<title>Probing the structural development of dip-coated silica sol-gel thin films via fluorescent probe molecules</title>

Structural formation of dip-coated silica sol-gel thin films is monitored in situ via fluorescence depolarization with luminescent probe molecules. Pyranine (trisodium 8-hydroxy- 1,2,6-pyrenetrisulfonate) and prodan [6-propionyl-2- (dimethylamino)naphthalene] are chosen as the probe molecules for these experiments and are dissolved into the sol gel solution in millimolar quantities. This provides sufficient luminescence intensity without interfering with the film drying process. Fluorescence depolarization yields results which directly correlate to microviscosity increases as the film progresses from liquid to solid. These results allow for further quantitative support of a model previously presented concerning the formation of sol-gel thin films.