Band‐Gap Manipulations of Monolayer Graphene by Phenyl Radical Adsorptions: A Density Functional Theory Study

Phenyl radical (Ph . ) adsorption on monolayer graphene sheets is used to investigate the band‐gap manipulation of graphene through density functional theory. Adsorption of a single Ph . on graphene breaks the aromatic π‐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 . 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 . adsorption, leading to potential wider applications of graphene.