The darkest material ever measured has been created by researchers in the US, making it 4 times darker than the previous recorded record.
All materials reflect some amount of light and scientists have long envisioned an ideal black material that absorbs all the colors of light while reflecting no light. So far they have been unsuccessful in engineering a material with a total reflectance of zero.
The material developed by a team from Rensselaer Polytechnic Institute and Rice University looks like a thin sheet of black paper made of billions of tiny hollow tubes of pure carbon that are vertically aligned like packaged spaghetti. The material's darkness lies in the loose packing of the tubes. Because the tips of each nanotube measure just one-billionth of meter across, most light striking the surface is absorbed. As a result, the material reflects only 0.045 percent of the light that strikes it.
The total reflectance of conventional black paint, for example, is between 5 and 10 percent. The darkest manmade material, prior to the discovery by the researchers, boasted a total reflectance of 0.16 percent to 0.18 percent.
The team tested the array over a broad range of visible wavelengths of light, and showed that the nanotube array's total reflectance remained constant.
"It is a fascinating technology, and this discovery will allow us to increase the absorption efficiency of light as well as the overall radiation-to-electricity efficiency of solar energy conservation," said Shawn-Yu Lin, professor of physics at Rensselaer and a member of the university's Future Chips Constellation, who led the research project. "The key to this discovery was finding how to create a long, extremely porous vertically-aligned carbon nanotube array with certain surface randomness, therefore minimizing reflection and maximizing absorption simultaneously."
The discovery could lead to applications in areas such as solar energy conversion, thermalphotovoltaic electricity generation, infrared detection, and astronomical observation.
The research results were published in the journal Nano Letters.
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Reference: Rensselaer Polytechnic Institute and Rice University
Source of top image: Rensselaer Polytechnic Institute