Air oxidation could result in the motion of metal confined in carbon nanotubes. This could also be utilized to tailor various hybrid nanostructures. By controllable air-oxidation, as-prepared metal carbon nanotube nanorods could be converted firstly to core-shell-void nanorods, then to metal/metal oxide carbon nanotubes, and finally to mesoporous metal oxide nanotubes. The metal/metal oxide carbonnanotubes nanotubes and mesoporous metal oxide nanotubes were expected to find many applications, such as in lithium ion batteries, catalysis, magnetic drug delivery, and gas sensing.

Diffusion of Metal in a Confined Nanospace of Carbon Nanotubes Induced by Air Oxidation. Zhou, J., Song, H., Chen, X., Huo, J: Journal of the American Chemical Society, 2010, 132[33], 11402-5