The present disclosure generally describes techniques for separating semiconducting carbon nanotubes from metallic carbon nanotubes in a carbon nanotube dispersion. The semiconducting carbon nanotubes and metallic carbon nanotubes may be provided and dispersed in a fluid. Once the semiconducting carbon nanotubes attach to the amine-coated magnetic particles, a magnetic field may be applied to the amine coated magnetic particles and attached semiconducting carbon nanotubes to attract and hold at least a portion of the semiconducting carbon nanotubes, so that the semiconducting carbon nanotubes may be separated from the fluid and/or metallic carbon nanotubes.