Molar Extinction Coefficient of Single-Wall Carbon Nanotubes

The molar extinction coefficient of single-wall carbon nanotubes (SWNTs) is determined using fluorescence tagging, as well as atomic force microscopy (AFM) imaging, which facilitate the correlation of nanotube concentrations with absorption spectra. Tagging of SWNTs is achieved using fluorescence-labeled single-strand DNA oligomers as the dispersion additive, while AFM imaging is used to determine the mass of SWNTs in the retentate of vacuum-filtered colloidal SWNT suspensions. The resulting absorption cross section for the first exciton transition of (6,5) nanotubes of 1.7 x 10(-17) cm(2) per C-atom corresponds to an extinction coefficient of (4400 +/- 1000) M-1.cm(-1), which is equivalent to an oscillator strength of 0.010 per carbon atom.