Computational study of the shift of the G band of double-walled carbon nanotubes due to interlayer interactions

Abstract

The interactions between the layers of double-walled carbon nanotubes induce measurable shift of the G bands relative to the isolated layers. While experimental data on this shift in free-standing double-walled carbon nanotubes has been reported in the past several years, comprehensive theoretical description of the observed shift is still lacking. The prediction of this shift is important for supporting the assignment of the measured double-walled nanotubes to particular nanotube types. Here, we report a computational study of the G-band shift as a function of the semiconducting inner layer radius and interlayer separation. We find that with increasing interlayer separation, the G band shift decreases, passes through zero and becomes negative, and further increases in absolute value for the wide range of considered inner layer radii. The theoretical predictions are shown to agree with the available experimental data within the experimental uncertainty.

Few-Wall Carbon Nanotube Coils

“…This splitting is attributed to interwall interactions within one FWCNT, where the G + mode of the inner (outer) wall shifts to a smaller (higher) frequency relative to the position in an isolated single-wall CNT. 35,45,46 This indicates that the Raman signals belong to the walls of a FWCNT, rather than to separate SWCNTs. 35,45 Overall, we imaged 14 coils by Raman spectroscopy, for 7 of which we could detect a G + mode splitting.…”

Nanotube‐Based 1D Heterostructures Coupled by van der Waals Forces

“…[42] Liu et al [19] compared the vdW interaction strength in DWCNTs with the vdW coupling between unit-area graphene sheets under pressure obtained from compressibility measurements of graphite and showed that the effective pressure between the walls of as-grown DWCNTs reaches GPa (upper scale in Figure 4a). Later, Popov et al [58] demonstrated that this effective pressure results from structural optimization of DWCNT layers, leading to radius changes (expansion/compression) as a function of both the diameter and the interlayer distance (Figure 4b). It is interesting to note that DWCNTs with Δr > 0.34 nm allow readily accessing a negative pressure on inner SWCNTs in the GPa range, which is difficult to achieve using conventional approaches.…”

“…Reproduced with permission. [58] Copyright 2018, American Physical Society. c) Raman spectrum for an individual (15,13)@(31,4) DWCNT, revealing the strong blue-shifted of DWCNT RBM frequencies from those of the constituent SWCNTs (dashed lines).…”

“…b) Calculated pressure-induced change of the innertube radius of DWCNTs, R i , for DWCNTs with given R i from 3.7 to 11.2 Å and different outer-tube radius R o . Reproduced with permission [58]. Copyright 2018, American Physical Society.…”

Особенности углеродных нанотрубок, синтезированных из метана и ацетилена при использовании катализатора FeCl-=SUB=-3-=/SUB=-

“…И поскольку частота G-моды напрямую зависит от длины связи C−C, наблюдаемое явление может иметь несколько возможных объяснений. Вопервых, длина связи C−C чувствительна к изменению межслоевого расстояния в МУНТ [17,18]: чем меньше межслоевое расстояние, тем выше оказывается частота G-моды. Во-вторых, влияние на связь C−C также может оказываться посредством допирования [14,19,20] и явления переноса заряда [21], что в нашем случае может происходить за счет частиц катализатора.…”