Preparation and electrocatalytic applications of a multilayer nanocomposite consisting of phosphomolybdate and poly(amidoamine)

Deposition of alternating layers of phosphomolybdic acid, PMo12, and generation-4 polyamidoamine dendrimer, PAMAM, on a gold electrode is demonstrated. The gold is first coated with a self-assembled monolayer of 4-aminothiophenol. Based on the charge under cyclic voltammetric peaks, at least 12 layers of PMo12 are deposited with an estimated quantity of 5.2 x 10(-11) mol cm(-2) in each. The voltammetry of PMo12 is consistent with that for solution studies, in that three two-electron processes are observed with formal potentials of 0.381, 0.238 and 0.012 V. However, the dependence of peak current on scan rate is indicative of redox surface-confined species. The PAMAM provided a spacer that led to a multilayer assembly with high conductivity and, because of its size, apparently high permeability. Regarding the latter, efficient catalysis of the reduction of nitrite and the oxidation of arsenite is achieved. (C) 2001 Elsevier Science Ltd. All rights reserved.