First-Principles Study of Crown Ether and Crown Ether-Li Complex Interactions with Graphene

Adsorption of molecules on graphene is a promising route to achieve novel functionalizations, which can lead to new devices. Density functional theory is used to calculate stabilities, electronic structures, charge transfer, and work function for a crown-4 ether (CE) molecule and a CE-Li (or CE-Li+) complex adsorbed on graphene. For a single CE on graphene, the adsorption distance is large with small adsorption energies, regardless of the relative lateral location of the CE. Because CE interacts weakly with graphene, the charge transfer between the CE and graphene is negligibly small. When Li and Li+ are incorporated, the adsorption energies significantly increase. Simultaneously, an n-type doping of graphene is introduced by a considerable amount of charge transfer in CE-Li adsorbed system. In all of the investigated systems, the linear dispersion of the p, band in graphene at the Dirac point is well-preserved; however, the work function of graphene is effectively modulated in the range of 3.69 to 5.09 eV due to the charge transfer and the charge redistribution by the adsorption of CE-Li and CE-Li+ (or CE), respectively. These results provide graphene doping and work function modulation without compromising graphene's intrinsic electronic property for device applications using CE-based complexes.