Atomic-Level Engineering of Au-Ag Nanoclusters Enables Divergent Triplet Emission

Triplet-state-based luminescence holds great promise for next-generation optoelectronic materials, yet its mechanistic modulation through structural control remains a fundamental challenge for nanomaterials. Here, we present a comparative study of two atomically precise nanoclusters, Au₆Ag₂ and Au₆Ag₄, which feature an identical Au₆ core but differ subtly in Ag atom count and ligand coordination. Despite their structural similarity and triplet dominated emission origin, the results herein reveal that Au₆Ag₂ exhibits phosphorescence, whereas Au₆Ag₄ demonstrates dual emission involving both phosphorescence and thermally activated delayed fluorescence (TADF). The contrasting behaviors arise from fine-tuning the silver contents and organic ligands, which alters photoluminescence nature without modifying the metal core. This work highlights a structure-driven approach to regulating triplet-state photoluminescence in metal nanoclusters and offers a blueprint for designing next-generation triplet-emissive materials.