A theoretical approach based on a tight-binding model is developed for studying the effects of finite concentration gas adsorption (for what are known as diatomic, triatomic and quadratomic gas molecules in the general forms denoted by XY, XY2 and XY3, respectively) on electronic properties of armchair graphene nanoribbons (AGNRs). To consider the edge effects on electronic properties of pure AGNRs for the first time, two hopping parameters, for hydrogen–carbon and carbon–carbon nearest neighbor hopping, are considered. We found, for some specified values of hopping integrals and random on-site energies, that adsorbed molecule AGNRs act as donors or acceptors, which is consistent with reported experimental results for CO, NO2, O2, N2, CO2 and NH3 adsorption on graphene. Then by using these parameters and the coherent potential approximation, we investigated the effect of finite concentration gas molecule adsorption on the average density of states. Our results could be used to make p-type or n-type semiconductors by means of finite concentration adsorption of gas molecules or a gas sensor.
