RPI professor of physics Shawn-Yu Lin and researchers from Rice University in Texas, including former RPI professor Pulickel Ajayan, have created the darkest material ever made by man.
The research results were recently published in the journal Nano Letters, and have garnered international attention. The researchers who developed the material have applied for a Guinness World Record.
Other researchers contributing to this project and listed authors of the paper include Rensselaer physics graduate student Zu-Po Yang, Rice postdoctoral research associate Lijie Ci, and Rensselaer senior research scientist James Bur.
The project was funded by the U.S. Department of Energy’s Office of Basic Energy Sciences and the Focus Center New York for Interconnect, and was part of Lin’s research for the Future Chips Constellation at RPI, which focuses on innovations in materials and devices, solid state and smart lighting, and applications such as sensing, communications, and biotechnology.
The material, a thin coating comprised of low-density arrays of loosely vertically-aligned carbon nanotubes, absorbs more than 99.9 percent of light and could possibly be used in the future to boost the effectiveness and efficiency of solar energy conversion, infrared sensors, and other devices.
The darkest manmade material prior to the discovery by Lin’s group used a film deposition of nickel-phosphorous alloy and boasted a total reflectance of 0.16 - 0.18 percent. Lin’s group created a material with a total reflective index of 0.045 percent—more than three times darker than the previous record.
“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,” Lin said in an RPI press release. “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 loosely-packed carbon nanotubes—full of extremely small gaps and holes to collect and trap light—give this material its unique ability to reflect light weakly and absorb light strongly.
“It’s also interesting to note that the reflectance of our nanotube array is two orders of magnitude lower than that of the glassy carbon, which is remarkable because both samples are made up of the same element—carbon,” said Lin.
The research team tested the array over a broad range of visible wavelengths of light, and demonstrated that the nanotube array’s total reflectance remains constant.
This discovery could lead to applications in areas such as solar energy conversion, thermalphotovoltaic electricity generation, infrared detection, and astrological observation.
