Photochemical formation of colloidal silver: peptizing action of acetone ketyl radical

Abstract

When an aqueous AgClO₄–sodium dodecylsulphate (SDS)–isopropyl alcohol (Prⁱ OH) solution was photolysed with 253.7 nm light, a sharp and intense absorption band of colloidal silver (λ= 390–400 nm) appeared after a relatively long induction period. In contrast, the sharp colloidal absorption rapidly developed when an AgClO₄–SDS–acetone [(CH₃)₂CO] solution was irradiated under the same conditions. It has been shown by chemical analysis and TEM characterization of the reduced silver that some of the colloidal silver agglomerates formed as a result of photolysis were peptized to fine silver particles during irradiation. Acetone ketyl radical formed by excitation of (CH₃)₂CO with 253.7 nm light seems to have an ability to peptize colloidal agglomerate in the solution phase (peptizing action). A novel ‘photo-acetone method’ available for preparation of fine metal particles has been proposed and applied to obtain colloidal gold, copper and platinum.