Materials Science and Engineering
2019 |
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 Article Journal of Physics: Condensed Matter, 31 (27), pp. 273003, 2019. @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 Journal Article Opt. Lett., 44 (3), pp. 479–482, 2019. @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 The Journal of Physical Chemistry C, 123 (14), pp. 9343-9351, 2019. @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 Journal Article Applied Surface Science, 467-468 , pp. 648 - 657, 2019, ISSN: 0169-4332. @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 Journal Article Geothermics, 77 , pp. 106 - 114, 2019, ISSN: 0375-6505. @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 Journal Article Dyes and Pigments, 160 , pp. 501 - 508, 2019, ISSN: 0143-7208. @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 Article Journal of Alloys and Compounds, 791 , pp. 674 - 680, 2019, ISSN: 0925-8388. @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. |
Kandemir, A; Iyikanat, F; Sahin, H Monitoring the crystal orientation of black-arsenic via vibrational spectra Journal Article J. Mater. Chem. C, 7 , pp. 1228-1236, 2019. @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 Article Journal of Biomimetics, Biomaterials and Biomedical Engineering, 41 , pp. 69–81, 2019. @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 Journal Article Chemical Engineering Research and Design, 141 , pp. 317 - 327, 2019, ISSN: 0263-8762. @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. |
Olcer, Yekta Arya; Tascon, Marcos; Eroglu, Ahmet E; Boyacı, Ezel Thin film microextraction: Towards faster and more sensitive microextraction Journal Article TrAC Trends in Analytical Chemistry, 113 , pp. 93 - 101, 2019, ISSN: 0165-9936. @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 Journal Article The Journal of Physical Chemistry C, 123 (7), pp. 4549-4557, 2019. @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} } |
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 Journal Article Materials Research Express, 5 (10), pp. 105305, 2018. @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 Journal Article Phys. Rev. Materials, 2 , pp. 073406, 2018. @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) During 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 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 As 3 the reaction barrier is reduced considerably along the bond angles being commensurate with the kinked geometry of hydrogenated graphene at the substrate edge. a result and This which has the potential to overcome substrate or rippling effects 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 Journal Article Phys. Rev. B, 98 , pp. 045431, 2018. @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 Journal Article Semiconductor Science and Technology, 33 (8), pp. 085002, 2018. @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 Journal Article Fibers and Polymers, 19 (4), pp. 767–774, 2018, ISSN: 1875-0052. @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 Journal Article Phys. Rev. B, 97 , pp. 155410, 2018. @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 Journal Article Phys. Rev. Materials, 2 , pp. 034601, 2018. @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 Journal Article Materials Research Express, 5 (3), pp. 036415, 2018. @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 Journal Article Nanotechnology, 29 (13), pp. 135202, 2018. @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 Journal Article MATERIALS & DESIGN, 140 , pp. 37-44, 2018. @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. |
Guner, Tugrul; Demir, Mustafa M A Review on Halide Perovskites as Color Conversion Layers in White Light Emitting Diode Applications Journal Article physica status solidi (a), 215 (13), pp. 1800120, 2018. @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. |
Demirkurt, M; Olcer, Y A; Demir, M M; Eroglu, A E Electrospun polystyrene fibers knitted around imprinted acrylate microspheres as sorbent for paraben derivatives Journal Article Analytica Chimica Acta, 1014 , pp. 1 - 9, 2018, ISSN: 0003-2670. @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. |
Sandonas, Leonardo Medrano; Sevinçli, Hâldun; Gutierrez, Rafael; Cuniberti, Gianaurelio First-Principle-Based Phonon Transport Properties of Nanoscale Graphene Grain Boundaries Journal Article Advanced Science, 5 (2), pp. 1700365, 2018. @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. |
Demirkurt, Begüm; Akdogan, Yasar Development of an Ionic Liquid Based Method for the Preparation of Albumin Nanoparticles Journal Article ChemistrySelect, 3 (34), pp. 9940-9945, 2018. @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. |
Kandemir, A; Sahin, H Bilayers of Janus WSSe: monitoring the stacking type via the vibrational spectrum Journal Article Phys. Chem. Chem. Phys., 20 , pp. 17380-17386, 2018. @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. |
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 Journal Article Chemistry – A European Journal, 24 (13), pp. 3136-3140, 2018. @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. |
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 Journal Article Applied Surface Science, 428 , pp. 1010 - 1017, 2018, ISSN: 0169-4332. @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 Article Journal of Chemical Theory and Computation, 14 (1), pp. 225-235, 2018, (PMID: 29206461). @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} } |
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 Journal Article ACS Applied Nano Materials, 1 (8), pp. 4306-4316, 2018. @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} } |
Isık, Tuğba; Demir, Mustafa M Tailored electrospun fibers from waste polystyrene for high oil adsorption Journal Article Sustainable Materials and Technologies, 18 , pp. e00084, 2018, ISSN: 2214-9937. @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; 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 Journal Article The Journal of Physical Chemistry C, 122 (21), pp. 11543-11549, 2018. @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 Journal Article Photonics and Nanostructures - Fundamentals and Applications, 29 , pp. 22 - 29, 2018, ISSN: 1569-4410. @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. |
Çelik, Aslı; Topçu, Gökhan; Isik, Tuğba; Baba, Alper; Horzum, Nesrin; Demir, Mustafa M Applied Electromagnetic Engineering for Advanced Materials from Macro-to Nanoscale under Static-to Shock Loading, pp. 121–126, Trans Tech Publications, 2018. @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. |