Carbon nanotubes having nanoscale dimension (1-D) have been well-known over the past 15 years. The molecules were first discovered by Iijima in 1991 when he was studying the synthesis of fullerenes by using electric arc discharge technique. The high resolution transmission electron microscopy (HRTEM) was employed for observation of that phenomenon. Carbon nanotubes that Iijima observed were so called multi-walled carbon nanotubes (MWNTs), nested as Russian dolls, containing at least two graphitic layers, and generally have inner diameters of around 4 nm. Two years later, Iijima and Ichihashi of NEC and Bethune and colleagues of the IBM Almaden Research Center in California synthesized single-walled carbon nanotubes (SWNTs). The SWNTs were synthesized by the same route of producing MWNTs but adding some metal particles to the carbon electrodes. The appearance of SWNT is quite different to that of MWNT. The individual tubes have very small diameters (typically ~ 1nm), and are curled and looped rather than straight. In the early 1990s, two research groups predicted electronic properties of individual SWNTs. From their calculations, they found that SWNTs can be either metallic or semiconducting depending on their chirality and diameter. By the end of that decade, these particular predictions were confirmed by experiments. In the early 1990s, two research groups predicted electronic properties of individual SWNTs. From their calculations, they found that SWNTs can be either metallic or semiconducting depending on their chirality and diameter. By the end of that decade, these particular predictions were confirmed by experiments.
Left side: HRTEM images of two MWNTs and Right side: SWNTs rope: each black circle is the image of one SWNT of the rope (From Journet et al., Physique 4 (2003) 986.)
In the meantime, a lot of reviews which provide a comprehensive overview with respect to the synthesis, characterization, applications, and the basic mechanical and electronic properties of carbon nanotube have appeared. In the Next time, the structure, synthesis, properties and applications of CNTs are discussed in details. Because of many interesting properties that carbon nanotubes exhibit, CNTs have emerged to be one of the most intensively investigated nanostructure materials. The field has been developed rapidly, and a number of publications per year have been increased almost exponentially. For instances, the number of publications exceeded three thousand in the year 2003. See more detail>> http://sites.google.com/site/nanomodern/Home/CNT