Fluorescence enhancement of water-soluble silver nanoclusters via Au doping

Jing Chen,Xiao-Dong Zhang,Tianyu Liu,Yanqing Qiao,Yonghui Li

doi:10.1063/5.0029434

Abstract

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.

Highlights

Nanoparticles (NPs) bridge the gap between single molecules and bulk materials
In the UV–Vis absorption spectrum [Fig. 1(a)], three absorption peaks of undoped Ag NCs can be clearly seen at 325 nm, 425 nm, and 500 nm, respectively, FIG. 1. (a) UV–vis absorption spectra and (b) fluorescence emission spectra of AgAu NCs in aqueous solutions with excitation at different wavelengths (300 nm, 410 nm, 600 nm). (c) and (d) Photoluminescence (PL) spectra of AgAu NCs in aqueous solutions, synthesized with different initial molar ratios of Au doping
The results indicate that AgAu NCs have good photostability and can be applied in fluorescent imaging, biolabeling probes, and other fields

Summary

Introduction

Nanoparticles (NPs) bridge the gap between single molecules and bulk materials. NPs with a size less than 2 nm are called nanoclusters (NCs). A little variance in the size, shape, or components of NCs may lead to extraordinary differences in their physical and chemical properties. In general, metal NCs consist of a certain number of metallic atoms and ligands, ranging from a few to several hundreds. NPs with a size less than 2 nm are called nanoclusters (NCs).. NCs create a link between metal atoms and NPs.. In the synthesis process of metal NCs, stabilizers or coating media are usually required, which include organic substances such as thiols, amines, carboxyl groups, dendrimers, and biological macromolecules such as proteins, peptides, and nucleic acids. They can provide biocompatible surfaces for metal NCs. The small size, fluorescence, and non-toxicity cause the NCs to have great potential in biomedical applications, such as bioimaging, radiation therapy, disease diagnosis, and as nanocatalysts for in vivo electrochemical reactions.

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