Imaging Nitrogen in Individual Carbon Nanotubes

Semiquantitative chemical imaging of the spatial distribution of nitrogen in a carbon matrix, adsorbed/intercalated N 2, and highly concentrated N 2 in nitrogen-doped carbon nanotubes (N-CNTs) with a spatial resolution of 30 nm has been obtained by scanning transmission X-ray microscopy (STXM). The local electronic structures of individual N-CNTs at C and N K-edges have been extracted from STXM image stacks (sensitive to bulk) and compared with that of N-CNT using X-ray absorption near-edge structure spectroscopy in total electron yield mode (sensitive to surface). The polarization-dependent STXM measurement has revealed the preferred orientation of N 2, parallel to the N-CNT long axis.