Carbon nanotubes (CNTs)

Carbon nanotubes (CNTs) are allotropes of carbon with a nanostructure that can have a length-to-diameter ratio of up to 28,000,000:1[1], which is significantly larger than any other material. These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential uses in architectural fields. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Their final usage, however, may be limited by their potential toxicity. Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs. The ends of a nanotube might be capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to several millimeters in length (as of 2008). Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamonds, provides the molecules with their unique strength. Nanotubes naturally align themselves into "ropes" held together by Van der Waals forces. Under high pressure, nanotubes can merge together, trading some sp² bonds for sp³ bonds, giving the possibility of producing strong, unlimited-length wires through high-pressure nanotube linking.Techniques have been developed to produce nanotubes in sizeable quantities, including arc discharge, laser ablation, high pressure carbon monoxide (HiPCO), and chemical vapor deposition (CVD). Most of these processes take place in vacuum or with process gases. CVD growth of CNTs can occur in vacuum or at atmospheric pressure. Large quantities of nanotubes can be synthesized by these methods; advances in catalysis and continuous growth processes are making CNTs more commercially viable. The strength and flexibility of carbon nanotubes makes them of potential use in controlling other nanoscale structures, which suggests they will have an important role in nanotechnology engineering. Because of the carbon nanotube's superior mechanical properties, many structures have been proposed ranging from everyday items like clothes and sports gear to combat jackets and space elevators. Carbon nanotubes have many properties—from their unique dimensions to an unusual current conduction mechanism—that make them ideal components of electrical circuits. A paper battery is a battery engineered to use a paper-thin sheet of cellulose (which is the major constituent of regular paper, among other things) infused with aligned carbon nanotubes. The nanotube’s versatile structure allows it to be used for a variety of tasks in and around the body. Although often seen especially in cancer-related incidents, the carbon nanotube is often used as a vessel for transporting drugs into the body. The nanotube application potentially allows for the drug dosage to be lowered by localizing its distribution. Carbon nanotubes have been implemented in nanoelectromechanical systems, including mechanical memory elements and nanoscale electric motors.

3D model of three types of single-walled carbon nanotubes

Further information:

1. H.W. Kroto, J.R.Heath, S.C. O’Brien, R.F. Curl, R.E. Smalley, C60: Buckminsterfullerene, Nature 318 162 (1985)
2. S. Iijima, Helical microtubules of graphitic carbon, Nature 354 56 (1991)
3. A. Oberlin, M. Endo, and T. Koyama. High resolution electron microscope observations of graphitized carbon fibers Carbon, 14, 133 (1976)
4. J.A.E. Gibson. Early nanotubes? Nature, 359, 369 (1992)
5. Л. В. Радушкевич и В. М. Лукьянович. О структуре углерода, образующегося при термическом разложении окиси углерода на железном контакте. ЖФХ, 26, 88 (1952)
6. L. X. Zheng et al. (2004). Ultralong Single-Wall Carbon Nanotubes. 3. pp. 673–676.
7. Mingo, N.; Stewart, D. A.; Broido, D. A.; and Srivasta, D. (2008). "Phonon transmission through defects in carbon nanotubes from first principles". Physical Review B 77: 033418.
8. Kolosnjaj J, Szwarc H, Moussa F (2007). "Toxicity studies of carbon nanotubes". Adv Exp Med Biol. 620: 181–204.
9. Porter, Alexandra (November 2007). "Direct imaging of single-walled carbon nanotubes in cells". Nature Nanotechnology 2 (11): 713–7
10. Gannon, Christopher J.; Cherukuri, Paul; Yakobson, Boris I.; Cognet, Laurent; Kanzius, John. S.; Kittrell, Carter; Weisman, R. Bruce; Pasquali, Matteo; Schmidt, Howard K.; Smalley, Richard E.; Curley, Steven A. (2007). "Carbon nanotube-enhanced thermal destruction of cancer cells in a noninvasive radiofrequency field". Cancer Dec. 2007: 2654.
11. Article Carbon nanotubes (CNTs) from Wikipedia, the Free Enciclopedia. Available under the license Creative Commons Attribution-Share Alike.

 Back to Russian