Effects of shape, size, and pyrene doping on electronic properties of graphene nanoflakes

Abstract

Effects of size, shape, and pyrene doping on electronic properties of graphene nanoflakes (GNFs) were theoretically investigated using density functional theory method with PBE, B3PW91, and M06-2X functionals and cc-pVDZ basis set. Two shapes of zigzag GNFs, hexagonal (HGN) and rhomboidal (RGN), were considered. The energy band gap of GNF depends on shape and decreases with size. The HGN has larger band gap energy (1.23-3.96 eV) than the RGN (0.13-2.12 eV). The doping of pyrene and pyrene derivatives on both HGN and RGN was also studied. The adsorption energy of pyrene and pyrene derivatives on GNF does not depend on the shape of GNFs with energies between 21 and 27 kcal mol. The substituent on pyrene enhances the binding to GNF but the strength does not depend on electron withdrawing or donating capability. The doping by pyrene and pyrene derivatives also shifts the HOMO and LUMO energies of GNFs. Both positive (destabilizing) and negative (stabilizing) shifts on HOMO and LUMO of GNFs were seen. The direction and magnitude of the shift do not follow the electron withdrawing and donating capability of pyrene substituents. However, only a slight shift was observed for doped RGN. A shift of 0.19 eV was noticed for HOMO of HGN doped with 1-aminopyrene (pyNH) and of 0.04 eV for LUMO of HGN doped with 1-pyrenecarboxylic acid (pyCOOH). Graphical Abstract HOMO and LUMO Energies of pyrene/pyrene derivatives doped Graphene Nanoflakes.

Anatomy of On-Surface Synthesized Boroxine Two-Dimensional Polymers

“…arising from the adsorption energy (~25 kcal/mol) 45 of the pyrene units on the HOPG surface, the hydrogen-bonding interactions between the boronic acid units (dimerization energies range from -7.0 to 10 -10.8 kcal/mol, see supporting information, also in agreement with the literature) 46 and the dense molecular packing within these networks.…”

“…These experiments indicate that once formed, these networks are sufficiently stable on the surface under given experimental conditions and the thermal activation provided to the system is insufficient to overcome the cohesive forces holding the self-assembled systems together. The high stability of these self-assembled systems could be understood by considering the high enthalpic gain arising from the adsorption energy (∼25 kcal/mol) 45 of the pyrene units on the HOPG surface, the hydrogen-bonding interactions between the boronic acid units (dimerization energies range from −7.0 to −10.8 kcal/mol, see Supporting Information, also in agreement with the literature), 46 and the dense molecular packing within these networks.…”

The holy grail of pyrene-based surface ligands on the sensitivity of graphene-based field effect transistors

“…5b, blue curve), V Dirac shifts toward a more positive gate voltage (+0.33 V). As it has been consistently reported that PBASE adsorption on graphene induces hole doping due to the presence of an NHS electron withdrawer group, [42][43][44][45] it is expected from PMAL molecules carrying a similar chemical functionality to also induce a hole doping effect after immobilization on graphene. Successively, a negative shift of V Dirac (+0.31 V) is observed after covalent grafting of the thiolated cTnIaptamer and PEG to PMAL linkers (Fig.…”

Effect of electric field on molecular and electronic structures of graphene with 4N-divacancy defect and application on hydrogen gas storage

“…and 0.025 a.u. of C 54 H 18 and C 96 H 24 , respectively.These results were inconsistent with previous studies54 where the HOMO-LUMO gap energy was reduced when the size of GQDs was increased. The degree of curvature, |a|, fitted by a quadratic equation, and the HOMO-LUMO gap energies of C 24 H 12 , C 54 H 18 , and C 96 H 24 were displayed in Figure13.…”