Figure 3.

N 1s core level photoemission spectra recorded at 100 K of metallic (a) and semiconducting (b) SWCNTs after exposure to NO₂ at the saturation limit of 260 L, compared to the N 1s spectrum reported in ref (19) (c), where the highest binding energy component corresponds to N₂O₄ and NO₃. This component has a minor contribution in the right and middle spectra corresponding to the separated samples. Also note that the intensity of the response for the metallic sample is twice as high as that corresponding to the semiconducting one.