Fluorescence–Phosphorescence Manipulation and Atom Probe Observation of Fully Inorganic Silver Quantum Clusters: Imitating from and Behaving beyond Organic Hosts

Abstract Silver quantum clusters (Ag QCs) have attracted great attention due to their unique electronic structure and molecule‐like photoluminescence (PL). Applications in catalysis, biology, and optoelectronics have already been realized, however, the understanding of PL mechanism and direct observation of Ag QCs still remain challenging. Here, fully inorganic Ag QCs well stabilized in the borate glass with simultaneous excellent chemical stability, tunable PL emission, and high quantum yield are prepared. And the PL properties of Ag QCs respond drastically to changes of the embedding environment, displaying pronounced fluorescence to phosphorescence (F‐P) switching. Combining the structural and spectral analysis, it is found that the F‐P switching is triggered by the Ag QCs aggregation and [BO 3 ]→[BO 4 ] − conversion of the borate network. Using atom probe tomography enables to quantitatively characterize the evolution of Ag QCs at an atomic level, which reveals that Ag QCs consisting of less than 20 atoms are responsible for the observed PL.