Improving gas sensing properties of armchair graphene nanoribbons by oxygen-hydrogen terminated edges

This work is focused on the effects of doping and neutralizing edges of armchair graphene nanoribbon (AGNR) on its gas sensing behavior. Four types of structures, pristine AGNR, boron doped AGNR, nitrogen doped AGNR and defective AGNR, when the ribbons edges are terminated by both hydrogen and oxygen atoms at the same time, are investigated in detail. First, interaction of the aforementioned structures with three gases molecules, CO, O-2 and CO2, are investigated by using the density functional theory, then their applications as gas sensors are studied. An AGNR structure depending on its edge termination and type of the adsorbed gas illustrates different atomic configurations. Different atomic configurations show different physical structure, chemical behavior and electronic properties. Our results have shown that the adsorptions of the three gases molecules have stronger interaction with the defective AGNR than with the other three AGNR structures. Therefore, based on quantum analysis of energy and calculation of current flow, the defective AGNR neutralized by both H and O at edges, concurrently, shows high sensitivities to CO, O-2 and CO2 gases molecules. In fact, the strong interactions between adsorbed gases molecules and AGNR cause significant changes in electronic properties of edge terminated AGNR. It is worth mentioning that the sensitivity of graphene based gas sensors could be significantly improved by introducing suitable dopants and defects. The results presented in this work indicate that the defective AGNR terminated by both hydrogen and oxygen atoms can operate as a selective CO, O-2 and CO2 gas sensor.