Ag@Cu₂O-MXene Core-Shell Nanostructures: Plasmonic Coupling and Charge Transfer for Ultra-Sensitive SERS Detection

The two-dimensional (2D) layered structure of MXene provides a large specific surface area, making it an ideal platform for optimizing geometric configurations in surface-enhanced Raman scattering (SERS) applications. In this study, we developed a novel ternary core-shell nanostructure, Ag@Cu2O-MXene, in which Ag@Cu2O core-shell nanoparticles (NPs) are uniformly anchored onto 2D Ti3C2Tx MXene nanosheets. The Ag NPs exhibit strong localized surface plasmon resonance, while the narrow bandgap and high electron mobility of Cu2O shell promote efficient charge transfer. Importantly, plasmonic coupling between the Ag core and the MXene substrate further enhances plasmon absorption, resulting in a substantial increase in SERS activity and enabling highly sensitive molecular detection. Using this composite, we achieved an ultra-low detection limit of 10–9 M for methylene blue. MXene substrate further facilitates rapid electron transfer from the Ag core to the the Cu2O shell, while its surface defects contribute additional charge carriers to Cu₂O, enhancing the utilization of photogenerated electron. Notably, the SERS enhancement was positively correlated with the thickness of Cu2O shell, highlighting the tunable nature of the Ag@Cu2O-MXene core-shell nanostructure.