Butterflies are proving to be quite generous as they inspire ideas for greater production of green fuels in addition to everything else they’ve inspired. From the March 26, 2012 news item on Nanowerk,
“We were searching the ‘art of blackness’ for the secret of how those black wings [from black butterflies] absorb so much sunlight and reflect so little,” Fan [Tongxiang Fan, Ph.D] explained.…
Fan’s team observed elongated rectangular scales arranged like overlapping shingles on the roof of a house. The butterflies they examined had slightly different scales, but both had ridges running the length of the scale with very small holes on either side that opened up onto an underlying layer.
The steep walls of the ridges help funnel light into the holes, Fan explained. The walls absorb longer wavelengths of light while allowing shorter wavelengths to reach a membrane below the scales. Using the images of the scales, the researchers created computer models to confirm this filtering effect. The nano-hole arrays change from wave guides for short wavelengths to barriers and absorbers for longer wavelengths, which act just like a high-pass filtering layer.
The group used actual butterfly-wing structures to collect sunlight, employing them as templates to synthesize solar-collecting materials. They chose the black wings of the Asian butterfly Papilio helenus Linnaeus, or Red Helen, and transformed them to titanium dioxide by a process known as dip-calcining. Titanium dioxide is used as a catalyst to split water molecules into hydrogen and oxygen. Fan’s group paired this butterfly-wing patterned titanium dioxide with platinum nanoparticles to increase its water-splitting power. The butterfly-wing compound catalyst produced hydrogen gas from water at more than twice the rate of the unstructured compound catalyst on its own.
This work was presented at the American Chemical Society’s 243rd annual meeting themed Chemistry of Life in San Diego, California, March 25-29, 2012.
As I’ve noted previously, although that was specific to Morpho butterflies (my Feb. 14, 2012 posting), butterflies are being very generous with their intellectual property.