Smallest limit of tube diameters for encasing of particular fullerenes determined by radial breathing mode Raman scattering

Lineshapes of radial breathing mode (RBM) Raman scattering from single-wall carbon nanotubes (SWNTs) encasing the fullerenes vary depending on the sizes of fullerenes. The lineshape fit using Lorentzian lines to the spectrum indicates downshift of ωr (RBM frequency) for most lines as compared with those observed in empty-SWNTs, except for one upshifted line associating with the stress to the tube-wall from the inside fullerenes. The smallest limit of tube diameters (d) is determined from this upshifted line, and they are resulting to be ∼1.37 nm for C60, ∼1.45 nm for both C76 and C78, and ∼1.54 nm for C84 when using ωr (cm−1)=246/d (nm).