Network films composed of conducting polymer-linked and polyoxometalate-stabilized platinum nanoparticles

The ability of Keggin-type phosphododecamolybdates (PMo12O403-) to undergo chemisorption and to form anionic monolayers on platinum surfaces is explored here to produce stable colloidal solutions of polyoxometalate-protected platinum nanoparticles (size, 5-10 nm, as determined by transmission electron microscopy and scanning tunneling microscopy). By dip-coating in the above solution, the particles can readily be assembled on carbon electrode substrates. The layer-by-layer method, which involves alternate exposures to the solutions of PMo12O403--stabilized Pt nanoparticles and anilinium cations, has been utilized to grow in a controlled manner hybrid network films in which the negatively charged layers of polyoxometalate-protected Pt nanoparticles are linked, or electrostatically attracted, by ultrathin positively charged polyaniline layers. The phosphomolybdate-decorated Pt nanoparticles (immobilized within ultrathin polyaniline film) are attractive for electrocatalysis: they show promising reactivity toward the electroreduction of oxygen.