Direct growth of aligned open carbon nanotubes by chemical vapor deposition

Open carbon nanotubes were directly obtained at a very high yield by pyrolysis of acetylene over iron/silica substrates. Scanning electron microscope images show that the nanotubes grow outwards perpendicularly and separately from the surface of the substrate and form an aligned nanotube array. The bottom ends of the tubes can be easily stripped off from the substrate and are found to be opened while the top ends are closed, as verified by transmission electron microscope. The tip growth of tubes might be responsible for the formation of open carbon nanotubes.