How do aryl groups attach to a graphene sheet?

How aryl groups attach to a graphene sheet is an experimentally unanswered question. Using first principles density functional theory methods, we shed light on this problem. For the basal plane, isolated phenyl groups are predicted to be weakly bonded to the graphene sheet, even though a new single C-C bond is formed between the phenyl group and the basal plane by converting a sp2-carbon in the graphene sheet to sp3. However, the interaction can be strengthened significantly with two phenyl groups attached to the para positions of the same six-membered ring to form a pair on the basal plane. The strongest bonding is found at the graphene edges. A 1,2-addition pair is predicted to be most stable for the armchair edge, whereas the zigzag edge possesses a unique localized state near the Fermi level that shows a high affinity for the phenyl group.