Controlled opening of single-wall carbon nanohorns by heat treatment in carbon dioxide

The opening of bud-type single-wall carbon nanohorns (SWNHs) by heat treatment in CO₂ was studied by TEM and nitrogen adsorption (77 K). The adsorption isotherms indicate that oxidation by CO₂ at 1273 K provides a sufficient nanohorn opening. The pore structure parameters of the open nanohorns can be controlled by varying the treatment conditions; the size of the generated nanopores increases with the temperature and time of treatment. In addition, TPD experiments indicate a significant decrease of the oxygen content in SWNHs opened by heat treatment in CO₂. This is in contrast to the procedures reported in the literature for opening of carbon nanotubular structures, typically introducing oxygen functional groups.