Electrothermal halogenation of carbon nanotube films

We report an innovative approach to halogenation of carbon nanotube (CNT) films. Application of bias voltage across horizontally aligned CNT films resulted in the electrothermal effect, which enabled us to chemically modify CNT films at the entirely controlled range of temperatures up to 300 °C. Such heated CNT membranes were exposed to gaseous halogens (Cl2, Br2, I2) whilst their electrical properties were monitored. The experiments were carried out at room temperature and 100-300 °C (in 50 °C steps) until no further change in electrical resistance could be seen. The procedure lasted less than one minute, during which we were able to successfully introduce up to 6.7%, 6.0% and 1.5% at. of Cl, Br and I into the CNT framework. In parallel, we observed a permanent increase in conductivity of the films and mild purification of the starting material due to the removal of various carbon-oxygen functional groups.