Browsing by Author "Timur, S"

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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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    A novel ethanol biosensor on pulsed deposited MnOx-MoOx electrode decorated with Pt nanoparticles
    Ozdokur, KV; Demir, B; Atman, E; Tatli, AY; Yilmaz, B; Demirkol, DO; Kocak, S; Timur, S; Ertas, FN
    Transition metal oxides provide low cost alternatives to noble metals due to their unique electrocatalytic and electrochromic properties and display strong interactions with noble metal nanoparticles. Present study describes the use of mixed molybdenum and manganese oxide film electrode enriched with platinum nanoparticles to enhance the catalytic performance in the oxygen reduction reaction (ORR). The mixed oxide film, denominated as GCE/MnOx-MoOx/Pt, was co-deposited by pulsed potential deposition technique and then, it was used as an immobilization matrix for the intact bacterial cells. The resulted whole cell biosensor has served as a sensing platform for ethanol detection by monitoring of oxygen consumption as a result of the bacterial metabolism in the presence of the substrate. Following the optimization experiments, GCE/MnOx-MoOx/Pt/Gluconobacter oxydans biofilm was applied to investigate the analytical characteristics and response time to ethanol as well as operational stability and substrate specificity for other carbon sources. The linear range was found as 0.075-5.0 mM with a response time of 63 s and the developed method was applied to the ethanol determination in alcoholic drinks. Satisfactory recovery figures were obtained in comparison to the standard method. (C) 2016 Elsevier B.V. All rights reserved.
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    Conducting polymers with benzothiadiazole and benzoselenadiazole units for biosensor applications
    Emre, FB; Ekiz, F; Balan, A; Emre, S; Timur, S; Toppare, L
    Poly(4,7-di(2,3)-dihydrothienol[3,4-b][1,4]dioxin-5-yl-benzo[1,2,5]thiadiazole) (PBDT) and poly(4,7-di(2,3)-dihydrothienol[3,4-b][1,4]dioxin-5-yl-2,1,3-benzoselenadiazole) (PESeE) were electrochemically deposited on graphite electrodes and used as immobilization matrices for biosensing studies. After electrochemical deposition of the polymeric matrices, glucose oxidase (GOx) was immobilized on the modified electrodes as the model enzyme. In the biosensing studies, the decrease in oxygen level as a result of enzymatic reaction was monitored at -0.7 V vs Ag/AgCl (3.0 M KCl) and correlated with substrate concentration. The biosensor was characterized in terms of several parameters such as operational and storage stabilities, kinetic parameters (K-m and I-max) and surface morphologies. The biosensor was tested on real human blood serum samples. (C) 2011 Elsevier B.V. All rights reserved.