Yazar "Ozturk, Sadullah" seçeneğine göre listele

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    Electrochemical Growth of Pd Doped ZnO Nanorods
    (ELECTROCHEMICAL SOC INC, 2015) Kosemen, Arif; Kosemen, Zuhal Alpaslan; Ozturk, Sadullah; Kilinc, Necmettin; San, Sait Eren; Tunc, Ali Veysel
    In this work, dense arrays of pure and Pd doped zinc oxide (ZnO) nanorods (NRs) were fabricated by an electrochemical growth. Pure and Pd doped ZnO NRs were characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and optic spectroscopy. Structural studies confirmed that pure and doped ZnO NRs present the hexagonal wurtzite crystal structures. The optical properties of pure and doped ZnO NRs were found to present redshift by increasing doping concentration. The diameters of the NRs increase with increasing Pd doping concentration under same condition. Compared with pure ZnO NRs, the Pd doped ZnO NRs presents improved optical properties in terms of bandgap energy from 3.24 eV to 1.97 eV. These bandgap values were obtained by optical absorption using a UV-Visible spectrophotometer. In addition, Pd doping concentration in ZnO affects the active species on the surface such as oxygen deficiencies and hydroxyls. The electrochemically growing mechanism is also discussed in detail in the scope of this work. (C) 2015 The Electrochemical Society. All rights reserved.
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    Electrochemically growth of Pd doped ZnO nanorods on QCM for room temperature VOC sensors
    (ELSEVIER SCIENCE SA, 2016) Ozturk, Sadullah; Kosemen, Arif; Kosemen, Zuhal Alpaslan; Kilinc, Necmettin; Ozturk, Zafer Ziya; Penza, Michele
    Pristine and various palladium (Pd) doped ZnO nanorods have been synthesized on the quartz crystal microbalance (QCM) for volatile organic compound (VOCs) sensors at room temperature. The doping concentrations were varied from 0 mol% to 2.5 mol% by using electrochemical deposition method. The diameters of the fabricated nanorods were in the range of 100-200nm, and were increased with Pd doping. The tested VOCs included alcohols (ethanol, methanol, isopropyl), ester (ethyl acetate), aromatic (toluene, xylene), ketone (acetone) and chloroform in the different concentrations. The results indicated that the sensitivity of the sensing materials was enhanced with the increasing Pd doping concentrations except for the acetone and chloroform. The undoped ZnO nanorod sensor showed higher sensor response against to acetone and chloroform while exposing high concentration of two analytes due to the absorbing/adsorbing mechanism. All undoped and Pd doped nanorods sensors showed the highest sensitivity to xylene. (C) 2015 Elsevier B.V. All rights reserved.
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    Fabrication of 1D ZnO nanostructures on MEMS cantilever for VOC sensor application
    (ELSEVIER SCIENCE SA, 2014) Kilinc, Necmettin; Cakmak, Onur; Kosemen, Arif; Ermek, Erhan; Ozturk, Sadullah; Yerli, Yusuf; Urey, Hakan
    This study reports the fabrication method and sensing performance for novel 1D zinc oxide (ZnO) nanorods and nanotubes grown on nickel MEMS cantilevers. The fabrication of the nanostructures and the cantilevers are simple and low-cost using standard lithography, electrodeposition, and hydrothermal etching processes. 1D ZnO nanostructures increase the total sensitive area for biological and chemical sensor applications. We performed experiments with various VOCs with a real-time sensor system developed in our laboratory. While Ni microcantilevers produced no signal, ZnO nanostructure coated microcantilevers showed good sensitivity and repeatable changes. Furthermore, the nanotube coated microcantilevers showed more than 10 fold increase in sensitivity compared to the nanorod coated microcantilevers which can be explained to the fact that ZnO nanotubes have higher surface area and subsurface oxygen vacancies and these provide a larger effective surface area with higher surface-to-volume ratio as compared to ZnO nanorods. The tests are performed using dynamic mode of operation near resonant frequency using magnetic actuation and optical sensing. The phase stability and the limit of detection of ZnO nanotube coated microcantilevers exposed to diethylamine (DEA) were 0.02 degrees and lower than 10 ppm, respectively. ZnO nanostructure coated microcantilevers have good potential for VOC sensor applications especially for amine groups. (C) 2014 Elsevier B.V. All rights reserved.
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    Pd thin films on flexible substrate for hydrogen sensor
    (ELSEVIER SCIENCE SA, 2016) Ozturk, Sadullah; Kilinc, Necmettin
    In this work, palladium (Pd) thin films were prepared via RF sputtering method with various thicknesses (6 nm, 20 nm and 60 nm) on both a flexible substrate and a hard substrate. Hydrogen (H-2) sensing properties of Pd films on flexible substrate have been investigated depending on temperatures (25-100 degrees C) and H-2 concentrations (600 ppm - 10%). The effect of H-2 on structural properties of the films was also studied. The films were characterized by Scanning Electron Microscopy (SEM) and X-ray diffraction. It is found that whole Pd films on hard substrate show permanent structural deformation after exposed to 10% H-2 for 30 min. But, this H-2 exposure does not causes any structural deformation for 6 nm Pd film on flexible substrate and 6 nm Pd film on flexible substrate shows reversible sensor response up to 10% H-2 concentration without any structural deformation. On the other hand, Pd film sensors that have the thicknesses 20 nm and 60 nm on flexible substrate are irreversible for higher H-2 concentration (>2%) with film deformation. The sensor response of 6 nm Pd film on flexible substrate increased with increasing H-2 concentration up 4% and then saturated. The sensitivity of the film decreased with increasing operation temperature. (C) 2016 Elsevier B.V. All rights reserved.
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    Poly(3-Methylthiophene) Thin Films Deposited Electrochemically on QCMs for the Sensing of Volatile Organic Compounds
    (MDPI AG, 2016) Ozturk, Sadullah; Kosemen, Arif; Sen, Zafer; Kilinc, Necmettin; Harbeck, Mika
    Poly(3-methylthiophene) (PMeT) thin films were electrochemically deposited on quartz crystal microbalance QCM transducers to investigate their volatile organic compound (VOC) sensing properties depending on ambient conditions. Twelve different VOCs including alcohols, ketones, chlorinated compounds, amines, and the organosphosphate dimethyl methylphosphonate (DMMP) were used as analytes. The responses of the chemical sensors against DMMP were the highest among the tested analytes; thus, fabricated chemical sensors based on PMeT can be evaluated as potential candidates for selectively detecting DMMP. Generally, detection limits in the low ppm range could be achieved. The gas sensing measurements were recorded at various humid air conditions to investigate the effects of the humidity on the gas sensing properties. The sensing performance of the chemical sensors was slightly reduced in the presence of humidity in ambient conditions. While a decrease in sensitivity was observed for humidity levels up to 50% r.h., the sensitivity was nearly unaffected for higher humidity levels and a reliable detection of the VOCs and DMMP was possible with detection limits in the low ppm range.