Linking Stability of Single-Walled Carbon Nanotubes with Growth Products

• Many of the envisioned products and technologies using single-walled carbon nanotubes (SWCNTs) are only possible with a uniform product. Thus, control over the chirality during catalytical chemical vapor deposition (CCVD) growth of SWCNTs is necessary. Our highlighted works1,2 focuses on stabilities of SWCNTs and how that relates to growth, in order to reach the ultimate goal of chirality-specific growth. In ref.1 density functional theory (DFT) has been used to calculate the stability of SWCNT-fragments of all chiralities in the (n+m) = 8 to 18 series. The fragment stabilities are compare to the chiralities of actual CCVD products from all properly analysed experiments to date. The results show that in 84% of the cases the experimental products represent chiralities among the most stable SWCNT-fragments (within 0.2 eV) from the calculations. The analysed products from growth experiments show that diameters of SWCNTs are governed by the well-known relation to the size of the catalytic particle and that the specific chirality of SWCNT products are strongly dependent on the stability of the tubes within each series, suggesting thermodynamic control at the early stage of growth. Analysis of the relative energy show that for the lower series 8 to 10, zigzag SWCNTs are the most stable and for the higher series 11 to 18 the most stable chirality changes from zigzag to armchair. This switch in stability between armchair and zigzag chiralities is studied further in ref.2, where DFT was used to calculate the stability of armchair and zigzag SWCNTs and graphene nanoribbons (GNRs) of different lengths. The calculations show that the stability of armchair and zigzag tubes has different linear dependence with regard to their length, with switches in the most stable chirality occurring at specific lengths for each SWCNT-series. These dependencies are explained by competing edge and curvature energies. Within each series armchair nanotubes are the most stable at short lengths, while zigzag nanotubes are the most stable at long lengths, this sheds new light into why armchair and near-armchair tubes are the dominant product from CCVD growth, if templating is not used. Paradoxically, the stability of armchair nanotubes at short lengths favors their growth although zigzag nanotubes are more stable at long lengths, resulting in the production of the least stable SWCNTs.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)

NATURVETENSKAP  -- Fysik -- Annan fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Other Physics Topics (hsv//eng)

Nyckelord

Single-walled carbon nanotubes

Density functional theory

Chirality-specific growth

Stability

Applied Physics

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