The photoinduced formation of gold nanoparticles in a mesoporous titania gelmonolith

Abstract

Spherical gold nanoparticles with diameters less than 8 nm have been prepared bythe photoinduced reduction of hydrogen tetrachloroaurate via a one-step sol–gelprocess. The as-prepared Au nanoparticles are highly dispersed in a mesoporousTiO2 gel monolith and are exposed to the external ambient atmosphere with asurface plasmon resonance absorption band centered at 578 nm. The resultsshow that the size, size distribution, and dispersion of Au nanoparticles in thetitania monolith are strongly dependent on the ultraviolet irradiation time ofAuCl4− ions in the titania sol. The Au nanoparticles are found to be more uniform and smaller insize and more highly dispersed in the titania monolith with longer irradiation time.The crystallization of titania from the amorphous phase to the anatase phase isfound to be suppressed at room temperature, and this is attributed to the smallerand highly dispersed Au nanoparticles on the surface of the colloids of titania.