Quantitative analysis of the (n,m) abundance of single-walled carbon nanotubes dispersed in ionic liquids by optical absorption spectra

Room temperature ionic liquids (ILs) of imidazolium ions were found to be ideal media for dispersing single-walled carbon nanotubes (SWNTs) at relatively high content and for studying their intrinsic properties. Comparing to other dispersion methods IL dispersion do not involve in extensive ultrasonication and centrifugation, thus can reflect the real chiral composition and abundance distribution of the original raw SWNT samples. Optical absorption spectra of 1-N-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6])-dispersed SWNTs at different concentrations are performed based on direct and precise weighing the mass of the SWNT samples. An excellent linear relationship of the absorbance with respect to SWNT concentration is observed not only in a large concentration scale but also over a wide wavelength range. By deconvolution of the absorption spectra in the region of the first subbands transition of semiconducting SWNTs (E11S region, 800–1400 nm) into individual bands with (n,m) assignment in good agreement with fluorescence spectra, the relative abundance of 12 different semiconducting chiralities is analyzed quantitatively. It is found that the relative abundance of semiconducting SWNTs follows an exponential trend with respect to chiral angle. No clear dependence of the relative abundance on tube diameter is observed.