Probing the Sol-Gel Conversion in the Tetraethoxysilane/Alcohol/Water System with the Aid of Diffusion-Controlled Fluorescence Quenching.

The sol-gel conversion in the tetraethoxysilane/alcohol/water system can be probed by means of the diffusion-controlled fluorescence quenching of Py* by Cu2+ ions. In the course of tetraethoxysilane hydrolysis, the viscosity of the system increases, thereby causing the quenching rate to decrease and the mean lifetime of the excited state to elongate dramatically as the system approaches the gel-point. Incorporating the equation proposed by Vogelsberger et al.