ELECTRONIC STRUCTURES AND ADSORPTION ENERGIES OF GRAPHENE DOPED WITH PYRENE DERIVATIVES

Abstract

Effects of size, shape, and pyrene doping on electronic properties of graphene were theoretically investigated using Density functional theory method with PBE and M06-2X functionals and cc-pVDZ basis set. Two shapes of the zigzag edged graphene, hexagonal (HGN) and rhomboidal (RGN), were considered. The energy band gap of graphene depends on shape and decreases with size. The HGN has larger band gap energy (0.79 – 2.94 eV) than the RGN (0.01 – 1.31 eV). The doping of pyrene and pyrene derivatives on both HGN and RGN were also studied. The adsorption energy of pyrene and pyrene derivatives on graphene does not depend on shape with energies between 21 – 27 kcal/mol. The substituent on pyrene enhances the binding to graphene but the strength does not depend on electron withdrawing or donating capability. The doping by pyrene and pyrene derivatives also shifts HOMO and LUMO energies of graphene. Both positive (destabilizing) and negative (stabilizing) shifts on HOMO and LUMO energies of graphene were seen. The direction and magnitude of the shift do not follow electron withdrawing and donating capability of pyrene substituents. However, only a slight shift was observed for doped RGN. The shift of 0.38 eV was noticed for HOMO of HGN doped with 1-aminopyrene (PyNH2) and of -0.05 eV for LUMO of HGN doped with 1-pyrenecarboxylic acid (PyCOOH).