Deoxidation of graphene oxide nanosheets to extended graphenites by “unzipping” elimination

Abstract

Low-temperature scanning tunneling microscopy on alkyl-surface-functionalized graphene oxide nanosheets reveals the formation of low-dimensional graphenite nanostructures with extended pi-conjugation at deoxidation temperatures above 150 degrees C. The elimination of these alkyl chains from the surface of the nanosheets does not occur uniformly, but in distinctive patterns that correspond to the formation of an underlying network of graphenite one-dimensional "tracks" and "dots." Atomic-resolution imaging of these graphenite regions reveals a defective honeycomb lattice characteristic of single-layer graphenes. These extended graphenite structures percolate the nanosheet even for moderate levels of deoxidation and regraphenization of the basal plane. The formation of extended conjugation indicates a regioselective rather than random elimination of the oxygen atoms and alkyl chains. The resultant network morphology allows bandlike transport of charge carriers across the sheets despite defects and disorder. The sub-meV apparent activation energies for the field-effect mobilities at low temperatures (70-30 K) for both electrons and holes rule out significant electron-phonon coupling. This suggests a remarkable potential for electronic applications of these solution-processable functionalized graphene oxide nanosheets.