Nitrogenated Holey Graphene (C2N-h2D): An excellent sensor for neurotransmitter amino acids

Abstract

Interactions of amino acids with organic surfaces are highly relevant to the development of modern synthetic biomaterials with biocompatibility and low biotoxicity. Biomolecule-surface interactions vary differently according to the molecule orientation, charge state, and distance from the surface. Furthermore, the electron transfer through molecule/surface could also play a key role in biological recognition and signaling systems. Here, using density functional theory (DFT), we investigated the interactions of three neurotransmitter amino acids (NAAs), namely, glycine (Gly), γ-aminobutyric acid (Gaba), and glutamate (Glu), onto a nanosheet of holey nitrogenated graphene (C2N-h2D). In general, the interactions between amino acids and carbon-based surfaces are mediated through weak van der Waals interactions. However, based on interaction energy and charge density difference calculations, there is a strong physisorption process between NAAs and the C2N structure. In particular, Gaba and Glu can act as exclusive electron donor and acceptor, respectively. Our calculations also reveal that, by changing the orientations from neutral to zwitterionic, the Gly molecule changes from a donor to a strong acceptor of electrons. In the case of electron donation, the resistivity on the C2N surface should be reduced. These findings indicate that the C2N surface is an excellent candidate for high-performance biosensor applications. From the band structure point of view, the NAAs molecules introduce occupied flat bands within the bandgap of the C2N single layer, while the surface energy levels keep the bulk characteristics of the semiconductor system. Finally, the optical absorption spectrum of NAAs-C2N systems reveals that these NAAs seem to improve the photoactivity performance of the C2N structure, with the appearance of intraband transitions.