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Nonlinear luminescence quenching has been documented in numerous systems such as organic crystals, rare earth insulators, laser materials, semiconductors, and phosphors. In each of these systems nonlinear luminescence quenching occurs under conditions of high excitation density from interactions between excited centers, the result is an additional nonradiative decay pathway that lowers luminescence quantum efficiency. During investigations into the spectra and dynamics of Eu2O3, an apparent saturation dip in the excitation spectra of nano-sized Eu2O3 particles was observed. This thesis describes the investigation into the nature of the saturation effect. The samples studied using luminescent spectroscopy included micron sized Eu2O3 crystals of both cubic and monoclinic phases, nanocrystal monoclinic Eu2O3, and a large fused crystal of monoclinic Eu2O3. It was determined that the saturation effect was due to nonlinear luminescence quenching occurring at the wavelengths of absorption maxima. The mechanism of nonlinear luminescence quenching was concluded to be upconversion by energy transfer. / Master of Science

Die Mechanismen von Immobilisierungsprozessen radioaktiver Schwermetall-Ionen innerhalb von Biofilmen sind noch weitgehend unerforscht. Das liegt an der Komplexität der Biofilme, welche häufig diskrete geochemische Mikromilieus bilden, die sich vom umgebenden Milieu („Bulk Solution“) in Bezug auf dessen Biozönose (der mikrobiellen Diversität), den darin herrschenden geochemischen Bedingung (z.B. Red/Ox-Potential u./o. gelöster Sauerstoffmenge), aber auch in der Konzentration möglicher Komplexbildner (z.B. Metaboliten u./o. EPS-Komponenten) deutlich unterscheiden. Alle diese Faktoren können die Speziation der Radionuklide verändern und damit auch deren Transportverhalten. Für ein besseres Prozessverständnis zu den Wechselwirkungen von Radionukliden mit natürlichen, in Uran-kontaminierten Milieus lebende Mikroorganismen und den damit verbunden Stoffen wurde die Biozönose in Biofilmen und im Grubenwasser des ehem. WISMUT-Uranbergwerkes Königstein nach klassischen mikrobiologischen- und molekularbiologischen Methoden bestimmt. Aus einem Vergleich der Chemie im Biofilm mit der Chemie der umgebenden Lösung wird der Einfluss der Biofilme auf das Migrationsverhalten von Radionukliden in der Natur beurteilt. Die Identifizierung und Quantifizierung von Prokaryoten erfolgte u.a. mit der CARD FISH Methode. Die selektive Visualisierung der EPS-Komponenten in der Matrix der Biofilme wurde mit Hilfe der Konfokalen Laser Scanning Mikroskopie (CLSM) bewerkstelligt. Zur Untersuchung der Speziation von fluoreszierenden Schwermetall-Ionen wie U(VI) kam die zeitaufgelöste, laser-induzierte Fluoreszenzspektroskopie (TRLFS) zum Einsatz. Um diese Methode auch im mikroskopischen Bereich anwenden zu können, wurde sie weiter zum CLSM hin entwickelt: Da ein 80-MHz-MaiTai-Laser zur Verfügung stand, wurde durch im kHz-Bereich alternierendes Beugen des Anregungslaserstrahls von der Probe weg (und wieder zu ihr hin) mittels akusto-optischem Modulator (AOM) eine quasi-gepulste Laseranregung im kHz-Bereich erreicht. Durch Einbindung von Frequenzvervielfachern („Harmonixx“ von APE Berlin und „Inspire“ von Spectra-Physics) konnte so eine gepulste Anregung innerhalb eines breiten Wellenlängenbereiches (ca. 230-1090 nm) ermöglicht werden. Für die Auswertung des als äußerst schwach zu erwartenden Fluoreszenzsignales (entsprechend des mikroskopisch kleinen Anregungsraumes) wurde die Time-Correlated Single-Photon Counting Methode (TCSPC) – auch „zeitbezügliche Einzelphotonenzählungs-Methode“ – an das Laser-Anregungssystem angepasst. Die Fluoreszenzlebenszeitkurve des Fluoreszenzsignals von U(VI) Species, die sich an der Oberfläche von den Protozoen Euglena Mutabilis befanden, konnte z.B. auf diese Art mit Hilfe der TCSPC ermittelt werden.

Les matériaux émetteurs et les lasers solides sont largement employés dans le domaine de l’optique et des sciences des matériaux en tant que sources d’excitation, pour des mesures expérimentales, des applications médicales, de la mise en forme ou de la découpe de métaux…Récemment des valeurs d’efficacité laser prometteuses ont été obtenues à partir de céramiques transparentes qui résultent de procédés de mises en forme plus rapides et moins couteux de matériaux à l’état cristallisé.Les travaux de recherche proposés sont centrés sur une matrice cubique dopée par des ions Eu3+ de formule Y3NbO7. Les voies de synthèse sont optimisées pour obtenir une phase pure présentant des grains homogènes en taille et de morphologie sphérique. Les paramètres SPS tels que la montée en température, la température et la durée de frittage ainsi que la pression sont ajustés pour favoriser la densification des pastilles.La spectroscopie de luminescence des ions europium trivalents est employée pour optimiser les paramètres étudiés. Les émissions enregistrées couplées à la diffraction des rayons X et à la microscopie électronique en transmission soulignent l’existence de plusieurs environnements distordus autour des ions dopants dans le réseau de type fluorine lacunaire. La cristallisation rapide obtenue par SPS, couplée à la nature du niobate de terre rare, conducteur ionique, conduit à une démixtion de la solution solide de Y3NbO7 en deux fluorines distinctes. La composition finale de la pastille est conditionnée par le ratio cationique Nb/Y. / Emitting materials and all solid state lasers are widely used in the field of optical applications and materials science as a source of excitement, instrumental measurements, medical applications, metal shaping…Recently promising laser efficiencies were recorded on transparent ceramics which results from a cheaper and faster ways to obtain crystallized materials.This investigation is focused on the cubic Eu3+ doped Y3NbO7 matrix. The synthesis route is optimized in order to obtain a pure phase which presents a homogeneous morphology of spherical grains. Several SPS parameters as heating rate, temperature, duration time and pressure are adjusted in order to increase the densification of the pellets. Luminescence spectroscopy of trivalent europium ions is used to optimize these parameters. The emission data coupled with X-Ray diffraction analysis and electronic diffraction microscopy highlight the existence of several distorted environments of the doping element in the defective fluorite type Y3NbO7 host lattice. Indeed, the fast and high crystallization rate obtained after SPS coupled with the ionic conductivity of the matrix make possible a phase composition splitting into two fluorites. The final composition of the pellet is driven by the ratio between niobium and yttrium elements.

Europium complex is a promising candidate for organic electroluminescent (EL) material due to its sharp emission band. Several diketone ligands bearing different substituents (substituents¡×CH3, Ph, CF3, thiophene) as well as phenanthroline and its derivatives (substituents¡×CH3, Ph, NO2) were used to synthesize our target series of Europium complexes. The complexes were identified by means of NMR, EA, MS, and single-crystal X-ray analysis. We report here the structural influence on photoluminescence (PL), UV-Vis and thermal properties of these Eu complexes. Within the series, Eu(TTFA)3(Bath) showed the highest fluorescence in THF solution. A efficient red electroluminescence (sharp emission at 616 nm) was obtained in the organic electroluminescent device using Eu(TTFA)3(Bath) doped into CBP. The external quantum efficiency and maximum luminance of the device were 1.022¢M and 1295 cd/m2, respectively.

Thesis (M.S.) -- Univeristy of Tennesse. / At head of title: Metallurgy Division. "Date issued: Sep. 12, 1960." Bibliography: p. 83.

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Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-05-25T12:57:10Z No. of bitstreams: 1 Glauco herbert.pdf: 2350916 bytes, checksum: 4bca93071e5f53c3cb946ca7f27ab0e6 (MD5) / Made available in DSpace on 2017-05-25T12:57:10Z (GMT). No. of bitstreams: 1 Glauco herbert.pdf: 2350916 bytes, checksum: 4bca93071e5f53c3cb946ca7f27ab0e6 (MD5) Previous issue date: 2015-06-03 / CAPES, FAPEMA,CNPQ e FINEP / Calcium Boroaluminate (CaBAl) glass is an important family of optical materials, which has been studied due to the good combination of chemical, thermal, mechanical, optical and spectroscopic properties. In this work Eu2O3 doped CaBAl glasses were prepared and thermal, structural, optical and spectroscopic properties were discussed in terms of rare earth content. Results of density, glass transition temperature, crystallization temperature, specific heat, refractive index, optical absorption coefficient, luminescence and lifetime measures were analyzed. Molar volume, thermal conductivity, electronic polarizability, ion concentration per cubic centimeter and interionic distance were calculated. X-ray diffraction, Raman and FT-IR were also carried out to obtain structural information of these glasses. The results show that europium doping, when replacing CaO, induced changes in various properties of the glass studied. The X-ray data showed the amorphous nature of all samples. Raman and FT-IR data confirmed the structural change, which showed that Eu2O3 addition cause the simultaneous increase in the bands corresponding to the presence of structural units of the type BO3, BO4 and non-bridging oxygens (NBO). The thermal and structural results shows that the incorporation of Eu2O3 lead to an increase in density, glass transition temperature, decrease in crystallization onset temperature and a consequent reduction in the thermal stability of the glass. The glass doping didn’t affect significantly the specific heat and the thermal conductivity, within the errors. The results of refractive index show an increase with Eu2O3 content. The absorption spectrum of glass matrix shows that it is transparent from 370nm to 2400nm. The absorption coefficient at 394nm showed a linear increase with the Eu2O3 concentration. The luminescence results indicate two emission bands centered at 614nm and 700nm. The emission intensity for these peaks increase with dopant concentration and no luminescence quenching was observed for the studied compositions. The emission lifetime results at 614nm shows a exponential decrease with doping concentration due to, probably, ion-ion interaction . The data analysis shows that the europium acts as network modifier. The results show that glasses studied in this work have a good combination of properties, making these glasses, potential candidate for use in photonic devices. / O vidro Cálcio Boroaluminato (CaBAl) faz parte de uma importante família de materiais ópticos que apresenta boas propriedades químicas, térmicas, mecânicas, ópticas e espectroscópicas. Neste trabalho foram realizados estudos em vidros CaBAl, dopados com óxido de európio. Foram caracterizadas propriedades térmicas, estruturais, ópticas e espectroscópicas em função da concentração de európio. Analisou-se resultados de medidas de densidade, temperaturas de transição vítrea, início de cristalização, calor específico, índice de refração, coeficiente de absorção óptica, luminescência e tempo de vida. Também calculou-se volume molar, condutividade térmica, polarizabilidade eletrônica, concentração de íons por centímetro cúbico e distancia interiônica. Foram realizados ainda estudos de difração de Raios-X, espalhamento Raman e FT-IR para obter informações estruturais destes vidros. Os resultados mostram que a incorporação do dopante na base promoveu mudanças em diversas propriedades do vidro estudado. Os dados de Raios-X comprovaram a característica amorfa das amostras. Os dados de Raman e FT-IR confirmam a modificação estrutural e mostraram que, com o aumento na concentração de dopante, há um aumento simultâneo nas bandas correspondentes à presença de unidades estruturais do tipo BO3, BO4 e oxigênios não ligados (NBO). O estudo dos resultados térmicos e estruturais mostrou que incorporação de Eu2O3 provocou um aumento na densidade, aumento na temperatura de transição vítrea, redução na temperatura de início de cristalização e consequente redução na estabilidade térmica do vidro. O calor específico do material não apresentou diferenças significativas para as amostras dopadas com até 10% em peso, dentro da margem de erro experimental. A inclusão de dopante também foi responsável por um aumento linear no índice de refração das amostras. Os dados de absorção mostram que a base apresenta uma boa janela de transparência, que vai de aproximadamente 370nm até 2400nm. As amostras dopadas apresentaram bandas de absorção no UV características do Eu2O3 e o coeficiente de absorção, em 394nm, apresentou um aumento praticamente linear com a concentração de Eu2O3. As medidas de luminescência indicam duas bandas de emissão, centradas em 614nm e 700nm. Os picos de emissão aumentam com a concentração de dopante, indicando ausência de quenching na luminescência para as composições estudadas. As medidas do tempo de vida foram realizadas para a emissão em 614nm e apresentam uma redução exponencial com a concentração de dopante, devido provavelmente a interações íon-íon. A análise dos dados mostra que, como visto em outros trabalhos, o európio atua também como modificador de rede. Os resultados mostram que os vidros estudados neste trabalho apresentam uma boa combinação de propriedades, o que faz destes vidros potenciais candidatos para uso em dispositivos fotônicos.

The N=88 isotones lie on the onset of nuclear deformation and have a complicated nuclear structure. To better understand this region, the nuclear levels of ��������Sm were studied in three different �� decay experiments. De-populating ��-rays were measured using the 8�� spectrometer, an array of 20 Compton suppressed Ge detectors. Levels of ��������Sm were populated in varying degrees by three radioactive sources: ��������Pm (J=1���, Q=3454 keV), ��������[superscript m]Eu (J=0���, Q=2303 keV), and ��������[superscipt g]Eu (J=5���, Q=2261 keV), which were all produced at the 88" cyclotron located at LBNL. Among several changes to the existing level structure were the addition of a 0��� level identified at 1603.24 keV, as well as confirming another questioned 0��� assignment of the 1786.47 keV level. Angular correlation analysis was carried out on many different transitions, allowing for spin assignments and the determination of mixing ratios. The results from these three experiments provide extensive new data, and give a fairly complete picture of nuclear levels below about 2 MeV and J���6. The theoretical interpretation of this particular nucleus is still open to question. The data from these experiments, used in conjunction with other studies of nuclei in this same mass region (which are currently underway), may provide further insight into this transition region. / Graduation date: 2003

Reproduction de : Thèse de doctorat : Chimie moléculaire : Toulouse 3 : 2007. / Titre provenant de l'écran-titre. Bibliogr. à la fin des chapitres.