Single molecule detection and photobleaching study of a phosphorescent dye: organometallic iridium(III) complex

We report results of single molecule study of phosphorescent organometallic complex, tris(2-phenylpyridine)-iridium (Ir(ppy)3). Single molecule emission intensities show a wide multi-component distribution. Photobleaching times of molecules emitting with particular intensity are exponentially distributed. The dependence of the inverse of the mean photobleaching time on the emission intensity reveals linear dependence for lower intensities and more complex behavior for higher intensities. The results obtained on Ir(ppy)3 are compared with those of a fluorescent label, diethyloxacarbocyanine.