Posted on 04/25/2009 3:15:34 PM PDT by decimon
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For more than a decade, chemical engineer Jiro Abe and colleagues at Aoyama Gakuin University in Japan have been studying the light-sensitive properties of photochromic materials, particularly those derived from a compound called hexaarylbiimidazole (HABI). In its natural state, HABI is colorless, but when ultraviolet light breaks one of the bonds in the molecule, it produces a version that is dark blue. The problem has been that the transformation takes tens of seconds or longer, so the only commercial application has been sunglasses that slowly darken.
When Abe's team began analyzing HABI's chemical structure through simulations and laboratory experiments, they found that by adding naphthalene to the compound, they could accelerate the color change to about 180 milliseconds. Adding a compound called cyclophane instead of naphthalene improved the clear-to-blue conversion even more--to about 30 milliseconds. Better still, Abe and colleagues report in the current issue of the Journal of the American Chemical Society, the cyclophane version of HABI reverts just as rapidly to its colorless state when the UV light source is turned off. And the compound is so stable that the reactions can be repeated thousands of times.
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(Excerpt) Read more at sciencenow.sciencemag.org ...
It would if not designed correctly. The UV blocker would have to be located behind this material, as with existing light-sensitive lenses.
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