FLUORESCENCE OF PYRENE IN SOL-GEL SILICA DERIVED FROM TRIETHOXYSILANE

The fluorescence of pyrene probe molecules was measured in a sol-gel reaction system of triethoxysilane (HTEOS)/tetraethoxysilane (TEOS). There was minimal change in the ratio of the intensity of the third peak to the first peak (I3/I1) for the fluorescence spectra in the starting sol-gel solutions for various mixtures of HTEOS and TEOS. On the contrary, I3/I1 in silica xerogels increased linearly as HTEOS increased. These results indicate that the solvent composition mainly determines the environmental polarity of pyrene probes in initial solutions, while the HTEOS composition determines the polarity in xerogels, and that those silica xerogels derived from HTEOS are hydrophobic. The infrared spectra of these xerogels suggests that the hydrophobic character of the xerogels derived from HTEOS is largely ascribed to the reduction of Si-OH groups and adsorbed water molecules on these groups.