A test strip changes from blue to colorless in the presence of peroxide-based explosives like those favored by terrorists. Credit: Allen Apblett |
Scientists
this week described development and successful initial tests of a spray-on
material that both detects and renders harmless the genre of terrorist
explosives responsible for government restrictions on liquids that can
be carried onboard airliners. They reported on the new ink-like
explosive detector/neutralizer at the 241st National Meeting &
Exposition of the American Chemical Society (ACS).
“This
stuff is going to be used anywhere terrorist explosives are used,
including battlefields, airports, and subways,” said study leader Allen
Apblett, Ph.D. “It’s going to save lives.”
The
material is a type of ink made of tiny metallic oxide nanoparticles —
so small that 50,000 could fit inside the diameter of a single human
hair. The ink changes color, from dark blue to pale yellow or clear, in
the presence of explosives. It also changes from a metallic conductor to
a non-conducting material, making electronic sensing also possible.
This
color-change feature allows the material to work as a sensor for
quickly detecting the presence of vapors produced by explosives, Apblett
said. Soldiers or firefighters could wear the sensors as badges on
their uniforms or use them as paper-based test strips. Airports, subways
and other facilities could use the sensors as part of stationary
monitoring devices. The sensors could even be engineered into jewelry
and cell phones, the scientist added.
The
same color-changing material can also serve as an explosives
neutralizer. Firefighters and bomb squad technicians could spray the ink
onto bombs or suspicious packages until the color change indicates that
the devices are no longer a threat, Apblett said. Technicians could
also dump the explosives into vats containing the ink to neutralize
them.
Apblett
notes that authorities are concerned about peroxide-based explosives,
made from hydrogen peroxide, which are easy to make and set off. These
explosives first drew public attention in 2001, when thwarted “shoe
bomber” Richard Reid tried to use one such substance as the detonator
onboard a commercial airliner. In particular, they are concerned about a
substance called triacetone triperoxide, or TATP, sometimes used in
suicide vests and improvised explosive devices that have claimed such a
toll among troops and civilians. However, current methods of detecting
this explosive are ineffective, allowing the material to easily escape
detection at airports and other locations.
The
new ink provides a quick way to detect and test these explosives, which
might be hidden in clothing, food, and beverages. The ink contains
nanoparticles of a compound of molybdenum, a metal used in a wide
variety of applications including missile and aircraft parts. The dark
blue ink reacts with the peroxide explosives and turns yellow or clear.
When
used as an electronic sensor, the highly-sensitive material is capable
of detecting TATP vapors at levels as low as a 50 parts per million,
equivalent to a few drops of the vapor in a small room, within 30
seconds. The same chemical reaction allows the materials to serve as an
explosives neutralizer. In lab studies, the scientists showed that they
could add the material to TATP or HMTD and make them nonexplosive.
“This
does a really good job of neutralizing terrorists’ explosives,” said
Apblett, a chemist at Oklahoma State University in Stillwater, Okla.
“I’m excited to see it moving from the lab to the real world.”
The
material can also improve safety at laboratories that use explosive
chemicals. Recently, Apblett developed pellets containing the ink that
can be added to laboratory solvents to prevent the build-up of levels of
dangerous peroxides, which can cause accidental explosions. The
color-changing feature allows the users of the solvents know that they
are safe.
Apblett
and colleagues founded a company called Xplosafe to develop and market
the material. They hope to see the explosive detecting ink used in
airports in as little as a year.
The
scientists acknowledge funding from Memorial Institute for the
Prevention of Terrorism, the National Science Foundation, Oklahoma
Center for the Advancement of Science and Technology, Xplosafe, and
Oklahoma State University.
