Gold nanoclusters (NCs) have been widely used in bioimaging and cancer therapy due to their unique electronic structures and tunable luminescence. However, their weak fluorescence prevents potential biomedical application, and thus it is necessary to develop an effective route to enhance the fluorescence of gold NCs. In this work, we report the fluorescence enhancement of ultrasmall GSHprotected Au NCs by Zn atom doping. The fluorescence signal of Zn-doped Au NCs shows approximately 5-fold enhancement compared to pure Au NCs. Density functional theory (DFT) calculation shows that Zn doping can enhance the electronic states of the highest occupied molecular orbital (HOMO), leading to enhancement of visible optical transitions. In vitro experiments show that AuZn alloy NCs can enhance the cancer radiotherapy via producing reactive oxygen species (ROS) and don't cause significant cytotoxicity. In vivo imaging indicates AuZn alloy NCs have significant passive targeting capability with high tumor uptake. Moreover, nearly 80% of GSH-protected AuZn alloy NCs can be rapidly eliminated via urine excretion.

Metal nanoclusters (NCs) have attracted much attention due to their unique properties. Silver (Ag) NCs are potential candidates for fluorescence bioimaging, but poor fluorescence of Ag NCs hinders their potential application. Atomic doping provides a feasible route toward improving the brightness of the clusters, but is limited to water-insoluble systems. Herein, we successfully enhance the fluorescence property of water-soluble Ag NCs by doping Au using a reduction method with dihydrolipoic acid as the ligand. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy proved that Au was successfully doped into Ag NCs by forming bimetallic NCs. The optical properties were analyzed using ultraviolet–visible absorption, photoluminescence, and time-resolved fluorescence spectroscopy. The results indicated that the Ag NCs with 10% Au doping content (AgAu NCs) had an 11-time increase in quantum yield compared to pure Ag NCs. Meanwhile, the sample shows good photostability for 30 min.