Efficient separation of nitrogen-doped carbon nanotube cups

Nitrogen-doped carbon nanotubes synthesized from a mixture of ferrocene, xylenes, and acetonitrile using chemical vapor deposition technique comprise compartmented hollow structures resembling stacked cups. Separating stacked nitrogen-doped carbon nanotube cups (NCNCs) into individual cups is an attractive way to further manipulate their morphology, providing additional opportunities for applications of NCNCs. Here we demonstrate an effective, simple, and low-cost separation method to obtain individual NCNCs around 180 nm in length, by sonicating as-synthesized stacked NCNCs in concentrated KCl solution. Another advantage of this technique is that it is highly selective to the separation of adjacent NCNCs and capable of preserving the surface structure and functionalities of stacked NCNCs. Here we demonstrate that the presence of potassium ions is vital for the separation and we hypothesize that the separation mechanism involves a partial intercalation that facilitates the separation of NCNCs.