(n,m) abundance evaluation of single-walled carbon nanotubes by fluorescence and absorption spectroscopy

A methodology that takes into account the (n,m) structure of single-walled carbon nanotubes (SWNTs), through an exciton-exciton resonance model and an electron-phonon interaction model, was employed in order to evaluate the semiconducting (n,m) abundance of two SWNT samples (i.e., Co-MCM- 41 and HiPco). This was based on photoluminescence and near-infrared absorption data obtained on aqueous suspensions of individually dispersed SWNTs. In the absence of known (n,m) abundance SWNT samples, we resorted to determining the diameter distribution curves for both samples, which were found to obey an unsymmetrical log-normal distribution, typical for vapor-phase particle growth. Using this log-normal function, we reconstructed the near-infrared E-11(S) absorption spectrum of the narrow diameter distribution Co-MCM-41 SWNT sample, which in turn enabled us to assess the predictions of these two theoretical models. High spectral reconstruction accuracy was obtained from the electron-phonon interaction model when considering (11,0) and (10,0) zigzag nanotubes, along with (n,m) line widths inversely proportional to their extinction coefficients.