Differential Response of Doped/Defective Graphene and Dopamine to Electric Fields: A Density Functional Theory Study

First-principles density functional theory calculations are performed on dopamine-graphene systems in the presence of an external electric field. The graphene lattice is also modified via substitutional boron- and nitrogen-doping, and via the introduction of defects (monovacancy and Thrower Stone Wales). The geometry optimization, electronic density of states, cohesive energy, electronic charge density, and wave functions are analyzed. Our results revealed that dopamine is anchored on the surface of graphene via a physisorption mechanism, and the cohesive strength varies as B-doped > N-doped > vacancy defect > Thrower Stone Wales defect. Boron-doped graphene exhibits valence states with dopamine molecules; furthermore, this system showed the strongest cohesive energy. When an electric field is applied, we observe shifts in the valence states near the Fermi level producing a decrease in the molecule layer interaction. We envisage that the present results could help in developing novel biosensors based on doped/defective graphene field-effect transistor devices.