Probing the Sol–Gel Conversion in the Tetraethoxysilane/Alcohol/Water System with the Aid of Diffusion-Controlled Fluorescence Quenching
✍ Scribed by T.A. Kikteva; B.V. Zhmud; N.P. Smirnova; A.M. Eremenko; Yu. Polevaya; M. Ottolenghi
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 119 KB
- Volume
- 193
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
of ortho-phenanthrolyne, which is known to form stable che-The sol-gel conversion in the tetraethoxysilane/alcohol/water late complexes with the aforesaid ions, the ESR spectra can system can be probed by means of the diffusion-controlled fluores-''sense'' the moment that the sol-gel conversion occurs. cence quenching of Py* by Cu 2/ ions. In the course of tetraethoxy-The use of the word ''moment'' here is justified in view of silane hydrolysis, the viscosity of the system increases, thereby the fact that the duration of sol-gel transformation is norcausing the quenching rate to decrease and the mean lifetime of mally many orders of magnitude shorter than the duration the excited state to elongate dramatically as the system approaches of the initiation stage, as well as the stage of gel ripening. the gel-point. Incorporating the equation proposed by Vogels-It has also been reported that the sol-gel conversion in the berger et al. (1992) for the time-dependence of the viscosity of TEOS/alcohol/water system can be detected by the change gelating systems into the Smoluchowsky kinetic equation, an equation has been proposed to describe the observed time-dependence in the fluorescence spectra of 7-azoindol (14) and by inverof the Py* lifetime. ᭧ 1997 Academic Press sion of the fluorescent level of 1-naphthol (15). The early Key Words: fluorescent probes; quenching kinetics; sol-gel constage of the process has been monitored by means of the version.
proton transfer reaction between water molecules and a pyranine probe added to the system (16).
Molecular probes, at least when present in trace amounts, have an advantage in that they permit the monitoring of