Raman scattering study of double-wall carbon nanotubes derived from the chains of fullerenes in single-wall carbon nanotubes

Double-wall carbon nanotubes (DWNTs) were prepared in quantitative amount from the chains of C60 molecules generated inside single-wall carbon nanotubes (SWNTs). The C60 molecules inside the SWNT unchange up to ∼800°C without dedoping. Further heating at ∼1200°C induces the coalescence between C60 and eventually the C60 molecules transform into a tubular structure. The DWNTs thus prepared show radial breathing mode (RBM) Raman scattering associated with inner tubes as well as those from parent outer tubes, which are all explained by a model of diameter pairing in DWNT with an inner tube diameter smaller by 0.71±0.05 nm than an outer one.