Purification and microwave treatment of single-walled carbon nanotubes

Abstract

Raw single-walled carbon nanotubes produced by HiPCO process were purified successfully through repetitive acid treatment to remove amorphous carbon and transition metal catalysts. After purification, SWNTs was cut with acid treatment to disperse in organic solution. Residual metal impurities from purified SWNTs dispersed in ethanol solution and aqueous surfactant solution were removed by magnetic field. Microwave radiation is a well-known noninvasive and clean processing tool that has been widely used to activate chemical reactions. Raw SWNTs were purified in air by microwave irradiation for 30 min using kitchen microwave oven. As a result, metal impurities were oxidized. Mild washing with acid solution removed oxidized metal impurities on the surface of raw SWNTs. Preferential destruction of metallic SWNTs with small diameters was achieved by microwave irradiation for 60 min due to stress induced by high curvature and abundant electron density. Microwave irradiation over critical time caused SWNTs to be damaged severely and destroyed to be graphite.