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 dip-coating 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.