Photoinduced electron transfer between molecules in silica matrices

Abstract

The reactions of electron transfer between anthracene (An), pyrene (Py) and fluorescence quenchers N,N-dimethylaniline (DMA), N,N-diethylaniline (DEA) and Cu2+ ions in heterogeneous systems on the basis of silica under the conditions of differing mobilities of molecules and changes of carrier structure have been studied. Quenching of An* and Py* by DEA and DMA on adsorption from hexane on the surface of pyrogenic nonporous silica-aerosil is accompanied by exciplex formation and concentrational dependence of the rate constant of quenching. Fluorescence of solubilized Py is quenched very strongly by adding DMA in adsorbed TX-100 micelles. Removal of water sharply changes the photonics of the system. Intensity of Py fluorescence remains high and no quenching occurs. Py molecules are encapsulated in the SiO2 between layers of hydrophobic parts of TX-100. Photoinduced electron transfer between Py* and Cu2+ is effective at the stage of sol-gel transition in tetraethoxysilane (TEOS) hydrolysis reaction. Py molecules trapped in porous sol-gel phases are shown to undergo photoinduced electron transfer with Cu2+ when the liquid phase is present inside the pores.