Exploration of fluorescence properties of gold nanoclusters at the single-molecule levels

Single-molecule spectroscopy (SMS) is a powerful and versatile technique that can be utilized to unravel the bio-molecule dynamics and to sense specific bio-molecules with extremely high sensitivity. A key requirement for successfully performing SMS is to incorporate suitable reporters/sensors. When the target molecules interact with them, the signals (such as fluorescence intensity/lifetime) can be changed accordingly. These reporters should be small enough, bio-compatible, non-toxic, and optically stable. Newly emerged fluorescent gold nanoclusters (Au NCs) have been demonstrated to be promising reporters in terms of aforementioned factors. In this work, we will explore their fluorescence properties from the single-molecule viewpoints by using novel fluorescence lifetime correlation spectroscopy. By which, the triplet state dynamics and diffusion process can be observed and the relevant time constant was derived. This work paves a way to use their single-particle fluorescence properties, such as fluorescence lifetime or triplet state dynamics for high-sensitivity bio-sensing in the future.