Standing or lying C ₇₀s encapsulated in carbon nanotubes with different diameters

Single-walled carbon nanotubes (SWNTs) encapsulating C ₇₀s, so-called C ₇₀ peapods, were synthesized in high yield by a vapor-phase doping method. Raman spectra, high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) measurement indicate that the tube diameter is one of the important factors to determine the orientation of C ₇₀ molecules inside the SWNTs. SWNTs with different diameters give different alignment of C ₇₀ molecules. The lying orientation is favorable over the standing orientation in thin nanotube, i.e. 1.36 nm nanotubes, whereas the standing orientation is favorable in thick nanotubes, i.e. 1.49 and 1.61 nm nanotubes.