Reconfigurable SERS platform based on magnetization-controlled self-assembly of magnetic nanoparticles on NdFeB composite substrate

Constructing surface-enhanced Raman scattering (SERS) substrates using magnetic control strategies is a common approach for the development of SERS-efficient tools. However, one persistent challenge lies in how to regulate the spatial coupling between the target analyte carrier and the plasmonic hot spots, in order to maximize the SERS enhancement activity. This study proposes a magnetic-field-controlled composite SERS substrate strategy, through regulating the spatial distribution of the target molecule carriers, to realize its coupling with the plasmon hot spot. This method allows to elaborate a NdFeB/PS/Ag composite structure as the plasmonic substrate, using Fe₃O₄@SiO₂@Ag (FSA) magnetic nanoparticles as the target molecule. By regulating the magnetic state of NdFeB magnetic sheets and optimizing the magnetization gradient, the spatial distribution state of FSA magnetic nanoparticles can be controlled. Meanwhile, based on the differences in magnetic field distribution at different positions on the NdFeB substrate, the regional control of SERS signals can be achieved. The finite element analysis method was also used to further verify the experimental results. Thanks to the advantages of differentiated signal distribution brought by magnetic field regulation, this system is expected to be applied to the actual detection of environmental pollutants, harmful substances in food, and biomarkers.