Theoretical Insights on the Regulatory Mechanisms of Structure and Doping on the Photoluminescence of Ligand Protected Gold Nanoclusters

ConspectusLigand-protected gold nanoclusters (Au NCs) occupy a unique region between molecules and bulk metals, garnering significant attention due to their atomically precise structure and size- and structure-dependent optical properties. Notably, their tunable emission characteristics, excellent photostability, and biocompatibility make them promising candidates for bioimaging, sensing, and optoelectronic applications. However, the relatively low photoluminescence quantum yield (PLQY) of most Au NCs hinders their practical application. Furthermore, the low PLQY of Au NCs is closely associated with their complex excited-state dynamics: the interactions between the metal core and ligand shell, coupled with the strong spin-orbit coupling (SOC) effect, collectively induce diverse excited-state relaxation pathways, which render the regulatory mechanism of photoluminescence (PL) difficult to decipher precisely.This Account summarizes recent theoretical insights into the PL mechanisms of ligand-protected gold and other coinage metal (Ag and Cu) nanoclusters. We systematically examine how fundamental structural factors, such as core-shell structure, isomer effects, size, and heteroatom doping, modulate the respective radiative and nonradiative decay channels that determine the clusters' PL properties. In addition, nonadiabatic molecular dynamics (NA-MD) simulations incorporating many-body (MB) treatment of electronic excited states yields relaxation time scales in better agreement with experiments. Finally, we introduce application of a graph convolutional neural network (GCNN) for the rapid and accurate prediction of UV-vis absorption spectra, demonstrating the potential of machine learning in this field. Collectively, these insights establish key principles: size and symmetry dictate radiative rates, ligand rigidity suppresses nonradiative decay, and heteroatom doping provides a flexible handle to tune excited-state pathways. Moving forward, integrating NA-MD with data-driven approaches will be critical for bridging atomic-scale structures with macroscopic optical performance. These advances are essential for the rational design of highly efficient luminescent clusters in light harvesting, optoelectronics, and biomedical applications.