FORMATION OF UNSTABILIZED OLIGOMERIC SILVER CLUSTERS DURING THE REDUCTION OF AG+ IONS IN AQUEOUS-SOLUTION

Deaerated aqueous AgClO4 solutions containing also 0.2 M methanol were exposed to a high energy electron pulse which produced reducing species (hydrated electrons, H-atoms and CH2OH radicals), and the absorption spectrum of the reduced silver species measured at various times after the pulse. The sharp 300 and 330 nm absorption bands of oligomeric silver clusters could be detected, the life time of the clusters amounting to several seconds. Both the build-up of the clusters by agglomerations of the silver atoms formed initially and the decay of the clusters are catalytically accelerated by sulfate anions, 10-5 M concentrations of the latter already exerting a strong effect. The absorption bands of the clusters are more narrow than in solutions containing a polyanionic stabilizer. The wavelengths of the absorption maxima are the same as for polyphosphate stabilized clusters. © 1990.