Room temperature phosphorescence of aromatic hydrocarbons in aqueous micellar solutions

Abstract

The phosphoresence spectra of several simple arenas, pyrene, naphthalene, biphenyl and their brominated derivatives have been observed in aqueous micellar solutions at room temperature. The success of these experiments is due to the protective screening of the arene triplet state by solubilization in the micelles. Impurities in the aqueous phase are thus excluded from the excited arene. Small traces of oxygen efficiently remove the phosphorescence as oxygen readily penetrates into the micelle to quench the arene triplet. Hydrophilic quenchers such as Cu 2+ and Tl + also reduce the lifetime of the phosphorescence. In anionic micelles these quenchers are located at the surface of the micelle and efficient quenching take place at the lipid water interface. Cupric ions reduce the lifetime and yield of phosphorescence, while Tl + ions reduce the lifetime but also enhance the rate of emission of the phosphorescence via heavy atom spin orbit coupling. The technique and data are relevant to the measurement of kinetic parameters in micelles and membranes.