Probing the chemical environment of 3-hydroxyflavone doped ormosils by a spectroscopic study of excited state intramolecular proton transfer

The spectroscopic properties of 3-hydroxyflavone (3-HF) molecules entrapped in films and in monoliths of sol-gel derived organically modified silicates (Ormosils) xerogels are studied by excitation and fluorescence spectroscopy as a function of the sol-gel precursors used for the synthesis. Different molar ratios of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and phenyltriethoxysilane (PTES) as precursors are used for the sol preparation. Emission and excitation spectra in the ultraviolet-visible range and photo-degradation curves as a function of time are collected with a spectrofluorimeter. The 3-hydroxyflavone optical properties change in the different networks, owing to the effects of the chemical environment on the excited state intramolecular proton transfer and to the solubility of the dye molecules in the different sol-gel systems. It turns out that the spectroscopic features can be used to probe the chemical state of the dye molecules microenvironment. (C) 2003 Elsevier B.V. All rights reserved.