Integrating molecular modeling methods to study the interaction between Azinphos-methyl and gold nanomaterials for environmental applications

We utilized density functional theory (DFT) to investigate the electronic structure and Raman spectrum of Azinphos-methyl (AzM) (C₁₀H₁₂N₃O₃PS₂) both in isolation and in combination with gold nanoclusters (Au_n, n = 2, 4, and 6). The research highlights a significant enhancement in Raman activity with increasing gold atom count from AzM-Au₂ to AzM-Au₄. The DFT calculations provide a comprehensive analysis of various electronic properties, including HOMO and LUMO energies, gap energy (Eg), ionization potential (IP), and electron affinity (EA), comparing these with experimental results from Liu et al. (2012). We also examined reactivity parameters, electrostatic properties, molecular electrostatic potential (MEP), Natural bond orbital (NBO) analysis, and atoms-in-molecules theory (AIM). The binding energy trends among the (AzM)-Aun complexes revealed a hierarchy: (AzM)-Au₂ > (AzM)-Au₆ > (AzM)-Au₄. Monte Carlo simulations were used to explore AzM interactions with gold nanoparticles (AuNPs) of various shapes and sizes, indicating that increased Raman intensity correlates with higher global electrophilicity and total polarizability. The results suggested that the stability of the complexes improves with more gold atoms, as evidenced by greater charge transfer, interaction energies, and second-order stabilization energies (E²). Among the complexes studied, AzM-Au₂ showed the highest stability. Monte Carlo simulations revealed that the right circular cone-shaped structure, especially at 7 nm, demonstrated the most negative adsorption energy, indicating stronger adsorption interactions. This research fills a gap in previous studies on AzM, providing valuable insights and serving as a reference for future work.