A simple and effective chemical route for the preparation of uniform nonaqueous gold colloids

In this paper, we report a simple and clean method of producing uniform nonaqueous gold colloids by the chemical reduction of chloroauric acid (HAuCl₄) using the oxygen-free organic supporting medium formamide itself as reducing agent in the presence of the stabilizer poly(vinylpyrrolidone) (PVP). The reduction of HAuCl₄ can take place easily at room temperature in the new reducing system without introducing foreign reducing agents. A two-step reaction process to gold particles was suggested from the kinetics analysis for the formation of gold colloids in formamide systems. The difference in the production of gold particles in formamide solution from the established route in aqueous solution was also depicted. This new and effective chemical route also provides an alternative method to produce other uniform transition-metal particles in nonaqueous solvents.