Raman scattering analysis of changes induced by chemical treatment of double-walled carbon nanotubes

Here we examine the changes in double-walled carbon nanotubes with two chemical treatments using Raman scattering spectroscopy at an excitation of 632.8 nm (1.96 eV). The nanotubes were acid treated then subsequently treated with phosphorus pentasulfide (a mild electrophillic catalyst). While the treatment process maintains the integrity the nanotubes, Raman analysis indicates the outer shells loose their electron–phonon resonance and metallic character, leaving only the tangential mode from the secondary (inner) tubes. After chemical treatment the strongly up-shifted G-band, at 1585 cm−1, has been designated as secondary semiconductor tubes, exhibiting resonant scattering via E 22 s