CHAPTER 1 I NTRODUCTION TO N ANOMATERIALS AND N ANOTECHNOLOGY G. Korotcenkov B. K. Cho 1. WHAT ARE NANOMATERIALS? Recent scientific research has discovered an important role for nanotechnologies in fields such as informa- tion technology, materials science, biology, medicine, engineering, electronics, physics, fiber-optic com- munication networks, chemistry, computer simulations, aerospace technology, advanced materials tech- nology, and chemical engineering (Feiner 2006; Wang et al. 2006; Mamalis 2007; Rickerby and Morrison 2007; Davenas et al. 2008; Meyer et al. 2009; Zhang and Webster 2009). As a result, a revolution of sorts has occurred in the search for approaches to attaining needed properties of materials: We have reached an era in which the control of physical, chemical, and biological properties of materials often takes place at the molecular and supramolecular levels. Just a few years ago, this ability seemed unrealistic. According to the International Union of Pure and Applied Chemistry (IUPAC), nanomaterials are defined as materials having sizes smaller than 100 nanometers (1 nm = 10 -9 m) along at least one dimension (length, width, or height) (Wikipedia 2009). For comparison, Table 1.1 lists the dimensions (sizes) of a number of well-known objects. In the range of crystallite sizes (<100 nm), and especially in the range smaller than 10 nm, large differences in the properties of nanomaterials and nanoparticles have been observed. For example, the exciton diameter in a semiconductor may be tens or hundreds of nanometers, the distance between domain walls in a magnet may be hundreds of nanometers, etc. So, nanostructures with characteristic size smaller than 10­100 nm can be considered as a special physical state, because the properties of materials formed with the participation of nano-sized structural elements 1