Charged silsesquioxane used as a vehicle for gold nanoparticles to perform the synthesis of catalyst xerogels

Abstract

The water soluble charged silsesquioxane that contains the bridged 1,4-diazoniabicyclo[2.2.2]octane chloride group, was used as stabilizing agent and size controller in the synthesis of gold nanoparticles smaller than 15 nm in aqueous medium. The gold nanoparticle dispersion was converted in solid powder form by evaporation. This powder presented organized structure imposed by the presence of charged organic group, similar to organized structure already observed for pure silsesquioxane. The gold nanoparticles in solid powder form presented high storage stability for several months, at ambient conditions, and can be completely redispersed in water again. After redispersion, the optical properties of gold nanoparticles, observed by ultra-violet and visible spectroscopy, and their morphological characteristics, investigated by transmission electron microscopy, are preserved. The gold nanoparticle aqueous dispersion was used as a vehicle of nanoparticles in the synthesis of sol-gel silica based hybrid material. This xerogel was characterized by N-2 adsorption-desorption isotherms, showing 260 m(2)g(-1), and it was applied in a satisfactory way as catalyst for p-nitrophenol reduction to p-aminephenol.