Light-field and external-field modulation in surface-enhanced raman scattering: Strategies and prospects

The development of surface-enhanced Raman scattering (SERS) technology is critically reliant on the effective modulation of the electromagnetic mechanism and chemical mechanism. In this paper, we conduct a systematic review of the recent advancements in the modulation of SERS by multi-physical fields (light field, magnetic field, and electric field) and their cooperative modulation. Light field modulation enhances the intensity and area of hotspots by optimizing the matching between the local surface plasmon resonance of nanostructures and the parameters of incident light (wavelength, polarization, and pulse). Moreover, the photo-induced plasmonic thermal effect dynamically regulates the phase transition between the nanogap and the material, achieving the synergistic enhancement of SERS. Magnetic field modulation capitalizes on the magnetic induction of magnetic materials and the magnetic resonance behavior of non-magnetic structures. It enables an external magnetic field to control the aggregation and spatial organization of nanoparticles, thereby generating high-density hotspots and enhancing the detection sensitivity and selectivity. Electric field modulation can adjust the band structure, carrier density, and molecular orientation of the substrate through an external electric field or the spontaneous electric field of functional materials (such as piezoelectric, triboelectric, thermoelectric, and pyroelectric materials), thus enhancing the charge transfer efficiency and the local electromagnetic field strength. The multi-field cooperative modulation strategy overcomes the static limitations of traditional SERS substrates and further provides a crucial theoretical and technical approach for realizing a high-performance, intelligent, and reconfigurable SERS sensing platform.