Smallest freestanding single-walled carbon nanotube

Here, we report the successful direct observation of the smallest free-standing single-walled carbon nanotube, which has a diameter of about 0.43 nm. Our single-walled carbon nanotubes were produced by the improved floating reactant method, which combines the conventional substrate and floating catalyst methods using zeolite particles as a floating catalyst support. This finding is also important because small-diameter nanotubes were proved to be able to grow without any confinement that limits the tube diameter such as in the tube growth in a template or in the central core of a multiwalled nanotube, as reported in previous studies by other groups. The success of obtaining very small single-walled carbon nanotubes opens the door to unprecedented applications of this fascinating material as a true 1D material.