Efficient purification of single-walled carbon nanotube fibers by instantaneous current injection and acid washing

Abstract

Growth of carbon nanotubes is usually accompanied by the trapping of large amount of amorphous impurities and catalyst residue. So far, most purification methods have focused on powder-form products and their dispersions. Here, we present a simple yet highly efficient method to directly purify twist-spun single-walled carbon nanotube (SWNT) fibers by applying an instantaneous high current through the fiber. The generated Joule heat burns away the amorphous carbon species coated on SWNT bundles, and exposes Fe particles that can be easily washed by diluted acid, resulting in very clean fibers. The purified fibers, consisting of only larger-size and clean-surface SWNT bundles, show significantly enhanced electrical and mechanical properties. Our purification method is suitable to clean long continuous single-walled or multi-walled nanotube fibers fabricated in various ways and those containing a large amount of residual catalyst and co-deposited carbonaceous impurity.