Ultrabright Au@Cu₁₄ 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@Cu₁₄(SPh Bu)₁₂(PPh(C₂H₄CN)₂)₆]⁺ nanocluster (abbreviated Au@Cu ) in non-degassed solution at room temperature. The structure of Au@Cu 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., O₂)-the phosphorescence from Au@Cu is much less sensitive to air, which is important for lighting and biomedical applications.