Sol-gel synthesis and characterization of Ag and Au nanoparticles in SiO2,TiO2, and ZrO2 thin films

Silver and gold nanoparticles were synthesized by the sol-gel process in Si O2, TiO2, and ZrO2 thin films. A versatile method, based on the use of coor dination chemistry, is presented for stabilizing Ag+ and Au3+ ions in sol-g el systems. Various ligands of the metal ions were tested, and for each sys tem it was possible to find a suitable ligand capable of stabilizing the me tal ions and preventing gold precipitation onto the film surface. Thin film s were prepared by spin-coating onto glass or fused silica substrates and t hen heat-treated at various temperatures in air or H-2 atmosphere for nucle ating the metal nanoparticles. The Ag particle size was about 10 nm after h eating the SiO2 film at 600 degrees C and the TiO2 and ZrO2 films at 500 de grees C. After heat treatment at 500 degrees C, the Au particle size was 13 and 17 nm in the TiO2 and ZrO2 films, respectively. The films were charact erized by UV-vis optical absorption spectroscopy and X-ray diffraction, for studying the nucleation and the growth of the metal nanoparticles, The res ults are discussed with regard to the embedding matrix, the temperature, an d the atmosphere of the heat treatment, and it is concluded that crystalliz ation of TiO2 and ZrO2 films may hinder the growth of Ag and Au particles.