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.