Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology.

SWCNT (Single Wall Carbon Nanotube)

Single-wall nanotubes (SWNT) are tubes of graphite that are normally capped at the ends. They have a single cylindrical wall. The structure of a SWNT can be visualized as a layer of graphite, a single atom thick, called graphene, which is rolled into a seamless cylinder.

Most SWNT typically have a diameter of close to 1 mm. The tube length, however, can be many thousands of times longer.

SWNT are more pliable yet harder to make than MWNT. They can be twisted, flattened, and bent into small circles or around sharp bends without breaking.

SWNT have unique electronic and mechanical properties which can be used in numerous applications, such as field-emission displays, nanocomposite materials, nanosensors, and logic elements. These materials are on the leading-edge of electronic fabrication, and are expected to play a major role in the next generation of miniaturized electronics.

Laser method for the manufacturing of carbon nanotubes:

Laser ablation was first used for the synthesis of fullerenes. In this method, a graphite target is vaporized by laser irradiation under flowing inert atmosphere at temperatures near 1200°C, as shown in Fig. The laser vaporization produces carbon species, which are swept by the owing gas and accumulate on a water-cooled collector. SWCNTs remarkably uniform in diameter can be produced when the graphite target is doped with a small amount of transition metals such Ni and Co.

Schematic diagram of LASER ablation method