Carbon Nanotubes (CNT), which were discovered by Iijima in 1991, are composed entirely of carbon atoms, as is C₆₀¹⁾. As the name implies, this carbon structure is shaped like a tube on a nanometer scale. In 1991, Hufman and Kraetschmer reported a procedure for the preparation of C₆₀ by an arc discharge. Many researchers had used this technique to obtain C₆₀ from the soot which had collected on the anode. However, Iijima focused his attention on the soot which had accumulated on the cathode carbon rod. In this soot, Iijima found a needle like substance which he characterized as carbon nanotubes. These early nanotubes were multi-walled carbon nanotubes (MWCNT), composed of many layers. Two years later, single-walled carbon nanotubes (SWCNT) were discovered. In 1996, Smalleys developed a mass production method of SWCNT²⁾ and since then, research of carbon nanotubes has progressed rapidly.
Today, researchers are making advances in the applications of carbon nanotubes as probes for Scanning Probe Microscopy, nano-tweezers³⁾, field-emitter of Field Emission Display (FED)⁴⁾, nanoelectronics devices⁵⁾, and hydrogen fuel cells⁶⁾.