Gold-Doping Effect on Two-Photon Absorption and Luminescence of Atomically Precise Silver Ligated Nanoclusters

Noble metal nanoclusters allow for the atomically-precise control of their composition. However, to create nanoclusters with pre-defined optical properties, comprehensive description of their structure-property relation is required. Here, we report the gold atom doping impact on one-photon and two-photon absorption (TPA) and luminescence properties of ligated silver nanoclusters via combined experimental studies and time-dependent density functional theory simulations (TD-DFT). We synthesized a series of Ag_25-x Au_x (DMBT)₁₈ nanoclusters where x=0, 1 and 5-10. For Ag₂₄ Au₁ (DMBT)₁₈ we demonstrate that the presence of the central Au dopant strongly influences linear and non-linear optical properties, increasing photoluminescence quantum yield and two-photon brightness, with respect to undoped silver nanoclusters. With improved TPA and luminescence, atomically-precise AuAg alloys presented in our work can serve as robust luminescent probes e.g. for bioimaging in the second biological window.