Generalizable Organic-to-Aqueous Phase Transfer of a Au18 Nanocluster with Luminescence Enhancement and Robust Photocatalysis in Water

Abstract

For the majority of gold nanoclusters (NCs), their water insolubility, low photoluminescence (PL) intensity, and less understood photostability are three critical factors that limit their application in the biomedical and photocatalysis fields. In this study, we report a polymer wrapping method for phase transfer of organic soluble NCs into aqueous phase without degrading the electronic and optical properties, and such materials are further demonstrated for robust photocatalysis in water. We first synthesized a Au₁₈(DMBT)₁₄ NC (DMBT = 2,4-dimethylbenzenethiolate) and found that the aromatic ligands confer a greatly enhanced antioxidation capability of the NC compared to the Au₁₈(CHT)₁₄ counterpart (CHT = cyclohexanethiolate), with the critical role of aromatic ligand interactions identified by X-ray crystallography. The organic soluble Au₁₈(DMBT)₁₄ was successfully transferred into the aqueous phase by an amphiphilic polymer (Pluronic F127, abbrev. F127) wrapping method, producing Au₁₈-D@F127 nanoparticles [each containing a few NCs; Au₁₈-D is an abbreviation for Au₁₈(DMBT)₁₄] with a 10-fold enhancement in PL intensity, and similar results were also obtained for Au₁₈(CHT)₁₄. This method is broadly applicable to various NCs, rendering their water solubility and significantly enhancing the PL intensity of otherwise weakly emissive gold NCs. The exceptional antioxidation stability of Au₁₈(DMBT)₁₄ enables the application of Au₁₈-D@F127 NPs for the photocatalytic activation of persulfate ions and subsequent photodegradation of water pollutants efficiently.