Abstract:
This study reports for the first time an analysis of the interactions between edge-functionalized
graphene oxide (GO) sheets and bisphenol A (BPA) examined by semi-empirical simulations. Bisphenol A
(BPA), (CH3)2C(C6H4OH)2, used in synthesis of a variety of polymers, is one of the chemicals produced in
very high quantities worldwide, with more than 450 metric tons released annually into the environment.
Due to its ability to mimic estrogen and it being an endocrine disruptor, it is a pollutant of serious concern.
Graphene oxides have been studied extensively as electrochemical sensor materials for analytes, wherein
the sensor performance (e.g., sensitivity) depends on the nature and amount of oxygen-containing
functional groups present. This work considers a lattice containing 59 hexagonal cells (C150H34), with one
edge modified by carbonyl/carboxyl groups, is used to examine interactions with BPA. Simulations are
carried out at the semi-empirical PM6 level using MOPAC and the DH2 modification is employed to
calculate interaction energies. It is seen that the hydrogen/oxygen atoms of the phenolic group(s) of BPA
interact primarily with the oxygen atoms of the carbonyl/carboxyl group or the hydrogen atoms of the
carboxyl groups/graphene edges. These interactions are predominantly polar and non-covalent in nature,
e.g., hydrogen bonds, in addition to dispersion. The heat of formation of the GO-BPA complex decreases
with increasing number of functional groups in GO and becomes exothermic. However, the strength of the
GO-BPA interaction goes through a maximum at 4 carboxyl groups (for an edge with 7 carbon atoms).
Beyond this, the carboxyl groups start interacting significantly amongst each other, weakening the GO-BPA
interaction. Optimized structures, charges and the corresponding interaction energies are presented for
eight different GO structures (2 containing carbonyl groups and 6 containing carboxyl groups).
