▎ 摘　　要

Phenyl radical (Ph-center dot) adsorption on monolayer graphene sheets is used to investigate the band-gap manipulation of graphene through density functional theory. Adsorption of a single Ph-center dot on graphene breaks the aromatic pi-bond and generates an unpaired electron, which is delocalized to the ortho or para position. Adsorption of a second radical at the ortho or para position saturates the radical by electron pairing and results in semiconducting graphene. Adsorption of a second radical at the ortho position (ortho-ortho pairing) is found to be more favorable than adsorption at the para position (ortho-para pairing), and the ortho-ortho pairing has stronger effects on band-gap opening compared with ortho-para pairing. Adsorption of even numbers of Ph-center dot on graphene by ortho-ortho and ortho-para pairings, in general, increases the band gap. Our study shows promise of band-gap manipulation in monolayer graphene by Ph-center dot adsorption, leading to potential wider applications of graphene.