Length reduction of multi-walled carbon nanotubes via high energy ultrasonication and its effect on their dispersibility

Length dependent dispersibility of carboxylated multiwalled carbon nanotubes is presented using a novel approach that ensures the same diameter and the degree of functionalization. The longer multiwalled nanotubes were reduced in length by ultrasonication and then their dispersibility was studied in comparison to the original tubes. Colloidal studies showed dependence on the length where the shorter tubes showed higher aggregation in terms of larger particle size, zeta potential and lower critical coagulation concentrations in the presence of electrolytes. It is hypothesized that the longer tubes entangled more leading to a more complex electrostatic double layer that increased their stability.