FLUORESCENCE AND INFRARED-SPECTRA OF PHENYL-MODIFIED SILICA-GELS PREPARED BY THE SOL-GEL PROCESS

Phenyl-modified silica gels were derived from a mixture of triethoxy ( phenyl) silane and tetraethoxysilane. The fluorescence spectra and lif etime of pyrene were measured in silica gels. The fluorescence spectra and lifetime changed with an increase In phenyl content and became co nstant above approximate to 20 mol% of triethoxy (phenyl)silane. The f luorescence band of phenyl groups also showed a change from a monomer one to an excimer one above approximate to 20 mol% of phenyltriethoxys ilane. Similarly the vibrational frequencies of infrared bands due to the siloxane network were shifted above approximate to 20 mol%. These results were explained by the structural changes of phenyl-modified si lica gels induced by the bulky phenyl groups.