Chirality-dependent curvature effect in smallest single-walled carbon nanotubes

Abstract

Polarized Raman spectra are measured for 0.4 nm single-walled carbon nanotubes embedded in the zeolite matrix. The polarization dependence of the Raman intensity of the radial breathing mode showed that the carbon nanotubes inside the channels of the zeolite are perfectly aligned. The observed radial breathing mode frequencies deviated from those predicted by the elastic model. The strong curvature effect leads to two features: (i) the radial breathing mode frequencies show obvious softening and (ii) the degree of the softening depends on the tube chirality, which agrees well with the theoretic calculations.