Au/TiO2 Nanosystems: A Combined RF-Sputtering/Sol-Gel Approach

An original synthetic approach to Au/TiO2 nanosystems is developed. The adopted technique is based on the RF-sputtering of gold (guest) on porous titania xerogels (host) obtained by the sol-gel route. Such a combined synthetic pathway joins the peculiarities offered by the features of the sol-gel layers (porosity, nonbridging groups) and the advantages of plasmochemical methods (conformal coverage, infiltration power). In particular, host titania substrates were first prepared on silica by dipcoating from ethanolic solutions of Ti(OPri)4 (OPri=iso-propoxy) and Hacac (2,4-pentanedione). Subsequently, Au depositions were performed on the as -prepared xerogels in Ar plasmas at low temperatures. The resulting samples were finally annealed in air between 200 and 600 C with the aim of tailoring the system features as a function of thermal treatment and gold content. Their structural, compositional, and morphological evolution was investigated by Glancing Incidence X-ray Diffraction (GIXRD), Transmission Electron Microscopy (TEM), optical absorption spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and Atomic Force Microscopy (AFM). The adopted strategy enabled the synthesis of Au/TiO2 nanosystems with characteristics strongly dependent on the deposited gold amount and processing conditions. In this way, materials with tunable structure, composition, and optical properties could be synthesized.