SEPARATION OF CARBON NANOTUBES

摘要

A method of sorting single-walled carbon nanotubes according to their physical structure by use of an inhomogeneous magnetic field. A mixture of single-walled carbon nanotubes in an aqueous surfactant suspension is positioned in a gradient magnetic field. Those nanotubes having metallic properties, and thus being paramagnetic, are attracted to regions of higher field while those having semiconducting properties, and thus being diamagnetic, are repelled to regions of lower field. Within the semiconducting nanotubes, a separation is also achieved according to their diameter upon which depends their diamagnetic susceptibility. The distribution can be adjusted by selecting the density of liquid used to suspend the nanotubes, for example by using heavy water so that the nanotubes move to a position where the net forces of gravity, buoyancy and the magnetic field, are in balance. A method of separating impurities, such as metallic catalyst particles, is also described in which a magnetic field is applied to a suspension of carbon nanotubes and the metallic particles are attracted towards the poles of the magnet allowing them to be removed.