Study of Anion Adsorption at the Gold-Aqueous Solution Interface by Atomic Force Microscopy

Abstract

The forces between a gold coated colloidal silica sphere and a pure gold plate have been measured in aqueous solution as a function of electrolyte concentration using an atomic force microscope (AFM). Forces in the presence of gold(III) chloride (HAuCl4), sodium chloride, and trisodium citrate were recorded as a function of concentration. Each of these anion species is present during the formation of colloidal gold by the reduction of gold(III) chloride with trisodium citrate. In pure water the force between the gold surfaces was exclusively attractive. In sodium chloride or trisodium citrate solution a repulsive interaction was observed which is attributed to the adsorption of these anions ..