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