Molecular Dynamics of Chirality Definable Growth of Single-Walled Carbon Nanotubes

Abstract

In order to achieve the chirality-specific growth of single-walled carbon nanotubes (SWCNTs), it is crucial to understand the growth mechanism. Even though many molecular dynamics (MD) simulations have been employed to analyze the SWCNT growth mechanism, it has been difficult to discuss the chirality determining kinetics because of the defects remaining on the SWCNTs grown in simulations. In this study, we demonstrate MD simulations of defect-free SWCNTs, that is, chirality definable SWCNTs, under the optimized carbon supply rate and temperature. The chiralities of the SWCNTs were assigned as (14,1), (15,2), and (9,0), indicating the preference of near-zigzag and pure-zigzag SWCNTs. The SWCNTs contained at least one complete row of defect-free walls consisting of only hexagons. The near-zigzag SWCNTs grew via a kink-running process, in which bond formation between a carbon atom at a kink and a neighboring carbon chain led to formation of a hexagon with a new kink at the SWCNT edge. Defects including pentagons and heptagons were sometimes formed but effectively healed into hexagons on metal surfaces. The pure-zigzag SWCNTs grew by the kink-running and the hexagon nucleation processes. In addition, chirality change events along SWCNTs with incorporation of pentagon–heptagon pair defects were observed in the MD simulations. Here, pentagons and heptagons were frequently observed as adjacent pairs, resulting in (n,m) chirality changes by (±1,0), (0,±1), (1,–1), or (−1,1).

Chirality Pure Carbon Nanotubes: Growth, Sorting, and Characterization

“…268 A recent MD simulation by Maruyama et al showed that an adjacent pair of pentagon− heptagon changes the chirality to (0,±1), (±1,0), (−1,1), or (1,−1). 269 The chirality change will be greater, (0,±2), (0,±3), and so on, if the pentagon is away from heptagon. How to achieve a single dominant (n,n − 1) species is still a mystery because it is very difficult to control the number of pentagon− heptagon pairs and their locations.…”

“…However, there are at least six possibilities of ( n , m ) switching, including ( n , m ± 1), ( n ± 1, m ), ( n + 1, m – 1), and ( n – 1, m + 1), when an adjacent pair of pentagon–heptagon is incorporated in a tube . A recent MD simulation by Maruyama et al showed that an adjacent pair of pentagon–heptagon changes the chirality to (0,±1), (±1,0), (−1,1), or (1,–1) . The chirality change will be greater, (0,±2), (0,±3), and so on, if the pentagon is away from heptagon.…”

Emerging Internet of Things driven carbon nanotubes-based devices

“…The growth mechanism of SWCNTs involving aspects of thermodynamics and kinetics revealed by computer [83,84,[110][111][112][113][114][115] and in-situ techniques [85,86,[116][117][118][119][120][121][122][123][124] became clearer. As to chirality-based sorting, Kataura et al demonstrated industrial-scale separation of high-purity, single-chirality SWNTs by using mixedsurfactant gel chromatography [125] and the separation of 12 different single-chirality enantiomers with high enantiomeric purity [126].…”

Precise Synthesis of Carbon Nanotubes and One‐Dimensional Hybrids from Templates†

“…[ 24,26,130 ] It was reported that any defects such as the pentagon‐heptagon pair in a SWCNT will change the local chirality. [ 131‐133 ] When disturbing the growth parameters during CVD, such as changing carbon feeding stocks [ 88,134 ] and introducing an electric field, [ 135 ] the as‐grown SWCNTs exhibited heterojunctions with different chiralities. With this strategy, the SWCNTs with high‐ purity electronic type [ 135 ] and specific chirality were obtained.…”