Physical characteristics of heat-treated nano-silvers dispersed in sol–gel silicamatrix

Abstract

Silica films containing various concentrations of Ag nanoparticles were deposited on glass slidesusing a sol–gel process and then heat-treated in air at different temperatures. The filmswere analysed by using UV–visible spectrophotometry, atomic force microscopy (AFM),scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-rayphotoelectron spectroscopy (XPS) for their optical, surface morphological as well as structural,and chemical properties. After heat-treatment, the optical absorption peaks of Agnanoparticles show a blueshift and an intensity reduction due to particle size reduction andAgOx nanoparticle formation, respectively. The particle size reduction and surface morphologychanges in the films were observed by AFM and TEM as a function of heat-treatmenttemperature and Ag concentration. Using AFM and XPS analyses, we have found that theAg nanoparticles accumulated on the surface diffuse into the substrate as theheat-treatment temperature increases. XPS analysis also showed that the silver oxidationoccurs during the heat-treatment, causing the reduction of absorption intensity. Bycontrolling the Ag concentration and the heat-treatment temperature, we could change thesilica structure, and tailor the average size of the silver nanoparticles down to less than4 nm.