Observation of Singlet Oxygen with Single-Molecule Photosensitization by Time-Dependent Photon Statistics.

The singlet oxygen has been widely applied to the treatment of physiological diseases, and the photosensitized generation of singlet oxygen is the main means of its physiological applications. On the basis of the fluctuation of fluorescence field from single photosensitizer, we characterize the generation of singlet oxygen at single molecule level with the time-dependent photon statistical method. By measuring the time-tagged-time-resolved single-molecule fluorescence photons, we analyze the time-dependent Mandel-Q parameter, which has been performed at different oxygen environment. It is shown that the single molecule not only offers an efficient way of generating singlet oxygen in ambient condition but also provides insights for the fluctuation of singlet oxygen in the nanoscale environment. The method of time-dependent photon statistics provides a convenient methodology for observing photosensitizers generating singlet oxygen in real time at single photosensitizer level.