Choking Effect of Single-Wall Carbon Nanotubes on Solvent Adsorption in Radial Breathing Mode

The radial breathing mode (RBM) frequency in Raman spectra of single-wall carbon nanotubes (SWNTs) is upshifted (3−9 cm-1) by immersion of the SWNTs in various alcohols and water. However, the immersion in the solvents does not cause any visible variation in the tangential mode frequency. The degree of this RBM frequency upshift induced by the solvent adsorption corresponds to that caused by applying a high pressure of 1 GPa (6−10 cm-1/GPa) in the literature. The degree of the RBM frequency upshift increases with increases in the molecular weight of the solvents. RBM frequency upshift caused by immersion of SWNTs in water is much larger than that by the molecular weight of alcohols, indicating the cluster formation of water molecules.