Discriminative modulation of the highest occupied molecular orbital energies of graphene and carbon nanotubes induced by charging.

The highest occupied molecular orbital (HOMO) energies of carbon nanotubes (CNTs) and graphene are crucial in fundamental and applied research of carbon nanomaterials, and so their modulation is desired. Our first-principles calculations reveal that the HOMO energies of CNTs and graphene can both be raised by negatively charging, and that the rate of increase of the HOMO energy of a CNT is much greater and faster than that of graphene with the same number of C atoms. This discriminative modulation holds true regardless of the number of C atoms and the CNT type, and so is universal. This work provides a new opportunity to develop all-carbon devices with CNTs and graphene as different functional elements.