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Öğe Amperometric Glucose Biosensor Based on Gold-Deposited Polyvinylferrocene Film on Pt Electrode(Elsevier Advanced Technology, 2006) Sulak, Meral Topçu; Gökdoğan, Özlem; Gülce, Ahmet; Gülce, HandanThe preparations and performances of the novel amperometric biosensors for glucose based on immobilized glucose oxidase (GOD) on modified Pt electrodes are described. Two types of modified electrodes for the enzyme immobilization were used in this study, polyvinyl ferrocene (PVF) coated Pt electrode and gold deposited PVF coated Pt electrode. A simple method forthe immobilization of GOD enzyme on the modified electrodes was described. The enzyme electrodes developed in this study were called as PVF-GOD enzyme electrode and PVF-Au-GOD enzyme electrode, respectively. The amperometric responses of the enzyme electrodes were measured at constant potential, which was due to the electrooxidation of enzymatically produced H2O2. The electrocatalytic effects of the polymer. PVF. and the cold particles towards the electrooxidation of the enzymatically generated H2O2 offers sensitive and selective monitoring of glucose. The biosensor based on PVF-Au-GOD electrode has 6.6 times larger maximum current, 3.8 times higher sensitivity and 1.6 times larger linear working portion than those of the biosensor based on PVF-GOD electrode. The effects of the applied potential. the thickness of the polymeric film. the amount of the immobilized enzyme, pH. the amount of the deposited An, temperature and substrate concentration on the responses of the biosensors were investigated. The optimum pH was found to be pH 7.4 at 25 degrees C. Finally the effects of interferents, stability of the biosensors and applicability to serum analysis of the biosensor were also investigated.Öğe Electrocatalytic oxidation of methanol on poly(vinylferrocene) modified Pt electrode(ELSEVIER SCIENCE SA, 2012) Akgül, Eda; Gülce, Ahmet; Gülce, HandanElectrooxidation of methanol have been studied on the poly(vinylferrocene) (PVF) coated Pt substrate electrode and uncoated Pt substrate electrode in aqueous HClO4 solutions and the results have been compared. The effects of various parameters such as polymeric films thickness, potential scan rates, methanol concentration and media temperature on the electrooxidation of methanol have been investigated. The results have showed that the current values obtained for the electrooxidation of methanol have been up to 19 times higher than the current values obtained with bare Pt substrate under the same conditions. The E-a values for forward scan oxidation of methanol at PVF coated Pt substrate and Pt substrate electrode have been found to be 8.2 kJ mol(-1) and 32.7 kJ mol(-1), respectively. The E-a values for reverse scan oxidation at the PVF coated Pt substrate and Pt substrate electrode have also been calculated as 21.7 kJ mol(-1) and 49.8 kJ mol(-1). respectively. The E-a values for the PVF coated Pt substrate electrode are lower than Pt substrate electrode for methanol electrooxidation indicating that electrocatalytic activity of PVF. Electrooxidation of methanol in this system shows no significant effects of site poisoning by chemisorbed CO. Furthermore, our results suggest that the important role of OH chemisorbed onto polymer matrix in electrocatalysis of methanol on modified electrode. The catalytic efficiency of PVF towards oxidation of methanol has been determined and it has been found to be higher than 100% at all scan rates. The results suggest that the electrooxidation of methanol proceeds on the PVF modified Pt substrate electrode with good catalytic efficiency. Chronoamperometry experiments have been also confirmed electrocatalytic performance of the PVF coating. (C) 2012 Elsevier B.V. All rights reserved.Öğe A ferrocene functionalized polymer: Poly [N-(ferrocenylmethyl)-o-phenylenediamine]. Electrochemical production and spectroelectroelectrochemical investigation in acetonitrile medium(ELSEVIER SCIENCE SA, 2013) Gülce, Handan; Yetkin, Ahmet; Akgül, Eda; Gülce, AhmetAn electroactive and conductive polymer having pendant ferrocene units was prepared from the electrochemical polymerization of the synthesized monomer, N-(ferrocenylmethyl)-o-phenylenediamine in 0.1 M tetrabuthyl-ammonium perchlorate/acetonitrile medium. The poly-N-(ferrocenylmethyl)-o-phenylenediamine (poly-FMOPD) was generated potentiodynamically or potentiostatically at both of indium tin oxide coated glass substrate and Pt electrodes. The poly-FMOPD film was characterized by cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, dry conductivity measurements, ultraviolet-visible absorption spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy. The electrical conductivity of polymer films was determined as 1.0 x 10(-1) and 4 x 10(-2) S cm(-1) depending on the potential scanning range during electropolymerization. The electroactivity of the polymer film retained even after hundreds cycles between their reduced and oxidized states. The spectroelectrochemical analysis demonstrated that the polymer film reveals a reversible cycling with distinctive color changes between neutral and reduced/oxidized forms. For the polymer film, the maximum optical contrasts (Delta T%) were measured as 18% at and 37% at 480 nm by step the potential between (0.00 V)-(1.20 V) and (-0.50 V)-(-1.70 V), respectively. The optical energy band gaps as the onset energy for the pi-pi* transitions are calculated as 1.89 eV, 1.85 eV and 1.88 eV for the neutral, reduced and oxidized states of poly-FMOPD. (C) 2013 Elsevier B. V. All rights reserved.Öğe NaCI' ün çekirdeklenme kinetiğine ağır metal safsızlıklarının etkisi(2014) Ceyhan, Ayhan Abdullah; Baytar, Orhan; Gülce, AhmetBu çalışmada NaClün çekirdeklenme kinetiği üzerine kristalizasyon ortamındaki ağır metal safsızlıklarının (Pb2, Fe3) etkisi incelenmiştir. Çalışmalar, NaClün endüstriyel üretim şartları dikkate alınarak bekleme zamanı ölçümleri yapılarak gerçekleştirilmiştir. Saf ortamda ve safsızlıkların varlığında yürütülen deneylerde karıştırma işleminin NaClün çekirdeklenme hızını artırdığı tespit edilmiştir. Ağır metal safsızlıklarının çekirdeklenme hızını önemli oranda düşürdüğü ve Pb2 safsızlığı için söz konusu etkinin daha belirgin olduğu belirlenmiştir. Aşı kristali varlığının çekirdeklenme hızını artırdığı belirlenmiştir. Ancak, ağır metal varlığının çekirdeklenme hızı üzerindeki olumsuz etkisinin devam ettiği de tespit edilmiştir.Öğe Preparation of polyaniline/ZnO nanocomposites by using arc-discharge synthesized zno nanoparticles and photocatalytic applications(Selçuk Üniversitesi Mühendislik-Mimarlık Fakültesi, 2012) Eskizeybek, Volkan; Gülce, Handan; Gülce, Ahmet; Avcı, Ahmet; Akgül, EdaPolyaniline (PANI) and PANI/ZnO nanocomposites were synthesized by the chemical oxidative polymerization of aniline and aniline with the presence of ZnO nanoparticles, respectively. The ZnO nanoparticles synthesized by arc-discharge method were used in this study to produce PANI/ZnO nanocomposites. Aniline/ZnO nanoparticles molar ratio was changed to investigate the effect of ZnO nanoparticles to the characteristic of the PANI. The scanning electron microscope analysis showed that ZnO nanoparticles were completely dispersed in PANI matrix homogeneously. It is revealed that shifting to the higher wavenumbers occurred by the increasing ZnO nanoparticle content in fourier transform infrared spectroscopy analysis. Furthermore, degradation of malachite green in aqueous solution was carried out with the prepared nanocomposites under ultraviolet irradiation. The experimental results showed that 1.2 g/L of the nanocomposite could catalyze green solution above 98% after 180 min of irradiation.Öğe Preparation of the New Polyaniline/ZnO Nanocomposite and Its Photocatalytic Activity for Degradation of Methylene Blue and Malachite Green Dyes Under UV and Natural Sun Lights Irradiations(ELSEVIER, 2012) Eskizeybek, Volkan; Sarı, Fahriye; Gülce, Handan; Gülce, Ahmet; Avcı, AhmetA new polyaniline (PANI) homopolymer and PANI/ZnO nanocomposite have been successfully synthesized in aqueous diethylene glycol solution medium via the chemical oxidative polymerization of aniline. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, FTIR spectra, UV-vis spectroscopy measurements were used to characterize the resulting PANI homopolymer and PANI/ZnO nanocomposite photocatalysts. The photocatalytic activities of PANI homopolymer and PANI/ZnO nanocomposites were investigated by the degradation of methylene blue (MB) and malachite green (MG) dyes in aqueous medium under natural sunlight and UV light irradiation and the efficiency of the catalysts have been discussed in detail. Results indicate that the addition of the ZnO nanoparticles to the PANI homopolymer enhance the photocatalytic efficiency under natural sunlight irradiation and a little amount of PANI/ZnO nanocomposite photocatalyst (0.4 g/L) degrades both of the dye solutions (MB or MG) with 99% efficiency after 5 h of irradiation under natural sunlight.
