Density Functional Theory Study on the Interaction between Aflatoxin B1/M1 and Gold Substrate.

Aflatoxin M1 (AFM1) and its precursor, Aflatoxin B1 (AFB1), are highly pathogenic and mutagenic substances, making the detection and sensing of AFB1/M1 a long-standing focus of researchers. Among various detection techniques, surface-enhanced Raman spectroscopy (SERS) is considered an ideal method for AFB1/M1 detection due to its ability not only to enhance characteristic frequencies but also to detect shifts in these frequencies with high repeatability. Therefore, we employed density functional theory in conjunction with surface-enhanced Raman spectroscopy to investigate the interaction between AFB1/M1 and a Au substrate in the context of the SERS effect for the first time. To predict the potential binding sites of AFB1/M1 and Au within the SERS effect, we performed calculations on the molecular electrostatic potential of AFB1/M1. Considering the crucial role of the binding energy in molecular docking studies, we computed the binding energy between two molecules interacting with Au at different binding sites. The molecular frontier orbitals and related chemical parameters of AFB1/M1 and "molecular-Au" complexes were computed to elucidate the alterations in AFB1/M1 molecules under the SERS effect. Subsequently, the theoretical Raman spectra of AFB1/M1 and the complexes were compared and analyzed, enabling determination of the adsorption conformation of AFB1/M1 on the gold surface based on SERS surface selection rules. These findings not only provide a deeper understanding of the interaction mechanism between molecules and substrates in the SERS effect but also offer theoretical support for developing novel aflatoxin SERS sensors.