Thermally Induced Supramolecular Polymorphism Strategy Enables Fabrication of Emissive Tunable Gold Nanoclusters...

Developing controllable multicolor emissive materials is highly desirable in the field of optical devices. However, the efficient strategies to achieve this from a single gold nanoclusters (AuNCs) are still scarce. Herein, we harness a thermally induced supramolecular polymorphism strategy to get distinct nanostructures with wide-range tunable emissions in the case of thiosalicylic acid (TSA) protected AuNCs and Zn²⁺ co-assembly system by introducing excess TSA molecules. In detail, nanospheres (Agg I) with yellow luminescence were obtained at 298 K, which converted into nanofibers (Agg II) with abnormally enhanced red emission upon thermal treatment at 358 K. This phenomenon is significantly different from conventional co-assembly systems, where heating typically promotes the dissociation of aggregates accompanied by emission quenching. Mechanistic studies reveal that the coordination of Zn²⁺ simultaneously with AuNCs and excess TSA molecules leads to the formation of kinetically trapped Agg I, while heating facilitates the molecular rearrangement, and aurophilic interaction results in thermodynamically controlled Agg II with ordered arrangement. Notably, the evolution process could be precisely controlled by ligand quantity, AuNCs concentration, and temperature. The programmable fluorescence and unprecedented thermochromic behavior enable them to have potential applications in complex information encryption and deepen the understanding of the aggregation structure-luminescence property relationship of AuNCs.