Pressure coefficients of Raman modes of carbon nanotubes resolved by chirality: Environmental effect on graphene sheet

Ghandour, AJa b; Crowe, Iain F.; Proctor, John E.; Sun, Yiwei; Halsall, Matthew P.; Hernandez, Ia e; Sapelkin, A.; Dunstan, D. J.

doi:10.1103/physrevb.87.085416

Cited by 20 publications

(30 citation statements)

References 27 publications

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“…Predictions of the pressure coefficient of the G-mode from graphene and graphite are not reliably fulfilled. Instead a great diversity of pressure coefficients is reported and attributed to diverse environmental effects and to variations of resonance conditions as the pressure is changed (see the discussion in Ghandour et al, 2012 [10], Ghandour et al 2013 [8]).…”

Section: Carbon Nanotubesmentioning

confidence: 99%

Nanomechanics of Carbon Nanotubes

Sun

Dunstan

Hartmann

et al. 2013

Proc Appl Math and Mech

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We discuss the mechanical properties of carbon nanotubes, in particular the pressure-dependence of the Raman modes and the collapse pressure, and their relation to the corresponding mechanical properties of graphite and graphene. The frequencies of the Raman G-mode and radial breathing mode (RBM), as well as the pressure dependence of the RBM can be largelyexplained in the existing framework of C-C stretching modes and envirionmental effects induced by the pressure medium. The pressure dependence of the G-mode is still missing such an explanation. The collapse pressure can be understood in terms of the continuum theory for thin-walled tubes.

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Section: Carbon Nanotubesmentioning

confidence: 99%

Nanomechanics of Carbon Nanotubes

Sun

Dunstan

Hartmann

et al. 2013

Proc Appl Math and Mech

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“…The results are shown as γ 0 and SDP in TA-BLE I. It is worth noticing that Ghandour et al pointed out that the transverse strain ε T =0 rather than ε T =-νε L , where ν is the in-plane Poisson's ratio and ε L is the longitudinal strain, in the case that uniaxial strain is applied by flexure of a beam to which a graphene flake adhered 17 . For graphite, when two adjacent graphene layers are considered, we can simply make two copies of Eq.…”

Section: Introductionmentioning

confidence: 96%

Graphite under uniaxial compression along thecaxis: A parameter to relate out-of-plane strain to in-plane phonon frequency

2015

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Stacking graphene sheets forms graphite. Two in-plane vibrational modes of graphite, E1u and E (2) 2g , are derived from the graphene E2g mode, the shifts of which under compression are considered as results of the in-plane bond shortening. Values of the Grüneisen parameter have been reported to quantify such relation. However, the reason why the shift rates of these three modes with pressure differ is unclear. In this work, we introduce new parameters γ E 2g =-0.0131 and γ E 1u =0.0585 to quantify the contribution of out-of-plane strain to the shift of the in-plane vibrational frequencies, suggesting that the compression of the π-electrons plays a non-negligible part in both graphite and graphene under high pressure.

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“…This is quite unlike the pressure dependence of RBM, which is due to the decrease of the distance between tube shell and the absorbed fluid layer and therefore unsurprisingly sensitive to the environment [29]. Second, according to the thick-wall tube model [12], the G + and G − pressure coefficients of 1.46 nm tubes should be 6.0 and 8.0 cm −1 GPa −1 respectively. The model is based on individual tubes but the G + values of i-SWCNTs are much higher than the predicted ones.…”

Section: Discussionmentioning

confidence: 93%

“…Ghandour et al attributed the disparity to the tube diameter and explained the diameter dependence of the GM pressure coefficients with a thick-wall tube model [12]. Such diameter dependence is expected, although the model itself is not perfect, requiring a lower graphene GM pressure coefficient than experimental value, and not taking recently reported chirality effects into account [13].…”

Section: Introductionmentioning

confidence: 99%

“…These are examples of close-ended tubes. The disparity comes both from the mixture of diameter and from environmental effects [12]-a specific environment (PTM, bundling and surfactants) and excitation wavelength picks out tubes of a certain diameter. A recent advance has been made in that experiments on CNTs in water enable the assignment of the observed GM pressure coefficients to tubes of particular chiralities (See Figure 1) [12].…”

Section: Introductionmentioning

confidence: 99%

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Significance of Bundling Effects on Carbon Nanotubes’ Response to Hydrostatic Compression

et al. 2016

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The study of the G-mode pressure coefficients of carbon nanotubes, reflecting the stiff sp 2 bond pressure dependence, is essential to the understanding of their extraordinary mechanical properties as well as fundamental mechanics. However, it is hindered by the availability of carbon nanotubes samples only as bundles or isolated with surfactants. Octadecylamine functionalized carbon nanotubes are mostly of a single diameter and can be stably dispersed in 1, 2-dichloroethane and chloroform without surfactants. Here we perform high pressure Raman spectroscopy on these tubes and obtain their experimental G-mode pressure coefficients for individual tubes and bundles. The G + pressure coefficient for bundles is only about half of that for individual tubes in 1, 2-dichloroethane and is about two-thirds in chloroform. The G − pressure coefficient for bundles is about one-third of G + in 1, 2-dichloroethane and about the same in chloroform. These results for the first time provide unambiguous experimental evidence of the significant effect of bundling on carbon nanotubes' G-mode pressure coefficients, identifying it as one of the major reasons for the lack of consensus on what the values should be in the literature.

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Pressure coefficients of Raman modes of carbon nanotubes resolved by chirality: Environmental effect on graphene sheet

Cited by 20 publications

References 27 publications

Nanomechanics of Carbon Nanotubes

Nanomechanics of Carbon Nanotubes

Graphite under uniaxial compression along thecaxis: A parameter to relate out-of-plane strain to in-plane phonon frequency

Significance of Bundling Effects on Carbon Nanotubes’ Response to Hydrostatic Compression

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