Editing Light-emitting diode (section)

=== Biological detection ===
The discovery of radiative recombination in aluminum gallium nitride (AlGaN) alloys by [[United States Army Research Laboratory|U.S. Army Research Laboratory]] (ARL) led to the conceptualization of UV light-emitting diodes (LEDs) to be incorporated in light-induced [[fluorescence]] sensors used for biological agent detection.<ref>{{Citation |last1=Sampath |first1=A. V. |title=The effects of increasing AlN mole fraction on the performance of AlGaN active regions containing nanometer scale compositionally imhomogeneities |date=2009-12-01 |work=Advanced High Speed Devices |volume=51 |pages=69–76 |series=Selected Topics in Electronics and Systems |publisher=World Scientific |doi=10.1142/9789814287876_0007 |isbn=9789814287869 |last2=Reed |first2=M. L. |last3=Moe |first3=C. |last4=Garrett |first4=G. A. |last5=Readinger |first5=E. D. |last6=Sarney |first6=W. L. |last7=Shen |first7=H. |last8=Wraback |first8=M. |last9=Chua |first9=C.}}</ref><ref name=":1">{{Cite journal |last1=Liao |first1=Yitao |last2=Thomidis |first2=Christos |last3=Kao |first3=Chen-kai |last4=Moustakas |first4=Theodore D. |date=2011-02-21 |title=AlGaN based deep ultraviolet light emitting diodes with high internal quantum efficiency grown by molecular beam epitaxy |journal=Applied Physics Letters |volume=98 |issue=8 |pages=081110 |doi=10.1063/1.3559842 |issn=0003-6951 |bibcode=2011ApPhL..98h1110L |doi-access=free}}</ref><ref name=":2">{{Cite journal |last1=Cabalo |first1=Jerry |last2=DeLucia |first2=Marla |last3=Goad |first3=Aime |last4=Lacis |first4=John |last5=Narayanan |first5=Fiona |last6=Sickenberger |first6=David |date=2008-10-02 |title=Overview of the TAC-BIO detector |journal=Optically Based Biological and Chemical Detection for Defence IV |publisher=International Society for Optics and Photonics |volume=7116 |pages=71160D |doi=10.1117/12.799843 |editor1-last=Carrano |editor1-first=John C. |editor2-last=Zukauskas |editor2-first=Arturas |bibcode=2008SPIE.7116E..0DC |s2cid=108562187}}</ref> In 2004, the [[Edgewood Chemical Biological Center|Edgewood Chemical Biological Center (ECBC)]] initiated the effort to create a biological detector named TAC-BIO. The program capitalized on semiconductor UV optical sources (SUVOS) developed by the [[DARPA|Defense Advanced Research Projects Agency (DARPA)]].<ref name=":2" />

UV-induced fluorescence is one of the most robust techniques used for rapid real-time detection of biological aerosols.<ref name=":2" /> The first UV sensors were lasers lacking in-field-use practicality. In order to address this, DARPA incorporated SUVOS technology to create a low-cost, small, lightweight, low-power device. The TAC-BIO detector's response time was one minute from when it sensed a biological agent. It was also demonstrated that the detector could be operated unattended indoors and outdoors for weeks at a time.<ref name=":2" />

Aerosolized biological particles fluoresce and scatter light under a UV light beam. Observed fluorescence is dependent on the applied wavelength and the biochemical fluorophores within the biological agent. UV induced fluorescence offers a rapid, accurate, efficient and logistically practical way for biological agent detection. This is because the use of UV fluorescence is reagentless, or a process that does not require an added chemical to produce a reaction, with no consumables, or produces no chemical byproducts.<ref name=":2" />

Additionally, TAC-BIO can reliably discriminate between threat and non-threat aerosols. It was claimed to be sensitive enough to detect low concentrations, but not so sensitive that it would cause false positives. The particle-counting algorithm used in the device converted raw data into information by counting the photon pulses per unit of time from the fluorescence and scattering detectors, and comparing the value to a set threshold.<ref>{{Cite journal |last1=Poldmae |first1=Aime |last2=Cabalo |first2=Jerry |last3=De Lucia |first3=Marla |last4=Narayanan |first4=Fiona |last5=Strauch III |first5=Lester |last6=Sickenberger |first6=David |date=2006-09-28 |title=Biological aerosol detection with the tactical biological (TAC-BIO) detector |journal=Optically Based Biological and Chemical Detection for Defence III |volume=6398 |pages=63980E |publisher=SPIE |doi=10.1117/12.687944 |s2cid=136864366 |editor1-last=Carrano |editor1-first=John C. |editor2-last=Zukauskas |editor2-first=Arturas}}</ref>

The original TAC-BIO was introduced in 2010, while the second-generation TAC-BIO GEN&nbsp;II, was designed in 2015 to be more cost-efficient, as plastic parts were used. Its small, light-weight design allows it to be mounted to vehicles, robots, and unmanned aerial vehicles. The second-generation device could also be utilized as an environmental detector to monitor air quality in hospitals, airplanes, or even in households to detect fungus and mold.<ref>{{Cite web |url=https://www.army.mil/article/141363/army_advances_bio_threat_detector |title=Army advances bio-threat detector |website=www.army.mil |date=January 22, 2015 |access-date=2019-10-10}}</ref><ref>{{Cite journal |last1=Kesavan |first1=Jana |last2=Kilper |first2=Gary |last3=Williamson |first3=Mike |last4=Alstadt |first4=Valerie |last5=Dimmock |first5=Anne |last6=Bascom |first6=Rebecca |date=2019-02-01 |title=Laboratory validation and initial field testing of an unobtrusive bioaerosol detector for health care settings |journal=Aerosol and Air Quality Research |volume=19 |issue=2 |pages=331–344 |doi=10.4209/aaqr.2017.10.0371 |issn=1680-8584 |doi-access=free}}</ref>