Accurate determination of the chiral indices of individual carbon nanotubes by combining electron diffraction and Resonant Raman spectroscopy

Abstract

The experimental approach combining high resolution transmission electron microscopy (HRTEM), electron diffraction (ED) and resonant Raman spectroscopy (RRS) on the same freestanding individual carbon nanotubes (CNT) is the most efficient method to determine unambiguously the intrinsic features of the Raman-active phonons. In this paper, we review the main results obtained by the approach regarding the intrinsic features of the phonons of singlewalled (SWNT) and double-walled carbon nanotubes (DWNT). First, we detail the different methods to identify the structure of SWNTs and DWNTs from the analysis of their electron diffraction patterns (EDP). In the following, we remind the principal features of the Raman response of SWNTs, unambiguously index-identified by ED. A special attention is devoted to the effect of the inter-layer interaction on the frequencies of the Raman-active phonons in indexidentified DWNTs. The information obtained on index-identified SWNT and DWNT allows us to propose Raman criteria, which help identifying CNT when the ED fails to propose a single assignment. The efficiency of the Raman criteria as the complement to the ED information for the index-assignment of a few SWNTs and DWNTs is shown. The same approach to index-assign a triple-walled carbon nanotube (TWNT), by combining ED and RRS information, is reported.

Interlayer Interaction Effects on the G Modes in Double‐Walled Carbon Nanotubes With Different Electronic Configurations

“…Now we explore the dependence of the G‐modes frequencies on the diameter and inter‐layer distance. Recently, this behavior have been studied in SC@SC DWNTs . In brief, the TO (G− component) and LO (G+ component) frequencies of the inner layer shift significantly in SC DWNTs with respect to the frequencies of the same modes in each constituent SWNT.…”

“…The direction and values of the shift depend on the inter-layer distance. [7] To complete these previous investigations, we plot in Figure 2a As expected with regards to the average diameters of these three DWNTs, the in-phase and the out-of-phase RBLMs have similar frequencies, namely: 131/ 186 cm À1 for the (12,8)@ (16,14), 132/183 cm À1 for the (16,2)@ (16,14) and 134/187 cm À1 for the third individual DWNT.…”

“…[21] Hence, the presence of the TO mode is not apparent in the Raman spectra excited at 2.33 eV (Figure 1), and is detectable only at certain excitation energies in the red (1.96 eV). On the other hand, the Raman spectrum of the outer metallic (15,12) layer is dominated by a broad and asymmetric BWF component located at 1570(82) cm À1 (LO mode) and a Lorentzian component observed at 1594 (7) cm À1 (TO mode). The small symmetrical line at 1580 cm À1 is ascribed to the LO mode of the inner semiconducting layer.…”

Silica‐Mediated Formation of Nickel Sulfide Nanosheets on CNT Films for Versatile Energy Storage

“…In the Raman spectra, two intense peaks can be found for all the materials at around 1345 and 1581 cm −1 , corresponding to the D‐band and G‐band of CNTs, respectively (Figure h) . Remarkably, all the samples possess very high intensity ratios of the bands ( I G / I D ), between 2.24 and 3.35, indicating high graphitization of the CNTs and the expectation of excellent conductivity, which is highly desirable for fast electron transfer to support rapid redox processes . In addition, there are also two identifiable peaks in the low wavenumber range, at about 160 and 280 cm −1 (Figure h inset), which can be reasonably attributed to single/few‐walled CNTs with small diameters .…”

Direct Chirality Recognition of Single‐Crystalline and Single‐Walled Transition Metal Oxide Nanotubes on Carbon Nanotube Templates

“…For one‐dimensional (1D) tubular structures, such as carbon nanotubes (CNTs), their tunable electrical, thermal, mechanical, and optical properties are fundamentally related to the defined chirality. And, the chirality recognition of CNTs, for example, is still rigorous and challenging, which usually requires complex electron diffraction, Raman/Rayleigh scattering analysis, or high‐resolution observation in very carefully prepared samples . To obtain outstanding CNT‐based devices, hard efforts were made to achieve the controlled growth of homochiral CNTs using designed catalysts .…”