Photochemistry on surfaces

Abstract

The photophysics and photochemistry of organic molecules (aro- matics, aza-aromatics, diphenylpolyenes, azobenzene, triphenylmethane dyes, thioindigo) adsorbed on metal oxides (alumina, silica, thoria, ti-tania) were investigated by steady-state and time-resolved diffuse reflectance and luminescence spectroscopy. The fluorescence decay curves of almost all adsorbates are non-exponen-tial. This effect is discussed in terms of different polarizing surface sites, aggregation, and interference between directly emitted and scattered fluorescence radiation. A method is elaborated to determine rate constants and quantum yields of photoreactions in strongly scattering rigid media by photometric measurements using the model of radiative transfer. The method is applied to quantify internal and translational mobilities of adsorbed photoexcited molecules, ring closure reactions, bimolecular photoprocesses, and charge transfer between the adsorbent and the adsorbate. © 1986 IUPAC