Issue 34, 2011
From the journal:

Physical Chemistry Chemical Physics

Thermal annealing of SiC nanoparticles induces SWNT nucleation: evidence for a catalyst-independent VSS mechanism†

Alister J. Page,a   K. R. S. Chandrakumar,a   Stephan Irle*b  and  Keiji Morokuma*ac  

* Corresponding authors

a Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
E-mail: alisterpage@fukui.kyoto-u.ac.jp, krsc@fukui.kyoto-u.ac.jp

b Institute for Advanced Research and Department of Chemistry, Nagoya University, Nagoya 464-8602, Japan
E-mail: sirle@iar.nagoya-u.ac.jp

c Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, USA
E-mail: keiji.morokuma@emory.edu

Abstract

Density-functional tight-binding molecular dynamics (DFTB/MD) methods were employed to demonstrate single-walled carbon nanotube (SWNT) nucleation resulting from thermal annealing of SiC nanoparticles. SWNT nucleation in this case is preceded by a change of the SiC structure from a crystalline one, to one in which silicon and carbon are segregated. This structural transformation ultimately resulted in the formation of extended polyyne chains on the SiC nanoparticle surface. These polyyne chains subsequently coalesced, forming an extended sp2-hybridized carbon cap on the SiC nanoparticle. The kinetics of this process were enhanced significantly at higher temperatures (2500 K), compared to lower temperatures (1200 K) and so directly correlated to the surface premelting behavior of the nanoparticle structure. Analysis of the SiC nanoparticle Lindemann index between 1000 and 3000 K indicated that SWNT nucleation at temperatures below 2600 K occurred in the solid, or quasi-solid, phase. Thus, the traditional vapor–liquid–solid mechanism of SWNT growth does not apply in the case of SiC nanoparticles. Instead, we propose that this example of SWNT nucleation constitutes evidence of a vapor–solid–solid process. This conclusion complements our recent observations regarding SWNT nucleation on SiO2 nanoparticles (A. J. Page, K. R. S. Chandrakumar, S. Irle and K. Morokuma, J. Am. Chem. Soc., 2011, 133, 621–628). In addition, similarities between the atomistic SWNT nucleation mechanisms on SiC and SiO2 catalysts provide the first evidence of a catalyst-independent SWNT nucleation mechanism with respect to ‘non-traditional’ SWNT catalyst species.

Graphical abstract: Thermal annealing of SiC nanoparticles induces SWNT nucleation: evidence for a catalyst-independent VSS mechanism

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Article information

DOI
https://doi.org/10.1039/C1CP21236B
Article type
Paper
Submitted
19 Apr 2011
Accepted
01 Jul 2011
First published
25 Jul 2011

Phys. Chem. Chem. Phys., 2011,13, 15673-15680

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Thermal annealing of SiC nanoparticles induces SWNT nucleation: evidence for a catalyst-independent VSS mechanism

A. J. Page, K. R. S. Chandrakumar, S. Irle and K. Morokuma, Phys. Chem. Chem. Phys., 2011, 13, 15673 DOI: 10.1039/C1CP21236B

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