Multiple splitting of G-band modes from individual multiwalled carbon nanotubes

Surface-enhanced Raman scattering spectra of an individual multiwalled carbon nanotube (MWNT) with the innermost diameter $\text{∼1\hspace{0.17em}}\mathrm{nm},$ prepared by hydrogen arc discharge, show a single peak of radial breathing mode and multiple splitting of the tangential stretching G-band modes. Based on Lorentzian line shape analysis and related theoretical calculations, the G-band modes of MWNT are confirmed to be composed of both G-band modes (linewidth $\text{4\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}})$ from the innermost tube and graphite-like mode (linewidth $\text{∼20\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}})$ from the outer cylinders in MWNT. This observation indicates that MWNTs are unique and possess characteristic Raman spectra different from other ${\mathrm{sp}}^2$ carbon allotropes.