Nanotubes Raman spectra

Fig. 23. Experimental room temperature Raman spectrum from a sample consisting primarily of bundles or ropes of single-wall nanotubes with diameters near that of the (10,10) nanotube. The excitation laser wavelength is 514.5 nm. The inset shows the lineshape analysis of the vibrational modes near 1580 cm . SWNT refers to singlewall carbon nanotubes [195].

Fig. 11. Raman spectrum (T = 300 K) of arc-derived carbons containing single-wall nanotubes generated in a Ni/Co-catalyzed dc arc (after ref. [42 ).

Raman scattering is one of the most useful and powerful techniques to characterize carbon nanotube samples. Figure 15.17 shows the Raman spectrum of a single SWNT [127]. The spectrum shows four major bands which are labeled RBM, D, G, and G. ... 

In another example [56] SWNT was modified with peroxytrifluoroacetic add (PTFAA). Raman spectrum of the carbon nanotubes after the FIFA A treatment shows a D-line substantially increased indicating the formation of defect sites with sp3-hybridized carbon atoms on the sidewalls due to the addition of the functional groups. The RBM bands in the region of 170-270cm-1 decreased and shifted to higher... 

With the aid of a bi-functionalized reagent (terminated with pyrenyl unit at one end and thiol group at the other end), gold nanoparticles were self-assembled onto the surface of solubilized carbon nanotubes [147], Raman spectrum of the gold nanoparticle bearing CNTs is enhanced possibly due to charge transfer interactions between nanotubes and gold nanoparticles. 

The thermal conductivity of suspended graphene has been calculated by measuring the frequency shift of the G-band in the Raman spectrum with varying laser power. These measurements yielded a value for thermal conductivity of 4840 5300 W m 1 K 1 [23], better than that of SWCNTs, with the exception of crystalline ropes of nanotubes, which gave values up to 5800 W m 1 K 1 [24]. Even when deposited on a substrate, the measured thermal conductivity is 600 W m 1 K 1 [25], higher than in commonly used heat dissipation materials such as copper and silver. 

Figure 4. Raman spectrum of multi-walled carbon nanotubes after purification recorded for kexc. = 676.4 nm [22], The low frequency modes have been calculated as explained in the text.

The Raman spectrum of HiPco SWNT obtained at the He-Ne laser excitation of 1.96 eV has three characteristic regions four bands in the low frequency region at 100-300 cm 1 (radial breathing mode (RBM)), two intensive bands at 1500-1600 cm 1 (tangential mode (G-mode)) of the spectrum and D mode (near 1300 cm"1) [14-18], At He-Ne laser excitation 4 intensive bands (RBM) are observed in Raman spectra of HiPCO nanotubes, corresponding to SWNTs of different diameters and chirality. 

The most significant change of the SWNT Raman spectrum due to the interaction with pyrene or naphthalene was observed in the intensity of the low-frequency component of the G mode (G), which decreased by about 16, 15 and % 30 for SWNT with PI, N and P2, respectively. To estimate the intensity of all the bands in the spectra, the bands were normalized to the most intensive G+ band in each spectrum. All these changes are the spectral manifestations of the complex formation between the nanotubes and the pyrene/naphthalene molecules. However, all the observed changes of the SWNT Raman spectrum are not strong. This was not unexpected because... 

SWNT interactions with different surfactants in aqueous solution result in changes in Raman spectra, as compared with spectra of a nanotube in films (Fig. 4). In this Figure two spectral intervals with bands corresponding to RBM and G mode are shown. Each Raman spectrum is normalized to the most intense band corresponding to the G-mode. The interaction with different surfactants leads to the intensity decrease and shift of lines attributed to the RBM. The essential changes in spectra are observed for this mode of SWNT in aqueous solutions with SDS. The intensity of the low-... 

Bulk HfSz is an indirect band gap semiconductor with au indirect band gap energy of 2.1 eV.67 The reflectance spectrum of the nanotubes shows a small blue shift compared with the bulk. The photoluminescence spectrum of the nanotubes shows a band at 676 nm due to trapped states, and the band is blue-shifted with respect to that of bulk HfS2 powder (see Fig. 21a). The Raman spectrum of the HfSz nanotubes is shown in Fig, 21b. It shows a band due to the Aiemode, corresponding to the S atom vibration along the c-axis perpendicular to the basal plane, and another due to the Eg mode due to the movement of the S and Hf atoms in the basal plane.68 The full-width at half maximum (FWHM) of the Alg band is 11 cm 1 in the nanotubes compared to 8 cm 1 for the bulk sample. Such broadening of the Raman band has been noted with MoS2 and WS2 nanotubes.19... 

In conclusion, the Mo0, Fe09Mg130 catalyst prepared by the combustion route preferentially yields DWNTs, the proportion of SWNTs being very small or negligible. The use of this catalyst has enabled the synthesis of 1 atom % N- and B-doped DWNTs. The diameters of the nanotubes obtained from the Raman RBM modes and transmission electron microscopy are comparable. The N-doped nanotubes show the G-band in the Raman spectrum at a lower frequency than the undoped ones, while the B-doped nanotubes show an increase in the frequency. The proportion of the metallic nanotubes appears to decrease on N- or 8-doping, but the average diameter is substantially larger in the B-doped DWNTs. 

Fig. 2 (a) Raman spectrum of BN nanotubes, (b) Raman spectra of the dispersions of BN nanotubes functionalized with tributylamine (1), trioctylamine (2) and trioctylphosphine (3). 

As a typical example, Figure 12.15 shows the Raman spectra of an unfilled ethylene-propylene-diene rubber (EPDM). The Raman spectra of pure MWNTs, pure CB and of a EPDM / MWNTs composite are also given. The D, G and G bands are respectively located at 1348, 1577 and 2684 cm-1 in the Raman spectrum of the multiwall carbon nanotubes. The Raman spectrum of pure carbon black (CB) remains dominated by the bands associated with the D and G modes at 1354 and 1589 cm1 respectively, even when the carbons do not have particular graphiting ordering (Figure 12.11). This fact has been widely discussed by Robertson (84) and Filik (85). Amorphous carbons are mixtures of sp3 (as in diamond) and sp2 (as in graphite) hybridised carbon. The it bonds formed by the sp2 carbons being more polarisable than the a bonds formed by the sp3 carbons, the authors conclude that the Raman spectrum is dominated by the sp2 sites. 

We have developed solvothermal synthesis as an important method in research of metastable structures. In the benzene-thermal synthesis of nanocrystalline GaN at 280°C through the metathesis reaction of GaClj and U3N, the ultrahigh pressure rocksalt type GaN metastable phase, which was previously prepared at 37 GPa, was obtained at ambient condition [5]. Diamond crystallites were prepared from catalytic reduction of CCI4 by metallic sodium in an autoclave at 700°C (Fig.l) [6]. In our recent studies, diamond was also prepared via the solvothermal process. In the solvothermal catalytic metathesis reaction of carbides of transition metals and CX4 (X = F, Cl, Br) at 600-700°C, Raman spectrum of the prepared sample shows a sharp peak at 1330 cm" (Fig. 1), indicating existence of diamond. In another process, multiwalled carbon nanotubes were synthesized at 350°C by the solvothermal catalytic reaction of CgCle with metallic potassium (Fig. 2) [7]. 

Telg H, Fouquet M, Maultzsch J, Wu Y, Chandra B, Hone J, Heinz TF, Thomsen C (2008) G and G in the Raman spectrum of isolated nanotube a study on resonance conditions and lineshape. Phys Status Solidi B 245(10) 2189-2192... 

Figure 3.40 Separation of metallic and semiconducting carbon nanotubes by AC dielectrophoresis. (a) Scheme of the installation, and (b) Raman spectrum of a metallic sample in comparison to the starting material as reference ( AAAS 2003).

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