title: Size, structure, and helical twist of graphene nanoribbons controlled by confinement in carbon nanotubes.
abstract: Carbon nanotubes (CNTs) act as efficient nanoreactors, templating the assembly of sulfur-terminated graphene nanoribbons (S-GNRs) with different sizes, structures, and conformations. Spontaneous formation of nanoribbons from small sulfur-containing molecules is efficiently triggered by heat treatment or by an 80 keV electron beam. S-GNRs form readily in CNTs with internal diameters between 1 and 2 nm. Outside of this optimum range, nanotubes narrower than 1 nm do not have sufficient space to accommodate the 2D structure of S-GNRs, while nanotubes wider than 2 nm do not provide efficient confinement for unidirectional S-GNR growth, thus neither can support nanoribbon formation. Theoretical calculations show that the thermodynamic stability of nanoribbons is dependent on the S-GNR edge structure and, to a lesser extent, the width of the nanoribbon. For nanoribbons of similar widths, the polythiaperipolycene-type edges of zigzag S-GNRs are more stable than the polythiophene-type edges of armchair S-GNRs. Both the edge structure and the width define the electronic properties of S-GNRs which can vary widely from metallic to semiconductor to insulator. The encapsulated S-GNRs exhibit diverse dynamic behavior, including rotation, translation, and helical twisting inside the nanotube, which offers a mechanism for control of the electronic properties of the graphene nanoribbon via confinement at the nanoscale.
authors.affiliation: School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Chamberlain
authors.forename: Johannes
authors.initials: J
authors.lastname: Biskupek
authors.forename: Graham A
authors.initials: GA
authors.lastname: Rance
authors.forename: Andrey
authors.initials: A
authors.lastname: Chuvilin
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Alexander
authors.forename: Elena
authors.initials: E
authors.lastname: Bichoutskaia
authors.forename: Ute
authors.initials: U
authors.lastname: Kaiser
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Khlobystov