermal system in the GAP Region. The result indicates that the surface temperatures of geothermal fluids are from 20 to 84.5 °C A large number of abandoned oil wells, whose temperature reaches 140 °C, are found in the region. Also, hydrogeochemical results show that deep circulated geothermal fluids are enriched with Na-Cl and shallow geothermal system fluids have Na−HCO3 and Ca-SO4 characters because of cold water mixing and water-rock interaction. Cold waters are generally of Ca-Mg−HCO3 and Ca−HCO3 type. Cation geothermometers were used for determining reservoir temperature of the geothermal resources in the region. The results show that the reservoir temperature of these geothermal resources ranges from 50 °C to 200 °C. The isotope data (oxygen-18, deuterium and tritium) suggests that geothermal fluid is formed by local recharge and deep circulation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Anatolia region is one of the most seismically active regions in the world. It has a considerably high level of geothermal energy potential thanks to its geological and tectonic settings. The Southeastern Anatolia Region (GAP) is located in the south of Bitlis-Zagros Suture Zone (BZSZ) which is in the Arabian foreland. During the neotectonic period, the folded structures have been developed under the influence of tectonic compression from the Upper Miocene in the GAP Region where it is closely related to active tectonics. These tectonic activities produce more geothermal resources. Few studies have been carried out in this region for geothermal energy. Limited portions of the geothermal resources have been used both for thermal tourism and greenhouses in the GAP region. The aim of this study is to determine geological, tectonic and hydrogeochemical properties of a geothermal system in the GAP Region. The result indicates that the surface temperatures of geothermal fluids are from 20 to 84.5 °C A large number of abandoned oil wells, whose temperature reaches 140 °C, are found in the region. Also, hydrogeochemical results show that deep circulated geothermal fluids are enriched with Na-Cl and shallow geothermal system fluids have Na−HCO3 and Ca-SO4 characters because of cold water mixing and water-rock interaction. Cold waters are generally of Ca-Mg−HCO3 and Ca−HCO3 type. Cation geothermometers were used for determining reservoir temperature of the geothermal resources in the region. The results show that the reservoir temperature of these geothermal resources ranges from 50 °C to 200 °C. The isotope data (oxygen-18, deuterium and tritium) suggests that geothermal fluid is formed by local recharge and deep circulation. |
Göksel, Yaman; Akdogan, Yasar: Increasing spontaneous wet adhesion of DOPA with gelation characterized by EPR spectroscopy. Materials Chemistry and Physics, 228 , pp. 124-130, 2019, ISSN: 0254-0584. (Type: Journal Article | Abstract | Links | BibTeX) @article{GOKSEL2019124, title = {Increasing spontaneous wet adhesion of DOPA with gelation characterized by EPR spectroscopy}, author = {Yaman Göksel and Yasar Akdogan}, url = {https://www.sciencedirect.com/science/article/pii/S025405841930149X}, doi = {https://doi.org/10.1016/j.matchemphys.2019.02.054}, issn = {0254-0584}, year = {2019}, date = {2019-01-01}, journal = {Materials Chemistry and Physics}, volume = {228}, pages = {124-130}, abstract = {The presence of water molecules around both adhesive materials and surface results in the hydration barriers that weaken adhesion. In nature, mussels attach to various types of surfaces by using 3,4-dihydroxyphenylalanine (DOPA) containing mussel foot proteins. DOPA shows wet adhesive properties before and after contribution in the hydrogel formation. Here, the wet adhesive properties of DOPA modified four armed poly(ethylene glycol) polymer (PEG-(DOPA)4) and its hydrogels induced by (IO4)- or (Cr2O7)2- ions are compared by using electron paramagnetic resonance (EPR) spectroscopy in terms of their surface coverages. In water, spin labeled hydrophobic polystyrene (SL-PS) and hydrophilic silica (SL-SiO2) nanoparticles are prepared, and the percentages of their covered surface values are obtained. Without applying force, the adhesion to SL-PS increases in the order of PEG-(DOPA)4 < PEG-(DOPA)4 + (IO4)- hydrogel < PEG-(DOPA)4 + (Cr2O7)2- hydrogel with the percentages of surface coverages 65%, 76% and 93%, respectively. Although, neither of PEG-(DOPA)4 polymer and (IO4)- induced PEG-(DOPA)4 hydrogel adhere to SL-SiO2 nanoparticle spontaneously, (Cr2O7)2- induced PEG-(DOPA)4 hydrogel adhere to SL-SiO2 with a 59% of surface coverage. These results show that gelation mechanisms of DOPA have effect on the spontaneous adhesion of DOPA to the wet surfaces even for the hydrophilic silica surface.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The presence of water molecules around both adhesive materials and surface results in the hydration barriers that weaken adhesion. In nature, mussels attach to various types of surfaces by using 3,4-dihydroxyphenylalanine (DOPA) containing mussel foot proteins. DOPA shows wet adhesive properties before and after contribution in the hydrogel formation. Here, the wet adhesive properties of DOPA modified four armed poly(ethylene glycol) polymer (PEG-(DOPA)4) and its hydrogels induced by (IO4)- or (Cr2O7)2- ions are compared by using electron paramagnetic resonance (EPR) spectroscopy in terms of their surface coverages. In water, spin labeled hydrophobic polystyrene (SL-PS) and hydrophilic silica (SL-SiO2) nanoparticles are prepared, and the percentages of their covered surface values are obtained. Without applying force, the adhesion to SL-PS increases in the order of PEG-(DOPA)4 < PEG-(DOPA)4 + (IO4)- hydrogel < PEG-(DOPA)4 + (Cr2O7)2- hydrogel with the percentages of surface coverages 65%, 76% and 93%, respectively. Although, neither of PEG-(DOPA)4 polymer and (IO4)- induced PEG-(DOPA)4 hydrogel adhere to SL-SiO2 nanoparticle spontaneously, (Cr2O7)2- induced PEG-(DOPA)4 hydrogel adhere to SL-SiO2 with a 59% of surface coverage. These results show that gelation mechanisms of DOPA have effect on the spontaneous adhesion of DOPA to the wet surfaces even for the hydrophilic silica surface. |
Topcu, Gokhan; Demir, Mustafa M: Effect of chain topology on plasmonic properties of pressure sensor films based on poly(acrylamide) and Au nanoparticles. Sensors and Actuators A: Physical, 295 , pp. 237-243, 2019, ISSN: 0924-4247. (Type: Journal Article | Abstract | Links | BibTeX) @article{TOPCU2019237, title = {Effect of chain topology on plasmonic properties of pressure sensor films based on poly(acrylamide) and Au nanoparticles}, author = {Gokhan Topcu and Mustafa M Demir}, url = {https://www.sciencedirect.com/science/article/pii/S0924424719305643}, doi = {https://doi.org/10.1016/j.sna.2019.06.009}, issn = {0924-4247}, year = {2019}, date = {2019-01-01}, journal = {Sensors and Actuators A: Physical}, volume = {295}, pages = {237-243}, abstract = {Au nanoparticles have been recognized as a colorimetric sensing element in polymeric systems because clustering shifts the red color of individual particles into saturated blue due to distinct plasmonic variation. The mechanism of pressure sensing is based on the disintegration of the particle clusters into the individual particles in polymers upon application of pressure. Polymers are usually composed of linear chains that provide a viscoelastic medium for their diffusion. Changing topology of polymer chains from linear to crosslinked under fixed pressure makes a clear change in spectral features of the particles probably due to the hindrance of particle diffusion by the crosslinking points. Therefore, the working range of the sensor films can be increased to higher-pressure values. In this work, polyacrylamide/Au nanoparticle films were prepared by various concentrations of formaldehyde as a crosslinking agent from 0.5 to 5.0 wt %. The initial absorption signal gradually shifts from 690 to 545 nm for linear chains upon application of pressure while shifting goes down to 571 nm for crosslinked ones. The colorimetric change is also examined under humid environments. Contrary to the crosslinking process, humid environment facilitates the diffusion of particles since the chains swell with water molecules that provide a convenient medium for particle diffusion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Au nanoparticles have been recognized as a colorimetric sensing element in polymeric systems because clustering shifts the red color of individual particles into saturated blue due to distinct plasmonic variation. The mechanism of pressure sensing is based on the disintegration of the particle clusters into the individual particles in polymers upon application of pressure. Polymers are usually composed of linear chains that provide a viscoelastic medium for their diffusion. Changing topology of polymer chains from linear to crosslinked under fixed pressure makes a clear change in spectral features of the particles probably due to the hindrance of particle diffusion by the crosslinking points. Therefore, the working range of the sensor films can be increased to higher-pressure values. In this work, polyacrylamide/Au nanoparticle films were prepared by various concentrations of formaldehyde as a crosslinking agent from 0.5 to 5.0 wt %. The initial absorption signal gradually shifts from 690 to 545 nm for linear chains upon application of pressure while shifting goes down to 571 nm for crosslinked ones. The colorimetric change is also examined under humid environments. Contrary to the crosslinking process, humid environment facilitates the diffusion of particles since the chains swell with water molecules that provide a convenient medium for particle diffusion. |
2018 |
Acar, Oktay; Varis, Serhat; Işık, Tuğba; Tirkes, Seha; Demir, Mustafa M: Synthesis and characterization of novel high temperature structural adhesives based on nadic end capped MDA-BTDA-ODA copolyimide. Materials Research Express, 5 (10), pp. 105305, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{acar2018, title = {Synthesis and characterization of novel high temperature structural adhesives based on nadic end capped MDA-BTDA-ODA copolyimide}, author = {Oktay Acar and Serhat Varis and Tuğba Işık and Seha Tirkes and Mustafa M Demir}, url = {https://doi.org/10.1088%2F2053-1591%2Faadb2e}, doi = {10.1088/2053-1591/aadb2e}, year = {2018}, date = {2018-08-01}, journal = {Materials Research Express}, volume = {5}, number = {10}, pages = {105305}, publisher = {IOP Publishing}, abstract = {A series of novel copolyimide structural adhesives were synthesized using 4,4'-diaminodiphenylmethane (MDA), 3,4'-oxydianiline (ODA) and 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA) as co-monomers, and nadic anhydride as an end cap reagent. The adhesives with different MDA and ODA contents were examined in terms of their structure, thermal stability, mechanical properties, and adhesive performance. They have glass transition temperatures (T g ) about 400 °C, with thermal stability up to 500 °C. The effect of diamine monomer compositions on adhesion performance and processability of the copolyimides were studied. The copolyimides exhibited adhesion strength up to 16.3 MPa at room temperature. Nadic end capped MDA-BTDA-ODA copolyimide resins gained adjustable and controllable processability with the addition of ether bridged aromatic segments. The copolyimide adhesive with equimolar composition of MDA:ODA is distinguished form the both commercial PMR-15 and LARC RP-46 polyimides in terms of its better processability and mechanical performance.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A series of novel copolyimide structural adhesives were synthesized using 4,4'-diaminodiphenylmethane (MDA), 3,4'-oxydianiline (ODA) and 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA) as co-monomers, and nadic anhydride as an end cap reagent. The adhesives with different MDA and ODA contents were examined in terms of their structure, thermal stability, mechanical properties, and adhesive performance. They have glass transition temperatures (T g ) about 400 °C, with thermal stability up to 500 °C. The effect of diamine monomer compositions on adhesion performance and processability of the copolyimides were studied. The copolyimides exhibited adhesion strength up to 16.3 MPa at room temperature. Nadic end capped MDA-BTDA-ODA copolyimide resins gained adjustable and controllable processability with the addition of ether bridged aromatic segments. The copolyimide adhesive with equimolar composition of MDA:ODA is distinguished form the both commercial PMR-15 and LARC RP-46 polyimides in terms of its better processability and mechanical performance. |
Özbal, G; Falkenberg, J T; Brandbyge, M; Senger, R T; Sevinçli, H: Directed growth of hydrogen lines on graphene: High-throughput simulations powered by evolutionary algorithm. Phys. Rev. Materials, 2 , pp. 073406, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{PhysRevMaterials.2.073406, title = {Directed growth of hydrogen lines on graphene: High-throughput simulations powered by evolutionary algorithm}, author = {G Özbal and J. T. Falkenberg and M Brandbyge and R T Senger and H Sevinçli}, editor = {We set up an evolutionary algorithm combined with density functional tight-binding calculations to investigate hydrogen adsorption on flat graphene and Afterwards Selected The In The (MRCL) where a mutation mechanism is also incorporated. a two-stage selection procedure is employed. candidates act as the parents of the next generation. evolutionary algorithm predicts formation of lines of hydrogen atoms on flat graphene. curved graphene the evolution follows a similar path except for a new mechanism which aligns hydrogen atoms on the line of minimum curvature. mechanism is due to the increased chemical reactivity of graphene along the minimum radius of curvature line During the evolution candidates for the new generations are created by adsorption of an additional hydrogen atom to the stable configurations of the previous generation and MRCL the reaction barrier is reduced considerably along the 3 bond angles being commensurate with the kinked geometry of hydrogenated graphene at the substrate edge. As a result and which has the potential to overcome substrate or rippling effects This growth mechanism enables lines of hydrogen atoms along the MRCL and could make it possible to define edges or nanoribbons without actually cutting the material.}, url = {https://link.aps.org/doi/10.1103/PhysRevMaterials.2.073406}, doi = {10.1103/PhysRevMaterials.2.073406}, year = {2018}, date = {2018-07-01}, journal = {Phys. Rev. Materials}, volume = {2}, pages = {073406}, publisher = {American Physical Society}, abstract = {We set up an evolutionary algorithm combined with density functional tight-binding calculations to investigate hydrogen adsorption on flat graphene and graphene monolayers curved over substrate steps. During the evolution, candidates for the new generations are created by adsorption of an additional hydrogen atom to the stable configurations of the previous generation, where a mutation mechanism is also incorporated. Afterwards a two-stage selection procedure is employed. Selected candidates act as the parents of the next generation. The evolutionary algorithm predicts formation of lines of hydrogen atoms on flat graphene. In curved graphene, the evolution follows a similar path except for a new mechanism, which aligns hydrogen atoms on the line of minimum curvature. The mechanism is due to the increased chemical reactivity of graphene along the minimum radius of curvature line (MRCL) and to sp3 bond angles being commensurate with the kinked geometry of hydrogenated graphene at the substrate edge. As a result, the reaction barrier is reduced considerably along the MRCL and hydrogenation continues like a mechanical chain reaction. This growth mechanism enables lines of hydrogen atoms along the MRCL, which has the potential to overcome substrate or rippling effects and could make it possible to define edges or nanoribbons without actually cutting the material.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We set up an evolutionary algorithm combined with density functional tight-binding calculations to investigate hydrogen adsorption on flat graphene and graphene monolayers curved over substrate steps. During the evolution, candidates for the new generations are created by adsorption of an additional hydrogen atom to the stable configurations of the previous generation, where a mutation mechanism is also incorporated. Afterwards a two-stage selection procedure is employed. Selected candidates act as the parents of the next generation. The evolutionary algorithm predicts formation of lines of hydrogen atoms on flat graphene. In curved graphene, the evolution follows a similar path except for a new mechanism, which aligns hydrogen atoms on the line of minimum curvature. The mechanism is due to the increased chemical reactivity of graphene along the minimum radius of curvature line (MRCL) and to sp3 bond angles being commensurate with the kinked geometry of hydrogenated graphene at the substrate edge. As a result, the reaction barrier is reduced considerably along the MRCL and hydrogenation continues like a mechanical chain reaction. This growth mechanism enables lines of hydrogen atoms along the MRCL, which has the potential to overcome substrate or rippling effects and could make it possible to define edges or nanoribbons without actually cutting the material. |
Özdamar, Burak; Özbal, Gözde; Sevim, Neşet Çınar Koray M; Kurt, Gizem; Kaya, Birnur; Hâldun, ; Sevinçli, : Structural, vibrational, and electronic properties of single-layer hexagonal crystals of group IV and V elements. Phys. Rev. B, 98 , pp. 045431, 2018. (Type: Journal Article | Links | BibTeX) @article{PhysRevB.98.045431, title = {Structural, vibrational, and electronic properties of single-layer hexagonal crystals of group IV and V elements}, author = {Burak Özdamar and Gözde Özbal and Neşet Çınar Koray M Sevim and Gizem Kurt and Birnur Kaya and Hâldun and Sevinçli}, url = {https://link.aps.org/doi/10.1103/PhysRevB.98.045431}, doi = {10.1103/PhysRevB.98.045431}, year = {2018}, date = {2018-07-01}, journal = {Phys. Rev. B}, volume = {98}, pages = {045431}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Kandemir, A; Akbali, B; Kahraman, Z; Badalov, S V; Ozcan, M; Iyikanat, F; Sahin, H: Structural, electronic and phononic properties of PtSe2: from monolayer to bulk. Semiconductor Science and Technology, 33 (8), pp. 085002, 2018. (Type: Journal Article | Links | BibTeX) @article{kandemir2018, title = {Structural, electronic and phononic properties of PtSe2: from monolayer to bulk}, author = {A Kandemir and B Akbali and Z Kahraman and S V Badalov and M Ozcan and F Iyikanat and H Sahin}, url = {https://doi.org/10.1088%2F1361-6641%2Faacba2}, doi = {10.1088/1361-6641/aacba2}, year = {2018}, date = {2018-06-01}, journal = {Semiconductor Science and Technology}, volume = {33}, number = {8}, pages = {085002}, publisher = {IOP Publishing}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Işık, Tuğba; Demir, Mustafa M: Medical Waste Treatment via Waste Electrospinning of PS. Fibers and Polymers, 19 (4), pp. 767–774, 2018, ISSN: 1875-0052. (Type: Journal Article | Abstract | Links | BibTeX) @article{isik2018b, title = {Medical Waste Treatment via Waste Electrospinning of PS}, author = {Tuğba Işık and Mustafa M Demir}, url = {https://doi.org/10.1007/s12221-018-1037-0}, doi = {10.1007/s12221-018-1037-0}, issn = {1875-0052}, year = {2018}, date = {2018-04-01}, journal = {Fibers and Polymers}, volume = {19}, number = {4}, pages = {767--774}, abstract = {Body fluid medical wastes are infectious clinical wastes (blood, saliva, urine) due to their high pathogenic content. Incineration is the most commonly used method in waste management that possess high water content along with molecularly dissolved species such as proteins. The process is costly; so that the removal of solid content dissolved in aqueous part by preliminary filtration can reduce the volume of the waste material. In this study, fibrous mats were prepared by electrospinning of PS wastes from DMF and THF solutions. Then they are employed in the removal of protein-based solid contents of body fluid medical wastes before their disposal. Two sources of PS waste (CD cover and Styrofoam) were employed along with virgin PS for comparison. The adsorption capacity of as-prepared electrospun fibers was examined for three model proteins: Bovine Serum Albumin (BSA), Myoglobin (MYO), and Trypsin (TRY). The fibers obtained from PS CD wastes have remarkably larger protein sorption capacities (particularly BSA) than the fibers obtained from virgin PS. XPS reveals the presence of CaCO3 domains in CD covers added into PS during their production steps probably to increase mechanical properties. There may be an electrostatic interaction between Ca2+ and the negatively charged groups of the protein. In this way, PS wastes could be converted to a beneficial secondary product by electrospinning and also resulting materials promises for the disposal of body fluid medical wastes. This may be one of the frontiers study on the removal of medical wastes by adsorbents produced via electrospinning of waste polymers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Body fluid medical wastes are infectious clinical wastes (blood, saliva, urine) due to their high pathogenic content. Incineration is the most commonly used method in waste management that possess high water content along with molecularly dissolved species such as proteins. The process is costly; so that the removal of solid content dissolved in aqueous part by preliminary filtration can reduce the volume of the waste material. In this study, fibrous mats were prepared by electrospinning of PS wastes from DMF and THF solutions. Then they are employed in the removal of protein-based solid contents of body fluid medical wastes before their disposal. Two sources of PS waste (CD cover and Styrofoam) were employed along with virgin PS for comparison. The adsorption capacity of as-prepared electrospun fibers was examined for three model proteins: Bovine Serum Albumin (BSA), Myoglobin (MYO), and Trypsin (TRY). The fibers obtained from PS CD wastes have remarkably larger protein sorption capacities (particularly BSA) than the fibers obtained from virgin PS. XPS reveals the presence of CaCO3 domains in CD covers added into PS during their production steps probably to increase mechanical properties. There may be an electrostatic interaction between Ca2+ and the negatively charged groups of the protein. In this way, PS wastes could be converted to a beneficial secondary product by electrospinning and also resulting materials promises for the disposal of body fluid medical wastes. This may be one of the frontiers study on the removal of medical wastes by adsorbents produced via electrospinning of waste polymers. |
Kandemir, A; Sahin, H: Janus single layers of : A first-principles study. Phys. Rev. B, 97 , pp. 155410, 2018. (Type: Journal Article | Links | BibTeX) @article{PhysRevB.97.155410, title = {Janus single layers of : A first-principles study}, author = {A Kandemir and H Sahin}, url = {https://link.aps.org/doi/10.1103/PhysRevB.97.155410}, doi = {10.1103/PhysRevB.97.155410}, year = {2018}, date = {2018-04-01}, journal = {Phys. Rev. B}, volume = {97}, pages = {155410}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Akbali, B; Topcu, G; Guner, T; Ozcan, M; Demir, M M; Sahin, H: CsPbBr3 perovskites: Theoretical and experimental investigation on water-assisted transition from nanowire formation to degradation. Phys. Rev. Materials, 2 , pp. 034601, 2018. (Type: Journal Article | Links | BibTeX) @article{PhysRevMaterials.2.034601, title = {CsPbBr3 perovskites: Theoretical and experimental investigation on water-assisted transition from nanowire formation to degradation}, author = {B Akbali and G Topcu and T Guner and M Ozcan and M M Demir and H Sahin}, url = {https://link.aps.org/doi/10.1103/PhysRevMaterials.2.034601}, doi = {10.1103/PhysRevMaterials.2.034601}, year = {2018}, date = {2018-03-01}, journal = {Phys. Rev. Materials}, volume = {2}, pages = {034601}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Gul, A; Bacaksiz, C; Unsal, E; Akbali, B; Tomak, A; Zareie, H M; Sahin, H: Theoretical and experimental investigation of conjugation of 1,6-hexanedithiol on MoS2. Materials Research Express, 5 (3), pp. 036415, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{gul2018, title = {Theoretical and experimental investigation of conjugation of 1,6-hexanedithiol on MoS2}, author = {A Gul and C Bacaksiz and E Unsal and B Akbali and A Tomak and H M Zareie and H Sahin}, url = {https://doi.org/10.1088%2F2053-1591%2Faab4a6}, doi = {10.1088/2053-1591/aab4a6}, year = {2018}, date = {2018-03-01}, journal = {Materials Research Express}, volume = {5}, number = {3}, pages = {036415}, publisher = {IOP Publishing}, abstract = {We report an experimental and theoretical investigation of conjugation of 1,6-Hexaneditihiol (HDT) on MoS2 which is prepared by mixing MoS2 structure and HDT molecules in proper solvent. Raman spectra and the calculated phonon bands reveal that the HDT molecules bind covalently to MoS2. Surface morphology of MoS2/HDT structure is changed upon conjugation of HDT on MoS2 and characterized by using Scanning Electron Microscope (SEM). Density Functional Theory (DFT) based calculations show that HOMO-LUMO band gap of HDT is altered after the conjugation and two-S binding (handle-like) configuration is energetically most favorable among three different structures. This study displays that the facile thiol functionalization process of MoS2 is promising strategy for obtaining solution processable MoS2.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report an experimental and theoretical investigation of conjugation of 1,6-Hexaneditihiol (HDT) on MoS2 which is prepared by mixing MoS2 structure and HDT molecules in proper solvent. Raman spectra and the calculated phonon bands reveal that the HDT molecules bind covalently to MoS2. Surface morphology of MoS2/HDT structure is changed upon conjugation of HDT on MoS2 and characterized by using Scanning Electron Microscope (SEM). Density Functional Theory (DFT) based calculations show that HOMO-LUMO band gap of HDT is altered after the conjugation and two-S binding (handle-like) configuration is energetically most favorable among three different structures. This study displays that the facile thiol functionalization process of MoS2 is promising strategy for obtaining solution processable MoS2. |
Güner, Tuğrul; Topçu, Gökhan; Savacı, Umut; Genç, Aziz; Turan, Servet; Sari, Emre; Demir, Mustafa M: Polarized emission from CsPbBr3 nanowire embedded-electrospun PU fibers. Nanotechnology, 29 (13), pp. 135202, 2018. (Type: Journal Article | Links | BibTeX) @article{guner2018, title = {Polarized emission from CsPbBr3 nanowire embedded-electrospun PU fibers}, author = {Tuğrul Güner and Gökhan Topçu and Umut Savacı and Aziz Genç and Servet Turan and Emre Sari and Mustafa M Demir}, url = {https://doi.org/10.1088%2F1361-6528%2Faaaaef}, doi = {10.1088/1361-6528/aaaaef}, year = {2018}, date = {2018-02-01}, journal = {Nanotechnology}, volume = {29}, number = {13}, pages = {135202}, publisher = {IOP Publishing}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Vakifahmetoglu, Cekdar; Zeydanli, Damla; Ozalp, Veli Cengiz; Borsa, Baris Ata; Soraru, Gian Domenico: Hierarchically porous polymer derived ceramics: A promising platform for multidrug delivery systems. MATERIALS & DESIGN, 140 , pp. 37-44, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000424943900005, title = {Hierarchically porous polymer derived ceramics: A promising platform for multidrug delivery systems}, author = {Cekdar Vakifahmetoglu and Damla Zeydanli and Veli Cengiz Ozalp and Baris Ata Borsa and Gian Domenico Soraru}, url = {https://www.sciencedirect.com/science/article/pii/S026412751731078X}, doi = {https://doi.org/10.1016/j.matdes.2017.11.047}, year = {2018}, date = {2018-02-01}, journal = {MATERIALS & DESIGN}, volume = {140}, pages = {37-44}, abstract = {Mesoporous silicon oxycarbide (SiOC) components were formed with the use of ``molecular spacer'' (a sacrificial vinyl-terminated linear siloxane which while decomposing during pyrolysis generates pores with size proportional to the molecular weight), followed by a post-pyrolysis etching treatment by hydrofluoric acid (HF) to obtain C-rich SiOC samples having additional micro-/mesoporosity and specific surface area reaching to 774 m(2)/g. The biocompatibility of the samples was validated by hemolysis test, and their cargo/drug loading capacities were studied by two different sized polypeptides as model molecules. SiOC particles showed less hemolysis compared to the reference material MCM-41. Similarly, the loading capacity and the release kinetics of bovine serum albumin (BSA) and vancomycin-loaded SiOC particles were improved compared to that of MCM-41. In the multi cargo loading/release capacity tests, done by using different size molecules, Bio2-HF and MCM-41 were loaded both with fluorescein and BSA. While a lagging time in fluorescein release was observed for MCM-41, the release kinetics of fluorescein and BSA was not affected when they are loaded together in the hierarchical pores of Bio2-HF, allowing the release of both large and small cargo molecules. The antimicrobial activity tests showed that Bio2-HF performed better than MCM-41 particles in improving bactericidal activity. (C) 2017 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mesoporous silicon oxycarbide (SiOC) components were formed with the use of ``molecular spacer'' (a sacrificial vinyl-terminated linear siloxane which while decomposing during pyrolysis generates pores with size proportional to the molecular weight), followed by a post-pyrolysis etching treatment by hydrofluoric acid (HF) to obtain C-rich SiOC samples having additional micro-/mesoporosity and specific surface area reaching to 774 m(2)/g. The biocompatibility of the samples was validated by hemolysis test, and their cargo/drug loading capacities were studied by two different sized polypeptides as model molecules. SiOC particles showed less hemolysis compared to the reference material MCM-41. Similarly, the loading capacity and the release kinetics of bovine serum albumin (BSA) and vancomycin-loaded SiOC particles were improved compared to that of MCM-41. In the multi cargo loading/release capacity tests, done by using different size molecules, Bio2-HF and MCM-41 were loaded both with fluorescein and BSA. While a lagging time in fluorescein release was observed for MCM-41, the release kinetics of fluorescein and BSA was not affected when they are loaded together in the hierarchical pores of Bio2-HF, allowing the release of both large and small cargo molecules. The antimicrobial activity tests showed that Bio2-HF performed better than MCM-41 particles in improving bactericidal activity. (C) 2017 Elsevier Ltd. All rights reserved. |
Isık, Tuğba; Demir, Mustafa M: Tailored electrospun fibers from waste polystyrene for high oil adsorption. Sustainable Materials and Technologies, 18 , pp. e00084, 2018, ISSN: 2214-9937. (Type: Journal Article | Abstract | Links | BibTeX) @article{isik2018e00084, title = {Tailored electrospun fibers from waste polystyrene for high oil adsorption}, author = {Tuğba Isık and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S2214993718301799}, doi = {https://doi.org/10.1016/j.susmat.2018.e00084}, issn = {2214-9937}, year = {2018}, date = {2018-01-01}, journal = {Sustainable Materials and Technologies}, volume = {18}, pages = {e00084}, abstract = {Recent ship accidents that resulted catastrophic oil spills necessitate producing environmentally friendly, cost-effective, and large-scale fabrication technology for oil- sorbent materials. Various material systems have been employed to fabricate sorbent materials; however, using fresh material components as adsorbent can lead to a secondary pollution. Therefore, recycling of plastics wastes for the fabrication of adsorbent material could be a wise approach to handle this environmental issue. In this study, foam-expanded polystyrene (f-PS), a commodity polymer used for insulation and packing materials, was electrospun from solution mixture of THF and DMF. Surface and interior porosity were achieved from individual fibers electrospun from a composition of DMF:THF (1:3) at 20-wt% of solid f-PS content. The resulting adsorbents exhibited a considerable hydrophobicity (WCA ≈ 120°) and oleophilicity (CA ≈ 10°), which can selectively adsorb both vegetable and engine oils from polluted waters. The porosity of the fibers has significant effect on the sorption capacity and separation efficiency up to 124 g/g and 99%, respectively. Thus, electrospun mats of the polystyrene wastes offer a promising adsorbent for the remediation of oily wastewaters.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent ship accidents that resulted catastrophic oil spills necessitate producing environmentally friendly, cost-effective, and large-scale fabrication technology for oil- sorbent materials. Various material systems have been employed to fabricate sorbent materials; however, using fresh material components as adsorbent can lead to a secondary pollution. Therefore, recycling of plastics wastes for the fabrication of adsorbent material could be a wise approach to handle this environmental issue. In this study, foam-expanded polystyrene (f-PS), a commodity polymer used for insulation and packing materials, was electrospun from solution mixture of THF and DMF. Surface and interior porosity were achieved from individual fibers electrospun from a composition of DMF:THF (1:3) at 20-wt% of solid f-PS content. The resulting adsorbents exhibited a considerable hydrophobicity (WCA ≈ 120°) and oleophilicity (CA ≈ 10°), which can selectively adsorb both vegetable and engine oils from polluted waters. The porosity of the fibers has significant effect on the sorption capacity and separation efficiency up to 124 g/g and 99%, respectively. Thus, electrospun mats of the polystyrene wastes offer a promising adsorbent for the remediation of oily wastewaters. |
Guner, Tugrul; Demir, Mustafa M: A Review on Halide Perovskites as Color Conversion Layers in White Light Emitting Diode Applications. physica status solidi (a), 215 (13), pp. 1800120, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002f, title = {A Review on Halide Perovskites as Color Conversion Layers in White Light Emitting Diode Applications}, author = {Tugrul Guner and Mustafa M Demir}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/pssa.201800120}, doi = {10.1002/pssa.201800120}, year = {2018}, date = {2018-01-01}, journal = {physica status solidi (a)}, volume = {215}, number = {13}, pages = {1800120}, abstract = {In the last decade, halide perovskites have attracted great interest due to many reasons, including their low cost, solution-processability, superior PL properties, broad range of color tunability, color purity, and defect tolerance, among others. They are in increasing demand for a wide range of applications, such as solar cells, light emitting diodes (LEDs), white LEDs (WLED), and lasers. Yellow phosphors have been heavily employed in solid-state lighting, since its illumination by blue yields white light with various optical features, such as high/low CRI, CCT, and luminous efficiency. However, phosphors as pigments are seldom found and are costly material. In this sense, halide perovskites may offer a promising alternative to phosphors for future solid-state lighting. In this study, the synthesis and optical properties of halide perovskites, as well as their application in WLED as a conversion layer are investigated.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the last decade, halide perovskites have attracted great interest due to many reasons, including their low cost, solution-processability, superior PL properties, broad range of color tunability, color purity, and defect tolerance, among others. They are in increasing demand for a wide range of applications, such as solar cells, light emitting diodes (LEDs), white LEDs (WLED), and lasers. Yellow phosphors have been heavily employed in solid-state lighting, since its illumination by blue yields white light with various optical features, such as high/low CRI, CCT, and luminous efficiency. However, phosphors as pigments are seldom found and are costly material. In this sense, halide perovskites may offer a promising alternative to phosphors for future solid-state lighting. In this study, the synthesis and optical properties of halide perovskites, as well as their application in WLED as a conversion layer are investigated. |
Guner, Tugrul; Akbali, Baris; Ozcan, Mehmet; Topcu, Gokhan; Demir, Mustafa M; Sahin, Hasan: Monitoring the Doping and Diffusion Characteristics of Mn Dopants in Cesium Lead Halide Perovskites. The Journal of Physical Chemistry C, 122 (21), pp. 11543-11549, 2018. (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.jpcc.8b02580, title = {Monitoring the Doping and Diffusion Characteristics of Mn Dopants in Cesium Lead Halide Perovskites}, author = {Tugrul Guner and Baris Akbali and Mehmet Ozcan and Gokhan Topcu and Mustafa M Demir and Hasan Sahin}, url = {https://doi.org/10.1021/acs.jpcc.8b02580}, doi = {10.1021/acs.jpcc.8b02580}, year = {2018}, date = {2018-01-01}, journal = {The Journal of Physical Chemistry C}, volume = {122}, number = {21}, pages = {11543-11549}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Topçu, Gökhan; Güner, Tuğrul; Demir, Mustafa M: Non-iridescent structural colors from uniform-sized SiO2 colloids. Photonics and Nanostructures - Fundamentals and Applications, 29 , pp. 22 - 29, 2018, ISSN: 1569-4410. (Type: Journal Article | Abstract | Links | BibTeX) @article{topcu201822, title = {Non-iridescent structural colors from uniform-sized SiO2 colloids}, author = {Gökhan Topçu and Tuğrul Güner and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S1569441017303036}, doi = {https://doi.org/10.1016/j.photonics.2018.01.002}, issn = {1569-4410}, year = {2018}, date = {2018-01-01}, journal = {Photonics and Nanostructures - Fundamentals and Applications}, volume = {29}, pages = {22 - 29}, abstract = {Structural colors have recently attracted interest from diverse fields of research due to their ease of fabrication and eco-friendliness. These types of colors are, in principle, achieved by periodically arranged submicron-diameter colloidal particles. The interaction of light with a structure containing long-range ordered colloidal particles leads to coloration; this usually varies depending on the angle of observation (iridescence). However, the majority of the applications demand constant color that is independent of the viewing angle (non-iridescence). In this work, silica colloids were obtained using the Stöber method at different sizes from 150 to 300 nm in an alcoholic dispersion. The casting of the dispersion on a substrate leaves behind a photonic crystal showing a colorful iridescent film. However, centrifugation and redispersion of the SiO2 particles into fresh solvent may cause the formation of small, aggregated silica domains in the new dispersion. The casting of this dispersion allows for the development of photonic glass, presumably due to the accumulation of aggregates showing stable colloidal film independent of viewing angle. Moreover, depending on the size of the silica colloids, non-iridescent photonic glasses with various colors (violet, blue, green, and orange) are obtained.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Structural colors have recently attracted interest from diverse fields of research due to their ease of fabrication and eco-friendliness. These types of colors are, in principle, achieved by periodically arranged submicron-diameter colloidal particles. The interaction of light with a structure containing long-range ordered colloidal particles leads to coloration; this usually varies depending on the angle of observation (iridescence). However, the majority of the applications demand constant color that is independent of the viewing angle (non-iridescence). In this work, silica colloids were obtained using the Stöber method at different sizes from 150 to 300 nm in an alcoholic dispersion. The casting of the dispersion on a substrate leaves behind a photonic crystal showing a colorful iridescent film. However, centrifugation and redispersion of the SiO2 particles into fresh solvent may cause the formation of small, aggregated silica domains in the new dispersion. The casting of this dispersion allows for the development of photonic glass, presumably due to the accumulation of aggregates showing stable colloidal film independent of viewing angle. Moreover, depending on the size of the silica colloids, non-iridescent photonic glasses with various colors (violet, blue, green, and orange) are obtained. |
Demirkurt, M; Olcer, Y A; Demir, M M; Eroglu, A E: Electrospun polystyrene fibers knitted around imprinted acrylate microspheres as sorbent for paraben derivatives. Analytica Chimica Acta, 1014 , pp. 1 - 9, 2018, ISSN: 0003-2670. (Type: Journal Article | Abstract | Links | BibTeX) @article{demirkurt20181, title = {Electrospun polystyrene fibers knitted around imprinted acrylate microspheres as sorbent for paraben derivatives}, author = {M Demirkurt and Y A Olcer and M M Demir and A E Eroglu}, url = {http://www.sciencedirect.com/science/article/pii/S0003267018302058}, doi = {https://doi.org/10.1016/j.aca.2018.02.016}, issn = {0003-2670}, year = {2018}, date = {2018-01-01}, journal = {Analytica Chimica Acta}, volume = {1014}, pages = {1 - 9}, abstract = {Parabens are used as antimicrobial preservatives in food, cosmetic products and pharmaceuticals regardless of their endocrine disrupting effect. In this study, highly selective molecular imprinted polymers (MIPs) were synthesized in submicron-sizes and converted to an SPME fiber coating through electrospinning process in order to determine parabens in water samples. Conversion of MIP to a fiber is achieved via creation of spacial knitting around MIP by polystyrene. The selectivity and extraction ability of the fibers were compared with the commercial fibers and the corresponding non-imprinted polymer (NIP) coated fiber. The coated fiber showed better extraction ability among them. Also, the results revealed that the fiber has better selectivity for benzyl paraben and the other structurally-related compounds, such as methyl and propyl paraben. Extraction efficiency of prepared fibers for three parabens has been tested by spiking bottled, tap and sea water samples. The recoveries changed between 92.2 ± 0.8 and 99.8 ± 0.1 for three different water types. This method could be used for selective and sensitive determination of parabens in aqueous samples.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Parabens are used as antimicrobial preservatives in food, cosmetic products and pharmaceuticals regardless of their endocrine disrupting effect. In this study, highly selective molecular imprinted polymers (MIPs) were synthesized in submicron-sizes and converted to an SPME fiber coating through electrospinning process in order to determine parabens in water samples. Conversion of MIP to a fiber is achieved via creation of spacial knitting around MIP by polystyrene. The selectivity and extraction ability of the fibers were compared with the commercial fibers and the corresponding non-imprinted polymer (NIP) coated fiber. The coated fiber showed better extraction ability among them. Also, the results revealed that the fiber has better selectivity for benzyl paraben and the other structurally-related compounds, such as methyl and propyl paraben. Extraction efficiency of prepared fibers for three parabens has been tested by spiking bottled, tap and sea water samples. The recoveries changed between 92.2 ± 0.8 and 99.8 ± 0.1 for three different water types. This method could be used for selective and sensitive determination of parabens in aqueous samples. |
Çelik, Aslı; Topçu, Gökhan; Isik, Tuğba; Baba, Alper; Horzum, Nesrin; Demir, Mustafa M: Investigation of Lithium Sorption Efficiency Using SWCNT Functionalized Electrospun Fiber Mats from the Hypersaline Geothermal Brine. Applied Electromagnetic Engineering for Advanced Materials from Macro-to Nanoscale under Static-to Shock Loading, pp. 121–126, Trans Tech Publications, 2018. (Type: Inproceedings | Abstract | Links | BibTeX) @inproceedings{celik2018, title = {Investigation of Lithium Sorption Efficiency Using SWCNT Functionalized Electrospun Fiber Mats from the Hypersaline Geothermal Brine}, author = {Aslı Çelik and Gökhan Topçu and Tuğba Isik and Alper Baba and Nesrin Horzum and Mustafa M Demir}, doi = {10.4028/www.scientific.net/MSF.915.121}, year = {2018}, date = {2018-01-01}, booktitle = {Applied Electromagnetic Engineering for Advanced Materials from Macro-to Nanoscale under Static-to Shock Loading}, volume = {915}, pages = {121--126}, publisher = {Trans Tech Publications}, series = {Materials Science Forum}, abstract = {Geothermal mining from brines becomes increasingly important with the increasing demand for rare earth elements in various engineering applications. Geothermal fluids contain valuable minerals and metals such as silica, zinc, lithium, and other materials that can be processed to recover these products. Solution mining by nature is challenging because of variable composition as well as the concentration of the interfering ions, particularly calcium and magnesium, and the presence of interfering ions increases the recovery costs requiring additional steps. The aim of this study is the fabrication of single-walled carbon nanotube functionalized electrospun chitosan, poly (methyl methacrylate) (PMMA), and polyacrylonitrile (PAN) fiber mats. Effect of polymer type, dilution factor, and surface modification on the sorption of lithium ( QUOTE ) ions was investigated. The maximum sorption performance was obtained with SWCNT functionalized PAN (15 wt%) fiber mats and they have sorption percentage as 55% at diluted (1/100) brine samples.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Geothermal mining from brines becomes increasingly important with the increasing demand for rare earth elements in various engineering applications. Geothermal fluids contain valuable minerals and metals such as silica, zinc, lithium, and other materials that can be processed to recover these products. Solution mining by nature is challenging because of variable composition as well as the concentration of the interfering ions, particularly calcium and magnesium, and the presence of interfering ions increases the recovery costs requiring additional steps. The aim of this study is the fabrication of single-walled carbon nanotube functionalized electrospun chitosan, poly (methyl methacrylate) (PMMA), and polyacrylonitrile (PAN) fiber mats. Effect of polymer type, dilution factor, and surface modification on the sorption of lithium ( QUOTE ) ions was investigated. The maximum sorption performance was obtained with SWCNT functionalized PAN (15 wt%) fiber mats and they have sorption percentage as 55% at diluted (1/100) brine samples. |
İncel, Anıl; Demir, Mustafa M: Triboluminescent composite microspheres consisting of alginate and EuD4TEA crystals. Sensors and Actuators A: Physical, 269 , pp. 556 - 562, 2018, ISSN: 0924-4247. (Type: Journal Article | Abstract | Links | BibTeX) @article{incel2018556, title = {Triboluminescent composite microspheres consisting of alginate and EuD4TEA crystals}, author = {Anıl İncel and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S0924424717317727}, doi = {https://doi.org/10.1016/j.sna.2017.12.023}, issn = {0924-4247}, year = {2018}, date = {2018-01-01}, journal = {Sensors and Actuators A: Physical}, volume = {269}, pages = {556 - 562}, abstract = {Alginate is utilized to obtain luminescent composite microspheres containing europium tetrakis (dibenzoylmethide) triethylammonium (EuD4TEA) triboluminescent (TL) crystals. Na alginate is initially treated with Ca(II) and then Eu (III) so that physically-crosslinked alginate microspheres were obtained. EuD4TEA crystals are precipitated in situ on the surface of the spheres upon treatment with dibenzoylmethane (DBM) and triethylamine (TEA). The EuD4TEA/alginate composite spheres are swollen in aqueous system, the diameter of the microspheres increases from 180 up to 405 μm in 48 h. TL intensity of the spheres swollen in 1 h decreases 4 folds compared to dry spheres; however, it systematically increases as the swelling time is extended step-wise to 48 h. Swelling may develop structural homogenity in the microsphere that supresses the optical scattering and may lead to better transmittance of the TL signal.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Alginate is utilized to obtain luminescent composite microspheres containing europium tetrakis (dibenzoylmethide) triethylammonium (EuD4TEA) triboluminescent (TL) crystals. Na alginate is initially treated with Ca(II) and then Eu (III) so that physically-crosslinked alginate microspheres were obtained. EuD4TEA crystals are precipitated in situ on the surface of the spheres upon treatment with dibenzoylmethane (DBM) and triethylamine (TEA). The EuD4TEA/alginate composite spheres are swollen in aqueous system, the diameter of the microspheres increases from 180 up to 405 μm in 48 h. TL intensity of the spheres swollen in 1 h decreases 4 folds compared to dry spheres; however, it systematically increases as the swelling time is extended step-wise to 48 h. Swelling may develop structural homogenity in the microsphere that supresses the optical scattering and may lead to better transmittance of the TL signal. |
Sevim, Koray; Sevinçli, Hâldun: Tuning thermal transport in graphene via combinations of molecular antiresonances. Carbon, 140 , pp. 603 - 609, 2018, ISSN: 0008-6223. (Type: Journal Article | Abstract | Links | BibTeX) @article{sevim2018603, title = {Tuning thermal transport in graphene via combinations of molecular antiresonances}, author = {Koray Sevim and Hâldun Sevinçli}, url = {http://www.sciencedirect.com/science/article/pii/S000862231830784X}, doi = {https://doi.org/10.1016/j.carbon.2018.08.050}, issn = {0008-6223}, year = {2018}, date = {2018-01-01}, journal = {Carbon}, volume = {140}, pages = {603 - 609}, abstract = {We propose a method to engineer the phonon thermal transport properties of low dimensional systems. The method relies on introducing a predetermined combination of molecular adsorbates, which give rise to antiresonances at frequencies specific to the molecular species. Despite their dissimilar transmission spectra, thermal resistances due to individual molecules remain almost the same for all species. On the other hand, thermal resistance due to combinations of different species are not additive and show large differences depending on the species. Using a toy model, the physics underlying the violation of resistance summation rule is investigated. It is demonstrated that equivalent resistance of two scatterers having the same resistances can be close to the sum of the constituents or ∼ 70% of it depending on the relative positions of the antiresonances. The relative positions of the antiresonances determine the net change in transmission, therefore the equivalent resistance. Since the entire spectrum is involved in phonon spectrum changes in different parts of the spectrum become important. Performing extensive first-principles based computations, we show that these distinctive attributes of phonon transport can be useful to tailor the thermal transport through low dimensional materials, especially for thermoelectric and thermal management applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We propose a method to engineer the phonon thermal transport properties of low dimensional systems. The method relies on introducing a predetermined combination of molecular adsorbates, which give rise to antiresonances at frequencies specific to the molecular species. Despite their dissimilar transmission spectra, thermal resistances due to individual molecules remain almost the same for all species. On the other hand, thermal resistance due to combinations of different species are not additive and show large differences depending on the species. Using a toy model, the physics underlying the violation of resistance summation rule is investigated. It is demonstrated that equivalent resistance of two scatterers having the same resistances can be close to the sum of the constituents or ∼ 70% of it depending on the relative positions of the antiresonances. The relative positions of the antiresonances determine the net change in transmission, therefore the equivalent resistance. Since the entire spectrum is involved in phonon spectrum changes in different parts of the spectrum become important. Performing extensive first-principles based computations, we show that these distinctive attributes of phonon transport can be useful to tailor the thermal transport through low dimensional materials, especially for thermoelectric and thermal management applications. |
Sandonas, Leonardo Medrano; Sevinçli, Hâldun; Gutierrez, Rafael; Cuniberti, Gianaurelio: First-Principle-Based Phonon Transport Properties of Nanoscale Graphene Grain Boundaries. Advanced Science, 5 (2), pp. 1700365, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/advs.201700365, title = {First-Principle-Based Phonon Transport Properties of Nanoscale Graphene Grain Boundaries}, author = {Leonardo Medrano Sandonas and Hâldun Sevinçli and Rafael Gutierrez and Gianaurelio Cuniberti}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.201700365}, doi = {10.1002/advs.201700365}, year = {2018}, date = {2018-01-01}, journal = {Advanced Science}, volume = {5}, number = {2}, pages = {1700365}, abstract = {Abstract The integrity of phonon transport properties of large graphene (linear and curved) grain boundaries (GBs) is investigated under the influence of structural and dynamical disorder. To do this, density functional tight-binding (DFTB) method is combined with atomistic Green's function technique. The results show that curved GBs have lower thermal conductance than linear GBs. Its magnitude depends on the length of the curvature and out-of-plane structural distortions at the boundary, having stronger influence the latter one. Moreover, it is found that by increasing the defects at the boundary, the transport properties can strongly be reduced in comparison to the effect produced by heating up the boundary region. This is due to the large reduction of the phonon transmission for in-plane and out-of-plane vibrational modes after increasing the structural disorder in the GBs.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract The integrity of phonon transport properties of large graphene (linear and curved) grain boundaries (GBs) is investigated under the influence of structural and dynamical disorder. To do this, density functional tight-binding (DFTB) method is combined with atomistic Green's function technique. The results show that curved GBs have lower thermal conductance than linear GBs. Its magnitude depends on the length of the curvature and out-of-plane structural distortions at the boundary, having stronger influence the latter one. Moreover, it is found that by increasing the defects at the boundary, the transport properties can strongly be reduced in comparison to the effect produced by heating up the boundary region. This is due to the large reduction of the phonon transmission for in-plane and out-of-plane vibrational modes after increasing the structural disorder in the GBs. |
Zeydanli, Damla; Akman, Suleyman; Vakifahmetoglu, Cekdar: Polymer-derived ceramic adsorbent for pollutant removal from water. Journal of the American Ceramic Society, 101 (6), pp. 2258-2265, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1111/jace.15423, title = {Polymer-derived ceramic adsorbent for pollutant removal from water}, author = {Damla Zeydanli and Suleyman Akman and Cekdar Vakifahmetoglu}, url = {https://ceramics.onlinelibrary.wiley.com/doi/abs/10.1111/jace.15423}, doi = {10.1111/jace.15423}, year = {2018}, date = {2018-01-01}, journal = {Journal of the American Ceramic Society}, volume = {101}, number = {6}, pages = {2258-2265}, abstract = {Abstract Polymer-derived ceramic components (SiOC, sample W) were produced from preceramic polymer mixture and a catalyst. After curing and pyrolysis, some of the samples etched by hydrofluoric acid to obtain carbonaceous SiOC (C-rich SiOC, sample W-HF). W and W-HF were tested as an adsorbent material to remove both heavy-metal ions (Cr (III), Pb (III), and Cd (II)) and cationic dyes (Methylene Blue (MB), Rhodamine B (RB), and Crystal Violet (CV)) from aqueous solutions. HF-treated high surface area SiOC samples had quite high adsorption affinity for cationic dyes. According the Langmuir isotherm model the maximum dye uptake values were found to be around to 50 mg/g for sample W, whereas those for sample W-HF ranged from 104 to 186 mg/g. Regeneration studies were conducted both by heat treatment and leaching, high recovery yields (always above 97%) of MB adsorption were obtained.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract Polymer-derived ceramic components (SiOC, sample W) were produced from preceramic polymer mixture and a catalyst. After curing and pyrolysis, some of the samples etched by hydrofluoric acid to obtain carbonaceous SiOC (C-rich SiOC, sample W-HF). W and W-HF were tested as an adsorbent material to remove both heavy-metal ions (Cr (III), Pb (III), and Cd (II)) and cationic dyes (Methylene Blue (MB), Rhodamine B (RB), and Crystal Violet (CV)) from aqueous solutions. HF-treated high surface area SiOC samples had quite high adsorption affinity for cationic dyes. According the Langmuir isotherm model the maximum dye uptake values were found to be around to 50 mg/g for sample W, whereas those for sample W-HF ranged from 104 to 186 mg/g. Regeneration studies were conducted both by heat treatment and leaching, high recovery yields (always above 97%) of MB adsorption were obtained. |
Demirkurt, Begüm; Akdogan, Yasar: Development of an Ionic Liquid Based Method for the Preparation of Albumin Nanoparticles. ChemistrySelect, 3 (34), pp. 9940-9945, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/slct.201801648, title = {Development of an Ionic Liquid Based Method for the Preparation of Albumin Nanoparticles}, author = {Begüm Demirkurt and Yasar Akdogan}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/slct.201801648}, doi = {10.1002/slct.201801648}, year = {2018}, date = {2018-01-01}, journal = {ChemistrySelect}, volume = {3}, number = {34}, pages = {9940-9945}, abstract = {Abstract Albumin based nanocarriers have been widely used in drug delivery studies. Here, we developed a water-in-ionic liquid (IL) emulsion-like method to prepare bovine serum albumin (BSA) nanoparticles as alternative to the traditional organic solvents containing techniques. Conformational changes of albumin induced by the imidazolium based ILs at the water-IL interface triggers the BSA nanoparticle formation. The albumin nanoparticle formation are dependent on the experimental parameters and the hydophobicity of the IL. At pH 9.0, using 1.3%wt of BSA in water/1-butyl-3-methyl imidazolium tetrafluoroborate (BmimBF4) (50/50 mol%) and TX-100/butanol surfactant mixture yields uniformly distributed 200 nm average sized BSA nanoparticles. Different than BmimBF4, using a more hydrophilic IL, EmimBF4 yielded albumin aggregates. Instead, using a more hydrophobic IL, HmimBF4 produced albumin nanoparticles but a non-uniform size distribution was obtained. These results indicate that the ionic liquids called green and designer solvents can be also used to synthesize albumin nanoparticles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract Albumin based nanocarriers have been widely used in drug delivery studies. Here, we developed a water-in-ionic liquid (IL) emulsion-like method to prepare bovine serum albumin (BSA) nanoparticles as alternative to the traditional organic solvents containing techniques. Conformational changes of albumin induced by the imidazolium based ILs at the water-IL interface triggers the BSA nanoparticle formation. The albumin nanoparticle formation are dependent on the experimental parameters and the hydophobicity of the IL. At pH 9.0, using 1.3%wt of BSA in water/1-butyl-3-methyl imidazolium tetrafluoroborate (BmimBF4) (50/50 mol%) and TX-100/butanol surfactant mixture yields uniformly distributed 200 nm average sized BSA nanoparticles. Different than BmimBF4, using a more hydrophilic IL, EmimBF4 yielded albumin aggregates. Instead, using a more hydrophobic IL, HmimBF4 produced albumin nanoparticles but a non-uniform size distribution was obtained. These results indicate that the ionic liquids called green and designer solvents can be also used to synthesize albumin nanoparticles. |
Göksel, Yaman; i, İklima K; Akdogan, Yasar: Spontaneous Adhesion of DOPA and Tryptophan Functionalized PEG to Polystyrene Nanobeads: An EPR Study. Applied Electromagnetic Engineering for Advanced Materials from Macro-to Nanoscale under Static-to Shock Loading, pp. 243–247, Trans Tech Publications, 2018. (Type: Inproceedings | Abstract | Links | BibTeX) @inproceedings{goksel2018, title = {Spontaneous Adhesion of DOPA and Tryptophan Functionalized PEG to Polystyrene Nanobeads: An EPR Study}, author = {Yaman Göksel and İklima K i and Yasar Akdogan}, doi = {10.4028/www.scientific.net/MSF.915.243}, year = {2018}, date = {2018-01-01}, booktitle = {Applied Electromagnetic Engineering for Advanced Materials from Macro-to Nanoscale under Static-to Shock Loading}, volume = {915}, pages = {243--247}, publisher = {Trans Tech Publications}, series = {Materials Science Forum}, abstract = {Wet adhesion is achieved by mussels so naturally. Their adhesion mechanism has inspired scientists to obtain wet adhesives for a long time. The amino acid 3,4-dihydroxyphenylalanine (DOPA) produced by mussels adheres to different types of surfaces and also contributes to cohesive interactions. Here, we showed the spontaneous adhesion of DOPA functionalized four armed poly (ethylene glycol) (PEG) polymer to spin labeled polystyrene (SL-PS) nanosurfaces by electron paramagnetic resonance (EPR) spectroscopy. In addition to DOPA, adhesion property of another amino acid of tryptophan (Trp) was studied. Trp attached four armed PEG polymers did not adhere to the surface of SL-PS in the force free condition. However, two armed DOPA and two armed Trp functionalized PEG adhere to the PS.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Wet adhesion is achieved by mussels so naturally. Their adhesion mechanism has inspired scientists to obtain wet adhesives for a long time. The amino acid 3,4-dihydroxyphenylalanine (DOPA) produced by mussels adheres to different types of surfaces and also contributes to cohesive interactions. Here, we showed the spontaneous adhesion of DOPA functionalized four armed poly (ethylene glycol) (PEG) polymer to spin labeled polystyrene (SL-PS) nanosurfaces by electron paramagnetic resonance (EPR) spectroscopy. In addition to DOPA, adhesion property of another amino acid of tryptophan (Trp) was studied. Trp attached four armed PEG polymers did not adhere to the surface of SL-PS in the force free condition. However, two armed DOPA and two armed Trp functionalized PEG adhere to the PS. |
Badalov, S V; Kandemir, A; Sahin, H: Monolayer AsTe2: Stable Robust Metal in 2D, 1D and 0D. ChemPhysChem, 19 (17), pp. 2176-2182, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/cphc.201800473, title = {Monolayer AsTe2: Stable Robust Metal in 2D, 1D and 0D}, author = {S V Badalov and A Kandemir and H Sahin}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/cphc.201800473}, doi = {10.1002/cphc.201800473}, year = {2018}, date = {2018-01-01}, journal = {ChemPhysChem}, volume = {19}, number = {17}, pages = {2176-2182}, abstract = {Abstract The structural, phononic, and electronic properties of the monolayer structures of AsTe2 are characterized by performing density functional theory (DFT) calculations. Total energy optimization and phonon calculations reveal that single layers of the 2H-AsTe2 and 1T-AsTe2 phases form dynamically stable crystal structures. Electronic structure analysis also shows that both 2H and 1T phases have nonmagnetic metallic character. It is also predicted that the metallic nature of the ultra-thin both 2H-AsTe2 and 1T-AsTe2 structures remain unchanged even under high biaxial strain values. For further examination of the dimensionality effect in the robust metallicity in 2D AsTe2 phases, electronic characteristics of 1D nanoribbons and 0D quantum dots are also investigated. It is found that independent from the dimension and crystallographic orientations 0D and 1D structures of 2H- and 1T-AsTe2 structures have metallic behavior. It is found that single layers of AsTe2 are quite promising materials for nanodevice applications owing to the robust metallic character.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract The structural, phononic, and electronic properties of the monolayer structures of AsTe2 are characterized by performing density functional theory (DFT) calculations. Total energy optimization and phonon calculations reveal that single layers of the 2H-AsTe2 and 1T-AsTe2 phases form dynamically stable crystal structures. Electronic structure analysis also shows that both 2H and 1T phases have nonmagnetic metallic character. It is also predicted that the metallic nature of the ultra-thin both 2H-AsTe2 and 1T-AsTe2 structures remain unchanged even under high biaxial strain values. For further examination of the dimensionality effect in the robust metallicity in 2D AsTe2 phases, electronic characteristics of 1D nanoribbons and 0D quantum dots are also investigated. It is found that independent from the dimension and crystallographic orientations 0D and 1D structures of 2H- and 1T-AsTe2 structures have metallic behavior. It is found that single layers of AsTe2 are quite promising materials for nanodevice applications owing to the robust metallic character. |
Kandemir, A; Peeters, F M; Sahin, H: Monitoring the effect of asymmetrical vertical strain on Janus single layers of MoSSe via vibrational spectrum. The Journal of Chemical Physics, 149 (8), pp. 084707, 2018. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/1.5043207, title = {Monitoring the effect of asymmetrical vertical strain on Janus single layers of MoSSe via vibrational spectrum}, author = {A Kandemir and F M Peeters and H Sahin}, url = {https://doi.org/10.1063/1.5043207}, doi = {10.1063/1.5043207}, year = {2018}, date = {2018-01-01}, journal = {The Journal of Chemical Physics}, volume = {149}, number = {8}, pages = {084707}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Kandemir, A; Sahin, H: Bilayers of Janus WSSe: monitoring the stacking type via the vibrational spectrum. Phys. Chem. Chem. Phys., 20 , pp. 17380-17386, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{C8CP02802H, title = {Bilayers of Janus WSSe: monitoring the stacking type via the vibrational spectrum}, author = {A Kandemir and H Sahin}, url = {http://dx.doi.org/10.1039/C8CP02802H}, doi = {10.1039/C8CP02802H}, year = {2018}, date = {2018-01-01}, journal = {Phys. Chem. Chem. Phys.}, volume = {20}, pages = {17380-17386}, publisher = {The Royal Society of Chemistry}, abstract = {Motivated by the recent successful synthesis of Janus type single layers of transition metal dichalcogenides, we investigate the stability, vibrational and electronic properties of the Janus single layer structure of WSSe and its bilayers by means of density functional theory. The structural and vibrational analysis show that the Janus single layer of WSSe forms a dynamically stable structure in the 2H phase. Owing to its non-centrosymmetric structure, the Janus WSSe single layer has two in-plane (E) and two out-of-plane (A) Raman active phonon modes. The eigen-frequencies of the prominent Raman active modes are calculated to be 277 (A) and 322 (E) cm−1. Similar to single layer WS2 and WSe2, Janus WSSe is a direct band gap semiconductor that has two electronically different faces. In addition, the possible bilayer stacking orders of the Janus WSSe single layers are investigated. It is found that there are 3 stacking types of bilayer Janus WSSe and each stacking type has distinctive Raman characteristics in its vibrational spectrum. Our results show that thanks to the vibrational characteristics, which stem from the distinctive interlayer interactions at different sides, the stability and stacking types of the bilayer of WSSe Janus structure can be monitored.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Motivated by the recent successful synthesis of Janus type single layers of transition metal dichalcogenides, we investigate the stability, vibrational and electronic properties of the Janus single layer structure of WSSe and its bilayers by means of density functional theory. The structural and vibrational analysis show that the Janus single layer of WSSe forms a dynamically stable structure in the 2H phase. Owing to its non-centrosymmetric structure, the Janus WSSe single layer has two in-plane (E) and two out-of-plane (A) Raman active phonon modes. The eigen-frequencies of the prominent Raman active modes are calculated to be 277 (A) and 322 (E) cm−1. Similar to single layer WS2 and WSe2, Janus WSSe is a direct band gap semiconductor that has two electronically different faces. In addition, the possible bilayer stacking orders of the Janus WSSe single layers are investigated. It is found that there are 3 stacking types of bilayer Janus WSSe and each stacking type has distinctive Raman characteristics in its vibrational spectrum. Our results show that thanks to the vibrational characteristics, which stem from the distinctive interlayer interactions at different sides, the stability and stacking types of the bilayer of WSSe Janus structure can be monitored. |
Sotthewes, Kai; Kap, Özlem; Wu, Hairong; Thompson, Damien; Huskens, Jurriaan; Zandvliet, Harold J W: Ordering of Air-Oxidized Decanethiols on Au(111). The Journal of Physical Chemistry C, 122 (15), pp. 8430-8436, 2018. (Type: Journal Article | Links | BibTeX) @article{ozlemkap2018, title = {Ordering of Air-Oxidized Decanethiols on Au(111)}, author = {Kai Sotthewes and Özlem Kap and Hairong Wu and Damien Thompson and Jurriaan Huskens and Harold J W Zandvliet}, url = {https://doi.org/10.1021/acs.jpcc.8b01389}, doi = {10.1021/acs.jpcc.8b01389}, year = {2018}, date = {2018-01-01}, journal = {The Journal of Physical Chemistry C}, volume = {122}, number = {15}, pages = {8430-8436}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sayar, Melike; Karakuş, Erman; Güner, Tuğrul; Yildiz, Busra; Yildiz, Umit Hakan; Emrullahoğlu, Mustafa: A BODIPY-Based Fluorescent Probe to Visually Detect Phosgene: Toward the Development of a Handheld Phosgene Detector. Chemistry – A European Journal, 24 (13), pp. 3136-3140, 2018. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/chem.201705613, title = {A BODIPY-Based Fluorescent Probe to Visually Detect Phosgene: Toward the Development of a Handheld Phosgene Detector}, author = {Melike Sayar and Erman Karakuş and Tuğrul Güner and Busra Yildiz and Umit Hakan Yildiz and Mustafa Emrullahoğlu}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201705613}, doi = {10.1002/chem.201705613}, year = {2018}, date = {2018-01-01}, journal = {Chemistry – A European Journal}, volume = {24}, number = {13}, pages = {3136-3140}, abstract = {Abstract A boron-dipyrromethene (BODIPY)-based fluorescent probe with a phosgene-specific reactive motif shows remarkable selectivity toward phosgene, in the presence of which the nonfluorescent dye rapidly transforms into a new structure and induces a fluorescent response clearly observable to the naked eye under ultraviolet light. Given that dynamic, a prototypical handheld phosgene detector with a promising sensing capability that expedites the detection of gaseous phosgene without sophisticated instrumentation was developed. The proposed method using the handheld detector involves a rapid response period suitable for issuing early warnings during emergency situations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract A boron-dipyrromethene (BODIPY)-based fluorescent probe with a phosgene-specific reactive motif shows remarkable selectivity toward phosgene, in the presence of which the nonfluorescent dye rapidly transforms into a new structure and induces a fluorescent response clearly observable to the naked eye under ultraviolet light. Given that dynamic, a prototypical handheld phosgene detector with a promising sensing capability that expedites the detection of gaseous phosgene without sophisticated instrumentation was developed. The proposed method using the handheld detector involves a rapid response period suitable for issuing early warnings during emergency situations. |
Mobaraki, Arash; Kandemir, Ali; Yapicioglu, Haluk; Gülseren, Oğuz; Sevik, Cem: Validation of inter-atomic potential for WS2 and WSe2 crystals through assessment of thermal transport properties. Computational Materials Science, 144 , pp. 92 - 98, 2018, ISSN: 0927-0256. (Type: Journal Article | Abstract | Links | BibTeX) @article{mobaraki201892, title = {Validation of inter-atomic potential for WS2 and WSe2 crystals through assessment of thermal transport properties}, author = {Arash Mobaraki and Ali Kandemir and Haluk Yapicioglu and Oğuz Gülseren and Cem Sevik}, url = {http://www.sciencedirect.com/science/article/pii/S0927025617306900}, doi = {https://doi.org/10.1016/j.commatsci.2017.12.005}, issn = {0927-0256}, year = {2018}, date = {2018-01-01}, journal = {Computational Materials Science}, volume = {144}, pages = {92 - 98}, abstract = {In recent years, transition metal dichalcogenides (TMDs) displaying astonishing properties are emerged as a new class of two-dimensional layered materials. The understanding and characterization of thermal transport in these materials are crucial for efficient engineering of 2D TMD materials for applications such as thermoelectric devices or overcoming general overheating issues. In this work, we obtain accurate Stillinger-Weber type empirical potential parameter sets for single-layer WS2 and WSe2 crystals by utilizing particle swarm optimization, a stochastic search algorithm. For both systems, our results are quite consistent with first-principles calculations in terms of bond distances, lattice parameters, elastic constants and vibrational properties. Using the generated potentials, we investigate the effect of temperature on phonon energies and phonon linewidth by employing spectral energy density analysis. We compare the calculated frequency shift with respect to temperature with corresponding experimental data, clearly demonstrating the accuracy of the generated inter-atomic potentials in this study. Also, we evaluate the lattice thermal conductivities of these materials by means of classical molecular dynamics simulations. The predicted thermal properties are in very good agreement with the ones calculated from first-principles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In recent years, transition metal dichalcogenides (TMDs) displaying astonishing properties are emerged as a new class of two-dimensional layered materials. The understanding and characterization of thermal transport in these materials are crucial for efficient engineering of 2D TMD materials for applications such as thermoelectric devices or overcoming general overheating issues. In this work, we obtain accurate Stillinger-Weber type empirical potential parameter sets for single-layer WS2 and WSe2 crystals by utilizing particle swarm optimization, a stochastic search algorithm. For both systems, our results are quite consistent with first-principles calculations in terms of bond distances, lattice parameters, elastic constants and vibrational properties. Using the generated potentials, we investigate the effect of temperature on phonon energies and phonon linewidth by employing spectral energy density analysis. We compare the calculated frequency shift with respect to temperature with corresponding experimental data, clearly demonstrating the accuracy of the generated inter-atomic potentials in this study. Also, we evaluate the lattice thermal conductivities of these materials by means of classical molecular dynamics simulations. The predicted thermal properties are in very good agreement with the ones calculated from first-principles. |
Aydin, H; Bacaksiz, C; Yagmurcukardes, N; Karakaya, C; Mermer, O; Can, M; Senger, R T; Sahin, H; Selamet, Y: Experimental and computational investigation of graphene/SAMs/n-Si Schottky diodes. Applied Surface Science, 428 , pp. 1010 - 1017, 2018, ISSN: 0169-4332. (Type: Journal Article | Abstract | Links | BibTeX) @article{aydin20181010, title = {Experimental and computational investigation of graphene/SAMs/n-Si Schottky diodes}, author = {H Aydin and C Bacaksiz and N Yagmurcukardes and C Karakaya and O Mermer and M Can and R T Senger and H Sahin and Y Selamet}, url = {http://www.sciencedirect.com/science/article/pii/S0169433217328520}, doi = {https://doi.org/10.1016/j.apsusc.2017.09.204}, issn = {0169-4332}, year = {2018}, date = {2018-01-01}, journal = {Applied Surface Science}, volume = {428}, pages = {1010 - 1017}, abstract = {We have investigated the effect of two different self-assembled monolayers (SAMs) on electrical characteristics of bilayer graphene (BLG)/n-Si Schottky diodes. Novel 4″bis(diphenylamino)-1, 1′:3″-terphenyl-5′ carboxylic acids (TPA) and 4,4-di-9H-carbazol-9-yl-1,1′:3′1′-terphenyl-5′ carboxylic acid (CAR) aromatic SAMs have been used to modify n-Si surfaces. Cyclic voltammetry (CV) and Kelvin probe force microscopy (KPFM) results have been evaluated to verify the modification of n-Si surface. The current–voltage (I–V) characteristics of bare and SAMs modified devices show rectification behaviour verifying a Schottky junction at the interface. The ideality factors (n) from ln(I)–V dependences were determined as 2.13, 1.96 and 2.07 for BLG/n-Si, BLG/TPA/n-Si and BLG/CAR/n-Si Schottky diodes, respectively. In addition, Schottky barrier height (SBH) and series resistance (Rs) of SAMs modified diodes were decreased compared to bare diode due to the formation of a compatible interface between graphene and Si as well as π–π interaction between aromatic SAMs and graphene. The CAR-based device exhibits better diode characteristic compared to the TPA-based device. Computational simulations show that the BLG/CAR system exhibits smaller energy-level-differences than the BLG/TPA, which supports the experimental findings of a lower Schottky barrier and series resistance in BLG/CAR diode.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We have investigated the effect of two different self-assembled monolayers (SAMs) on electrical characteristics of bilayer graphene (BLG)/n-Si Schottky diodes. Novel 4″bis(diphenylamino)-1, 1′:3″-terphenyl-5′ carboxylic acids (TPA) and 4,4-di-9H-carbazol-9-yl-1,1′:3′1′-terphenyl-5′ carboxylic acid (CAR) aromatic SAMs have been used to modify n-Si surfaces. Cyclic voltammetry (CV) and Kelvin probe force microscopy (KPFM) results have been evaluated to verify the modification of n-Si surface. The current–voltage (I–V) characteristics of bare and SAMs modified devices show rectification behaviour verifying a Schottky junction at the interface. The ideality factors (n) from ln(I)–V dependences were determined as 2.13, 1.96 and 2.07 for BLG/n-Si, BLG/TPA/n-Si and BLG/CAR/n-Si Schottky diodes, respectively. In addition, Schottky barrier height (SBH) and series resistance (Rs) of SAMs modified diodes were decreased compared to bare diode due to the formation of a compatible interface between graphene and Si as well as π–π interaction between aromatic SAMs and graphene. The CAR-based device exhibits better diode characteristic compared to the TPA-based device. Computational simulations show that the BLG/CAR system exhibits smaller energy-level-differences than the BLG/TPA, which supports the experimental findings of a lower Schottky barrier and series resistance in BLG/CAR diode. |
Özdamar, Burak; Bouzid, Assil; Ori, Guido; Massobrio, Carlo; Boero, Mauro: First-Principles Study of Dissociation Processes for the Synthesis of Fe and Co Oxide Nanoparticles. Journal of Chemical Theory and Computation, 14 (1), pp. 225-235, 2018, (PMID: 29206461). (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.jctc.7b00869, title = {First-Principles Study of Dissociation Processes for the Synthesis of Fe and Co Oxide Nanoparticles}, author = {Burak Özdamar and Assil Bouzid and Guido Ori and Carlo Massobrio and Mauro Boero}, url = {https://doi.org/10.1021/acs.jctc.7b00869}, doi = {10.1021/acs.jctc.7b00869}, year = {2018}, date = {2018-01-01}, journal = {Journal of Chemical Theory and Computation}, volume = {14}, number = {1}, pages = {225-235}, note = {PMID: 29206461}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Kalkan, S B; Aydın, H; Özkendir, D; Çelebi, C: The effect of adsorbates on the electrical stability of graphene studied by transient photocurrent spectroscopy. Applied Physics Letters, 112 (1), pp. 013103, 2018. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/1.5011454, title = {The effect of adsorbates on the electrical stability of graphene studied by transient photocurrent spectroscopy}, author = {S B Kalkan and H Aydın and D Özkendir and C Çelebi}, url = {https://doi.org/10.1063/1.5011454}, doi = {10.1063/1.5011454}, year = {2018}, date = {2018-01-01}, journal = {Applied Physics Letters}, volume = {112}, number = {1}, pages = {013103}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Cotin, Geoffrey; Kiefer, Céline; Perton, Francis; Boero, Mauro; Özdamar, Burak; Bouzid, Assil; Ori, Guido; Massobrio, Carlo; Begin, Dominique; Pichon, Benoit; Mertz, Damien; Begin-Colin, Sylvie: Evaluating the Critical Roles of Precursor Nature and Water Content When Tailoring Magnetic Nanoparticles for Specific Applications. ACS Applied Nano Materials, 1 (8), pp. 4306-4316, 2018. (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acsanm.8b01123, title = {Evaluating the Critical Roles of Precursor Nature and Water Content When Tailoring Magnetic Nanoparticles for Specific Applications}, author = {Geoffrey Cotin and Céline Kiefer and Francis Perton and Mauro Boero and Burak Özdamar and Assil Bouzid and Guido Ori and Carlo Massobrio and Dominique Begin and Benoit Pichon and Damien Mertz and Sylvie Begin-Colin}, url = {https://doi.org/10.1021/acsanm.8b01123}, doi = {10.1021/acsanm.8b01123}, year = {2018}, date = {2018-01-01}, journal = {ACS Applied Nano Materials}, volume = {1}, number = {8}, pages = {4306-4316}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2017 |
Iyikanat, F; Kandemir, A; Ozaydin, H D; Senger, R T; Sahin, H: Hydrogenation-driven phase transition in single-layer TiSe2. Nanotechnology, 28 (49), pp. 495709, 2017. (Type: Journal Article | Links | BibTeX) @article{iyikanat2017, title = {Hydrogenation-driven phase transition in single-layer TiSe2}, author = {F Iyikanat and A Kandemir and H D Ozaydin and R T Senger and H Sahin}, url = {https://doi.org/10.1088%2F1361-6528%2Faa94ab}, doi = {10.1088/1361-6528/aa94ab}, year = {2017}, date = {2017-11-01}, journal = {Nanotechnology}, volume = {28}, number = {49}, pages = {495709}, publisher = {IOP Publishing}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Mayda, Selma; Kandemir, Zafer; Bulut, Nejat: Electronic Structure of Cyanocobalamin: DFT+QMC Study. Journal of Superconductivity and Novel Magnetism, 30 (11), pp. 3301–3308, 2017, ISSN: 1557-1947. (Type: Journal Article | Abstract | Links | BibTeX) @article{mayda2017, title = {Electronic Structure of Cyanocobalamin: DFT+QMC Study}, author = {Selma Mayda and Zafer Kandemir and Nejat Bulut}, url = {https://doi.org/10.1007/s10948-016-3635-7}, doi = {10.1007/s10948-016-3635-7}, issn = {1557-1947}, year = {2017}, date = {2017-11-01}, journal = {Journal of Superconductivity and Novel Magnetism}, volume = {30}, number = {11}, pages = {3301--3308}, abstract = {We study the electronic structure and the magnetic correlations of cyanocobalamin (C63H88CoN14O14P) by using the framework of the multi-orbital single-impurity Haldane-Anderson model of a transition metal impurity in a semiconductor host. Here, we first determine the parameters of the Anderson Hamiltonian by performing density functional theory (DFT) calculations. Then, we use the quantum Monte Carlo (QMC) technique to obtain the electronic structure and the magnetic correlation functions for this effective model. We find that new electronic states, which correspond to impurity bound states, form above the lowest unoccupied level of the host semiconductor. These new states derive from the atomic orbitals at the cobalt site and the rest of the molecule. We observe that magnetic moments develop at the Co(3d$nu$) orbitals and over the surrounding sites. We also observe that antiferromagnetic correlations exist between the Co (3d$nu$) orbitals and the surrounding atoms. These antiferromagnetic correlations depend on the filling of the impurity bound states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the electronic structure and the magnetic correlations of cyanocobalamin (C63H88CoN14O14P) by using the framework of the multi-orbital single-impurity Haldane-Anderson model of a transition metal impurity in a semiconductor host. Here, we first determine the parameters of the Anderson Hamiltonian by performing density functional theory (DFT) calculations. Then, we use the quantum Monte Carlo (QMC) technique to obtain the electronic structure and the magnetic correlation functions for this effective model. We find that new electronic states, which correspond to impurity bound states, form above the lowest unoccupied level of the host semiconductor. These new states derive from the atomic orbitals at the cobalt site and the rest of the molecule. We observe that magnetic moments develop at the Co(3d$nu$) orbitals and over the surrounding sites. We also observe that antiferromagnetic correlations exist between the Co (3d$nu$) orbitals and the surrounding atoms. These antiferromagnetic correlations depend on the filling of the impurity bound states. |
Akbali, B; Yanilmaz, A; Tomak, A; Tongay, S; Ç, C; Sahin, H: Few-layer MoS2 as nitrogen protective barrier. Nanotechnology, 28 (41), pp. 415706, 2017. (Type: Journal Article | Abstract | Links | BibTeX) @article{akbali2017, title = {Few-layer MoS2 as nitrogen protective barrier}, author = {B Akbali and A Yanilmaz and A Tomak and S Tongay and C Ç and H Sahin}, url = {https://doi.org/10.1088%2F1361-6528%2Faa825e}, doi = {10.1088/1361-6528/aa825e}, year = {2017}, date = {2017-09-01}, journal = {Nanotechnology}, volume = {28}, number = {41}, pages = {415706}, publisher = {IOP Publishing}, abstract = {We report experimental and theoretical investigations of the observed barrier behavior of few-layer MoS2 against nitrogenation. Owing to its low-strength shearing, low friction coefficient, and high lubricity, MoS2 exhibits the demeanor of a natural N-resistant coating material. Raman spectroscopy is done to determine the coating capability of MoS2 on graphene. Surface morphology of our MoS2/graphene heterostructure is characterized by using optical microscopy, scanning electron microscopy, and atomic force microscopy. In addition, density functional theory-based calculations are performed to understand the energy barrier performance of MoS2 against nitrogenation. The penetration of nitrogen atoms through a defect-free MoS2 layer is prevented by a very high vertical diffusion barrier, indicating that MoS2 can serve as a protective layer for the nitrogenation of graphene. Our experimental and theoretical results show that MoS2 material can be used both as an efficient nanocoating material and as a nanoscale mask for selective nitrogenation of graphene layer.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report experimental and theoretical investigations of the observed barrier behavior of few-layer MoS2 against nitrogenation. Owing to its low-strength shearing, low friction coefficient, and high lubricity, MoS2 exhibits the demeanor of a natural N-resistant coating material. Raman spectroscopy is done to determine the coating capability of MoS2 on graphene. Surface morphology of our MoS2/graphene heterostructure is characterized by using optical microscopy, scanning electron microscopy, and atomic force microscopy. In addition, density functional theory-based calculations are performed to understand the energy barrier performance of MoS2 against nitrogenation. The penetration of nitrogen atoms through a defect-free MoS2 layer is prevented by a very high vertical diffusion barrier, indicating that MoS2 can serve as a protective layer for the nitrogenation of graphene. Our experimental and theoretical results show that MoS2 material can be used both as an efficient nanocoating material and as a nanoscale mask for selective nitrogenation of graphene layer. |
Eschmann, Neil A; Georgieva, Elka R; Ganguly, Pritam; Borbat, Peter P; Rappaport, Maxime D; Akdogan, Yasar; Freed, Jack H; Shea, Joan-Emma; Han, Songi: Signature of an aggregation-prone conformation of tau. Scientific Reports, 7 , pp. 44739 EP -, 2017, (Article). (Type: Journal Article | Links | BibTeX) @article{eschmann2017, title = {Signature of an aggregation-prone conformation of tau}, author = {Neil A Eschmann and Elka R Georgieva and Pritam Ganguly and Peter P Borbat and Maxime D Rappaport and Yasar Akdogan and Jack H Freed and Joan-Emma Shea and Songi Han}, url = {https://doi.org/10.1038/srep44739}, year = {2017}, date = {2017-03-17}, journal = {Scientific Reports}, volume = {7}, pages = {44739 EP -}, publisher = {The Author(s) SN -}, note = {Article}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sevinçli, Hâldun: Quartic Dispersion, Strong Singularity, Magnetic Instability, and Unique Thermoelectric Properties in Two-Dimensional Hexagonal Lattices of Group-VA Elements. Nano Letters, 17 (4), pp. 2589-2595, 2017, (PMID: 28318269). (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.nanolett.7b00366, title = {Quartic Dispersion, Strong Singularity, Magnetic Instability, and Unique Thermoelectric Properties in Two-Dimensional Hexagonal Lattices of Group-VA Elements}, author = {Hâldun Sevinçli}, url = {https://doi.org/10.1021/acs.nanolett.7b00366}, doi = {10.1021/acs.nanolett.7b00366}, year = {2017}, date = {2017-01-01}, journal = {Nano Letters}, volume = {17}, number = {4}, pages = {2589-2595}, note = {PMID: 28318269}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Gökçe, Melis; Şentürk, Ufuk; Uslu, Deniz K; Burgaz, Gözde; Şahin, Yüksel; Gökçe, Aytaç Gürhan: Investigation of europium concentration dependence on the luminescent properties of borogermanate glasses. Journal of Luminescence, 192 , pp. 263 - 268, 2017, ISSN: 0022-2313. (Type: Journal Article | Abstract | Links | BibTeX) @article{gokce2017263, title = {Investigation of europium concentration dependence on the luminescent properties of borogermanate glasses}, author = {Melis Gökçe and Ufuk Şentürk and Deniz K Uslu and Gözde Burgaz and Yüksel Şahin and Aytaç Gürhan Gökçe}, url = {http://www.sciencedirect.com/science/article/pii/S0022231317306257}, doi = {https://doi.org/10.1016/j.jlumin.2017.06.041}, issn = {0022-2313}, year = {2017}, date = {2017-01-01}, journal = {Journal of Luminescence}, volume = {192}, pages = {263 - 268}, abstract = {In order to elucidate the effect of europium content on the optical and luminescent properties of borogermanate glasses, a series of Eu3+ doped 30B2O3-40GeO2-(30-x)Gd2O3 glasses with various doping levels (x=1–9mol%) have been synthesized and studied with transmission, absorption, photoluminescence and decay time measurements. The transmission spectra proved that the title glasses maintained a high transparency about 80% in the 440 to 900nm region. Based on the absorption spectra, the optical band gaps obtained from Tauc's plot can be narrowed by increasing content of Eu3+. From the photoluminescence spectra, the strongest red emission has been observed from the 5D0→7F2 level of Eu3+ ions in borogermanate glasses. The strongest emission and excitation intensities of Eu3+ ions are at the doping level of x=7 mol% and then these intensities decrease due to concentration quenching. The red to orange ratio (R/O) of 5D0→7F2 to 5D0→7F1 transitions has been investigated to predict the local environment of Eu3+ ions. Judd-Ofelt (J-O) analyses have been performed from the emission spectra. The values of R/O and Ω2 present an increase with increasing doping level, indicating the lower symmetric environment for Eu3+ ions and higher covalency for Eu-O bond. The emission efficiency calculated from J-O theory is 75% at x=2mol%. The decay time curves of 6P7/2→8S7/2 transition of Gd3+ ions and 5D0–7F2 transition of Eu3+ ions confirm the energy transfer from Gd3+ to Eu3+ ions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In order to elucidate the effect of europium content on the optical and luminescent properties of borogermanate glasses, a series of Eu3+ doped 30B2O3-40GeO2-(30-x)Gd2O3 glasses with various doping levels (x=1–9mol%) have been synthesized and studied with transmission, absorption, photoluminescence and decay time measurements. The transmission spectra proved that the title glasses maintained a high transparency about 80% in the 440 to 900nm region. Based on the absorption spectra, the optical band gaps obtained from Tauc's plot can be narrowed by increasing content of Eu3+. From the photoluminescence spectra, the strongest red emission has been observed from the 5D0→7F2 level of Eu3+ ions in borogermanate glasses. The strongest emission and excitation intensities of Eu3+ ions are at the doping level of x=7 mol% and then these intensities decrease due to concentration quenching. The red to orange ratio (R/O) of 5D0→7F2 to 5D0→7F1 transitions has been investigated to predict the local environment of Eu3+ ions. Judd-Ofelt (J-O) analyses have been performed from the emission spectra. The values of R/O and Ω2 present an increase with increasing doping level, indicating the lower symmetric environment for Eu3+ ions and higher covalency for Eu-O bond. The emission efficiency calculated from J-O theory is 75% at x=2mol%. The decay time curves of 6P7/2→8S7/2 transition of Gd3+ ions and 5D0–7F2 transition of Eu3+ ions confirm the energy transfer from Gd3+ to Eu3+ ions. |
Güner, Tuğrul; Şentürk, Ufuk; Demir, Mustafa M: Optical enhancement of phosphor-converted wLEDs using glass beads. Optical Materials, 72 , pp. 769 - 774, 2017, ISSN: 0925-3467. (Type: Journal Article | Abstract | Links | BibTeX) @article{guner2017769, title = {Optical enhancement of phosphor-converted wLEDs using glass beads}, author = {Tuğrul Güner and Ufuk Şentürk and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S0925346717304810}, doi = {https://doi.org/10.1016/j.optmat.2017.07.033}, issn = {0925-3467}, year = {2017}, date = {2017-01-01}, journal = {Optical Materials}, volume = {72}, pages = {769 - 774}, abstract = {YAG:Ce3+ is a yellow-source compound commonly used in phosphor conversion layers for direct coating or remote phosphor configurations in LED illumination. This material, however, suffers from a high correlated color temperature, and low color-rendering index due to its deficiency in the red spectrum. In this study, glass beads (GB) with an average particle diameter of 10 μm were introduced to the conversion layer of a YAG:Ce3+ particulate-filled polydimethylsiloxane matrix composite structure and found to improve the optical features of the resulting composite.}, keywords = {}, pubstate = {published}, tppubtype = {article} } YAG:Ce3+ is a yellow-source compound commonly used in phosphor conversion layers for direct coating or remote phosphor configurations in LED illumination. This material, however, suffers from a high correlated color temperature, and low color-rendering index due to its deficiency in the red spectrum. In this study, glass beads (GB) with an average particle diameter of 10 μm were introduced to the conversion layer of a YAG:Ce3+ particulate-filled polydimethylsiloxane matrix composite structure and found to improve the optical features of the resulting composite. |
Ozer, Imran; Tomak, Aysel; Zareie, Hadi M; Baran, Yusuf; Bulmus, Volga: Effect of Molecular Architecture on Cell Interactions and Stealth Properties of PEG. Biomacromolecules, 18 (9), pp. 2699-2710, 2017, (PMID: 28777555). (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.biomac.7b00443, title = {Effect of Molecular Architecture on Cell Interactions and Stealth Properties of PEG}, author = {Imran Ozer and Aysel Tomak and Hadi M Zareie and Yusuf Baran and Volga Bulmus}, url = {https://doi.org/10.1021/acs.biomac.7b00443}, doi = {10.1021/acs.biomac.7b00443}, year = {2017}, date = {2017-01-01}, journal = {Biomacromolecules}, volume = {18}, number = {9}, pages = {2699-2710}, note = {PMID: 28777555}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Çelik, Aslı; Topçu, Gökhan; Baba, Alper; Akdogan, Yasar; Şentürk, Ufuk; Demir, Mustafa M: Experimental modeling of silicate-based geothermal deposits. Geothermics, 69 , pp. 65 - 73, 2017, ISSN: 0375-6505. (Type: Journal Article | Abstract | Links | BibTeX) @article{celik201765, title = {Experimental modeling of silicate-based geothermal deposits}, author = {Aslı Çelik and Gökhan Topçu and Alper Baba and Yasar Akdogan and Ufuk Şentürk and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S0375650517300512}, doi = {https://doi.org/10.1016/j.geothermics.2017.04.007}, issn = {0375-6505}, year = {2017}, date = {2017-01-01}, journal = {Geothermics}, volume = {69}, pages = {65 - 73}, abstract = {Scaling by metal silicates represents a major obstacle for geothermal systems. A composition that enables the fabrication of artificial deposits is necessary for the rapid testing of potential inhibitors. In this work, artificial deposits were synthesized by employing experimental conditions similar to those in the Tuzla Geothermal Field in Turkey. Although refluxing enabled the formation of a precipitate that was similar to naturally formed deposits in color and texture, their elemental composition and morphology showed a mismatch. An autoclave enabled the production of a precipitate that more closely resembled naturally formed deposits in color, texture, elemental composition, and structure.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Scaling by metal silicates represents a major obstacle for geothermal systems. A composition that enables the fabrication of artificial deposits is necessary for the rapid testing of potential inhibitors. In this work, artificial deposits were synthesized by employing experimental conditions similar to those in the Tuzla Geothermal Field in Turkey. Although refluxing enabled the formation of a precipitate that was similar to naturally formed deposits in color and texture, their elemental composition and morphology showed a mismatch. An autoclave enabled the production of a precipitate that more closely resembled naturally formed deposits in color, texture, elemental composition, and structure. |
Zeren, Doğuş; Güden, Mustafa: The increased compression strength of an epoxy resin with the addition of heat-treated natural nano-structured diatom frustules. Journal of Composite Materials, 51 (12), pp. 1681-1691, 2017. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1177/0021998316669855, title = {The increased compression strength of an epoxy resin with the addition of heat-treated natural nano-structured diatom frustules}, author = {Doğuş Zeren and Mustafa Güden}, url = {https://doi.org/10.1177/0021998316669855}, doi = {10.1177/0021998316669855}, year = {2017}, date = {2017-01-01}, journal = {Journal of Composite Materials}, volume = {51}, number = {12}, pages = {1681-1691}, abstract = {Natural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200℃ for 2 h and used as filler/reinforcing agent (15 wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900℃. The epoxy resin test samples reinforced with heat-treated and as-received frustules and neat epoxy test samples were compression tested at the quasi-static strain rate of 7 × 10−3 s−1. The results showed that the inclusion of the frustules heat-treated at 1000℃ increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000℃ and the as-received frustules increased the strength by ∼25% and 16%, respectively. The heat treatment above 1000℃ decreased the surface area of the frustules from 8.23 m2 g−1 to 3.46 m2 g−1. The cristobalite grains of the frustules heat-treated at 1000℃ was smaller than 100 nm, while the grain size increased to ∼500 nm at 1200℃. The increased compressive stresses of the resin at the specific heat treatment temperature (1000℃) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000℃ were attributed to the micro-cracking of the frustules that might be resulted from higher density of the cristobalite than that of the opal and accompanying reduction of the surface area and the surface pore sizes that might impair the resin-frustule interlocking and intrusion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Natural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200℃ for 2 h and used as filler/reinforcing agent (15 wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900℃. The epoxy resin test samples reinforced with heat-treated and as-received frustules and neat epoxy test samples were compression tested at the quasi-static strain rate of 7 × 10−3 s−1. The results showed that the inclusion of the frustules heat-treated at 1000℃ increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000℃ and the as-received frustules increased the strength by ∼25% and 16%, respectively. The heat treatment above 1000℃ decreased the surface area of the frustules from 8.23 m2 g−1 to 3.46 m2 g−1. The cristobalite grains of the frustules heat-treated at 1000℃ was smaller than 100 nm, while the grain size increased to ∼500 nm at 1200℃. The increased compressive stresses of the resin at the specific heat treatment temperature (1000℃) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000℃ were attributed to the micro-cracking of the frustules that might be resulted from higher density of the cristobalite than that of the opal and accompanying reduction of the surface area and the surface pore sizes that might impair the resin-frustule interlocking and intrusion. |
Isık, Tuğba; Demir, Mustafa M; Aydogan, Cansu; Ciftci, Mustafa; Yagci, Yusuf: Hydrophobic coatings from photochemically prepared hydrophilic polymethacrylates via electrospraying. Journal of Polymer Science Part A: Polymer Chemistry, 55 (8), pp. 1338-1344, 2017. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/pola.28501, title = {Hydrophobic coatings from photochemically prepared hydrophilic polymethacrylates via electrospraying}, author = {Tuğba Isık and Mustafa M Demir and Cansu Aydogan and Mustafa Ciftci and Yusuf Yagci}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/pola.28501}, doi = {10.1002/pola.28501}, year = {2017}, date = {2017-01-01}, journal = {Journal of Polymer Science Part A: Polymer Chemistry}, volume = {55}, number = {8}, pages = {1338-1344}, abstract = {ABSTRACT Linear poly(hydroxyethyl methacrylate-co-methyl methacrylate) P(HEMA-co-MMA) and poly(dimehylaminoethyl methacrylate-co-methyl methacrylate) P(DMAEMA-co-MMA) and their corresponding hyperbranched copolymers were synthesized by conventional photoinitiated free radical polymerization and self-condensing vinyl polymerization (SCVP) using Type I and Type II photoinitiators, respectively. Then, the polymers were processed by electrospraying in N, N-dimethylformamide. The surface of the resulting electrospray coatings was examined by SEM, XPS, and WCA then compared with those prepared by drop casting. Regardless of the structural nature of the polymers, electrospraying allows the preparation of rough surface that shows more hydrophobic behavior. Electrospray coatings with linear and hyperbranched copolymers exhibited WCA as ∼150° and ∼130°, respectively, indicating that branching reduces the WCA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1338–1344}, keywords = {}, pubstate = {published}, tppubtype = {article} } ABSTRACT Linear poly(hydroxyethyl methacrylate-co-methyl methacrylate) P(HEMA-co-MMA) and poly(dimehylaminoethyl methacrylate-co-methyl methacrylate) P(DMAEMA-co-MMA) and their corresponding hyperbranched copolymers were synthesized by conventional photoinitiated free radical polymerization and self-condensing vinyl polymerization (SCVP) using Type I and Type II photoinitiators, respectively. Then, the polymers were processed by electrospraying in N, N-dimethylformamide. The surface of the resulting electrospray coatings was examined by SEM, XPS, and WCA then compared with those prepared by drop casting. Regardless of the structural nature of the polymers, electrospraying allows the preparation of rough surface that shows more hydrophobic behavior. Electrospray coatings with linear and hyperbranched copolymers exhibited WCA as ∼150° and ∼130°, respectively, indicating that branching reduces the WCA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1338–1344 |
Shukla, Sudheesh K; Demir, Mustafa M; Govender, Penny P; Tiwari, Ashutosh; Shukla, S K: Optical fibre based non-enzymatic glucose sensing over Cu2+-doped polyaniline hybrid matrix. Sensors and Actuators B: Chemical, 242 , pp. 522 - 528, 2017, ISSN: 0925-4005. (Type: Journal Article | Abstract | Links | BibTeX) @article{shukla2017522, title = {Optical fibre based non-enzymatic glucose sensing over Cu2+-doped polyaniline hybrid matrix}, author = {Sudheesh K Shukla and Mustafa M Demir and Penny P Govender and Ashutosh Tiwari and S K Shukla}, url = {http://www.sciencedirect.com/science/article/pii/S0925400516318615}, doi = {https://doi.org/10.1016/j.snb.2016.11.062}, issn = {0925-4005}, year = {2017}, date = {2017-01-01}, journal = {Sensors and Actuators B: Chemical}, volume = {242}, pages = {522 - 528}, abstract = {The opto-chemical glucose sensing over cupric ion doped polyaniline (Cu+2/PANI) hybrid polymer matrix coated glass rod based optode has been demonstrated.Cu+2/PANI hybrid matrix was synthesized by in situ chemical polymerization of intrinsically functionalized aniline. Furthermore, developed optode has been explored for direct oxidisation of glucose on Cu+2/PANI hybrid matrix for non-enzymatic glucose sensing employing O-dianisidine indicator system. The proposed glucose sensor works well in range of 50mg/dL–200mg/dL with response time of 15s in artificial as well as in biological samples along with 40days of lifespan.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The opto-chemical glucose sensing over cupric ion doped polyaniline (Cu+2/PANI) hybrid polymer matrix coated glass rod based optode has been demonstrated.Cu+2/PANI hybrid matrix was synthesized by in situ chemical polymerization of intrinsically functionalized aniline. Furthermore, developed optode has been explored for direct oxidisation of glucose on Cu+2/PANI hybrid matrix for non-enzymatic glucose sensing employing O-dianisidine indicator system. The proposed glucose sensor works well in range of 50mg/dL–200mg/dL with response time of 15s in artificial as well as in biological samples along with 40days of lifespan. |
Kandemir, Ali; Ozden, Ayberk; Cagin, Tahir; Sevik, Cem: Thermal conductivity engineering of bulk and one-dimensional Si-Ge nanoarchitectures. Science and Technology of Advanced Materials, 18 (1), pp. 187-196, 2017, (PMID: 28469733). (Type: Journal Article | Links | BibTeX) @article{doi:10.1080/14686996.2017.1288065, title = {Thermal conductivity engineering of bulk and one-dimensional Si-Ge nanoarchitectures}, author = {Ali Kandemir and Ayberk Ozden and Tahir Cagin and Cem Sevik}, url = {https://doi.org/10.1080/14686996.2017.1288065}, doi = {10.1080/14686996.2017.1288065}, year = {2017}, date = {2017-01-01}, journal = {Science and Technology of Advanced Materials}, volume = {18}, number = {1}, pages = {187-196}, publisher = {Taylor & Francis}, note = {PMID: 28469733}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Yanilmaz, A; Tomak, A; Akbali, B; Bacaksiz, C; Ozceri, E; Ari, O; Senger, R T; Selamet, Y; Zareie, H M: Nitrogen doping for facile and effective modification of graphene surfaces. RSC Adv., 7 , pp. 28383-28392, 2017. (Type: Journal Article | Abstract | Links | BibTeX) @article{C7RA03046K, title = {Nitrogen doping for facile and effective modification of graphene surfaces}, author = {A Yanilmaz and A Tomak and B Akbali and C Bacaksiz and E Ozceri and O Ari and R T Senger and Y Selamet and H M Zareie}, url = {http://dx.doi.org/10.1039/C7RA03046K}, doi = {10.1039/C7RA03046K}, year = {2017}, date = {2017-01-01}, journal = {RSC Adv.}, volume = {7}, pages = {28383-28392}, publisher = {The Royal Society of Chemistry}, abstract = {We report experimental and theoretical investigations of nitrogen doped graphene. A low-pressure Chemical Vapor Deposition (CVD) system was used to grow large-area graphene on copper foil, using ethylene as the carbon source. Nitrogen-doped graphene (N-graphene) was prepared by exposing the graphene transferred to different substrates to atomic nitrogen plasma. The effect of varying nitrogen flow rates on doping of graphene was investigated while keeping the power and time constant during the process. The N-graphene was characterized via Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Tunneling Microscopy and Spectroscopy (STM and STS), and Fourier Transform Infrared spectroscopy (FTIR). Raman mapping of N-graphene was also performed to show homogeneity of nitrogen on the graphitic lattice. XPS results have revealed the presence of different nitrogen configurations in the graphitic lattice with similar doping concentrations. Density functional theory (DFT) based calculations showed that the periodic adsorption of N atoms predominantly occurs on top of the C atoms rather than through substitution of C in our N-graphene samples. Our results indicate a feasible procedure for producing N-graphene with homogenous and effective doping which would be valuable in electronic and optical applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report experimental and theoretical investigations of nitrogen doped graphene. A low-pressure Chemical Vapor Deposition (CVD) system was used to grow large-area graphene on copper foil, using ethylene as the carbon source. Nitrogen-doped graphene (N-graphene) was prepared by exposing the graphene transferred to different substrates to atomic nitrogen plasma. The effect of varying nitrogen flow rates on doping of graphene was investigated while keeping the power and time constant during the process. The N-graphene was characterized via Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Tunneling Microscopy and Spectroscopy (STM and STS), and Fourier Transform Infrared spectroscopy (FTIR). Raman mapping of N-graphene was also performed to show homogeneity of nitrogen on the graphitic lattice. XPS results have revealed the presence of different nitrogen configurations in the graphitic lattice with similar doping concentrations. Density functional theory (DFT) based calculations showed that the periodic adsorption of N atoms predominantly occurs on top of the C atoms rather than through substitution of C in our N-graphene samples. Our results indicate a feasible procedure for producing N-graphene with homogenous and effective doping which would be valuable in electronic and optical applications. |
Semerci, T; Demirhan, Y; Miyakawa, N; Wang, H B; Ozyuzer, L: Fabrication of Bi2212 Single Crystal Bolometer for Detection of Terahertz Waves. Pereira, Mauro F; Shulika, Oleksiy (Ed.): THz for CBRN and Explosives Detection and Diagnosis, pp. 75–83, Springer Netherlands, Dordrecht, 2017, ISBN: 978-94-024-1093-8. (Type: Inproceedings | Abstract | Links | BibTeX) @inproceedings{semerci2017, title = {Fabrication of Bi2212 Single Crystal Bolometer for Detection of Terahertz Waves}, author = {T Semerci and Y Demirhan and N Miyakawa and H B Wang and L Ozyuzer}, editor = {Mauro F Pereira and Oleksiy Shulika}, url = {https://link.springer.com/chapter/10.1007/978-94-024-1093-8_11}, isbn = {978-94-024-1093-8}, year = {2017}, date = {2017-01-01}, booktitle = {THz for CBRN and Explosives Detection and Diagnosis}, pages = {75--83}, publisher = {Springer Netherlands}, address = {Dordrecht}, abstract = {Terahertz (THz) radiation is in powerful region of electromagnetic spectrum because of prosperous application areas yet deficiency still exists about sources and detectors in despite of improvements of the research field in this range. This gap can be filled by focusing on development of THz detectors. Therefore, bolometers were preferred through many detectors due to detection sensitivity above 1 THz. In this study, Bi2Sr2CaCu2O8+$delta$ (Bi2212) single crystals were used to fabricate THz bolometric detector. Bi2212 single crystals were transferred on sapphire substrate by cleavage process and e-beam lithography and ion beam etching were used to fabricate the microchip clean room facilities. Custom-designed cryogenic cryostat was used for a-b axis electrical and THz response measurements with liquid nitrogen cooled system. After electrical measurements, Bi2212 microchips detected the signals using Stefan-Boltzmann Lamp and response time were calculated. This study have shown with our experimental results that Bi2212 single crystals are potential candidates for THz bolometric detectors.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Terahertz (THz) radiation is in powerful region of electromagnetic spectrum because of prosperous application areas yet deficiency still exists about sources and detectors in despite of improvements of the research field in this range. This gap can be filled by focusing on development of THz detectors. Therefore, bolometers were preferred through many detectors due to detection sensitivity above 1 THz. In this study, Bi2Sr2CaCu2O8+$delta$ (Bi2212) single crystals were used to fabricate THz bolometric detector. Bi2212 single crystals were transferred on sapphire substrate by cleavage process and e-beam lithography and ion beam etching were used to fabricate the microchip clean room facilities. Custom-designed cryogenic cryostat was used for a-b axis electrical and THz response measurements with liquid nitrogen cooled system. After electrical measurements, Bi2212 microchips detected the signals using Stefan-Boltzmann Lamp and response time were calculated. This study have shown with our experimental results that Bi2212 single crystals are potential candidates for THz bolometric detectors. |
İncel, Anıl; Akın, Osman; Çağır, Ali; Yıldız, Ümit Hakan; Demir, Mustafa M: Smart phone assisted detection and quantification of cyanide in drinking water by paper based sensing platform. Sensors and Actuators B: Chemical, 252 , pp. 886 - 893, 2017, ISSN: 0925-4005. (Type: Journal Article | Abstract | Links | BibTeX) @article{incel2017886b, title = {Smart phone assisted detection and quantification of cyanide in drinking water by paper based sensing platform}, author = {Anıl İncel and Osman Akın and Ali Çağır and Ümit Hakan Yıldız and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S0925400517310559}, doi = {https://doi.org/10.1016/j.snb.2017.05.185}, issn = {0925-4005}, year = {2017}, date = {2017-01-01}, journal = {Sensors and Actuators B: Chemical}, volume = {252}, pages = {886 - 893}, abstract = {An organometallic dye, europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) and gold nanoparticles (Au NPs) impregnated paper based sensor platform have been utilized for development of fluorescence turn-on cyanide assay in aqueous media. The ordinary filter paper with 6μ m pore size were employed as solid support that facilitates impregnation of EuD4TEA and gold nanoparticles and provides durability. Detection mechanism relying on two processes (i) dissolution of gold nanoparticles causing fluorescence recovery and (ii) ligand exchange of triethyl amine with CN group stimulating cyanide specific fluorescence enhancement. The paper platform exhibit naked eye distinguishable color transition upon CN− addition from 10−2 to 10−12M. To standardize the methodology a homemade image processing algorithm has been developed that enabling calibration of color change and quantify CN− concentration. The described algorithm is applicable to Android smart phones and facilitate transforming these devices into a quantitative cyanide detector. The overall methodology provides instrument free cyanide detection and therefore rapid control of water quality and safety at off-field conditions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An organometallic dye, europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) and gold nanoparticles (Au NPs) impregnated paper based sensor platform have been utilized for development of fluorescence turn-on cyanide assay in aqueous media. The ordinary filter paper with 6μ m pore size were employed as solid support that facilitates impregnation of EuD4TEA and gold nanoparticles and provides durability. Detection mechanism relying on two processes (i) dissolution of gold nanoparticles causing fluorescence recovery and (ii) ligand exchange of triethyl amine with CN group stimulating cyanide specific fluorescence enhancement. The paper platform exhibit naked eye distinguishable color transition upon CN− addition from 10−2 to 10−12M. To standardize the methodology a homemade image processing algorithm has been developed that enabling calibration of color change and quantify CN− concentration. The described algorithm is applicable to Android smart phones and facilitate transforming these devices into a quantitative cyanide detector. The overall methodology provides instrument free cyanide detection and therefore rapid control of water quality and safety at off-field conditions. |
İncel, Anıl; Emirdag-Eanes, Mehtap; McMillen, Colin D; Demir, Mustafa M: Integration of Triboluminescent EuD4TEA Crystals to Transparent Polymers: Impact Sensor Application. ACS Applied Materials & Interfaces, 9 (7), pp. 6488-6496, 2017, (PMID: 28125205). (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acsami.6b16330b, title = {Integration of Triboluminescent EuD4TEA Crystals to Transparent Polymers: Impact Sensor Application}, author = {Anıl İncel and Mehtap Emirdag-Eanes and Colin D McMillen and Mustafa M Demir}, url = {https://doi.org/10.1021/acsami.6b16330}, doi = {10.1021/acsami.6b16330}, year = {2017}, date = {2017-01-01}, journal = {ACS Applied Materials & Interfaces}, volume = {9}, number = {7}, pages = {6488-6496}, note = {PMID: 28125205}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Olcer, Y A; Demirkurt, M; Demir, M M; Eroglu, A E: Development of molecularly imprinted polymers (MIPs) as a solid phase extraction (SPE) sorbent for the determination of ibuprofen in water. RSC Adv., 7 , pp. 31441-31447, 2017. (Type: Journal Article | Abstract | Links | BibTeX) @article{C7RA05254Eb, title = {Development of molecularly imprinted polymers (MIPs) as a solid phase extraction (SPE) sorbent for the determination of ibuprofen in water}, author = {Y A Olcer and M Demirkurt and M M Demir and A E Eroglu}, url = {http://dx.doi.org/10.1039/C7RA05254E}, doi = {10.1039/C7RA05254E}, year = {2017}, date = {2017-01-01}, journal = {RSC Adv.}, volume = {7}, pages = {31441-31447}, publisher = {The Royal Society of Chemistry}, abstract = {Ibuprofen is a well-known endocrine disrupter. In this study, highly selective molecularly imprinted polymers (MIPs) with different morphologies were synthesized via precipitation and bulk polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) in the presence of ibuprofen as a template. Non-imprinted polymers (NIPs) were also synthesized via the same procedure in the absence of ibuprofen. Spherical and monolithic MIPs were obtained using different experimental conditions, and the spherical MIP was shown to have better sorption towards ibuprofen. The optimum sample pH, sorbent amount, sample volume, and sorption time were determined to be 8.0, 25.0 mg, 10.0 mL, and 30.0 min, respectively. A methanol water mixture (MeOH : H2O, 80 : 20, pH 3.0) was employed as an eluent with >97% (±0.8}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ibuprofen is a well-known endocrine disrupter. In this study, highly selective molecularly imprinted polymers (MIPs) with different morphologies were synthesized via precipitation and bulk polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) in the presence of ibuprofen as a template. Non-imprinted polymers (NIPs) were also synthesized via the same procedure in the absence of ibuprofen. Spherical and monolithic MIPs were obtained using different experimental conditions, and the spherical MIP was shown to have better sorption towards ibuprofen. The optimum sample pH, sorbent amount, sample volume, and sorption time were determined to be 8.0, 25.0 mg, 10.0 mL, and 30.0 min, respectively. A methanol water mixture (MeOH : H2O, 80 : 20, pH 3.0) was employed as an eluent with >97% (±0.8 |
İncel, Anıl; Reddy, Subrayal M; Demir, Mustafa M: A new method to extend the stress response of triboluminescent crystals by using hydrogels. Materials Letters, 186 , pp. 210 - 213, 2017, ISSN: 0167-577X. (Type: Journal Article | Abstract | Links | BibTeX) @article{incel2017210, title = {A new method to extend the stress response of triboluminescent crystals by using hydrogels}, author = {Anıl İncel and Subrayal M Reddy and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S0167577X16315944}, doi = {https://doi.org/10.1016/j.matlet.2016.10.007}, issn = {0167-577X}, year = {2017}, date = {2017-01-01}, journal = {Materials Letters}, volume = {186}, pages = {210 - 213}, abstract = {Polyacrylamide hydrogel entrapment of EuD4TEA or Cu(NCS)(py)2(PPh3) radically extends the emission time of the triboluminescent (TL) crystalline particles by a factor of 103, optimized when matching the hydrophilic/hydrophobic characteristics of the TL/gel components. Triboluminescence intensity improves with hydration of the TL/hydrogel composite. The composites may be used in impact-related sensor applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Polyacrylamide hydrogel entrapment of EuD4TEA or Cu(NCS)(py)2(PPh3) radically extends the emission time of the triboluminescent (TL) crystalline particles by a factor of 103, optimized when matching the hydrophilic/hydrophobic characteristics of the TL/gel components. Triboluminescence intensity improves with hydration of the TL/hydrogel composite. The composites may be used in impact-related sensor applications. |
İncel, Anıl; Varlikli, Canan; McMillen, Colin D; Demir, Mustafa M: Triboluminescent Electrospun Mats with Blue-Green Emission under Mechanical Force. The Journal of Physical Chemistry C, 121 (21), pp. 11709-11716, 2017. (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.jpcc.7b02875c, title = {Triboluminescent Electrospun Mats with Blue-Green Emission under Mechanical Force}, author = {Anıl İncel and Canan Varlikli and Colin D McMillen and Mustafa M Demir}, url = {https://doi.org/10.1021/acs.jpcc.7b02875}, doi = {10.1021/acs.jpcc.7b02875}, year = {2017}, date = {2017-01-01}, journal = {The Journal of Physical Chemistry C}, volume = {121}, number = {21}, pages = {11709-11716}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Topçu, Gökhan; Çelik, Aslı; Baba, Alper; Demir, Mustafa M: Design of Polymeric Antiscalants Based on Functional Vinyl Monomers for (Fe, Mg) Silicates. Energy & Fuels, 31 (8), pp. 8489-8496, 2017. (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acs.energyfuels.7b01221, title = {Design of Polymeric Antiscalants Based on Functional Vinyl Monomers for (Fe, Mg) Silicates}, author = {Gökhan Topçu and Aslı Çelik and Alper Baba and Mustafa M Demir}, url = {https://doi.org/10.1021/acs.energyfuels.7b01221}, doi = {10.1021/acs.energyfuels.7b01221}, year = {2017}, date = {2017-01-01}, journal = {Energy & Fuels}, volume = {31}, number = {8}, pages = {8489-8496}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Celik, Asli; Koc, Gonca; Erdogan, Emre; Shahwan, Talal; Baba, Alper; Demir, Mustafa M: Use of electrospun fiber mats for the remediation of hypersaline geothermal brine. DESALINATION AND WATER TREATMENT, 62 , pp. 94-100, 2017. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000403566800010, title = {Use of electrospun fiber mats for the remediation of hypersaline geothermal brine}, author = {Asli Celik and Gonca Koc and Emre Erdogan and Talal Shahwan and Alper Baba and Mustafa M Demir}, url = {http://openaccess.iyte.edu.tr/handle/11147/6328}, doi = {http://doi.org/10.5004/dwt.2017.20151}, year = {2017}, date = {2017-01-01}, journal = {DESALINATION AND WATER TREATMENT}, volume = {62}, pages = {94-100}, abstract = {Geothermal brines display high contents of various metal ions that can adversely affect surface and groundwater resources. Nevertheless, it is possible to sequestrate these metals and use some of them in certain engineering applications. The aim of this study was to fabricate electrospun chitosan fiber mats and remove heavy metal cations from geothermal brine of the Tuzla geothermal field (TGF) by employing these mats. TGF is located on the Biga Peninsula in the northwestern part of Turkey. The brine of TGF has high salinity (EC > 91 mS/cm) and high temperature ( reservoir temperature is 173 degrees C). The brine is rich in terms of metal cations. For instance, the concentration of lithium ion in geothermal fluid ranges from 17 to 35 mg/L, with little seasonal variations. A horizontal electrospinning setup was employed to obtain a non-woven mat comprising submicron diameter chitosan fibers at 2.0 kV.cm(-1). This material was then utilized as a stable membrane for the removal of metal ions present in the brine through sorption at 25 degrees C overnight. The results showed that the chitosan fiber mats sequestrate various ions in the brine. Under the studied conditions, the material was capable of removing 46%, 44%, 50%, 44%, 40%, 67% and 48% of Li+, Mg2+, Ba2+, Sr2+, Mn2+, Ca2+ and K+ from the geothermal brine, respectively.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Geothermal brines display high contents of various metal ions that can adversely affect surface and groundwater resources. Nevertheless, it is possible to sequestrate these metals and use some of them in certain engineering applications. The aim of this study was to fabricate electrospun chitosan fiber mats and remove heavy metal cations from geothermal brine of the Tuzla geothermal field (TGF) by employing these mats. TGF is located on the Biga Peninsula in the northwestern part of Turkey. The brine of TGF has high salinity (EC > 91 mS/cm) and high temperature ( reservoir temperature is 173 degrees C). The brine is rich in terms of metal cations. For instance, the concentration of lithium ion in geothermal fluid ranges from 17 to 35 mg/L, with little seasonal variations. A horizontal electrospinning setup was employed to obtain a non-woven mat comprising submicron diameter chitosan fibers at 2.0 kV.cm(-1). This material was then utilized as a stable membrane for the removal of metal ions present in the brine through sorption at 25 degrees C overnight. The results showed that the chitosan fiber mats sequestrate various ions in the brine. Under the studied conditions, the material was capable of removing 46%, 44%, 50%, 44%, 40%, 67% and 48% of Li+, Mg2+, Ba2+, Sr2+, Mn2+, Ca2+ and K+ from the geothermal brine, respectively. |
2016 |
Kiymaz, D; Yagmurcukardes, M; Tomak, A; Sahin, H; Senger, R T; Peeters, F M; Zareie, H M; Zafer, C: Controlled growth mechanism of poly (3-hexylthiophene) nanowires. Nanotechnology, 27 (45), pp. 455604, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{kiymaz2016, title = {Controlled growth mechanism of poly (3-hexylthiophene) nanowires}, author = {D Kiymaz and M Yagmurcukardes and A Tomak and H Sahin and R T Senger and F M Peeters and H M Zareie and C Zafer}, url = {https://doi.org/10.1088%2F0957-4484%2F27%2F45%2F455604}, doi = {10.1088/0957-4484/27/45/455604}, year = {2016}, date = {2016-10-01}, journal = {Nanotechnology}, volume = {27}, number = {45}, pages = {455604}, publisher = {IOP Publishing}, abstract = {Synthesis of 1D-polymer nanowires by a self-assembly method using marginal solvents is an attractive technique. While the formation mechanism is poorly understood, this method is essential in order to control the growth of nanowires. Here we visualized the time-dependent assembly of poly (3-hexyl-thiophene-2,5-diyl) (P3HT) nanowires by atomic force microscopy and scanning tunneling microscopy. The assembly of P3HT nanowires was carried out at room temperature by mixing cyclohexanone (CHN), as a poor solvent, with polymer solution in 1,2-dichlorobenzene (DCB). Both π–π stacking and planarization, obtained at the mix volume ratio of P3HT (in DCB):CHN (10:7), were considered during the investigation. We find that the length of nanowires was determined by the ordering of polymers in the polymer repetition direction. Additionally, our density functional theory calculations revealed that the presence of DCB and CHN molecules that stabilize the structural distortions due to tail group of polymers was essential for the core-wire formation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Synthesis of 1D-polymer nanowires by a self-assembly method using marginal solvents is an attractive technique. While the formation mechanism is poorly understood, this method is essential in order to control the growth of nanowires. Here we visualized the time-dependent assembly of poly (3-hexyl-thiophene-2,5-diyl) (P3HT) nanowires by atomic force microscopy and scanning tunneling microscopy. The assembly of P3HT nanowires was carried out at room temperature by mixing cyclohexanone (CHN), as a poor solvent, with polymer solution in 1,2-dichlorobenzene (DCB). Both π–π stacking and planarization, obtained at the mix volume ratio of P3HT (in DCB):CHN (10:7), were considered during the investigation. We find that the length of nanowires was determined by the ordering of polymers in the polymer repetition direction. Additionally, our density functional theory calculations revealed that the presence of DCB and CHN molecules that stabilize the structural distortions due to tail group of polymers was essential for the core-wire formation. |
Akdogan, Y; Emrullahoglu, M; Tatlidil, D; Ucuncu, M; Cakan-Akdogan, G: EPR studies of intermolecular interactions and competitive binding of drugs in a drug-BSA binding model. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18 (32), pp. 22531-22539, 2016. (Type: Journal Article | Links | BibTeX) @article{ISI:000381436500058, title = {EPR studies of intermolecular interactions and competitive binding of drugs in a drug-BSA binding model}, author = {Y Akdogan and M Emrullahoglu and D Tatlidil and M Ucuncu and G Cakan-Akdogan}, url = {https://pubs.rsc.org/en/content/articlelanding/2016/cp/c6cp04137j#!divAbstract}, year = {2016}, date = {2016-08-01}, journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, volume = {18}, number = {32}, pages = {22531-22539}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sevik, Cem; Sevinçli, Hâldun: Promising thermoelectric properties of phosphorenes. Nanotechnology, 27 (35), pp. 355705, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{sevik_2016, title = {Promising thermoelectric properties of phosphorenes}, author = {Cem Sevik and Hâldun Sevinçli}, url = {https://doi.org/10.1088%2F0957-4484%2F27%2F35%2F355705}, doi = {10.1088/0957-4484/27/35/355705}, year = {2016}, date = {2016-07-01}, journal = {Nanotechnology}, volume = {27}, number = {35}, pages = {355705}, publisher = {IOP Publishing}, abstract = {Electronic, phononic, and thermoelectric transport properties of single layer black- and blue-phosphorene structures are investigated with first-principles based ballistic electron and phonon transport calculations employing hybrid functionals. The maximum values of room temperature thermoelectric figure of merit, ZT corresponding to armchair and zigzag directions of black-phosphorene, ∼0.5 and ∼0.25, are calculated as rather smaller than those obtained with first-principles based semiclassical Boltzmann transport theory calculations. On the other hand, the maximum value of room temperature ZT of blue-phosphorene is predicted to be substantially high and remarkable values as high as 2.5 are obtained for elevated temperatures. Besides the fact that these figures are obtained at the ballistic limit, our findings mark the strong possibility of high thermoelectric performance of blue-phosphorene in new generation thermoelectric applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electronic, phononic, and thermoelectric transport properties of single layer black- and blue-phosphorene structures are investigated with first-principles based ballistic electron and phonon transport calculations employing hybrid functionals. The maximum values of room temperature thermoelectric figure of merit, ZT corresponding to armchair and zigzag directions of black-phosphorene, ∼0.5 and ∼0.25, are calculated as rather smaller than those obtained with first-principles based semiclassical Boltzmann transport theory calculations. On the other hand, the maximum value of room temperature ZT of blue-phosphorene is predicted to be substantially high and remarkable values as high as 2.5 are obtained for elevated temperatures. Besides the fact that these figures are obtained at the ballistic limit, our findings mark the strong possibility of high thermoelectric performance of blue-phosphorene in new generation thermoelectric applications. |
Tomak, A; Bacaksiz, C; Mendirek, G; Sahin, H; Hur, D; Görgün, K; Senger, R T; Birer, Ö; Peeters, F M; Zareie, H M: Structural changes in a Schiff base molecular assembly initiated by scanning tunneling microscopy tip. Nanotechnology, 27 (33), pp. 335601, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{tomak2016, title = {Structural changes in a Schiff base molecular assembly initiated by scanning tunneling microscopy tip}, author = {A Tomak and C Bacaksiz and G Mendirek and H Sahin and D Hur and K Görgün and R T Senger and Ö Birer and F M Peeters and H M Zareie}, url = {https://doi.org/10.1088%2F0957-4484%2F27%2F33%2F335601}, doi = {10.1088/0957-4484/27/33/335601}, year = {2016}, date = {2016-07-01}, journal = {Nanotechnology}, volume = {27}, number = {33}, pages = {335601}, publisher = {IOP Publishing}, abstract = {We report the controlled self-organization and switching of newly designed Schiff base (E)-4-((4-(phenylethynyl) benzylidene) amino) benzenethiol (EPBB) molecules on a Au (111) surface at room temperature. Scanning tunneling microscopy and spectroscopy (STM/STS) were used to image and analyze the conformational changes of the EPBB molecules. The conformational change of the molecules was induced by using the STM tip while increasing the tunneling current. The switching of a domain or island of molecules was shown to be induced by the STM tip during scanning. Unambiguous fingerprints of the switching mechanism were observed via STM/STS measurements. Surface-enhanced Raman scattering was employed, to control and identify quantitatively the switching mechanism of molecules in a monolayer. Density functional theory calculations were also performed in order to understand the microscopic details of the switching mechanism. These calculations revealed that the molecular switching behavior stemmed from the strong interaction of the EPBB molecules with the STM tip. Our approach to controlling intermolecular mechanics provides a path towards the bottom-up assembly of more sophisticated molecular machines.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report the controlled self-organization and switching of newly designed Schiff base (E)-4-((4-(phenylethynyl) benzylidene) amino) benzenethiol (EPBB) molecules on a Au (111) surface at room temperature. Scanning tunneling microscopy and spectroscopy (STM/STS) were used to image and analyze the conformational changes of the EPBB molecules. The conformational change of the molecules was induced by using the STM tip while increasing the tunneling current. The switching of a domain or island of molecules was shown to be induced by the STM tip during scanning. Unambiguous fingerprints of the switching mechanism were observed via STM/STS measurements. Surface-enhanced Raman scattering was employed, to control and identify quantitatively the switching mechanism of molecules in a monolayer. Density functional theory calculations were also performed in order to understand the microscopic details of the switching mechanism. These calculations revealed that the molecular switching behavior stemmed from the strong interaction of the EPBB molecules with the STM tip. Our approach to controlling intermolecular mechanics provides a path towards the bottom-up assembly of more sophisticated molecular machines. |
Semerci, T; Demirhan, Y; Miyakawa, N; Wang, H B; Ozyuzer, L: Thin film like terahertz bolometric detector on Bi2212 single crystal. Optical and Quantum Electronics, 48 (6), pp. 340, 2016, ISSN: 1572-817X. (Type: Journal Article | Abstract | Links | BibTeX) @article{semerci2016, title = {Thin film like terahertz bolometric detector on Bi2212 single crystal}, author = {T Semerci and Y Demirhan and N Miyakawa and H B Wang and L Ozyuzer}, url = {https://doi.org/10.1007/s11082-016-0612-0}, doi = {10.1007/s11082-016-0612-0}, issn = {1572-817X}, year = {2016}, date = {2016-06-02}, journal = {Optical and Quantum Electronics}, volume = {48}, number = {6}, pages = {340}, abstract = {In this study, we developed a microbolometer chip fabricated from high temperature superconducting Bi2Sr2CaCu2O8+$delta$ (Bi2212) single crystals for the terahertz (THz) detection. For the manufacturing of the microbolometer chips, Bi2212 single crystals were transferred on substrate in the thin film like form and electron beam lithography, ion beam etching techniques were used. Resistance versus temperature behavior of the bolometer chips were performed by four probe technique in liquid nitrogen cryostat. Bi2212 microchips were integrated and characterized using in our custom-designed cryogenic bolometer system instead of expensive and massive cooling systems. The fabricated microchips significantly detected signals from the Stefan-Boltzmann lamp which includes a portion of THz radiation. The detected power and response time were studied for Bi2212 thin film like microbolometer chips. Our results demonstrated the feasibility of improved Bi2212 microchips could be used for bolometric detection for THz applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, we developed a microbolometer chip fabricated from high temperature superconducting Bi2Sr2CaCu2O8+$delta$ (Bi2212) single crystals for the terahertz (THz) detection. For the manufacturing of the microbolometer chips, Bi2212 single crystals were transferred on substrate in the thin film like form and electron beam lithography, ion beam etching techniques were used. Resistance versus temperature behavior of the bolometer chips were performed by four probe technique in liquid nitrogen cryostat. Bi2212 microchips were integrated and characterized using in our custom-designed cryogenic bolometer system instead of expensive and massive cooling systems. The fabricated microchips significantly detected signals from the Stefan-Boltzmann lamp which includes a portion of THz radiation. The detected power and response time were studied for Bi2212 thin film like microbolometer chips. Our results demonstrated the feasibility of improved Bi2212 microchips could be used for bolometric detection for THz applications. |
Kandemir, Zafer; Mayda, Selma; Bulut, Nejat: Electronic structure and correlations of vitamin B12 studied within the Haldane-Anderson impurity model. The European Physical Journal B, 89 (5), pp. 113, 2016, ISSN: 1434-6036. (Type: Journal Article | Abstract | Links | BibTeX) @article{kandemir2016, title = {Electronic structure and correlations of vitamin B12 studied within the Haldane-Anderson impurity model}, author = {Zafer Kandemir and Selma Mayda and Nejat Bulut}, url = {https://doi.org/10.1140/epjb/e2016-60702-x}, doi = {10.1140/epjb/e2016-60702-x}, issn = {1434-6036}, year = {2016}, date = {2016-05-02}, journal = {The European Physical Journal B}, volume = {89}, number = {5}, pages = {113}, abstract = {We study the electronic structure and correlations of vitamin B12 (cyanocobalamine) by using theframework of the multi-orbital single-impurity Haldane-Anderson model of atransition-metal impurity in a semiconductor host. The parameters of the effectiveHaldane-Anderson model are obtained within the Hartree-Fock (HF) approximation. Thequantum Monte Carlo (QMC) technique is then used to calculate the one-electron andmagnetic correlation functions of this effective model. We observe that new states forminside the semiconductor gap found by HF due to the intra-orbital Coulomb interaction atthe impurity 3d orbitals. In particular, the lowest unoccupiedstates correspond to an impurity bound state, which consists of states from mainly the CNaxial ligand and the corrin ring as well as the Co eg-like orbitals. We alsoobserve that the Cothinspace(3d) orbitals can develop antiferromagneticcorrelations with the surrounding atoms depending on the filling of the impurity boundstates. In addition, we make comparisons of the HF+QMC data with the density functionaltheory calculations. We also discuss the photoabsorption spectrum of cyanocobalamine.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the electronic structure and correlations of vitamin B12 (cyanocobalamine) by using theframework of the multi-orbital single-impurity Haldane-Anderson model of atransition-metal impurity in a semiconductor host. The parameters of the effectiveHaldane-Anderson model are obtained within the Hartree-Fock (HF) approximation. Thequantum Monte Carlo (QMC) technique is then used to calculate the one-electron andmagnetic correlation functions of this effective model. We observe that new states forminside the semiconductor gap found by HF due to the intra-orbital Coulomb interaction atthe impurity 3d orbitals. In particular, the lowest unoccupiedstates correspond to an impurity bound state, which consists of states from mainly the CNaxial ligand and the corrin ring as well as the Co eg-like orbitals. We alsoobserve that the Cothinspace(3d) orbitals can develop antiferromagneticcorrelations with the surrounding atoms depending on the filling of the impurity boundstates. In addition, we make comparisons of the HF+QMC data with the density functionaltheory calculations. We also discuss the photoabsorption spectrum of cyanocobalamine. |
Berber, Emine; Horzum, Nesrin; Hazer, Baki; Demir, Mustafa M: Solution Electrospinning of Polypropylene-based Fibers and Their Application in Catalysis. FIBERS AND POLYMERS, 17 (5), pp. 760-768, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000376685800014b, title = {Solution Electrospinning of Polypropylene-based Fibers and Their Application in Catalysis}, author = {Emine Berber and Nesrin Horzum and Baki Hazer and Mustafa M Demir}, url = {https://link.springer.com/article/10.1007/s12221-016-6183-7}, year = {2016}, date = {2016-05-01}, journal = {FIBERS AND POLYMERS}, volume = {17}, number = {5}, pages = {760-768}, abstract = {Since the dissolution of polyolefins is a chronic problem, melt processing has been tacitly accepted as an obligation. In this work, polypropylene (PP) was modified on molecular level incorporating poly(ethylene glycol) (PEG) as graft segment (PP-g-PEG) in a range of 6 to 9 mol%. Gold nanoparticles were nucleated in the presence of the copolymer chains via redox reaction. The dissolution of the amphiphilic comb-type graft copolymers containing gold nanoparticles (80 nm in diameter) was achieved in toluene and successfully electrospun from its solution. The diameter of composite fibers was in the range from 0.3 to 2.5 mu m. The design of the structurally organized copolymer fiber mats provided a support medium for the nanoparticles enhancing the active surface area for the catalytic applications. The resulting composite fibers exhibited rapid catalytic reduction of methylene blue (MB) dye in the presence of sodium borohydride (NaBH4) compared to corresponding composite cast film.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Since the dissolution of polyolefins is a chronic problem, melt processing has been tacitly accepted as an obligation. In this work, polypropylene (PP) was modified on molecular level incorporating poly(ethylene glycol) (PEG) as graft segment (PP-g-PEG) in a range of 6 to 9 mol%. Gold nanoparticles were nucleated in the presence of the copolymer chains via redox reaction. The dissolution of the amphiphilic comb-type graft copolymers containing gold nanoparticles (80 nm in diameter) was achieved in toluene and successfully electrospun from its solution. The diameter of composite fibers was in the range from 0.3 to 2.5 mu m. The design of the structurally organized copolymer fiber mats provided a support medium for the nanoparticles enhancing the active surface area for the catalytic applications. The resulting composite fibers exhibited rapid catalytic reduction of methylene blue (MB) dye in the presence of sodium borohydride (NaBH4) compared to corresponding composite cast film. |
Ozer, Bahar Basak Peksen; Uz, Metin; Oymaci, Pelin; Altinkaya, Sacide Alsoy: Development of a novel strategy for controlled release of lysozyme from whey protein isolate based active food packaging films. Food Hydrocolloids, 61 , pp. 877 - 886, 2016, ISSN: 0268-005X. (Type: Journal Article | Abstract | Links | BibTeX) @article{ozer2016877, title = {Development of a novel strategy for controlled release of lysozyme from whey protein isolate based active food packaging films}, author = {Bahar Basak Peksen Ozer and Metin Uz and Pelin Oymaci and Sacide Alsoy Altinkaya}, url = {http://www.sciencedirect.com/science/article/pii/S0268005X16302892}, doi = {https://doi.org/10.1016/j.foodhyd.2016.07.001}, issn = {0268-005X}, year = {2016}, date = {2016-01-01}, journal = {Food Hydrocolloids}, volume = {61}, pages = {877 - 886}, abstract = {The purpose of this study is to develop a novel controlled release system based on pH-responsive polyacrylic acid (PAA)/lysozyme (LYS) complexes incorporated within a hydrophilic whey protein isolate (WPI) film matrix for active food packaging applications. Complex formation is simple under benign conditions that are suitable for preserving antimicrobial activity of the lysozyme. In addition, the pH-dependent charge density of complexes allowed a uniform distribution in the matrix. The properties of the complexes such as size, surface charge and hydrophilicity were varied by changing PAA/LYS ratio (0.1 and 0.3 w/w) and PAA molecular weight (2 kDa and 450 kDa). The effects of complex properties as well as mode of lysozyme incorporation into the films (100%-free, 50%-free+50%-PAA/LYS complex and 100%-PAA/LYS complex) on the LYS release rate, activity and antimicrobial efficacy of the films were investigated. The results have shown that ∼100% LYS loading into the complexes is possible regardless of PAA molecular weight or PAA/LYS ratio. Incorporating lysozyme into the film in complexed form extended its release time from less than 24 h up to 500 h and reduced its diffusivity from ∼10−9 to ∼10−13 cm2/s. The films including 50%-free-LYS+50%-PAA/LYS complex showed a 5.7 log reduction in bacterial population within 72 h whereas 100%-free-LYS containing film could not suppress Listeria innocua growth after 24 h. Overall, the results suggest that complexation of lysozyme with weak polyelectrolytes can be used as an effective strategy to achieve a long-lasting antimicrobial effect and that films prepared with such complexes have great potential as food packaging materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The purpose of this study is to develop a novel controlled release system based on pH-responsive polyacrylic acid (PAA)/lysozyme (LYS) complexes incorporated within a hydrophilic whey protein isolate (WPI) film matrix for active food packaging applications. Complex formation is simple under benign conditions that are suitable for preserving antimicrobial activity of the lysozyme. In addition, the pH-dependent charge density of complexes allowed a uniform distribution in the matrix. The properties of the complexes such as size, surface charge and hydrophilicity were varied by changing PAA/LYS ratio (0.1 and 0.3 w/w) and PAA molecular weight (2 kDa and 450 kDa). The effects of complex properties as well as mode of lysozyme incorporation into the films (100%-free, 50%-free+50%-PAA/LYS complex and 100%-PAA/LYS complex) on the LYS release rate, activity and antimicrobial efficacy of the films were investigated. The results have shown that ∼100% LYS loading into the complexes is possible regardless of PAA molecular weight or PAA/LYS ratio. Incorporating lysozyme into the film in complexed form extended its release time from less than 24 h up to 500 h and reduced its diffusivity from ∼10−9 to ∼10−13 cm2/s. The films including 50%-free-LYS+50%-PAA/LYS complex showed a 5.7 log reduction in bacterial population within 72 h whereas 100%-free-LYS containing film could not suppress Listeria innocua growth after 24 h. Overall, the results suggest that complexation of lysozyme with weak polyelectrolytes can be used as an effective strategy to achieve a long-lasting antimicrobial effect and that films prepared with such complexes have great potential as food packaging materials. |
Ocakoglu, Kasim; Okur, Salih; Aydin, Hasan; Emen, Fatih Mehmet: The effect of annealing temperature on the optical properties of a ruthenium complex thin film. Thin Solid Films, 612 , pp. 225 - 230, 2016, ISSN: 0040-6090. (Type: Journal Article | Abstract | Links | BibTeX) @article{ocakoglu2016225, title = {The effect of annealing temperature on the optical properties of a ruthenium complex thin film}, author = {Kasim Ocakoglu and Salih Okur and Hasan Aydin and Fatih Mehmet Emen}, url = {http://www.sciencedirect.com/science/article/pii/S0040609016302474}, doi = {https://doi.org/10.1016/j.tsf.2016.06.004}, issn = {0040-6090}, year = {2016}, date = {2016-01-01}, journal = {Thin Solid Films}, volume = {612}, pages = {225 - 230}, abstract = {The stability of the optical parameters of a ruthenium polypyridyl complex (Ru-PC K314) film under varying annealing temperatures between 278K and 673K was investigated. The ruthenium polypyridyl complex thin film was prepared on a quartz substrate by drop casting technique. The transmission of the film was recorded by using Ultraviolet/Visible/Near Infrared spectrophotometer and the optical band gap energy of the as-deposited film was determined around 2.20eV. The optical parameters such as refractive index, extinction coefficient, and dielectric constant of the film were determined and the annealing effect on these parameters was investigated. The results show that Ru PC K314 film is quite stable up to 595K, and the rate of the optical band gap energy change was found to be 5.23×10−5eV/K. Furthermore, the thermal analysis studies were carried out in the range 298–673K. The Differential Thermal Analysis/Thermal Gravimmetry/Differantial Thermal Gravimmetry curves show that the decomposition is incomplete in the temperature range 298–673K. Ru-PC K314 is thermally stable up to 387K. The decomposition starts at 387K with elimination of functional groups such as CO2, CO molecules and SO3H group was eliminated between 614K and 666K.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The stability of the optical parameters of a ruthenium polypyridyl complex (Ru-PC K314) film under varying annealing temperatures between 278K and 673K was investigated. The ruthenium polypyridyl complex thin film was prepared on a quartz substrate by drop casting technique. The transmission of the film was recorded by using Ultraviolet/Visible/Near Infrared spectrophotometer and the optical band gap energy of the as-deposited film was determined around 2.20eV. The optical parameters such as refractive index, extinction coefficient, and dielectric constant of the film were determined and the annealing effect on these parameters was investigated. The results show that Ru PC K314 film is quite stable up to 595K, and the rate of the optical band gap energy change was found to be 5.23×10−5eV/K. Furthermore, the thermal analysis studies were carried out in the range 298–673K. The Differential Thermal Analysis/Thermal Gravimmetry/Differantial Thermal Gravimmetry curves show that the decomposition is incomplete in the temperature range 298–673K. Ru-PC K314 is thermally stable up to 387K. The decomposition starts at 387K with elimination of functional groups such as CO2, CO molecules and SO3H group was eliminated between 614K and 666K. |
Karakaya, Merve; Bilgilisoy, Elif; Arı, Ozan; Selamet, Yusuf: Surface roughness estimation of MBE grown CdTe/GaAs(211)B by ex-situ spectroscopic ellipsometry. AIP Advances, 6 (7), pp. 075111, 2016. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/1.4959223, title = {Surface roughness estimation of MBE grown CdTe/GaAs(211)B by ex-situ spectroscopic ellipsometry}, author = {Merve Karakaya and Elif Bilgilisoy and Ozan Arı and Yusuf Selamet}, url = {https://doi.org/10.1063/1.4959223}, doi = {10.1063/1.4959223}, year = {2016}, date = {2016-01-01}, journal = {AIP Advances}, volume = {6}, number = {7}, pages = {075111}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Oymaci, Pelin; Altinkaya, Sacide Alsoy: Improvement of barrier and mechanical properties of whey protein isolate based food packaging films by incorporation of zein nanoparticles as a novel bionanocomposite. Food Hydrocolloids, 54 , pp. 1 - 9, 2016, ISSN: 0268-005X. (Type: Journal Article | Abstract | Links | BibTeX) @article{oymaci20161, title = {Improvement of barrier and mechanical properties of whey protein isolate based food packaging films by incorporation of zein nanoparticles as a novel bionanocomposite}, author = {Pelin Oymaci and Sacide Alsoy Altinkaya}, url = {http://www.sciencedirect.com/science/article/pii/S0268005X15300758}, doi = {https://doi.org/10.1016/j.foodhyd.2015.08.030}, issn = {0268-005X}, year = {2016}, date = {2016-01-01}, journal = {Food Hydrocolloids}, volume = {54}, pages = {1 - 9}, abstract = {In this study, whey protein isolate (WPI) based bio-nanocomposite films embedded with zein nanoparticles (ZNP) were prepared by solution casting. Nanoparticles were coated with sodium caseinate to obtain a uniform distribution in the films. The mechanical, water vapor barrier, surface wetting, morphological and viscoelastic properties of the films were investigated. The addition of ZNP significantly improved the water vapor barrier and mechanical properties of the WPI without adversely affecting the elongation of the films. Dynamical mechanical analysis and contact angle measurements revealed that upon addition of the nanoparticles, the fractional free volume and hydrophilicity of the WPI films decreased. Sodium caseinate containing both hydrophilic and hydrophobic groups created an efficient interface between the hydrophobic ZNP and hydrophilic WPI matrix, allowing for a homogeneous distribution of nanoparticles even at very high loading levels as evidenced by the scanning electron microscope (SEM) and atomic force microscopy (AFM) images. The WPI/ZNP nanocomposite films can potentially become effective food packaging materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, whey protein isolate (WPI) based bio-nanocomposite films embedded with zein nanoparticles (ZNP) were prepared by solution casting. Nanoparticles were coated with sodium caseinate to obtain a uniform distribution in the films. The mechanical, water vapor barrier, surface wetting, morphological and viscoelastic properties of the films were investigated. The addition of ZNP significantly improved the water vapor barrier and mechanical properties of the WPI without adversely affecting the elongation of the films. Dynamical mechanical analysis and contact angle measurements revealed that upon addition of the nanoparticles, the fractional free volume and hydrophilicity of the WPI films decreased. Sodium caseinate containing both hydrophilic and hydrophobic groups created an efficient interface between the hydrophobic ZNP and hydrophilic WPI matrix, allowing for a homogeneous distribution of nanoparticles even at very high loading levels as evidenced by the scanning electron microscope (SEM) and atomic force microscopy (AFM) images. The WPI/ZNP nanocomposite films can potentially become effective food packaging materials. |
Moghtader, Farzaneh; Congur, Gulsah; Zareie, Hadi M; Erdem, Arzum; Piskin, Erhan: Impedimetric detection of pathogenic bacteria with bacteriophages using gold nanorod deposited graphite electrodes. RSC Adv., 6 , pp. 97832-97839, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{C6RA18884B, title = {Impedimetric detection of pathogenic bacteria with bacteriophages using gold nanorod deposited graphite electrodes}, author = {Farzaneh Moghtader and Gulsah Congur and Hadi M Zareie and Arzum Erdem and Erhan Piskin}, url = {http://dx.doi.org/10.1039/C6RA18884B}, doi = {10.1039/C6RA18884B}, year = {2016}, date = {2016-01-01}, journal = {RSC Adv.}, volume = {6}, pages = {97832-97839}, publisher = {The Royal Society of Chemistry}, abstract = {Electrochemical impedance spectroscopy (EIS) is applied for the detection of bacteria using bacteriophages as a bioprobe together with gold nanorods (GNRs). Escherichia coli – E. coli K12 was used as a model target bacteria and also for the propagation of its specific T4-phages. Gold nanorods (GNRs) were synthesized via a two-step protocol and characterized using different techniques. EIS measurements were conducted in an electrochemical cell consisting of a three electrode system. Single-use pencil graphite electrodes (PGE) were modified by the physical adsorption of GNRs to increase their interfacial conductivity and therefore sensitivity for impedimetric measurements. Therefore, interfacial charge-transfer resistance values (Rct) sharply decreased after GNRs deposition. Phages were adsorbed on these electrodes via a simple incubation protocol at room temperature, which resulted in an increase in Rct values, which was concluded to be as a result of nonconductive phage layers. These phage-carrying GNRs–PGEs were used for impedimetric detection of the target bacteria, E. coli. Significant increases at the Rct values were observed which were attributed to the insulation effects of the adsorbed bacterial layers. This increase was even more when the bacterial concentrations were higher. In the case of the non-target bacteria Staphylococcus aureus (S. aureus), conductivity noticeable decreases (due to nonspecific adsorption). However, in the case of E. coli, the Rct value increase is time dependent and reaches maximum in about 25–30 min, then decreases gradually as a result of bacterial lysis due to phage invasion on the electrode surfaces. In contrast, there were no time dependent changes with the non-target bacteria S. aureus (no infection and no lytic activity). It is concluded that the target bacteria could be detected using this very simple and inexpensive detection protocol with a minimum detection limit of 103 CFU mL−1 in approximately 100 μL bacterial suspension.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrochemical impedance spectroscopy (EIS) is applied for the detection of bacteria using bacteriophages as a bioprobe together with gold nanorods (GNRs). Escherichia coli – E. coli K12 was used as a model target bacteria and also for the propagation of its specific T4-phages. Gold nanorods (GNRs) were synthesized via a two-step protocol and characterized using different techniques. EIS measurements were conducted in an electrochemical cell consisting of a three electrode system. Single-use pencil graphite electrodes (PGE) were modified by the physical adsorption of GNRs to increase their interfacial conductivity and therefore sensitivity for impedimetric measurements. Therefore, interfacial charge-transfer resistance values (Rct) sharply decreased after GNRs deposition. Phages were adsorbed on these electrodes via a simple incubation protocol at room temperature, which resulted in an increase in Rct values, which was concluded to be as a result of nonconductive phage layers. These phage-carrying GNRs–PGEs were used for impedimetric detection of the target bacteria, E. coli. Significant increases at the Rct values were observed which were attributed to the insulation effects of the adsorbed bacterial layers. This increase was even more when the bacterial concentrations were higher. In the case of the non-target bacteria Staphylococcus aureus (S. aureus), conductivity noticeable decreases (due to nonspecific adsorption). However, in the case of E. coli, the Rct value increase is time dependent and reaches maximum in about 25–30 min, then decreases gradually as a result of bacterial lysis due to phage invasion on the electrode surfaces. In contrast, there were no time dependent changes with the non-target bacteria S. aureus (no infection and no lytic activity). It is concluded that the target bacteria could be detected using this very simple and inexpensive detection protocol with a minimum detection limit of 103 CFU mL−1 in approximately 100 μL bacterial suspension. |
Güner, Tuğrul; Köseoğlu, Devrim; Demir, Mustafa M: Multilayer design of hybrid phosphor film for application in LEDs. Optical Materials, 60 , pp. 422 - 430, 2016, ISSN: 0925-3467. (Type: Journal Article | Abstract | Links | BibTeX) @article{guner2016422b, title = {Multilayer design of hybrid phosphor film for application in LEDs}, author = {Tuğrul Güner and Devrim Köseoğlu and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S0925346716304414}, doi = {https://doi.org/10.1016/j.optmat.2016.08.023}, issn = {0925-3467}, year = {2016}, date = {2016-01-01}, journal = {Optical Materials}, volume = {60}, pages = {422 - 430}, abstract = {Crosslinked polydimethylsiloxane (PDMS) composite coatings containing luminescent micrometer-sized yellow Y3Al5O12:Ce3+ (YAG:Ce3+) particles were prepared by spraying for potential applications in solid-state lighting. Blue light was down converted by phosphor particles to produce white light, yet poor color properties of YAG:Ce3+ stemmed from a deficiency of red. When nitride-based red phosphor was simply blended into the system, the electrostatic interaction of negatively charged YAG:Ce3+ and positively charged red phosphor particles caused remarkable clustering and heterogeneity in particle dispersion. Consequently, the light is dominantly blue and shifted to cold white. In other case, phosphor particles were sprayed onto the diffused polycarbonate substrate in stacked layers. Coatings with >80% inorganic content by mass with a thickness of 60 μm were subjected to thermal crosslinking, which the presence of the phosphor particles obstructed, presumably due to the hindrance of large phosphor particles in the diffusion of PDMS precursors. The coating of YAG:Ce3+ first followed by red phosphor in stacked layers produced better light output and color properties than the coating obtained by spraying the mixture at once. Monte Carlo simulation validated the hypothesis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Crosslinked polydimethylsiloxane (PDMS) composite coatings containing luminescent micrometer-sized yellow Y3Al5O12:Ce3+ (YAG:Ce3+) particles were prepared by spraying for potential applications in solid-state lighting. Blue light was down converted by phosphor particles to produce white light, yet poor color properties of YAG:Ce3+ stemmed from a deficiency of red. When nitride-based red phosphor was simply blended into the system, the electrostatic interaction of negatively charged YAG:Ce3+ and positively charged red phosphor particles caused remarkable clustering and heterogeneity in particle dispersion. Consequently, the light is dominantly blue and shifted to cold white. In other case, phosphor particles were sprayed onto the diffused polycarbonate substrate in stacked layers. Coatings with >80% inorganic content by mass with a thickness of 60 μm were subjected to thermal crosslinking, which the presence of the phosphor particles obstructed, presumably due to the hindrance of large phosphor particles in the diffusion of PDMS precursors. The coating of YAG:Ce3+ first followed by red phosphor in stacked layers produced better light output and color properties than the coating obtained by spraying the mixture at once. Monte Carlo simulation validated the hypothesis. |
Aşkın, Görkem; Çeçen, Volkan; Ünlütürk, Seçil Sevim; Özçelik, Serdar; Demir, Mustafa M: Enthalpy-driven selective loading of CdSe0.75S0.25 nanoalloys in triblock copolymer polystyrene-b-polyisoprene-b-polystyrene. Materials Today Communications, 8 , pp. 91 - 99, 2016, ISSN: 2352-4928. (Type: Journal Article | Abstract | Links | BibTeX) @article{askin201691b, title = {Enthalpy-driven selective loading of CdSe0.75S0.25 nanoalloys in triblock copolymer polystyrene-b-polyisoprene-b-polystyrene}, author = {Görkem Aşkın and Volkan Çeçen and Seçil Sevim Ünlütürk and Serdar Özçelik and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S2352492816300538}, doi = {https://doi.org/10.1016/j.mtcomm.2016.06.004}, issn = {2352-4928}, year = {2016}, date = {2016-01-01}, journal = {Materials Today Communications}, volume = {8}, pages = {91 - 99}, abstract = {CdSe0.75S0.25 nanoalloys were blended with asymmetric triblock copolymer of polystyrene-b-polyisoprene-b-polystyrene(PS-SIS) in tetrahydrofuran. The fraction of styrene block varies from 14 to 22% with respect to isoprene by mass. The morphology of the copolymer cast film experiences a phase change from cylinder to lamella. CdSe0.75S0.25 nanoalloys were prepared by two-phase method. The surface of the nanoalloys was capped by either oleic acid (OA) or n-tri-octylphosphonic acid (TOPO) in situ. The mean diameter of the alloyed particles is around 12nm in both systems. The chemical nature of the nanoalloy surface was found to influence the dispersion of the particles over polymer volume. The size of the nanoalloy domains in PS is 50nm, on average, consisting of approximately 0.7wt% nanoalloys. However, the size of the nanoalloy domains is smaller when they are loaded into PS-SIS. The structure formation is predominantly determined by enthalpic compatibilization. Atomic force microscopy results suggest that the nanoalloys capped with TOPO sequester into PS-rich domains and enlarge the domain. On the other hand, the ones capped with OA prefer to locate in polyisoprene domains. The increase of particles over 1.0wt% distorts the lamella structure.}, keywords = {}, pubstate = {published}, tppubtype = {article} } CdSe0.75S0.25 nanoalloys were blended with asymmetric triblock copolymer of polystyrene-b-polyisoprene-b-polystyrene(PS-SIS) in tetrahydrofuran. The fraction of styrene block varies from 14 to 22% with respect to isoprene by mass. The morphology of the copolymer cast film experiences a phase change from cylinder to lamella. CdSe0.75S0.25 nanoalloys were prepared by two-phase method. The surface of the nanoalloys was capped by either oleic acid (OA) or n-tri-octylphosphonic acid (TOPO) in situ. The mean diameter of the alloyed particles is around 12nm in both systems. The chemical nature of the nanoalloy surface was found to influence the dispersion of the particles over polymer volume. The size of the nanoalloy domains in PS is 50nm, on average, consisting of approximately 0.7wt% nanoalloys. However, the size of the nanoalloy domains is smaller when they are loaded into PS-SIS. The structure formation is predominantly determined by enthalpic compatibilization. Atomic force microscopy results suggest that the nanoalloys capped with TOPO sequester into PS-rich domains and enlarge the domain. On the other hand, the ones capped with OA prefer to locate in polyisoprene domains. The increase of particles over 1.0wt% distorts the lamella structure. |
Isık, Tuğba; Horzum, Nesrin; Yıldız, Hakan Ü; Liedberg, Bo; Demir, Mustafa M: Utilization of Electrospun Polystyrene Membranes as a Preliminary Step for Rapid Diagnosis. Macromolecular Materials and Engineering, 301 (7), pp. 827-835, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/mame.201600127b, title = {Utilization of Electrospun Polystyrene Membranes as a Preliminary Step for Rapid Diagnosis}, author = {Tuğba Isık and Nesrin Horzum and Hakan Ü Yıldız and Bo Liedberg and Mustafa M Demir}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/mame.201600127}, doi = {10.1002/mame.201600127}, year = {2016}, date = {2016-01-01}, journal = {Macromolecular Materials and Engineering}, volume = {301}, number = {7}, pages = {827-835}, abstract = {Recent advances in clinical practice drive deoxyribonucleic acid (DNA) as an important class of biomarker. Monitoring the change in their concentration suggests the initiation and/or progression of various disorders. However, low quantity of DNA biomarkers in body fluids requires a delicate isolation methodology that provides efficient separation and easy handling. This study describes a newer-generation separation technology relying on electrospun fibers of sub-micrometer diameter of a commodity polymer for DNA biomarkers in simulative serum. Fibrous polystyrene membranes are prepared by electrospinning and they are subjected to post-modification with Au. The composite membranes may provide a convenient environment for the removal of bovine serum albumin (BSA) from BSA and DNA mixtures. The eluent can be used as an efficient tool for detection of DNA biomarkers associated with diagnosis of numerous life-threatening diseases.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recent advances in clinical practice drive deoxyribonucleic acid (DNA) as an important class of biomarker. Monitoring the change in their concentration suggests the initiation and/or progression of various disorders. However, low quantity of DNA biomarkers in body fluids requires a delicate isolation methodology that provides efficient separation and easy handling. This study describes a newer-generation separation technology relying on electrospun fibers of sub-micrometer diameter of a commodity polymer for DNA biomarkers in simulative serum. Fibrous polystyrene membranes are prepared by electrospinning and they are subjected to post-modification with Au. The composite membranes may provide a convenient environment for the removal of bovine serum albumin (BSA) from BSA and DNA mixtures. The eluent can be used as an efficient tool for detection of DNA biomarkers associated with diagnosis of numerous life-threatening diseases. |
Horzum, Nesrin; Mete, Derya; Karakuş, Erman; Üçüncü, Muhammed; Emrullahoğlu, Mustafa; Demir, Mustafa M: Rhodamine-Immobilised Electrospun Chitosan Nanofibrous Material as a Fluorescence Turn-On Hg2+ Sensor. ChemistrySelect, 1 (5), pp. 896-900, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/slct.201600027b, title = {Rhodamine-Immobilised Electrospun Chitosan Nanofibrous Material as a Fluorescence Turn-On Hg2+ Sensor}, author = {Nesrin Horzum and Derya Mete and Erman Karakuş and Muhammed Üçüncü and Mustafa Emrullahoğlu and Mustafa M Demir}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/slct.201600027}, doi = {10.1002/slct.201600027}, year = {2016}, date = {2016-01-01}, journal = {ChemistrySelect}, volume = {1}, number = {5}, pages = {896-900}, abstract = {Abstract A turn-on fluorescence sensing system for mercuric (Hg2+) ions relying on a modified rhodamine B–chitosan fluorophore moiety was developed. This novel sensing approach relies on the simultaneous electrospinning of chitosan and rhodamine B hydrazide with phenylisothiocyanate functionality in hexafluoroisopropanol solution at 3.4 kV cm−1. The electrospun mats exhibited not only considerably enhanced fluorescence intensity in the presence of mercury ions, a result attributed to the ring opening of the spirolactam unit of the rhodamine-based fluorophore, but also a remarkably high sensitivity and selectivity toward Hg2+. In effect, the strategy has the potential to open new avenues in the design and development of other high-performance nanofibrous sensing materials for detecting target metal species of environmental interest.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract A turn-on fluorescence sensing system for mercuric (Hg2+) ions relying on a modified rhodamine B–chitosan fluorophore moiety was developed. This novel sensing approach relies on the simultaneous electrospinning of chitosan and rhodamine B hydrazide with phenylisothiocyanate functionality in hexafluoroisopropanol solution at 3.4 kV cm−1. The electrospun mats exhibited not only considerably enhanced fluorescence intensity in the presence of mercury ions, a result attributed to the ring opening of the spirolactam unit of the rhodamine-based fluorophore, but also a remarkably high sensitivity and selectivity toward Hg2+. In effect, the strategy has the potential to open new avenues in the design and development of other high-performance nanofibrous sensing materials for detecting target metal species of environmental interest. |
Kandemir, Ali; Yapicioglu, Haluk; Kinaci, Alper; Çağın, Tahir; Sevik, Cem: Thermal transport properties of MoS2and MoSe2monolayers. Nanotechnology, 27 (5), pp. 055703, 2016. (Type: Journal Article | Abstract | Links | BibTeX) @article{kandemir2016d, title = {Thermal transport properties of MoS2and MoSe2monolayers}, author = {Ali Kandemir and Haluk Yapicioglu and Alper Kinaci and Tahir Çağın and Cem Sevik}, url = {https://doi.org/10.1088%2F0957-4484%2F27%2F5%2F055703}, doi = {10.1088/0957-4484/27/5/055703}, year = {2016}, date = {2016-01-01}, journal = {Nanotechnology}, volume = {27}, number = {5}, pages = {055703}, publisher = {IOP Publishing}, abstract = {The isolation of single- to few-layer transition metal dichalcogenides opens new directions in the application of two-dimensional materials to nanoelectronics. The characterization of thermal transport in these new low-dimensional materials is needed for their efficient implementation, either for general overheating issues or specific applications in thermoelectric devices. In this study, the lattice thermal conductivities of single-layer MoS2 and MoSe2 are evaluated using classical molecular dynamics methods. The interactions between atoms are defined by Stillinger–Weber-type empirical potentials that are developed to represent the structural, mechanical, and vibrational properties of the given materials. In the parameterization of the potentials, a stochastic optimization algorithm, namely particle swarm optimization, is utilized. The final parameter sets produce quite consistent results with density functional theory in terms of lattice parameters, bond distances, elastic constants, and vibrational properties of both single-layer MoS2 and MoSe2. The predicted thermal properties of both materials are in very good agreement with earlier first-principles calculations. The discrepancies between the calculations and experimental measurements are most probably caused by the pristine nature of the structures in our simulations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The isolation of single- to few-layer transition metal dichalcogenides opens new directions in the application of two-dimensional materials to nanoelectronics. The characterization of thermal transport in these new low-dimensional materials is needed for their efficient implementation, either for general overheating issues or specific applications in thermoelectric devices. In this study, the lattice thermal conductivities of single-layer MoS2 and MoSe2 are evaluated using classical molecular dynamics methods. The interactions between atoms are defined by Stillinger–Weber-type empirical potentials that are developed to represent the structural, mechanical, and vibrational properties of the given materials. In the parameterization of the potentials, a stochastic optimization algorithm, namely particle swarm optimization, is utilized. The final parameter sets produce quite consistent results with density functional theory in terms of lattice parameters, bond distances, elastic constants, and vibrational properties of both single-layer MoS2 and MoSe2. The predicted thermal properties of both materials are in very good agreement with earlier first-principles calculations. The discrepancies between the calculations and experimental measurements are most probably caused by the pristine nature of the structures in our simulations. |
Basoglu, Harun; Bilgin, Mehmet Dincer; Demir, Mustafa Muammer: Protoporphyrin IX-loaded magnetoliposomes as a potential drug delivery system for photodynamic therapy: Fabrication, characterization and in vitro study. Photodiagnosis and Photodynamic Therapy, 13 , pp. 81 - 90, 2016, ISSN: 1572-1000. (Type: Journal Article | Links | BibTeX) @article{basoglu201681, title = {Protoporphyrin IX-loaded magnetoliposomes as a potential drug delivery system for photodynamic therapy: Fabrication, characterization and in vitro study}, author = {Harun Basoglu and Mehmet Dincer Bilgin and Mustafa Muammer Demir}, url = {http://www.sciencedirect.com/science/article/pii/S1572100015300612}, doi = {https://doi.org/10.1016/j.pdpdt.2015.12.010}, issn = {1572-1000}, year = {2016}, date = {2016-01-01}, journal = {Photodiagnosis and Photodynamic Therapy}, volume = {13}, pages = {81 - 90}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2015 |
Ozceri, Elif; Selamet, Yusuf: Influence of buffer layers on Ni thin film structure and graphene growth by CVD. Journal of Physics D: Applied Physics, 48 (45), pp. 455302, 2015. (Type: Journal Article | Abstract | Links | BibTeX) @article{ozceri2015, title = {Influence of buffer layers on Ni thin film structure and graphene growth by CVD}, author = {Elif Ozceri and Yusuf Selamet}, url = {https://doi.org/10.1088%2F0022-3727%2F48%2F45%2F455302}, doi = {10.1088/0022-3727/48/45/455302}, year = {2015}, date = {2015-10-01}, journal = {Journal of Physics D: Applied Physics}, volume = {48}, number = {45}, pages = {455302}, publisher = {IOP Publishing}, abstract = {Buffer and/or adhesive layers were used to decrease the dewetting of Ni thin film at graphene growth temperatures of around 900 °C. Depositing a thin buffer (Al2O3) layer onto SiO2/Si substrate significantly reduced the dewetting effect and surface roughness of Ni catalyst film. Thin adhesive (Cr) layers with or without Al2O3 buffer layers increased the texturing in (1 1 1) orientation, which was promoted by growing at an elevated temperature (450 °C). The effects of pretreatment and growth temperature on crystal orientation, grain size and surface roughness of Ni film were analyzed. Our results indicated a large positive correlation coefficient between the film thickness and surface roughness for thinner and non-buffered films, and a negative correlation coefficient between the thickness and 900 °C -annealed film roughness for thicker and buffered films. The graphene coverage was greatly improved over the films grown with Al2O3 and/or Cr layers. In summary, we suggest that growing high quality, large area, 1- or 2-layer graphene on polycrystalline Ni transition metal thin film is optimized by using Al2O3 and/or Cr layers to reduce Ni dewetting, surface roughness, and groove depth while controlling grain size and texturing in (1 1 1) orientation by annealing at 900 °C.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Buffer and/or adhesive layers were used to decrease the dewetting of Ni thin film at graphene growth temperatures of around 900 °C. Depositing a thin buffer (Al2O3) layer onto SiO2/Si substrate significantly reduced the dewetting effect and surface roughness of Ni catalyst film. Thin adhesive (Cr) layers with or without Al2O3 buffer layers increased the texturing in (1 1 1) orientation, which was promoted by growing at an elevated temperature (450 °C). The effects of pretreatment and growth temperature on crystal orientation, grain size and surface roughness of Ni film were analyzed. Our results indicated a large positive correlation coefficient between the film thickness and surface roughness for thinner and non-buffered films, and a negative correlation coefficient between the thickness and 900 °C -annealed film roughness for thicker and buffered films. The graphene coverage was greatly improved over the films grown with Al2O3 and/or Cr layers. In summary, we suggest that growing high quality, large area, 1- or 2-layer graphene on polycrystalline Ni transition metal thin film is optimized by using Al2O3 and/or Cr layers to reduce Ni dewetting, surface roughness, and groove depth while controlling grain size and texturing in (1 1 1) orientation by annealing at 900 °C. |
Koseoglu, Hasan; Turkoglu, Fulya; Kurt, Metin; Yaman, Mutlu D; Akca, Fatime G; Aygun, Gulnur; Ozyuzer, Lutfi: Improvement of optical and electrical properties of ITO thin films by
electro-annealing. VACUUM, 120 (B, SI), pp. 8-13, 2015, ISSN: 0042-207X, (Conference and Exhibition on Science and Applications of Thin Films
(SATF), Cesme, TURKEY, SEP 15-19, 2014). (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000361405300003, title = {Improvement of optical and electrical properties of ITO thin films by electro-annealing}, author = {Hasan Koseoglu and Fulya Turkoglu and Metin Kurt and Mutlu D Yaman and Fatime G Akca and Gulnur Aygun and Lutfi Ozyuzer}, doi = {10.1016/j.vacuum.2015.06.027}, issn = {0042-207X}, year = {2015}, date = {2015-10-01}, journal = {VACUUM}, volume = {120}, number = {B, SI}, pages = {8-13}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {The effect of electro-annealing in vacuum and air on the optical and electrical properties of ITO thin films grown by large area DC magnetron sputtering was investigated. Moreover, the performances of the electro-annealed ITO thin films in vacuum and air were compared. Electro-annealing was performed by applying 0.75, 1.00, 1.25 and 1.50 A constant ac current to the ITO thin films. It was observed that the crystallinity of the films was better for the ITO thin films electro-annealed in vacuum. The changes in sheet resistance of electro-annealed ITO thin films with applied currents were detailed. The transmittance of the films increased for both electro-annealing in vacuum and air. A correlation between band-gap and resistivity for all of the electro-annealed thin films was observed. (C) 2015 Elsevier Ltd. All rights reserved.}, note = {Conference and Exhibition on Science and Applications of Thin Films (SATF), Cesme, TURKEY, SEP 15-19, 2014}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of electro-annealing in vacuum and air on the optical and electrical properties of ITO thin films grown by large area DC magnetron sputtering was investigated. Moreover, the performances of the electro-annealed ITO thin films in vacuum and air were compared. Electro-annealing was performed by applying 0.75, 1.00, 1.25 and 1.50 A constant ac current to the ITO thin films. It was observed that the crystallinity of the films was better for the ITO thin films electro-annealed in vacuum. The changes in sheet resistance of electro-annealed ITO thin films with applied currents were detailed. The transmittance of the films increased for both electro-annealing in vacuum and air. A correlation between band-gap and resistivity for all of the electro-annealed thin films was observed. (C) 2015 Elsevier Ltd. All rights reserved. |
Tüzüner, Şeyda; Demir, Mustafa M: Dispersion of organophilic Ag nanoparticles in PS-PMMA blends. Materials Chemistry and Physics, 162 , pp. 692 - 699, 2015, ISSN: 0254-0584. (Type: Journal Article | Abstract | Links | BibTeX) @article{tuzuner2015692, title = {Dispersion of organophilic Ag nanoparticles in PS-PMMA blends}, author = {Şeyda Tüzüner and Mustafa M Demir}, url = {http://www.sciencedirect.com/science/article/pii/S025405841530184X}, doi = {https://doi.org/10.1016/j.matchemphys.2015.06.044}, issn = {0254-0584}, year = {2015}, date = {2015-01-01}, journal = {Materials Chemistry and Physics}, volume = {162}, pages = {692 - 699}, abstract = {The preparation of stable composites with well-controlled particle location is one of the challenges in formulating new polymer/nanoparticle mixtures. In this study, cetyltriammonium bromide (CTAB)-capped monodisperse Ag nanoparticles were prepared and mixed with an equimass blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) in solution. The surface of the blend film without nanoparticles showed spherical pits with a size of 4.5 μm in diameter. The integration of CTAB-capped nanoparticles into the blend film developed surface bumps with a size of 0.4 μm in diameter. The organophilic Ag nanoparticles were distributed heterogeneously in the immiscible PS-PMMA blend. When the diameter of particle domains reached approximately 20 nm, particles were preferentially located at the interface of the PS and PMMA domains. Larger particle domains with a diameter of 90 nm were found to be in the PMMA-rich phase. Isothermal post-treatment of the PS-PMMA/Ag composite films directs the particle domains into PS domains. Thermodynamic factors that contribute to the observed morphologies are discussed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The preparation of stable composites with well-controlled particle location is one of the challenges in formulating new polymer/nanoparticle mixtures. In this study, cetyltriammonium bromide (CTAB)-capped monodisperse Ag nanoparticles were prepared and mixed with an equimass blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) in solution. The surface of the blend film without nanoparticles showed spherical pits with a size of 4.5 μm in diameter. The integration of CTAB-capped nanoparticles into the blend film developed surface bumps with a size of 0.4 μm in diameter. The organophilic Ag nanoparticles were distributed heterogeneously in the immiscible PS-PMMA blend. When the diameter of particle domains reached approximately 20 nm, particles were preferentially located at the interface of the PS and PMMA domains. Larger particle domains with a diameter of 90 nm were found to be in the PMMA-rich phase. Isothermal post-treatment of the PS-PMMA/Ag composite films directs the particle domains into PS domains. Thermodynamic factors that contribute to the observed morphologies are discussed. |
Horzum, Nesrin; Mari, Margherita; Wagner, Manfred; Fortunato, Giuseppino; Popa, Ana-Maria; Demir, Mustafa M; Landfester, Katharina; Crespy, Daniel; Muñoz-Espí, Rafael: Controlled surface mineralization of metal oxides on nanofibers. RSC Adv., 5 , pp. 37340-37345, 2015. (Type: Journal Article | Abstract | Links | BibTeX) @article{C5RA02140E, title = {Controlled surface mineralization of metal oxides on nanofibers}, author = {Nesrin Horzum and Margherita Mari and Manfred Wagner and Giuseppino Fortunato and Ana-Maria Popa and Mustafa M Demir and Katharina Landfester and Daniel Crespy and Rafael Muñoz-Espí}, url = {http://dx.doi.org/10.1039/C5RA02140E}, doi = {10.1039/C5RA02140E}, year = {2015}, date = {2015-01-01}, journal = {RSC Adv.}, volume = {5}, pages = {37340-37345}, publisher = {The Royal Society of Chemistry}, abstract = {We report a versatile approach for the preparation of metal oxide/polymer hybrid nanofibers by in situ formation of metal oxide nanoparticles on surface-functionalized polymer fibers. Poly (styrene-co-vinylphosphonic acid) fibers were produced by electrospinning and used as supports for the in situ formation of ceria nanocrystals without further thermal treatment. The crystallization of ceria was induced by the addition of an alkaline solution to fibers loaded with the corresponding precursor. The formation of the inorganic material at the fiber surface was investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The extension of the approach to prepare polymer/titania hybrid nanofibers demonstrates its versatility.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report a versatile approach for the preparation of metal oxide/polymer hybrid nanofibers by in situ formation of metal oxide nanoparticles on surface-functionalized polymer fibers. Poly (styrene-co-vinylphosphonic acid) fibers were produced by electrospinning and used as supports for the in situ formation of ceria nanocrystals without further thermal treatment. The crystallization of ceria was induced by the addition of an alkaline solution to fibers loaded with the corresponding precursor. The formation of the inorganic material at the fiber surface was investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The extension of the approach to prepare polymer/titania hybrid nanofibers demonstrates its versatility. |
Baba, Alper; Demir, Mustafa M; Koç, Gonca A; Tuğcu, Celal: Hydrogeological properties of hyper-saline geothermal brine and application of inhibiting siliceous scale via pH modification. Geothermics, 53 , pp. 406 - 412, 2015, ISSN: 0375-6505. (Type: Journal Article | Abstract | Links | BibTeX) @article{baba2015406, title = {Hydrogeological properties of hyper-saline geothermal brine and application of inhibiting siliceous scale via pH modification}, author = {Alper Baba and Mustafa M Demir and Gonca A Koç and Celal Tuğcu}, url = {http://www.sciencedirect.com/science/article/pii/S0375650514001047}, doi = {https://doi.org/10.1016/j.geothermics.2014.08.007}, issn = {0375-6505}, year = {2015}, date = {2015-01-01}, journal = {Geothermics}, volume = {53}, pages = {406 - 412}, abstract = {Scaling is a major obstacle in harnessing of geothermal energy from the geothermal resources. This paper presents a case study for inhibition of metal silicate scaling using formic acid, harvesting more energy in particular case of Tuzla Geothermal Field (TGF), located on Biga Peninsula, in the northwestern of Turkey. TGF is 5km far from Aegean Sea and 80km south of Çanakkale. Geothermal fluid of TGF has high salinity (EC>91mS/cm) and medium temperature (reservoir temperature is 173°C). The acidification of high-salinity brine to mitigate silicate scaling is examined. Results of the study showed that a compromise between scaling and corrosion is achieved by reducing pH of brine to <6 using 55ppm formic acid.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Scaling is a major obstacle in harnessing of geothermal energy from the geothermal resources. This paper presents a case study for inhibition of metal silicate scaling using formic acid, harvesting more energy in particular case of Tuzla Geothermal Field (TGF), located on Biga Peninsula, in the northwestern of Turkey. TGF is 5km far from Aegean Sea and 80km south of Çanakkale. Geothermal fluid of TGF has high salinity (EC>91mS/cm) and medium temperature (reservoir temperature is 173°C). The acidification of high-salinity brine to mitigate silicate scaling is examined. Results of the study showed that a compromise between scaling and corrosion is achieved by reducing pH of brine to <6 using 55ppm formic acid. |
Tatlidil, D; Ucuncu, M; Akdogan, Y: Physiological concentrations of albumin favor drug binding. Phys. Chem. Chem. Phys., 17 , pp. 22678-22685, 2015. (Type: Journal Article | Links | BibTeX) @article{C5CP03583J, title = {Physiological concentrations of albumin favor drug binding}, author = {D Tatlidil and M Ucuncu and Y Akdogan}, url = {http://dx.doi.org/10.1039/C5CP03583J}, doi = {10.1039/C5CP03583J}, year = {2015}, date = {2015-01-01}, journal = {Phys. Chem. Chem. Phys.}, volume = {17}, pages = {22678-22685}, publisher = {The Royal Society of Chemistry}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Yardimci, Atike Ince; Yılmaz, Selahattin; Selamet, Yusuf: The effects of catalyst pretreatment, growth atmosphere and temperature on carbon nanotube synthesis using Co–Mo/MgO catalyst. Diamond and Related Materials, 60 , pp. 81 - 86, 2015, ISSN: 0925-9635. (Type: Journal Article | Abstract | Links | BibTeX) @article{yardimci201581, title = {The effects of catalyst pretreatment, growth atmosphere and temperature on carbon nanotube synthesis using Co–Mo/MgO catalyst}, author = {Atike Ince Yardimci and Selahattin Yılmaz and Yusuf Selamet}, url = {http://www.sciencedirect.com/science/article/pii/S0925963515300686}, doi = {https://doi.org/10.1016/j.diamond.2015.10.025}, issn = {0925-9635}, year = {2015}, date = {2015-01-01}, journal = {Diamond and Related Materials}, volume = {60}, pages = {81 - 86}, abstract = {The growth of high quality and high yield carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CVD) of CH4 over Co–Mo/MgO catalyst was investigated for different growth temperatures and H2 flow rates. It was observed that CNT yield decreased with the H2 flow rate, however, quality increased with increasing H2 flow rate. CNT yield increased for the temperatures 850–950°C but dropped significantly above 950°C. In this study, the highest yield of 1526% was obtained at the growth temperature of 950°C. The optimum H2 flow rate was 200sccm; this rate gave both high graphitization and high yield of product. Various CNT growth atmospheres including Ar, H2 and the mixture of both gases were also analyzed and it was observed that the highest quality CNTs were obtained for both pretreatment and growth carried out with H2. This gave a high yield of 292%. On the other hand, CNT growth carried out under Ar atmosphere gave higher CNT yield of 368%, however, the CNTs grown with Ar were more defective and had larger diameters. Prime novelty statement We demonstrate a sorbitol added catalysis synthesis method and importance of the ideal growth conditions to improve high quality single walled carbon nanotube yield up to 1500%.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The growth of high quality and high yield carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CVD) of CH4 over Co–Mo/MgO catalyst was investigated for different growth temperatures and H2 flow rates. It was observed that CNT yield decreased with the H2 flow rate, however, quality increased with increasing H2 flow rate. CNT yield increased for the temperatures 850–950°C but dropped significantly above 950°C. In this study, the highest yield of 1526% was obtained at the growth temperature of 950°C. The optimum H2 flow rate was 200sccm; this rate gave both high graphitization and high yield of product. Various CNT growth atmospheres including Ar, H2 and the mixture of both gases were also analyzed and it was observed that the highest quality CNTs were obtained for both pretreatment and growth carried out with H2. This gave a high yield of 292%. On the other hand, CNT growth carried out under Ar atmosphere gave higher CNT yield of 368%, however, the CNTs grown with Ar were more defective and had larger diameters. Prime novelty statement We demonstrate a sorbitol added catalysis synthesis method and importance of the ideal growth conditions to improve high quality single walled carbon nanotube yield up to 1500%. |
Tomak, A; Zareie, H M: Gold nanorod encapsulated bubbles. RSC Adv., 5 , pp. 38842-38845, 2015. (Type: Journal Article | Abstract | Links | BibTeX) @article{C5RA03240G, title = {Gold nanorod encapsulated bubbles}, author = {A Tomak and H M Zareie}, url = {http://dx.doi.org/10.1039/C5RA03240G}, doi = {10.1039/C5RA03240G}, year = {2015}, date = {2015-01-01}, journal = {RSC Adv.}, volume = {5}, pages = {38842-38845}, publisher = {The Royal Society of Chemistry}, abstract = {A simple method has been described for synthesizing gold nanorods (GNRs) encapsulated bubbles in a controlled manner. The method involves the use of nitrogen gas in the seed-mediated synthesis method routinely used for synthesis of GNRs. Control over the morphology of the nanostructures was achieved by nitrogen gas flow. The synthesized structures were examined by UV-Vis Spectroscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). New structures of this type could conceivably serve as plasmonic biosensors, nanodevices and photothermal theranostics with dual modality imaging functionality.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A simple method has been described for synthesizing gold nanorods (GNRs) encapsulated bubbles in a controlled manner. The method involves the use of nitrogen gas in the seed-mediated synthesis method routinely used for synthesis of GNRs. Control over the morphology of the nanostructures was achieved by nitrogen gas flow. The synthesized structures were examined by UV-Vis Spectroscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). New structures of this type could conceivably serve as plasmonic biosensors, nanodevices and photothermal theranostics with dual modality imaging functionality. |
İncel, Anıl; Güner, Tuğrul; Parlak, Onur; Demir, Mustafa M: Null Extinction of Ceria@silica Hybrid Particles: Transparent Polystyrene Composites. ACS Applied Materials & Interfaces, 7 (49), pp. 27539-27546, 2015, (PMID: 26594909). (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/acsami.5b09818b, title = {Null Extinction of Ceria@silica Hybrid Particles: Transparent Polystyrene Composites}, author = {Anıl İncel and Tuğrul Güner and Onur Parlak and Mustafa M Demir}, url = {https://doi.org/10.1021/acsami.5b09818}, doi = {10.1021/acsami.5b09818}, year = {2015}, date = {2015-01-01}, journal = {ACS Applied Materials & Interfaces}, volume = {7}, number = {49}, pages = {27539-27546}, note = {PMID: 26594909}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Arı, Ozan; Polat, Mustafa; Karakaya, Merve; Selamet, Yusuf: Growth and characterization of CdTe absorbers on GaAs by MBE for high concentration PV solar cells. physica status solidi c, 12 (9‐11), pp. 1211-1214, 2015. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/pssc.201510068b, title = {Growth and characterization of CdTe absorbers on GaAs by MBE for high concentration PV solar cells}, author = {Ozan Arı and Mustafa Polat and Merve Karakaya and Yusuf Selamet}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/pssc.201510068}, doi = {10.1002/pssc.201510068}, year = {2015}, date = {2015-01-01}, journal = {physica status solidi c}, volume = {12}, number = {9‐11}, pages = {1211-1214}, abstract = {Abstract CdTe based II-VI absorbers are promising candidates for high concentration PV solar cells with an ideal band gap for AM1.5 solar radiation. In this study, we propose single crystal CdTe absorbers grown on GaAs substrates with a molecular beam epitaxy (MBE) which is a clean deposition technology. We show that high quality CdTe absorber layers can be grown with full width half maximum of X-ray diffraction rocking curves (XRD RC) as low as 227 arc-seconds with 0.5% thickness uniformity that a 2 µm layer is capable of absorbing 99% of AM1.5 solar radiation. Bandgap of the CdTe absorber is found as 1.483 eV from spetroscopic ellipsometry (SE) measurements. Also, high absorption coefficient is calculated from the results, which is ∼5 x 105cm-1 in solar radiation spectrum. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract CdTe based II-VI absorbers are promising candidates for high concentration PV solar cells with an ideal band gap for AM1.5 solar radiation. In this study, we propose single crystal CdTe absorbers grown on GaAs substrates with a molecular beam epitaxy (MBE) which is a clean deposition technology. We show that high quality CdTe absorber layers can be grown with full width half maximum of X-ray diffraction rocking curves (XRD RC) as low as 227 arc-seconds with 0.5% thickness uniformity that a 2 µm layer is capable of absorbing 99% of AM1.5 solar radiation. Bandgap of the CdTe absorber is found as 1.483 eV from spetroscopic ellipsometry (SE) measurements. Also, high absorption coefficient is calculated from the results, which is ∼5 x 105cm-1 in solar radiation spectrum. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) |
2014 |
Horzum, Nesrin; Tascioglu, Didem; Ozbek, Cebrail; Okur, Salih; Demir, Mustafa M: VOC sensors based on a metal oxide nanofibrous membrane/QCM system prepared by electrospinning. NEW JOURNAL OF CHEMISTRY, 38 (12), pp. 5761-5768, 2014. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000345485000013, title = {VOC sensors based on a metal oxide nanofibrous membrane/QCM system prepared by electrospinning}, author = {Nesrin Horzum and Didem Tascioglu and Cebrail Ozbek and Salih Okur and Mustafa M Demir}, url = {https://pubs.rsc.org/en/content/articlelanding/2014/NJ/C4NJ00884G#!divAbstract}, doi = {10.1039/c4nj00884g}, year = {2014}, date = {2014-12-01}, journal = {NEW JOURNAL OF CHEMISTRY}, volume = {38}, number = {12}, pages = {5761-5768}, abstract = {We report a simple synthetic route to fabricate crystalline ZnO and CeO2/ZnO nanofibrous mats and their sensing characteristics against volatile organic compounds (VOCs) such as benzene, propanol, ethanol, and dichloromethane. Precursor fibers were fabricated by electrospinning of poly(vinyl alcohol) and metal salt(s) at 2.5 kV cm(-1) in aqueous solution. The fibers were directly deposited on the crystal surface of a quartz crystal microbalance (QCM). The crystal, which was coated by nanostructured PVA/metal precursor(s) fibers, was subjected to calcination in air at 500 degrees C for 5 h. The formation of an oxide based nanofiber mat was revealed by scanning electron microscopy and X-ray diffraction. Upon exposure of the nanofiber mats to the VOCs, the compounds adsorbed onto the surface of oxidic fibers. The physisorption of the compounds was confirmed by FTIR and QCM. Both systems showed sensitivity to the VOCs and they hold a broad promise particularly for sensing applications of volatile alcoholic compounds. The introduction of CeO2 into the ZnO structure reduced the sensitivity of ZnO most probably due to the decrement of oxygen vacancies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We report a simple synthetic route to fabricate crystalline ZnO and CeO2/ZnO nanofibrous mats and their sensing characteristics against volatile organic compounds (VOCs) such as benzene, propanol, ethanol, and dichloromethane. Precursor fibers were fabricated by electrospinning of poly(vinyl alcohol) and metal salt(s) at 2.5 kV cm(-1) in aqueous solution. The fibers were directly deposited on the crystal surface of a quartz crystal microbalance (QCM). The crystal, which was coated by nanostructured PVA/metal precursor(s) fibers, was subjected to calcination in air at 500 degrees C for 5 h. The formation of an oxide based nanofiber mat was revealed by scanning electron microscopy and X-ray diffraction. Upon exposure of the nanofiber mats to the VOCs, the compounds adsorbed onto the surface of oxidic fibers. The physisorption of the compounds was confirmed by FTIR and QCM. Both systems showed sensitivity to the VOCs and they hold a broad promise particularly for sensing applications of volatile alcoholic compounds. The introduction of CeO2 into the ZnO structure reduced the sensitivity of ZnO most probably due to the decrement of oxygen vacancies. |
Acikgoz, Sabriye; Demir, Mustafa M; Yapasan, Ece; Kiraz, Alper; Unal, Ahmet A; Inci, Naci M: Investigation of the spontaneous emission rate of perylene dye molecules encapsulated into three-dimensional nanofibers via FLIM method. Applied Physics A, 116 (4), pp. 1867–1875, 2014, ISSN: 1432-0630. (Type: Journal Article | Abstract | Links | BibTeX) @article{acikgoz2014, title = {Investigation of the spontaneous emission rate of perylene dye molecules encapsulated into three-dimensional nanofibers via FLIM method}, author = {Sabriye Acikgoz and Mustafa M Demir and Ece Yapasan and Alper Kiraz and Ahmet A Unal and Naci M Inci}, url = {https://doi.org/10.1007/s00339-014-8346-y}, doi = {10.1007/s00339-014-8346-y}, issn = {1432-0630}, year = {2014}, date = {2014-09-01}, journal = {Applied Physics A}, volume = {116}, number = {4}, pages = {1867--1875}, abstract = {The decay dynamics of perylene dye molecules encapsulated in polymer nanofibers produced by electrospinning of polymethyl methacrylate are investigated using a confocal fluorescence lifetime imaging microscopy technique. Time-resolved experiments show that the fluorescence lifetime of perylene dye molecules is enhanced when the dye molecules are encapsulated in a three-dimensional photonic environment. It is hard to produce a sustainable host with exactly the same dimensions all the time during fabrication to accommodate dye molecules for enhancement of spontaneous emission rate. The electrospinning method allows us to have a control over fiber diameter. It is observed that the wavelength of monomer excitation of perylene dye molecules is too short to cause enhancement within nanofiber photonic environment of 330 nm diameters. However, when these nanofibers are doped with more concentrated perylene, in addition to monomer excitation, an excimer excitation is generated. This causes observation of the Purcell effect in the three-dimensional nanocylindrical photonic fiber geometry.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The decay dynamics of perylene dye molecules encapsulated in polymer nanofibers produced by electrospinning of polymethyl methacrylate are investigated using a confocal fluorescence lifetime imaging microscopy technique. Time-resolved experiments show that the fluorescence lifetime of perylene dye molecules is enhanced when the dye molecules are encapsulated in a three-dimensional photonic environment. It is hard to produce a sustainable host with exactly the same dimensions all the time during fabrication to accommodate dye molecules for enhancement of spontaneous emission rate. The electrospinning method allows us to have a control over fiber diameter. It is observed that the wavelength of monomer excitation of perylene dye molecules is too short to cause enhancement within nanofiber photonic environment of 330 nm diameters. However, when these nanofibers are doped with more concentrated perylene, in addition to monomer excitation, an excimer excitation is generated. This causes observation of the Purcell effect in the three-dimensional nanocylindrical photonic fiber geometry. |
Demir, Mustafa M; Baba, Alper; Atilla, Vedat; Inanli, Mustafa: Types of the scaling in hyper saline geothermal system in northwest Turkey. GEOTHERMICS, 50 , pp. 1-9, 2014. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000331482600001, title = {Types of the scaling in hyper saline geothermal system in northwest Turkey}, author = {Mustafa M Demir and Alper Baba and Vedat Atilla and Mustafa Inanli}, url = {https://www.sciencedirect.com/science/article/pii/S037565051300059X}, doi = {https://doi.org/10.1016/j.geothermics.2013.08.003}, year = {2014}, date = {2014-04-01}, journal = {GEOTHERMICS}, volume = {50}, pages = {1-9}, abstract = {Tuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. The geothermal brine from this area, which is dominated by NaCl, has a typical temperature of 173 degrees C. Rapid withdrawal of fluid to ambient surface conditions during sampling causes precipitation of various compounds known as scaling. Scaling is one of the important problems in Tuzla geothermal system that reduces the efficiency of the geothermal power plant and causes economical loss. The aim of this study was to determine the type of scaling as a first step towards preventing its formation. The scales formed in the geothermal system were divided into two groups according to location: the ones that formed in downhole and the ones that accumulated along the surface pipeline. Both scales were examined in terms of their elemental composition, structure and morphology using XRF, XRD, and SEM, respectively. The former was found to be mainly composed of PbS (Galena) and CaCO3 (aragonite or calcite). In contrast, the latter was heterogeneous in nature and consisted of mainly saponite like amorphous structure along with submicrometer-sized amorphous silica particles, layered double magnesium and iron hydroxide, and NaCl. (C) 2013 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Tuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. The geothermal brine from this area, which is dominated by NaCl, has a typical temperature of 173 degrees C. Rapid withdrawal of fluid to ambient surface conditions during sampling causes precipitation of various compounds known as scaling. Scaling is one of the important problems in Tuzla geothermal system that reduces the efficiency of the geothermal power plant and causes economical loss. The aim of this study was to determine the type of scaling as a first step towards preventing its formation. The scales formed in the geothermal system were divided into two groups according to location: the ones that formed in downhole and the ones that accumulated along the surface pipeline. Both scales were examined in terms of their elemental composition, structure and morphology using XRF, XRD, and SEM, respectively. The former was found to be mainly composed of PbS (Galena) and CaCO3 (aragonite or calcite). In contrast, the latter was heterogeneous in nature and consisted of mainly saponite like amorphous structure along with submicrometer-sized amorphous silica particles, layered double magnesium and iron hydroxide, and NaCl. (C) 2013 Elsevier Ltd. All rights reserved. |
Coutts, Michael J; Zareie, Hadi M; Cortie, Michael B; McDonagh, Andrew M: Charging of gold/metal oxide/gold nanocapacitors in a scanning electron microscope. Nanotechnology, 25 (15), pp. 155703, 2014. (Type: Journal Article | Abstract | Links | BibTeX) @article{coutts2014, title = {Charging of gold/metal oxide/gold nanocapacitors in a scanning electron microscope}, author = {Michael J Coutts and Hadi M Zareie and Michael B Cortie and Andrew M McDonagh}, url = {https://doi.org/10.1088%2F0957-4484%2F25%2F15%2F155703}, doi = {10.1088/0957-4484/25/15/155703}, year = {2014}, date = {2014-03-01}, journal = {Nanotechnology}, volume = {25}, number = {15}, pages = {155703}, publisher = {IOP Publishing}, abstract = {Triangular parallel-plate nanocapacitors were fabricated by a combination of microsphere lithography and physical vapor deposition. The devices were comprised of a 20 nm layer of dielectric material sandwiched between two 20 nm layers of gold. Dielectric materials with a range of relative permittivities were investigated. Charging of the capacitors was probed in a scanning electron microscope (SEM) by monitoring the change in brightness of the images of the devices as a function of time. The time constants, RC, associated with the charging of the capacitors, were extracted from the SEM grayscale data. The resulting average RC values were 248 ± 27 s for SiO2, 70 ± 8 s for Al2O3, 113 ± 80 s for ZnO and 125 ± 13 s for HfO2. These values are consistent with the anticipated RC values based on the resistivities and permittivities of the materials used in the devices and importantly, were measured without the need to attach any wires or leads.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Triangular parallel-plate nanocapacitors were fabricated by a combination of microsphere lithography and physical vapor deposition. The devices were comprised of a 20 nm layer of dielectric material sandwiched between two 20 nm layers of gold. Dielectric materials with a range of relative permittivities were investigated. Charging of the capacitors was probed in a scanning electron microscope (SEM) by monitoring the change in brightness of the images of the devices as a function of time. The time constants, RC, associated with the charging of the capacitors, were extracted from the SEM grayscale data. The resulting average RC values were 248 ± 27 s for SiO2, 70 ± 8 s for Al2O3, 113 ± 80 s for ZnO and 125 ± 13 s for HfO2. These values are consistent with the anticipated RC values based on the resistivities and permittivities of the materials used in the devices and importantly, were measured without the need to attach any wires or leads. |
Dikici, Tuncay; Guzelaydin, Abdurrahman Halis; Toparli, Mustafa: Formation and characterisation of nanoporous TiO2 layers on
microroughened titanium surfaces by electrochemical anodisation. MICRO & NANO LETTERS, 9 (2), pp. 144-148, 2014, ISSN: 1750-0443. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000333393900019, title = {Formation and characterisation of nanoporous TiO2 layers on microroughened titanium surfaces by electrochemical anodisation}, author = {Tuncay Dikici and Abdurrahman Halis Guzelaydin and Mustafa Toparli}, doi = {10.1049/mnl.2013.0719}, issn = {1750-0443}, year = {2014}, date = {2014-02-01}, journal = {MICRO & NANO LETTERS}, volume = {9}, number = {2}, pages = {144-148}, publisher = {INST ENGINEERING TECHNOLOGY-IET}, address = {MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND}, abstract = {Nanoporous titanium dioxide (TiO2) layers were successfully formed by an electrochemical anodisation method on microroughened titanium (Ti) surfaces in FLuoride containing aqueous electrolyte. Microroughened Ti surfaces were produced by sandblasting with Al2O3 particles of 50 m in diameter and acid-etching in a blend of HCl/H2SO4 solution. The surface morphology, topography and chemical composition of the specimens were analysed by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The surface roughness and the wettability of treated Ti surfaces were measured using profilometry and a contact angle measurement system, respectively. With anodising of sandblasted-/acid etched surfaces, micrometre- and nanometre-scale textures on titanium specimens were created. Results showed that these developed nanoporous-microroughened surfaces exhibited lower contact angle values than the other treated Ti surfaces. The sandblasted/acid-etched/anodised Ti specimen had a surface morphology with distinctively formed hills and valleys and higher surface roughness than the other anodised specimens. This study indicated that nanoporous TiO2 structures fabricated on microroughened Ti can be an effective way to modify the titanium surfaces for the future development of implant applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Nanoporous titanium dioxide (TiO2) layers were successfully formed by an electrochemical anodisation method on microroughened titanium (Ti) surfaces in FLuoride containing aqueous electrolyte. Microroughened Ti surfaces were produced by sandblasting with Al2O3 particles of 50 m in diameter and acid-etching in a blend of HCl/H2SO4 solution. The surface morphology, topography and chemical composition of the specimens were analysed by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The surface roughness and the wettability of treated Ti surfaces were measured using profilometry and a contact angle measurement system, respectively. With anodising of sandblasted-/acid etched surfaces, micrometre- and nanometre-scale textures on titanium specimens were created. Results showed that these developed nanoporous-microroughened surfaces exhibited lower contact angle values than the other treated Ti surfaces. The sandblasted/acid-etched/anodised Ti specimen had a surface morphology with distinctively formed hills and valleys and higher surface roughness than the other anodised specimens. This study indicated that nanoporous TiO2 structures fabricated on microroughened Ti can be an effective way to modify the titanium surfaces for the future development of implant applications. |
Demir, Mustafa M; Horzum, Nesrin; Taşdemirci, Alper; Turan, Kıvanç; Güden, Mustafa: Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix. ACS Applied Materials & Interfaces, 6 (24), pp. 21901-21905, 2014, (PMID: 25485762). (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/am507029c, title = {Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix}, author = {Mustafa M Demir and Nesrin Horzum and Alper Taşdemirci and Kıvanç Turan and Mustafa Güden}, url = {https://doi.org/10.1021/am507029c}, doi = {10.1021/am507029c}, year = {2014}, date = {2014-01-01}, journal = {ACS Applied Materials & Interfaces}, volume = {6}, number = {24}, pages = {21901-21905}, note = {PMID: 25485762}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sevinçli, Hâldun; Sevik, Cem: Electronic, phononic, and thermoelectric properties of graphyne sheets. Applied Physics Letters, 105 (22), pp. 223108, 2014. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/1.4902920, title = {Electronic, phononic, and thermoelectric properties of graphyne sheets}, author = {Hâldun Sevinçli and Cem Sevik}, url = {https://doi.org/10.1063/1.4902920}, doi = {10.1063/1.4902920}, year = {2014}, date = {2014-01-01}, journal = {Applied Physics Letters}, volume = {105}, number = {22}, pages = {223108}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Sevinçli, H; Brandbyge, M: Phonon scattering in graphene over substrate steps. Applied Physics Letters, 105 (15), pp. 153108, 2014. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/1.4898066, title = {Phonon scattering in graphene over substrate steps}, author = {H Sevinçli and M Brandbyge}, url = {https://doi.org/10.1063/1.4898066}, doi = {10.1063/1.4898066}, year = {2014}, date = {2014-01-01}, journal = {Applied Physics Letters}, volume = {105}, number = {15}, pages = {153108}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Nozaki, Daijiro; Avdoshenko, Stas M; Sevinçli, Hâldun; Cuniberti, Gianaurelio: Quantum interference in thermoelectric molecular junctions: A toy model perspective. Journal of Applied Physics, 116 (7), pp. 074308, 2014. (Type: Journal Article | Links | BibTeX) @article{doi:10.1063/1.4893475, title = {Quantum interference in thermoelectric molecular junctions: A toy model perspective}, author = {Daijiro Nozaki and Stas M Avdoshenko and Hâldun Sevinçli and Gianaurelio Cuniberti}, url = {https://doi.org/10.1063/1.4893475}, doi = {10.1063/1.4893475}, year = {2014}, date = {2014-01-01}, journal = {Journal of Applied Physics}, volume = {116}, number = {7}, pages = {074308}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Akdogan, Yasar; Wei, Wei; Huang, Kuo-Ying; Kageyama, Yoshiyuki; Danner, Eric W; Miller, Dusty R; Martinez Rodriguez, Nadine R; Waite, Herbert J; Han, Songi: Intrinsic Surface-Drying Properties of Bioadhesive Proteins. Angewandte Chemie International Edition, 53 (42), pp. 11253-11256, 2014. (Type: Journal Article | Abstract | Links | BibTeX) @article{doi:10.1002/anie.201406858, title = {Intrinsic Surface-Drying Properties of Bioadhesive Proteins}, author = {Yasar Akdogan and Wei Wei and Kuo-Ying Huang and Yoshiyuki Kageyama and Eric W Danner and Dusty R Miller and Nadine R Martinez Rodriguez and Herbert J Waite and Songi Han}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201406858}, doi = {10.1002/anie.201406858}, year = {2014}, date = {2014-01-01}, journal = {Angewandte Chemie International Edition}, volume = {53}, number = {42}, pages = {11253-11256}, abstract = {Abstract Sessile marine mussels must “dry” underwater surfaces before adhering to them. Synthetic adhesives have yet to overcome this fundamental challenge. Previous studies of bioinspired adhesion have largely been performed under applied compressive forces, but such studies are poor predictors of the ability of an adhesive to spontaneously penetrate surface hydration layers. In a force-free approach to measuring molecular-level interaction through surface-water diffusivity, different mussel foot proteins were found to have different abilities to evict hydration layers from surfaces—a necessary step for adsorption and adhesion. It was anticipated that DOPA would mediate dehydration owing to its efficacy in bioinspired wet adhesion. Instead, hydrophobic side chains were found to be a critical component for protein–surface intimacy. This direct measurement of interfacial water dynamics during force-free adsorptive interactions at solid surfaces offers guidance for the engineering of wet adhesives and coatings.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract Sessile marine mussels must “dry” underwater surfaces before adhering to them. Synthetic adhesives have yet to overcome this fundamental challenge. Previous studies of bioinspired adhesion have largely been performed under applied compressive forces, but such studies are poor predictors of the ability of an adhesive to spontaneously penetrate surface hydration layers. In a force-free approach to measuring molecular-level interaction through surface-water diffusivity, different mussel foot proteins were found to have different abilities to evict hydration layers from surfaces—a necessary step for adsorption and adhesion. It was anticipated that DOPA would mediate dehydration owing to its efficacy in bioinspired wet adhesion. Instead, hydrophobic side chains were found to be a critical component for protein–surface intimacy. This direct measurement of interfacial water dynamics during force-free adsorptive interactions at solid surfaces offers guidance for the engineering of wet adhesives and coatings. |
Barlas, F B; Seleci, Ag D; Ozkan, M; Demir, B; Seleci, M; Aydin, M; Tasdelen, M A; Zareie, H M; Timur, S; Ozcelik, S; Yagci, Y: Folic acid modified clay/polymer nanocomposites for selective cell adhesion. J. Mater. Chem. B, 2 , pp. 6412-6421, 2014. (Type: Journal Article | Abstract | Links | BibTeX) @article{C4TB00850B, title = {Folic acid modified clay/polymer nanocomposites for selective cell adhesion}, author = {F B Barlas and Ag D Seleci and M Ozkan and B Demir and M Seleci and M Aydin and M A Tasdelen and H M Zareie and S Timur and S Ozcelik and Y Yagci}, url = {http://dx.doi.org/10.1039/C4TB00850B}, doi = {10.1039/C4TB00850B}, year = {2014}, date = {2014-01-01}, journal = {J. Mater. Chem. B}, volume = {2}, pages = {6412-6421}, publisher = {The Royal Society of Chemistry}, abstract = {A folic acid (FA) modified poly(epsilon-caprolactone)/clay nanocomposite (PCL/MMT–(CH2CH2OH)2–FA) resulting in selective cell adhesion and proliferation was synthesized and characterized as a cell culture and biosensing platform. For this purpose, first the FA modified clay (MMT–(CH2CH2OH)2–FA) was prepared by treating the organo-modified clay, Cloisite 30B [MMT–(CH2CH2OH)2] with FA in chloroform at 60 °C. Subsequent ring opening polymerization of ε-caprolactone in the presence of tin octoate (Sn(Oct)2) using MMT–(CH2CH2OH)2–FA at 110 °C resulted in the formation of MMT–(CH2CH2OH)2–FA with an exfoliated clay structure. The structures of intermediates and the final nanocomposite were investigated in detail by FT-IR spectral analysis and DSC, TGA, XRD, SEM and AFM measurements. The combination of FA, PCL and clay provides a simple and versatile route to surfaces that allows controlled and selective cell adhesion and proliferation. FA receptor-positive HeLa and negative A549 cells were used to prove the selectivity of the modified surfaces. Both microscopy and electrochemical sensing techniques were applied to show the differences in cell adherence on the modified and pristine clay platforms. This approach is expected to be adapted into various bio-applications such as ‘cell culture on chip’, biosensors and design of tools for targeted diagnosis or therapy.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A folic acid (FA) modified poly(epsilon-caprolactone)/clay nanocomposite (PCL/MMT–(CH2CH2OH)2–FA) resulting in selective cell adhesion and proliferation was synthesized and characterized as a cell culture and biosensing platform. For this purpose, first the FA modified clay (MMT–(CH2CH2OH)2–FA) was prepared by treating the organo-modified clay, Cloisite 30B [MMT–(CH2CH2OH)2] with FA in chloroform at 60 °C. Subsequent ring opening polymerization of ε-caprolactone in the presence of tin octoate (Sn(Oct)2) using MMT–(CH2CH2OH)2–FA at 110 °C resulted in the formation of MMT–(CH2CH2OH)2–FA with an exfoliated clay structure. The structures of intermediates and the final nanocomposite were investigated in detail by FT-IR spectral analysis and DSC, TGA, XRD, SEM and AFM measurements. The combination of FA, PCL and clay provides a simple and versatile route to surfaces that allows controlled and selective cell adhesion and proliferation. FA receptor-positive HeLa and negative A549 cells were used to prove the selectivity of the modified surfaces. Both microscopy and electrochemical sensing techniques were applied to show the differences in cell adherence on the modified and pristine clay platforms. This approach is expected to be adapted into various bio-applications such as ‘cell culture on chip’, biosensors and design of tools for targeted diagnosis or therapy. |
2013 |
Sevinçli, H; Lehmann, T; Ryndyk, D A; Cuniberti, G: Comparison of electron and phonon transport in disordered semiconductor carbon nanotubes. Journal of Computational Electronics, 12 (4), pp. 685–691, 2013, ISSN: 1572-8137. (Type: Journal Article | Abstract | Links | BibTeX) @article{sevincli2013, title = {Comparison of electron and phonon transport in disordered semiconductor carbon nanotubes}, author = {H Sevinçli and T Lehmann and D A Ryndyk and G Cuniberti}, url = {https://doi.org/10.1007/s10825-013-0539-7}, doi = {10.1007/s10825-013-0539-7}, issn = {1572-8137}, year = {2013}, date = {2013-12-01}, journal = {Journal of Computational Electronics}, volume = {12}, number = {4}, pages = {685--691}, abstract = {Charge and thermal conductivities are the most important parameters of carbon nanomaterials as candidates for future electronics. In this paper we address the effects of Anderson type disorder in long semiconductor carbon nanotubes (CNTs) to electron charge conductivity and lattice thermal conductivity using the atomistic Green function approach. The electron and phonon transmissions are analyzed as a function of the length of the disordered nanostructures. The thermal conductance as a function of temperature is calculated for different lengths. Analysis of the transmission probabilities as a function of length of the disordered device shows that both electrons and phonons with different energies display different transport regimes, i.e. quasi-ballistic, diffusive and localization regimes coexist. In the light of the results we discuss heating of the semiconductor device in electronic applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Charge and thermal conductivities are the most important parameters of carbon nanomaterials as candidates for future electronics. In this paper we address the effects of Anderson type disorder in long semiconductor carbon nanotubes (CNTs) to electron charge conductivity and lattice thermal conductivity using the atomistic Green function approach. The electron and phonon transmissions are analyzed as a function of the length of the disordered nanostructures. The thermal conductance as a function of temperature is calculated for different lengths. Analysis of the transmission probabilities as a function of length of the disordered device shows that both electrons and phonons with different energies display different transport regimes, i.e. quasi-ballistic, diffusive and localization regimes coexist. In the light of the results we discuss heating of the semiconductor device in electronic applications. |
Demir, Mustafa M; Horzum, Nesrin; Özen, Bengisu; Özçelik, Serdar: Hierarchial Coassembly of a Cyanine Dye in Poly(vinyl alcohol) Fibrous Films by Electrospinning. JOURNAL OF PHYSICAL CHEMISTRY B, 117 (37), pp. 10920-10928, 2013, ISSN: 1520-6106. (Type: Journal Article | Links | BibTeX) @article{ISI:000329515200027, title = {Hierarchial Coassembly of a Cyanine Dye in Poly(vinyl alcohol) Fibrous Films by Electrospinning}, author = {Mustafa M Demir and Nesrin Horzum and Bengisu Özen and Serdar Özçelik}, url = {https://pubs.acs.org/doi/10.1021/jp404977d}, doi = {10.1021/jp404977d}, issn = {1520-6106}, year = {2013}, date = {2013-09-01}, journal = {JOURNAL OF PHYSICAL CHEMISTRY B}, volume = {117}, number = {37}, pages = {10920-10928}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Tunusoğlu, Özge; Demir, Mustafa M: Tailored CeO2 Nanoparticles Surface in Free Radical Bulk Polymerization of Methyl Methacrylate. Industrial & Engineering Chemistry Research, 52 (37), pp. 13401-13410, 2013. (Type: Journal Article | Links | BibTeX) @article{doi:10.1021/ie401872y, title = {Tailored CeO2 Nanoparticles Surface in Free Radical Bulk Polymerization of Methyl Methacrylate}, author = {Özge Tunusoğlu and Mustafa M Demir}, url = {https://doi.org/10.1021/ie401872y}, doi = {10.1021/ie401872y}, year = {2013}, date = {2013-01-01}, journal = {Industrial & Engineering Chemistry Research}, volume = {52}, number = {37}, pages = {13401-13410}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Boyaci, Ezel; Horzum, Nesrin; Cagir, Ali; Demir, Mustafa M; Eroglu, Ahmet E: Electrospun amino-functionalized PDMS as a novel SPME sorbent for the speciation of inorganic and organometallic arsenic species. RSC ADVANCES, 3 (44), pp. 22261-22268, 2013. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000326056600157, title = {Electrospun amino-functionalized PDMS as a novel SPME sorbent for the speciation of inorganic and organometallic arsenic species}, author = {Ezel Boyaci and Nesrin Horzum and Ali Cagir and Mustafa M Demir and Ahmet E Eroglu}, url = {https://pubs.rsc.org/en/content/articlehtml/2013/ra/c3ra43622e}, doi = {10.1039/C3RA43622E}, year = {2013}, date = {2013-01-01}, journal = {RSC ADVANCES}, volume = {3}, number = {44}, pages = {22261-22268}, abstract = {Sol-gel based amine-functionalized SPME fibers (PDMS-weak anion exchanger) were prepared and used for direct mode extraction of dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)) from aqueous solutions followed by HPLC-ICPMS determination. Two different methods of coating were employed: (i) electrospinning and (ii) dip coating. Electrospinning was used for the first time for preparation of sol-gel based SPME fibers and was found to be superior in terms of extracted amount of arsenicals, coating homogeneity, accessibility of amine groups on the surface, and preparation time for a single fiber. Various parameters such as solution pH, extraction time, agitation speed, extraction temperature, and ionic strength were studied. Optimum extraction conditions were determined as pH of 5.0, extraction time of 30 min, agitation speed of 700 rpm, and extraction temperature of 20 degrees C. Extraction ability of the novel coating decreased by the addition of NaCl as a consequence of the competition between anionic arsenic species and chloride ions for active sites of the weak anion exchanger. This novel sol-gel coating prepared by electrospinning was found to be promising for SPME applications. Vibrational spectroscopy revealed the alignment of PDMS chains by elongational force under electrospinning process. The chain alignment accordingly orients the pendant amino functional groups perpendicular to the fiber surface, which may develop the free active functional groups available to the medium and lead to the enhancement of the extraction performance. Moreover, the proposed coating strategy through electrospinning might be able to break new ground for various applications in analytical chemistry as well as other disciplines.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Sol-gel based amine-functionalized SPME fibers (PDMS-weak anion exchanger) were prepared and used for direct mode extraction of dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)) from aqueous solutions followed by HPLC-ICPMS determination. Two different methods of coating were employed: (i) electrospinning and (ii) dip coating. Electrospinning was used for the first time for preparation of sol-gel based SPME fibers and was found to be superior in terms of extracted amount of arsenicals, coating homogeneity, accessibility of amine groups on the surface, and preparation time for a single fiber. Various parameters such as solution pH, extraction time, agitation speed, extraction temperature, and ionic strength were studied. Optimum extraction conditions were determined as pH of 5.0, extraction time of 30 min, agitation speed of 700 rpm, and extraction temperature of 20 degrees C. Extraction ability of the novel coating decreased by the addition of NaCl as a consequence of the competition between anionic arsenic species and chloride ions for active sites of the weak anion exchanger. This novel sol-gel coating prepared by electrospinning was found to be promising for SPME applications. Vibrational spectroscopy revealed the alignment of PDMS chains by elongational force under electrospinning process. The chain alignment accordingly orients the pendant amino functional groups perpendicular to the fiber surface, which may develop the free active functional groups available to the medium and lead to the enhancement of the extraction performance. Moreover, the proposed coating strategy through electrospinning might be able to break new ground for various applications in analytical chemistry as well as other disciplines. |
Horzum, Nesrin; Demir, Mustafa M; Nairat, Muath; Shahwan, Talal: Chitosan fiber-supported zero-valent iron nanoparticles as a novel sorbent for sequestration of inorganic arsenic. RSC ADVANCES, 3 (21), pp. 7828-7837, 2013. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000318634000029, title = {Chitosan fiber-supported zero-valent iron nanoparticles as a novel sorbent for sequestration of inorganic arsenic}, author = {Nesrin Horzum and Mustafa M Demir and Muath Nairat and Talal Shahwan}, url = {https://pubs.rsc.org/en/content/articlehtml/2013/ra/c3ra23454a}, doi = {10.1039/C3RA23454A}, year = {2013}, date = {2013-01-01}, journal = {RSC ADVANCES}, volume = {3}, number = {21}, pages = {7828-7837}, abstract = {This study proposes a new sorbent for the removal of inorganic arsenic from aqueous solutions. Monodispersed nano zero-valent iron (nZVI) particles were nucleated at the surface of electrospun chitosan fibers (average fiber diameter of 195 +/- 50 nm) by liquid phase reduction of FeCl3 using NaBH4. The material was characterized using SEM, TGA, XPS, XRD, and FTIR. The diameter of iron nanoparticles was found to vary between 75-100 nm. A set of batch experiments were carried out to elucidate the efficiency of the composite sorbent toward fixation of arsenite and arsenate ions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the chitosan fiber supported nZVI particles is an excellent sorbent material for inorganic arsenic uptake at concentrations ranging from 0.01 to 5.00 mg L-1 over a wide range of pH values. Based on XPS analysis, As(III) was found to undergo oxidation to As(V) upon sorption, while As(V) retained its oxidation state. By virtue of the successful combination of the electrospun fibers' mechanical integrity and the large reactivity of dispersed nZVI particles, the applicability of the resulting sorbent material in arsenic sorption holds broad promise.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study proposes a new sorbent for the removal of inorganic arsenic from aqueous solutions. Monodispersed nano zero-valent iron (nZVI) particles were nucleated at the surface of electrospun chitosan fibers (average fiber diameter of 195 +/- 50 nm) by liquid phase reduction of FeCl3 using NaBH4. The material was characterized using SEM, TGA, XPS, XRD, and FTIR. The diameter of iron nanoparticles was found to vary between 75-100 nm. A set of batch experiments were carried out to elucidate the efficiency of the composite sorbent toward fixation of arsenite and arsenate ions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the chitosan fiber supported nZVI particles is an excellent sorbent material for inorganic arsenic uptake at concentrations ranging from 0.01 to 5.00 mg L-1 over a wide range of pH values. Based on XPS analysis, As(III) was found to undergo oxidation to As(V) upon sorption, while As(V) retained its oxidation state. By virtue of the successful combination of the electrospun fibers' mechanical integrity and the large reactivity of dispersed nZVI particles, the applicability of the resulting sorbent material in arsenic sorption holds broad promise. |
Attila, Yiğit; Güden, Mustafa; Taşdemirci, Alper: Foam glass processing using a polishing glass powder residue. Ceramics International, 39 (5), pp. 5869 - 5877, 2013, ISSN: 0272-8842. (Type: Journal Article | Abstract | Links | BibTeX) @article{attila20135869, title = {Foam glass processing using a polishing glass powder residue}, author = {Yiğit Attila and Mustafa Güden and Alper Taşdemirci}, url = {http://www.sciencedirect.com/science/article/pii/S0272884213000242}, doi = {https://doi.org/10.1016/j.ceramint.2012.12.104}, issn = {0272-8842}, year = {2013}, date = {2013-01-01}, journal = {Ceramics International}, volume = {39}, number = {5}, pages = {5869 - 5877}, abstract = {The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950°C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680°C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378gcm−3, respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between ∼1 and 4MPa and the thermal conductivity between 0.048 and 0.079WK−1m−1. Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950°C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680°C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378gcm−3, respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between ∼1 and 4MPa and the thermal conductivity between 0.048 and 0.079WK−1m−1. Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges. |
Colpankan, O; Yildiz, S; Tanoglu, M: Silica Based Shear Thickening Fluids (STFs) and Their Composites. 9TH INTERNATIONAL CONFERENCE ON COMPOSITE SCIENCE AND TECHNOLOGY: 2020 -
SCIENTIFIC AND INDUSTRIAL CHALLENGES, pp. 993+, Boeing, Italy; Boeing, USA DESTECH PUBLICATIONS, INC, 439 DUKE STREET, LANCASTER, PA 17602-4967 USA, 2013, ISBN: 978-1-60595-113-3, (9th International Conference on Composite Science and Technology (ICCST)
- 2020-Scientific and Industrial Challenges, Naples, ITALY, APR 24-26,
2013). (Type: Inproceedings | Links | BibTeX) @inproceedings{ISI:000329403000101, title = {Silica Based Shear Thickening Fluids (STFs) and Their Composites}, author = {O Colpankan and S Yildiz and M Tanoglu}, url = {http://www.dpi-proceedings.com/index.php/ICCST9/article/viewFile/244/245}, isbn = {978-1-60595-113-3}, year = {2013}, date = {2013-01-01}, booktitle = {9TH INTERNATIONAL CONFERENCE ON COMPOSITE SCIENCE AND TECHNOLOGY: 2020 - SCIENTIFIC AND INDUSTRIAL CHALLENGES}, pages = {993+}, publisher = {DESTECH PUBLICATIONS, INC}, address = {439 DUKE STREET, LANCASTER, PA 17602-4967 USA}, organization = {Boeing, Italy; Boeing, USA}, note = {9th International Conference on Composite Science and Technology (ICCST) - 2020-Scientific and Industrial Challenges, Naples, ITALY, APR 24-26, 2013}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } |
Kesici, Kutsal; Tuney, Inci; Zeren, Dogus; Guden, Mustafa; Sukatar, Atakan: Morphological and molecular identification of pennate diatoms isolated
from Urla, Izmir, coast of the Aegean Sea. TURKISH JOURNAL OF BIOLOGY, 37 (5), pp. 530-537, 2013, ISSN: 1300-0152. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000325300500004, title = {Morphological and molecular identification of pennate diatoms isolated from Urla, Izmir, coast of the Aegean Sea}, author = {Kutsal Kesici and Inci Tuney and Dogus Zeren and Mustafa Guden and Atakan Sukatar}, doi = {10.3906/biy-1205-40}, issn = {1300-0152}, year = {2013}, date = {2013-01-01}, journal = {TURKISH JOURNAL OF BIOLOGY}, volume = {37}, number = {5}, pages = {530-537}, publisher = {TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY}, address = {ATATURK BULVARI NO 221, KAVAKLIDERE, ANKARA, 00000, TURKEY}, abstract = {Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms. |
Parlak, Onur; Demir, Mustafa M: Anomalous transmittance of polystyrene-ceria nanocomposites at high
particle loadings. JOURNAL OF MATERIALS CHEMISTRY C, 1 (2), pp. 290-298, 2013, ISSN: 2050-7526. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000314801200017, title = {Anomalous transmittance of polystyrene-ceria nanocomposites at high particle loadings}, author = {Onur Parlak and Mustafa M Demir}, doi = {10.1039/c2tc00084a}, issn = {2050-7526}, year = {2013}, date = {2013-01-01}, journal = {JOURNAL OF MATERIALS CHEMISTRY C}, volume = {1}, number = {2}, pages = {290-298}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {Optical nanocomposites based on transparent polymers and nanosized pigment particles have usually been produced at low particle concentrations due to the undesirable optical scattering of the pigment particles. However, the contribution of the particles to many physical properties is realized at high concentrations. In this study, nanocomposites were prepared with transparent polystyrene (PS) and organophilic CeO2 nanoparticles using various compositions in which the particle content was up to 95 wt%. The particles, capped by 3-methacryloxypropyltrimethoxysilane (MPS), were dispersed into PS and the transmittance of the spin-coated composite films was examined over the UV-visible region. When the particle concentration was <20 wt%, the transmittance of the films showed a first-order exponential decay as the Rayleigh scattering theory proposes. However, a positive deviation was observed from the decay function for higher particle contents. The improvement in transmittance may be a consequence of interference in the multiple scattering of light by the quasi-ordered internal microstructure that gradually develops as the particle concentration increases.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Optical nanocomposites based on transparent polymers and nanosized pigment particles have usually been produced at low particle concentrations due to the undesirable optical scattering of the pigment particles. However, the contribution of the particles to many physical properties is realized at high concentrations. In this study, nanocomposites were prepared with transparent polystyrene (PS) and organophilic CeO2 nanoparticles using various compositions in which the particle content was up to 95 wt%. The particles, capped by 3-methacryloxypropyltrimethoxysilane (MPS), were dispersed into PS and the transmittance of the spin-coated composite films was examined over the UV-visible region. When the particle concentration was <20 wt%, the transmittance of the films showed a first-order exponential decay as the Rayleigh scattering theory proposes. However, a positive deviation was observed from the decay function for higher particle contents. The improvement in transmittance may be a consequence of interference in the multiple scattering of light by the quasi-ordered internal microstructure that gradually develops as the particle concentration increases. |
2012 |
Savaci, Umut; Yilmaz, Sinan; Guden, Mustafa: Open cell lead foams: processing, microstructure, and mechanical
properties. JOURNAL OF MATERIALS SCIENCE, 47 (15), pp. 5646-5654, 2012, ISSN: 0022-2461. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000304110400004, title = {Open cell lead foams: processing, microstructure, and mechanical properties}, author = {Umut Savaci and Sinan Yilmaz and Mustafa Guden}, doi = {10.1007/s10853-012-6496-x}, issn = {0022-2461}, year = {2012}, date = {2012-08-01}, journal = {JOURNAL OF MATERIALS SCIENCE}, volume = {47}, number = {15}, pages = {5646-5654}, publisher = {SPRINGER}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {Open cell lead foams with the porosities between 48 and 74 % were prepared by means of powder metallurgical and casting routes, using ammonium bicarbonate particles, silica beads, and sodium chloride salt particles as space holder. The resulting foam samples structure closely resembled open cell foam structure: each cell had few interconnections with neighboring cells. Small-sized lead (II) fluoride precipitates were microscopically observed in the interior of cells in the foam samples prepared using silica beads as space holder, resulting from the reaction between silica and hydrofluoric acid in the space holder dissolution step. The compression stress-strain curve of foam samples prepared by powder metallurgical route showed brittle deformation behavior following the initial elastic deformation region, while the foam samples prepared by casting route showed characteristic foam deformation behavior: cell edge crushing on the bent cell walls, and cell wall tearing. The collapse stresses, densification strains, and elastic moduli of the prepared foams were further fitted with scaling relations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Open cell lead foams with the porosities between 48 and 74 % were prepared by means of powder metallurgical and casting routes, using ammonium bicarbonate particles, silica beads, and sodium chloride salt particles as space holder. The resulting foam samples structure closely resembled open cell foam structure: each cell had few interconnections with neighboring cells. Small-sized lead (II) fluoride precipitates were microscopically observed in the interior of cells in the foam samples prepared using silica beads as space holder, resulting from the reaction between silica and hydrofluoric acid in the space holder dissolution step. The compression stress-strain curve of foam samples prepared by powder metallurgical route showed brittle deformation behavior following the initial elastic deformation region, while the foam samples prepared by casting route showed characteristic foam deformation behavior: cell edge crushing on the bent cell walls, and cell wall tearing. The collapse stresses, densification strains, and elastic moduli of the prepared foams were further fitted with scaling relations. |
2008 |
Ince, Umut; Toksoy, Macit; Guden, Mustafa: Testing corrosion rates on steel piping in geothermal district heating. MATERIALS PERFORMANCE, 47 (5), pp. 56-59, 2008, ISSN: 0094-1492. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000255758800018, title = {Testing corrosion rates on steel piping in geothermal district heating}, author = {Umut Ince and Macit Toksoy and Mustafa Guden}, url = {http://openaccess.iyte.edu.tr/handle/11147/4352}, issn = {0094-1492}, year = {2008}, date = {2008-05-01}, journal = {MATERIALS PERFORMANCE}, volume = {47}, number = {5}, pages = {56-59}, publisher = {NATL ASSOC CORROSION ENG}, address = {1440 SOUTH CREEK DRIVE, HOUSTON, TX 77084-4906 USA}, abstract = {The St-37 carbon steel piping in a geothermal heating system experienced increasing corrosion leaks. Tests with pipe steel coupons showed that while uniform corrosion rates were low, pitting rates were high. Sulfate-reducing bacteria were the main cause. Changes in fluid velocities and the addition of a bacteriacide were recommended.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The St-37 carbon steel piping in a geothermal heating system experienced increasing corrosion leaks. Tests with pipe steel coupons showed that while uniform corrosion rates were low, pitting rates were high. Sulfate-reducing bacteria were the main cause. Changes in fluid velocities and the addition of a bacteriacide were recommended. |
2005 |
Altinkaya, SA; Yenal, H; Ozbas, B: Membrane formation by dry-cast process model validation through
morphological studies. JOURNAL OF MEMBRANE SCIENCE, 249 (1-2), pp. 163-172, 2005, ISSN: 0376-7388. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000227187900018, title = {Membrane formation by dry-cast process model validation through morphological studies}, author = {SA Altinkaya and H Yenal and B Ozbas}, doi = {10.1016/j.memsci.2004.10.008}, issn = {0376-7388}, year = {2005}, date = {2005-03-01}, journal = {JOURNAL OF MEMBRANE SCIENCE}, volume = {249}, number = {1-2}, pages = {163-172}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {Asymmetric membranes were prepared by dry-cast phase inversion technique from a cellulose acetate, acetone, water solution in order to assess the validity of the mathematical model recently developed by us. Based on the model predictions, general structural characteristics of the membranes were determined by plotting the composition paths on the ternary phase diagram and polymer concentration profile at the first moment of precipitation. Composition paths on the ternary phase diagram enable the assessment of whether a phase separation occurs and allow prediction of inception time and duration of the phase separation. The polymer distribution at the moment of precipitation provides a rough thickness of the high polymer concentration region near the interface and a pore distribution of the sublayer structure. The effects of polymer/nonsolvent ratio in the casting solution, the initial film thickness, evaporation temperature, relative humidity and velocity of air were investigated. Model predictions were compared with the morphological analysis conducted using scanning electron microscopy. Results show that diffusion formulation plays an important role in capturing the accurate structure of the membrane from the model predictions. (C) 2004 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Asymmetric membranes were prepared by dry-cast phase inversion technique from a cellulose acetate, acetone, water solution in order to assess the validity of the mathematical model recently developed by us. Based on the model predictions, general structural characteristics of the membranes were determined by plotting the composition paths on the ternary phase diagram and polymer concentration profile at the first moment of precipitation. Composition paths on the ternary phase diagram enable the assessment of whether a phase separation occurs and allow prediction of inception time and duration of the phase separation. The polymer distribution at the moment of precipitation provides a rough thickness of the high polymer concentration region near the interface and a pore distribution of the sublayer structure. The effects of polymer/nonsolvent ratio in the casting solution, the initial film thickness, evaporation temperature, relative humidity and velocity of air were investigated. Model predictions were compared with the morphological analysis conducted using scanning electron microscopy. Results show that diffusion formulation plays an important role in capturing the accurate structure of the membrane from the model predictions. (C) 2004 Elsevier B.V. All rights reserved. |
2004 |
Altinkaya, SA; Ozbas, B: Modeling of asymmetric membrane formation by dry-casting method. JOURNAL OF MEMBRANE SCIENCE, 230 (1-2), pp. 71-89, 2004, ISSN: 0376-7388. (Type: Journal Article | Abstract | Links | BibTeX) @article{ISI:000189087000008, title = {Modeling of asymmetric membrane formation by dry-casting method}, author = {SA Altinkaya and B Ozbas}, doi = {10.1016/j.memsci.2003.10.034}, issn = {0376-7388}, year = {2004}, date = {2004-02-01}, journal = {JOURNAL OF MEMBRANE SCIENCE}, volume = {230}, number = {1-2}, pages = {71-89}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {Many polymeric membranes are produced by phase inversion technique invented by Loeb and Sourirajan in 1962. The dry-casting method is one of the major phase inversion techniques in which a homogeneous polymer solution consisting of solvent(s) and nonsolvent(s) is cast on a support and then evaporation of the casting solution takes place under convective conditions. In this paper, we model membrane formation by the dry-casting method. The model takes into account film shrinkage, evaporative cooling, coupled heat, and mass transfer and incorporates practical and reliable diffusion theory as well as complex boundary conditions especially at the polymer solution/air interface. The predictions from the model provide composition paths, temperature, and thickness of the solution. By plotting the composition paths on the ternary phase diagram, we ascertain the general structural characteristics of the membranes prepared from particular casting conditions. The predictive ability of the model was evaluated by comparing the results with the experimental data obtained from gravimetric measurements for cellulose acetate (CA)-acetone-water system. In an attempt to illustrate the importance of diffusion formalism on the predictions, recently proposed multicomponent diffusion theory and its simplified forms were utilized in the model. The computational results show that the critical factor for capturing the accurate behavior of membrane formation is the diffusion formalism utilized in the model. (C) 2003 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Many polymeric membranes are produced by phase inversion technique invented by Loeb and Sourirajan in 1962. The dry-casting method is one of the major phase inversion techniques in which a homogeneous polymer solution consisting of solvent(s) and nonsolvent(s) is cast on a support and then evaporation of the casting solution takes place under convective conditions. In this paper, we model membrane formation by the dry-casting method. The model takes into account film shrinkage, evaporative cooling, coupled heat, and mass transfer and incorporates practical and reliable diffusion theory as well as complex boundary conditions especially at the polymer solution/air interface. The predictions from the model provide composition paths, temperature, and thickness of the solution. By plotting the composition paths on the ternary phase diagram, we ascertain the general structural characteristics of the membranes prepared from particular casting conditions. The predictive ability of the model was evaluated by comparing the results with the experimental data obtained from gravimetric measurements for cellulose acetate (CA)-acetone-water system. In an attempt to illustrate the importance of diffusion formalism on the predictions, recently proposed multicomponent diffusion theory and its simplified forms were utilized in the model. The computational results show that the critical factor for capturing the accurate behavior of membrane formation is the diffusion formalism utilized in the model. (C) 2003 Elsevier B.V. All rights reserved. |
0000 |
Kandemir, Ayse Cagil; Donmez, Fatma; Davut, Kemal; Can, Hatice Kaplan: Design and fabrication of polymer micro/nano composites with two-level
mechanical reinforcing procedure. POLYMER COMPOSITES, 0000, ISSN: 0272-8397. (Type: Journal Article | Abstract | Links | BibTeX) @article{WOS:000791768700001, title = {Design and fabrication of polymer micro/nano composites with two-level mechanical reinforcing procedure}, author = {Ayse Cagil Kandemir and Fatma Donmez and Kemal Davut and Hatice Kaplan Can}, doi = {10.1002/pc.26717}, issn = {0272-8397}, journal = {POLYMER COMPOSITES}, publisher = {WILEY}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {Biocompatible composite production was accomplished by utilizing two-level hierarchical approach for mechanical reinforcement. A well-known commodity polymer; low-density polyethylene (LDPE), which has high-fracture toughness, yet low strength and modulus was used as the main matrix material. As the first step of hierarchy, ductile LDPE was blended with brittle polyvinylpyrrolidone (PVP), which is an eco-friendly, nontoxic and biocompatible polymer. This resulted in slight decrease of strength and drastic reduction of toughness (%70), yet modulus was increased by 78%. As the second level of hierarchy, PVP composites were introduced in LDPE. Nano-scaled Halloysite clay and micro-scaled spherical Silica particles were utilized as additives in the aforementioned PVP composites. The reason for the choice of these particles is that they are nontoxic, low-cost and in the case of Halloysite; abundant in nature. Owing to the implementation of the second level; modulus improvement was further enhanced to 150%, with additional benefits of strength increase up to 17% and less reduction in fracture toughness (minimum 51% reduction). Dynamic mechanical analysis also supported these outcomes that storage modulus of composites are higher than both LDPE and LDPE-PVP blend. The proposed biocompatible composites in the end of this study would be utilized in biomedical applications necessitating mechanical improvements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Biocompatible composite production was accomplished by utilizing two-level hierarchical approach for mechanical reinforcement. A well-known commodity polymer; low-density polyethylene (LDPE), which has high-fracture toughness, yet low strength and modulus was used as the main matrix material. As the first step of hierarchy, ductile LDPE was blended with brittle polyvinylpyrrolidone (PVP), which is an eco-friendly, nontoxic and biocompatible polymer. This resulted in slight decrease of strength and drastic reduction of toughness (%70), yet modulus was increased by 78%. As the second level of hierarchy, PVP composites were introduced in LDPE. Nano-scaled Halloysite clay and micro-scaled spherical Silica particles were utilized as additives in the aforementioned PVP composites. The reason for the choice of these particles is that they are nontoxic, low-cost and in the case of Halloysite; abundant in nature. Owing to the implementation of the second level; modulus improvement was further enhanced to 150%, with additional benefits of strength increase up to 17% and less reduction in fracture toughness (minimum 51% reduction). Dynamic mechanical analysis also supported these outcomes that storage modulus of composites are higher than both LDPE and LDPE-PVP blend. The proposed biocompatible composites in the end of this study would be utilized in biomedical applications necessitating mechanical improvements. |
Erisir, Ersoy; Bilir, Oguz Gurkan; Sozer, Yunus Emre; Ararat, Ozge; Davut, Kemal: Partial austenitisation and TBF steel composed of ferrite, bainitic
ferrite, and austenite. MATERIALS SCIENCE AND TECHNOLOGY, 0000, ISSN: 0267-0836. (Type: Journal Article | Abstract | Links | BibTeX) @article{WOS:000829862200001, title = {Partial austenitisation and TBF steel composed of ferrite, bainitic ferrite, and austenite}, author = {Ersoy Erisir and Oguz Gurkan Bilir and Yunus Emre Sozer and Ozge Ararat and Kemal Davut}, doi = {10.1080/02670836.2022.2102289}, issn = {0267-0836}, journal = {MATERIALS SCIENCE AND TECHNOLOGY}, publisher = {TAYLOR & FRANCIS LTD}, address = {2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND}, abstract = {A TRIP-aided bainitic-ferritic (TBF) steel with a chemical composition of Fe-0.19C-1.7Mn-1.09Si-0.51Al-0.05Nb (wt-%) was partially austenitised from a hot-rolled martensitic initial microstructure. After the hot rolling, the martensitic specimens were reheated to different intercritical temperatures and then austempered at 350 degrees C. Thus, the effect of the initial microstructure of TBF steel on intercritical austenite formation during partial austenitisation was studied. The microstructures were investigated by scanning electron microscopy and electron backscatter diffraction (EBSD), and the tensile properties were tested. Microstructural observations revealed that a final microstructure of fine ferrite, bainitic ferrite, and retained austenite can be obtained. The steel partial austenitised at 770 degrees C showed a good combination of ultimate tensile strength and total elongation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A TRIP-aided bainitic-ferritic (TBF) steel with a chemical composition of Fe-0.19C-1.7Mn-1.09Si-0.51Al-0.05Nb (wt-%) was partially austenitised from a hot-rolled martensitic initial microstructure. After the hot rolling, the martensitic specimens were reheated to different intercritical temperatures and then austempered at 350 degrees C. Thus, the effect of the initial microstructure of TBF steel on intercritical austenite formation during partial austenitisation was studied. The microstructures were investigated by scanning electron microscopy and electron backscatter diffraction (EBSD), and the tensile properties were tested. Microstructural observations revealed that a final microstructure of fine ferrite, bainitic ferrite, and retained austenite can be obtained. The steel partial austenitised at 770 degrees C showed a good combination of ultimate tensile strength and total elongation. |