Editing Ultraviolet (section)

==Applications==
Because of its ability to cause chemical reactions and excite [[fluorescence]] in materials, ultraviolet radiation has a number of applications. The following table<ref>{{cite web |title=Classification of UV |website=SETi |url=http://www.s-et.com/en/technology/uvled/ |access-date=2019-12-01 |archive-date=1 December 2019 |archive-url=https://web.archive.org/web/20191201143257/http://www.s-et.com/en/technology/uvled/ |url-status=live }}<br />{{cite web|url=http://www.s-et.com/applications/wavelength.html|title=Applications|website=SETi|access-date=2009-09-26|url-status=usurped|archive-url=https://web.archive.org/web/20080820022822/http://www.s-et.com/applications/wavelength.html|archive-date=20 August 2008}}</ref> gives some uses of specific wavelength bands in the UV spectrum.
* ''13.5&nbsp;nm'': [[Extreme ultraviolet lithography]]
* ''30–200&nbsp;nm'': [[Photoionization]], [[ultraviolet photoelectron spectroscopy]], standard [[integrated circuit]] manufacture by [[photolithography]]
* ''230–365&nbsp;nm'': UV-ID, label tracking, [[barcode]]s
* ''230–400&nbsp;nm'': Optical [[sensor]]s, various instrumentation
* ''240–280&nbsp;nm'': [[Disinfection]], decontamination of surfaces and water ([[DNA]] absorption has a peak at 260&nbsp;nm), [[germicidal lamp]]s<ref name="Liverpool, UVGI" />
* ''200–400&nbsp;nm'': [[Forensic analysis]], drug detection
* ''270–360&nbsp;nm'': [[Protein]] analysis, [[DNA sequencing]], [[drug discovery]]
* ''280–400&nbsp;nm'': [[Medical imaging]] of [[cell (biology)|cells]]
* ''300–320&nbsp;nm'': [[Light therapy]] in medicine
* ''300–365&nbsp;nm'': [[curing (chemistry)|Curing]] of [[polymer]]s and [[printer ink]]s
* ''350–370&nbsp;nm'': [[Bug zapper]]s (flies are most attracted to light at 365&nbsp;nm)<ref>{{cite web |url=http://www.pestproducts.com/uv_light.htm |title=Ultraviolet Light, UV Rays, What is Ultraviolet, UV Light Bulbs, Fly Trap |publisher=Pestproducts.com |access-date=2011-11-08 |url-status=live |archive-url=https://web.archive.org/web/20111008084125/http://www.pestproducts.com/uv_light.htm |archive-date=8 October 2011 }}</ref>

===Photography===
{{main|Ultraviolet photography}}
[[File:UV Portrait.jpg|thumb|upright|A portrait taken using only UV light between the wavelengths of 335 and 365 nanometers]]
Photographic film responds to ultraviolet radiation but the glass lenses of cameras usually block radiation shorter than 350&nbsp;nm. Slightly yellow UV-blocking filters are often used for outdoor photography to prevent unwanted bluing and overexposure by UV rays. For photography in the near UV, special filters may be used. Photography with wavelengths shorter than 350&nbsp;nm requires special quartz lenses which do not absorb the radiation.
[[Image sensor|Digital cameras sensors]] may have internal filters that block UV to improve color rendition accuracy. Sometimes these internal filters can be removed, or they may be absent, and an external visible-light filter prepares the camera for near-UV photography. A few cameras are designed for use in the UV.{{cn|date=May 2024}}

Photography by reflected ultraviolet radiation is useful for medical, scientific, and forensic investigations, in applications as widespread as detecting bruising of skin, alterations of documents, or restoration work on paintings. Photography of the fluorescence produced by ultraviolet illumination uses visible wavelengths of light.{{cn|date=May 2024}}

[[File:Jupiter.Aurora.HST.UV.jpg|thumb|right|Aurora at [[Jupiter]]'s north pole as seen in ultraviolet light by the [[Hubble Space Telescope]]]]
In [[ultraviolet astronomy]], measurements are used to discern the chemical composition of the interstellar medium, and the temperature and composition of stars. Because the ozone layer blocks many UV frequencies from reaching telescopes on the surface of the Earth, most UV observations are made from space.<ref>{{Cite web |title=Observing Ultraviolet Light |url=https://hubblesite.org/contents/articles/observing-ultraviolet-light#:~:text=How%20Do%20We%20Capture%20Ultraviolet%20Light? |access-date=2024-12-14 |website=HubbleSite |language=en}}</ref>

===Electrical and electronics industry===
[[Corona discharge]] on electrical apparatus can be detected by its ultraviolet emissions. Corona causes degradation of electrical insulation and emission of [[ozone]] and [[nitrogen oxide]].<ref>
{{cite magazine
 | title = The daytime UV inspection magazine
 | magazine = Corona
 | url = http://www.seeing-corona.com/
 | url-status=live
 | archive-url = https://web.archive.org/web/20040801222232/http://seeing-corona.com/
 | archive-date = 1 August 2004
}}
</ref>

[[EPROM]]s (Erasable Programmable Read-Only Memory) are erased by exposure to UV radiation. These modules have a transparent ([[quartz]]) window on the top of the chip that allows the UV radiation in.

===Fluorescent dye uses===
Colorless [[fluorescent dyes]] that emit blue light under UV are added as [[optical brightener]]s to paper and fabrics. The blue light emitted by these agents counteracts yellow tints that may be present and causes the colors and whites to appear whiter or more brightly colored.

UV fluorescent dyes that glow in the primary colors are used in paints, papers, and textiles either to enhance color under daylight illumination or to provide special effects when lit with UV lamps. [[Blacklight paint]]s that contain dyes that glow under UV are used in a number of art and aesthetic applications.{{cn|date=May 2024}}

Amusement parks often use UV lighting to fluoresce ride artwork and backdrops. This often has the side effect of causing rider's white clothing to glow light-purple.{{cn|date=May 2024}}

[[File:RBC Visa UV.jpg|right|thumb|A bird appears on many Visa credit cards when they are held under a UV light source.]]
To help prevent [[counterfeiting]] of currency, or forgery of important documents such as driver's licenses and [[passports]], the paper may include a UV [[watermark]] or fluorescent multicolor fibers that are visible under ultraviolet light. Postage stamps are [[Phosphor banded stamp|tagged]] with a phosphor that glows under UV rays to permit automatic detection of the stamp and facing of the letter.

UV fluorescent [[dye]]s are used in many applications (for example, [[biochemistry]] and [[forensics]]). Some brands of [[pepper spray]] will leave an invisible chemical (UV dye) that is not easily washed off on a pepper-sprayed attacker, which would help police identify the attacker later.

In some types of [[nondestructive testing]] UV stimulates fluorescent dyes to highlight defects in a broad range of materials. These dyes may be carried into surface-breaking defects by capillary action ([[liquid penetrant|liquid penetrant inspection]]) or they may be bound to ferrite particles caught in magnetic leakage fields in ferrous materials ([[magnetic particle inspection]]).

===Analytic uses===

====Forensics====
UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids such as semen, blood, and saliva.<ref>
{{cite journal
 |last1=Springer |first1=E.       |last2=Almog     |first2=J.
 |last3=Frank    |first3=A.       |last4=Ziv       |first4=Z.
 |last5=Bergman  |first5=P.       |last6=Gui Quang |first6=W.
 |year=1994
 |title=Detection of dry bodily fluids by inherent short wavelength UV luminescence: Preliminary results
 |journal=Forensic Sci. Int.
 |volume=66 |issue=2 |pages=89–94
 |doi=10.1016/0379-0738(94)90332-8 |pmid=8063277
}}
</ref> For example, ejaculated fluids or saliva can be detected by high-power UV sources, irrespective of the structure or colour of the surface the fluid is deposited upon.<ref>
{{cite web
 |author1=Fiedler, Anja
 |author2=Benecke, Mark
 |display-authors=etal
 |title=Detection of semen (human and boar) and saliva on fabrics by a very high-powered UV- / VIS-light source
 |website=Bentham Science
 |url=http://www.benthamscience.com/open/toforsj/articles/V001/12TOFORSJ.pdf
 |access-date=2009-12-10 |url-status=dead
 |archive-url=https://web.archive.org/web/20121130113644/http://www.benthamscience.com/open/toforsj/articles/V001/12TOFORSJ.pdf
 |archive-date=30 November 2012
}}
</ref> [[UV/VIS spectroscopy|UV–vis microspectroscopy]] is also used to analyze trace evidence, such as textile fibers and paint chips, as well as questioned documents.

Other applications include the authentication of various collectibles and art, and detecting counterfeit currency. Even materials not specially marked with UV sensitive dyes may have distinctive fluorescence under UV exposure or may fluoresce differently under short-wave versus long-wave ultraviolet.

==== Enhancing contrast of ink ====
Using multi-spectral imaging it is possible to read illegible [[papyrus]], such as the burned papyri of the [[Villa of the Papyri]] or of [[Oxyrhynchus]], or the [[Archimedes palimpsest]]. The technique involves taking pictures of the illegible document using different filters in the infrared or ultraviolet range, finely tuned to capture certain wavelengths of light. Thus, the optimum spectral portion can be found for distinguishing ink from paper on the papyrus surface.

Simple NUV sources can be used to highlight faded iron-based [[ink]] on [[vellum]].<ref>
{{cite web
 |title=Digital photography of documents
 |publisher=wells-genealogy.org.uk
 |url=http://www.wells-genealogy.org.uk/photography.htm
 |url-status=dead
 |archive-url=https://archive.today/20120919133157/http://www.wells-genealogy.org.uk/photography.htm
 |archive-date=2012-09-19
}}
</ref>

==== Sanitary compliance ====
[[File:Ultra-violet screening for potentially Ebola-carrying liquids (15811190376).jpg|alt=A person wearing full protective gear, glowing in ultraviolet light|thumb|After a training exercise involving fake [[body fluids]], a healthcare worker's [[personal protective equipment]] is checked with ultraviolet to find invisible drops of fluids. These fluids could contain deadly viruses or other contamination.]]
Ultraviolet helps detect organic material deposits that remain on surfaces where periodic cleaning and sanitizing may have failed. It is used in the hotel industry, manufacturing, and other industries where levels of cleanliness or contamination are [[Inspection|inspected]].<ref>
{{cite web
 |title=Defining "What is clean?"
 |series=Integrated cleaning and measurement
 |publisher=Healthy Facilities Institute
 |url=http://www.healthyfacilitiesinstitute.com/a_353-Defining_What_is_Clean
 |language=en |url-status=usurped |access-date=24 June 2017
 |archive-url=https://web.archive.org/web/20170921171252/http://www.healthyfacilitiesinstitute.com/a_353-Defining_What_is_Clean
 |archive-date=21 September 2017
}}
</ref><ref>{{cite news
 |title=Non-destructive inspection: Seeing through the B‑52
 |publisher=[[U.S. Air Force]]
 |website=afgsc.af.mil
 |url=https://www.afgsc.af.mil/News/Article-Display/Article/989575/non-destructive-inspection-seeing-through-the-b-52/
 |access-date=24 June 2017
 |archive-date=16 November 2017
 |archive-url=https://web.archive.org/web/20171116031617/http://www.afgsc.af.mil/News/Article-Display/Article/989575/non-destructive-inspection-seeing-through-the-b-52/
 |url-status=live
 }}</ref><ref>
{{cite magazine
 |last1=Escobar  |first1=David
 |date=20 April 2015
 |title=Oxygen cleaning: A validated process is critical for safety
 |magazine=Valve Magazine
 |url=http://www.valvemagazine.com/web-only/categories/technical-topics/6658-oxygen-cleaning-a-validated-process-is-critical-for-safety.html
 |lang=en-gb  |url-status=live
 |archive-url=https://web.archive.org/web/20171115202939/http://www.valvemagazine.com/web-only/categories/technical-topics/6658-oxygen-cleaning-a-validated-process-is-critical-for-safety.html
 |archive-date=15 November 2017
}}
</ref><ref>
{{cite book
 |last1=Raj          |first1=Baldev
 |last2=Jayakumar    |first2=T.
 |last3=Thavasimuthu |first3=M.
 |date=2002
 |title=Practical Non-destructive Testing
 |page=10  |language=en-gb
 |publisher=Woodhead Publishing
 |isbn=9781855736009
 |url=https://books.google.com/books?id=qXcCKsL2IMUC&pg=PA10
}}
</ref>

Perennial news features for many television news organizations involve an investigative reporter using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such.<ref>
{{cite magazine
 |title=New investigation finds some hotels don't wash sheets between guests
 |date=15 September 2016
 |magazine=House Beautiful
 |url=http://www.housebeautiful.com/lifestyle/news/a7060/clean-hotel-bed-sheets/
 |language=en |url-status=live
 |archive-url=https://web.archive.org/web/20170703053642/http://www.housebeautiful.com/lifestyle/news/a7060/clean-hotel-bed-sheets/
 |archive-date=3 July 2017
}}
</ref><ref>
{{cite news
 |title=What's hiding in your hotel room?
 |date=17 November 2010
 |website=ABC News
 |url=https://abcnews.go.com/GMA/Health/hiding-hotel-room/story?id=1507794
 |url-status=live
 |archive-url=https://web.archive.org/web/20160722060221/https://abcnews.go.com/GMA/Health/hiding-hotel-room/story?id=1507794
 |archive-date=22 July 2016
}}
</ref>

==== Chemistry ====
[[UV/Vis spectroscopy]] is widely used as a technique in [[chemistry]] to analyze [[chemical structure]], the most notable one being [[conjugated system]]s. UV radiation is often used to excite a given sample where the fluorescent emission is measured with a [[spectrofluorometer]]. In biological research, UV radiation is used for [[quantification of nucleic acids]] or [[protein]]s. In environmental chemistry, UV radiation could also be used to detect [[Contaminants of emerging concern]] in water samples.<ref name="ReferenceA" />

In pollution control applications, ultraviolet analyzers are used to detect emissions of nitrogen oxides, sulfur compounds, mercury, and ammonia, for example in the flue gas of fossil-fired power plants.<ref>
{{cite book
 |editor-first=N.E. |editor-last=Battikha
 |year=2007
 |title=The Condensed Handbook of Measurement and Control
 |edition=3rd |pages=65–66
 |publisher=ISA
 |isbn=978-1-55617-995-2
}}
</ref> Ultraviolet radiation can detect thin sheens of [[oil spill|spilled oil]] on water, either by the high reflectivity of oil films at UV wavelengths, fluorescence of compounds in oil, or by absorbing of UV created by [[Raman scattering]] in water.<ref>
{{cite book
 |editor-first=Mervin |editor-last=Fingas
 |year=2011 |title=Oil Spill Science and Technology
 |pages=123–124
 |publisher=Elsevier
 |isbn=978-1-85617-943-0
}}</ref> UV absorbance can also be used to quantify contaminants in wastewater. Most commonly used 254&nbsp;nm UV absorbance is generally used as a surrogate parameters to quantify NOM.<ref name="ReferenceA">{{Cite journal |last1=Lee |first1=Brandon Chuan Yee |last2=Lim |first2=Fang Yee |last3=Loh |first3=Wei Hao |last4=Ong |first4=Say Leong |last5=Hu |first5=Jiangyong |date=January 2021 |title=Emerging Contaminants: An Overview of Recent Trends for Their Treatment and Management Using Light-Driven Processes |journal=Water |language=en |volume=13 |issue=17 |pages=2340 |doi=10.3390/w13172340 |issn=2073-4441 |doi-access=free |bibcode=2021Water..13.2340L }}</ref> Another form of light-based detection method uses a wide spectrum of excitation emission matrix (EEM) to detect and identify contaminants based on their flourense properties.<ref name="ReferenceA"/><ref>{{Cite web |title=What is an Excitation Emission Matrix (EEM)? |url=https://www.horiba.com/int/scientific/technologies/fluorescence-spectroscopy/what-is-an-excitation-emission-matrix-eem/ |access-date=2023-07-10 |website=horiba.com |language=en |archive-date=10 July 2023 |archive-url=https://web.archive.org/web/20230710083853/https://www.horiba.com/int/scientific/technologies/fluorescence-spectroscopy/what-is-an-excitation-emission-matrix-eem/ |url-status=live }}</ref> EEM could be used to discriminate different groups of NOM based on the difference in light emission and excitation of fluorophores. NOMs with certain molecular structures are reported to have fluorescent properties in a wide range of excitation/emission wavelengths.<ref>{{Cite journal |last1=Sierra |first1=M.M.D. |last2=Giovanela |first2=M. |last3=Parlanti |first3=E. |last4=Soriano-Sierra |first4=E.J. |date=February 2005 |title=Fluorescence fingerprint of fulvic and humic acids from varied origins as viewed by single-scan and excitation/emission matrix techniques |url=http://dx.doi.org/10.1016/j.chemosphere.2004.09.038 |journal=Chemosphere |volume=58 |issue=6 |pages=715–733 |doi=10.1016/j.chemosphere.2004.09.038 |pmid=15621185 |bibcode=2005Chmsp..58..715S |issn=0045-6535 |access-date=10 July 2023 |archive-date=29 May 2024 |archive-url=https://web.archive.org/web/20240529134758/https://www.sciencedirect.com/science/article/abs/pii/S0045653504008185?via%3Dihub |url-status=live |url-access=subscription }}</ref><ref name="ReferenceA"/>

[[File:Fluorescent minerals hg.jpg|thumb|right|A collection of mineral samples fluorescing brilliantly at various wavelengths as seen while being irradiated by UV]]
Ultraviolet lamps are also used as part of the analysis of some [[mineral]]s and [[gems]].

===Material science uses===

====Fire detection====
{{see also|Flame detector}}
In general, ultraviolet detectors use either a solid-state device, such as one based on [[silicon carbide]] or [[aluminium nitride]], or a gas-filled tube as the sensing element. UV detectors that are sensitive to UV in any part of the spectrum respond to irradiation by [[sunlight]] and [[artificial light]]. A burning hydrogen flame, for instance, radiates strongly in the 185- to 260-nanometer range and only very weakly in the [[Infrared|IR]] region, whereas a coal fire emits very weakly in the UV band yet very strongly at IR wavelengths; thus, a fire detector that operates using both UV and IR detectors is more reliable than one with a UV detector alone. Virtually all fires emit some [[thermal radiation|radiation]] in the UVC band, whereas the [[Sun]]'s radiation at this band is absorbed by the [[Earth's atmosphere]]. The result is that the UV detector is "solar blind", meaning it will not cause an alarm in response to radiation from the Sun, so it can easily be used both indoors and outdoors.

UV detectors are sensitive to most fires, including [[hydrocarbon]]s, metals, [[sulfur]], [[hydrogen]], [[hydrazine]], and [[ammonia]]. [[Arc welding]], electrical arcs, [[lightning]], [[X-ray]]s used in nondestructive metal testing equipment (though this is highly unlikely), and radioactive materials can produce levels that will activate a UV detection system. The presence of UV-absorbing gases and vapors will attenuate the UV radiation from a fire, adversely affecting the ability of the detector to detect flames. Likewise, the presence of an oil mist in the air or an oil film on the detector window will have the same effect.

==== Photolithography ====
Ultraviolet radiation is used for very fine resolution [[photolithography]], a procedure wherein a chemical called a photoresist is exposed to UV radiation that has passed through a mask. The exposure causes chemical reactions to occur in the photoresist. After removal of unwanted photoresist, a pattern determined by the mask remains on the sample. Steps may then be taken to "etch" away, deposit on or otherwise modify areas of the sample where no photoresist remains.

Photolithography is used in the manufacture of [[semiconductor]]s, [[integrated circuit]] components,<ref>{{cite web | title = Deep UV Photoresists | date = 23 February 2001 | url = http://www.almaden.ibm.com/st/chemistry/lithography/deep_uv/ | archive-url = https://web.archive.org/web/20060312012823/http://www.almaden.ibm.com/st/chemistry/lithography/deep_uv/ | archive-date = 2006-03-12}}</ref> and [[printed circuit board]]s. Photolithography processes used to fabricate electronic integrated circuits presently use 193&nbsp;nm UV and are experimentally using 13.5&nbsp;nm UV for [[extreme ultraviolet lithography]].

====Polymers====
Electronic components that require clear transparency for light to exit or enter (photovoltaic panels and sensors) can be potted using acrylic resins that are cured using UV energy. The advantages are low VOC emissions and rapid curing.

[[File:UV effect on finished wood.jpg|thumb|Effects of UV on finished surfaces in 0, 20 and 43 hours]]
Certain inks, coatings, and [[adhesive]]s are formulated with [[photoinitiator]]s and resins. When exposed to UV light, [[polymerization]] occurs, and so the adhesives harden or cure, usually within a few seconds. Applications include glass and plastic bonding, [[optical fiber]] coatings, the coating of flooring, [[UV coating]] and paper finishes in offset [[printing]], dental fillings, and decorative fingernail "gels".

UV sources for UV curing applications include [[UV lamps]], UV [[LED]]s, and [[excimer]] flash lamps. Fast processes such as flexo or offset printing require high-intensity light focused via reflectors onto a moving substrate and medium so high-pressure [[Mercury (element)|Hg]] (mercury) or [[Iron|Fe]] (iron, doped)-based bulbs are used, energized with electric arcs or microwaves. Lower-power fluorescent lamps and LEDs can be used for static applications. Small high-pressure lamps can have light focused and transmitted to the work area via liquid-filled or fiber-optic light guides.

The impact of UV on polymers is used for modification of the ([[surface roughness|roughness]] and [[hydrophobicity]]) of polymer surfaces. For example, a [[poly(methyl methacrylate)]] surface can be smoothed by vacuum ultraviolet.<ref>{{cite journal|author1=R. V. Lapshin|author2=A. P. Alekhin|author3=A. G. Kirilenko|author4=S. L. Odintsov|author5=V. A. Krotkov|year=2010|title=Vacuum ultraviolet smoothing of nanometer-scale asperities of poly(methyl methacrylate) surface|journal=Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques|volume=4|issue=1|pages=1–11|issn=1027-4510|doi=10.1134/S1027451010010015|bibcode=2010JSIXS...4....1L |s2cid=97385151|url=http://www.lapshin.fast-page.org/publications.htm#vacuum2010|url-status=live|archive-url=https://web.archive.org/web/20130909230837/http://www.lapshin.fast-page.org/publications.htm#vacuum2010|archive-date=9 September 2013|url-access=subscription}}</ref>

UV radiation is useful in preparing low-surface-energy [[polymer]]s for adhesives. Polymers exposed to UV will oxidize, thus raising the [[surface energy]] of the polymer. Once the surface energy of the polymer has been raised, the bond between the adhesive and the polymer is stronger.

===Biology-related uses===

====Air purification====

UV-C light is used in air conditioning systems as a method of improving indoor air quality by disinfecting the air and preventing microbial growth. UV-C light is effective at killing or inactivating harmful microorganisms, such as bacteria, viruses, mold, and mildew. When integrated into an air conditioning system, the ultraviolet light is typically placed in areas like the [[air handler]] or near the [[Evaporator|evaporator coil]].
In air conditioning systems, UV-C light works by irradiating the airflow within the system, killing or neutralizing harmful microorganisms before they are recirculated into the indoor environment. The effectiveness of it in air conditioning systems depends on factors such as the intensity of the light, the duration of exposure, airflow speed, and the cleanliness of system components.<ref>{{Cite journal |last1=Thornton |first1=Gail M. |last2=Fleck |first2=Brian A. |last3=Fleck |first3=Natalie |last4=Kroeker |first4=Emily |last5=Dandnayak |first5=Dhyey |last6=Zhong |first6=Lexuan |last7=Hartling |first7=Lisa |date=2022-04-08 |title=The impact of heating, ventilation, and air conditioning design features on the transmission of viruses, including the 2019 novel coronavirus: A systematic review of ultraviolet radiation |journal=PLOS ONE |language=en |volume=17 |issue=4 |pages=e0266487 |doi=10.1371/journal.pone.0266487 |doi-access=free |issn=1932-6203 |pmc=8992995 |pmid=35395010|bibcode=2022PLoSO..1766487T }}</ref><ref>{{Cite journal |last1=Abkar |first1=Leili |last2=Zimmermann |first2=Karl |last3=Dixit |first3=Fuhar |last4=Kheyrandish |first4=Ataollah |last5=Mohseni |first5=Madjid |date=2022-11-01 |title=COVID-19 pandemic lesson learned- critical parameters and research needs for UVC inactivation of viral aerosols |journal=Journal of Hazardous Materials Advances |volume=8 |pages=100183 |doi=10.1016/j.hazadv.2022.100183 |issn=2772-4166 |pmc=9553962 |pmid=36619826|bibcode=2022JHzMA...800183A }}</ref>

Using a [[Photocatalysis|catalytic chemical reaction]] from [[titanium dioxide]] and UVC exposure, [[oxidation]] of organic matter converts [[pathogens]], [[pollens]], and [[mold]] [[spores]] into harmless inert byproducts. However, the reaction of titanium dioxide and UVC is not a straight path. Several hundreds of reactions occur prior to the inert byproducts stage and can hinder the resulting reaction creating [[formaldehyde]], aldehyde, and other VOC's en route to a final stage. Thus, the use of titanium dioxide and UVC requires very specific parameters for a successful outcome. The cleansing mechanism of UV is a photochemical process. Contaminants in the indoor environment are almost entirely organic carbon-based compounds, which break down when exposed to high-intensity UV at 240 to 280&nbsp;nm. Short-wave ultraviolet radiation can destroy DNA in living microorganisms.<ref>{{Cite news|url=https://bestledgrowlightsinfo.com/the-importance-of-uv-light-for-plants-cultivated-indoors/|title=The Importance of UV Light for Plants Cultivated Indoors|date=2017-06-11|work=Best LED Grow Lights Info|access-date=2017-06-24|language=en-US|archive-date=30 July 2018|archive-url=https://web.archive.org/web/20180730203142/https://bestledgrowlightsinfo.com/the-importance-of-uv-light-for-plants-cultivated-indoors/|url-status=live}}</ref> UVC's effectiveness is directly related to intensity and exposure time.

UV has also been shown to reduce gaseous contaminants such as [[carbon monoxide]] and [[VOCs]].<ref>{{cite journal |last1=Scott|first1=K.J. |last2=Wills|first2=R.R.H. |last3=Patterson|first3=B.D. |year=1971 |journal=Journal of the Science of Food and Agriculture |doi=10.1002/jsfa.2740220916 |title= Removal by ultra-violet lamp of ethylene and other hydrocarbons produced by bananas |volume=22|pages=496–7|issue=9|bibcode=1971JSFA...22..496S }}</ref><ref>{{cite journal |last1=Scott|first1=KJ |last2=Wills|first2=RBH |title=Atmospheric pollutants destroyed in an ultra violet scrubber |year=1973 |journal=Laboratory Practice|volume=22 |issue=2|pages=103–6 |pmid=4688707}}</ref><ref>{{cite journal |last1=Shorter|first1=AJ |last2=Scott|first2=KJ |year=1986|title=Removal of ethylene from air and low oxygen atmospheres with ultra violet radiation|journal=Lebensm-Wiss U Technology |volume=19|pages=176–9}}</ref> UV lamps radiating at 184 and 254&nbsp;nm can remove low concentrations of [[hydrocarbons]] and [[carbon monoxide]] if the air is recycled between the room and the lamp chamber. This arrangement prevents the introduction of ozone into the treated air. Likewise, air may be treated by passing by a single UV source operating at 184&nbsp;nm and passed over iron pentaoxide to remove the ozone produced by the UV lamp.

====Sterilization and disinfection====
{{Main|Ultraviolet germicidal irradiation|Germicidal lamp}}

[[File:UV-ontsmetting laminaire-vloeikast.JPG|thumb|right|A low-pressure mercury vapor discharge tube floods the inside of a [[Fume hood|hood]] with shortwave UV light when not in use, [[Asepsis|sterilizing]] microbiological contaminants from irradiated surfaces.]]

[[Ultraviolet lamp]]s are used to [[sterilization (microbiology)|sterilize]] workspaces and tools used in biology laboratories and medical facilities. Commercially available low-pressure [[mercury-vapor lamps]] emit about 86% of their radiation at 254 nanometers (nm), with 265&nbsp;nm being the peak germicidal effectiveness curve. UV at these germicidal wavelengths damage a microorganism's DNA/RNA so that it cannot reproduce, making it harmless, (even though the organism may not be killed).<ref>{{cite news |last1=Chang |first1=Kenneth |title=Scientists Consider Indoor Ultraviolet Light to Zap Coronavirus in the Air |url=https://www.nytimes.com/2020/05/07/science/ultraviolet-light-coronavirus.html |archive-url=https://web.archive.org/web/20200507214905/https://www.nytimes.com/2020/05/07/science/ultraviolet-light-coronavirus.html |archive-date=2020-05-07 |url-access=subscription |url-status=live |website=The New York Times |date=7 May 2020 |access-date=9 May 2020}}</ref> Since microorganisms can be shielded from ultraviolet rays in small cracks and other shaded areas, these lamps are used only as a supplement to other sterilization techniques.

UVC LEDs are relatively new to the commercial market and are gaining in popularity.{{Failed verification|date=April 2020}}<ref>{{cite journal|author1=Welch, David |display-authors=et al |title=Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases|journal=Scientific Reports|volume=8|issue=1|pages=2752|doi=10.1038/s41598-018-21058-w|pmid=29426899|pmc=5807439|issn=2045-2322|date=January 2018|bibcode=2018NatSR...8.2752W}}</ref> Due to their monochromatic nature (±5&nbsp;nm){{Failed verification|date=April 2020}} these LEDs can target a specific wavelength needed for disinfection. This is especially important knowing that pathogens vary in their sensitivity to specific UV wavelengths. LEDs are mercury free, instant on/off, and have unlimited cycling throughout the day.<ref>{{cite web|url=https://www.wateronline.com/doc/coming-of-age-uv-c-led-technology-update-0001|title=Coming of Age UV-C LED Technology Update|website=wateronline.com|url-status=live|archive-url=https://web.archive.org/web/20170420045809/https://www.wateronline.com/doc/coming-of-age-uv-c-led-technology-update-0001|archive-date=20 April 2017}}</ref>

[[Disinfection]] using UV radiation is commonly used in [[wastewater]] treatment applications and is finding an increased usage in municipal drinking [[water treatment]]. Many bottlers of spring water use UV disinfection equipment to sterilize their water. [[Solar water disinfection]]<ref>{{cite web |url=http://www.sodis.ch/index_EN |title=Solar Water Disinfection |publisher=Sodis.ch |date=2 April 2011 |access-date=2011-11-08 |url-status=dead |archive-url=https://web.archive.org/web/20120831050355/http://www.sodis.ch/index_EN |archive-date=31 August 2012 }}</ref> has been researched for cheaply treating contaminated water using natural [[sunlight]]. The UVA irradiation and increased water temperature kill organisms in the water.

Ultraviolet radiation is used in several food processes to kill unwanted [[microorganisms]]. UV can be used to [[pasteurize]] fruit juices by flowing the juice over a high-intensity ultraviolet source. The effectiveness of such a process depends on the UV [[absorbance]] of the juice.

[[Pulsed light]] (PL) is a technique of killing microorganisms on surfaces using pulses of an intense broad spectrum, rich in UVC between 200 and 280 [[Nanometer|nm]]. Pulsed light works with [[xenon flash lamp]]s that can produce flashes several times per second. [[Disinfection robot]]s use pulsed UV.<ref>{{cite web|url=http://www.xenex.com/xenex-robot/|title=Video Demos|url-status=dead|archive-url=https://web.archive.org/web/20141219140317/http://www.xenex.com/xenex-robot/|archive-date=19 December 2014|access-date=27 November 2014}}</ref>

The antimicrobial effectiveness of filtered [[far-UVC]] (222 nm) light on a range of pathogens, including bacteria and fungi showed inhibition of pathogen growth, and since it has lesser harmful effects, it provides essential insights for reliable disinfection in healthcare settings, such as hospitals and long-term care homes.<ref>{{Cite journal |last1=Lorenzo-Leal |first1=Ana C. |last2=Tam |first2=Wenxi |last3=Kheyrandish |first3=Ata |last4=Mohseni |first4=Madjid |last5=Bach |first5=Horacio |date=2023-10-31 |editor-last=Barbosa |editor-first=Joana |title=Antimicrobial Activity of Filtered Far-UVC Light (222 nm) against Different Pathogens |journal=BioMed Research International |language=en |volume=2023 |issue=1 |pages=1–8 |doi=10.1155/2023/2085140 |issn=2314-6141 |pmc=10630020 |pmid=37942030 |doi-access=free }}</ref> UVC has also been shown to be effective at degrading SARS-CoV-2 virus.<ref>{{cite journal | doi=10.1021/acsphotonics.3c00828 | title=Mechanisms of SARS-CoV-2 Inactivation Using UVC Laser Radiation | date=2023 | last1=Devitt | first1=George | last2=Johnson | first2=Peter B. | last3=Hanrahan | first3=Niall | last4=Lane | first4=Simon I. R. | last5=Vidale | first5=Magdalena C. | last6=Sheth | first6=Bhavwanti | last7=Allen | first7=Joel D. | last8=Humbert | first8=Maria V. | last9=Spalluto | first9=Cosma M. | last10=Hervé | first10=Rodolphe C. | last11=Staples | first11=Karl | last12=West | first12=Jonathan J. | last13=Forster | first13=Robert | last14=Divecha | first14=Nullin | last15=McCormick | first15=Christopher J. | last16=Crispin | first16=Max | last17=Hempler | first17=Nils | last18=Malcolm | first18=Graeme P. A. | last19=Mahajan | first19=Sumeet | journal=ACS Photonics | volume=11 | issue=1 | pages=42–52 | pmid=38249683 | pmc=10797618 }}</ref>

====Biological====
Some animals, including birds, reptiles, and insects such as bees, can see near-ultraviolet wavelengths. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision. Scorpions glow or take on a yellow to green color under UV illumination, thus assisting in the control of these arachnids. Many birds have patterns in their plumage that are invisible at usual wavelengths but observable in ultraviolet, and the urine and other secretions of some animals, including dogs, cats, and human beings, are much easier to spot with ultraviolet. Urine trails of rodents can be detected by pest control technicians for proper treatment of infested dwellings.

Butterflies use ultraviolet as a [[Ultraviolet communication in butterflies|communication system]] for sex recognition and mating behavior. For example, in the ''[[Colias eurytheme]]'' butterfly, males rely on visual cues to locate and identify females. Instead of using chemical stimuli to find mates, males are attracted to the ultraviolet-reflecting color of female hind wings.<ref>{{cite journal | last1 = Silberglied | first1 = Robert E. | last2 = Taylor | first2 = Orley R. | year = 1978 | title = Ultraviolet Reflection and Its Behavioral Role in the Courtship of the Sulfur Butterflies Colias eurytheme and C. philodice (Lepidoptera, Pieridae) | journal = Behavioral Ecology and Sociobiology | volume = 3 | issue = 3| pages = 203–43 | doi=10.1007/bf00296311| bibcode = 1978BEcoS...3..203S | s2cid = 38043008 }}</ref> In ''[[Pieris napi]]'' butterflies it was shown that females in northern Finland with less UV-radiation present in the environment possessed stronger UV signals to attract their males than those occurring further south. This suggested that it was evolutionarily more difficult to increase the UV-sensitivity of the eyes of the males than to increase the UV-signals emitted by the females.<ref name= "Meyer-Rohow & Järvilehto 1997">{{cite journal| last1=Meyer-Rochow|first1=V.B.|last2=Järvilehto|first2=M.|title=Ultraviolet colours in Pieris napi from northern and southern Finland: Arctic females are the brightest!| journal= Naturwissenschaften|date=1997|volume=84|issue=4|pages= 165–168|bibcode=1997NW.....84..165M|doi=10.1007/s001140050373|s2cid=46142866}}</ref>

Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. A local ultraviolet emitter will normally disrupt the navigation process and will eventually attract the flying insect.
[[File:ultraviolet trap entomologist.jpg|thumb|right|Entomologist using a UV lamp for collecting [[beetles]] in [[Chaco Department|Chaco]], [[Paraguay]]]]

The [[green fluorescent protein]] (GFP) is often used in [[genetics]] as a marker. Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are of interest in biochemistry and related fields. UV-capable spectrophotometers are common in such laboratories.

Ultraviolet traps called [[bug zapper]]s are used to eliminate various small flying insects. They are attracted to the UV and are killed using an electric shock, or trapped once they come into contact with the device. Different designs of ultraviolet radiation traps are also used by [[entomologists]] for [[collecting]] [[nocturnal]] insects during [[faunistic]] survey studies.

====Therapy====
{{main|Ultraviolet light therapy}}
Ultraviolet radiation is helpful in the treatment of [[skin conditions]] such as [[psoriasis]] and [[vitiligo]]. Exposure to UVA, while the skin is hyper-photosensitive, by taking [[psoralen]]s is an effective treatment for [[psoriasis]]. Due to the potential of [[psoralens]] to cause damage to the [[liver]], [[PUVA therapy]] may be used only a limited number of times over a patient's lifetime.

UVB phototherapy does not require additional medications or topical preparations for the therapeutic benefit; only the exposure is needed. However, phototherapy can be effective when used in conjunction with certain topical treatments such as anthralin, coal tar, and [[vitamin A]] and D derivatives, or systemic treatments such as [[methotrexate]] and [[Soriatane]].<ref>
{{cite web |title = UVB Phototherapy |url = http://www.psoriasis.org/treatment/psoriasis/phototherapy/uvb.php |archive-url=https://web.archive.org/web/20070622180124/http://www.psoriasis.org/treatment/psoriasis/phototherapy/uvb.php |archive-date=22 June 2007 |format=php |access-date=2007-09-23 |publisher=National Psoriasis Foundation, USA}}</ref>

====Herpetology====
[[Reptile]]s need UVB for biosynthesis of vitamin D, and other metabolic processes.<ref>{{Cite journal |last1=Diehl |first1=J. J. E. |last2=Baines |first2=F. M. |last3=Heijboer |first3=A. C. |last4=van Leeuwen |first4=J. P. |last5=Kik |first5=M. |last6=Hendriks |first6=W. H. |last7=Oonincx |first7=D. G. A. B. |date=February 2018 |title=A comparison of UVb compact lamps in enabling cutaneous vitamin D synthesis in growing bearded dragons |journal=Journal of Animal Physiology and Animal Nutrition |language=en |volume=102 |issue=1 |pages=308–316 |doi=10.1111/jpn.12728 |pmid=28452197 |s2cid=30124686 |doi-access=free |url=https://dspace.library.uu.nl/bitstream/handle/1874/360841/Diehl_et_al_2018_Journal_of_Animal_Physiology_and_Animal_Nutrition_1_.pdf?sequence=1&isAllowed=y }}</ref> Specifically [[cholecalciferol]] (vitamin D3), which is needed for basic cellular / neural functioning as well as the utilization of calcium for bone and egg production.{{Citation needed|date=April 2022}} The UVA wavelength is also visible to many reptiles and might play a significant role in their ability survive in the wild as well as in visual communication between individuals.{{Citation needed|date=April 2022}} Therefore, in a typical reptile enclosure, a fluorescent UV a/b source (at the proper strength / spectrum for the species), must be available for many{{Which|date=April 2022}} captive species to survive. Simple supplementation with [[cholecalciferol]] (Vitamin D3) will not be enough as there is a complete biosynthetic pathway{{Which|date=May 2022}} that is "leapfrogged" (risks of possible overdoses), the intermediate molecules and metabolites{{Which|date=April 2022}} also play important functions in the animals health.{{Citation needed|date=April 2022}} Natural sunlight in the right levels is always going to be superior to artificial sources, but this might not be possible for keepers in different parts of the world.{{Citation needed|date=April 2022}}

It is a known problem that high levels of output of the UVa part of the spectrum can both cause cellular and DNA damage to sensitive parts of their bodies – especially the eyes where blindness is the result of an improper UVa/b source use and placement [[photokeratitis]].{{Citation needed|date=April 2022}} For many keepers there must also be a provision for an adequate heat source this has resulted in the marketing of heat and light "combination" products.{{Citation needed|date=April 2022}} Keepers should be careful of these "combination" light/ heat and UVa/b generators, they typically emit high levels of UVa with lower levels of UVb that are set and difficult to control so that animals can have their needs met.{{Citation needed|date=April 2022}} A better strategy is to use individual sources of these elements and so they can be placed and controlled by the keepers for the max benefit of the animals.<ref>{{cite web|url=http://www.uvguide.co.uk/vitdpathway.htm|title=Vitamin D and Ultraviolet Light – a remarkable process|website=UV Guide UK|access-date=2017-01-13|url-status=live|archive-url=https://web.archive.org/web/20160531172209/http://www.uvguide.co.uk/vitdpathway.htm|archive-date=31 May 2016}}</ref>