Raman and Infrared Spectroscopy of Carbon Nanotubes

From their first measurement and theoretical discussion on, the Raman spectra of carbon nanotubes provided valuable information on the shape and composition of the structure. They can also serve to prove the existence or nonexistence of nanotubes in a sample, which is assessed, among others, by considering a distinct Raman band. It is called radial breathing mode (RBM) band and corresponds to a synchronous radial vibration of all carbon atoms in perpendicular to the tube s axis. This band is the characteristic of the nanotube stracture, and for the time being, nothing Hke this has ever been observed for any other carbon material studied. 

While the electronic wavefunction has been considered to describe electronic properties, the discussion wiU now focus on the phonons, that is, the quantized normal modes of the lattice. Again the zone-folding model of a graphene layer being roUed up to become a nanotube proved to be a useful approach. In comparison to graphene, the resulting density of phonon states exhibits many sharp peaks similar to the van Hove singularities in the density of electronic states (Section 

The D-band is observed at ca. 1347 cm . It results from disorder defects in the nanotube lattice and originates from phonons close to the point K of the Brillouin zone. The signal is strongly dependent on the irradiated laser energy. Changing, 

Experimental studies on nanotubes revealed that the energy of the exciting radiation has a general influence on the Raman spectrum. This is indicative of resonant processes with the resonance resulting from the accordance of the excitation energy the transition energy Ea between the van Hove singularities 

In comparison to SWNTs, MWNTs give rise to a much more graphite-like Raman spectrum with a dominant signal at ca. 1575 cm and a weaker one at about 868cm . The determination of stmctural properties from the Raman spectra of MWNTs is anything from complicated to impossible due to the variety of constituent tubes and their respective interactions. 

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J. Kastner, T. Pichler, H. Kuzmany, S. Curran, W. Blau, D.N. Weldon, M. Delamesiere, S. Draper, and H. Zandbergen, Resonance Raman and infrared spectroscopy of carbon nanotubes. Chem. Phys. Lett. 221, 53-58 (1994). 

Kastner J, Pichler T, Kuzmany H, Curan S, Blau W, Weldon DN, Delamisiere M, Draper S, Zandbergen H (1994) Resonance Raman and infrared spectroscopy of carbon nanotubes. Chem Phys Lett 221(l-2) 53-58... 

Measurement of adsorption phenomena by chemical means require adsorbents that have a relatively high surface area, preferably in excess of 20-50 m /g, to provide sufficient sensitivity. Such carbons are, e.g., activated carbons, carbon blacks, graphite wear dust, and carbon nanotubes. Physical measurements, such as by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), Fourier transform infrared (FTIR), and special Raman spectroscopies, can be done with materials of much lower surface area. 

Functionalized multi-walled carbon nanotubes (MWNTs) were prepared by acid treatment followed by reaction with 3-aminopropyltriethoxysilane. Reaction of silane with oxidized nanotubes was confirmed by Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray (EDX) analysis to confirm silicon on the surface of the MWNTs. Raman spectroscopy of the acid-treated MWNTs confirmed formation of surface defects due to carboxyl... 

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