Pristine single-walled carbon nanotube purity evaluation by using 1H NMR spectroscopy

Proper purity characterization of single-walled carbon nanotubes (SWCNTs) is an increasingly hot topic in the area of carbon nanotechnology. There are inconsistencies in purity characterization of SWCNT from manufacturers and in the literature. Purity of "as received," oven dried, and NaHCO3-washed SWCNTs of three commercially available brands (NanoLab, SWeNT, and HiPco) is explored by using a consistent methodology via proton nuclear magnetic resonance (H-1 NMR) spectroscopy comparison, across three NMR solvents: DMSO-d(6), CDCl3, and D2O. Important insights into the purity of commercially available SWCNT and the importance of washing (cleaning) samples before use are offered.