ABSTRACT
A curved graphene ribbon corresponds to an unzipped carbon nanotube. The systematic studies have been made for the latter since the successful synthesis using the arc-discharge evaporation in 1991, such as synthesis, characterization, property and application. The essential properties of curved graphene nanoribbons without extra termination hydrogen atoms are elaborated. The unzipped and zipped graphene nanoribbons are quite different from each other, mainly owing to the curvature effect and the open and periodical boundary condition. Armchair and zigzag carbon nanotubes are very different from zigzag and armchair graphene nanoribbons in the main features of electronic properties. The edge- atom-dominated energy bands are absent in carbon nanotubes, and each energy band is equally contributed by carbon atoms on a cylindrical surface. The variation of the band structure and DOS with the curvature is investigated thoroughly. The calculated results clearly indicate the unusual features of energy band, such as energy gap, energy dispersions, band-edge states, mixing bands, band overlap, and state degeneracy.
