Electrochemical,microscopic, and EQCM studies of cathodic electrodeposition of ZnO/FAD and anodic polymerization of FAD films modified electrodes and their electrocatalytic properties |
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Authors: | S Ashok Kumar Shen-Ming Chen |
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Institution: | (1) Electroanalysis and Bioelectrochemistry Laboratory, Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, No. 1, section 3, Chung-Hsiao East Road, Taipei, Taiwan, 106, Republic of China |
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Abstract: | Two kinds of chemically modified electrodes were prepared. In the first type of electrodes, zinc oxide (ZnO) and flavin adenine
dinucleotide (FAD) molecules were deposited onto the glassy carbon-, gold-, and SnO2-coated glass electrodes by using cyclic voltammetry from the bath solution containing aqueous 0.1 M zinc nitrate, 0.1 M sodium
nitrate, and 1 × 10−4 M FAD. It was called as ZnO/FAD modified electrodes. The second type of modified electrode was prepared by the electropolymerization
method. Electrochemical polymerization of FAD was carried out from the acidic solution containing 1 × 10−4 M FAD monomers onto electrode surfaces. This poly(FAD)-modified electrode yields a new redox couple in addition to the monomers
redox couple. The influence of the concentrations, pH, and electrocatalytic properties of the ZnO/FAD- and poly(FAD)-modified
electrodes are investigated by means of the in situ technique electrochemical quartz–crystal microgravimetry (EQCM) combined
with cyclic voltammetry and the ex situ technique scanning electron microscopy. From these studies, it appears that the cathodic
deposition of ZnO/FAD-modified electrodes gives only one redox couple, and the anodically polymerized FAD film-modified electrodes
gives two reversible redox couples. The pH dependence of the redox responses were investigated and the kinetics of electron
transfer was evaluated. In addition, the EQCM technique was employed to follow the deposition process of both kinds of modified
electrodes in real time as well as the characteristics of the charge transfer associated with the surface-confined redox-active
couples. The electrocatalytic activity of the poly(FAD)-modified electrode towards the reduction of hydrogen peroxide and
the oxidation of dopamine and ascorbic acid was explored. The important electrocatalytic properties of poly(FAD)-modified
electrode were observed for simultaneous separation of dopamine and ascorbic acid in neutral solution. This poly(FAD)-modified
electrode has several advantages than the previously reported FAD-modified electrodes. |
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