Comparison between time-correlated single photon counting and fluorescence correlation spectroscopy in single molecule identification

Currently, two methods of detection and identification of single molecules are widely used: fluorescence correlation spectroscopy (FCS) and time-correlated single photon counting (TCSPC). We present a thorough theoretical analysis of the error rates for identifying single molecules according to their diffusion coefficients (using FCS), and to their fluorescence lifetimes (using TCSPC). In most cases, the error rate using TCSPC is much lower. TCSPC is thus proven to be more versatile for analyzing single molecule events. The study is significant for a broad range of ultra-sensitive fluorescence detection applications.