Abstract
Double-wall carbon nanotubes are the molecular analogues to coaxial cables. Narrowdiameter double-walled carbon nanotubes (DWNTs) have been obtained by catalyticchemical vapour deposition process with high yield and characterized by scanning andtransmission electron microscopy. We examine the inelastic light scattering spectrum ofmostly DWNTs with internal tubes of subnanometre diameter. We observe particularlynarrow radial breathing modes corresponding to the internal tubes of diameter lessthan 0.7 nm of double-walled tubes. The D band is found to be strongly helicitydependent and the tangential modes in narrow diameter DWNTs are found to be oftendown-shifted.
Highlights
The electronic properties of carbon nanotubes depend on the orientation of the honeycomb lattice with respect to the tube axis
We present in this paper the synthesis, structural characterization and vibrational spectra of narrow diameter Double-walled carbon nanotubes (DWNTs)
We have described the synthesis of narrow diameter DWNTs
Summary
The electronic properties of carbon nanotubes depend on the orientation of the honeycomb lattice with respect to the tube axis (helicity). Double-walled tubes were observed by Laurent et al [3] during the decomposition of methane on iron catalysts generated in situ during the reduction of a solid solution of iron and aluminium oxides In this process, a mixture of single- and double-walled tubes was obtained. At low Raman shifts (50– 450 cm−1) a radial symmetric breathing mode is observed for nanotubes whose energy is inversely proportional to the diameter (ω ∝ 1/d) [10]. This means that, as the diameter of the tube gets smaller, the sensitivity of this mode to the diameter can become very high. The D band is found to be strongly helicity dependent and the tangential modes in narrow diameter DWNTs are found to be often down-shifted
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