Sonochemical Formation of Gold Sols

Abstract

The reduction of AuCl 4 - to colloidal gold in the presence of aliphatic alcohols and sodium dodecyl sulfate in aqueous solutions using 20 kHz ultrasound is described. The extent of reduction of AuCl 4 - was found to be directly dependent on the gas−solution interfacial activity of the solutes used. The diameters of the gold colloids produced were in the size range of 9−25 nm. The particle size was dependent on the alcohol concentration in solution and on the hydrophobicity of the alcohol. For a particular alcohol concentration, smaller particles were obtained the greater the hydrophobicity of the alcohol. A detailed mechanism is presented that describes the overall sonochemically initiated reduction of AuCl 4 - leading to the formation of colloidal gold.