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 The effects of growth conditions on the surface properties and photocatalytic activities of anatase TiO2 films prepared via electrochemical anodizing and annealing methods(SPRINGER, 2017) DEMİRCİ, SELİM; Dikici, Tuncay; Yurddaskal, Metin; Demirci, Selim; Celik, ErdalIn the present work, nanostructured TiO2 films were prepared by electrochemical anodization process of titanium in fluoride-containing electrolytes using an innovative approach. After anodization, the TiO2 films were annealed at 480 degrees C for 2 h in air in order to acquire anatase phase transformation and increase its crystallinity. The effects of anodization voltage, electrolyte concentration and anodization time on the formation of TiO2 films and the photocatalytic degradation of methylene blue (MB) were discussed in details. The phase structure and surface morphology of the samples characterized by means of X-ray diffraction and scanning electron microscope. The as-prepared nanostructured TiO2 film anodized in 0.5% HF electrolyte at 15 V for 240 min showed excellent photocatalytic degradation of MB and is promising for environmental purification.Publication Metadata only Influence of electrolyte composition on the microstructure and photocatalytic activity of TiO2 nanostructures(SPRINGER) DEMİRCİ, SELİM; Yilmaz, Ozan; Ebeoglugil, Faruk; Demirci, Selim; Dikici, TuncayIn this study, titanium dioxide (TiO2) nanostructures were produced on pure titanium in different electrolytes at constant voltage of 20 V for 30 min. The crystallographic structure, surface morphology, and optical properties of the films were investigated by XRD, SEM, and UV-vis spectrum, respectively. The wettability of the samples was determined by contact angle measurement equipment. The photocatalytic properties of the TiO2 films were tested by the degradation of a methylene blue (MB) as the model reaction under UV light irradiation. The results showed that the electrolyte composition can play an important role in the surface morphology of nanostructured TiO2 films and therefore on various properties such as optics, electronics, sensing, and degradation. The SEM images of the samples demonstrated that surface morphology was directly affected by the electrolyte composition. It is known that the surface area is a dominant factor affecting the photocatalytic activity of a porous TiO2 layer prepared by anodic oxidation. The TiO2 film (sample C) anodized in 1 M Na2SO4 containing 5 wt.% NH4F exhibited better photocatalytic performance as compared to the other oxide films. This is because a higher surface area with dense pore structure favors more photocatalytic active areas. The photocatalytic degradation efficiency of MB using sample C was reached to 92.35% and rate constant 5.92 x 10(-3), respectively. Moreover, this sample showed lowest band gap energy that was almost 3.167 eV. We believe that new anodic TiO2 nanoporous structures are highly promising in photocatalytic decomposition of water and pollutants elimination.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.