A robust synthesis of reverse Au/ZnO core/shell nanostructures with high visible photocatalytic activity of methylene blue dye†

Abstract

In this study, we report a robust electrochemical synthesis of reverse Au/ZnO core/shell nanostructures via a galvanic replacement strategy, aimed at enhancing the photocatalytic degradation of methylene blue (MB) dye. ZnO nanoparticles were first electrochemically synthesized, followed by the formation of Au (core)/ZnO (shell) nanostructures. The shell formation is attributed to a galvanic interaction between ZnO and Au³⁺ ions, resulting in the reduction of Au and subsequent ZnO encapsulation. The morphology, structure, optical properties, and photocatalytic activity of the resulting nanostructures were systematically characterized. The synthesized particles exhibited core/shell nanostructure with diameters of 30–50 nm, comprising Au cores (25–40 nm) and ZnO shells (5–10 nm). Under visible light irradiation, the Au/ZnO nanostructures achieved up to 98.9% MB degradation within 90 min. The enhanced photocatalytic performance is attributed to the localized surface plasmon resonance (SPR) of the Au core, which promotes efficient photo-induced electron transfer to the ZnO shell and extends light absorption into the visible range.