Radial breathing modes

At 186 cm a strong line is seen in Fig. 23. This feature is identified with the Alp radial breathing mode and depends only on the nanotube diameter. The linewidth and lineshape is due to contributions from nanotubes of different... 

Modified CNTs feature various spectral changes depending on the methods and the location of modifications. These changes include variations in band frequencies, width, and intensities. For example, aryldiazonium salts [139] were used to modify individual sodium dodecyl sulphate (SDS) coated SWNTs with aryl group. The Raman spectrum of functionalized (SDS-free) SWNTs shows a disorder mode much higher than pristine SWNT the radial breathing modes are nearly unobservable. 

Raman spectroscopy is one of the most powerful techniques for the characterization of nanocarbons. It is also a convenient technique because it involves almost no sample preparation and leaves the material unharmed. There are four characteristic bands for CNTs The band at 200 cm-1 is called radial breathing mode (RBM). It depends on the curvature and can be used to calculate the diameter of SWCNTs [61]. The relatively broad D-band at 1340 cm-1 is assigned to sp2-related defects and disorder in the graphitic structure of the material. The tangential C-C stretching mode is located at -1560 cm 1 (G-band). The second order mode of the D-band can be observed (G -band,... 

The theoretical prediction of these vibrations was made by several authors (see for example refs. 8,9). Two main characteristics in the Raman spectra of SWNTs can be raised. First, the radial breathing mode, hereafter referred to RBM, is strongly dependant upon the diameter of the tubes. 

Figure 2. Calculations of the radial breathing mode frequency of (10,10) armchair single-walled nanotubes a) isolated tubes b) bundle of 7 tubes and c) bundle with an infinity of tubes.

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 Ih symmetry of the 60-atoms molecule allows 2Ag and SH modes to be Raman active and 4T modes to be IR active. The four IR active modes are at 1430, 1185, 580 and 528 cm , respectively. The most important Raman modes are at 1469 (tangential bond alternation or pinch mode, Ag), 495 (radial breathing mode, T ) and 271 (squashing mode, Hg) cm , respectively. In the low temperatur phase degenerate modes split from a crystal field and Davidov interaction. Good reviews on the group theoretical analysis and on the line positions are given in (Dresselhaus et al., 1992 Matus and Kuzmany, 1993). 

Fig. 5.7 Raman spectrum of SWNTs excited by 785-nm CW radiation. The observed peaks around 1,590, 1,300, and 260 cm correspond to the tangential graphite-like modes (G-band), the disorder-induced modes (D-band), and the radial breathing modes (RBM), respectively [27]...

Raman spectra of SWCNTs as well as the most common experimental techniques of their characterization have been also thoroughly discussed in literature [3, 26]. The strongest Raman bands of SWCNTs are the RBM band (radial breathing mode in the range 100-300 cm ), and the G-band (tangential mode at around 1600 cm ) as shown in Fig. 7.2 [27]. Two more characteristic, but weaker bands are the D-band (disorder-induced band in the range 1300-1400 cm ) and the G -band (sometimes called D -band) at around 2600-2800 cm . ... 

Fig. 7.2 Most important Raman lines of single-wall carbon nanotubes as excited with three different laser lines. RBM radial breathing mode, D defect-induced line, G graphitic line, D2 overtone of D-line, G2 overtone of G-line. The thin straight lines indicate the dispersion of the modes. All spectra in one slot were normalized to unit height (Reprinted with permission from Kuzmany H, Plank W, Schaman CH, Pfeifer R, Hasi F, Simon F, Rotas G, Pagona G, Tagmatarchis N (2007) Raman scattering from nanomaterials encapsulated into single-wall carbon nanotubes. Journal of Raman Spectroscopy 38 (6) 704—713, John Wiley Sons, Ltd.)...

Kuzmany H, Plank W, Hulman M, Kramberger Ch, Griineis A, Pichler Th, Peterlik H, Kataura H, Achiba Y (2001) Determination of SWCNT diameters from the Raman response of the radial breathing mode. Eur Phys J B 22(3) 307-320... 

SWCNTs, DWCNTs, or MWCNTs with very small inner-tube diameters show another size-dependent Raman feature in the low-frequency range referred to as radial breathing modes (RBMs) [35, 39, 40]. The RBMs are considered as a clear indicator for the presence of CNTs, since this Raman feature is unique to CNTs and is not observed for other carbon materials. As suggested by the name, the RBM is a bond-stretching, out-of-plane mode, where all carbon atoms vibrate simultaneously in the radial direction. The RBM frequencies are between 100 and 400 cm and were found to be inversely proportional to the tube diameter [41 3]. In case of DWCNTs and small-diameter MWCNTs, RBM frequencies higher than 200 cm are ascribed to inner tubes while lower frequencies can be associated with both, inner and outer tubes [44, 45]. SWCNTs typically exhibit... 

Zhao XL, Ando Y, Qin LC, Kataura H et al (2002) Radial breathing modes of multiwalled carbon nanotubes. Chem Phys Lett 361(1-2) 169-174... 

Chiashi S, Murakami Y, Miyauchi Y, Maruyama S (2008) Temperature dependence of Raman scattering from single-walled carbon nanotubes undefined radial breathing mode peaks at high temperatures. Jpn J Appl Phys 47 2010... 

Fig. 3.3. Power spectra in the vibrational transients of single gold nanoparticles, shown together with their scanning electron micrographs, (a) Nanospheres (80 nm diameter) show only the radial breathing mode at 40GHz. (b) Elongated particles show an ellipsoidal deformation mode at 14GHz. (c, d) Dumbbells usually present the ellipsoidal mode and a stretching mode at 6 GHz...

The presence of the third peak in the low frequency Raman spectrum, radial breathing mode, testifies to the presence of SWNTs in the arrays. Moreover, it contains the quantitative characteristic information on SWNTs structure. The SWNTs diameter d was calculated as v= 6.5+223.75/al, where v(cm ) is the frequency of the radial oscillation modes of the SWNT hexagonal lattice. SWNTs were observed in both types of arrays synthesized with 1.0% and 10% of ferrocene in the feeding solution. CNT arrays obtained with 1.0% of ferrocene have V =183.1cm (Fig. 3a), and the calculated d value is 1.2 nm, which... 

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