The concentration-dependent distribution of tris(4,7′-diphenyl-1, 10′- phenanthroline) ruthenium (II) within sol-gel-derived thin films

Abstract

Organic dye-doped glasses, viz., ruthenium (II) tris(4,7'-diphenyl-1,10'- phenanthroline) [Ru(dpp)3]2+ incorporated into thin silica xerogel films produced by the sol-gel method, were prepared and their O2 quenching properties investigated as a function of the [Ru(dpp) 3]2+ concentration (3-400 μM) within the xerogel. The ratio of the luminescence from the [Ru(dpp)3]2+-doped films in the presence of N2 and O2 (IN2/IO2) was used to describe the film sensitivity to O2 quenching. IN2/IO2 changed three-fold over the [Ru(dpp)3]2+ concentration range. Time-resolved intensity decay studies showed that there are two discrete [Ru(dpp)3]2+ populations within the xerogels (ô1 ~ 300 ns; ô2 ~ 3000 ns) whose relative fraction changes as the [Ru(dpp) 3]2+ concentration changes. The increased O2 sensitivity that is observed at the higher [Ru(dpp)3]2+ concentrations is a manifestation of a greater fraction of the 3000 ns [Ru(dpp)3]2+ species (more susceptible to O2 quenching). A model is presented to describe the observed response characteristics resulting from [Ru(dpp)3]2+ distribution within the xerogel.