Thermally-activated delayed fluorescence from biocompatible, solid-state gold nanoclusters embedded into ionic-crystal matrices

Abstract The optical materials showing thermally-activated delayed fluorescence (TADF), have been considered to be promising light emitters for developing high-efficiency light-emitting devices due to their unique capability of harvesting both singlet and triplet states. Biocompatible gold nanoclusters (AuNCs) also exhibit TADF in the pristine aqueous solution. It would be useful by further exploiting TADF emission in the solid state for novel bio-friendly light-emitting materials. To this end, here, a facile, low-cost but effective method was used to generate stable and enhanced TADF emission in the solid state under ambient conditions by embedding biocompatible AuNCs into inorganic salt matrices. Temperature-dependent transient photoluminescence (PL) measurements were used to investigate TADF behavior of AuNCs embedded into the solid matrices. As compared with AuNCs in an aqueous solution, the TADF was enhanced for solid AuNCs even under ambient environment. In addition, by using waterproof salt matrices with polymer encapsulants, stable and broadband emission was demonstrated based on all biocompatible nanomaterials under UV-light illumination.