News: LEDs
17 December 2021
Nitride Semiconductor verifies inactivating effect of UVC-LEDs on coronavirus
Nitride Semiconductor Co Ltd of Tokushima, Japan (which was spun off from Tokushima University in 2000 and claims to have developed the first highly efficient ultraviolet light-emitting diode) says that, in collaboration with the National Hospital Organization Sendai Medical Center Clinical Research Department Virus Center, it has verified the inactivating effect on OC43 coronavirus (pseudo SARS-CoV-2) using three different wavelengths in the deep ultraviolet region (222nm, 254nm and 275nm).
The team confirmed that the UVC deep ultraviolet wavelength of 275nm has an inactivating effect equal to or greater than that of the sterilization light source 254nm in a comparative test in which each deep ultraviolet wavelength is irradiated with the same amount of light energy under the same environment.
The rapid spread of the SARS-CoV-2 Omicron variant in South Africa has revealed that the vaccine's effectiveness is limited. Mercury-containing UV lamps have been used as germicidal lamps since 1901 when German physicist Hermann Strebel discovered that UV lamps could inactivate bacteria and viruses. Since inactivation by UV lamp does not use chemicals, it has been used in the medical field as a safe and reliable inactivation method without residual substances.
In recent years, through the development of semiconductor technology, similar effects have been confirmed with deep ultraviolet light-emitting diodes (UVC-LEDs) with a wavelength of 300nm or less. The latest research was conducted for the purpose of comparing and verifying two types of ultraviolet light with wavelengths of 222nm and 275nm (which have recently begun to be applied in the deep ultraviolet region) with the conventional sterilization light source of 254nm.
Experiment contents
As a light source for each emission wavelength, the team prepared an excimer lamp with a wavelength of 222nm, a UV (low-pressure mercury) lamp with a wavelength of 254nm, and a deep ultraviolet LED with a wavelength of 275nm.
Since the illuminance of each light source is different, in order to make the conditions the same the team adjusted the length of time to irradiate the object according to the illuminance of each light source so that the amount of irradiation light energy (integrated light amount) was equal.
Results
The figure shows the change over time in the residual infectious titer of OC43 coronavirus (the concentration of viral particles that can transduce cells) adhering to the surface. The two blue bars in the Reference correspond to the standard values of the test conditions, and are the smear sample immediately after creation and the same sample left for 12 minutes in a safety cabinet at 22°C 30-35% RH. The orange, yellow, blue, green and gray bars of each wavelength are used in a bio-cleanroom maintained at 20°C at 8-14% RH, after the smear sample has been completely dried according to the protocol.
The figure shows the result of irradiating orange 0J/m2, yellow 7.5J/m2, blue 15J/m2, green 30J/m2, gray 60J/m2 light in order from the left at a distance of 50cm from the light source. Regarding the change over time in the residual infection rate, the shorter the bar length compared with the 0.0J/m2 orange bar graph, the higher the inactivating effect. Notably, the 60J/m2 gray bar with the largest amount of illuminated light showed the shortest at 275nm, followed by a wavelength of 254nm and finally 222nm.
Significance
Compared with 254nm, which has been conventionally applied as a sterilization line wavelength, the result was that 275nm has the same or better inactivating effect on the pseudo SARS-CoV-2. This is in line with the flow of total abolition of mercury stipulated in the United Nations Environmental Plan (UNEP) ‘Minamata Convention on Mercury’. It shows that UVC-LED light can fully fulfill its role of abandoning mercury.
UV LEDs and coronavirus: how effective are the latest sanitizer systems?
