Origin of radial breathing mode in multiwall carbon nanotubes synthesized by catalytic chemical vapor deposition

The origin of radial breathing mode (RBM) in the Raman spectra of multiwall carbon nanotubes (MWNCTs) is discussed. In general, RBM is characteristics of single wall carbon nanotube (SWCNT). With the help of transmission electron microscope (TEM) and Raman spectroscopic studies, it is established that the presence of SWCNT in the cavity of MWCNT is responsible for the appearance of RBM in MWCNT (synthesized by low temperature catalytic chemical vapor deposition technique). The estimated diameter of 8.2 Å (from Raman study) of SWCNT is almost same as that observed (∼8.3 Å) in TEM studies.