Tuesday, August 15, 2006

A New Way to Make Ultrasensitive Explosives Detectors

Continued from page 1

By Kevin Bullis

Rauh says that a product could be available within five years, but it would probably not reach the one-molecule detection level possible in a lab. "Single molecule detection is done under highly specialized circumstances," he says; but for airports, what the method offers "is the possibility of detecting a whole spectrum of different chemicals and identifying them at parts per billion levels."

The work is one example in a growing field of research: developing new methods for creating carefully spaced nanostructures with well-controlled sizes, shapes, and spacings, which will be essential for the most sensitive devices. Williams says that in the past "having two silver nanoparticles that are exactly the right diameter and separated by only one or two nanometers has been an accident. It just simply hasn't been possible to build such a thing. This [HP] process gives you almost for free the ability to do that."

Chad Mirkin, professor of chemistry at Northwestern University, says the technique is "a clever way of arranging particles on a surface. And the ability to do that can impact many areas, ranging from catalysis to optics and electronics." He notes, however, that the researchers have yet to demonstrate its versatility with various metals, and have not yet tested it for use in sensors. Furthermore, says Mirkin, the new method will have to compete with other experimental ways of creating arrays of nanoparticles of precise sizes and distributions.