Synthesis of Au@CuO 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 owing to their unique metal-semiconductor interface and the integration of the properties from both core and shell materials. Although many efforts have been made toward the precise synthesis of Au@CuO core-shell structures, the chemical stability of Au@CuO aqueous suspensions, which is of great significance in many related applications, is not mentioned in any published research. Herein we report the synthesis of Au@CuO 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 CuO thickness in the range of 2-40 nm. Furthermore, the chemical stability of Au@CuO core-shell nanoparticle suspensions in water/ethanol mixed solvents is investigated. It is found that water/ethanol mixed solvents with a larger amount of water are more likely to deteriorate the stability of Au@CuO NPs by oxidizing CuO to CuO. The results from this work may provide useful information for the preparation of metal@CuO water-based suspensions that are expected to be used for SERS, photocatalyst, or photothermal applications.