Impact of Annealing Temperature and Silver Concentration on the Formation of Silver Nanoparticles in Silica

Abstract

The optical and structural properties of silica doped with silver were investigated in detail at various annealing temperatures (from 500 °C up to 1300 °C) and silver concentration (from 0.1 - 5 mol%). To investigate the effects of Ag concentration and annealing temperature on the formation of silver nanoparticles, complementary techniques were used namely ultraviolet-visible spectrometer (UV-VIS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained results showed that the crystalline phase of silver did not form in samples annealed below 800 °C while for annealing temperature above 1000 °C the amount of silver is reduced by evaporation. This indicates that the optimum annealing temperature is in between 800 °C-1000 °C. It is also revealed that the size of silver nanoparticles is increases with increasing the annealing temperature while increasing of Ag concentration had no significant effect on the particle size. It is also found that the peak intensity of the XRD pattern related to silver was increases as function of silver loads up to 1mol% and then decreased, indicating that the optimum concentration of silver is about 1mol%. On the other hand, it is found that the increasing of Ag loads in silica is catalyzed the structure order of amorphous silica towards the cristobalite phase.