Boffins build nanotube gas detector

Minute traces of toxic gases now detectable

Carbon nanotubes have been used to build the most sensitive electronic detector yet

Chemical engineers at MIT have used carbon nanotubes to build the most sensitive electronic detector yet for sensing deadly gases.

The technology can detect the presence of harmful gases such as sarin, mustard gas, ammonia and VX nerve agents.

It has the potential to be used as a low-cost, low-energy device that could be carried in a pocket or deployed inside a building to monitor hazardous chemicals.

"We think this could be applied to a variety of environmental and security applications," said Michael Strano, the Charles and Hilda Roddey Associate Professor of Chemical Engineering at MIT, and senior author of the paper.

The super-sensitive detector is built using an array of carbon nanotubes aligned across microelectrodes.

Each tube consists of a single-layer lattice of carbon atoms, rolled into a long cylinder which acts as a molecular wire.

When a particular gas molecule binds to the carbon nanotube, the tube's electrical conductivity changes. Because each gas affects conductivity differently, gases can be identified by measuring the conductivity change after binding.

According to the paper, published in Angewandte Chemie, the sensor has exhibited record sensitivity to molecules mimicking organophosphate nerve toxins such as sarin.

It can detect minute quantities as low as 1 femtomole, roughly equivalent to a concentration of 25 parts per trillion.

The nanotube sensors require just 0.3mW to run, so one sensor could run essentially forever on a regular battery.

"It is something that could sit in the corner of a room and you could just forget about it," said Strano.

The scientist reckons that this is the first nanotube sensor that is passively reversible at this level of sensitivity, allowing the sensor to detect a series of gas exposures in rapid succession.

The work was funded by the US Department of Homeland Security. Similar research into the use of graphene to detect gases is being done by other researchers.