Effect of poly(methyl methacrylate) on the physical properties of quantized CdS doped silica xerogels

Optically transparent nanocrystalline CdS doped silica xerogels are prepared in the presence of pyridinic poly(methyl methacrylate) (PMMA) organic polymer. The PMMA/SiO2 weight ratio was varied from 0 to 0.04 by keeping the CdS/SiO2 weight ratio at 0.005 and it was found that there was drastic decrease in the gelation time of alcogels from 10 days to 1 day whereas the percentage of optical transmission of the alcogels decreased from 80 to 30%, respectively. It was found that the thermal stability of the PMMA doped nanocrystalline CdS xerogels was decreased from 280 to 220°C with the increase of PMMA/SiO2 weight ratio from 0.004 to 0.04. When PMMA doped nanocrystalline CdS doped silica xerogels were heated at 300°C for 3 h, the percentage of weight loss increased from 7 to 35% and density decreased from 1.8 to 1.25 g cm−3 with an increase of PMMA/SiO2 weight ratio from 0 to 0.04, respectively. From the optical absorption and X-ray diffraction studies, it was found that there was an increase in crystalline size from 2 to 3.3 nm with the variation of PMMA/SiO2 weight ratio from 0 to 0.04, respectively. In the case of IR spectral studies it was found that there is no change either in the CdS or SiO2 bond peaks with the addition of PMMA to the nanocrystalline CdS silica xerogels.