A Single Model for the Excited-State Dynamics of Au₁₈(SR)₁₄ and Au₂₅(SR)₁₈ Clusters

Excited-state properties of photonic materials play an important part in dictating the photocatalytic activity. Thiol-protected gold clusters, like Au18(SR)14 and Au25(SR)18, are an emerging material of interest with unique optical and electronic properties. Au18(SR)14 clusters, in particular, have shown promise as one of the highest efficiency clusters in light harvesting, with a high emission quantum yield. In this work, the excited-state properties of Au18(SR)14 are studied in-depth by ultrafast pump/probe spectroscopy for the first time. A single model describing the optical characteristics of thiol-protected Au18(SR)14 and Au25(SR)18 clusters is offered. Excited-state dynamics analysis suggests that there are state-resolved relaxations due to the presence of multiple excited states. The populations of these excited states are shown to be solvent- and ligand-dependent