Cutting, solubilizing and size-sorting of single-wall carbon nanotubes

The fluorination of purified HiPco single-wall carbon nanotubes (SWNTs) to a stoichiometry CFx (x less than or equal to 0.2) followed by pyrolysis of the partially fluorinated SWNTs up to 1000 degreesC was found to have "cut" the nanotubes to a range of short lengths (average < 50 nm). The pyrolysis process was monitored in-situ with TGA-FTIR. The "cut" nanotubes have been characterized by Raman, ATR-IR, EDAX and AFM measurements. Short bundles composed of strongly interacting individual nanotubes were found in the "cut" nanotube sample. Solubilization of the "cut" nanotubes was achieved by derivatizing them either through re-fluorination or by refluxing in dilute nitric acid. Such derivatized "cut" SWNTs form a stable suspension in alcohol solvents such as ethanol or isopropanol, through which the size exclusion chromatography (SEC) separation of these short SWNTs bundles was conducted. AFM analysis was used to characterize the fractions from the SEC and the statistical length distribution was obtained. The short lengths and specific reactivities of the cut-SUWTs should lead to novel applications in fields such as microelectronics, drug delivery media and composite materials.