Synthesis and structure of pristine and alkali-metal-intercalated single-walled carbon nanotubes

Single-walled carbon nanotubes (SWNTs) were synthesized by ablating graphite targets with either the primary (1064 nm) or the second-harmonic (532 nm) beam of a pulsed Nd:YAG laser at high temperature. The structure and the morphology of the raw materials were studied by high-resolution transmission microscopy (HRTEM), X-ray diffraction, and micro-Raman techniques. The diameter distribution of the SWNTs was found to vary with the laser frequency used for ablation. The raw materials were reacted with alkali metal (K, Cs) by vapor transport method. The saturation composition was found to be MC(8)s (M = K or Cs). No crystalline structure was observed in the reacted materials by X-ray diffraction. In situ metal deposition, TEM, and electron energy loss spectroscopy (EELS) measurements were performed on individual SWNT bundles at 300 K. The results showed that alkali metals can be reversibly intercalated into the SWNT bundles. Although intercalation induced structural disorder, individual nanotubes and to a large extent the bundles maintained their structural integrity after intercalation and de-intercalation.