Graphene covalently binding aryl groups: conductivity increases rather than decreases.

Graphene functionalized via nitrophenyl groups covalently bonding to its basal plane is studied by Raman spectroscopy and electric transport measurements. The Raman spectra of functionalized graphene exhibit D mode and peaks derived from nitrophenyl groups, and the two fingerprints exhibit nearly the same distribution in the two-dimensional Raman maps over the whole graphene sheet. This result directly proves that the nitrophenyl groups bond to the graphene basal plane via σ-bonds. Electric transport measurements demonstrate that the modified graphene is significantly more conductive than intrinsic graphene. In the competition between charge transfer effect and scattering effect introduced by the nitrophenyl groups, the former one is dominant so that the conductivity of functionalized graphene is significantly enhanced as a result.