Fluorescence enhancement of water-soluble silver nanoclusters via Au doping

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.