Synthesis of Au@Cu2O Core-Shell Nanoparticles with Tunable Shell Thickness and Their Degradation Mechanism in Aqueous Solutions.

Metal@semiconductor core-shell nanoparticles (NPs) are widely used in photocatalysts, sensors and optical applications thanks to the unique metal-semiconductor interface and integration of the properties from both core and shell materials. Although many efforts have been paid on the precise synthesis of Au@Cu2O core-shell structures, the chemical stability of Au@Cu2O aqueous suspensions are not mentioned in any published research, which is of great significance in many related applications. Herein, we report the synthesis of Au@Cu¬2O core-shell NPs with small shell thickness from 2 to 40 nm through a wet-chemistry method. The UV-Vis absorption properties are found to be tunable with Cu2O thickness in the range of 2~40 nm. Furthermore, the chemical stability of Au@Cu2O core-shell nanoparticle suspensions in ethanol-water mixed solvents are investigated. It was found that ethanol-water mixed solvents with high water content are more likely to deteriorate the stability of Au@Cu2O NPs by oxidizing Cu2O to CuO. The results from this work may provide useful information for the preparation of metal@Cu2O water-based suspensions which are expected to be used for the SERS, photocatalyst or photothermal applications.