The Band Gap of Graphene Is Efficiently Tuned by Monovalent Ions
  Following recently published study of Prezhdo and coworkers (JPC Letters, 2014, 5, 4129-4133), we report a systematic investigation of how monovalent and divalent ions influence valence electronic structure of graphene. Pure density functional theory is employed to compute electronic energy levels. We show that LUMO of an alkali ion (Li+, Na+) fits between HOMO and LUMO of graphene, in such a way tuning the bottom of the conduction band (i.e. band gap). In turn, Mg2+ shares its orbitals with graphene. The corresponding binding energy is ca. 4 times higher than in the case of alkali ions. The reported insights provide inspiration for engineering electrical properties of the graphene containing systems. 
Guilherme Colherinhas, Eudes Eterno Fileti and Vitaly V. Chaban
cond-mat.mtrl-sci