WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 61Citation - Scopus: 64Electrospun Gelma Fibers and P(hema) Matrix Composite for Corneal Tissue Engineering(Elsevier Ltd., 2021) Arıca, Tuğçe A.; Güzelgülgen, Meltem; Yıldız, Ahu Arslan; Demir, Mustafa MuammerThe 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. © 2020 Elsevier B.V.Article Citation - WoS: 3Citation - Scopus: 3Green Fabrication of Lanthanide-Doped Hydroxide-Based Phosphors: Y(oh)(3):eu3+ Nanoparticles for White Light Generation(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2019) Güner, Tuğrul; Kuş, Anılcan; Özcan, Mehmet; Genç, Aziz; Şahin, Hasan; Demir, Mustafa MuammerPhosphors can serve as color conversion layers to generate white light with varying optical features, including color rendering index (CRI), high correlated color temperature (CCT), and luminous efficacy. However, they are typically produced under harsh synthesis conditions such as high temperature, high pressure, and/or by employing a large amount of solvent. In this work, a facile, water-based, rapid method has been proposed to fabricate lanthanide-doped hydroxide-based phosphors. In this sense, sub-micrometer-sized Y(OH)(3):Eu3+ particles (as red phosphor) were synthesized in water at ambient conditions in <= 60 min reaction time. The doping ratio was controlled from 2.5-20 mol %. Additionally, first principle calculations were performed on Y(OH)(3):Eu3+ to understand the preferable doping scenario and its optoelectronic properties. As an application, these fabricated red phosphors were integrated into a PDMS/YAG:Ce3+ composite and used to generate white light. The resulting white light showed a remarkable improvement (approximate to 24%) in terms of luminous efficiency, a slight reduction of CCT (from 3900 to 3600 K), and an unchanged CRI (approximate to 60) as the amount of Y(OH)(3):Eu3+ was increased.Article Citation - WoS: 18Citation - Scopus: 46Phosphor-Based White Led by Various Glassy Particles:control Over Luminous Efficiency(The Optical Society, 2019) Yüce, Hürriyet; Güner, Tuğrul; Balcı, Sinan; Demir, Mustafa MuammerGenerating 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. (C) 2019 Optical Society of AmericaArticle Citation - WoS: 18Citation - Scopus: 14Optimization and Performance of Nitrogen-Doped Carbon Dots as a Color Conversion Layer for White-Led Applications(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2019) Güner, Tuğrul; Yüce, Hürriyet; Taşçıoğlu, Didem; Şimşek, Eren; Savacı, Umut; Genç, Aziz; Demir, Mustafa MuammerIn this study, green-emitting nitrogen-doped carbon dots (N-CDots) were synthesized and incorporated into drop-cast composite films for use as color conversion layers in a white-LED configuration to generate white light. In order to resolve the red deficiency of this configuration, a commercial red phosphor was integrated into the system. Moreover, the N-CDots were also processed into polymer/N-CDot composite fibers, for which we determined the amount of N-CDots that yielded adequate white-light properties. Finally, we showed that white light with excellent properties could be generated by employing both of the fabricated N-CDot composites either as drop-cast films or composite fibers. Hence, N-CDots provide a promising alternative to inorganic phosphors that are commonly employed in white-LED configurations.Article Citation - WoS: 45Citation - Scopus: 46Electrospun Polystyrene Fibers Knitted Around Imprinted Acrylate Microspheres as Sorbent for Paraben Derivatives(Elsevier, 2018) Demirkurt, Merve; Ölçer, Yekta Arya; Demir, Mustafa Muammer; Eroğlu, Ahmet EroğluParabens 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.Article Citation - WoS: 39Citation - Scopus: 39Polarized Emission From Cspbbr3 Nanowire Embedded-Electrospun Pu Fibers(IOP Publishing Ltd., 2018) Güner, Tuğrul; Topçu, Gökhan; Savacı, Umut; Genç, Aziz; Sarı, Emre; Demir, Mustafa MuammerInterest in all-inorganic halide perovskites has been increasing dramatically due to their high quantum yield, band gap tunability, and ease of fabrication in compositional and geometric diversity. In this study, we synthesized several hundreds of nanometer long and ∼4 nm thick CsPbBr3 nanowires (NWs). They were then integrated into electrospun polyurethane (PU) fibers to examine the polarization behavior of the composite fiber assembly. Aligned electrospun fibers containing CsPbBr3 NWs showed a remarkable increase in the degree of polarization from 0.17-0.30. This combination of NWs and PU fibers provides a promising composite material for various applications such as optoelectronic devices and solar cells.Article Citation - WoS: 31Citation - Scopus: 36Integration of Triboluminescent Eud4tea Crystals To Transparent Polymers: Impact Sensor Application(American Chemical Society, 2017) İncel, Anıl; Eanes, Mehtap; McMillen, Colin D.; Demir, Mustafa MuammerLanthanide-based organometallic materials are well-known candidate triboluminescent (TL) materials that can show bright emission when a mechanical force is applied. These materials are usually in the form of crystalline powders, and it is often useful to integrate these samples into a polymer matrix in order to achieve processability, enabling coating from a solution/molten state or fabrication as a complex-shaped matrix. In this work, micrometer-sized europium tetrakis (dibenzoylmethide) triethylammonium (EuD4TEA) crystals were synthesized and integrated with various transparent polymers (PMMA, PS, PVDF, and PU) using two approaches: (i) blending and (ii) surface impregnation. In the former method, the crystalline particles were molecularly dissolved; therefore, a TL response cannot be achieved. More than 10 wt % TL crystals in the composite is needed to obtain TL signals. However, TL signal was achieved at 2.5 wt % when a composite was prepared by the latter approach. TL intensity shows exponential decay with consecutive mechanical action. The TL emission of PU-based surface impregnated composite expires with long-lived emission, and maximum TL response with respect to applied force was measured between 2.45 and 42.0 N.Article Citation - WoS: 42Citation - Scopus: 43Investigation of Oxygen Permeation Through Composites of Pmma and Surface-Modified Zno Nanoparticles(John Wiley and Sons Inc., 2009) Hess, Sandra; Demir, Mustafa Muammer; Yakutkin, Vladimir; Baluschev, Stanislav; Wegner, GerhardOxygen permeabilities of nanocomposite films consisting of poly(methyl methacrylate) (PMMA) and different amounts of spherical zinc oxide (ZnO) nanoparticles were determined to investigate the barrier effect of this material with respect to particle content. A method was applied which is based on quenching of an excited phosphorescent dye by oxygen. Possible effects of the nanoparticles on the response of the dye molecules were investigated and were ruled out.Article Citation - WoS: 64Citation - Scopus: 67Hierarchically Structured Metal Oxide/Silica Nanofibers by Colloid Electrospinning(American Chemical Society, 2012) Horzum Polat, Nesrin; Mun˜oz-Espí, Rafael; Glasser, Gunnar; Demir, Mustafa Muammer; Landfester, Katharina; Crespy, DanielWe present herein a new concept for the preparation of nanofibrous metal oxides based on the simultaneous electrospinning of metal oxide precursors and silica nanoparticles. Precursor fibers are prepared by electrospinning silica nanoparticles (20 nm in diameter) dispersed in an aqueous solution of poly(acrylic acid) and metal salts. Upon calcination in air, the poly(acrylic acid) matrix is removed, the silica nanoparticles are cemented, and nanocrystalline metal oxide particles of 4-14 nm are nucleated at the surface of the silica nanoparticles. The obtained continuous silica fibers act as a structural framework for metal oxide nanoparticles and show improved mechanical integrity compared to the neat metal oxide fibers. The hierarchically nanostructured materials are promising for catalysis applications, as demonstrated by the successful degradation of a model dye in the presence of the fibers.Article Citation - WoS: 73Citation - Scopus: 73Toward Transparent Nanocomposites Based on Polystyrene Matrix and Pmma-Grafted Ceo 2 Nanoparticles(American Chemical Society, 2011) Parlak, Onur; Demir, Mustafa MuammerThe association of transparent polymer and nanosized pigment particles offers attractive optical materials for various potential and existing applications. However, the particles embedded into polymers scatter light due to refractive index (RI) mismatch and reduce transparency of the resulting composite material. In this study, optical composites based on polystyrene (PS) matrix and poly(methyl methacrylate) (PMMA)-grafted CeO 2 hybrid particles were prepared. CeO 2 nanoparticles with an average diameter of 18 ± 8 nm were precipitated by treating Ce(NO 3) ·6H 2O with urea in the presence of a polymerizable surfactant, 3-methacyloxypropyltrimethoxy silane. PMMA chains were grafted on the surface of the nanoparticles upon free radical in situ solution polymerization. While blending of unmodified CeO 2 particles with PS resulted in opaque films, the transparency of the composite films was remarkably enhanced when prepared by PMMA-grafted CeO 2 hybrid particles, particularly those having a PMMA thickness of 9 nm. The improvement in transparency is presumably due to the reduction in RI mismatch between CeO 2 particles and the PS matrix when using PMMA chains at the interface.