Chemical Modification of Epitaxial Graphene: Spontaneous Grafting of Aryl Groups

Abstract

The addition of nitrophenyl groups to the surface of few-layer epitaxial graphene (EG) by the formation of covalent carbon-carbon bonds changed the electronic structure and transport properties of the EG from near-metallic to semiconducting.

Janus graphene from asymmetric two-dimensional chemistry

“…3b and Supplementary Fig. S9) centred at 406.2 eV (labelled by * and assigned to nitro groups 23,24 ), confirming the presence of nitro phenyl groups on Janus graphene. The lower N1s peaks is associated with the presence of reduced nitrogen species introduced by the transferring procedure and may be due to transformation of the nitro groups by X-ray irradiation in the XPS spectrometer chamber 49 .…”

“…XPS survey, the evolution of Raman spectra, and surface wettability measurements confirm that the fluorine and oxygen Figs S6,S7). Here, we show another example by using diazotization of graphene in the second step of functionalisation, in view of its simplicity and versatility [23][24][25]27 . Peeled mediator embedding chlorinated graphene was submerged into B20 mM diazonium salt (4-nitrobenzene diazonium tetrafluoroborate) aqueous solution for 1-2 h at 40 o C without stirring, allowing only the exposed surface to react and undergo surface functionalisation to form covalently bonded aryl-substituents.…”

“…The recorded XPS N1s spectra (Fig. 3b) showed a single peak centred at 399.2 eV after 5 h reduction, assigned to the amino group nitrogen 24 . The reduction of surface functionalities was also confirmed by the evolution of surface wettability ( Supplementary Fig.…”

“…Physisorption of chemical species on graphene would provide a facile way to alter its electronic properties 12 , however, covalent chemical modification shows a great advantage in achieving permanent stabilisation for long-term usage 13 . Previous attempts towards fundamental research on covalent functionalisation of graphene mainly involved the development of new modification strategies (for example, hydrogenation [14][15][16][17] , fluorination [18][19][20] , chlorination 21,22 , diazotization [23][24][25][26][27] and other cycloaddition reactions [28][29][30][31] ), covalent addition of edge and defects 27,32 , fabrication of chemical superlattices 26,33 and quantum effects in graphene modification 17,34 . Of the various significant research activities on graphene chemistry that have been conducted, nearly no work to date has been focused on the asymmetric chemistry of this ideal 2D atomic crystal via covalently attaching different functional groups on its two faces simultaneously.…”

Aryl Functionalization as a Route to Band Gap Engineering in Single Layer Graphene Devices

“…Here we report the successful aryl-group functionalization 26 and transport measurements of single layer graphene sheets that are isolated in the form of free-standing films or supported on Si/SiO 2 substrates. Functionalization of graphene is verified by the development of D and D* peaks in Raman spectroscopy measurements 27,28 .…”