Call number: LD2668 .T4 1956 B87 / Master of Science

Call number: LD2668 .T4 1958 W45

The emerging field of nanotechnology, which spans diverse areas such as nanoelectronics, medicine, chemical and pharmaceutical industries, biotechnology and computation, focuses on the development of devices whose improved performance is based on the utilization of self-assembled nanoscale components exhibiting unique properties owing to their miniaturized dimensions. The first phase in the conception of such multifunctional devices based on integrated technologies requires the study of basic principles behind the functional mechanism of nanoscale components, which could originate from individual nanoobjects or result as a collective behaviour of miniaturized unit structures. The comprehensive studies presented in this thesis encompass the mechanical, dynamical and photophysical aspects of three nanoscale systems. A newly developed europium sulfide nanocrystalline material is introduced. Advances in synthetic methods allowed for shape control of surface-functionalized EuS nanocrystals and the fabrication of multifunctional EuS-CdSe hybrid particles, whose unique structural and optical properties hold promise as useful attributes of integrated materials in developing technologies. A comprehensive study based on a new class of multifunctional nanomaterials, derived from the basic unit of barcoded metal nanorods is presented. Their chemical composition affords them the ability to undergo autonomous motion in the presence of a suitable fuel. The nature of their chemically powered self-propulsion locomotion was investigated, and plausible mechanisms for various motility modes were presented. Furthermore functionalization of striped metallic nanorods has been realized through the incorporation of chemically controlled flexible hinges displaying bendable properties. The structural aspect of the light harvesting machinery of a photosynthetic cryptophyte alga, Rhodomonas CS24, and the mobility of the antenna protein, PE545, in vivo were investigated. Information obtained through a combination of steady-state and time-resolved spectroscopy in conjunction with quantum chemical calculations aided in the elucidation of the dynamics and the mechanism of light harvesting in the multichromophoric phycobiliprotein phycocyanin PC645 in vitro. Investigation of the light-harvesting efficiency and optimization of energy transfer with respect to the structural organization of light-harvesting chromophores on the nanoscale, can provide us with fundamental information necessary for the development of synthetic light-harvesting devices capable of mimicking the efficiency of the natural system.

Rare earth ion doped glasses find applications in optical and photonic devices such as optical windows, laser, and optical amplifiers, and as model systems for immobilization of nuclear waste. Macroscopic properties of these materials, such as luminescence efficiency and phase stability, depend strongly on the atomic structure of these glasses. In this thesis, I have studied the atomic level structure of rare earth doped silicate and aluminophosphate glasses by using molecular dynamics simulations. Extensive comparisons with experimental diffraction and NMR data were made to validate the structure models. Insights on the local environments of rare earth ions and their clustering behaviors and their dependence on glass compositions have been obtained. In this thesis, MD simulations have been used to investigate the structure of Eu2O3-doped silica and sodium silicate glasses to understand the glass composition effect on the rare earth ions local environment and their clustering behaviors in the glass matrix, for compositions with low rare earth oxide concentration (~1mol%). It was found that Eu–O distances and coordination numbers were different in silica (2.19-2.22 Å and 4.6-4.8) from those in sodium silicate (2.32 Å and 5.8). High tendencies of Eu clustering and short Eu-Eu distances in the range 3.40-3.90 Å were observed in pure silica glasses as compared to those of silicate glasses with much better dispersed Eu3+ ions and lower probability to form clusters. The results show Eu3+ clustering behavior dependence on the system size and suggest for low doping levels, over 12,000 atoms to obtain statistical meaningful results on the local environment and clustering for rigid silica-based glasses. The structures of four cerium aluminophosphate glasses have also been studied using MD simulations for systems of about 13,000 atoms to investigate aluminum and cerium ion environment and their distribution. P5+ and Al3+ local structures were found stable while those of Ce3+ and Ce4+ ions, through their coordination numbers and bond lengths, are glass composition-dependence. Cerium clusters were found in the high cerium glasses.P5+ coordination numbers around cerium revealed the preference of phosphorus ions in the second coordination shell. Total structure factors from MD simulations and experimental diffraction results show a general agreement from comparison for all the cerium aluminophosphate glasses and with compositional changes up to 25 Å-1. Aluminum enters the phosphate glass network mainly as AlO4 and AlO5 polyhedra only connected through corner sharing to PO4 tetrahedra identified by Q11(1 AlOx), Q12(2 AlOx), Q21(1 AlOx), and Q22(2 AlOx) species.

New red emitting phosphors, based on the double tungstate/molybdates, were discovered. Some were able to retain their luminous efficacy after substituting Y3+ for Eu3+, reducing the cost of the phosphor. This substitution was attempted for existing commercial red emitting phosphors and proved unsuccessful. Another set of phosphors based on these lattices were discovered and the emitted luminous efficacy was 140% greater than other reported Eu3+ phosphors. The best of these was Na2WO4MoO4Eu0.44Al1.34Sm0.011. The integration of phosphors to the lighting application was also studied, including improvements in light extraction for existing phosphors. ACEL panels are currently applied to many applications and were briefly examined. The more recent OLED technology was investigated and comparisons can be drawn with the ACEL panels. LEDs were also a focus of the work with a new method developed for remote application of phosphors to LEDs, based on a dome shaped encapsulant, and this was adopted commercially by a high brightness LED manufacturer. The studies on the phosphors reported herein were aimed at integrating these into commercial applications. Although this was not achieved as brightness and particles size were problematic, if it is demonstrated that further development of the synthetic methods produce phosphors with suitable attributes, this may lead to the integration in applications.

Este trabalho apresenta as propriedades ópticas dos complexos Európio Tetraciclinas (EuTcs) na presença de LDL e de LDL oxidada com potenciais aplicações em análises clínicas. Foram escolhidos quatro elementos da família das Tetraciclinas: Tetraciclina (Tc), Clorotetraciclina (CTc), Metatetraciclina (MTc) e Oxitetraciclina (OTc) para fazerem parte dos complexos com o íon európio. As melhores condições para se formar os complexos eficientemente foram determinadas, através das medidas dos parâmetros ópticos como: absorção, emissão e de tempo de vida. As melhores concentrações de európio nos complexos EuTcs e possíveis influências de íons inorgânicos normalmente presentes no plasma sanguíneo também foram analisadas. As amostras foram preparadas em pH neutro e a luminescência visível do lantanídeo foi detectada após tempo de repouso das amostras de 15 minutos. Os resultados deste trabalho mostraram que as moléculas de LDL e de LDL oxidada apresentaram um importante papel no aumento da intensidade de emissão dos complexos das Tcs. As medidas realizadas com os complexos EuTcs não apresentaram deslocamentos nos comprimentos de onda dos espectros de absorção e de emissão na presença de LDL, o que demonstra a ausência de interação direta entre as moléculas de Tcs e as moléculas de LDL e LDL oxidada. No entanto, o íon európio pode interagir em diferentes sítios das moléculas de tetraciclinas o que diferenciou a intensidade de emissão de cada complexo. Comparando os resultados obtidos entre os complexos de EuTcs, o complexo EuTc foi o que apresentou perspectivas promissoras na quantificação de LDL e LDL oxidada. / This work presents the optical properties of europium complexes - Tetracyclines (EuTcs) in the presence of LDL and oxidized LDL with potential applications in clinical analysis. Four elements were chosen from the Tetracyclines family: Tetracycline (Tc), Chlortetracycline (CTc), Metatetraciclina (MTc) and Oxytetracycline (OTc) to be part of complexes with europium ion. The best conditions to form the complex efficiently were determined through measurements of optical parameters such as absorption, emission and lifetime. The best concentrations of europium complexes in EuTcs and possible influences of inorganic ions normally present in blood plasma were also analyzed. The samples were prepared at neutral pH and the visible luminescence of lanthanide was detected after resting time of the samples of 15 minutes. These results showed that the molecules of LDL and oxidized LDL have an important role in increase of the emission intensity for Tcs complexes . The measurements performed with the complex EuTcs showed no shifts in the wavelengths of the absorption and emission spectra in the presence of LDL, which demonstrates the absence of direct interaction between the molecules of Tcs and the molecules of LDL and oxidized LDL. However, the europium ion can interact at different sites of the tetracyclines molecules which differed the emission intensity of each complex. Comparing the results obtained between the complexes EuTcs, the complex EuTc is the one that presented the promising prospects in the quantification of LDL and oxidized LDL.

Nenhuma / Foi realizado neste trabalho o estudo da recuperação de európio e ítrio de monitores de computadores sucateados por meio de técnicas hidrometalúrgicas. O trabalho foi composto de três etapas: (i) lixiviação ácida do pó de revestimento da tela de monitores CRT; (ii) separação dos elementos de interesse por extração por solventes em escala de bancada testes descontínuos e (iii) otimização da etapa (ii) em escala micro piloto testes contínuos. Na etapa de lixiviação ácida investigou-se a influência do agente lixiviante, da relação ácido/amostra, tempo e temperatura de reação na porcentagem de solubilização de európio e ítrio do resíduo em estudo. Obteve-se um máximo de solubilização destes (98% p/p) com o emprego de H2SO4 na relação ácido/amostra 1250g/kg em temperatura ambiente (25 C), 10% de sólidos e com agitação mecânica por 30 minutos. O licor obtido no processo de lixiviação, contendo 11,9 g/L de ítrio e 0,72 g/L de európio, foi submetido a testes descontínuos de extração por solventes com a finalidade de separação dos dois íons metálicos. Investigou-se o desempenho dos seguintes extratantes orgânicos no rendimento de extração das espécies de interesse: DEHPA, IONQUEST 801, CYANEX 272 e PRIMENE JMT. O DEHPA na concentração de 1,0 mol/L mostrou-se mais eficiente na separação do par Y/Eu, fator de separação igual a 111,4 na relação de fase A/O = 1 e agitação mecânica por 10 minutos. A partir da isoterma de extração e construção do diagrama McCabe-Thiele, observou-se que dois estágios de extração na relação A/O = 1,1 são suficientes para extrair todo o ítrio da fase aquosa para a fase orgânica, enquanto que o európio fica na fase aquosa. Na lavagem do orgânico carregado, uma solução de H2SO4 0,75 mol/L na relação de fase O/A = 5 foi suficiente para retirar todas as espécies coextraídos na etapa de extração. No processo de reextração, obteve-se 67% de reextração de ítrio da fase orgânica para a fase aquosa com o emprego de HCl 5,0 mol/L na relação de fase O/A = 1. A partir da curva de equilíbrio de reextração, determinou-se que são necessários no mínimo 12 estágios de reextração para se reextrair todo o ítrio da fase orgânica. Após definidas as melhores condições de extração, lavagem e reextração na etapa descontínua, realizou-se cinco ensaios contínuos de extração por solventes em escala micro piloto até se atingir a condição ótima de separação dos elementos em estudo. A melhor separação foi alcançada quando o circuito operou com três estágios de extração, sete de lavagem e quinze de reextração. Ao final do processo obteve-se um rafinado com 0,55 g/L de Eu, 16,7 g/L de Zn e concentração de Y menor que 0,001 g/L. No reextrato, a concentração de Y é de 41,4 g/L e 0,06 g/L de Eu, enquanto que a concentração de Zn foi menor que 0,001 g/L. / This work deals with the study of the recovery of europium and yttrium from discarded computer monitors through hydrometallurgical techniques. It comprises three phases: (i) acid leaching of the coating powder of the monitor screens CRT; (ii) separation of the concerning elements through solvent extraction in a laboratory bench scale discontinuous tests, and (iii) optimisation of phase ii in a micro pilot scale continuous tests. In the acid leaching phase, it was investigated the influence of the leaching agents, the relation acid/sample, time and temperature of the reaction in the percentage of solubilisation of europium and yttrium from the studied residue. The maximum solubilisation achieved (98 w/t%) occurred when H2SO4 in an acid/sample relation of 1250g/kg at room temperature (25 C), 10% of solids and mechanical agitation for 30 minutes were used. The liquor obtained in the leaching process, containing 11.9 g/L of yttrium and 0.72 g/L of europium, was submitted to solvent extraction discontinuous experiments aiming at the separation of the two metallic ions. The behaviour of the following organic extractants - DEHPA, IONQUEST 801, CYANEX 272 and PRIMENE JMT was investigated in relation to the performance of the extraction of the concerned species. DEHPA in concentration of 1.0 mol/L showed to be more efficient in the separation of the pair Y/Eu, with a separation factor equal to 111,4 for phase relation A/O =1, under mechanical agitation for 10 minutes. Based on the McCabe-Thiele diagram, it could be observed that two extraction stages in the relation A/O =1.1 were enough to extract all the yttrium in the aqueous phase to the organic phase, whereas the europium remains in the aqueous phase. In the loaded organic scrubbing, a H2SO4 0.75 mol/L solution in the relation phase O/A of 5 proved to be sufficient to remove all the co-extracted species in the extraction phase. In the stripping phase, 67% of the yttrium extraction was obtained from the organic phase to the aqueous phase by employing HCl 5.0 mol/L in the relation phase O/A = 1. From the stripping isotherm, it was determined that at least 12 stages of stripping are necessary in order to extract all the yttrium in the organic phase. After defining the best extraction, scrubbing and stripping conditions in the discontinuous phase, five continuous solvent extraction experiments were carried out in a micro pilot scale, until the optimum condition for separation of the elements under study was achieved. This degree of separation was attained when the circuit operated with three separation stages, seven washing stages and fifteen stripping phases. At the end of the process, a raffinate containing 0,55 g/L of Eu and 16,7 g/L of Zn and a pregnant stripping solution with 41,4 g/L of Y and 0,06 g/L of Eu was achieved.

Resumo: A sílica mesoporosa do tipo MSU-4 foi sintetizada a partir do agente direcionador de estrutura Tween 20, utilizado como molde, e do precursor inorgânico tetraetilortosilicato (TEOS). Estruturas mesoporosas tem sido aplicadas em estudos luminescentes por apresentarem alto índice de organização, grande área superficial e distribuição regular de tamanho de poros. Nesse trabalho a sílica mesoporosa foi funcionalizada com 3-aminopropiltrietoxisilano (APTES) para aplicação luminescente. A sílica mesoporosa funcionalizada foi caracterizada por difração de raios-X a baixo ângulo (SAXS), espectroscopia no infravermelho (FT-IR) e adsorção e dessorção de nitrogênio (BET). O material luminescente foi preparado pela formação do complexo [Eu(tta)3] em meio metanólico e impregnado nos canais da sílica mesoporosa. Para a impregnação, o íon Eu3+ foi primeiramente encapsulado na sílica e posteriormente foi adicionado o ligante 2- tenoiltrifluoroacetona (tta). Esse procedimento foi realizado para as sílicas lavada, calcinada e funcionalizada. Uma amostra de sílica funcionalizada foi preparada com a impregnação do complexo já pronto. Todas as amostras foram caracterizadas por espectroscopia luminescente. O estudo espectroscópico foi realizado à temperatura ambiente e os espectros de excitação mostraram a absorção de energia pelo ligante tta na faixa do ultravioleta. Os espectros de emissão mostraram as transições características do íon Eu3+, dos estados de maior energia 5D0 para os de menor energia 7F0-4. Foi observado que a transferência de energia do ligante para o íon Eu3+ foi eficiente. A transição hipersensitiva 5D0→7F2 mostrou o efeito das diferentes superfícies da matriz de sílica. PALAVRAS CHAVE: Sílica mesoporosa, luminescência, európio. / Abstract: MSU-4 type mesoporous sílica has been synthesized with polyoxyethylenesorbitan monolaurate (Tween 20) as structure-directing agent (MTS) as a template and tetraethyl orthosilicate Si(OEt)4 (TEOS) as silica source. The mesoporous structures have a wide application in the luminescence study because of their organization, large surface area, and size of pores. In this work, MSU-4 mesoporous silica was functionalized with 3-amino-propyl-triethoxysilane (APTES) for luminescence applications. Mesoporous silica and amino-functionalized silica was characterized by small-angle X-ray scattering (SAXS), infrared spectroscopy (FT-IR) and nitrogen adsorption/desorption isotherms at 77 K (BET). A luminescent material was prepared by formation of the complex Eu(tta)3 in methanolic medium within the channels of MSU-4 type ordered mesoporous silica. Using simple wet impregnation methods, the europium ion was first encapsulated followed by ligand 2-thenoyltrifluoracetonate (tta) addition. This process it was done for washed, calcined and functionalized mesoporous silica. Analogous one sample of functionalized silica was impregnated with the complex already ready. All samples were characterized by photoluminescence spectroscopy. The spectroscopy studies in room temperature showed the energy absorption of the ligand range ultraviolet in excitation spectra. The emission spectra this materials displayed the typical Eu3+ intra-4f6 lines ascribed to transitions between the 5D0,1 excited states and the ground multiplet (7F0-4). Negligible emission from the organic part of the encapsulated species was observed, indicating that energy transfer from the ligands to the Eu3+ ion was quite efficient. The hypersensitive 5D0→7F2 line showed the mesoporous silica effect in luminescence europium chelate. / Orientador: Marco Antonio Utrera Martines / Coorientador: Gustavo Rocha de Castro / Banca: Cláudio Luiz Carvalho / Banca: Ademir dos Santos / Mestre

Orientador: Regina Célia Galvão Frem / Banca: Sidney José Lima Ribeiro / Banca: José Clayston Melo Pereira / Banca: José Maurício Almeida Caiut / Banca: Lippy Faria Marques / Resumo: Este trabalho é dividido em duas partes, na primeira parte foi caracterizado o complexo [Ln(keto)3(H2O)] (Ln = Gd, Eu) por espectroscopia vibracional no infravermelho, analise elementar e otimização da geometria por método DFT. Mas o foco central foram os estudos das propriedades luminescente no intervalo de 12 - 300 K. O espectro de emissão do [Eu(keto)3(H2O)] revela uma forte dependência com a temperatura, bem ilustrada pelo não usual deslocamento amplo para o azul de (17 cm1) da transição 5D07F0 quando a temperatura é elevada de 12 a 300 K. A diferença aritmética entre os espectros de absorção do [Eu(keto)3(H2O)] com o do [Gd(keto)3(H2O)] indicou a presença de uma banda de transferência de carga do ligante para o metal (LMCT) (320-370 nm). A partir da fosforescência do [Gd(keto)3(H2O)] a energia dos estados de tripleto relacionada ao Keto foi determinada mostrando uma grande sobreposição com os níveis intra-4f6 e um forte acoplamento elétron-fônon. A alta ressonância entre o nível LMCT e estados tripletos e os níveis do Eu3+ leva a uma forte dependência do valor do tempo de vida da 5D0, típico da presença de processos de transferência de energia operativos. A segunda parte desse trabalho compreendeu na síntese, caracterização e estudos das propriedades luminescente e magnéticas de uma MOF inédito de formula [Eu2(Btec)1,5(H2O)]n. A MOF foi sintetizada por via hidrotermal e caracterizado por DRX de monocristal e pó, espectroscopia vibracional no infravermelho, reflectânci... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work is divided into two parts, the first part was characterized the complex [Ln(keto)3(H2O)] (Ln = Gd, Eu) by infrared spectroscopy, elemental analysis and geometry optimization by DFT method. But the central focus was the study of luminescent properties in the 12-300 K interval. The emission spectra of [Eu(keto)3(H2O)] reveal a strong dependence with the temperature, well-illustrated by an unusual large blue-shift (17 cm1) of the 5D07F0 transition as the temperature is raised from 12 to 300 K. The arithmetic difference between the absorption spectrum of [Eu(keto)3(H2O)] with that of [Gd(keto)3(H2O)] pointed out the presence of a ligand-to-metal charge transfer (LMCT) band (320-370 nm). From the [Gd(keto)3(H2O)] phosphorescence the energy of the keto-related triplet states was determined showing a large overlap with the intra-4f 6 levels and a strong electron-phonon coupling. The high-resonance between the LMCT and triplet states and the Eu3+ levels leads to a strong dependence of the 5D0 lifetime value, typical of the presence of operative energy transfer processes. The second part of this work included in the synthesis, characterization and study of luminescence and magnetic properties of a novel MOF formula [Eu2(Btec)1,5(H2O)]n. The MOF was synthesized by way hydrothermal and characterized by XRD of single crystal and powder, infrared spectroscopy, diffuse reflectance, elemental analysis, thermal analysis, scanning electron microscopy and N2 physisorption. Compoun... (Complete abstract click electronic access below) / Doutor

Thèse de doctorat : Physique et Chimie de la Matière et des Matériaux : Nancy 1 : 2007. / Titre provenant de l'écran-titre. Bibliogr.