Large-Scale Production of Single-Wall Carbon Nanohorns with High Purity

To increase the practical daily capacity to produce single-wall carbon nanohorns (SWNHs) with high purity by CO2 laser ablation of graphite, we made a new three-chamber system composed of a target reservoir, a laser ablation chamber, and a collection chamber. The frequency of exchanging targets was reduced by increasing the target size (diameter, 10 cm; length, 50 cm), and the time taken to exchange targets was reduced by adding an automated exchange mechanism. Most of the SWNHs produced in the laser ablation chamber were immediately swept into the collection chamber by an Ar gas carrier. This avoided the problem of fluffy SWNHs blocking the laser beam irradiating the target and enabled the CO2 laser to be operated continuously. The resulting SWNHs had a purity of 92−95% under the optimized conditions of laser power density (15−30 kW/cm2) and target rotation speed (1−3 rpm). This increase in purity represents a remarkable improvement on the previous level of 85−90%. A practical production capacity of 1 kg/day was achieved, which is about 100 times greater than the daily capacity attained by the previous single-chamber system.