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

Abstract

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@Cu 2 O core−shell structures, the chemical stability of Au@Cu 2 O 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@Cu 2 O 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 Cu 2 O thickness in the range of 2−40 nm. Furthermore, the chemical stability of Au@Cu 2 O 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@Cu 2 O NPs by oxidizing Cu 2 O to CuO. The results from this work may provide useful information for the preparation of metal@Cu 2 O water-based suspensions that are expected to be used for SERS, photocatalyst, or photothermal applications.

Self-sustainable and recyclable ternary Au@Cu2O–Ag nanocomposites: application in ultrasensitive SERS detection and highly efficient photocatalysis of organic dyes under visible light

“…1b). Compared with the absorption peak of Cu 2 O nanocrystals, the absorption peak of Au@Cu 2 O NCs is blueshifted and broadened due to the interband transition and scattering of the Cu 2 O shells 31 . When Ag nanocrystals were immobilized on Au@Cu 2 O NC shells, the absorption bands shifted further to lower wavelengths due to the interaction between Au@Cu 2 O NCs and Ag nanocrystals 32 .…”

TiO2 Thickness-Dependent Charge Transfer in an Ordered Ag/TiO2/Ni Nanopillar Arrays Based on Surface-Enhanced Raman Scattering

“…Additionally, the degree of induced excitation CT process at the metal–semiconductor interface depends on the parameter and dielectric properties of the semiconductor. For example, the UV-vis absorption properties and the chemical stability of Au@Cu 2 O core−shell nanoparticles are found to be tunable with Cu 2 O thickness [ 24 ]. Zhao et al [ 25 ] found that the CT degree of the Ag/PATP/ZnO system depends on the size of ZnO nanoparticles, and the possible CT resonance mechanism was responsible for the size-dependent SERS behavior.…”

“…The study of SPR and interfacial CT process provides vital information on the interfacial interaction of substrate materials and also provides a theoretical basis for the optimal design of excellent SERS substrates. At present, the effect of the semiconductor thickness on the SERS and photocatalytic performance in hybrid systems has been reported [ 24 , 28 , 29 , 30 ]. However, the SPR and CT mechanism, as well as the CT process at the substrate–molecule interface related to semiconductor thickness changes, are rarely studied in the composite system.…”

A SERS Study of Charge Transfer Process in Au Nanorod–MBA@Cu2O Assemblies: Effect of Length to Diameter Ratio of Au Nanorods

“…Among the potential hybrid nanostructures, the metal@semiconductor core-shell heterostructure has been extensively studied because this composite material combines two completely different materials together to form a unique structure with synergistic properties and functions [16,17]. Among these materials, the Au NP@semiconductor structure is widely used in photocatalysis, solar cells, biology, sensing, and other fields [18][19][20][21][22]. Compared with Au NPs, Au nanorods (NRs) are also a commonly used SERS substrate.…”