Exfoliation of single-wall carbon nanotubes in aqueous surfactant suspensions: A Raman study

Aqueous suspensions of bundles and individual single-wall carbon nanotubes were prepared with the help of surfactants. We study the changes in the Raman spectra of the suspensions with respect to powders, and of exfoliated tubes with respect to bundles. The radial breathing modes (RBM) upshift in suspensions because of the internal pressure of the liquid. By contrast, no shift is observed in the RBM spectra after exfoliation in the suspensions. However, we demonstrate a selectivity of the exfoliation process for tubes of small diameters.