Methods of enriching different species of carbon nanotubes

A method of enriching specific species of carbon nanotubes by exposing a composition of carbon nanotubes comprising semiconductor carbon nanotubes and metallic carbon nanotubes to an azo compound, the azo compound having the chemical formula (I) or a salt thereof

• AN=N−Bn (I)
• wherein
• at each occurrence, A is an optionally substituted naphthalene;
• B is the same as A or different from A and is an optionally substituted naphthalene;
• and
• n is 2 or 3;
• the method comprising
• a) mixing the azo compound with a suspension comprising the composition of carbon nanotubes to form a mixture;
• b) incubating the mixture to react the azo compound with the carbon nanotubes, whereby a supernatant enriched with semiconductor carbon nanotubes and a precipitate enriched with metallic carbon nanotubes are formed in the mixture;
• and
• c) separating the supernatant and the precipitate formed in the mixture.