Chemists' work on peroxide bomb detectors shows promise

In the fight against terrorism, one of the main goals of law-enforcement and security agencies is to stop terrorist attacks before they can happen.

Early detection is essential, and work being done by University of Nebraska-Lincoln chemists could give those agencies the tools they need to detect the easy-to-make and highly explosive bombs that came be made from peroxide compounds that are sold at virtually hardware store.

UNL's Gerry Harbison and Jody Redepenning have been investigating two promising, but different methods of detection -- Harbison researching the ability of nuclear magnetic resonance (NMR) machines to target the substances and Redepenning looking into chemical "sniffers" that would sense their presence.

The work started last fall after Harbison returned to Lincoln from London, where he had attended an international conference -- and missed going through London's Kings Cross Station the day terrorists bombed it only because of a last-minute change of plans. He was visiting his sister in London following the conference and when it came time for him to fly home, he told her he planned to take the train to the airport. But he said she talked him out of it by telling him, "Don't be a cheapskate. Take a cab."

He said the close call gave him a keener interest than he might otherwise have had in the materials the attackers used. And what he learned about the materials gave him an inspiration about what he and colleagues in the UNL chemistry department might be able to do to help prevent future attacks.

"I wasn't even aware of these molecules, and it turned out they're all peroxides," he recalled. "There's triacetone triperoxide, which you can make out of acetone and hydrogen peroxide and battery acid, and you can buy all these goods in a hardware store. And the other one is HMDT (hexamethylene triperoxide diamine), which is the same thing, but substitute sterno for the acetone. These things are trivial to cook up."

They're also cheap, easy to detonate, highly explosive (hit a tiny, 10-milligram speck of it with a hammer and it sounds like a rifle has gone off), and extremely dangerous to work with. If you don't care about your personal safety, they would be the weapon of choice, Harbison said.

"I though about this and I realized, boy, I've done detection work on contraband for the Department of Defense using nuclear magnetic resonance. We have one of the best peroxide chemists in the country in Pat Dussault, the department chair, and we have Jody Redepenning, and electrochemist who has some ideas on how to detect this things if they're in the atmosphere, using what are essentially chemical sniffers," Harbison said.

Harbison and Redepenning said early research in both detection areas has shown enough promise that UNL has submitted a proposal to the Department of Homeland Security to build experimental models of each.

"It turns out there's probably a unique magnetic resonancing signature of these things, and we're hoping we can detect that," Harbison said. "They actually have the highest nitrogen frequency of anything I've ever seen."

Because of that high nitrogen frequency, Harbison said an NMR detector would need only a low-field magnet or even no magnet at all to detect the substances. The ability to detect low-frequency radio waves, like those in the AM band, are all that's needed to detect the Nitrogen 14 isotope, for example.

"What it means is you just beam low-frequency radio waves into the sample, and the frequencies are so low, they'll penetrate baggage really well," he explained. "The idea is if you sit right on the frequency of any of these materials, you can actually see them absorb light in the AM radio band. When you pick up that signature, some bells should go off somewhere."

In the case of the chemical sniffer, Redepenning said a workable detection device would also be relatively inexpensive and small, probably the size of wristwatch or smaller.

"My detector is constructed from two electrodes that are separated by a small gap, and this gap is covered with a nonconducting polymer," he said. "The molecules that we're interested in are strong oxidants, they're peroxides, so they oxidize the polymer to make it conductive. This should increase the passage of current between the two electrodes in the detector. But the trick is: Is it sensitive enough? Will it work fast enough? And I suppose you could ask, is it discriminating enough to sense between this class of molecules that we're interested in and some other oxidant?

"Certainly, all the pieces are there to make it work. We haven't actually demonstrated it yet, but there are a number of similar things around, not involving these exact molecules directly, but involving similar ones. I would be surprised if this design doesn't work at some level. The question is: Does it work well enough and is it economical enough?"

CONTACTS: Gerry Harbison, Professor, Chemistry, (402) 472-9346 (gharbison1@unl.edu)

Jody Redepenning, Assoc. Professor, Chemistry, (402) 472-3533