Person: DEMİRCİ, SELİM
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DEMİRCİ
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SELİM
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Publication Metadata only Enhanced photocatalytic activity of micro/nano textured TiO2 surfaces prepared by sandblasting/acid-etching/anodizing process(ELSEVIER SCIENCE SA, 2017) DEMİRCİ, SELİM; Dikici, Tuncay; Demirci, Selim; Erol, MustafaIn this study, micro-textured titanium surfaces were created by sandblasting and acid-etching methods. Nanostructured titanium dioxide (TiO2) films were synthesized on the micro-textured titanium surfaces by anodizing method. Subsequently, anodized (A), acid-etched/anodized (EA), sandblasted/anodized (SA) and sandblasted/acid-etched/anodized (SEA) samples were fabricated. Structural and morphological properties of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, surface roughness and wettability of the samples were evaluated by means of profilometry and contact angle measurement systems, respectively. Finally, the photocatalytic activities of the samples were determined by using aqueous methylene blue (MB) solutions under a specific UV light illumination for different periods of time. The obtained results pointed out that sandblasting and acid-etching treatment improved the surface roughness of the samples significantly. The photocatalytic experimental results showed that micro textured surface accelerated the degradation of MB, if compared to samples which are anodized without any of the regarding surface treatments. To sum up, sandblasted/acid-etched/anodized titanium surfaces exhibited the highest wettability, surface roughness and photocatalytic activity among the samples. The present study may shed new light on the modification of titanium surfaces. (C) 2016 Elsevier B.V. All rights reserved.Publication Metadata only Fast and low-cost fabrication of 1D hematite photoanode in pure water vapor and air atmosphere: Investigation the effect of the oxidation atmosphere on the PEC performance of the hematite photoanodes(PERGAMON-ELSEVIER SCIENCE LTD, 2017) SARIOĞLU, CEVAT; Demirci, Selim; Sarioglu, CevatIn this study, hematite photoanodes were successfully fabricated by thermal oxidation of the commercial cold-rolled steel at 500 degrees C in pure water vapor and air atmosphere. The crystal phase structure, surface morphology, and optical properties of the hematite photoanodes were characterized using an X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM) and UV-VIS spectrophotometer, respectively. The results showed that hematite photoanodes had high crystalline phase and the annealing atmosphere influenced the morphology of the hematite photoanodes. Moreover, nanowhisker and nanorod shaped nanostructures were observed on the substrate. The optical band gap values of the hematite photoanodes varied between 2.38 and 2.70 eV. Photoelectrochemical (PEC) studies of the hematite photoanodes were assessed in the 0.1 M NaOH electrolyte solution using the Mott-Schottky analysis and electrochemical impedance spectroscopy techniques. The PEC findings exhibited that the hematite photoanode annealed 15-min in water vapor had best PEC performance achieving photocurrent density 0.244 mA/cm(2) at 1.6 V vs. V-RHE and highest carrier density value (N-D = 1.15 x 10(21) cm(-3)). Furthermore, the photoanodes annealed in water vapor atmosphere revealed at least three times higher PEC performance than that of photoanodes annealed in air. Thermal oxidation method in water vapor is an efficient methods for fabrication of hematite photoanodes. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only Synthesis and characterization of Ag doped TiO2 heterojunction films and their photocatalytic performances(ELSEVIER, 2016) DEMİRCİ, SELİM; Demirci, Selim; Dikici, Tuncay; Yurddaskal, Metin; Gultekin, Serdar; Toparli, Mustafa; Celik, ErdalIn this study, undoped and silver (Ag) doped titanium dioxide (TiO2) films were successfully synthesized by sol-gel spin coating technique on the Si substrates. Photocatalytic activities of the TiO2 films with different Ag content were investigated for the degradation of methylene blue (MB) under UV light irradiation. The crystal phase structure, surface morphology, chemical and optical properties of Ag-doped TiO2 films were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectrophotometer, and FTIR spectrophotometer. The results showed that the Ag-doped TiO2 films calcined at 500 degrees C had the crystalline anatase phases and the surface morphologies with some cracks. Ag substitution into TiO2 matrix enhanced the photocatalytic activity of TiO2 films under UV light irradiation as compared to the undoped TiO2 film. Furthermore, the results indicated that the 0.7% Ag doped TiO2 film exhibited a superior photocatalytic activity than that of undoped and other Ag-doped TiO2 films. This study demonstrated the potential of an application of Ag doped films to efficiently treat dissolved organic contaminants in water. (C) 2016 Elsevier B.V. All rights reserved.Publication Open Access Production of Zn-doped TiO2 film with enhanced photocatalytic activity(2022-12-01) DEMİRCİ, SELİM; DİKİCİ T., YILMAZ O., Akalin A., DEMİRCİ S., GÜLTEKİN S., YILDIRIM S., YURDDAŞKAL M.In this study, zinc (Zn)-doped titanium dioxide (TiO2) films were prepared using the two steps: anodic oxidation method and heat treatment process. The crystal structure, morphology and elemental composition of the Zn-doped TiO2 films were investigated. These films were characterized by scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicated that the TiO2 films with clear, uniform and short nanopores had a high surface area and high degree of crystallinity. The results showed that the asanodized TiO2 film was successfully obtained as anatase phase at 450 degrees C. The results of XPS analysis confirmed the presence of Zn in the lattice of TiO2 as dopant, and thermal diffusion technique was successfully done as doping method. The photocatalytic performances of the Zn-doped TiO2 films were evaluated in terms of their photodegradation rate of methylene blue (MB) in an aqueous solution under UV light irradiation. The results revealed that the Zn-doped TiO2 film had a higher photocatalytic activity in comparison with the undoped sample. This study inspired that Zn-doped TiO2 films are a great potential material to treat wastewater in industrial field.Publication Open Access Production, characterization, and luminescent properties of Eu3+ doped yttrium niobate-tantalate films(SPRINGEROPEN, 2017-03) DEMİRCİ, SELİM; Yildirim, Serdar; Demirci, Selim; Ertekin, Kadriye; Celik, Erdal; Alicikus, Zumre AricanMonoclinic yttrium tantalate (M'-YTaO4, M '-YTO), and two different kinds of yttrium niobium-tantalate (M '-YTa0.85Nb0.15O4 (M '-YTNO) and Eu3+ doped M '-YTa0.85Nb0.15O4 (M '-YTNO:Eu3+)) were produced by sol-gel method and grown on single crystalline Si (100) substrate by spin coating approach. Structural properties and thermal behaviours of the films were characterized by means of X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and thermogravimetry and differential thermal analysis (TG-DTA). Systematic Steady-state photoluminescence and lifetime measurements in a series of yttrium niobium-tantalate with varying amounts of Eu3+ were presented. The photoluminescence spectra of the films exhibited strong blue (380-400 nm) and red (614 nm) emissions upon ultraviolet excitation. Emission intensities were strongly dependent on the host lattice composition and film morphology. 1.5% Eu3+ doped films exhibited the brightest luminescence and long lifetime extending to 1.22 ms when excited at 254 nm. To the best of our knowledge, this is the first attempt in the production of M '-YTO, M '-YTNO, and M '-YTNO:Eu3+ films on single crystalline Si (100) substrate via sol-gel spin coating.Publication Open Access A study of heating rate effect on the photocatalytic performances of ZnO powders prepared by sol-gel route: Their kinetic and thermodynamic studies(ELSEVIER, 2020-03) TÜNÇAY, MEHMET MASUM; Demirci, Selim; Dikici, Tuncay; Tuncay, Mehmet Masum; Kaya, NusretIn this work, ZnO particles were fabricated by sol-gel method at different heating rate at 500 degrees C for 2 h. The ZnO powders were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and photoluminescence, respectively. The effect of heating rate on photocatalytic activities of ZnO particles was evaluated by degradation of methylene blue (MB). The non-isothermal kinetics and thermodynamic properties were also estimated. The XRD results showed that ZnO had hexagonal wurtzite structure. The different heating rate didn't influence the surface morphology of ZnO powders. It was observed that the heating rate had a profound effect on reduction of band gap and photocatalytic performances. The band gap of the ZnO particles varied from 3.10 to 3.17. The ZnO sample prepared at 1 degrees C/min exhibited the highest photocatalytic activity. Its relative photocatalytic degradation rate and kinetic constant were 92.7% and 1.069x10(-2) min(-1), respectively. The results might be ascribed to low bulk vacancies, high surface oxygen vacancies and narrow band gap energy. Also, ZnO photocatalysts showed good stability after four sequence tests. This study provides a new strategy to improve the photocatalytic performances of ZnO photocatalyst for the degradation of organic contaminant.