PREPARATION AND CHARACTERIZATION OF AQUEOUS SILICA-BASED COLLOIDAL COMPOSITES CONTAINING IMMOBILIZED ORGANOMETALLIC PHOTOSENSITIZERS

Aqueous colloidal silica suspensions modified by incorporation of tris (2,2'-bipyridyl)ruthenium(II) and zinc(II) tetrakis(N-methyl-4-pyridyl )porphyrin into the particle matrix were prepared. The photophysical p roperties of the complexes in this environment were investigated using laser flash photolysis and steady-state luminescence techniques. The excited states exhibit nonexponential kinetics and their lifetimes are increased compared to homogeneous aqueous solutions. The metal-to-lig and charge transfer state of the Ru(II) complex is not affected by the presence of dissolved oxygen, whereas a fraction of the triplet state s of the porphyrin is quenched by O-2. Didodecyldimethylammonium ion w as used to build surfactant bilayers supported on the silica surface. The possibility of using this system for transmembrane electron transf er is discussed.