Overview

Chemical and biological sensors are found across a broad range of application areas. An ideal sensor is one with high sensitivity, fast response time, selectivity, and compactness. Achieving this goal is difficult, and current sensor technologies utilize a variety of approaches, often relying on optical techniques. As progress in the miniaturization of electronic components is continued, electronic detection of chemical and biological species may provide an alternative to these established technologies. In its simplest form, electronic detection measures the change in conductivity of a material upon exposure to analytes. One aspect of electronic sensing that can benefit from nanomaterials is the sensitivity, because nanomaterials, carbon nanotubes in particular, have a large surface-to-volume ratio. Indeed, a carbon nanotube is entirely a surface material, and its circumference is comparable to the size of many small analytes. Thus, even a single analyte that attaches on the surface of a carbon nanotube can significantly impact the nanotube conductivity. This "single-molecule" detection capability is difficult to achieve with bulk or thin film materials.

In this chapter, we present the recent progress in developing a basic understanding of the impact of chemical and biological species on the conductance of carbon nanotubes, and discuss laboratory demonstrations of simple electronic detection approaches. There are several different physical mechanisms that can lead to changes of the nanotube conductivity in the presence of analytes: charge transfer, changes in electron scattering, contact effects, and capacitance changes. As we will see in this chapter, carbon nanotube field-effect transistors are often utilized...