Metal clusters have attracted wide interests due to their unique electronic and optical properties, but the low luminescence quantum yield (QY) prevents them from potential biomedical applications. In this work, silver-doped Au nanoclusters (NCs) are shown to be able to improve the QY of metal clusters. We succeeded in synthesizing ultrabright glutathione (GSH) protected AuAg clusters with 10.8% QY by a one-pot route. Their florescence is about 7.5 times brighter than pure Au NCs, with super photostability and good biocompatibility in physiological environment. Based on density functional theory (DFT) calculations, we investigated the electronic structures and optical properties of the AuAg NCs. The results show that the increase of the density of states of the lowest unoccupied molecular orbital (LUMO) leads to the fluorescence enhancement. In addition, two-photon excitation fluorescence imaging has been performed to show their great potential for biomedicine.

中文翻译：

---

超亮双金属 AuAg 配合物：从发光机制到生物应用

金属簇因其独特的电子和光学特性而引起了广泛的兴趣，但低发光量子产率 (QY) 阻碍了它们潜在的生物医学应用。在这项工作中，银掺杂的金纳米团簇（NCs）被证明能够改善金属团簇的 QY。我们通过一锅法成功合成了 10.8% QY 的超亮谷胱甘肽 (GSH) 保护的 AuAg 簇。它们的荧光比纯Au NCs亮约7.5倍，在生理环境中具有超强的光稳定性和良好的生物相容性。基于密度泛函理论 (DFT) 计算，我们研究了 AuAg NCs 的电子结构和光学性质。结果表明，最低未占分子轨道（LUMO）的态密度增加导致荧光增强。