Effect of the Synthesis Method on the Distribution of C, B, and N Elements in Multiwall Nanotubes: A Spatially Resolved Electron Energy Loss Spectroscopy Study

Multiwalled boron- and nitrogen-doped carbon nanotubes (CxByNz) have been synthesized using both low and high temperature synthesis methods namely an aerosol-assisted chemical vapor deposition process and a laser vaporization process, respectively. Degrees of purity, homogeneity, and yield have been estimated from a systematic inspection of the sample by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Spatially resolved electron energy loss spectroscopy (EELS) measurements in a dedicated scanning transmission electron microscope (STEM) have been performed in order to correlate spectroscopic information with structural features at a nanometer scale on nanotubes and nanoparticles that originates their growth. As a result, spatially resolved analyses have shown a clearly defined segregation of BN-regions from CN-rich regions, indicating that separate nanodomains of boron nitride and carbon nitride may exist with different arrangements in carbon nanotubes as a function of the synthesis method.