Probing the Fluorescence Intermittency of Bimetallic Nanoclusters using Single-Molecule Fluorescence Spectroscopy.

Single-molecule spectroscopy (SMS) is a unique and competent technique to study molecule dynamics and sense biomolecules precisely. The design of an ultrahigh-stability single fluorophore probe with excellent photostability and long-lived dark transient states for single-molecule fluorescence microscopy is challenging. Here, we found that the photostability of bimetallic AuAg 28 nanoclusters is better than monometallic Ag 29 nanoclusters. The photon antibunching experiments unveiled exceptional brightness and remarkable photostability with high survival times of up to 218 s with minimal blinking. AuAg 28 NCs exhibited longer "on" times and shorter "off" times as compared to Ag 29 NCs. The statistical analysis was performed on at least 100 molecules that showed single-step photobleaching and almost a 5-fold enhancement in intensity on Au doping in Ag 29 NCs. The distinctive and tunable photophysics of metal NCs can offer huge potential in pushing single-molecule dynamic measurements to be carried out biologically.