Researchers at the University of Massachusetts Amherst have created complex molecules containing zinc for use in portable sensors that quickly and reliably detect the presence of plastic explosives, a pressing need for soldiers in Iraq and other hostile environments.
Sensors containing the zinc complexes are also the first devices that allow the user to identify which type of explosive is present, since each metal complex has a unique response to explosives and explosive mimics.
“This is a big improvement over existing sensors based on polymers, since the metal complexes can discriminate between closely related explosives compounds,” says Michael Knapp, a professor of chemistry. “This ability is a real advantage for airport security personnel and law enforcement officials, who need to quickly detect and identify what type of explosives they are dealing with.”
Results of the study by Knapp, doctoral candidate Meaghan Germain and undergraduate student Thomas Vargo were published April 23 in the Journal of the American Chemical Society.
Knapp and Germain currently hold a patent for the zinc complexes, and are working with the UMass Amherst Office of Commercial Ventures and Intellectual Property to bring this technology to market. The research was supported by start-up funds provided by the University of Massachusetts Amherst.
The zinc complexes are naturally fluorescent, but they lose this ability when exposed to chemicals contained in plastic explosives, a phenomenon called quenching. Since each of the complexes react by losing different amounts of their fluorescent ability, they can be used to create sensor arrays that produce a different visual display when exposed to different explosives.
During testing, the sensors also responded quickly, since the zinc complexes are very efficient at changing energy states, making them suitable for hostile environments. “Of all the molecules that fluoresce, these go from a high energy state to a low energy state like falling off a cliff,” says Knapp. “They don’t lose energy gradually like metal complexes made with copper.”
“Identifying and distinguishing related compounds by optical methods is an enormous challenge for chemical sensing,” says Knapp. “The differential quenching of the zinc complexes is what permits discrimination within the closely related nitroaromatic family used in explosives.”
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