Safe and damage-less dry-purification of carbon nanotubes using FeCl3 vapor

The FeCl3-vapor treatment was proposed and developed for the purification of carbon nanotubes (CNTs). The FeCl3-vapor treatment combined with vacuum heating at 1000 °C efficiently removed various catalysts (Fe, Ni, Y, Mg, and Al) from single-wall and multi-wall CNTs. No damage was found in the purified CNTs with retained/enhanced G-band to D-band intensity ratios in Raman spectroscopy and elevated combustion temperatures in thermogravimetric analysis. Even if vapors of metal chlorides leak, they show low vapor pressure at ambient temperature and turn solid, significantly reducing the hazard. A safe and damage-less dry-purification method will promote various practical applications of CNTs. [Display omitted] •Safe dry-purification method of carbon nanotubes (CNTs) was developed.•Exposure to FeCl3 vapor efficiently removed Fe, Ni, Y, Mg, and Al from CNTs.•The purified CNTs had a retained/enhanced G/D ratio in Raman spectroscopy.•FeCl3 has a low vapor pressure at room temperature and solidifies even if leaked.