Thermal stability of silver nanoparticles and SiO₂ composite films

Nano-Ag-SiO₂ composite films with Ag nanoparticles embedded in SiO₂ were prepared by sol-gel method via hydrolyze reactions. The thermal stabilization of nano-Ag-SiO₂ film was investigated by the absorbance spectrum of localized surface plasmon resonance (SPR) of Ag nanoparticles. The nano-Ag-SiO₂ film was further characterized by thermogravimety-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersire spectrometer(EDS). The results show that the SPR peaks of Ag nanoparticles in the films appear and strengthen after annealeding, then weaken and finally disappear when the annealing temperature increases from 200 to 900°C, with the maximum absorbance at the annealing temperature of 500 and 600°C. The film annealed at 500°C has a good thermal stability, wherein SiO₂ in the nanocomposites is amorphous. Ag nanoparticles get diffusing and volatilizing with increasing the temperature to 700°C and the annealing time increases, at the same time, SiO₂ particles transform into crystalloid from noncrystal.