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.