The influence of surfactants on the distribution of the radial breathing modes of single walled carbon nanotubes

Single walled carbon nanotubes (SWNT) were solubilized in similar to 30 mM sodium dodecylsulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) aqueous solutions by severe sonication. Raman scattering experiments using three different excitation energies revealed that the distribution of the radial breathing modes (RBM) for SDBS-SWNT samples is shifted to lower frequencies compared to the SDS-SWNT samples. This effect is proposed here to be due to preferential solubilization of large diameter SWNTs by SDBS compared to SDS solutions, which may be accounted for by the increased effective dielectric constant and consequently increased transition energy as the tube solubilizes in an aqueous environment.