Mechanical purification of single-walled carbon nanotube bundles from catalytic particles

Ferromagnetic particles used for the catalytic growth of single-walled carbon nanotubes (SWNTs), which are embedded in a graphitic shell, represent a major obstacle in studying the bulk material. We have explored a purification method that is based on a mixing of the SWNT suspension with inorganic nanoparticles in an ultrasonic bath, which causes ferromagnetic particles to be mechanically removed from their graphitic shells. By trapping these magnetic particles with permanent magnetic poles and with a subsequent chemical treatment, a high Purity SWNT material was obtained.