Interactions between polybrominated diphenyl ethers and graphene surface: a DFT and MD investigation

Abstract

Understanding the adsorption behavior of chemical pollutant molecules on graphene surfaces is of both fundamental and practical importance for the application of graphene in environmental analysis. In this work, the mechanism and thermodynamics of adsorption of polybrominated diphenyl ethers (PBDEs) on graphene surfaces were studied by density functional theory and molecular dynamics methods. Nine types of PBDE molecules with different degrees of bromination and diphenyl ether (DE) molecules were selected as the adsorbates. It was found that the interaction strengths between the PBDE congeners (without 6 and 6′-substitution) and graphene increased with the degree of bromination. The adsorption energies of these systems also exhibited a positive linear correlation with the hydrophobicity of PBDE molecules, while for the other three PBDEs with 6 or 6′-substitution, the steric-hindrance effect leads to the molecules forming single π–π stacking interactions with the graphene surface and exhibiting a different adsorption behavior. The electronic density of states, charge transfer analysis and thermodynamic analysis indicated that the adsorption process of PBDEs on graphene is physisorption. The MD simulation indicates that graphene is sensitive to PBDE molecules and the adsorption process of PBDE on graphene is very fast. These findings will contribute to the understanding of the adsorption chemistry of aromatic pollutants on graphene-like nanomaterials.