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

Reduction of HAuCl4 has been investigated pulse radiolytically in water and in water-in-oil microemulsions. Rate constants have been determined for Au3+ + e/sub aq/- → Au2+, 2Au2+ → Au3+ + Au+, and Au+ + R-. → Au0 + R (where R-. is an unidentified radical). On the longer time scale formation of colloidal gold, nAu0 → (Au0)n, has been observed. Rate of colloidal gold formation has also been studied in the bombardment of HAuCl4 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