The principles behind UV and visible light sanitization are different. Both of these approaches have similar reach and are aimed at sanitization of surfaces. In both cases a specific quantity of light (see below) must hit the microorganisms to damage them. UV light changes their DNA, while the visible light causes oxidative stress until the germs become inactive.

Various sub bands of the UV band have side-effects. Any high intensity light sources will eventually cause damage to human skin or eyes. UV light sources with high energy below 240nm also result in ionization of air and production of ozone molecules. Ozone, despite being advertised as a sanitizing agent itself, is harmful to humans in increased concentration.

UV-C (100–280 nm) has its germicidal peak around 265nm. Common frequencies commercially used are 270nm, 254nm and recently 222nm.

Light sanitization efficiency

Sanitization by light is based on irradiation of pathogens by high amounts of energy at specific wavelengths. Sanitization is obtained when a specific dose of energy is delivered at the target. The amount of lethal (deactivating) energy depends on pathogens and wavelength of radiation. The energy required to sanitize an object accumulates over exposure time.

Required irradiation time also depends on:

• distance between light source and object targeted;

• power of light source

Doubling the distance of the target results in four times less of the energy delivered, the efficiency decreases with the square of sanitization target distance. Exposure time required for sanitization is inversely proportional to the power of light source, so by doubling the energy emitted (two light sources instead of one, see image below) we can halve the time required for sanitization.

In terms of energy required, UV-C lights are commonly more effective against viruses than against bacteria or fungi. When UV-C lights are compared with PurpleBlue™ the effectiveness varies with the virus considered, PurpleBlue™ is more effective than UVc for the deactivation of COVID-19, and influenza A. PurpleBlue™ is also more effective than UVc against bacteria, mold and fungi. 

Precise evaluation and sanitization principles

Performance reported in this document is for reference only. Precise custom evaluation of sanitization time considering target pathogens, room layout, wall materials and light conditions is available as a service.

Customized solutions can be provided upon evaluation of needs and environment specifications

Different pathogens require different amounts of energy to be deactivated. At Itsuki we provide customized solutions based on your needs (what you want to achieve and within what time). Above are two examples of our simulations made evaluating time to sanitize surfaces inside an office in Tokyo. Evaluation on the left employed 28m of L36 LED strip, while there are 14m in the result on the right.

STOP COVID-19 and other threats

Our light is able to deactivate 99.9% of germs:

Bacteria, Mold, Fungi, COVID-19 and other viruses

PurpleBlue™ is a CERTIFIED TECHNOLOGY

Virostatics, an Italy-based Pharmaceutical company, has conducted studies on our technology evaluating the virucidal effects of our products against the original Wuhan version of SARS-CoV-2. Virostatics observed a virucidal effect of our lamp, concluding that PurpleBlueTM lamp was effective in reducing SARS-CoV-2 in two independent experiments. The deactivation effect observed, and the virucidal efficiency of our technology, can be extended to any variant of the SARS-CoV-2 virus, and to other viruses. Request here the scientific report

EFFECTIVENESS AGAINST MICROBES

"Violet–blue light, particularly 405 nm light, has significant antimicrobial properties against a wide range of bacterial and fungal pathogens and, although germicidal efficacy is lower than UV light, this limitation is offset by its facility for safe, continuous use in occupied environments."

Maclean et.al., Journal of Hospital Infection (2014), 88/1, pages 1-11

The germicidal effect of our PurpleBlue™ LED is given from its special spectrum that present a crucial peak at 405nm.

EFFECTIVENESS AGAINST SARS-CoV-2

In the middle of March 2021 a team of doctors of the Ichan medical research institute of New York and the García-Sastre Laboratory reported that irradiating a culture of SARS-COV-2 for 8 hours with a 405nm light source emitting 0.6 m Wcm-2 brought a population reduction of 99.74%.

" [..] Given the ongoing COVID-19 pandemic, we wanted to explore the impact of 405 nm enriched visible light technology on inactivation of respiratory pathogens such as SARS-CoV-2 [..] a high irradiation dose of 0.6 mWcm−2 was used to assess the inactivation potential within a much shorter time frame. Irradiation for one hour resulted in a reduction of 71.52% which reached 91.15% after four hours and 99.74% (385 times) after 8 hours in comparison to the initial input (TO)."

Yahnke, et al. "Lighting a better future: the virucidal effects of 405 nm visible light on SARS-CoV-2 and influenza A virus." bioRxiv (2021).

Our experiments

In our laboratory we ran several experiments on mold and food deterioration. We have always tried to control all the factors, changing just the light condition: 

• Test: PurpleBlue light; 

• Control: Sunlight.

For mold we used petri dishes filled with nutrients that promote the growth of microorganisms (molds) and left them in an indoor room.

For food deterioration we just placed inside two adjacent petri dishes three blackberries. A divider was standing between the two petri dishes blocking the PurpleBlue light to avoid that both dishes were exposed to the sanitizing effects of our lights.

Below a video created with images taken during the experiment. We show one picture per day for a total of eight days.

High Power Visible Light - References

• M. Maclean, S.J. MacGregor, J.G. Anderson, G. Woolsey. Inactivation of bacterial pathogens following exposure to light from a 405-nanometer light-emitting diode array. Appl. Environ. Microbiol, 75(7):1932-7. 2009.

• L.E. Murdoch, M. Maclean, E. Endarko, S.J. MacGregor, J.G. Anderson. Bactericidal effects of 405 nm light exposure demonstrated by inactivation of Escherichia, Salmonella, Shigella, Listeria, and Mycobacterium species in liquid suspensions and on exposed surfaces. The Scientific World Journal. 2012; 2012.

• M. Maclean, An investigation into the light inactivation of medically important microorganisms, Ph.D. thesis, University of Strathclyde, Glasgow, UK, 2006.

• L. E. Murdoch, M. MacLean, S. J. MacGregor, and J. G. Anderson, Inactivation of Campylobacter jejuni by exposure to high-intensity visible light, Foodborne Pathogens and Disease, vol. 7, no. 10, pp. 1211–1216, 2010.

• C.J. Yahnke, R.J. Rathnasinghe, A. Garcia-Sastre, Lighting a better future: the virucidal effects of 405 nm visible light on SARS-CoV-2 and influenza A virus. bioRxiv, 2021.

Germicidal UV Light - References

• S.E. Beck, H. Ryu, L.A. Boczek, J.L. Cashdollar, K.M. Jeanis, J.S. Rosenblum, O.R. Lawal, K.G. Linden. Evaluating UV-C LED disinfection performance and investigating potential dual-wavelength synergy. Water research. 109:207-16. 2017.

• G.Y. Lui, D. Roser, R. Corkish, N.J. Ashbolt, R. Stuetz. Point-of-use water disinfection using ultraviolet and visible light-emitting diodes. Science of the Total Environment. 553:626-35. 2016.

• K. Oguma, S. Rattanakul, J.R. Bolton. Application of UV Light–Emitting Diodes to adenovirus in water. Journal of Environmental Engineering.142(3):04015082. 2016.

In all other cases, electric power is turned into light by heating up various materials. The efficiency of this conversion to light improved more than 1000x since the first candles (before 200BCE). Efficiency got a big boost with the inventions of light bulbs with electrically heated filaments and later with fluorescent lamps. The LED technology surpassed fluorescent lights in efficiency decades ago, and is the best at the moment.

LEDs not only produce less heat, the light they produce is all directed so it can be guided to where it's needed. Fluorescent tubes may require shades or reflectors do deliver the light emitted into desired directions. Fluorescent lights age quickly. LEDs last longer and perform constantly for very long time, they output decays minimally towards the end of their life when compared to any other light source technology.

LEDs use less toxic (mercury) or difficult-to-recycle materials in production and for their function. Fluorescent light produce some UV, which cause material ageing and, discoloration of plastic and paints.

Save up to 75% on your electricity bill

Considering brightness and energy consumption of our LED solutions it is easy to evaluate the great advantage in choosing our products:

The brightness of 1m of L36 (36W) is comparable to a single 150W incandescent bulb or 1.5 (1.8m) of fluorescent tubes (considering tubes of 40W and 1.2m in length)

In terms of consumption L36 use 4 times less energy than incandescent bulbs and less than half of the energy used by fluorescent lamps for an equivalent light output.

Finally, the lifespan of L36 is 40,000h without any performance decrease, while the lifespan of fluorescent tube is on average 10,000h. This means you will replace 4 fluorescent tubes before a single replacement of a L36 or any other of our LED products.

In order to get the same brightness provided by 1m of L36 for the same number of hours, we need 1.5 fluorescent tubes, and those tubes need to be replaced 4 times. After 40,000 hours of use we should consider that 1m of L36 is more convenient than plugging 6 fluorescent tubes.

Below is an example of savings evaluated for 40000h (or 16 years of use for 8h a day 6 days a week) considering an average residential consumption in Japan, US and Italy, respectively equal to 26.88JPY, 14.19USD cents, and 0,19248€ per kWh. The resulting savings exceed the cost of 1m of L36.

Plant growth support

Photosynthetic efficiency

Without enough light, a plant cannot photosynthesize very quickly - even if there is plenty of water and carbon dioxide and suitable temperature. Moderately increasing the light intensity of selected light frequencies increases the rate of photosynthesis.

Plant growth

Plants illuminated with 660 nm light source feel like illuminated by natural sunlight. Blue and red parts of visible spectrum are the most important parts of the spectrum for natural growth of plants. Effects of bands of spectra vary depending on absorption of light by various plant compounds and processes. Chlorophyll A and B are are responsible for photosynthesis, Chlorophyll absorbs the light required to convert carbon dioxide and water into energy. The germination, building and growth of the plant is supported by Phytochromes Pr and Pfr.

Plant growth - References

• Xu, Yingchao, Yongxiao Chang, Guanyu Chen, and Hongyi Lin. "The research on LED supplementary lighting system for plants." Optik 127, no. 18 (2016): 7193-7201.

• Merchant N., "This illuminated field isn't just pretty - it's helping to grow crops", World Economic Forum website, downloaded March 2021

• Jwo-Huei, J., Ching-Chiao, L., Tsung-Han, L., Chieh-Ju, L., Shiang-Hau, P., Fu-Chin, Y., & ... Ban-Dar, H. Plant Growth Absorption Spectrum Mimicking Light Sources. Materials, 2015,8(8), 5265-5275.

• Trouwborst, G., Hogewoning, S. W., van Kooten, O., Harbinson, J., & van Ieperen, W. Plasticity of photosynthesis after the red light syndrome in cucumber. Environmental & Experimental Botany, 2016, 12175-82.

• Deram P, Lefsrud M, Orsat V. Supplemental Lighting Orientation and Red-to-blue Ratio of Light-emitting Diodes for Greenhouse Tomato Production. Hortscience [serial online]. April 2014;49(4):448-452.