Freon-CO2-assisted purification of single-walled carbon nanotubes

With the rapidly growing applications, efficient purification of single-walled carbon nanotubes (SWCNTs) has become one of the key problems. This paper proposes Freon-CO2-assisted purification of SWCNTs, where CO2 can oxidize the graphitized carbon layer to expose iron (Fe) impurities, while the chlorine from Freon can react with the Fe impurities to form low-boiling-point metal chlorides that can be eliminated in a gas stream. After an acid washing with a very small amount of hydrochloric acid, the last remaining metal impurities are removed and highly pure SWCNTs are produced. Compared with traditional strong-acid-oxidation purification or high-temperature-vacuum purification, this method can maintain the structure and length of the SWCNTs. Raman spectra show that an IG/ID ratio of more than 100 can be obtained. This purification method can maintain the microstructure and excellent properties of SWCNTs and provide a solution for the preparation of high-quality SWCNTs to exert their properties.