These gas detectors provide a new way to determine if drugs or nanoparticles harm cells or to study how cells communicate with one another. Based on metal oxide nanotubes, the new sensors are a hundred to 1,000 times more sensitive than current devices based on thin films and are able to act as multiple sensors simultaneously.
Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. Thus, the more surface available, the more sensitive the sensor will be. Scientists are interested in developing gas sensors based on nanotubes because, having walls that are only a few nanometers thick, they are almost all surface.
The National Institute of Standards and Technology (NIST) research group built upon a design using a sheet of aluminum oxide about the thickness of a human hair and perforated with millions of holes about 200 nanometers wide. With the nanosized pores serving as a mold, the researchers dipped the aluminum oxide sheet in a solution of tungsten ions, coating the interior of the pores and casting the nanotubes in place. After the nanotubes were formed, the team deposited thin layers of gold on the top and bottom of the aluminum oxide membrane to act as electrical contacts.
The sensor’s high sensitivity derives from its design, which ensures that any sensor response is the result of the gas interacting with the interior of the nanotube. The researchers also note that this same technique can easily be adapted to form nanotubes of other semiconductors and metal oxides so long as the ends of the nanotubes remain open.
COMPAMED.de; Source: National Institute of Standards and Technology