![]() Where photons are absorbed by DNA/RNA the resulting damage can inhibit the microorganism’s ability to replicate, rendering it no longer infectious (Harm 1980). UV-B and UV-C photons can directly alter chemical bonds within these key biomolecules, affecting their structure and function. UV-C and UV-B light has a direct disinfection effect when its energy is absorbed by genetic material (limiting replication) or by other cellular or viral components such as a protein (limiting attachment and infectivity). How does UV light inactivate microorganisms? Commercial UV LEDs are formed of thin crystalline aluminum gallium nitride (AlGaN) layers deposited onto a substrate (sapphire or aluminum nitride) the ratio of aluminum to gallium in the thin layers determines the band gap and so the emission spectrum emitted by the LED. The choice of semiconducting materials used in the LED dictates the size of the barrier and therefore the wavelength of the photon emitted. Once across the barrier, these electrons can lose the energy gained in the transition and emit a photon. With an applied voltage, electrons are pushed across an energy barrier (band gap) separating differently charged layers within the LED crystal structure. Ultraviolet light emitting diodes (UV LEDs) are solid state semiconductor devices. Common plasma discharge lamps include mercury vapor lamps, metal halide lamps, xenon lamps (pulsed UV), excimer and exciplex lamps, and deuterium lamps. The spectrum, or wavelengths emitted, depends on the elements of the gas inside. As a voltage is applied to the lamp filament, electrons within the enclosed gas are excited to a higher energy state as they fall back to the ground state, they release that extra energy as a photon, which is a packet of light energy. Plasma discharge lamps contain a gas mixture enclosed inside a glass tube. Due to strong absorption of higher-energy radiation in the upper atmosphere almost no solar UV-C reaches the Earth’s surface (ASTM G-173 2020) the spectrum of solar radiation – commonly referred to by air mass (AM) values – varies across the Earth’s surface.Īrtificial UV light is produced primarily from plasma discharge lamps and light-emitting diodes (LEDs), as well as unintentional emissions from activities such as arc welding. Natural UV light comes from the sun some of which reaches the Earth’s surface, and some is absorbed by the atmosphere. Sources of UV lightĪs with other types of light on the electromagnetic spectrum, UV light is produced both naturally and artificially. The majority of microbes show a relative peak in sensitivity to radiation around 265 nm, and so the application of UV disinfection has targeted the “germicidal” range around this peak. Even higher-energy radiation in the UV-C band is most commonly used for disinfection. For this reason, UV-B radiation, at shorter wavelengths than UV-A, has higher energy and carries a greater cancer risk in humans (NTP, 2016). The energy carried by light is inversely proportional to its wavelength therefore, the shorter the wavelength, the higher the energy. 2016), also are commonly used for curing anything from inks or coatings to adhesives and nail polish (Endruweit 2006). UV-A wavelengths, which cause suntans and are used in tanning salons (Nilsen et al. Vacuum UV wavelengths are so-named because of their strong absorption, even by air. The UV range is further subdivided into four categories: UV-A (315 nm to 400 nm), UV-B (280 nm to 315 nm), UV-C (200 nm to 280 nm) and vacuum UV (100 to 200 nm). UV radiation is on the short-wavelength side of the electromagnetic spectrum, occupying the range from 100 to 400 nm. As a wave, the energy is radiated by smooth oscillations of the electromagnetic field. As a particle, massless photons carry light energy throughout the universe (at the speed of light). Light can be described as both a particle and a wave, a phenomenon known as wave-particle duality. ![]() This article gives an overview, for general audiences, of UV disinfection. ![]() UV light is commonly used for disinfecting water, air and surfaces however, the wavelengths that are most effective at inactivating microbes also are considered damaging to human skin and eyes. It inactivates microorganisms (including viruses) by degrading their genetic material and structural molecules so that they are no longer infectious. Ultraviolet (UV) light is commonly used for disinfection. Zhe Sun, Ph.D., post-doc, Research Center for Eco- Environmental Sciences, Chinese Academy of Sciences Beck, Ph.D., assistant professor, University of British Columbiaīabak Adeli, Ph.D., director of R&D, Acuva Technologies Inc. Richard Simons, Ph.D., head of application science, AquiSense Technologies Kari Sholtes, Ph.D., instructor, CMU/CU Boulder Civil Engineering, Colorado Mesa University
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