Graphene oxides(GOs)may offer extraordinary potential in the design of high-performance molecular sensors due to its unique electronic and structural properties.Using the density functional theory calculations,we investigate the interaction of ammonia with graphene oxides(GO).Our results indicate that the presence of diverse active defect sites on GOs can strengthen the adsorption of NH3 on the surface and enhance charge transfers from NH3 to GO.The oxygen groups of GOs can lead to formation of OH---N and O---HN hydrogen bonds with NH3,and even induce dissociation of the adsorbed NH3 into the chemisorbed NH2 or NH species by the H atom abstractions.The adsorption and dissociation of NH3 result in the removal of surface oxygen species through the hydroxyl group hydrogenation and the ring opening of epoxy group.The mechanisms for reduction of GO with NH3 are proposed.The hydroxyl group exhibits relatively higher reactivity toward the hydrogen abstraction from the adsorbed NH3 than the epoxy group in GO with the single oxygen group.Followed by the ring opening of the epoxy group,the newly-formed hydroxyl group can be removed by the second H atom abstraction from NH2.The calculated results show good agreement with available experimental observations.