Fluorescence probing of composite organic/inorganic transparent matrices

Transparent composite SiO2/organic matrices have been made by the sol-gel m ethod using tetramethoxysilane and either cetyltrimethylammoniumbromide (CT AB) or a polyethylene glycol oligomer (PEG-200) or a cationic polyelectroly te. We have investigated conditions under which transparent xerogel matrice s are possible and we have characterized them mainly by time-resolved fluor escence probing using stretched exponentials. CTAB creates a hydrophobic an d PEG-200 a hydrophilic subphase in the matrix. An important property of th ese composite matrices is that they allow molecular diffusion contrary to m atrices made in the absence of surfactants or polymers.