Hydrogen-assisted fabrication of spherical gold nanoparticles through sonochemical reduction of tetrachloride gold(III) ions in water.

Spherical gold nanoparticles (AuNPs) were selectively synthesized through sonochemical reduction of tetrachloride gold(III) ions ([AuCl4](-)) in an aqueous solution of hydrogen tetrachloroaurate(III) tetrahydrate (HAuCl4 · 4H2O) with the aid of hydrogen (H2) gas in the absence of any additional capping agents. On the other hand, various shaped-AuNPs such as spherical nanoparticles, triangular and hexagonal plates were formed from sonochemical reduction of [AuCl4](-) in argon (Ar)-, nitrogen (N2)- or oxygen (O2)-purged aqueous [AuCl4](-) solutions. The selective fabrication of spherical AuNPs assisted by H2 gas is most likely attributed to the generation of hydrogen radicals (H) promoted by the reaction of H2 introduced and hydrogen oxide radicals (OH) produced by sonolysis of water.