A team of researchers from the National Institute of Standards and Technology (NIST), George Mason University and the University of Maryland has made nano-sized sensors that detect volatile organic compoundsharmful pollutants released from paints, cleaners, pesticides and other productsthat offer several advantages over today's commercial gas sensors, including low-power room-temperature operation and the ability to detect one or several compounds over a wide range of concentrations.
The recently published work* is proof of concept for a gas sensor made of a single nanowire and metal oxide nanoclusters chosen to react to a specific organic compound. This work is the most recent of several efforts at NIST that take advantage of the unique properties of nanowires and metal oxide elements for sensing dangerous substances.
Modern commercial gas sensors are made of thin, conductive films of metal oxides. When a volatile organic compound like benzene interacts with titanium dioxide, for example, a reaction alters the current running through the film, triggering an alarm. While thin-film sensors are effective, many must operate at temperatures of 200 C (392 F) or higher. Frequent heating can degrade the materials that make up the films and contacts, causing reliability problems. In addition, most thin-film sensors work within a narrow range: one might catch a small amount of toluene in the air, but fail to sniff out a massive release of the gas. The range of the new nanowire sensors runs from just 50 parts per billion up to 1 part per 100, or 1 percent of the air in a room.
These new sensors, built using the same fabrication processes that are commonly used for silicon computer chips, operate using the same basic principle, but on a much smaller scale: the gallium nitride wires are less than 500 nanometers across and less than 10 micrometers in length. Despite their microscopic size, the nanowires and titanium dioxide nanoclusters they'r
|Contact: Michael Baum|
National Institute of Standards and Technology (NIST)