Characterization and Catalytic Activity of Gold Nanoparticles Synthesized by Autoreduction of Aqueous Chloroaurate Ions with Fumed Silica

In this report, a novel method for the synthesis of gold nanoparticles on an amorphous silica support is described wherein silanol groups on the surface of the fumed silica spontaneously reduce aqueous chloroaurate ions. This results in the formation of gold nanoparticles that are bound fairly strongly to the fumed silica surface. Alkylamine molecules present in solution were observed to reduce the size of the gold nanoparticles thus formed by self-assembling on the nanoparticles and preventing further growth. The gold nanoparticle size is dependent on the concentration of alkylamine molecules in solution. The gold nanoparticle−fumed silica composite material was found to be catalytically active in the hydrogenation of cyclohexene.