*2.1.6 Procedure for synthesis of CNTs by Laser Ablation method*

Laser Ablation method is a Physical Vapor Deposition method in which graphite target is vaporized by laser source **Figure 3**. In this method the graphite target is placed at the center of quartz chamber filled with argon gas and maintained at 1200°C. The graphite target is vaporized by either continuous laser source or pulsed laser source. The vaporized target atoms (carbon) are sweeped toward cooled copper collector by the flow of argon gas. The carbon atoms are deposited and grown as CNTs on cooled copper collector. In case of continuous laser beam, the carbon atoms are continuously vaporized whereas in case of pulsed laser beam the amount of CNTs produced can be monitored as each shot of pulsed laser beam is directly proportional to the amount of carbon atoms vaporized [26]. By this method multiwalled carbon nanotubes are synthesized and to synthesize single-walled carbon

**Figure 3.** *Laser ablation method—schematic representation.*

nanotubes catalyst nanoparticles of Fe, Co, Ni are used. The obtained CNTs are further purified to get the pure form of CNTs.
