Study of silica-surfactant composite films with fluorescent probes

A nanostructured layered composite film has been obtained by dip-coating in a sol containing tetramethoxysilane, water, and surfactant. Two surfactants have been tried: Cetyltrimethylammonium bromide and Triton X-100. The film was studied by analyzing the absorption and fluorescence spectra of Coumarin-153, the fluorescence spectra of Pyrene, and the time-resolved direct-energy-transfer data between pyrene and Coumarin-153. These probes are solubilized in a surfactant bilayer sandwiched between two silica layers, and they lie close to the interface. They detect a very rigid, closely packed, highly oriented structure, The geometry of energy transfer is isotropic at sufficiently high probe concentration, indicating an orderly distribution of probes. The data are compatible with a model proposed by Ogawa (J. Am, Chem. See. 1994, 116, 7941).