Directly Measured Optical Absorption Cross Sections for Structure-Selected Single-Walled Carbon Nanotubes

We have measured peak and spectrally integrated absolute absorption cross sections for the first (E-11) and second (E-22) optical transitions of seven semiconducting single-walled carbon nanotube (SWCNT) species in bulk suspensions. Species-specific concentrations were determined using short-wave IR fluorescence microscopy to directly count SWCNTs in a known sample volume. Measured cross sections per atom are inversely related to nanotube diameter. E-11 cross sections are larger for mod 1 species than for mod 2; the opposite is found for E-22.