▎ 摘　　要

We investigate density of states and an electric current of an armchair hexagonal graphene ring (AHGR) with adsorbed gas molecules (CO, NO, CO2, and NH3). In order to optimize the structure as a gas sensor, a perpendicular magnetic field and an in-plane electric field are applied. The electronic structure of AHGR is sensitive to adsorbed gas molecules so that it changes to n-type and p-type semiconductor in the presence of NH3 and CO2 gas molecule. In addition, the current passing through graphene ring attached to two semi-infinite armchair graphene nanoribbon leads obtains different values by interaction with the gas molecules at a fixed voltage which may be of relevant to gas sensors. By tuning magnetic or electric field, the difference of current values related to various gas molecules increases because of change in density of states that it provides an appropriate condition to recognize more types of adsorbed gas molecules.