Nondestructive and high-recovery-yield purification of single-walled carbon nanotubes by chemical functionalization

Raw single-walled carbon nanotubes produced by arc discharge were first treated with K2S2O8 in dilute H2SO4 solution to generate oxygenated functional groups such as carboxyl, hydroxyl, and carbonyl on varying carbon components. Further functionalization with octadecylamine was carried out via a condensation reaction between an amine group and a carboxyl group with the assistance of dicyclohexylcarbodiimide. The attachment of long alkyl chains leads the sample to be soluble in tetrahydrofuran and other organic solvents. The thus obtained stable dispersion was subjected to dispersion-centrifugation recycles, and then the metal catalysts and varying carbon impurities were separated with carbon nanotubes. The advantage of this procedure ties in high-yield and nondestructive recovery of the target material. Optical absorption spectroscopic and thermogravimetric analyses show that about 60% of the nanotubes in the starting material is extracted with a purity more than 90 wt %.