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Interview with the Chancellor
RAE: A Poet Post-Pulitzer
Car Talk
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Campus Currents
Penguins in Peril
Boundless Birch
Flash Gordon
Stamp of Approval
As Smelled on TV
Toxic Colors
Bio-fuel Accelerator
Tissue Engineering
Name that Worm
3D Pyramid Scheme

Campus Currents May 2007: Volume 4, Number 2

Toxic Colors

First responders wear respirators fitted with charcoal filters to avoid inhaling toxic fumes. Airborne toxins stick to the carbon in the filter, trapping the dangerous materials, but as the filters become saturated, chemicals will begin to pass through. The respirator can then do more harm than good by providing an illusion of safety. Right now, there is no easy way to determine when a filter is spent.

Michael Sailor, a UCSD chemistry professor, and his research group, working with partners at Tyco Electronics, have developed a visible indicator that can warn emergency workers when their masks are no longer effective.

It is made of carbon nanofibers assembled into repeating structures called photonic crystals. Because the photonic carbon is chemically similar to the activated charcoal in filters, it will absorb pollutants at the same rate. But unlike ordinary black carbon, the nanofibers are iridescent. Their crystals reflect specific wavelengths, or colors, of light. A natural example of this kind of structure is found in the wing scales of the Morpho butterfly, which give the insect its brilliant iridescent coloration. The nanofibers change color as the toxins accumulate—a visible indication of their capacity to absorb additional chemicals.

—Susan Brown