Photoluminescence behavior of SiO2 prepared by sol-gel processing

kinds of SiO2 were prepared by the usual sol-gel process (heat-treated samp le) or a sol-gel process using photoirradiation (photoirradiated sample) an d their photoluminescence behaviors were investigated. All heat-treated sam ples had photoluminescence bands, but none of the photoirradiated samples d id. Intensity of emission of heat-treated sample increased as the treatment temperature increased. This photoluminescence behavior occurred reversibly with thermal treatment and photoirradiation. The network structure of SiO2 samples were evaluated by solid slate NMR. The intensity of O-17 solid sta te NMR peak increased with increased emission intensity. These results impl ied that heat-treated samples included some defects which showed photosensi tivity, but the photoirradiated samples lacked such defects and formed a ri gid network structure instead. These defects caused the observed photolumin escence. (C) 2000 Elsevier Science B.V. All rights reserved.