Optimized electromagnetic enhancement and charge transfer in MXene/Au/Cu 2 O 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/Cu 2 O hybrids are combined with two-dimensional Ti 3 C 2 T x MXene ultrathin nanosheets, is prepared and used for efficient SERS detection of molecules. By controlling the growth of Cu 2 O on Au nanotriangles, Au/Cu 2 O hybrids with three tips exposed are prepared, which show much better SERS performance than bare Au and core-shell Au@Cu 2 O in detecting methylene blue (MB) under excitation at 785 nm due to the optimized electromagnetic field enhancement and charge transfer. Furthermore, the Au/Cu 2 O hybrids are transferred to the plasmonic Ti 3 C 2 T x nanosheet, generating a further enhanced electromagnetic field around their interfaces. As a result, the MXene/Au/Cu 2 O hybrids present further improved SERS activity, and their analytical enhancement factor reaches 2.4 × 10 9 and the detection limit is as low as 10 -12 M. The enhancement mechanism can be ascribed to the improved electric field enhancement around the Au tips and the interface between MXene and Au/Cu 2 O. Meanwhile, the multiple charge-transfer processes between Au, Cu 2 O, MXene, and MB also play an important role in improving the SERS signal.