A method of obtaining purified semiconducting SWCNTs from a bulk mixture of metallic SWCNTs and semiconducting SWCNTs by first creating an aqueous solution containing the bulk mixture and adding a functionalized particle or nanoparticle to the solution, whereby the functionalized particle or nanoparticle reacts chemically with the metallic SWCNTs to form a high density particle-nanotube composite that can be physically separated by centrifugation.