Origins of Visible and Near-Infrared Emissions in [Au25(SR)18]− Nanoclusters

The origin of photoluminescence in [Au25(SR)18]− nanoclusters remains elusive, and there is not a universal model that can well explain the experimental result. Here, we design Au25 nanoclusters protected by four different types of ligands for investigation of the photoluminescence mechanism by looking into the visible to near-infrared emissions. On the basis of time-resolved emission and nanosecond transient absorption spectroscopy analyses, we propose a model that can well explain the emission bands of Au25 nanoclusters. The visible and near-infrared emissions have different lifetimes and are found to arise from the core–shell charge transfer state and the Au13 core state, respectively. The obtained insight will help to understand how the excited state deactivates and to further engineer the photoluminescence of metal nanoclusters.