Sonochemistry and Sonoluminescence in Aqueous AuCl4- Solutions in the Presence of Surface-Active Solutes

The 515 kHz ultrasound-initiated reduction of AuCl 4 - to Au(0) was examined as a function of the concentration of various surface-active solutes. The amount of AuCl 4 - reduced in the presence of ethanol, propan-1-ol, and butan-1-ol was found to be dependent on the surface excess of the alcohol at the gas/solution interface, i.e., the relative concentration of the alcohol at the gas/solution interface compared to the bulk solution concentration. The efficiency of reduction of AuCl 4 - in the presence of the surfactants sodium dodecyl sulfate or octaethylene glycol monodecyl ether was found to be related to the monomer concentration of the surfactant in solution. The light emitted (sonoluminescence) during ultrasonic irradiation of the aqueous solutions was also monitored and compared with the trends observed in the sonochemical experiments. The sonoluminescence was observed to be significantly reduced in the presence of alcohol, and the effect was correlated with the surface excess of the alcohols at the gas/solution interface. In contrast, the effect of the surfactants on the sonoluminescence was highly dependent on concentration and headgroup type of the surfactant.