Photophysical properties of organic fluorescent probes on nanosized TIO2/SIO2 systems prepared by the sol-gel method

Highly transparent TiO2 and TiO2/SiO2 films prepared using the sol-gel technique have been studied by means of fluorescence probes method. Electronic interactions between adsorbed species-pyrene and donor-acceptor substituted push-pull stilbene-and Ti-doped silica matrices have been studied by the methods of steady-state and momentary spectrofluorimetry. Organic molecules are strongly adsorbed on the TiO2 and Ti/Si surfaces. Increasing the Ti content within Ti/Si systems results in a decrease in the intensity of the photoluminescence spectra. These findings indicate that titania oxide species are highly dispersed within silica matrices, probably without aggregating each other, and adsorbed molecules are in direct contact with titanium ions located on the Ti/Si surface. The time scale of these decay processes is tens of nanoseconds. The fluorescence emission quenching can be attributed to the charge injection From the singlet excited state of the molecule to the conduction band of the semiconductor. (C) 2000 Elsevier Science B.V. All rights reserved.