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    Covalent grafting of three flavonoids onto the glassy carbon electrode surface by cyclic voltammetry
    (WALTER DE GRUYTER GMBH, 2011) Mulazimoglu, Ibrahim Ender; Ustundag, Zafer; Ozkan, Erdal; Solak, Ali Osman
    Electrochemical oxidation of quercetin (QR), 3-hydroxyfl avone (3HF), and baicalein (BN) and their grafting onto the glassy carbon (GC) electrode have been studied using the cyclic voltammetric (CV) technique. Electrochemical studies were performed within a one-compartment three-electrode cell at room temperature. The modification was carried out only in nonaqueous media, while the electrochemical characterization was done in both aqueous and nonaqueous media. In the nonaqueous experiments, 0.1 m tetrabutylammonium tetrafluoroborate in acetonitrile was used, whereas in the aqueous experiments, Britton-Robinson buffer solutions (pH = 2) and 0.1 m KCl solutions were. Surface modifi cations were performed by CV for all compounds. The presence of QR, 3HF, and BN at the GC electrode surface was characterized by CV, electrochemical impedance spectroscopy, contact angle measurement, ellipsometry, and atomic force microscopy.
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    Electrochemical and spectroelectrochemical investigation of the behaviors of HF, 3-HF, 6-HF, 3,6-DHF on glassy carbon electrode surfaces
    (WALTER DE GRUYTER GMBH, 2011) Dundar, Ezher; Mulazimoglu, Ibrahim Ender; Ozkan, Erdal
    An electrochemical investigation of hydroxyflavone, HF; 3-hydroxyflavone, 3-HF; 6-hydroxyflavone, 6-HF; and 3,6-dihydroxyflavone, 3,6-DHF oxidation on a glassy carbon (GC) electrode was carried out using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical oxidation is a complex process, which proceeds in a cascade mechanism, related to the hydroxyl groups of HF, 3-HF, 6-HF, and 3,6-DHF molecules. The hydroxyl group is the first to be oxidized by a one-or two-electron and one-or two-proton irreversible or quasi-reversible oxidation-reduction reaction, followed by an irreversible oxidation reaction due to the hydroxyl groups. The electron and proton oxidation process at the first peak led to the formation of the corresponding quinone, which is an electrochemically active and unstable species, as evidenced by the dependence of the cyclic voltammogram profile on the applied scan rate, in agreement with the electrochemical and then chemical mechanism.
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    High energetic body source and strong antioxidant quercetin, morin and rutin: Their covalent grafting onto the glassy carbon electrode surfaces and investigation of surface properties
    (SILA SCIENCE, 2012) Mulazimoglu, Ibrahim Ender; Ozkan, Erdal; Solak, Ali Osman
    Herein, electrochemical oxidation and grafting of quercetin, morin and rutin as important biological molecules has been studied with the cyclic voltammetry technique by using a glassy carbon electrode. Electrochemical studies have beep performed potentiostatically within a one-compartment three-electrode cell at room temperature. Glassy carbon electrode was used as a working electrode and Pt was used as a wire counter electrode. Ag/Ag+ (10 mM AgNO3), non-aqueous reference electrode calibrated to the E-1/2 of ferrocene redox probe and Ag/AgCl/KCl (sat.), an aqueous reference electrode calibrated to the E-1/2 of Fe(CN)(6)(3-) redox probe respectively. The modification and surface characterizations were carried out in both aqueous and non-aqueous media. 0.1 M tetrabutylammonium tetrafluoroborate in acetonitrile was used in non-aqueous experiments, Britton-Robinson buffer solution (pH=2) and 0.1 M KCl solution were used in aqueous experiments. Before each experiment the solution was de-aerated by the bubbling of Argon to remove the oxygen effects from the experiment results. Surface modification experiments were performed in the +0.3 V and +2.8 V potential ranges with a scan rate of 0.1 V s(-1) and 10 cycles for all molecules. The presence of quercetin, morin and rutin at the glassy carbon electrode surface was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy.
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    Investigation of Electrochemical Behaviour of Quercetin on the Modified Electrode Surfaces with Procaine and Aminophenyl in Non-Aquous Medium
    (WWW PUBL PTE, 2008) Mulazimoglu, Ibrahim Ender; Ozkan, Erdal
    In this study, cyclic voltammetry and electrochemical impedance spectroscopy have been used to investigate the electrochemical behaviour of quercetin (3,3',4',5,7-pentahydroxyflavone) on the procaine and aminophenyl modified electrode. The modification of procaine and aminophenyl binded electrode surface with quercetin was performed in +0,3/+2,8 V (for procaine) and +0,4/+1,5 V (for aminophenyl) potential range using 100 mV s(-1) scanning rate having 10 cycle. A solution of 0.1 M tetrabutylammonium tetra fluoroborate in acetonitrile was used as a non-aquous solvent. For the modification process a solution of 1 mM quercetin in 0.1 M tetrabutylammonium tetrafluoroborate was used. In order to obtain these two surface, a solution of 1 mM procaine and 1 mM nitrophenyl diazonium salt in 0.1 M tetrabutylammonium tetrafluoroborate was used. By using these solutions bare glassy carbon electrode surface was modified. Nitrophenyl was reduced to amine group in 0.1 M HCl medium on the nitrophenyl modified glassy carbon elelctrode surface. Procaine modified glassy carbon electrode surface was quite electroactive. Although nitrophenyl modified glassy carbon elelctrode surface was electroinactive, it was activated by reducing nitro group into amine group. For the characterization of the modified surface I mM ferrocene in 0.1 M tetrabutylammonium tetrafluoroborate for cyclic voltammetry and 1 mM ferricyanide/ferrocyanide (1:1) mixture in 0,1 M KCI for electrochemical impedance spectroscopy were used.