Spectroscopy of Covalently Functionalized Graphene

Abstract

In order to engineer a band gap into graphene, covalent bond-forming reactions can be used to change the hybridization of the graphitic atoms from sp 2 to sp 3 , thereby modifying the conjugation length of the delocalized carbon lattice; similar side-wall chemistry has been shown to introduce a band gap into metallic single-walled carbon nanotubes. Here we demonstrate that the application of such covalent bond-forming chemistry modifies the periodicity of the graphene network thereby introducing a band gap (∼0.4 eV), which is observable in the angle-resolved photoelectron spectroscopy of aryl-functionalized graphene. We further show that the chemically-induced changes can be detected by Raman spectroscopy; the in-plane vibrations of the conjugated π-bonds exhibit characteristic Raman spectra and we find that the changes in D, G, and 2D-bands as a result of chemical functionalization of the graphene basal plane are quite distinct from that due to localized, physical defects in sp 2 -conjugated carbon.

From highly graphitic to amorphous carbon dots: A critical review

“…The G peak is associated with the E 2g vibration mode of the sp 2 -bonded carbon and the D peak is assigned to the A 1g (zone-edge) breathing vibration phonon that becomes active only in close proximity to a sp 3 defect. 30 In a fi rst approximation, the intensity ratio of the D over G band is an index of the disordered carbon; the value I D / I G = 0.5 found here implies a high graphitization degree for the gC-dots. X-ray photoelectron spectroscopy (XPS) patterns of gC-dots are compared with the initial graphene electrode in Fig.…”

Sublattice-induced symmetry breaking and band-gap formation in graphene

“…There are various widely publicized approaches to engineering a band gap in graphene, such as strain engineering, 1-4 spatial restriction, for example via graphene nanoribbon fabrication, [5][6][7][8][9][10][11][12][13][14][15][16] controlling the density of electrons as in adsorbate hybridization, [17][18][19][20][21] and symmetry breaking, [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] typically as a result of substrate interactions. All have major aws when the goal is retention of the unique properties of graphene while opening a band gap.…”

Dibromocarbene Functionalization of Boron Nitride Nanosheets: Toward Band Gap Manipulation and Nanocomposite Applications

“…Analogous to studies involving graphene, where the band gap energy may be increased by doping and surface functionalization, [20][21][22] in case of BNNSs, an insulator with a band gap of 5.56 eV, 14 it has been predicted that covalent functionalization by carbene species may lower the band gap to 0.6 eV. 23 UV-Vis spectroscopy has been used by a number of authors to investigate the optical energy gap of h-BN thin films.…”