With the widespread of the novel coronavirus (SARS-CoV-2), the inactivation of bacteria and viruses using ultraviolet (UV) light has been reevaluated. However, there are many applications where the safety to the human body itself and inactivation effect itself are questioned, and there is a movement to review the UV-C guidelines (Global Lighting Association, Position Statement on Germicidal UV-C Irradiation UV-C SAFETY GUIDELINES, 2020). Since the Minamata Convention on Mercurybans the production of mercury in principle, deep-ultraviolet light-emitting diodes (UVC-LEDs) are now being used in place of mercury lamps. In this paper, we will discuss effective irradiation methods for the inactivation of pathogens on solid surfaces, the inactivation of pathogens in water, and the inactivation of viruses in aerosols using UVC-LED.

Micro light emitting diode (μLED) displays have been in development since 2017, aimed for application in 2020. However, when using three-color, i.e., red, blue, and green LEDs, or blue LEDs that excite red and green phosphors, many challenges arise in mass production, cost, and quality. Our group has devised an ultraviolet (UV)-excited red, green, and blue (RGB) display that excites red, green, and blue phosphors using UV-LEDs. This paper studies how the composition and crystal defects of a light-emitting layer affect the luminous efficiency of a UV μLED chip from the perspective of internal quantum efficiency (IQE). It was confirmed that the luminous efficiency improves by making the LED chips in the near ultraviolet range μ-size. The UV μLED chip emitting at 385 nm exhibited a more linear output than a 400-nm purple μLED chip.

A viral fluid containing coronavirus OC43 was smeared onto plastic surfaces and irradiated with light at wavelengths of 222, 254, and 275 nm emitted by an excimer lamp, an ultraviolet lamp, and a deep ultraviolet LED, respectively. After irradiation at varying durations, the virus on the plastic surface was collected and the viral activity was measured to compare the viral inactivation capabilities of the three wavelengths. We found that the 275-nm light from the deep ultraviolet LED exhibited an inactivating effect greater than or equal to the 254-nm light from the UV lamp that is used as a sterilizing device in general applications. The results demonstrated the potential of deep ultraviolet LED irradiation for general viral infection control and in the ongoing fight against the novel coronavirus, SARS-CoV-2.