Persistent luminescence in Eu2+-doped compounds : a review

In 1996, Matsuzawa et al. reported on the extremely long-lasting afterglow of SrAl2O4:Eu2+ codoped with Dy3+ ions, which was more than 10-times brighter than the previously widely used ZnS:Cu,Co. Since then, research for stable and efficient persistent phosphors has continuously gained popularity. However, even today - almost 15 years after the discovery of SrAl2O4:Eu2+, Dy3+ - the number of persistent luminescent materials is still relatively low. Furthermore, the mechanism behind this phenomenon is still unclear. Although most authors agree on the general features, such as the existence of long-lived trap levels, many details are still shrouded in mystery. In this review, we present an overview of the important classes of known persistent luminescent materials based on Eu2+-emission and how they were prepared, and we take a closer look at the models and mechanisms that have been suggested to explain bright afterglow in various compounds

Manipulation of Ga2O3 Nanocrystals for the Design of Functional Phosphors

Transparent conducting oxides are of great interest in semiconductor research and industry. Their ability to carry electricity while remaining transparent allows them to be used for different applications including photovoltaics, lighting, and photocatalysis. Among transparent conducting oxides, Ga2O3 has the widest band gap and is characterized by a strong broad-band blue-green afterglow emission, making it attractive for various lighting applications. The main motivation of this thesis is to use these unique properties of Ga2O3 to design new phosphors with targeted optical properties. The research described in this thesis specifically focuses on generating white light by non-radiative energy transfer between Ga2O3 nanocrystals, as energy donors, and orange-red emitting semiconductor quantum dots, as energy acceptors, and using dopant-induced trap states to extend afterglow emission. Solution phase conjugation of colloidal nanocrystals allows for short-range energy transfer processes to occur with high probability, which is valuable for sensing and lighting. The first part of this thesis demonstrates the conjugation and electronic coupling of Ga2O3 nanocrystals with CdSe/CdS core/shell quantum dots. The introduction of a bifunctional organic ligand to the suspension mixture of these nanocrystals allows for their conjugation. The resulting Förster resonance energy transfer leads to quenching of Ga2O3 emission and an increase in the emission of CdSe/CdS quantum dots. As the ratio of CdSe/CdS quantum dots to Ga2O3 nanocrystals increases, so does the quenching of Ga2O3 emission and the CdSe/CdS photoluminescence intensity. The increase in quenching of Ga2O3 emission was successfully modelled assuming a Poisson distribution of CdSe/CdS quantum dots bound to Ga2O3 nanocrystals. Owing to the good emission colour complementarity of these materials, white light was observed for optimal nanoconjugate composition. Next, we demonstrated that the same phenomenon can be achieved without the organic linker by a careful deposition of the colloidal mixture on the glass substrate to remove the empty space between nanocrystals. This approach enables a surface-mediated Förster resonance energy transfer that allows for a design of all-inorganic white light emitting phosphors. The resulting films were highly luminescent and were tuned to give CIE coordinates of 0.31, 0.28. Gallium oxide also has a long luminescence lifetime, compared to other nanoparticles with similar emission strengths, enabled by its donor-acceptor pair recombination. This phenomenon makes Ga2O3 nanocrystals a prime candidate for attempting to design persistent afterglow nanophosphors through doping nanocrystals with selected trivalent rare earth metals. These rare earth elements provide a mechanism for trapping excited free carriers because relaxation within these dopant ions is Laporte forbidden. As a result of doping Ga2O3 with Dy3+, the emission of Ga2O3 nanocrystals becomes significantly longer at room temperature. More interestingly, the temperature-dependent emission of Ga2O3 nanocrystals doped with Dy3+ for doping levels between 3 and 13 % increased between 50 K and 200 K, where typical semiconducting nanocrystals show strong quenching. We attribute this anomalous behavior to the carriers trapped in Dy3+ excited states, that are thermally reactivated and subsequently relax to Ga2O3 native traps states. This assignment was validated by a kinetic Monte Carlo simulation, which was in good agreement with experimental results. As the importance of luminescence materials, particularly persistent phosphors, increases it is imperative that undergraduate students in chemistry and materials science become familiar with their properties and fabrication. A new laboratory exercise encompassing the combustion synthesis, processing, and characterization of SrAl2O4:(Eu2+, Dy3+) has been adopted by NE 320L course in the Nanotechnology Engineering program at the University of Waterloo. In this laboratory, students produced crude strontium aluminate containing Eu3+ which was subsequently annealed under hydrogen gas, resulting in the red europium emission. This emission becomes green upon reduction of Eu3+ to Eu2+. Students performed XRD showing a dramatic increase in crystallinity after annealing, while their SEM measurements did not show a significant change in morphology. Mechanoluminescence was observed using a ballistic setup and found to show a linear dependence on the projectile velocity. In this thesis I demonstrated the extrinsic (external functionalization) and intrinsic (doping) manipulation of the electronic structure of gallium oxide nanocrystals. The obtained results allow for technological application of the resulting materials (e.g., to generate white light and extend afterglow emission), and provide a framework to enrich upper-year undergraduate curriculum in materials science and nanotechnology

Luminescência persistente de nanotubos, nanoarames e cápsulas de SrAl2O4:Ce(III), Dy, Eu para pessoas com deficiências: nano-emergência

Doutoramento em Ciência e Engenharia dos MateriaisEste estudo transversal está focado na propriedade de luminescência persistente do aluminato de estrôncio co-dopado com cério (III), disprósio (III) e európio (II), SrAl2O4:Ce3+, Dy3+, Eu2+, em sistemas de sinalização de áreas de risco e emergências para pessoas com deficiências. Na área da ciência e engenharia dos materiais, foram desenvolvidos novos materiais com características nanométricas, nanotubos, nanoarames e nanobastões luminescentes de SrAl2O4:Ce3+, Dy3+, Eu2+ para aplicações na área da reabilitação e acessibilidade de pessoas com deficiências. Os nanotubos foram obtidos a partir de micro- e nano-partículas precursoras sintetizadas por reacção do estado-sólido e tratamento térmico de recozedura (1273-1473 K). Os nanoarames e nanobastões foram preparados por moagem, sonificação e recozedura (373 K). Novas nanocápsulas de aluminatos luminescentes dopados com cério (III) e encapsulados com TiO2 foram criadas de modo a obter-se materiais multifuncionais, designadamente com acção fotocatalítica antimicrobiana, antibacteriana e resistência à água. Tais aluminatos podem ser amplamente aplicados como superfícies higiénicas, auto-limpantes, em biomateriais, no domínio de medicamentos antibióticos, na formulação de vacinas, e com ênfase à aplicação em cerâmicas fotoluminescentes. As metodologias de obtenção de tais nanoestruturas de aluminato de estrôncio dopado com cério (III) e do seu encapsulamento, desenvolvidas no âmbito desta tese, são aplicáveis a diversos aluminatos dopados com outros iões lantanídeos (Ln consiste em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Tm ou Lu) com a fórmula M(1-x-y)N2O4:Cex, Lny, onde M é Be, Mg, Ca, Sr ou Ba. Na área da oftalmologia, foi desenvolvido um equipamento médico para o diagnóstico de biofuncionalidade das células retinais fotoreceptoras, e como suporte à telemedicina oftalmológica. Este equipamento foi utilizado para realizar testes de visão cromática FM100HUE em fundo branco/preto para a personalização de materiais luminescentes. Os resultados demonstraram uma biofuncionalidade celular à visibilidade fotópica das cores em fundo preto superior no grupo de tratamento, composto por pessoas com retinopatia diabética (n=38), em comparação ao grupo de referência (n=38). Estes resultados sugerem a recomendação de materiais com fotoluminescência persistente (λem=485-555 nm), incluindo SrAl2O4:Ce3+, Dy3+, Eu2+, para o referido grupo de tratamento, em sinalização de emergência e em ambientes de baixa iluminação. Na área da arquitectura, foi proposta uma nova aplicação dos referidos nanomateriais luminescentes à base de SrAl2O4:Ce3+, Dy3+, Eu2+ em cerâmica de revestimento, tendo em vista a sua boa visibilidade e uso por pessoas com deficiências. Novos pavimentos, cerâmicos, fotoluminescentes, foram desenhados com propriedades multisensoriais (contraste táctil, sonoro e visual) e antimicrobianas, para pessoas portadoras de deficiências utilizarem, no escuro, com a prioridade de salvar vidas em emergências. Tais pisos, com relevos, podem ser combinados de modo a compor um sistema exclusivo de sinalização fotoluminescente multisensorial que possibilita a rápida evacuação mediante o uso de auxílios de mobilidade (e.g. bengala, cadeira de rodas, andadores, muletas). A solução integrada de tais inovações que potencializa a propriedade de luminescência persistente de SrAl2O4:Ce3+, Dy3+, Eu2+ de modo acessível para as pessoas com deficiências, pode contribuir para salvar vidas, no escuro, em emergências.This transversal study is focused on the persistent luminescence property of the strontium aluminate co-doped with cerium (III), dysprosium (III) and europium (II), SrAl2O4:Ce3+, Dy3+, Eu2+, in signalling systems of risk areas and emergencies for people with disabilities. In the area of materials science and engineering, new nanostructured luminescent materials were developed, SrAl2O4:Ce3+, Dy3+, Eu2+ nanotubes, nanowires and nanorods, for applications in rehabilitation and accessibility for people with disabilities. The nanotubes were obtained from precursor micro- and nano-particles as-synthesized by solid-state reaction and under thermal treatment of post-annealing (1273-1473 K). The nanowires and nanorods were prepared by grinding, sonification and post-annealing (373 K). New luminescent core-shells of strontium aluminate doped with cerium (III) and encapsulated with TiO2 were created in order to obtain multifunctional materials, especially with photocatalytic activity, antimicrobial, antibacterial and water resistance. Such aluminates can be widely applied as hygiene surface, self-cleaning, in biomaterials, in the field of antibiotic drugs, in the formulation of vaccines, with emphasis on application in photoluminescent ceramics. The methods of obtaining such strontium aluminate nanostructures doped with cerium (III) and its encapsulation process developed in this thesis are applicable to various aluminates doped with other lanthanide ions (Ln is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Tm or Lu) with the formula M(1-x-y)N2O4:Cex, Lny, where M is Be, Mg, Ca, Sr or Ba. In the field of ophthalmology, medical equipment was developed for the diagnosis of biofunctionality of retinal photoreceptor cells, and for to support the ophthalmic telemedicine. This equipment was used for testing colour vision FM100HUE in white/black backgrounds for personalization of luminescent materials. The results showed a superior cellular biofunctionality to the photopic visibility of colours on a black background in treatment trials with diabetic retinopathy (n=38) than compared with references subjects (n=38). These results suggest the recommendation of persistent luminescent materials (λem=485-555 nm), including SrAl2O4:Ce3+, Dy3+, Eu2+, specifically to the said people with diabetes, in emergency signalling and for a better life quality in low lighting environments. In the field of architecture, we proposed a new application of these SrAl2O4:Ce3+, Dy3+, Eu2+ based-nanomaterials in ceramic tiles, in view to the superior persistent luminescence visibility and use by disable persons. New floors, photoluminescent-warning ceramic tiles were designed with multi-sensory (tactile, sonorous and visual contrast) and antimicrobial properties, for people with disabilities use them in the dark, with the priority of saving lives in emergencies. Such floors, with reliefs, can be combined to compose a unique multisensory photoluminescent signalization that enables a rapid evacuation through the use of mobility aids (e.g. canes, wheelchairs, walkers, crutches). The integrated solution of such innovations that enhances the persistent luminescence property of SrAl2O4:Ce3+, Dy3+, Eu2+ accessible for people with disabilities, can help save lives in the dark in an emergency.Cette étude transversale se concentre sur des propriété de luminescence persistante liées à l’aluminate de strontium dopé par cerium (III), dysprosium (III) et europium (II), SrAl2O4:Ce3+, Dy3+, Eu2+, dans les systèmes de signalisation des zones de risques ou d'urgences pour les personnes handicapées. Dans le domaine de la science et ingénierie des matériaux, a développé de nouveaux matériaux luminescents à l'échelle nanométrique, SrAl2O4:Ce3+, Dy3+, Eu2+ nanotubes, nanofils et nanotiges, pour les applications dans la réhabilitation et l'accessibilité des personnes handicapées. Les nanotubes ont été obtenus à partir de micro- et nano-particules précurseurs par synthèse à l'état solide suivie d’un de traitement thermique de post-recuisson (1273-1473 K). Les nanofils et nanotiges ont été préparés par broyage, traitement aux ultrasons et post-recuits (373 K). Les capsules luminescents originalles, basées sur les aluminates dopés au cérium (III) et encapsulés avec le TiO2, ont été créés afin d'obtenir des matériaux multifonctionnels avec une activité photocatalytique, y compris les antimicrobiens, antibactériens et des propriétés de résistance à l'eau. Ces aluminates peuvent être largement appliqués en tant que surface d'hygiène, d'auto-nettoyage, dans les biomatériaux, dans le domaine des antibiotiques, dans la formulation des vaccins, en mettant l'accent sur l'application de la céramique photoluminescent. Les méthodes pour obtenir ces nanostructures à l’aluminate de strontium dopé au cérium (III) et de son encapsulation, développé dans cette thèse, sont applicables aux différents aluminates dopées avec d'autres ions lanthanides (Ln est La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Tm ou Lu) avec la formule M(1-x-y)N2O4:Cex, Lny,, où M est Be, Mg, Ca, Sr ou Ba. Dans le domaine de l'ophtalmologie, un équipement médical été développé pour le diagnostic de biofunctionalité des cellules photoréceptrices de la rétine et le soutient de la télémédecine en ophtalmologie. Ce équipement été utilisé pour tester la vision des couleurs FM100HUE en blanc/noir fond pour le personnalisation de matériaux luminescents. Les résultats montrent une biofunctionalité cellulaire supérieure à la visibilité photopique de couleurs sur un fond noir chez les traitement groupe de personnes atteintes de rétinopathie diabétique (n=38) que par rapport aux sujets de référence (n=38). Ces résultats suggèrent la recommandation de matériaux photoluminescents (λem= 485-555 nm), y compris SrAl2O4:Ce3+, Dy3+, Eu2+, à ces traitement personnes atteintes de diabète, dans la signalisation d'urgence et pour une meilleure qualité de vie dans l'éclairage faible. Dans le domaine de l'architecture, nous avons proposé une nouvelle application de ces nanomatériaux luminescents basée sur SrAl2O4:Ce3+, Dy3+, Eu2+, en carreaux céramiques, en vue de la bonne visibilité pour les personnes ayant déficiences visuelles. Nouveaux pavements, céramiques, photoluminescents, ont été conçus avec des propriétés multi-sensorielle et antimicrobiennes, dans des conditions d’obscurité pour les personnes handicapées, et dans le but de sauver des vies dans les situations graves d'urgence. Ces pavements, en reliefs, peuvent être combinés pour composer un signal unique photoluminescent multisensoriel qui permet une évacuation rapide grâce à l'utilisation des aides à la mobilité (par exemple, cannes, fauteuils roulants, des déambulateurs). La solution intégrée de ces innovations améliorent la propriété de luminescence persistante de SrAl2O4:Ce3+, Dy3+, Eu2+ nanomatériaux accessible aux personnes handicapées et peut aider à sauver des vies, dans l'obscurité, dans une situation d'urgence.MCTESBDUA | RECTORY | f2698 | 2006-2010INR - National Institute for RehabilitationPrémio Maria Cândida da Cunha 2009MTS

Synthesis and luminescence investigations of Europium (Eu3+) and Samarium (Sm3+ ) doped sodium alkaline-earth sulphate phosphors (Na6Mg(SO4)4 and Na2Ca(SO4)2 ) via combustion method

Abstract: The rapid change in technological influence have seen sodium mixed sulphate phosphors made way in the new development of optoelectronics. Na6Mg(SO4)4 and Na2Ca(SO4)2 nanophosphors were synthesized using chemical combustion method at a temperature of 5800C, with a single dope concentration of (1.0mol%) of Sm3+ and Eu3+. These nanophosphors were co-doped with Na6Mg(SO4)4: Sm3+(1.0mol)/xEu3+ (where x= 0.5mol%, 1mol% and 1.5mol%) and Na2Ca(SO4)2:Sm3+(1.0mol%)/xEu3+(where x= 0.5mol% - 1.5mol%). The structural, morphological and optical properties of prepared nanophosphors were studied using X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) techniques. The XRD results confirmed that the crystal structure of both compounds exhibited diffraction peaks of a monoclinic phase with different space groupings. The surface morphological studies showed that the addition of impurities into both Na6Mg(SO4)4 and Na2Ca(SO4)2 phosphors can have an impact on the variation of particle sizes and shapes through their agglomeration effect. The luminescence properties were studied using the DRS spectra measured from 250 nm -2250 nm. To investigate photoluminescence (PL) features of Sm3+ and Eu3+ ions, all series of Na6Mg(SO4)4 and Na2Ca(SO4)2 nanophosphors were excited with 404 nm and 395 nm wavelengths respectively. An improved colour tenability was witnessed in Na6Mg(SO4)4 nanophosphor series and supported by results of the lifetime decay curve and energy transfer mechanism from Sm3+ to Eu3+. The CIE color images were found to be the tuning of pure red color emission for increasing of Eu3+ ion concentration in both Na6Mg(SO4)4 and Na2Ca(SO4)2 nanophosphors. The results of this study show that Sm3+ and Eu3+ co-doped Na6Mg(SO4)4 and Na2Ca(SO4)2 materials are potential candidates for efficient orange and red emitting luminescent phosphors for application in white LEDs.M.Sc. (Nanoscience

Structural, optical and magnetic properties of samarium doped zinc phosphate glasses embedded with nickel nanoparticles

Two series of 40ZnO-(60-x)P2O5-xSm2O3 and 40ZnO-(59-y)P2O5-Sm2O3- yNiO glasses are prepared by melt-quenching technique with 1.0 = x = 4.0 mol% and 0.5 = y = 2.0 mol% respectively. The glass is characterized by X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM), High Resolution Transmission Electron Microscope (HRTEM), Fourier Transform Infrared (FTIR) spectrometer, Raman spectrometer, UV-Vis NIR spectrophotometer, Photoluminescence (PL) spectrometer, Vibrating Sample Magnetometer (VSM) and Electron Spin Resonance (ESR) spectrometer. The XRD pattern confirms the amorphous nature of the glass and the TEM image reveals the existence of nickel nanoparticles (Ni NPs) with average size ~8 nm. Meanwhile, HRTEM reveals the lattice spacing of face centered cubic (FCC) structure of nickel is 0.35 nm at (100) plane. Four major IR absorption peaks are found to be at 723 cm-1, 916 cm-1, 1081 cm-1 and 1280 cm-1 corresponding to stretching vibration of symmetric (P-O-P), asymmetric (P-O-P), asymmetric (P-O-) and asymmetric (P=O) respectively. Raman spectra display two significant peaks at 708 cm-1 and 1201 cm-1 attributed to the symmetric and asymmetric stretching vibrations of P-O-P, respectively. The Raman intensities for both peaks exhibit a rapid decrease with the increase of Ni NPs concentration. The absorption spectra of samarium ions consist of five bands attributed to absorption from the ground state 6H5/2 to the excited states 6F1/2, 6F3/2, 4F5/2, 4F7/2 and 6F9/2. The surface plasmon resonance (SPR) peaks of Ni NPs are detected at 433 nm and 475 nm. Photoluminescence emission exhibits four peaks corresponding to 4G5/2 - 6H5/2, 6H7/2, 6H9/2, and 6H11/2 transitions. It is observed that all peaks experience significant quenching effect with increasing concentration of Ni NPs, suggesting that there is a strong energy transfer from excited samarium ions to the nickel ions. The glass magnetization and susceptibility in magnetic field up to 12 kOe at room temperature is found to be in the range of (0.11-2.02) x10-2 emu/g and (0.09-1.68) x10-6 emu/Oeg respectively. The obtained hysteresis curve and g-factor value of 1.99 to 2.34 indicate that the glass samples are superparamagnetic. It is concluded that samarium doped zinc phosphate glass embedded with nickel nanoparticles could be useful for magneto-optical and solid state devices

Persistent Phosphors for Smartphone-Based Luminescence Thermometry and Anti-Counterfeiting Applications

Leuchtstoffe anhaltender Lumineszenz im sichtbaren Spektrum eröffnen neue Möglichkeiten für Smartphone-basierte Anwendungen. Videoaufnahmen mit dem Smartphone mit 30 Bildern pro Sekunde können persistente Lumineszenzlebenszeiten einer Größenordnung von 100 ms und länger bestimmen. Die mit dem Smartphone aufgezeichneten Daten können benutzt werden um Anwendungen zu realisieren, die ansonsten nur für kurze Lebenszeiten möglich sind. Diese Alternative umgeht den Bedarf an teuren und relativ komplizierten Messinstrumenten, die für die Detektion von kurzen Lebenszeiten eingesetzt werden, wie zum Beispiel Multichannel scaling, Hochgeschwindigkeitskameras und Mikroskope zur Messung der Fluoreszenzlebenszeit. Diese Arbeit konzentriert sich auf die Detektion anhaltender Lumineszenz für Temperaturmessung und Anwendungen zur Fälschungssicherung mit dem Smartphone. Für die Smartphone-basierte Temperaturmessung wurde ein optimierter Gd2O2S: Eu3+ als Leuchtstoff verwendet, der mithilfe einer UV-Quelle angeregt werden kann. Der Leuchtstoff zeigte eine temperaturabhängige Lumineszenz, die hell und lange anhaltend genug war, um mit einer Smartphone-Kamera mit 30 Bildern pro Sekunde aufgezeichnet zu werden. Der Leuchtstoff hat eine Photolumineszenz-Quantenausbeute von 65 % und seine Lebenszeit nimmt mit steigender Temperatur ab. Dies wurde beobachtet über einen Temperaturbereich von 270 K bis 338 K, in dem die Lebenszeit von 1107 ms bis auf 100 ms abfiel. Die Analyse der zeitintegrierten Emission mit dem Smartphone nach einer Anregung mit 375 nm zeigte, dass die Temperaturen im Bereich von 270 K bis 338 K präzise gemessen werden konnten mit einer Messungenauigkeit unter 2 K. Darüber hinaus wurde die Lebenszeitmessung nicht durch Hintergrundstrahlung beeinträchtigt und ermöglichte somit eine genaue Temperaturmessung auch bei einer Hintergrundbeleuchtungsstärke von bis zu 1500 lx. Um eine Smartphone-basierte Fälschungssicherung zu realisieren wurden anhaltende Leuchtstoffe mit einstellbarer Lebenszeit bei Raumtemperatur benutzt, um dynamische, lumineszierende Etiketten zu entwickeln. Dynamische Fälschungssicherung wurde mithilfe von Ti4+-dotierten Gd2O2S: Eu3+ realisiert, wobei die Ti4+-Dotierung eine Kontrolle der Lebenszeit bei Raumtemperatur ermöglicht. Durch eine Veränderung der Kodotierung von 0 bis 0.09 mol% konnte die Lebenszeit von 1.17 ± 0.02 bis 5.95 ± 0.07 s durchgestimmt werden mit einer Anregung bei 375 nm. Durch eine Kombination von Leuchtstoffen mit verschiedenen Lebenszeiten konnten somit dynamische Etiketten zur Fälschungssicherung entwickelt werden. Die Lebenszeit der Leuchtstoffe für diese dynamischen Muster bestimmte dabei die Komplexität der Fälschungssicherung. Solche Muster, die aus einer Kombination von Leuchtstoffen mit großen Unterschieden in der Lumineszenzlebenszeit entwickelt wurden, konnten mit bloßem Auge beobachtet werden. Im Gegensatz dazu sind zeitliche Änderungen in Etiketten mit viel kürzerer Lebenszeit im Bereich von 0.2 s nur schwer mit bloßem Auge nachzuvollziehen. Mithilfe der Smartphone-Kamera mit einer Aufzeichnungsrate von 30 Bildern pro Sekunde können die versteckten Merkmale jedoch leicht entschlüsselt werden. In Hinblick auf die tatsächliche Anwendung am Verkaufsort, ist eine UV-Quelle einerseits normalerweise nicht vorhanden in einem Smartphone und andererseits stellt der Einsatz von UV-Strahlung für die Anregung der Leuchtstoffe eine Gesundheitsrisiko dar. Um die Nutzung einer UV-Quelle gänzlich zu vermeiden, wurden zweifarbige dynamische Etiketten zur Fälschungssicherung entwickelt. Diese erlauben eine Anregung mithilfe eines herkömmlichen Smartphone-Blitzlichtes während die Emission einfach mit der Kamera aufgezeichnet werden kann. Zu diesem Zweck wurden grün emittierende (SrAl2O4: Eu2+, Dy3+ (SAED)) und rot emittierende (CaS: Eu2+ und SrS: Eu2+) Leuchtstoffe entwickelt. Die Lebenszeit von SAED konnte variiert werden von 0.5 s bis 11.7 s durch Glühen des kommerziell erhältlichen Stoffes, was eine Verringerung der Störstellendichte im Material zur Folge hat. Die Lumineszenzlebenszeit von CaS: Eu2+ und SrS: Eu2+ konnte dagegen zwischen 0.1 bis 0.6 s und 150 bis 377 ms eingestellt werden mithilfe der Eu2+-Dotierdichte. Die Nutzung eines Smartphones ermöglicht nicht nur lebenszeit-basierte Temperaturmessungen ohne teure Messinstrumente, sondern eröffnet darüber hinaus eine kostengünstige Methode zur Authentifizierung von lumineszenzbasierten, dynamischen Markierungen zur Fälschungssicherung

Environmental Technologies to Treat Rare Earth Element Pollution

Rare earth elements (REE) have applications in various modern technologies, e.g., semiconductors, mobile phones, magnets. They are categorized as critical raw materials due to their strategic importance in economies and high risks associated with their supply chain. Therefore, more sustainable practices for efficient extraction and recovery of REE from secondary sources are being developed. This book, Environmental Technologies to Treat Rare Earth Elements Pollution: Principles and Engineering: presents the fundamentals of the (bio)geochemical cycles of rare earth elements and which imbalances in these cycles result in pollution. overviews physical, chemical and biological technologies for successful treatment of water, air, soils and sediments contaminated with different rare earth elements. explores the recovery of value-added products from waste streams laden with rare earth elements, including nanoparticles and quantum dots. This book is suited for teaching and research purposes as well as professional reference for those working on rare earth elements. In addition, the information provided in this book is helpful to scientists, researchers and practitioners in related fields, such as those working on metal/metalloid microbe interaction and sustainable green approaches for resource recovery from wastes

Environmental Technologies to Treat Rare Earth Element Pollution

Rare earth elements (REE) have applications in various modern technologies, e.g., semiconductors, mobile phones, magnets. They are categorized as critical raw materials due to their strategic importance in economies and high risks associated with their supply chain. Therefore, more sustainable practices for efficient extraction and recovery of REE from secondary sources are being developed. This book, Environmental Technologies to Treat Rare Earth Elements Pollution: Principles and Engineering: presents the fundamentals of the (bio)geochemical cycles of rare earth elements and which imbalances in these cycles result in pollution. overviews physical, chemical and biological technologies for successful treatment of water, air, soils and sediments contaminated with different rare earth elements. explores the recovery of value-added products from waste streams laden with rare earth elements, including nanoparticles and quantum dots. This book is suited for teaching and research purposes as well as professional reference for those working on rare earth elements. In addition, the information provided in this book is helpful to scientists, researchers and practitioners in related fields, such as those working on metal/metalloid microbe interaction and sustainable green approaches for resource recovery from wastes

5th International Conference on Nanomaterials Science and Mechanical Engineering

No abstract available.publishe