The present investigation concerns multiwalled carbon nanotubes synthesized on graphite cathodes by arcdischarge in a He atmosphere, either with the insertion of a catalytic Ni–Cr mixture or without catalysts.The morphology of the deposited cathodes was investigated by SEM, while the amount of carbon chainsinside multiwalled carbon nanotubes (C@MWCNT) in various regions of the deposited cathodes wasrevealed by a parallel micro-Raman study, through the analysis of the signal from the Raman bandsgenerated by C@MWCNT in the range 1780–1870 cm-1 (L bands). In samples obtained by using thecatalyst, a very high concentration of linear carbon chains is found in some zones, as indicated by the intensity of the L band, which turns out remarkably stronger than the G band of the host nanotubes. Inthese zones, the second-order Raman scattering is clearly observed, too. The experimental wavenumbervalues of the 2 L overtone are slightly lower than the exact doubling of the one-phonon peak wavenumber,and this fact is discussed in terms of the existing theoretical predictions for the chain-mode dispersioncurve.

The present investigation concerns multiwalled carbon nanotubes synthesized on graphite cathodes by arc discharge in a He atmosphere, either with the insertion of a catalytic Ni-Cr mixture or without catalysts. The morphology of the deposited cathodes was investigated by SEM, while the amount of carbon chains inside multiwalled carbon nanotubes (C@MWCNT) in various regions of the deposited cathodes was revealed by a parallel micro-Raman study, through the analysis of the signal from the Raman bands generated by C@MWCNT in the range 1780-1870 cm(-1) (L bands). In samples obtained by using the catalyst, a very high concentration of linear carbon chains is found in some zones, as indicated by the intensity of the L band, which turns out remarkably stronger than the G band of the host nanotubes. In these zones, the second-order Raman scattering is clearly observed, too. The experimental wavenumber values of the 2 L overtone are slightly lower than the exact doubling of the one-phonon peak wavenumber, and this fact is discussed in terms of the existing theoretical predictions for the chain-mode dispersion curve. Copyright (C) 2008 John Wiley & Sons, Ltd.

Second-order Raman scattering from linear carbon chains inside multiwalled carbon nanotubes

Cupolillo A;Castriota M;Cazzanelli E;Caputi L;Giallombardo C;Mariotto G;Papagno L
2008-01-01

Abstract

The present investigation concerns multiwalled carbon nanotubes synthesized on graphite cathodes by arcdischarge in a He atmosphere, either with the insertion of a catalytic Ni–Cr mixture or without catalysts.The morphology of the deposited cathodes was investigated by SEM, while the amount of carbon chainsinside multiwalled carbon nanotubes (C@MWCNT) in various regions of the deposited cathodes wasrevealed by a parallel micro-Raman study, through the analysis of the signal from the Raman bandsgenerated by C@MWCNT in the range 1780–1870 cm-1 (L bands). In samples obtained by using thecatalyst, a very high concentration of linear carbon chains is found in some zones, as indicated by the intensity of the L band, which turns out remarkably stronger than the G band of the host nanotubes. Inthese zones, the second-order Raman scattering is clearly observed, too. The experimental wavenumbervalues of the 2 L overtone are slightly lower than the exact doubling of the one-phonon peak wavenumber,and this fact is discussed in terms of the existing theoretical predictions for the chain-mode dispersioncurve.
2008
The present investigation concerns multiwalled carbon nanotubes synthesized on graphite cathodes by arc discharge in a He atmosphere, either with the insertion of a catalytic Ni-Cr mixture or without catalysts. The morphology of the deposited cathodes was investigated by SEM, while the amount of carbon chains inside multiwalled carbon nanotubes (C@MWCNT) in various regions of the deposited cathodes was revealed by a parallel micro-Raman study, through the analysis of the signal from the Raman bands generated by C@MWCNT in the range 1780-1870 cm(-1) (L bands). In samples obtained by using the catalyst, a very high concentration of linear carbon chains is found in some zones, as indicated by the intensity of the L band, which turns out remarkably stronger than the G band of the host nanotubes. In these zones, the second-order Raman scattering is clearly observed, too. The experimental wavenumber values of the 2 L overtone are slightly lower than the exact doubling of the one-phonon peak wavenumber, and this fact is discussed in terms of the existing theoretical predictions for the chain-mode dispersion curve. Copyright (C) 2008 John Wiley & Sons, Ltd.
multiwalled carbon nanotubes; raman spectroscopy
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11770/126978
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