Yazar "Sonmezoglu, Savas" seçeneğine göre listele

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    Facile synthesis of cobalt-doped zinc oxide thin films for highly efficient visible light photocatalysts
    (ELSEVIER SCIENCE BV, 2016) Yildirim, Ozlem Altintas; Arslan, Hanife; Sonmezoglu, Savas
    Cobalt-doped zinc oxide (Co:ZnO) thin films with dopant contents ranging from 0 to 5 at.% were prepared using the sol-gel method, and their structural, morphological, optical, and photocatalytic properties were characterized. The effect of the dopant content on the photocatalytic properties of the films was investigated by examining the degradation behavior of methylene blue (MB) under visible light irradiation, and a detailed investigation of their photocatalytic activities was performed by determining the apparent quantum yields (AQYs). Co2+ ions were observed to be substitutionally incorporated into Zn2+ sites in the ZnO crystal, leading to lattice parameter constriction and band gap narrowing due to the photoinduced carriers produced under the visible light irradiation. Thus, the light absorption range of the Co:ZnO films was improved compared with that of the undoped ZnO film, and the Co:ZnO films exhibited highly efficient photocatalytic activity (similar to 92% decomposition of MB after 60-min visible light irradiation for the 3 at.% Co:ZnO film). The AQYs of the Co:ZnO films were greatly enhanced under visible light irradiation compared with that of the undoped ZnO thin film, demonstrating the effect of the Co doping level on the photocatalytic activity of the films. (C) 2016 Elsevier B.V. All rights reserved.
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    The influence of CdS quantum dots incorporation on the properties of CdO thin films
    (EDP SCIENCES S A, 2013) Gultekin, Aytac; Karanfil, Gamze; Ozel, Faruk; Kus, Mahmut; Say, Ridvan; Sonmezoglu, Savas
    The aim of our work is to obtain nano-structured cadmium oxide (CdO) thin films by sol-gel spin coating method and to investigate the effects of cadmium sulfide quantum dots (CdS QDs) doping on the structural modification and surface morphology evolution. X-ray diffraction (XRD) results show that the intensities of the peaks of the crystalline phase increase with the increase in CdS QDs concentrations. From scanning electron microscopy (SEM) images, the distinct variations in the morphology of the thin films were also observed. In addition, the evolution of surface morphology, roughness and granularity has been characterized by atomic force microscopy (AFM). Moreover, we have performed the optical characteristics of the thin films such as transparency, energy band gap and Urbach tail. The optical band gap of the thin films increases from 2.23 to 2.51 eV with the increase in CdS QDs concentrations due to the Moss-Burstein effect. The enhanced values of the transparency, energy band gap and crystallity indicate that addition of CdS QDs can be used to modify the optical, structural and morphological properties of CdO thin films.
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    Penternary chalcogenides nanocrystals as catalytic materials for efficient counter electrodes in dye-synthesized solar cells
    (NATURE PUBLISHING GROUP, 2016) Ozel, Faruk; Sarilmaz, Adem; Istanbullu, Bilal; Aljabour, Abdalaziz; Kus, Mahmut; Sonmezoglu, Savas
    The penternary chalcogenides Cu2CoSn(SeS)(4) and Cu2ZnSn(SeS)(4) were successfully synthesized by hot-injection method, and employed as a catalytic materials for efficient counter electrodes in dye-synthesized solar cells (DSSCs). The structural, compositional, morphological and optical properties of these pentenary semiconductors were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectrometer (EDS) and ultraviolet-visible (UV-Vis) spectroscopy. The Cu2CoSn(SeS)(4) and Cu2ZnSn(SeS)(4) nanocrystals had a single crystalline, kesterite phase, adequate stoichiometric ratio, 18-25 nm particle sizes which are forming nanospheres, and band gap energy of 1.18 and 1.45 eV, respectively. Furthermore, the electrochemical impedance spectroscopy and cyclic voltammograms indicated that Cu2CoSn(SeS)(4) nanocrystals as counter electrodes exhibited better electrocatalytic activity for the reduction of iodine/iodide electrolyte than that of Cu2ZnSn(SeS)(4) nanocrystals and conventional platinum (Pt). The photovoltaic results demonstrated that DSSC with a Cu2CoSn(SeS)(4) nanocrystals-based counter electrode achieved the best efficiency of 6.47%, which is higher than the same photoanode employing a Cu2ZnSn(SeS)(4) nanocrystals (3.18%) and Pt (5.41%) counter electrodes. These promising results highlight the potential application of penternary chalcogen Cu2CoSn(SeS)(4) nanocrystals in low-cost, high-efficiency, Pt-free DSSCs.
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    A photoelectrochemical device for water splitting using oligoaniline-crosslinked [Ru(bpy)(2)(bpyCONHArNH(2))](+2) dye/IrO2 nanoparticle array on TiO2 photonic crystal modified electrode
    (PERGAMON-ELSEVIER SCIENCE LTD, 2016) Yildiz, Huseyin Bekir; Carbas, Buket Bezgin; Sonmezoglu, Savas; Karaman, Mustafa; Toppare, Levent
    This article describes the construction of photoelectrochemical cell system splitting water into hydrogen and oxygen using UV-vis light under constant applied voltage. Oligoaniline-crosslinked 2-(4-aminobenzyl)malonic acid functionalized IrO2 center dot nH(2)O nanoparticles and visible light absorbing dye, [Ru(bpy)(2)(bpyCONHArNH(2))(+2)] arrays on titanium dioxide (TiO2) photonic crystals modified electrodes were used as photoanode, and nanostructures based on bonding of Pt nanoparticles by using electropolymerization on poly 4-(2,5-di(thiophene-2-il)-1H-pyrrol-1-il)benzenamine P(SNS-NH2) conducting polymer modified gold electrode acted as cathode. Each component in anode and cathode of the system was characterized successfully using the methods related. Some optimization studies such as the molar concentration ratio of [Ru(bpy)(2)(bpyCONHArNH(2))(+2)] dye to IrO2 center dot nH(2)O nanoparticles, the optimum cycle number of each components and thickness of TiO2 film were performed in order to investigate the system performance. Furthermore, the photocurrent generation capacity of the photoanode against oxygen resulting and UV stability experiments of photoanode were also investigated. After obtained all necessary informations and improvements of the system, the cell was constructed, and corresponding hydrogen gas evolution from water splitting was calculated as 1.25 x 10(-8) mol/cm(2) by using a gas chromatography (GC). The cell generated a photocurrent with a quantum yield of 3.5%. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Preparation of MIP-based QCM nanosensor for detection of caffeic acid
    (ELSEVIER SCIENCE BV, 2014) Gultekin, Aytac; Karanfil, Gamze; Kus, Mahmut; Sonmezoglu, Savas; Say, Ridvan
    In the present work, a new caffeic acid imprinted quartz crystal microbalance (QCM) nanosensor has been designed for selective assignation of caffeic acid in plant materials. Methacrylamidoantipyrine-iron (III) [MAAP-Fe(III)] as metal-chelating monomer has been used to prepare selective molecular imprinted polymer (MIP). MIP film for detection of caffeic acid has been developed on QCM electrode and selectivity experiments and analytical performance of caffeic acid imprinted QCM nanosensor has been studied. The caffeic acid imprinted QCM nanosensor has been characterized by AFM. After the characterization studies, imprinted and non-imprinted nanosensors was connected to QCM system for studies of connection of the target molecule, selectivity and the detection of amount of target molecule in real samples. The detection limit was found to be 7.8 nM. The value of Langmuir constant (b) (4.06 x 10(6)) that was acquired using Langmuir graph demonstrated that the affinity of binding sites was strong. Also, selectivity of prepared caffeic acid imprinted nanosensor was found as being high compared to chlorogenic acid. Finally, the caffeic acid levels in plant materials was determined by the prepared QCM nanosensor. (C) 2013 Elsevier B.V. All rights reserved.
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    Synthesis and characterisations of Au-nanoparticle-doped TiO2 and CdO thin films
    (PERGAMON-ELSEVIER SCIENCE LTD, 2014) Gultekin, Aytac; Karanfil, Gamze; Ozel, Faruk; Kus, Mahmut; Say, Ridvan; Sonmezoglu, Savas
    In the present study, pure and gold nanoparticle (Au NP)-doped titanium dioxide (TiO2) and cadmium oxide (CdO) thin film were prepared by the sal-gel method, and the effect of Au NP doping on the optical, structural and morphological properties of these thin films was investigated. The prepared thin films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible-near infrared (UV-Vis-NIR) spectra. While the optical band increases from 3.62 to 3.73 for TiO2 thin films, it decreases from 2.20 to 1.55 for CdO thin films with increasing Au doping concentration. Analysis of XRD indicates that the intensities of peaks of the crystalline phase have increased with the increasing Au NP concentrations in all thin films. SEM images demonstrate that the surface morphologies of the samples were affected by the incorporation of Au NPs. Consequently, the most significant results of the present study are that the Au NPs can be used to modify the optical, structural and morphological properties of TiO2 and CdO thin films. (C) 2014 Elsevier Ltd. All rights reserved.
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    Ternary copper-tungsten-disulfide nanocube inks as catalyst for highly efficient dye-sensitized solar cells
    (PERGAMON-ELSEVIER SCIENCE LTD, 2018) Gulen, Mahir; Sarilmaz, Adem; Patir, Imren Hatay; Ozel, Faruk; Sonmezoglu, Savas
    In this report, ternary copper-tungsten-disulfide (Cu2WS4) nanocube inks are successfully synthesized via colloidal synthesis process, utilizing metal chloride as cation sources, sulphur powder combined with oleylamine as coordinating solvent and ligand, and employed, for the first time, as catalyst for counter electrode (CE) to build up a low-cost/high-efficient dye-sensitized solar cell (DSSC). The composition, structure and morphology of these nanocubes are characterized by performing pertinent analyses. The experimental results indicate that the nanocubes are single phase, nearly stoichiometric composition and a mean size of 200 nm. From outstanding electrochemical performance, Cu2WS4 CE exhibits excellent catalytic activity towards iodine redox couples in the electrolyte and fast electron-transfer at the interfaces of CE/electrolyte owing to its larger surface area, more conductive network, lower charge transfer resistance and strong adherence of CWS nanocubes on substrate compare to Pt. The CWS-based cell displays a higher power conversion efficiency of 8.94% than that with Pt CE (8.00%), as well as an excellent reversibility/durability with long-term stability. The newly developed material confirms as valuable alternatives to Pt-free CEs for reduction in DSSCs and is of peculiar interest because of its low-cost, high stability simple fabrication process and impressive photovoltaic performance. (C) 2018 Elsevier Ltd. All rights reserved.