A DFT study of dopamine-graphene interactions

A.C ROSSI FERNÁNDEZ; CASTELLANI, N.J

Montevideo

Congreso; XLII Congreso Latinoamericano de Químicos Teóricos de Expresión Latina; 2016

The detection of biological molecules has undergone noticeably advances in the last years due to the incorporation of techniques based on nanotechnological materials such as semiconductor nanoparticles, semiconductor nanowires and carbon nanotubes. In particular, for the detection of DA (dopamine), a very importantneurotransmitter, the detection was accomplished using high resolution voltammetry by means of graphene-based electrodes. In the present work the adsorption of neutral DA on the surface of G (graphene) and GV (defected graphene with monovacancies) was studied in the framework of DFT (Density Functional Theory) formalism as implemented in VASP (Vienna Ab-initio Simulation Program) [1].The surface was modeled with a slab where G is replicated in the normal direction with a vacuum gap of 25 Å. In the calculations the vdW-like dispersive interactions were taken into account by the method of Grimme and by using the method due to Langreth y Lundquist. The G supercell has 50 carbon atoms. Several adsorption modes for the DA/G and DA/GV systems were considered, noting that the geometries where the DA molecule is parallel to G or GV are the more stable. The corresponding DA adsorption energies and the DA-G distances for the case of the G surface are indicative of an adsorption of physisorptive nature, while in the case of the GV surface the DA-GV interaction is more significant owing to the presence of a hydrogen bond. This bond is formed between one of the DA hydroxyl groups and one carbon of the G monovacancy. These attractive interactions must compete with a covalent repulsion between the occupied  orbitals of DA ring and  orbitals of G. The electronic charge redistribution due to adsorption is compatible with an electronic drift from DA to G. The attractive non-covalent interactions were analyzed with the NCI technique.