Single-walled Carbon Nanotube
Growth from Chiral Carbon
Nanorings: Prediction of Chirality and Diameter Influence on Growth
Rates
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Abstract
Catalyst-free, chirality-controlled growth of chiral
and zigzag
single-walled carbon nanotubes (SWCNTs) from organic precursors is
demonstrated using quantum chemical simulations. Growth of (4,3),
(6,5), (6,1), (10,1) and (8,0) SWCNTs was induced by ethynyl radical
(C<sub>2</sub>H) addition to organic precursors. These simulations
show a strong dependence of the SWCNT growth rate on the chiral angle,
θ. The SWCNT diameter however does not influence the SWCNT growth
rate under these conditions. This agreement with a previously proposed
screw-dislocation-like model of transition metal-catalyzed SWCNT growth
rates [Ding, F.; Proc.
Natl. Acad. Sci. 2009, 106, 2506] indicates that the SWCNT growth rate is
an intrinsic property of the SWCNT edge itself. Conversely, we predict
that the rate of SWCNT growth <i>via</i> Diels–Alder
cycloaddition of C<sub>2</sub>H<sub>2</sub> is strongly influenced
by the diameter of the SWCNT. We therefore predict the existence of
a maximum growth rate for an optimum diameter/chirality combination
at a given C<sub>2</sub>H/C<sub>2</sub>H<sub>2</sub> ratio. We also
find that the ability of a SWCNT to avoid defect formation during
growth is an intrinsic quality of the SWCNT edge