DFT-Based Theoretical Study on Label-Free SERS Detection of Type B Fumonisins: New Insights into Molecular–Substrate Interactions and Quantification Strategies

was confirmed. Analysis of the theoretical Raman spectra of vertex-binding/surface-binding complexes revealed selective enhancement phenomena associated with different docking modes. These findings provide a feasible strategy for the simultaneous quantification of the overall content of type B fumonisins and the individual components of FB1, FB2, and FB3 in a single detection. Finally, based on the characteristic frequency variations of the three molecules, a theoretically reproducible, highly sensitive, and high-throughput label-free detection strategy is proposed for analyzing type B fumonisins in complex sample systems. This study not only enhances our understanding of the physical mechanisms underlying molecular-substrate interactions in the SERS effect but also demonstrates the theoretical feasibility of using SERS for simultaneous quantification of different type B fumonisins in complex sample systems. Moreover, it provides a promising and potentially effective label-free sensing strategy for detecting substances with similar molecular structures.