Surface chemistry of colloidal silver: Reduction of adsorbed Cd2 ions and accompanying optical effects

Abstract

Cadmium ions can be reduced by 1-hydroxyethylmethyl radicals in solutions containing colloidal silver particles (about 40 Å diameter). The mechanism is postulated to consist of the transfer of electrons from the radicals to the colloidal particles followed by the reduction of adsorbed Cd2+ ions. The Cd atoms formed cause a blue shift of the surface plasmon absorption band of silver. This is explained by free electron donation from adsorbed Cd into the silver particles. At a coverage of 3 monolayers, the surface plasmon band is shifted to 260 nm, where pure cadmium absorbs. Adsorbed Cd atoms at a coverage of less than 0.4 monolayers cannot be reoxidized by methyl viologen; at higher coverages..