Browsing by Subject "Electrochemical reductions"

Now showing 1 - 4 of 4
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    Optical and electrochemical properties of polyether derivatives of perylenediimides adsorbed on nanocrystalline metal oxide films
    (Elsevier, 2008) Kus M.; Hakli O.; Zafer C.; Varlikli C.; Demic S.; Özçelik S.; Icli S.
    We report optical and electrochemical properties of polyether derivatives of perylenediimides (PDIs) thin films formed in various materials (semiconductor, insulator, amorphous and self-assembly). Perylenediimides adsorbed on nanocrystalline TiO2 (NT) nanocrystalline alumina (NA), amorphous silicon (PS) and neat self-assemblied (SA) films were prepared and characterized based on spectroscopic, electrochemical, spectro-electrochemical techniques. The absorption and fluorescence spectra of PDIs in chloroform exhibit vibronic features. The fluorescence quantum yields (Φf) of PDIs with end amino substituents in chloroform solutions are over 0.95, while the quantum yield of triethoxyphenyl substituted PDI Φf value is 0.024 in solution. Optical spectroscopy proves that PDIs in metal oxide thin films form aggregated type complexes. An electrochromism, a color change from red to blue/violet, is observed on metal oxide films, that indicates existence of mono and dianion forms of PDIs. Reversibility of electrochemical reductions in NT film depends on the scanning rate. However, electrochromism in NA films is stable and reversibility is independent from scanning rate. Stable mono and diaionic species are formed on NA films. SA films show broad absorption peaks during the voltammetric scan. On the other hand, the first reduction onset potentials of PDIs are almost equal to the onset potential of capacitive current of TiO2 which lead to low efficiency in dye-sensitized solar cells. © 2008 Elsevier B.V. All rights reserved.
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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
    (2013) Çakar I.; Özdokur K.V.; Demir B.; Yavuz E.; Demirkol D.O.; Koçak S.; Timur S.; Ertaş F.N.
    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 (GOx) as the model enzyme. After optimization of the operational conditions, analytical characterization and application of the glucose oxidase GOx biosensor to flow injection analysis mode have been successfully performed. © 2013 Published by Elsevier B.V. All rights reserved.
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    Hydrazine oxidation at gold nanoparticles and poly(bromocresol purple) carbon nanotube modified glassy carbon electrode
    (Elsevier, 2014) Koçak S.; Aslişen B.
    Bromocresol purple monomers were polymerized electrochemically at carbon nanotube modified glassy carbon electrode surface and obtained electrodes were donated as poly(BCP)/CNT/GCE. After electrochemical polymerization, Au nanoparticles were doped on the polymer film carbon nanotube modified glassy carbon electrode surface by electrochemical reduction from their acidic solutions. Modified electrodes are characterized with electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical behavior of hydrazine oxidation was investigated at gold nanoparticles modified poly(BCP)/CNT electrodes in pH 10.0 phosphate buffer solution. The obtained results were compared with other modified electrodes. The best catalytic activity was obtained at AuNPs/poly(BCP)/CNT/GCE due to the shift of oxidation peak to more negative values than other electrodes with a higher current value. The peak potential and current oxidation of hydrazine were obtained at AuNPs/poly(BCP)/CNT/GCE (-28 mV, 205 μA) and poly(BCP)/CNT/GCE (427 mV, 80 μA). Under optimal conditions, the calibration curves for hydrazine were obtained over the range of 5.0 × 10-7-1.0 × 10-3 M. The limit of detection for hydrazine was calculated as 1.0 × 10-7 M for AuNPs/poly(BCP)/CNT/GCE. © 2014 Elsevier B.V.
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    Electrochemical sensing platform based on tyrosinase immobilized magnetite chitosan nanobiocomposite film and its application as catechol biosensor
    (Electrochemical Society Inc., 2019) Polatoğlu İ.
    The easy design of an enzyme electrode using tyrosinase immobilized magnetite chitosan nanobiocomposite film (TMCG) and its applicability for electrochemical sensing platform are reported in this work. The sensor components were characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Stable biomaterial was obtained by chemical immobilization of the enzyme to chitosan structure with glutaraldehyde. Magnetite nanoparticles were homogeneously distributed on the chitosan surface. Nyquist curves revealed that, chitosan and tyrosinase enzyme exhibit higher resistance to the electron transfer while magnetite nanoparticles promote the electron transfer as a result of their nanostructure behaviors. In addition to well defined oxidation peak, new reduction peak was observed from CV analysis after magnetite modification as a result of electrochemical reduction of enzymatically produced o-quinone to the catechol. The developed biosensor (TMCG*) selectively detected the catechol at a sensitivity of 0.057A/M in a linear range from 1 μM to 30 μM with a detection limit of 260 nM and Km value of 22.5 μM. These findings strongly indicate that TMCG* is applicable as an electrochemical sensing platform for detection of the sample that inhibits the tyrosinase enzyme in tap water. © 2019 The Electrochemical Society.