Preparation of gold nanoparticles on silica substrate by radio frequency sputtering

RF-sputtering of gold on amorphous silica substrates was used for the preparation of Au nanoparticles on SiO2. Deposition experiments were carried out in Ar plasmas under mild conditions (RF power=5-10 W, total pressure=0.38 mbar, Substrate Temperature<=210°C), focusing in particular on the effect of Sputtering Time (5-30 min) and Substrate Temperature on gold nucleation and coalescence, with the aim of obtaining SiO2-supported Au nanoparticles characterized by precise structural and morphological features. To this aim, several analytical techniques were employed for a thorough characterization of the systems properties, including GIXRD (Glancing Incidence X-Ray Diffraction), TEM (Transmission Electron Microscopy), XPS (X-ray Photoelectron Spectroscopy), AFM (Atomic Force Microscopy) and UV-Vis absorption spectroscopy. In particular, the evolution of optical spectra, i.e., of the SPR (Surface Plasmon Resonance) peak, was used as a probe for the structural features and related to the results obtained by the other characterization techniques. Gold nanoclusters (ca. 4-10 nm) uniformly dispersed on silica matrices were obtained under soft conditions, with morphology ranging from island- to cluster-like. The obtained results give the possibility to achieve a careful modulation of substrate coverage and gold nanoparticle size.