Understanding the co-adsorption mechanism between nanoplastics and neonicotinoid insecticides from an atomistic perspective

CONTEXT: Density functional theory calculations were applied to elucidate the co-adsorption mechanism of different nanoplastic-neonicotinoid insecticides (NP-NEO) complexes where polyethylene terephthalate (PET), polyethylene (PE), and polystyrene (PS) are tested as adsorbents, and imidacloprid (IMI) and clothianidin (CLO) are considered adsorbates. HOMO energies indicate all nanoplastics (NPs) tend to donate electrons, while LUMO analysis shows PET and CLO favor electron acceptance, while PE, PS, and IMI are unstable, the last one due to resonance effects. Complex formation slightly increases HOMO energies but maintains trends, while LUMO energies improve only in PET due to its carbonyl groups. The LUMO-HOMO gap (G) decreases significantly in PE-IMI and PE-CLO (~ 28%), reducing stability. Our results reveal that electrostatic and dispersion interactions dominate adsorption, contributing ~ 90% to the stabilization of NP-NEO complexes through physisorption onto the surface of all plastic matrices. Adsorption energies span the range from - 18.32 to - 32.56 kcal/mol, with the PE-IMI complex being the most stable. Our results provide molecular-level insights into the nature of pesticide-nanoplastic interactions, contributing to a better understanding of how these materials may influence the environmental fate of neonicotinoids. METHODS: Calculations of density functional theory at the wB97XD/def2-SVP level of theory in Gaussian16 were implemented. PCM, BSSE, and dispersion effects were considered. To gain insights into the nature of the interaction, ALMO-EDA and IGMH analyses were performed. Finally, the structures were visualized in the VMD program.