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    Photoelectrocatalytic Oxidation of NADH at a Graphite Electrode Modified with a New Polymeric Phenothiazine
    (Wiley-V C H Verlag Gmbh, 2009) Gligor, Delia; Dilgin, Yusuf; Popescu, Ionel Catalin; Gorton, Lo
    A new approach for photoelectrocatalytic oxidation of NADH is described, based on a graphite electrode (G) modified with a new phenothiazine derivative, polyphenothiazine formaldehyde (PPF). Electrochemical measurements reveal that G/PPF presents a quasireversible voltammetric response, corresponding to a 2e(-)/2H(+) transfer and that G/PPF modified electrodes show electrocatalytic activity for NADH oxidation. When the surface of the G/PPF modified electrode was irradiated with a light source (250 W Halogen lamp), a significant increase in the electrocatalytic current was observed. The second order electrocatalytic rate constant (k(obs,[NADH]=0) = 3.9 x 10(3) M-1 s(-1), pH 7.0) was calculated from rotating disk electrode experiments, performed at various NADH concentrations. From amperometric measurements, it was noticed that, in the presence of light irradiation, the sensitivity of NADH detection (calculated as I-max/K-M ratio) increased ca. 3 times.
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    Öğe
    Poly-phenothiazine derivative-modified glassy carbon electrode for NADH electrocatalytic oxidation
    (Pergamon-Elsevier Science Ltd, 2009) Gligor, Delia; Dilgin, Yusuf; Popescu, Ionel Catalin; Gorton, Lo
    Electropolymerization of a new phenothiazine derivative (bis-phenothiazin-3-yl methane; BPhM) on glassy carbon (GC) electrode generates a conducting film of poly-BPhM. in stable contact with the electrode surface. The heterogeneous electron-transfer process corresponding to the modified electrode is characterized by a high rate constant (50.4 s(-1), pH 7). The CC/poly-BPhM electrode shows excellent electrocatalytic activity toward NADH oxidation. The rate constant for catalytic NADH oxidation, estimated from rotating disk electrode (RDE) measurements and extrapolated to zero concentration of NADH, was found to be 9.4 x 10(4) M-1 s(-1) (pH 7). The amperometric detection of NADH, at +200 mV vs. SCE, is described by the following electroanalytical parameters: a sensitivity of 1.82 mA M-1, a detection limit of 2 mu M and a linear domain up to 0.1 mM NADH. (c) 2008 Elsevier Ltd. All rights reserved.