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摘要
Resonance enhanced Raman spectroscopy is a simple, quick, non-destructive and powerful tool for the characterization of single-walled carbon nanotubes (SWNTs). Raman spectroscopy can be used to obtain information about both the geometry structure and the electronic density of states of SWNTs, including isolated individual SWNTs. In this review, the characteristics of the main Raman active modes of SWNTs, including radial breath mode (RBM), G-band, D-band and G'-band were stated, and the application of Raman spectroscopy in the characterization of the diameter and chirality of SWNTs, strained SWNTs, defects and doping in SWNTs, and the temperature-dependence of the structures of SWNTs were summarized. The diameter of SWNTs can be calculated from the frequency of RBM (omega(RBM)), according to an equation which is slightly varied with the type of SWNT samples. Furthermore, by combining the Raman resonance condition, omega(RBM) and Kataura plot, both information of electronic conducting properties, electron transition energy, and (n, m) of SWNTs could be obtained. With application of uniaxial strain, the D-band, G-band and G'-band of SWNTs shift due to the change of C-C distance, according to which the strain applied on SWNTs can be measured. At the same time, the Raman resonance intensity varies, which is attributed to the influence of uniaxial strain on the electronic structure of SWNTs. Raman spectroscopy can also be used to characterize radial deformation of SWNTs. It is found that the variation of frequency and intensity of RBM with the application of radial deformation shows dependence on the diameter and chirality of SWNTs. Theoretically, G-band will change under bending deformation, while experimental verification is still in needs due to difficulties of bend deformation of SWNTs in experiments. Besides, Raman spectra of SWNTs can be used to monitor the temperature of SWNTs due to the sensentivity of Raman spectra to photon properties. The Raman spectra of SWNTs upshift with the increase of temperature and the Raman resonance intensity varies with the change of temperature. Interestingly, the temperature coefficiency of omega(RBM) was found to be diameter- and chirality-dependent, while that of omega(G) did not show such effects. The intensity of Raman D-band of SWNTs varies with the concentration of defects in SWNTs, according to which the defects in SWNTs can be conveniently characterized. Besides, for doped SWNTs, shift of frequency and variations of intensity of both G-band and G'-band were observed, indicating the change of atomic structure and electron density of state of SWNTs. Due to the high resolution of micro-Raman spectroscopy, it is also a convenient tool to study of inter-molecular junctions in individual SWNTs. In the end of this review, the challenges and opportunities for the further application of Raman spectroscopy in the characterization of SWNTs were discussed.
