Carbon Nanostructures: Bucky Balls and Nanotubes
This chapter focuses on nanostructures produced by carbon. It may seem strange to devote a chapter to a single element, but there is such a plethora of nanostructures composed of carbon that it is easy to justify several books (as indeed there are), never mind a chapter on them. Here we will pass lightly over the subject and discuss how and why these structures form and their basic properties. Their use in nanotechnology is described in Chapter 5, but their applications are diverse and references to carbon nanostructures can be found throughout the rest of this book.
3.1 Why Carbon?
Carbon is a light, simple element: Its atoms contain just six electrons, two of them being core (1s) electrons and the remaining four (2sp) available for bonding with other atoms. It is the slightly schizophrenic nature of the chemical bonding by these four that naturally gives carbon a diversity of forms. The details of the environment in which the atoms come together (pressure, temperature, etc.) determine the types of bonds. For example, we are very familiar with the two very different bulk forms (allotropes) of carbon—that is, graphite and diamond that result from different types of bonds. The bonding in diamond and graphite and why they adopt their particular crystal structures is illustrated in Fig. 3.1.