|
:: research survey ::
To Catch a Bomb
The webs Ling Zang spins are made of fibers thousands of time thinner than a spider's silk, and far more sensitive.
That's because he's not hunting insects; he's using so-called nanowires to snag molecules that indicate the presence of explosives.
An assistant professor of chemistry and biochemistry, Zang has received a five-year, $592,000 grant from the National Science Foundation to further develop his work on the fabrication of organic-based nanowires.
The NSF is funding Zang's research through its CAREER program, which helps promising scholars establish their research a at high level and integrate research with teaching. SIUC faculty have received eight of the prestigious grants over the past few years.
Zang and his students are developing a new generation of extremely acute sensing devices at the nanometer scale. (Generally speaking, nanomaterials have at least one dimension that measures less than 100 nanometers. To put that in perspective, your average human hair measures roughly 100,000 nanometers across.)
The infinitesimally small threads Zang works with are strings of molecules constructed with specific geometries. Together, these so-called nanowires act as a super-fine filter that can catch single airborne molecules from explosives (such as TNT) or poisonous substances (such as hydrazine).
Zang collaborates with University of Illinois chemist Jeff Moore, who makes specially functionalized organic molecules. Zang then uses those molecules to fabricate the nanowires at SIUC. The University is patenting the technology on behalf of the two scientists.
The technology could be a vast improvement over current sensors in terms of sensitivity to extremely low levels of telltale molecules. Future research also may improve the selectivity of such instruments, which refers to their ability to detect various substances.
Even though they may be solid substances, bombs and TNT give off trace amounts of vapor—a few parts per billion or per trillion in the atmosphere. For instance, a landmine buried beneath soil emits about 40 parts per trillion of TNT into the atmosphere.
A typical electronic sensor, such as those used in airport screening, can detect vapors at 100 parts per trillion. But Zang has evidence the materials he fabricates can detect levels below 10 parts per trillion.
"This is a newer technology that would provide better sensitivity and minimize problems like having false positives," says Zang. "As you can imagine, you don't want many false positives when you're dealing with explosives."
When the molecules are strung together in nanowire form, sort of like plates in a stack, they can be excited by ultraviolet light. In other words, the nanowires are fluorescent.
But when a TNT molecule lands on the matrix of nanowires, it "quenches," or turns off, the fluorescence. That quenching can be detected by the electronics package with which the nanowire filter is mated.
Another type of nanowire with which Zang is experimenting uses a different approach to detect poisons such as hydrazine, a gas used in submarine environments and rocket fuel.
With the NSF funding, Zang is experimenting with different geometric structures for the nanowires, looking for optimal performance. He and Moore also are working to synthesize organic molecules with improved sensitivity and selectivity—the ability to detect a greater range of substances—for the nanowire building blocks.
Finally, Zang will use the grant to explore marrying two types of sensors—optical and electronic—into a new hybrid sensing technology.
Zang's laboratory includes four graduate students, one postdoctoral fellow, three graduate students he shares with other researchers, and several undergraduate students.
"I see [the CAREER award] as an award for my whole group," he says.
"Without their hard work, I can't do anything. I'm so proud of them."
—by Tim Crosby
Comments: Perspectives Webmaster
Copyright © 2007, Board of Trustees, Southern Illinois University | Privacy Policy
|
