According to Meyer, scientists have known for decades that hemes, a naturally occurring group of compounds that contain iron atoms, can break up organohalides. The most well-known heme is hemoglobin, a compound in red blood cells that carries oxygen.
"There's a lot of speculation that hemes in proteins are what cells use to defend themselves from organohalides," Meyer explained. "We can buy hemes we don't have to extract them from protein or anything but when you remove them from their naturally occurring environment, you tend to oxidize them."
In their oxidized state, hemes are no longer useful for breaking down organohalides. Hemes can be re-activated using chemical or electrochemical techniques, but Obare wanted to try using a practical, easily available energy source to power the re-activation: sunlight. She decided to try to take advantage of titanium dioxide's abilities as a photocatalyst, a substance that promotes chemical reactions in other nearby materials when exposed to light.
"I anchored hemin on porous thin films of nanocrystalline titanium dioxide, and when I exposed the system to light, the hemin was activated to a reduced state where it reacted rapidly with organohalides, producing much better results than I expected," Obare explained. "I've even been able to recycle and reactivate the thin films for further organohalide degradation."
Meyer noted that there's still a lot of development work to be done, not the least of which is figuring out exactly how the chemistry of the new system works. But he speculated that scientists might someday be able to insert a si
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Contact: Phil Sneiderman
prs@jhu.edu
410-516-7160
Johns Hopkins University
9-Sep-2003