The adsorption of dopamine on nitrogen-doped graphene: a DFT study

A.C ROSSI FERNÁNDEZ; N.J. CASTELLANI

París

Congreso; XLIII Congress of Theoretical Chemists of Latin Expression; 2017

Universidad de la Sorbonne

The DA (dopamine) molecule is an important neurotransmitter that plays a significant role in the function of the mammalian central nervous, renal and hormonal systems. The detection of dopamine performed by voltammetric techniques with graphene electrodes was a subject of increasing interest, taking into account that dopamine is an electrochemically active compound through the oxidation of DA phenolic hydroxyls. Recently the doping of graphene with nitrogen in these electrodes has been proposed as a way to achieve a better resolution in oxidation peaks. In the present work, the neutral DA adsorption on the G (graphene) surface and three different G-N (defected graphene with nitrogen as dopant) systems was studied in the framework of DFT (Density Functional Theory) formalism as implemented in VASP (Vienna Ab-initio Simulation Program) code. The surface was modeled with a slab where G is replicated in the normal direction with a vacuum gap of 25 Amstrongs. In the calculations, the vdW-like dispersive interactions were taken into account by using the vdW-DF2 method due to Langreth y Lundquist. The G supercell has 50 carbon atoms. Several adsorption modes for the DA/G and DA/G-N systems were considered. In general, the adsorption modes where the molecule is parallel or quasi-parallel to the surface are the most favored. The substitutional doping with nitrogen in graphene lattice regular sites increases the magnitude of adsorption energy, making these sites more appropriate for the anchoring of molecules that undergo the oxidative electrochemical process. In all cases considered the adsorbate-substrate interaction is in agreement with the presence of a fisisortive adsorption. Nevertheless, an important electronic charge redistribution occurs due to adsorption. The attractive non-covalent interactions of the different DA/G-N systems were analyzed with the non covalent index (NCI) and the electronic structure by means of the projected density of states concept.