Nature is the origin of all things.
Carbon is an old but new material. It has been used forcenturies going back to antiquity, but yet many new crystalline forms of carbon have only recently been experimentally discovered in the last few decades. These newer crystalline forms include buckyballs, carbon nanotubes (CNTs), and graphene, where the latter two are illustrated in Figure 1.1. Furthermore, carbon nanotubes come in two major flavors, the single-wall and multi-wall varieties, as shown in Figure 1.1a and b respectively. The newer forms of carbon have significantly contrasting properties compared with the older forms of carbon, which are graphite and diamond. In particular, they share in common a hexagonal lattice or arrangement of carbon atoms. In addition, CNTs and graphene occupy a reduced amount of space compared with their older siblings; hence, they are often referred to as reduced-dimensional or low-dimensional solids or nanomaterials for short. To give a comparative (order of magnitude) idea of the critical size scales of these nanomaterials, nanotubes are about 10 000 times thinner than human hair, and graphene is about 300 000 times thinner than a sheet of paper. The typical diameter of nanotubes range from about 1 to 100 nm, and graphene ideally has the thickness of a single atomic layer (∼3.4 Å). Fundamentally, it is the combination of the reduced dimensions and the different lattice structure that leads to the fascinating properties unique to nanotubes and graphene.