As-synthesised single-walled carbon nanotubes (SWCNTs) are often contaminated with
amorphous carbon and residual catalyst particles. These contaminants have a detrimental effect
on the effective mechanical and electronic properties, limiting their performance in many
applications. A comparative series of SWCNT purifications including acid treatments, gas
phase purifications and recently-developed reductive purifications have been conducted using
a single commercial SWCNT type (Tuball™). Each of the purification procedures was selected
for its potential scalability to bulk quantities and evaluated for the extent of impurity removal,
SWCNT damage, and overall yield. Raman spectra confirmed that reductive purification using
sodium naphthalide gave the lowest D/G ratio, suggesting that the sp2
carbon framework was
most effectively preserved, while removing a large percentage of the metal impurities.
Conversely, nitric acid treatment was most effective at removing catalytic impurities, but the
sp2
carbon framework was most heavily damaged in the process. The development of scalable,
one pot, reductive separations provides a useful new approach to SWCNT purification.