The article of record as published may be located at http://dx.doi.org/10.1002/smll.201401034
The use of carbon nanotubes (CNTs) as cylindrical reactor vessels has become a
viable means for synthesizing graphene nanoribbons (GNRs). While previous
studies demonstrated that the size and edge structure of the as-produced GNRs are
strongly dependent on the diameter of the tubes and the nature of the precursor, the
atomic interactions between GNRs and surrounding CNTs and their effect on the
electronic properties of the overall system are not well understood. Here, it is shown
that the functional terminations of the GNR edges can have a strong infl uence on the
electronic structure of the system. Analysis of SWCNTs before and after the insertion
of sulfur-terminated GNRs suggests a metallization of the majority of semiconducting
SWCNTs. This is indicated by changes in the radial breathing modes and the D and
G band Raman features, as well as UV–vis–NIR absorption spectra. The variation
in resonance conditions of the nanotubes following GNR insertion make direct
(n,m) assignment by Raman spectroscopy diffi cult. Thus, density functional theory
calculations of representative GNR/SWCNT systems are performed. The results
confirm significant changes in the band structure, including the development of a
metallic state in the semiconducting SWCNTs due to sulfur/tube interactions. The
GNR-induced metallization of semiconducting SWCNTs may offer a means of
controlling the electronic properties of bulk CNT samples and eliminate the need for
a physical separation of semiconducting and metallic tubes.
This work was supported by the Research Initiation Program of NPS’ Offi ce of Research, ONR grant N0001414WX00160, the EPSRC, ERC, Royal Society and Nottingham Nanoscience and Nanotechnology Centre.