Laser and pulse radiolytically induced colloidal gold formation in water and in water-in-oil microemulsions

Abstract

Reduction of HAuCl/sub 4/ has been investigated pulse radiolytically in water and in water-in-oil microemulsions. Rate constants have been determined for Au/sup 3 +/ + e/sub aq//sup -/ ..-->.. Au/sup 2 +/, 2Au/sup 2 +/ ..-->.. Au/sup 3 +/ + Au/sup +/, and Au/sup +/ + R/sup -/. ..-->.. Au/sup 0/ + R (where R/sup -/. is an unidentified radical). On the longer time scale formation of colloidal gold, nAu/sup 0/ ..-->.. (Au/sup 0/)n, has been observed. Rate of colloidal gold formation has also been studied in the bombardment of HAuCl/sub 4/ solutions by 353-nm 60-mJ 3-5-ns laser pulses. Hydrodynamic diameters and polydispersities of empty and colloidal-gold-containing microemulsions have been determined by electron micrography. There are a number of advantages of forming colloidal particles in microemulsions. Under identical conditions a greater amount of colloidal particles is formed than that in water. Colloidal gold particles formed in microemulsions are smaller and more uniform than those obtained in homogeneous solutions.