It is well-known now that many viruses, including the emergent coronavirus that has led to the Covid-19 pandemic are destroyed by exposure to sunlight. However, in many environments chemical disinfectants must be used to ensure hygiene and reduce the serious risk of transmission of this potentially lethal respiratory virus. Now, a US team is building ultraviolet LEDs that could be used in a handheld device to destroy the virus quickly and efficiently in the healthcare environment, care homes, shops and restaurants and elsewhere. Such a development, which obviously hinges on developments in materials science, could help in our efforts to take control of this and future pathogens.

The team from the University of California Santa Barbara and their colleagues discuss details of their work on UV LEDs that can decontaminate surfaces, and perhaps even the air around us and liquids, including water, and kill the SARS-CoV-2 virus.

"One major application is in medical situations - the disinfection of personal protective equipment, surfaces, floors," explains Christian Zollner. An effective UV disinfection system active against the new virus could allow so-called PPE, personal protective equipment, to be made safe where there is pressure for it to be reused because of supply limitations, for instance. The team has demonstrated that UV disinfection can sterilize to the 99.9% level within 30 seconds and has been shown to work in sterilizing the interior of unoccupied vehicles. This would have the obvious application of reducing the risk of infection for paramedics and ambulance drivers after transporting an infected patient.

"UV-C light in the 260 - 285 nm range most relevant for current disinfection technologies is also harmful to human skin, so for now it is mostly used in applications where no one is present at the time of disinfection," Zollner explains. It cannot be used to sanitize hands or other areas of the skin safely as it causes burns and can damage the eyes.

UV-C is commonly generated using mercury vapor lamps and much work needs to be done to bring UV LED technology to the same efficiency, cost, reliability, and lifetime. However, the team's work on fabricating high-quality deep-ultraviolet (UV-C) LEDs using film deposition of the semiconductor alloy aluminum gallium nitride (AlGaN) on to silicon carbide (SiC) avoids the use of sapphire substrate and could pave the way to a commercially viable UV-C LED. Silicon carbide suits deposition of the semiconductor better than sapphire. [Burhan K., et al. ACS Photonics, 2020; 7 (3): 554 DOI: 10.1021/acsphotonics.9b00600]