Carbon nanotubes are another allotrope of carbon discovered after C60. Their radial dimensions are relatively small, with outer diameters typically ranging from a few nanometers to tens of nanometers, and inner diameters even smaller, some as small as about 1 nm. Their lengths are generally on the micrometer scale, with an extremely large length-to-diameter ratio, reaching 10³ to 10⁶. Therefore, carbon nanotubes are considered a typical one-dimensional nanomaterial. Since their discovery, carbon nanotubes have been hailed as the material of the future and have become one of the forefront fields of international science in recent years.