Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
Browse
9 results
Search Results
Article Citation - WoS: 4Citation - Scopus: 4Transparent Films Made of Highly Scattering Particles(Amer Chemical Soc, 2020-01-13) Erdem, Talha; Yang, Lan; Xu, Peicheng; Altintas, Yemliha; O'Neil, Thomas; Caciagli, Alessio; Eiser, ErikaToday, colloids are widely employed in various products from creams and coatings to electronics. The ability to control their chemical, optical, or electronic features by controlling their size and shape explains why these materials are so widely preferred. Nevertheless, altering some of these properties may also lead to some undesired side effects, one of which is an increase in optical scattering upon concentration. Here, we address this strong scattering issue in films made of binary colloidal suspensions. In particular, we focus on raspberry-type polymeric particles made of a spherical polystyrene core decorated by small hemispherical domains of acrylate with an overall positive charge, which display an unusual stability against aggregation in aqueous solutions. Their solid films display a brilliant red color due to Bragg scattering but appear completely white on account of strong scattering otherwise. To suppress the scattering and induce transparency, we prepared films by hybridizing them with oppositely charged PS particles with a size similar to that of the bumps on the raspberries. We report that the smaller PS particles prevent raspberry particle aggregation in solid films and suppress scattering by decreasing the spatial variation of the refractive index inside the film. We believe that the results presented here provide a simple strategy to suppress strong scattering of larger particles to be used in optical coatings.Article Citation - WoS: 3Citation - Scopus: 4The Experimental Determination of Thermophysical Properties of Intermetallic CuAl2 Phase in Equilibrium With (Al Plus Cu Plus Si) Liquid(Academic Press Ltd- Elsevier Science Ltd, 2016-06) Altintas, Yemliha; Aksoz, Sezen; Keslioglu, Kazim; Marasli, Necmettin; Keşlioʇlu, KâzImThe equilibrated grain boundary groove shapes of solid CuAl2 in equilibrium with (Al + Cu + Si) eutectic liquid were observed from a quenched sample by using a radial heat flow apparatus. The Gibbs-Thomson coefficient, (solid + liquid) interfacial energy and grain boundary energy of the solid CuAl2 were determined from these observed shapes. The thermal conductivity of the eutectic solid and the thermal conductivity ratio of eutectic liquid to the eutectic solid in the (Al + 26.82 wt.% Cu + 5.27 wt.% Si) eutectic alloy at its eutectic melting temperature were also measured with a radial heat flow apparatus and a Bridgman-type growth apparatus, respectively. The three phases of (Al + Cu + Si) alloy have detected as Al solution, Si and theta (CuAl2) phases with EDX composition analysis and the microstructure of these phases were photographed by SEM. (C) 2016 Elsevier Ltd. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1The Experimental Determination of Interfacial Energies for Solid Zn in Equilibrium With Zn-Al Liquid(Springer, 2015-06-16) Altintas, Yemliha; Ozturk, Esra; Aksoz, Sezen; Keslioglu, Kazim; Marasli, NecmettinThe equilibrated grain boundary groove shapes of solid Zn in equilibrium with Zn-Al-Sb liquid were observed from a quenched sample using a radial heat flow apparatus. The Gibbs-Thomson coefficient, solid-liquid interfacial energy, and grain boundary energy of the solid Zn were determined from the observed grain boundary groove shapes. The thermal conductivity of the eutectic solid phase for Zn-0.4 at. pct Al-0.4 at. pct Sb alloy and the thermal conductivity ratio of the liquid phase to the solid phase for Zn-0.4 at. pct Al-0.4 at. pct Sb alloy at eutectic temperature were also measured with a radial heat flow apparatus and a Bridgman-type growth apparatus, respectively.Article Citation - WoS: 15Citation - Scopus: 18FRET Enabled Light Harvesting within Quantum Dot Loaded Nanofibers(IOP Publishing Ltd, 2018-01-24) Altintas, Yemliha; Kiremitler, Nuri Burak; Genc, Sinan; Onses, M. Serdar; Mutlugun, EvrenThe spatial control of the nano-emitters in novel light harvesting platforms offers great potential for the manipulation of the excitonic interaction amongst the donor-acceptor pairs of energy transferring agents. In this work, we report colloidal quantum dot loaded electrospun nanofibers as a light harvesting platform to study the excitonic interaction among them. The donor emission lifetime modified from 12.46 ns to 7.45 ns with the change in the ratio of green and red quantum dots in the nanofiber, as a result of confining acceptor quantum dots in close proximity. The spectrally narrow emitter luminescent nanofiber platforms have further been investigated for their potential of white light generation. The hybrid platform of blue LED integrated electrospun nanofibers has been shown to demonstrate a correlated color temperature of 3632.5 K, luminous efficacy of optical radiation value of 307.7 lm/W-opt along with color rendering index value of 60.Article Citation - WoS: 21Citation - Scopus: 21Efficient Forster Resonance Energy Transfer Donors of In(Zn)P/ZnS Quantum Dots(Amer Chemical Soc, 2017-01-26) Altintas, Yemliha; Talpur, Mohammad Younis; Mutlugun, Evren; Altlntas, YemlihaWe demonstrate a detailed investigation of the effect of the type and concentration of zinc precursor on the optical properties of In(Zn)P/ZnS quantum dots. We achieved up to 87% quantum yield along with 54 nm emission bandwidth for the green emitters with changing the concentration of the Zn precursors. Employing efficient green emitters as the donor species, we demonstrated an efficient Forster resonance energy transfer (FRET) couple of green and red emitting InP-based quantum dots. With a FRET efficiency level of 70.3% achieved (analyzed from the donor lifetime with and without an acceptor), we further demonstrated the enhancement of the acceptor emission nearly twofold due to the energy transfer. Our results provide new insights toward the understanding of the excitonic interactions among donor and acceptor quantum dots of the III-V family for light harvesting applications.Article Citation - WoS: 1Citation - Scopus: 1Effect of Sn Contents on Thermodynamic, Microstructure and Mechanical Properties in the Zn90-Bi10 and Bi88-Zn12 Based Ternary Alloys(Springer, 2019-01-10) Esener, Pinar Ata; Altintas, Yemliha; Bayram, Umit; Ozturk, Esra; Marasli, Necmettin; Aksoz, SezenThe thermal conductivity variations with temperature for Zn90-x-Sn-x-Bi10 (x=5,10, 40 and 85wt%) and Bi88-x-Sn-x-Zn-12 (x=1.39, 43.26 and 79.3wt%) alloys were measured by using the linear heat flow method. From thermal conductivity-temperature plots, the coefficients of thermal conductivity for the Zn-Sn-Bi alloys were calculated. The microstructures of Zn-Sn-Bi alloys were observed using scanning electron microscopy (SEM). The existing phases into microstructure were identified energy dispersive X-ray (EDX) analysis. The melting temperatures, the enthalpy of fusion and specific heat change between the liquid and solid phases in the Zn-Sn-Bi alloys were determined from Differential Scanning Calorimetry (DSC) trace. The tensile strength and microhardness of the alloys were measured using a Shimadzu Universal Testing Instrument (Type AG-10 KNG) and Future-Tech FM-700 model microhardness device.Article Citation - WoS: 5Citation - Scopus: 5Cd-Free Quantum Dot Pellets for Efficient White Light Generation(Optical Soc Amer, 2017-11-01) Altintas, Yemliha; Talpur, Mohammad Younis; Mutlugun, EvrenSemiconductor quantum dots have been on demand for niche optoelectronic applications providing color tenability and possessing high quantum yield and high extinction coefficient. Although the investigation of II-VI have attained a mature level of understanding of the photo physical properties, suppression of the nonradiative decay channels and enhancing the optical properties for III-V material systems still remain a challenge. In this study, we have developed and demonstrated a simple, very fast, and efficient strategy to synthesize the highly luminescent III-V group based In(Zn)P quantum dots (QDs) utilized by the effect of core growth temperature, revealing their emission kinetics and their outstanding application for white light generation. Varying the core growth temperature from 240 degrees C to 90 degrees C, limiting the extent of the precursors involved in the synthesis, and a substantial enhancement of the photoluminescence quantum yield up to 75% is demonstrated. Further modification of the synthesis procedure with optimizing the In:P precursor ratio for the first time up to 88.5 +/- 5.5% quantum yield of alloyed core/shell In(Zn)P/ZnS QDs is achieved, in which the whole synthesis process takes only around one hour. In addition, as a demonstration of Cd-free pellets, versatile pellets of green and orange emitting QDs within KCl macrocrystals are prepared. Hybridizing with blue LED, a white light with correlated color temperature of 4597K along with an unprecedentedly high color rendering index of 90 is presented. (C) 2017 Optical Society of AmericaArticle Citation - WoS: 51Citation - Scopus: 53CdSe/ZnS Quantum Dot Films for High Performance Flexible Lighting and Display Applications(IOP Publishing Ltd, 2016-06-10) Altintas, Yemliha; Genc, Sinan; Talpur, Mohammad Younis; Mutlugun, EvrenColloidal quantum dots have attracted significant interest in recent years for lighting and display applications and have recently appeared in high-end market products. The integration of quantum dots with light emitting diodes has made them promising candidates for superior lighting applications with tunable optical characteristics. In this work we propose and demonstrate high quality colloidal quantum dots in their novel free-standing film forms to allow high quality white light generation to address flexible lighting and display applications. High quality quantum dots have been characterized using transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, steady state and time resolved photoluminescence and dynamic light scattering methods. The engineering of colloidal quantum dot composition and its optical properties in stand-alone film form has led to the experimentally high NTSC color gamut of 122.5 (CIE-1931) for display applications, color rendering index of 88.6, luminous efficacy of optical radiation value of 290 lm/W-opt and color temperature of 2763 K for lighting applications.Article Citation - WoS: 44Citation - Scopus: 46Highly Efficient Cd-Free Alloyed Core/Shell Quantum Dots With Optimized Precursor Concentrations(Amer Chemical Soc, 2016) Altintas, Yemliha; Talpur, Mohammad Younis; Unlu, Miray; Mutlugun, EvrenThe chemical composition, the emission spectral bandwidth, and photoluminescence quantum yield of a semiconductor quantum dot (QD) play an important role in the assessment of the performance of the applications related to the quantum dots. Quantum dots based on environmentally friendly compositions with high optical performance have been in demand for high-end technological applications. In this work, we propose and demonstrate a detailed synthesis approach for environmentally friendly and highly efficient InPZnS alloy/ZnS shell quantum dots. Following a systematic study of the ratio and type of the precursors involved, we achieved alloyed core shell InPZnS/ZnS QDs with tunable emission across the visible spectrum, having a record quantum efficiency up to 78% along with a full width at half-maximum as narrow as 45 nm. The effect of the systematic shell growth has been further investigated using time-resolved photoluminescence characterizations along with the observation of the suppression of the nonradiative decay channels, with the photoluminescence lifetime prolonged from 20.3 to 50.4 ns. The development of highly efficient and environmentally friendly QDs will pave the way for robust, sustainable optoelectronic applications.