Hydrothermal synthesis of novel photosensitive gold and silver bimetallic nanoclusters protected by adenosine monophosphate (AMP)

Abstract

Herein, a rapid and effective hydrothermal synthesis method was employed for the preparation of Au and Ag bimetallic nanoclusters protected by adenosine monophosphate (Au–AgNCs@AMP); the Au–AgNCs@AMP show large Stokes shift (∼200 nm) and strong luminescence emission with a high quantum yield (QY = 8.46%). Moreover, to the best of our knowledge, it is for the first time that the hydrothermal synthesis method has been employed to prepare bimetal nanoclusters protected by small molecules, which is a simple, easy-to-operate, one-pot, and time saving method. Through employing gold nanoclusters as seed and monitoring the preparation process, it can be understood that Au–AgNCs@AMP are formed with a core–shell structure, where gold atoms serve as the core and silver atoms are distributed on the surface as a shell. In addition, the Au–AgNCs@AMP show an obvious color change and turned from colorless to orange accompanied by a slight luminescence quenching upon exposure to sunlight; moreover, a new absorption peak appears between 400 and 500 nm, which gradually increases with the exposure time, and the mean particle size of the products also increases from 2.25 to 10.0 nm. The intrinsic mechanism of the novel photosensitivity has been attributed to the hydroxyl groups on the sugar ring of AMP that react with silver ions on the surface of the bimetal nanoclusters and induce an increase in the particle size. Herein, we have presented a new and feasible synthesis method for small molecule-protected bimetal nanoclusters to improve their luminescence properties.