Abstract Submitted to the ; NANOTUBE'05 Conference:

Near-infrared spectroscopy is a convenient tool for measuring nanotube / non-tubular carbon impurities ratios in carbon nanotube samples¹. These measurements are based on separation of contributions from nanotubes and impurities to the near-infrared absorption. In the current work we produced a reference standard for NIR measurements using purified laser nanotubes. The sample was oxidized slowly in a thermal gravimetry analyzer (TGA) in 2 % oxygen atmosphere. In these conditions, the sample oxidized in several steps, which were attributed to carbonaceous impurities, nanotubes and graphitic shells based on TEM and Raman observations. Stopping oxidation at 625 ^oC (this temperature is sample-specific) allowed us to produce a sample with well-defined ratio of nanotubes, graphite and metal catalyst. Since carbonaceous impurities no longer glue nanotubes and particles together, further dispersion and centrifuging allowed us to remove particles (verified by IC P-MS) and produce pure nanotube sample. This sample was used as a reference standard to determine relative contributions of nanotubes and impurities to NIR absorption in p-plasmon background and Van-Hove peak areas. We will also discuss a refinement of this technique for samples with varying diameter distributions, that takes into account energy dependence of absorption.

1. M. E. Itkis, et al. Nano Lett, 3, 309 (2003)

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