Purification, cutting, and sidewall functionalization of multiwalled carbon nanotubes using potassium permanganate solutions

In this work multiwalled carbon nanotubes were examined using a combination of thermal annealing followed by chemical treatments with potassium permanganate solution. Functionalization with carboxylic acid moieties through this newly devised process simultaneously purified and cut the nanotubes. A cutting procedure using potassium permanganate that could keep or remove the MnO2 has not been previously reported, making this study a stepping stone to further functionalization/application opportunities. One such further functionalization was explored here with alkyl groups, through the generation of an amide linkage. A very detailed standard suspension test was performed on this material. What was found was an increased suspension stability toward polar solvents for the nanotubes with high concentrations of MnO2 deposits, and in nonpolar solvents the nanotubes with large alkyl chains attached were observed, thus proving it to be a versatile treatment.