Carbon nanotubes (CNTs): A small review

Carbon nanotubes (CNTs) are allotropes of carbon with a nanostructure that can have a length-to-diameter ratio greater than 10,000,000 and as high as 40,000,000 as of 2004. 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 cylindrical nanotube usually has at least one end capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is in 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.[…]

Recent Developments on Carbon nanotubes:

• Lack Of Thermoelectric Effect Is Cool Feature In Carbon Nanotubes: Metallic carbon nanotubes have been proposed as interconnects in future electronic devices packed with high-density nanoscale circuits. But can they stand up to the heat?[1]
• Cautionary Note In Use Of Carbon Nanotubes As Interconnects: Researchers have used scanning tunneling microscopy to confirm remarkable changes in the fundamental electronic behavior when double-walled carbon nanotubes are subject to radial deformations and torsional strain. The work reported in Nano Letters reveals that squashing and twisting a double-walled nanotube opens an electronic band gap in an otherwise metallic system, which has major ramifications on the use of carbon nanotubes for electronic and NEMS applications.[2]
• Breakthrough In Production Of Double-walled Carbon Nanotubes: In recent years, the possible applications for double-walled carbon nanotubes have excited scientists and engineers, particularly those working on developing renewable energy technologies. These tiny tubes, just two carbon atoms thick, are thin enough to be transparent, yet can still conduct electricity. This combination makes them well-suited for advanced solar panels, sensors and a host of other applications[3]