Dynamic repulsive interaction enables an asymmetric electron–phonon coupling for improving Raman scattering

Abstract

Two-dimensional (2D) materials are an excellent platform for surface-enhanced Raman spectroscopy (SERS). For ReS₂, the Raman enhancement effect can be highly improved through the dipole–dipole interactions and synergistic resonance effects in the phase-engineering ReS₂ films. However, the performance of the substrate can be improved further through regulating the electronic interaction between the ReS₂ and probe molecules. Herein, a dynamic coulomb repulsion strategy is proposed to trigger an electronic state redistribution by asymmetric electrostatic interactions. With the phase-engineering ReS₂/graphene heterostructure as a prototype, under laser excitation, the generated hot electrons in graphene and ReS₂ can repel each other due to Coulomb interaction, which breaks the symmetrical distribution of hot electrons in ReS₂, and increases the electronic concentration at the interface between ReS₂ and the probe molecule. With R6G as the probe molecule, the asymmetric electron distribution and synergistic resonance effects on their interface improve the limit of detection to 10⁻¹² M with an EF of 2.15 × 10⁸. Meanwhile, the heterostructure also shows good uniformity, stability as well as unique anisotropy. This strategy can be generalized to other 2D heterostructures to obtain the ultrasensitive SERS substrates.