Tuning the Electronic Structure of Graphene by Molecular Charge Transfer: A Computational Study

Abstract

We have studied the modification in the electronic structure, as well as optical and transport properties of graphene induced by molecular charge transfer using ab initio density functional theory. Our results from first-principles spin-polarized calculations are compared with those of the available data from Raman spectroscopic studies of modified graphene systems. We find that electron donor and acceptor molecules adsorbed onto the graphene surface exhibit effective molecular charge transfer, giving rise to mid-gap molecular levels with tuning of the band gap region near the Dirac point. The molecular charge transfer causes the stiffening or softening of the Raman G-band frequency in graphene, and we find that it also has a significant impact on the intensity ratio of the D- to G-band, corroborating experimental findings. We suggest that these charge transfer mechanisms can be probed through the low-frequency profile of the optical conductivity.

Synthesis of WO3@Graphene composite for enhanced photocatalytic oxygen evolution from water

“…The trend was similar to previous studies with the p-type doping of the GR causing upshift of the G-band. 40 The Raman G-band shift provides reliable evidence of charge transfer between the GR sheets and the WO 3 in the WO 3 @GR composite and suggests a dyadic bonding between the GR and WO 3 .…”

Breakdown in the Wetting Transparency of Graphene

“…Graphene, a sheet consisting of a single-layer sp 2 lattice of carbon [1], combines optical transparency, electrical conductivity, and mechanical strength [2][3][4][5][6]. The production of large-area graphene [7] using chemical vapor deposition (CVD) has further shed light on engineering the material for real applications.…”

Adsorption of TCNQH-functionalized quinonoid zwitterions on gold and graphene: evidence for dominant intermolecular interactions

“…This is accompanied by a decrease of the HOMO-LUMO gap, at variance with observations made with zwitterion 1. While TCNQ is considered to be an electron acceptor molecule, [30][31][32][33][34][35][36][37][38][39] the XPS spectra surprisingly indicate that the substrate Au 4f binding energies decrease by 200-300 meV upon adsorption of zwitterion 4 on gold (Fig. 6a), which is indicative of charge donation to the gold surface.…”

“…[25][26][27][28][29] It appeared to us attractive to functionalize the p-benzoquinonemonoimine zwitterion core by reaction with tetracyanoquinodimethane (TCNQ), which is one of the most widely used electron acceptors in organic solar cells. Adsorption of TCNQ and its derivatives on graphene and various metals has been widely studied, [14][15][16][30][31][32][33][34][35][36][37][38] because of the presence of the four strongly electron-acceptor cyano groups with high electron affinity. 38,39 For TCNQ, a p-doping of graphene results from a charge transfer of about 0.03 electron per C atom of graphene to the TCNQ adlayer.…”