Browsing by Author "Özdokur, KV"

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    Pulsed Deposited Manganese and Vanadium Oxide Film Modified with Carbon Nanotube and Gold Nanoparticle: Chitosan and Ionic Liquid-based Biosensor
    Akogullari, S; Çinar, S; Özdokur, KV; Aydemir, T; Ertas, FN; Koçak, S
    Present study describes the synthesis of mixed oxide films of manganese and vanadium by electrochemical pulsed deposition technique on a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNT). The film was further decorated with gold nanoparticles to enhance the reduction signal of dissolved oxygen in pH 5.17 acetate buffer solution. All of the electrochemical synthesized modified electrodes have been characterized with Scanning electron microscopy(SEM), High-resolution transmission electron microscopy (HRTEM), X-Ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD) techniques. The electrode obtained (AuNPs/MnOx-VOx/CNT/GCE) was utilized as a platform for glucose biosensor where the glucose oxidase enzyme was immobilized on the composite film with the aid of chitosan and an ionic liquid. The electrochemical performance of the biosensor was investigated by cyclic voltammetry and the relative parameters have been optimized by amperometric measurements in pH 5.17 acetate buffer solution. The developed biosensor exhibited a linear range for glucose between 0.1-1.0 mM and the limit of detection was calculated as 0.02 mM.
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    Molybdenum oxide/platinum modified glassy carbon electrode: A novel electrocatalytic platform for the monitoring of electrochemical reduction of oxygen and its biosensing applications
    Çakar, I; Özdokur, KV; Demir, B; Yavuz, E; Demirkol, DO; Koçak, S; Timur, S; Ertas, FN
    The reduction of oxygen to water is one of the most important reactions in electrochemistry with regards to the wide range of applications in electrocatalysis, metal corrosion, and fuel cell and mostly in biosensor studies. Present study describes the use of a glassy carbon electrode modified with platinum and molybdenum oxide (Pt-MoOx) in strongly acidic solutions for electrocatalytic reduction of oxygen dissolved in buffer solution for the first time. The dispersion of Pt nanoparticles on MoOx provides larger surface area and better electrocatalytic activity for oxygen reduction and the best response toward dissolved oxygen was obtained with a mole ratio of 1: 90 Pt:Mo in deposition solution. The modified surface was then used as a biosensing platform for the monitoring of oxygen consumption due to the bio-catalytic action of glucose oxidase (GO(x)) as the model enzyme. After optimization of the operational conditions, analytical characterization and application of the glucose oxidase GO(x) biosensor to flow injection analysis mode have been successfully performed. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.
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    Electrochemical Preparation, Characterization of Molybdenum-Oxide/Platinum Binary Catalysts and Its Application to Oxygen Reduction Reaction in Weakly Acidic Medium
    Yavuz, E; Özdokur, KV; Çakar, I; Koçak, S; Ertas, FN
    This study reports a detailed analysis of an electrode material containing molybdenum oxide and platinum nanoparticles which shows superior catalytic effect towards to oxygen reduction in weakly acid medium. The material is sequentially electrodeposited on a glassy carbon electrode from aqueous solutions of MoO42 and PtCl42 either by cycling the potential or by applying pulsed potential technique. Chemical and morphological characterization of the electrode surface was made by X-ray photoelectron spectroscopy, scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The electrode performance towards oxygen reduction reaction was investigated in pH 5.0 acetate buffer solution saturated with oxygen and parameters such as the cell content and electrodeposition conditions were optimized. The performance of the electrode was compared with Pt disk, bare glassy carbon, platinum modified glassy carbon electrodes along with the electrode modified in a single step and named as Pt-MoOx/GCE. Overall results indicated that sequentially deposited molybdenum oxide and platinum modified glassy carbon electrode designated as Pt/MoOx/GCE has shown higher catalytic activity considering the peak location and current intensities. This was consisted with the pulsed electrodeposition process and even higher catalytic activity was obtained than the electrode modified by cycling voltammetry. (C) 2014 Elsevier Ltd. All rights reserved.
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    Development of pulsed deposited manganese and molybdenum oxide surfaces decorated with platinum nanoparticles and their catalytic application for formaldehyde oxidation
    Özdokur, KV; Tatli, AY; Yilmaz, B; Koçak, S; Ertas, FN
    Manganese and molybdenum mixed oxides were co-deposited in a thin film form by pulsed deposition technique on a glassy carbon substrate, and this mixed oxide film was further decorated with platinum nanoparticles. Formaldehyde, being a candidate for proton exchange membrane fuel cell applications, was chosen as the test material for the catalytic activities of the developed surface in alkaline media. The synergetic effect of the mixed metal oxide deposit incorporating Pt nanoparticles was verified by using different mol ratios of the corresponding metal ions and applying pulsed deposition conditions and under optimized conditions and, resultant oxidation peak has shown a significant increase in the peak current accompanied by the small shift in the peak potential. The modified composite electrodes were characterized by SEM, EDX, XPS and EIS. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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    Development of cobalt oxide film modified electrode decorated with platinum nanoparticles as a biosensing platform for phenol
    Kuscu, C; Özdokur, KV; Koçak, S; Ertas, FN
    Recently, cobalt oxides attract a special attention mainly due to their excellent electrocatalytic activity towards various compounds. This study concerns with electrochemical preparation of cobalt oxide modified glassy carbon electrodes decorated with platinum nanoparticle in the pursuit of its catalytic applications. The parameters affecting the deposition conditions have been evaluated by monitoring oxygen reduction reaction (ORR) in pH 5.0 acetate buffer. Under optimal conditions, the composite film electrode surface was utilised as a platform forbiosensor development. Polyphenol oxidase enzyme was immobilised onto the electrode surface for phenol detection, and the influence of solution and operational parameters have been investigated. The medium pH and the enzyme amount have been optimised as pH 7.0 and 0.3 mg, respectively. Chronoamperograms were recorded for phenol detection in micromolar levels.
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    WO3 decorated TiO2 nanotube array electrode: Preparation, characterization and superior photoelectrochemical performance for rhodamine B dye degradation
    Davaslioglu, IÇ; Özdokur, KV; Koçak, S; Çirak, Ç; Çaglar, B; Çirak, BB; Ertas, FN
    An efficient photoelectrocatalyst was synthesized by electrochemical deposition of WO3 on the titanium nanotube (TNT) array by subsequent cycling the potential between -0.6 - 1.0 V vs Ag/AgCl. The structural and morphological properties of the electrode obtained (TNT-WO3) was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopic (SEM) techniques and it was revealed that TNT surfaces were successfully decorated by WO3 species without formation of another oxidation species. Then, the photoelectrocatalytic activity of the composite electrode set at 0.2 V (vs Ag/AgCl), was tested under UV light irradiation on the degradation of Methylene blue (MB), Orange G (OG) and Rhodamine B (RhB), as the model pollutants. Among the azo dyes studied, the electrode has given the best performance against RhB in comparison to the bare TNT electrode. The influence of the deposition conditions on the efficiency was examined and under optimal conditions and it was noted that efficient removal of the dye can be achieved within 10 min. Another advantage of the composite electrode is that PEC performance can be tuned by simply changing the parameters of deposition. (C) 2021 Elsevier B.V. All rights reserved.
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    Photopolymerization and characterization of vinyl imidazole based allyl derivative polymers; Cr3+ and Cd2+ metal adsorption and antibacterial studies
    Saltan, F; Saltan, GM; Ilktac, R; Özdokur, KV
    A new type polymeric adsorbent, poly(allylphenol-co-hydroxyethyl methacrylate-co-vinyl imidazole) (PAHV), is synthesized in this study. 2-Hydroxyethyl methacrylate is used as complementary monomers along with 1-vinyl imidazole and allylphenol monomers. The photopolymerization method is preferred as a synthesis method and benzophenone is used as the photoinitiator. The effectiveness of the PAHV against bacterial species such as Escherichia coli and Staphylococcus aureus is investigated by the Clinical and Laboratory Standards Institute (CLSI) disk diffusion method. The inhibition areas of PA(1)H(1)V(3) and PA(1)H(1)V(1) derivatives against E. coli and S. aureus are measured as 25 mm +/- 0.25 mm and 7 mm +/- 0.1 mm; 20 mm +/- 0.25 mm, and 5 mm +/- 0.1 mm, respectively. Sorption efficiencies (%) at pH = 6 (selected optimum pH) for 100 mu g/L Cd and Cr of the PA(1)H(1)V(1), PA(1)H(3)V(1), and PA(1)H(1)V(3) derivatives are found to be 69.0 +/- 2.7 and 58.3 +/- 6.7, 66.8 +/- 6.2 and 75.8 +/- 5.5, and 97.2 +/- 3.7 and 97.7 +/- 3.2 (n = 3), respectively. Adsorption studies revealed that the PA1H1V3 polymer can be used as an alternative for the sorption of cadmium and chromium. The pseudo-second-order model and Langmuir isotherm model fits for both adsorption processes. The adsorption capacities obtained from the Langmuir isotherm model for chromium and cadmium sorption are 52.63 and 68.49 mu g g(-1), respectively.
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    Electrochemical Determination of Levofloxacin Using Poly(Pyrogallol Red) Modified Glassy Carbon Electrode
    Koçak, ÇC; Aslisen, B; Karabiberoglu, S; Özdokur, KV; Aslan, A; Koçak, S
    In this paper, an electrochemical sensor for levofloxacin detection was developed by electrochemical polymerization of pyrogallol red (PGR) on the glassy carbon electrode (GCE) surfaces. Surface morphology and electrical properties of the Poly(PGR)/GCE obtained was characterized by SEM and EIS techniques. Voltammetric behaviour of the levofloxacin was found pH dependent, and the best response was obtained at pH 6.0 PBS. By monitoring the peak current at around 0.9 V, a wide linear range of calibration graph: from 0.2 mu M- 15 mu M LEV and 15 mu M- 355 mu M for levofloxacin, and very low detection limit of 97 nM were achieved with amperometry. Selectivity of the method developed was proven in the presence of possible interfering substances and the method was successfully employed for levofloxacin detection in pharmaceutical tablet and synthetic urine sample.