Carbon Nanotube Radio

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been synthesized with length-to-diameter ratio of up to 132,000,000 : 1, which is significantly greater than any other material. These cylindrical carbon molecules have novel properties which make them potentially useful in many applications in nanotechnology, electronics, optics, and other fields of materials science. Nanotubes are members of the fullerene structural family (one dimensional form of fullerenes), which also includes the spherical buckyballs. Fullerenes were accidentally discovered by Kroto and Smalley in 1985, when they found strange results in mass spectra of evaporated carbon samples (Kroto et al. 1985). Since the discovery in 1991 by Iijima (Iijima, 1991), carbon nanotubes have been investigated by many researchers all over the world both from fundamental point of view and for future potential applications in the field of energy storage, molecular electronics, nanomechanical devices and composite materials. However, the real applications are still under development. 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 18 centimeters in length. Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). Figures 1 a) and b) show the scanning tunneling microscopic (STM) and transmission electron microscopic (TEM) images of a single-walled carbon nanotube. Figure 2 illustrates the scanning electron microscopic (SEM) image of carbon nanotube bundles. Single-walled nanotubes are an important variety of carbon nanotube because they exhibit electric properties that are not shared by the multi-walled carbon nanotube (MWNT). In particular, their band gap can vary from zero to about 2 eV and their electrical conductivity can show metallic or semiconducting behavior, whereas MWNTs are zero-gap metals. Single-walled nanotubes are the most likely candidate for miniaturizing electronics beyond the micro electromechanical scale currently used in electronics. The most basic building block of these systems is the electric wire, and SWNTs can be excellent conductors. One useful application of SWNTs is in the development of the first intramolecular field effect transistors (FET). Multi-walled nanotubes (MWNTs) consist of multiple rolled layers (concentric tubes) of graphite. There are two models which can be used to describe the structures of multi-walled nanotubes. Single Walled Nanotubes (SWNTs) can be considered as long wrapped graphene sheets. As stated before, nanotubes generally have a length to diameter ratio of about 1000 so they can be considered as nearly one-dimensional structures. Figure 3 shows some SWNTs with