Concentric carbon structures

Pasqualini, E.

doi:10.1103/physrevb.56.7751

Cited by 14 publications

(7 citation statements)

References 15 publications

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“…The MW (or concentric) [81] nanotubes and nano-onions represent 'radial superlattices' as opposed to the usual 'translational superlattices'. Nanocones are also known to be MW.…”

Section: Complex Geometries and Higher Genus Topological Structuresmentioning

confidence: 99%

Nanocarbon materials: probing the curvature and topology effects using phonon spectra

Gupta

Saxena

2009

J Raman Spectroscopy

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Much has been learned from the use of resonance Raman spectroscopy and high-resolution transmission electron microscopy techniques about the micro-/nanoscopic structure of various nanostructured carbons. However, they still possess some features that are not entirely understood particularly in terms of topological characteristics, which go beyond making a distinction with just the geometrical structure at nanoscale. To effectively utilize the potential of these materials for technological needs, understanding both the geometrical and topological structure and perhaps relating these attributes to physical (optical/electronic, lattice vibrational) properties become indispensable. Here, we make an attempt to describe the differences between various nanostructures and provide geometrical and topological property assessment semiquantitatively by monitoring the phonon spectra using resonance Raman spectroscopy thereby also capturing the electronic spectra. We elucidate the notion of global topology and curvature for a range of technologically important nanoscale carbons including tubular (single-, double-and multiwalled nanotubes, peapod), spherical (hypo-and hyperfullerenes, onion-like carbon) and complex (nanocones, nanohorns, nanodisks and nanorings) geometries. To demonstrate the proof-of-concept, we determined the variation in the prominent Raman bands of the respective materials, represented as D, G and D * (the overtone of D) bands, as a possible topological or curvature trend due to their sensitivity toward structural modification. The latter arises from local topological defects such as pentagons giving rise to curved nanocarbons. In this study, we provide systematics of their variation with respect to their geometric forms and compare with highly oriented pyrolytic graphite and monolayer graphene since the nanocarbons discussed are their derivatives. Once established, this knowledge will provide a powerful machinery to understand newer nanocarbons and indeed point to an unprecedented emergent paradigm of global topology/curvature → property → functionality relationship. We emphasize that these concepts are applicable to other topologically distinct nanomaterials, which include boron-nitride (BN) nanotubes and nanotori, helical gold nanotubes and Möbius conjugated organics. Copyright

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“…The MW (or concentric) [81] nanotubes and nano-onions represent 'radial superlattices' as opposed to the usual 'translational superlattices'. Nanocones are also known to be MW.…”

Section: Complex Geometries and Higher Genus Topological Structuresmentioning

confidence: 99%

Nanocarbon materials: probing the curvature and topology effects using phonon spectra

Gupta

Saxena

2009

J Raman Spectroscopy

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“…The repeated observations of spherical onion shells as opposed to the predicted Goldberg polyhedra with protrusions along and around the pentagonal defects [5][6][7] have warranted an explanation. Some authors [8,9] have provided results from topological arguments to show that the spherical shell structure is more stable. The formation of closed carbon cages in a cluster-forming environment has been extensively studied [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Continuum elastic model of fullerenes and the sphericity of the carbon onion shells

Ahmad

2002

The Journal of Chemical Physics

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A continuum elastic model of fullerenes is presented by utilizing the analogy between the closed carbon cages and elastic shells. We derive expressions for the curvature related strain energies Ep of the pentagonal protrusions. We propose to explain the observed sphericity of the carbon onions shells as opposed to the predicted protrusions around the pentagonal defects on the basis of our continuum elastic model of fullerenes. In our model the energy inherent in the pentagonal protrusions Ep is due to the stretching and bending of the shell and shown to be a function of the structural parameters. It also defines the upper limit on the size of the free-standing fullerenes. Using Ep and the topological arguments, we show that the pentagonal protrusions will be smoothed out, resulting in spherical shells of the carbon onions denoted as C60@C240@C540@C960@C1500 ,... .

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“…On the other hand, non-equal peak breaths were also observed in the low resolution x-ray diffraction (XRD) data from the existing literature [11,[17][18][19][20], and from a recent neutron diffraction experiment [21], where the (004) peaks were found to be wider than (002). Although this could also be attributed to the lattice distortion, it produces a much higher layer number [19].…”

Section: Resultsmentioning

confidence: 69%

“…In some cases the sample purity was about 60% [19]. Although most of them found no strong (101) peak, due presumably to the expected misalignment between the graphite layers, the works of Pasqualini [20] and Burian et al [21] suggested that it is possible to have lateral correlation. Therefore, it is likely that they exist in the samples of high purity.…”

Section: Resultsmentioning

confidence: 97%

Nano-Cylinder Structure Studied by X-ray Diffraction

Feng

Popović

et al. 2001

MRS Proc.

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The study of nano-cylinder structure has attracted much attention due to the application of multi-wall carbon nanotubes (MWCNTs). While some TEM observations indicate that they are formed by seamless concentric cylinders, other TEM and high pressure X-ray diffraction studies suggest that they look like scrolls of graphite sheets. Although many people now accept the concentric cylinder model, there has been no confirmation reported. On the other hand, this structural difference of MWCNTs plays a crucial role in determining the properties and suitability for future applications. For example, the periodical boundary condition can only be imposed for cylinders, but not for scrolls. To resolve this issue, we employed high-resolution X-ray diffraction to measure detailed profiles of the Bragg peaks for high-purity MWCNTs. We then identified some unusual observations unique to the nano-cylinder structure, followed by the analysis of the structural difference in the Fourier transform between nanotubes formed by scrolls and concentric cylinders. The simulation results are then compared with the experimental data to reveal the structural details.

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Concentric carbon structures

Cited by 14 publications

References 15 publications

Nanocarbon materials: probing the curvature and topology effects using phonon spectra

Nanocarbon materials: probing the curvature and topology effects using phonon spectra

Continuum elastic model of fullerenes and the sphericity of the carbon onion shells

Nano-Cylinder Structure Studied by X-ray Diffraction

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