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

Optically transparent nanocrystalline CdS doped silica xerogels are prepare d in the presence of pyridinic poly(methyl methacrylate) (PMMA) organic pol ymer. The PMMA/SiO2 weight ratio was varied from 0 to 0.04 by keeping the C dS/SiO2 weight ratio at 0.005 and it was found that there was drastic decre ase in the gelation time of alcogels from 10 days to 1 day whereas the perc entage of optical transmission of the alcogels decreased from 80 to 30%, re spectively. It was found that the thermal stability of the PMMA doped nanoc rystalline CdS xerogels was decreased from 280 to 220 degreesC with the inc rease of PMMA/SiO2 weight ratio from 0.004 to 0.04. When PMMA doped nanocry stalline CdS doped silica xerogels were heated at 300 degreesC for 3 h, the percentage of weight loss increased from 7 to 35% and density decreased fr om 1.8 to 1.25 g cm(-3) with an increase of PMMA/SiO2 weight ratio from 0 t o 0.04, respectively. From the optical absorption and X-ray diffraction stu dies, 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, respec tively. In the case of TR spectral studies it was found that there is no ch ange either in the CdS or SiO2 bond peaks with the addition of PMMA to the nanocrystalline CdS silica xerogels. (C) 2001 Elsevier Science B.V. All rig hts reserved.