LED lighting isn’t just for illuminating rooms and roads. Someday it could be used to sterilize surgical tools or purify water.
At the right wavelength, ultraviolet light kills microorganisms on surfaces and in water. But the effort to develop new UV disinfection devices that utilize LEDs has been hampered by the semiconductors used to make LEDs. The substrate absorbs the wavelengths that are effective for sterilization. Researchers in North Carolina, in partnership with scientists in Japan, have found a way to overcome the problem. Their findings are now published online in Applied Physics Letters.
Most semiconductor chips are made on silicon. LEDs use aluminum nitride as a semiconductor. North Carolina State University said that the material can handle a lot of power and create light in a wide spectrum of colors, particularly in the UV range. LEDs that are based on aluminum nitride can generate UV light in the range of 200 nm to 280 nm. UV light at 265 nm is effective for sterilization purposes. The problem with this substrate is that it also absorbs wavelengths of UV light important for sterilization.
In a computer simulation researchers found that trace carbon atoms were responsible for absorbing most of the UV light important for sterilization applications. Eliminating the carbon in the substrate solved the problem.
The UV sterilization technologies could find their way into new commercialized products developed by HexaTech, a Raleigh, North Carolina company spun off from N.C. State. HexaTech, which last year raised $3.1 million in venture capital financing, is doing R&D work on semiconductor products that use aluminum nitride. The company lists water sterilization and alternative energy technologies among its product targets.
HexaTech scientists participated in the research with N.C. State and are listed as co-authors on the the paper published in Applied Physics Letters. Also contributing were researchers from Tokyo University of Agriculture and Technology and the Tokuyama Corporation. The research was supported by funding from the U.S. Department of Defense.
“UV treatment utilizing LEDs would be more cost effective, energy efficient and longer lasting,” Ramón Collazo, an assistant professor of materials science and engineering at N.C. State and lead author of the paper said in a statement. “Our work would also allow for the development of robust and portable water-treatment technologies for use in developing countries.”