Tuning the structural properties and chemical activities of graphene and hexagonal boron nitride for efficient adsorption of steroidal pollutants

Abstract

Two-dimensional (2D) materials are in general considered as incredible recognition functions toward different targets. Here, our aim is to understand whether the target steroidal pollutants can adsorb on 2D surfaces or not? For this purpose, we have performed first-principles calculations to analyze the molecular interactions involved in the adsorption mechanism of target steroidal estrogens (estrone, E1; 17β-estradiol, E2 and estriol, E3) and anti-estrogens (bisphenol-A, BPA) on pure and defective graphene and boron nitride (h-BN) surfaces. After screening 144 configurations of both pure and defective graphene and h-BN surfaces, we found that the nitrogen vacancy in h-BN (VN@BN) surface is highly sensitive and selective towards target steroid molecules with apparent charge transfer and robust adsorption energy. The contrasted chemical reactivity of h-BN and graphene demonstrates that the target steroid pollutants are chemisorbed over VN@BN, while this mechanism is not spotted on pure and defective graphene surface. The decreased distance between VN@BN and steroid molecules is due to electronic rearrangement, leading to an attraction of B-atoms of VN@BN toward target steroid molecules. Marked variations are also observed on the electronic structure of VN@BN after the adsorption of target steroids, which indicates significant charge transfer from steroid molecules to corresponding surfaces. The observed conspicuous variation between the two systems can be related to their electronic properties and the availability of insufficient screening patterns for graphene surface when compared to that of h-BN. These fundamental findings may furnish novel insights into the rational design and development of defect engineered h-BN for the detection of critically relevant steroid pollutants.