Separation of single-walled carbon nanotubes by gel-based chromatography using surfactant step-gradient techniques and development of new instrumentation for studying SWCNT reaction processes

Single-walled carbon nanotube (SWCNT) synthesis methods such as CoMoCATTM, HiPcoTM, pulsed laser vaporization (PLV), and catalytic chemical vapor deposition (CCVD) produce several different distributions of (n,m) SWCNT structures, where (n,m) defines the nanotube diameter and chiral wrapping angle. Post-synthesis processing such as functionalization and/or separations must therefore be employed to yield high purity electronic or single (n,m) samples. Through the use of a surfactant gradient across a gel-based chromatographic column, separations of single (n,m) species can be achieved. Anionic surfactants such as SDS, SDBS, and AOT display different separation effectiveness for single (n,m) species. Results of near-infrared optical absorption for separated SWCNT surfactant suspensions will be discussed, leading to a broader understanding of the important factors necessary for the gel chromatography separation technique. In particular, the effects of SWCNT/surfactant micelle structure are found to be key to achieving fast, simple SWCNT electronic type separations. Additionally, development of new instrumentation for the near-infrared spectrofluorimetric analysis (NIR-SFA) of SWCNTs is useful to the advancement of fundamental SWCNT research and applications. NIR-SFA, for instance, allows for the (n,m) structures of a sample to be identified and monitored during the progress of a chemical reaction or separation experiment. Seeking to achieve the time resolutions necessary for such experiments, the design and optimizations of a system utilizing single-wavelength excitation by diode lasers coupled with a fast NIR detection system are presented