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September 2008 EEEL Researchers Uncover Missing Light |
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EEEL Researchers John Lehman, Katherine Hurst, and Lara Roberson, along with collaborators Kathryn Nield and John Hamlin of New Zealand’s Measurement Standards Laboratory, have identified unique features in the reflectance spectra of single-wall carbon nanotubes (SWCNT) that were previously misidentified in the literature as absorbance. In the process, they have demonstrated a novel method for determining SNCWT absorbance that, unlike other published accounts, is independent of sample concentration and does not rely on data post-processing to remove the effects of contaminants. Prior to this work, other published results for SWCNT absorbance relied on transmittance measurements of SWCNTs in solution using spectrophotometers. The spectrophotometer method assumes that the reflectance of the sample is negligible and that the absorbance is complementary to the transmittance (A = 1 – T). The NIST results, which appeared in the August 7, 2008, issue of the Journal of Physical Chemistry C, demonstrate that reflectance is not negligible and in fact dominates absorbance near excitonic transitions. |