SERS Chemical Enhancement Mechanism of Phenthoate on Gold Nanoparticles Revealed by DFT and TD-DFT

This study employed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to investigate the interaction mechanism between Phenthoate and Au₂₀ nanoclusters, and the solvent environment effect was examined under the polarizable continuum model (PCM). By comparing and analyzing theoretical Raman active spectra and experimental Raman spectra, the phenomenon of selective enhancement of specific vibrational modes in surface-enhanced Raman spectroscopy (SERS) was explained. By analyzing the molecular structure, frontier molecular orbitals (FMOs), ultraviolet-visible absorption spectra (UV-vis), noncovalent interactions (NCI), reduced density gradients (RDG), electron localization function (ELF), and localized orbital locator (LOL), the adsorption mechanism and the spectral characteristics induced by interfacial charge transfer were comprehensively revealed at the electronic level. Phenthoate chemically adsorbed onto the Au₂₀ surface through the S atom, forming a stable complex. Meanwhile, this charge transfer mechanism effectively modulated the polarization rate of the molecule. This study provides a theoretical basis for elucidating the adsorption behavior and spectral response mechanism of organophosphorus pesticides on metal nanostructures, offering valuable insights for the design of highly sensitive SERS sensors.