Optimized electromagnetic enhancement and charge transfer in MXene/Au/CuO hybrids for achieving efficient SERS.

The rational optimization of the electromagnetic field enhancement and charge transfer in a Raman substrate is vital for achieving efficient surface-enhanced Raman scattering (SERS). Herein, a ternary plasmonic substrate, whose structure-adjustable Au nanotriangle/CuO hybrids are combined with two-dimensional TiCT MXene ultrathin nanosheets, is prepared and used for efficient SERS detection of molecules. By controlling the growth of CuO on Au nanotriangles, Au/CuO hybrids with three tips exposed are prepared, which show much better SERS performance than bare Au and core-shell Au@CuO in detecting methylene blue (MB) under excitation at 785 nm due to the optimized electromagnetic field enhancement and charge transfer. Furthermore, the Au/CuO hybrids are transferred to the plasmonic TiCT nanosheet, generating a further enhanced electromagnetic field around their interfaces. As a result, the MXene/Au/CuO hybrids present further improved SERS activity, and their analytical enhancement factor reaches 2.4 × 10 and the detection limit is as low as 10 M. The enhancement mechanism can be ascribed to the improved electric field enhancement around the Au tips and the interface between MXene and Au/CuO. Meanwhile, the multiple charge-transfer processes between Au, CuO, MXene, and MB also play an important role in improving the SERS signal.