A Blacker Black: Darkest Known Material Created

January 24, 2008

Scientists have delivered a crushing blow to fans of the cult movie This is Spinal Tap—a material even blacker than the band's black album cover.

In the 1984 film, lead guitarist Nigel Tufnel looks at the album cover for the first time and opines, "It's like, how much more black could this be? And the answer is none, none, none more black."

But Pulickel Ajayan, a professor of engineering at Rice University in Houston, Texas, and colleagues at Rensselaer Polytechnic Institute in Troy, New York, have created a blacker black.

Theirs is an array of tiny carbon cylinders standing on end like bristles on a brush that reflects only 0.045 percent of the visible light shined on it.

"It definitely makes a very dark material," Ajayan said. "In fact, better than what is reported as the darkest material in the Guinness Book of World Records."

The team reported the findings this month in the journal Nano Letters and applied to Guinness for record-holder status.

The current record holder is a nickel-phosphorus alloy created by scientists in 2003 at the National Physical Laboratory in London. It reflects 0.35 percent of visible light.

An actual black album cover reflects about 5 percent of the light.

From Solar Power to Art

Pure academic curiosity drove Ajayan and his colleagues to create their superdark material, which may now find wide-ranging practical applications.

Theory suggests this type of array of carbon nanotubes—one-atom-thick carbon sheets rolled into cylinders—may just be the perfect absorber, Ajayan said. Carbon is one of nature's darkest materials.

His team arranged the carbon nanotubes on end, because the spaces between the tubes—the gaps—allow for efficient trapping of light.

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