High-yield, nondestructive purification and quantification method for multiwalled carbon nanotubes

We have described a one-step, high-yield, nondestructive purification and processing method for multiwalled carbon nanotube (MWNT) containing soot using a conjugated organic polymer host. This host selectively suspends nanotubes relative to impurities. The fraction of available MWNTs suspended can be measured using electron paramagnetic resonance (EPR) and rises with increasing polymer mass before saturating at approximately 50% by mass for a soot to polymer mass ratio of 1:5. Thermogravimetric analysis can then be used to calculate the mass of nanotubes suspended and hence the purity of the original soot. Furthermore, this allows the calculation of numerical constants relating the EPR signal intensity to the nanotube mass, allowing the routine calculation of nanotube content. Finally the host polymer was removed by filtration, giving 91% pure nanotube material. In this case a yield of 17% pristine nanotubes was reclaimed from the soot. Full optimization of this process could lead to yields of up to 40%.