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Japanese UVC LED supplier Nitride Semis made experiment on covid-19 disinfection based on three wavelengths

Using three wavelengths including 222nm, 254nm, and 275nm, Japanese UVC-LED supplier Nitride Semiconductors has made an experiment recently to verify the UVC-LED disinfecting effect on covid-19 virus.

The experiment showed that the UVC LED whose wavelength of 274nm has an disinfection effect equal to or greater than that of 254nm, during the test, each UVC LED light is irradiated with the same amount of light energy under the same environment.  

As a light source for each emission wavelength, Nitride prepared an excimer lamp with a wavelength of 222 nm, a low pressure mercury lamp with a wavelength of 254 nm, and a deep UVC LED with a wavelength of 275 nm.

As each light source is different, in order to make the conditions the same, the engineers adjusted the length of time to illuminate the object according to the illuminance of each light source. 
different wavelengths of UVC-LED using in the experiment

The figure shows the change over time in the residual infectious titer of covid-19 virus adhering to the surface. The two blue bars in the Reference are equivalent to the standard values of the test conditions, and are the cut sample immediately after creation and the same sample left for 12 minutes in a safety cabinet at 22 °C 30-35 percent RH. The orange, yellow, blue, green, and grey bars of each wavelength are used in a clean room maintained at 20 °C at 8-14 percent RH, after the sample has been completely dried according to the protocol.

The figure shows the result of irradiating the light amount of orange 0 J / m2. Yellow 7.5 J / m2, blue 15 J / m2, green 30 J / m2, gray 60 J / m2 in order from the left at a distance of 50 cm from the light source. As for the change over time in the residual infection rate, the shorter the bar length compared to the 0.0 J / m2 orange bar graph, the higher the inactivating effect. Notably, the 60J / m2 grey bar graph with the largest amount of illuminated light showed the shortest at 275nm, followed by a wavelength of 254nm and finally 222nm.

The test result shows that the wavelength of 275 nm has the same or better inactivating effect for 254nm on the covid-19 virus. It shows that UVC-LED can really disinfect the covid-19 virus under the experiment environment.
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