Thermally activated delayed fluorescence Au-Ag-oxo nanoclusters: From photoluminescence to radioluminescence

Thermally activated delayed fluorescence (TADF) materials have numerous applications in energy conversion and luminescent imaging. However, they are typically achieved as metal-organic complexes or pure organic molecules. Herein, we report the largest Au-Ag-oxo nanoclusters to date, Au18Ag26(R1COO)12(R2C equivalent to C)24(mu 4-O)2(mu 3-O)2 (Au18Ag26, where R1 = CH3-, Ph-, CHOPh- or CF3Ph-; R2 = Ph- or FPh-). These nanoclusters exhibit exceptional TADF properties, including a small S1-T1 energy gap of 55.5 meV, a high absolute photoluminescence quantum yield of 86.7%, and a microseconds TADF decay time of 1.6 mu s at ambient temperature. Meanwhile, Au18Ag26 shows outstanding stability against oxygen quenching and ambient conditions. Atomic level analysis reveals the strong pi MIDLINE HORIZONTAL ELLIPSIS pi and C-HMIDLINE HORIZONTAL ELLIPSIS pi interactions from the aromatic alkynyl ligands and the enhancement of metal-oxygen-metal interactions by centrally coordinated O2-. Modeling of the electronic structure shows spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital, which promote charge transfer from the ligand shell, predominantly carboxylate ligands, to O2--embedded metal core. Furthermore, TADF Au-Ag-oxo nanoclusters exhibit promising radioluminescence properties, which we demonstrate for X-ray imaging. Our work paves the way for the design of TADF materials based on large metal nanoclusters for light-emission and radioluminescence applications. Au18Ag26 nanoclusters are the largest Au-Ag-oxo nanoclusters reported to date, showcasing remarkable TADF characteristics. Strong pi MIDLINE HORIZONTAL ELLIPSIS pi interactions from aromatic alkynyl ligands and O2--induced metal aggregation contribute to their outstanding photoluminescence. They display an 86% quantum yield and microsecond-scale lifetime, alongside exceptional stability in oxygen-rich environments. Our study unveils molecular interactions and electronic structure, offering insights for X-ray imaging applications.dagger double dagger image