Detection and lifetime measurement of single molecules in flowing sample streams by laser-induced fluorescence

Abstract

The detection and measurement of fluorescence lifetimes of single Rhodamine‐110 molecules in a flowing, aqueous sample stream is described. Time‐correlated single‐photon counting, used in combination with mode‐locked picosecond pulsed excitation, allows the detection of single fluorescent molecules in the presence of significant solvent Raman and Rayleigh backgrounds. The fluorescence lifetime of a detected molecule is estimated from the record of arrival times (relative to the excitation pulse) of photons detected during the molecule’s passage through the ∼1 pL excitation volume.