Ultrabright Au@Cu(14) nanoclusters: 71.3% phosphorescence quantum yield in non-degassed solution at room temperature

The photoluminescence of metal nanoclusters is typically low, and phosphorescence emission is rare due to ultrafast free-electron dynamics and quenching by phonons. Here, we report an electronic engineering approach to achieving very high phosphorescence (quantum yield 71.3%) from a [Au@Cu(14)(SPh(t)Bu)(12)(PPh(C(2)H(4)CN)(2))(6)](+) nanocluster (abbreviated Au@Cu(14)) in non-degassed solution at room temperature. The structure of Au@Cu(14) has a single-Au-atom kernel, which is encapsulated by a rigid Cu(I) complex cage. This core-shell structure leads to highly efficient singlet-to-triplet intersystem crossing and suppression of nonradiative energy loss. Unlike the phosphorescent organic materials and organometallic complexes—which require de-aerated conditions due to severe quenching by air (i.e., O(2))—the phosphorescence from Au@Cu(14) is much less sensitive to air, which is important for lighting and biomedical applications.