Electrochemical behavior and assembly of tetranuclear Dawson-derived sandwich compound [Cd4(H2O)2(As2W15O56)2]16- on 4-aminobenzoic acid modified glassy carbon electrode

The transition metal-substituted heteropolyoxoanion, Cd-4(H2O)(2)(As2W15O56)(2)(12-) (As4W30Cd4), is one of the trivacant Dawson derivatives. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited three steps of four-electron redox waves attributed to redox processes of the tungsten-oxo framework. Through layer-by-layer assembly, the compound was first successfully immobilized on a 4-aminobenzoic acid modified glassy carbon electrode surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bPY)(2)Cl](2+/+) (denoted as QPVP-Os). Thus, prepared multilayer films have been characterized by cyclic voltammetry (CV). X-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy (UV-vis). The electrocatalytic activities of the multilayer films containing As4W30Cd4 have been investigated on the reduction of three substrates of important analytical interests, NO2-, BrO3- and IO3-. And with the increase of the number of As4W30Cd4 layers, the catalytic current towards the reduction of BrO3- was enhanced and the catalytic potential shifted positively. (c) 2004 Elsevier B.V. All rights reserved.