Structurally Resolved Water-Soluble Copper Nanoclusters with NIR TADF Exhibiting Multifunctional Catalytic Activity

Thermally activated delayed fluorescence (TADF) in metal nanoclusters (MNCs) is an effective strategy to harvest the emission from the excited-triplet states. However, the applications of these TADF-active MNCs are limited by the use of hydrophobic ligands, which generally make these MNCs insoluble. Herein, we report the NIR-TADF emitting CuNCs that are highly water-soluble and display intense-red emission in the solid state. The atomic connectivity of the CuNCs was determined by SC-XRD technique. The delayed fluorescence phenomenon is validated by temperature-dependent photoluminescence studies, and the excited singlet-triplet energy gap (ΔE_ST) was experimentally estimated to be ∼98 meV, thereby substantiating the TADF mechanism. DFT calculations performed on the crystal geometry of the CuNCs further attested to the TADF mechanism along with the associated charge-transfer dynamics. Additionally, the CuNCs demonstrate excellent catalytic activity involving the reduction of ferricyanide and Methylene Blue, highlighting their multifunctional applications in the aqueous phase.