Optical Properties and Excited-State Dynamics of Atomically Precise Gold Nanoclusters

Understanding the excited-state dynamics of nanomaterials is essential to their applications in photoenergy storage and conversion. This review summarizes recent progress in the excited-state dynamics of atomically precise gold (Au) nanoclusters (NCs). We first discuss the electronic structure and typical relaxation pathways of Au NCs from subpicoseconds to microseconds. Unlike plasmonic Au nanoparticles, in which collective electron excitation dominates, Au NCs show single-electron transitions and molecule-like exciton dynamics. The size-, shape-, structure-, and composition-dependent dynamics in Au NCs are further discussed in detail. For small-sized AuNCs, strong quantum confinement effects give rise to relaxation dynamics that is significantly dependent on atomic packing, shape, and heteroatom doping. For relatively larger-sized Au NCs, strong size dependence can be observed in exciton and electron dynamics. We also discuss the origin of coherent oscillations and their roles in excited-state relaxation. Finally, we provide our perspective on future directions in this area.