UV-C LEDs for Disinfection (280nm)
UV LEDs for Disinfection
Delivering high output and reliability
to enable mercury‑lamp replacement
Why did Nichia focus on 280nm?
Low-pressure mercury lamps have long been used for disinfection applications. Due to the dominant wavelength of mercury lamps, the concept that "shorter wavelengths within the UV region are more effective for disinfection" has become widely accepted, even as the transition to UV LEDs continues.
While the adoption of UV LEDs has expanded the available wavelength options, studies on UV LED-based disinfection have faced challenges due to variations in evaluation conditions among different research efforts. As a result, it has been difficult to make appropriate comparisons of disinfection effectiveness across wavelengths.
Acknowledging this background, Nichia, in collaboration with Tokushima University, developed a standardized evaluation device with strictly controlled irradiation conditions and verified the disinfection effectiveness at different wavelengths. The results revealed that effectiveness is not determined solely by shorter wavelengths; rather, at present, UV LEDs with a peak wavelength of 280nm offer an optimal balance between disinfection performance and practical applicability.
This page presents key considerations and measured data for evaluating disinfection using UV LEDs based on these research findings. Nichia expects that this information will contribute to the development and commercialization of disinfection technologies across a wide range of applications.
What is required for disinfection using ultraviolet (UV) LEDs
There are several points to consider when discussing disinfection with UV LEDs, including the viricidal power by wavelength, the UV LED characteristics, and the lifetime or Virucidal Maintenance.
By correctly understanding and evaluating each, the maximum viricidal power can obtained for the application.
Below explains these three key points.
Video 1. What is required for disinfection using ultraviolet (UV) LEDs
(1) Refer to appropriate UV sensitivity data
Although it is necessary to know the required fluence (UV dose) for the target microorganisms, UV irradiation conditions currently differ between studies, making it impossible to perform evaluations under consistent conditions. Nichia's newly developed UV LED irradiation device standardizes irradiation parameters and enables highly accurate evaluation of UV sensitivity. (For more information on the irradiation device, refer to the press release.)
Figure 1. Nichia Developed a UV Irradiation Device to Evaluate UV Sensitivity
In a joint research course with the University of Tokushima ("Microbial Control Research" by Professor Akira Takahashi), this irradiation system was used to evaluate the UV sensitivity of each microorganism at each wavelength. The overall results show that the peaks were closer to the longer wavelength than the commonly used bactericidal effect curve JIS Z8811-1968. In addition, UV sensitivity differs from microorganism to microorganism, confirming the importance of referencing data according to the target of disinfection.
Experiment Data
Figure 2. Results of UV sensitivity evaluation for each microorganism at each wavelength (In the joint research course with the University of Tokushima)
(2) Use the Virucidal Power as a key indicator, taking the UV LED output into consideration.
The inactivation effect is determined not only by the virucidal efficiency of each wavelength, but through multiplying the wavelength virucidal efficiency by the output of the LED. This factor is called "Virucidal Power" is one of the most important indicators of the inactivation effect.
Figure 3. Virucidal Power
(3) Consider UV LED lifetime (Output1 Maintenance Rate) for Virucidal Maintenance
The output of LEDs simply just decreases with time of use. In particular, for UV-C LEDs, shorter wavelength LEDs degrade faster than longer wavelength LEDs. Therefore, the lifetime of LEDs differs by wavelength. Through testing, Nichia continues to prove that 280nm is the ideal wavelength when considering the Virucidal Maintenance. Below shows a list of products.
Video 2: Virucidal power decreases over time
2 LED out put by wavelength: This graph is based on in-house research and modeled based on the output power (radiant flux) of ordinary LEDs available on the market as of July 2023.
Verification of Disinfection Effectiveness Based on Experimental Data
This study has clarified the cumulative UV dose required for the inactivation of fungi, bacteria, and various viruses using 280nm LEDs, as outlined below.
| Microbial Category | Common Name | Scientific Name | UV Dose (mJ/cm2) at Each Inactivation Rate |
||
|---|---|---|---|---|---|
| 90% | 99% | 99.9% | |||
| Fungi3 | Yeast | Rhodotorula mucilaginosa NBRC114835 |
63 | 84 | 100 |
| Mold | Cladosporium Halotolerans NBRC113481 (Mature Spores) |
820 | 1450 | 2250 | |
| Cladosporium sphaerospermum NBRC6348 (Mature Spores) |
57 | 88 | 149 | ||
| Penicillium roqueforti NBRC5459 |
37 | 61 | 105 | ||
| Aspergillus brasiliensis NBRC9455 |
98 | 180 | 400 | ||
| Botrytis cinerea Persoon ATCC46522 |
104 | 128 | 187 | ||
| Bacteria4 | Bacteria | Escherichia coli ATCC25922 |
4.5 | 6.4 | 7.7 |
| Staphylococcus aureus ATCC29213 |
4.2 | 5.4 | 6.6 | ||
| Vibrio parahaemolyticus RIMD2210633 |
1.2 | 2.5 | 3.8 | ||
| Enterococcus faecalis ATCC7080 |
7.5 | 10 | 11.4 | ||
| Pseudomonas aeruginosa PAO-1 strain |
1.8 | 3 | 4.4 | ||
| Salmonella enterica Enteritidis 171 strain |
3 | 4.8 | 6.5 | ||
| Legionella pneumophila ATCC33152 |
3 | 4.5 | 6.2 | ||
| Campylobacter jejuni NCTC11168 |
2.1 | 3.7 | 5.2 | ||
| Lactobacillus plantarum ATCC8014 |
5.7 | 8.1 | 10.1 | ||
| Bacillus subtilis IFO3134 (trophozoite) |
4.5 | 6.7 | 8.3 | ||
| Bacillus subtilis IFO3134 (spore) |
36 | 48 | 61 | ||
| Viruses5 | Virus | Influenza A virus H1N1 subtype PR8 strain |
2 | 5 | 9.4 |
| Herpes simplex virus KOS strain |
5 | 12 | 19 | ||
| Human coronavirus OC43 strain |
2.7 | 5.2 | 7.7 | ||
| Human coronavirus 229E strain |
3 | 5 | 9.7 | ||
| Feline calicivirus F9 strain |
8.8 | 20.6 | 30 | ||
| Human adenovirus 5 strain |
30 | 56 | |||
| Human respiratory syncytial virus strain Long |
1.6 | 2.6 | 3.9 | ||
| Human respiratory syncytial virus strain 18537 |
1.7 | 3.1 | 4.6 | ||
| Influenza A virus H5N1 subtype |
3.5 | 7.7 | 12.6 | ||
| Human metapneumovirus strain TN/83-1211 |
3.8 | 5.4 | 7.1 | ||
| Severe acute respiratory syndrome coronavirus 2 | 2.5 | 5.4 | 7.6 | ||
| Escherichia coli phage MS2 NBRC102619 |
23.9 | 48.2 | |||
4 The full paper on bacteria is available here.
5 The full paper on viruses is available. (Paper 1, Paper 2)
What is disinfection using ultraviolet?
Bacteria multiply by cell division, whereas viruses are known to invade the cells of organisms and multiply by taking advantage of the host's functions. In both cases, growth is based on information in the DNA and RNA of the bacteria and viruses. UV irradiation has the effect of deforming the DNA and RNA structure of the bacteria and virus.
The mechanism is that abnormalities in the structure of DNA and RNA interfere with their ability to metabolize and multiply, thus enabling the inactivation of bacteria and viruses.
Video 3. Mechanism of inactivation by ultraviolet
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