Formation of Ag-Cu nanoparticles in SiO2 films by sol-gel process and their effect on the film properties

Sol-gel thin films and microcrystalline powders of SiO2 doped with Ag and Cu were obtained under environmental conditions of pressure and temperature. The precursor material was a mixture of water, tetraethyl-orthosilicate, ethanol and aqueous solutions of Ag and Cu salts, the components were taken in ratios known to provide SiO2 matrix material with good structure. The annealing was performed in oxidizing and reducing atmosphere, the temperature varied in the range of 100-800 degrees C. Formation of metal particles of 100 nm order of magnitude was confirmed by X-ray, optical and SEM analysis. In presence of metal particles, the SiO2 matrix was crystallized in alpha-cristobalite at annealing temperature as low as 500 degrees C, and in quartz form at 800 degrees C. A simple model treating the metal-induced low-temperature crystallization is presented. The material obtained is promising for the use as optical filter, gas sensing element and antibacterial agent. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.