ABSTRACT
Nanotechnology provides the ability to work at the molecular level, atom by atom, to create large structures with fundamentally new molecular organization. It is essentially concerned with materials, devices, and systems whose structures and components exhibit novel and significantly improved physical, chemical, and biological properties; phenomena; and processes because of their nanoscale size. As one class of nanostructured materials, carbon nanotubes (CNTs) have been receiving much attention due to their remarkable mechanical properties and unique electronic properties as well as the high thermal and chemical stability and excellent heat conduction. CNTs have a large surface-to-volume ratio and aspect ratio with the diameter of a few nanometers and length up to 100
µ
m so that they form an extremely thin wire, a unique one in the carbon family, with the hardness of diamond and the conductivity of graphite. Diamond is the hardest substance found in nature and is an insulator, but graphite is one of the softest conducting materials (pencils use graphite, and graphite is also often used as a lubricant to allow two surfaces to slide freely). Because the electronic property of CNTs is a strong function of their atomic structure and mechanical deformations, such relationships make them useful when developing extremely small sensors that are sensitive to the chemical and mechanical or physical environment. In this chapter, CNTs for chemical and physical sensor applications are discussed. Sensor technology commands much attention because sensors have the ability to provide immediate feedback on the environment in places where our own five sensors of taste, sight, hearing, touch, and smell cannot go or are not sensitive enough. Advances in chemical and physical sensor technology are continuously needed for improved sensitivity and fast response to extract more-accurate and -precise information from changes in the environment.
