Enrichment of small-diameter double-wall carbon nanotubes synthesized by catalyst-supported chemical vapor deposition using zeolite supports

A highly efficient enrichment of thin double-wall carbon nanotubes (DWNTs) having ail average outer diameter of ca. 1.4 nm by thermal oxidative purification has been reported. Thin DWNTs of ca. 1% with respect to single-wall carbon nanotubes (SWNTs), which are synthesized by catalyst-supported chemical vapor deposition (CCVD) on zeolite supports, are enriched up to ca. 90% (vs SWNTs) by thermal oxidation in air. The present thin DWNTs grown on zeolite are several hundreds of times as resistant as SWNTs toward the oxidation at 700 degrees C. When oxidative purification is applied for DWNTs with larger diameters, the amount of DWNTs lost during the purification process is large compared to thinner DWNTs lost. The present oxidative purification is much more effective for thin DWNTs with diameters smaller than 2 nm.