Polyoxometalate modified electrodes: from a monolayer to multilayer structures

We describe the strong and spontaneous adsorption of different polyoxometalates on a carbon filled polycarbonate electrode and on glassy carbon. The modification of the surface occurs by dipping the electrode in a polyoxometalate solution at open circuit. The resulting first monolayer of polyoxometalate is used to anchor an adlayer of cations like NH3+ (CH2)(x)NH3+, Hg-2(2+) or Ag+ by electrostatic interaction. In this latter case the subsequent reduction of the metal ions leads to the formation of a metal layer on top of the polyoxometalate layer. Generally the cationic adlayer can be used to adsorb a second polyoxometalate layer or other anions like PtCl62-. The repeated alternate adsorption of anions and cations by this simple dipping procedure leads to molecular sandwiches with high stability and interesting redox properties. (C) 1999 Elsevier Science S.A. All rights reserved.