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A Review of Light-Emitting Diodes and Ultraviolet Light-Emitting Diodes and Their Applications
This paper presents an extensive literature review on Light-Emitting Diode (LED) fundamentals and discusses the historical development of LEDs, focusing on the material selection, design employed, and modifications used in increasing the light output. It traces the evolutionary trajectory of the efficiency enhancement of ultraviolet (UV), blue, green, and red LEDs. It rigorously examines the diverse applications of LEDs, spanning from solid-state lighting to cutting-edge display technology, and their emerging role in microbial deactivation. A detailed overview of current trends and prospects in lighting and display technology is presented. Using the literature, this review offers valuable insights into the application of UV LEDs for microbial and potential viral disinfection. It conducts an in-depth exploration of the various microorganism responses to UV radiation based on the existing literature. Furthermore, the review investigates UV LED-based systems for water purification and surface disinfection. A prospective design for a solar-powered UV LED disinfection system is also delineated. The primary objective of this review article is to organize and synthesize pivotal information from the literature, offering a concise and focused overview of LED applications. From our review, we can conclude that the efficiency of LEDs has continuously increased since its invention and researchers are searching for methods to increase efficiency further. The demand for LED lighting and display applications is continuously increasing. Our analysis reveals an exciting horizon in microbial disinfection, where the integration of UV LED systems with cutting-edge technologies such as sensors, solar power, Internet-of-Things (IoT) devices, and artificial intelligence algorithms promises high levels of precision and efficacy in disinfection practices. This contribution sets the stage for future research endeavors in the domain of viral disinfection using solar-powered UV LED modules for universal applications.
Journal Article
Synthesis and luminescence properties of Sr.sub.2-xY.sub.xSi.sub.5-xAl.sub.xN.sub.8:Eu.sup.2+ red phosphor for white light-emitting diodes
To improve the luminescence properties of Sr.sub.2Si.sub.5N.sub.8:Eu.sup.2+ phosphor, Sr.sub.2-xY.sub.xSi.sub.5-xAl.sub.xN.sub.8:Eu.sup.2+ specimens in which Sr.sup.2+ and Si.sup.4+ were partially substituted with Y.sup.3+ and Al.sup.3+ were prepared by carbothermal reduction nitridation. The obtained Sr.sub.2-xY.sub.xSi.sub.5-xAl.sub.xN.sub.8:Eu.sup.2+ samples showed standard Sr.sub.2Si.sub.5N.sub.8 structure. The effects of Y.sup.3+ and Al.sup.3+ partial substitution on the structures and luminescence properties of the resulting specimens were investigated. Under excitation by near UV and blue radiation, Sr.sub.2Si.sub.5N.sub.8:Eu.sup.2+ exhibited a broad emission band at about 613 nm, originating from the 4f.sup.65d.sup.1 [right arrow] 4f.sup.7 transition of Eu.sup.2+. As Eu.sup.2+ concentration increased, the emission peak positions red-shifted from 606 to 628 nm, occupying two different crystallographic sites labeled as Eu(Sr1) and Eu(Sr2). Also, incorporation of both Y.sup.3+and Al.sup.3+ ions into Sr.sub.2Si.sub.5N.sub.8:Eu.sup.2+ significantly increased the luminescence intensity of Eu.sup.2+. This was attributed to modification of the crystal field environment of Eu.sup.2+. Overall, the improved luminescence intensities obtained through partial substitution of Sr.sup.2+ and Si.sup.4+ by Y.sup.3+ and Al.sup.3+, respectively, indicated the promise of Sr.sub.2-xY.sub.xSi.sub.5-xAl.sub.xN.sub.8:Eu.sup.2+ as red phosphor candidates in white light-emitting diodes at x = 0.16.
Journal Article
Shaping light for video in the age of LEDs : a practical guide to the art and craft of lighting
\"A practical, hands-on guide to lighting for video, this book explores how LEDs are changing the aesthetics of lighting and provides students with an indispensable guide to the everyday techniques required to produce professional quality lighting in the age of LEDs and wireless control options. The book focuses on first-hand application of technical knowledge, beginning with simple lighting setups and progressing to more complicated scenarios, and features accompanying diagrams, illustrations and case studies to demonstrate their real-world application. Key topics covered include basic three-point lighting, lighting moving actors, set lighting and exposure, instrument selection, bringing style to your lighting, color temperature and the Kelvin scale, exterior lighting, lighting categories and genres, green-screen techniques, money and budgeting, and electricity and electrical distribution. The book also provides guidance on career paths including what a grip does, case studies with photos and diagrams, and an extensive glossary of set terminology to introduce students to the language of filmmaking. A must have resource for film and media production students taking classes in lighting and/or cinematography\"-- Provided by publisher.
Book
Brightly luminescent and color-tunable CaMoO.sub.4:RE.sup.3+ nanofibers synthesized through a facile route for efficient light-emitting diodes
One-dimensional CaMoO.sub.4:RE.sup.3+ (RE = Eu, Sm, Dy, Tb) nanofibers were successfully synthesized through a facile supersaturated recrystallization process. These CaMoO.sub.4:Ln.sup.3+ nanofibers have the length ranging from 40 to 70 nm and the width of nearly 2 nm. Under UV excitation, these single-doped CaMoO.sub.4 nanofibers shown stronger emission, and the photoluminescence quantum efficiency is 25.7% (CaMoO.sub.4:Eu.sup.3+), 22.4% (CaMoO.sub.4:Sm.sup.3+), 23.2% (CaMoO.sub.4:Dy.sup.3+) and 27.7% (CaMoO.sub.4:Tb.sup.3+), respectively. Moreover, our work reveals that various emission colors can be obtained and tuned from pure red to delight green via co-doping Tb.sup.3+ and Eu.sup.3+ in the CaMoO.sub.4 host, and the energy transfer properties from Tb.sup.3+ to Eu.sup.3+ are also demonstrated. Finally, we apply the green CaMoO.sub.4:Tb.sup.3+, red CaMoO.sub.4:Eu.sup.3+ and white CaMoO.sub.4:0.05Tb.sup.3+, 0.02Eu.sup.3+ for LED devices, and these nanofiber-based LEDs present high efficiency and stability, which indicates the promising application in future optoelectronic fields.
Journal Article
Color-tunable luminescence properties of Sm.sup.3+/Dy.sup.3+ co-doped NaLa.sub.2 phosphors and their energy transfer mechanism
The Sm.sup.3+, Dy.sup.3+ doped and Sm.sup.3+/Dy.sup.3+ co-doped NaLa(MoO.sub.4).sub.2 spherical phosphors were hydrothermally synthesized by the EDTA-2Na mediated method. Under the excitation of 297 nm, the quenching concentration of Sm.sup.3+ in NaLa(MoO.sub.4).sub.2 host was determined to be 13%, and the concentration quenching mechanism was discussed to be the electric quadrupole-quadrupole interaction. After Sm.sup.3+ and Dy.sup.3+ ions were co-doped into the NaLa(MoO.sub.4).sub.2 host, the energy transfer behaviors resulted from Dy.sup.3+ to Sm.sup.3+ ions were investigated by the help of the luminescent spectra of the obtained phosphors. By varying co-doping concentrations of Sm.sup.3+/Dy.sup.3+ ions, the emission color of NaLa(MoO.sub.4).sub.2:Sm.sup.3+/Dy.sup.3+ can be tuned from reddish-orange, pink and white to bluish-green. The CIE chromaticity coordinate, the correlated color temperature and the quantum efficiency of NaLa.sub.0.87(MoO.sub.4).sub.2:1%Sm.sup.3+, 12%Dy.sup.3+ were calculated to be (0.356, 0.320), 4353 K and 20%, respectively. Furthermore, in the temperature-dependent analysis, it presented good thermal stability, which can become a promising single-phased white-emitting phosphor for white LEDs devices. Based on these results, the possible energy transfer mechanism between Dy.sup.3+ and Sm.sup.3+ in NaLa(MoO.sub.4).sub.2:Sm.sup.3+/Dy.sup.3+ was also proposed.
Journal Article