Adsorption behaviour of boron nitride nanosheets towards the positive, negative and the neutral antibiotics: Insights from first principle studies

Abstract

In this study, the adsorption of ampicillin (APC, positive), ciprofloxacin (CFX, neutral) and cephalosporin (CLS, negative) antibiotics on boron nitride nanosheets (BNNS) were investigated using the first principle density functional theory. To make a comprehensive study on the adsorption of the positive, negative and neutral antibiotics on the BNNS, investigations were made using the electrostatic potential maps, natural-bonding orbitals charge distributions and the density of states plots. Theoretical IR spectra of clusters before and after adsorption were obtained to study the stability of the post adsorption complexes. Koopman's approach was used to study the properties of antibiotics and complex clusters. The quantum mechanical descriptors of various systems were also calculated to comment upon the feasibility of the interactions. From the electrostatic potential contours and the natural-bonding orbitals charge transfer data, it was clear that the maximum charge accretion occurred in the CLS-BNNS complex. APC was the closest to the BNNS at a distance of 2.52 Å. The adsorption energies calculated for the three complex clusters revealed that CLS released the most adsorption energy of −167.74 kJ/mol, indicating that interaction was maximum for CLS antibiotics. CLS-BNNS cluster exhibited the smallest HOMO-LUMO gap, indicating that CLS antibiotic adsorption on the BNNS was more favourable among the three antibiotics. The plausible mechanism investigated indicated that the interactions between antibiotics and BNNS were mainly due to the weak Van der Waal forces. This theoretical study showed the promising application of BNNS as an effective adsorbing material for removing negatively charged antibiotics from an aqueous stream.