Filmes amorfos de nitreto de alumínio (AlN) foram preparados por sputtering de rádio frequência convencional em um alvo de Al+Cr e plasma de nitrogênio puro. A área relativa de Al-Cr determina o conteúdo de Cr, o qual esteve em um intervalo de concentração de ~ 0 3.33 at.% no presente estudo. A deposição dos filmes foi seguida por tratamento térmico das amostras até 1050 ºC e por caracterização espectroscópica através de medidas de EDS (Energy Dispersive Spectrometry), Foto-luminescência e Transmissão Óptica. De acordo com os resultados experimentais, as propriedades óptico-eletrônicas dos filmes de AlN contendo Cr são altamente influenciadas tanto pela concentração de Cr como pela temperatura de tratamento térmico. Na verdade, o tratamento térmico a 1050 ºC induz o desenvolvimento de estruturas que, devido ao seu tamanho típico e características espectrais exclusivas, foram designadas por micro-estruturas de rubi (RbMSs). Estas RbMSs são rodeadas por um meio rico em nitrogênio no qual os íons Cr3+ apresentam características luminescentes não encontradas na literatura. A emissão de luz apresentada pelas RbMSs e suas vizinhanças foram investigadas de acordo com o conteúdo de Cr e a temperatura de medida permitindo a identificação de várias linhas luminescentes relatadas do Cr3+. As principais características destas linhas luminescentes e correspondentes processos de recombinação-excitação são apresentados e discutidos tendo em vista uma análise espectroscópica detalhada. / Films of amorphous aluminum-nitride (AlN) were prepared by conventional radio frequency sputtering of an Al+Cr target in a plasma of pure nitrogen. The Cr-to-Al relative area determines the chromium content, which stayed in the ~ 0 3.33 at.% concentration range in the present study. Film deposition was followed by thermal annealing the samples up to 1050 ºC and by spectroscopic characterization through energy dispersive spectrometry (EDS), Photo-luminescence and Optical Transmission measurements. According to the experimental results, the optical-electronic properties of the Cr-containing AlN films are highly influenced by both the Cr concentration and the temperature of the thermal treatments. In fact, thermal annealing at 1050 °C induces the development of structures which, because of their typical size and unique spectral characteristics, were designated by ruby microstructures (RbMS\'s). These RbMS\'s are surrounded by a nitrogen-rich environment in which Cr3+ ions exhibit luminescent features with no counterpart in the literature. The light emission presented by the RbMS\'s and surroundings were investigated according to the Cr content and temperature of measurement allowing the identification of several Cr3+-related luminescent lines. The main characteristics of these luminescent lines and corresponding excitation-recombination processes are presented and discussed in view of a detailed spectroscopic analysis.

Une zone de constriction dans un micro-canal fluidique peut générer, si le débit est suffisant, un écoulement bi-phasique. Ceci est l’origine de la cavitation hydrodynamique. Les échanges de chaleur latente générés par l’apparition et l’implosion des bulles impliquent une variabilité importante de la température dans les zones au-delà de la constriction. En ajoutant des sondes de température nanométriques dans le fluide et en utilisant un microscope confocal on peut déterminer la température en un point. Ainsi on a pu établir des cartographies thermiques en 2 et 3 dimensions à l’intérieur d’un écoulement stationnaire bi-phasique. La technique permet en outre d’avoir accès à la quantité de gaz ce qui permet de corréler les gradients de température avec les zones de transitions de phases. Des zones de très forts refroidissements sont observées après la constriction, là où les bulles apparaissent. Par contre on n’observe pas les zones d’échauffement attendu à cause de la condensation. Une méthode complémentaire, moins sensible, utilisant la spectroscopie Raman a aussi été utilisée pour confirmer ce résultat. Par ailleurs une nouvelle classe de matériaux luminescents sensible à la température et la pression a été étudiée. Enfin une étude de la production de radicaux lors de l’implosion des bulles a été menée en utilisant la chimiluminescence du luminol. La technique utilisée par comptage de photons a permis de quantifier cette production et une cartographie de l’émission du luminol a permis d’associer celle-ci avec la zone d’implosion des bulles / A constriction in the microchannel can be used to establish a two-phase flow, when a sufficient liquid flux is introduced. This is known as hydrodynamic cavitation. The latent heat resulting from the growing and collapsing vapor bubbles makes it interesting to observe the temperature conditions in the flow downstream of the constriction. Using fluorescence microscopy, with the addition of temperature sensitive nano probes into the working fluid, we can determine the temperature at a single point, averaged over the integration time. Coupled with a confocal microscope, we were able to produce two and three dimensional temperature maps of the steady state flow in the microchannel by the use of ratiometric intensity measurements. This technic allows us to observe temperature gradients in two-phase flow as well yielding the void fraction information. Areas of substantial cooling are observed downstream the constriction in the two-phase flow, linked to the bubble growth, while heating regions due to condensations are missing. A complementary, yet less sensitive probe-less technique using the inherent Raman scattering signal of the liquid, was used to confirm the findings. A separate study evaluating a new group of luminescent materials for optical temperature and pressure probes is performed and discussed herein. Finally, the luminol chemiluminescent reaction with radicals produced by the cavitating flow, is used to obtain a corresponding photon yield. By counting the photons produced, an estimate on the radical yield can be obtained. Additionally, rudimentary mapping of the chemiluminescence signal allows the localization of the bubble collapse regions

Cette étude a pour objectif de développer des matériaux luminescents avec un rendement quantique supérieur à 100% permettant d'améliorer l'efficacité des cellules photovoltaïques. Ces travaux sont basés sur des sulfures avec une faible énergie de phonon. Les verres Ga₂S₃-GeS₂-CsCl dopés par des terres-rares sont d'abord étudiés. Il a été démontré qu'un photon visible peut être divisé en deux photons infrarouges par les couples d'ions Er³⁺/Yb³⁺ou Pr³⁺/Yb³⁺ Cependant, le rendement quantique mesuré avec une sphère intégrante est beaucoup plus faible que 100%. Ceci est attribué aux impuretés qui conduisent au désexcitation non-radiative, et à l'absorption du transfert de charge d'Yb³⁺ qui se situe dans le visible dans le cas des sulfures. Grâce à l'électronégativité plus élevée de l'oxygène par rapport au soufre, la bande de transfert de charge d'Yb³⁺ est repoussée vers l'UV dans des oxysulfures de terres-rares. Les oxysulfures très purs ont été préparés avec la méthode de combustion complétée par une sulfuration. La multiplication de photon dans l'IR a été observée dans La₂O₂S dopé par Pr³⁺/Yb³⁺, Er³⁺/Yb³⁺ ou Tb³⁺/Yb³⁺. Un rendement quantique supérieur à 100% est pour la première fois directement mesuré dans La₂O₂S :Er³⁺,Yb³⁺. Une structure "core-shell" est conçue pour sensibiliser des ions Er³⁺ dans les oxysulfures par des ions Ce³⁺ dans le YAG. Par une précipitation homogène, on a réussi à déposer du Y₂O₂S sur des poudres fines de YAG : Ce³⁺. Bien que la structure désirée ne soit pas encore obtenue due à la diffusion d'Er³⁺ dans le YAG, cette piste de recherche est intéressante pour développer des convertisseurs spectrales avec une bande d'absorption large et intense.

In present work we studied the processes of phase transition of five luminescent liquid-crystals by using emission ellipsometry technique. The samples studied present different mesophases liquid crystalline between the solid crystalline and liquid isotropic phases. The samples were characterized by optical absorption, photoluminescence, and emission ellipsometry technique (EE) in function of sample temperature. The EE measurement allowed us obtain the Stokes parameters, the degree of polarization of emitted light, and ellipticity and rotation angle of the polarization ellipse. In addition, we founded that the degree polarization, the ellipticity, and the rotation angle of polarization ellipse of emitted light change when the sample temperature increase. It was possible to correlate those changes with the phase transition temperature for each sample in concordance with the literature data. Finally, we propose empirical model to explain our results using the emission ellipsometry technique to determine the phase transition temperature of luminescent liquid crystal systems. / Neste trabalho foram estudados processos de transição de fase de cinco cristais líquidos luminescentes através da técnica de elipsometria de emissão. Os compostos estudados possuem mais de uma mesofase líquido-cristalina entre o estado sólido-cristalino e a fase líquido-isotrópica. As amostras foram caracterizadas opticamente pelas técnicas de medidas de absorção óptica, fotoluminescência e elipsometria de emissão (EE) em função da temperatura. A medida de EE nos permitiu obter os parâmetros de Stokes, o grau de polarização, a elipsidade e o ângulo de rotação da luz emitida, sendo possível verificar as mudanças no grau de polarização, na elipsidade da luz e no ângulo de rotação da elipse de polarização da luz emitida pelas amostras com a variação da temperatura das amostras. Foi possível correlacionar essas mudanças da luz emitida pelas amostras com as transições de fase desses materiais e comprovadas por dados da literatura, com boa concordância. Finalmente, propomos um modelo empírico para explicar nossos resultados e certificar a técnica EE para determinação da temperatura de transição de fase em sistemas líquido-cristalinos luminescentes. / Mestre em Física

Este trabalho dedica-se ao estudo de sistemas luminescentes do tipo hóspede-hopedeiro altamente emissivos. A preparação desses materiais se deu a partir da incorporação de complexos organometálicos (Eu3+ e Ir3+) em matrizes mesoporosas inorgânicas e orgâno-modificadas preparadas via sol-gel. Um complexo de európio foi imobilizado por impregnação úmida nos mesoporos de xerogéis e de materiais derivados da peneira molecular MCM-41, enquanto um complexo-surfactante de irídio foi inserido nos canais do MCM-41 como agente diretor da estrutura durante o processo de síntese. Previamente à incorporação dos centros emissores, as matrizes hospedeiras foram caracterizadas do ponto de vista estrutural, morfológico e óptico. As propriedades fotofísicas do material final foram investigadas e comparadas com aquelas apresentadas pelos complexos em solução. Para o complexo de európio foi realizado uma modelagem de suas propriedades ópticas através da teoria do campo ligante, empregando o modelo de recobrimento simples. Nesse tratamento, a geometria do estado fundamental foi obtida pelo método semi-empírico Sparkle/AM1 e confirmada a partir de um mapeamento criterioso dos fatores de carga. Observou-se que, para as amostras dopadas com o complexo de európio, a modificação da matriz hospedeira com grupos orgânicos só leva a melhoria das propriedades ópticas do material final quando a unidade orgânica substitui grupos silanol. Para o MCM-41 preparado com o complexo-surfactante de irídio, constatou-se que as propriedades fotofísicas do material final são muito superiores àquelas apresentadas pelo complexo em solução. / This work dedicates to the study of highly emissive guest-host luminescent materials prepared by the incorporation of organometallic complexes (of Eu3+ and Ir3+) in inorganic and organically-modified mesoporous hosts, obtained via sol-gel methodology. The europium complex (tris[(4 - (4\' - tert - butylbiphenyl - 4 - yl) - 2,2\' - bipyridine - κ2N,N\' - 6 - carboxylato - κO)] europium(III)) was immobilized, via wet impregnation, in the mesopores of silica xerogels and of MCM-41 derived materials. The iridium surfactant-complex (bis[1 - benzyl 4 - (2,4 - difluorophenyl) - 1H -1,2,3 - triazole](4,4\' diheptadecyl - 2,2\' - bipyridine) iridium(III)) was inserted in the channels of MCM-41 while acting as the structure driving agent (template) during the host synthesis procedure. Prior to the incorporation of the luminescent centers in the host matrices, the latter were characterized from the structural, morphological and optical points of view. The photophysical properties of the final luminescent materials were investigated and compared to those presented by the complexes in solution. Particularly, the properties of the Eu-complex were further analyzed, via ligand field theory, employing the simple overlap model. For this treatment, the geometry of the ground state was obtained by the semiempirical Sparkle/AM1 model and confirmed by mapping out the charge factors. For the Eu-complex loaded materials it was verified that the host matrix surface modification with organic groups only results in improved photophysical properties when the organic units substitute silanol groups. For the case of the MCM-41 loaded with the Ir-surfactant-complex, the photophysical properties were found to be much superior to those presented by the complex in solution.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-03-24T17:20:10Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese MAML BIBLIOTECA.pdf: 9163873 bytes, checksum: a3dedf9afddd54463bad724f48c71013 (MD5) / Made available in DSpace on 2017-03-24T17:20:10Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese MAML BIBLIOTECA.pdf: 9163873 bytes, checksum: a3dedf9afddd54463bad724f48c71013 (MD5) Previous issue date: 2016-07-26 / CAPES / Resíduos de tiro (GSR) são evidências físicas de grande valor forense em casos envolvendo o uso de armas de fogo. Mas apesar de sua importância, existe uma carência metodológica para a caracterização do GSR proveniente de munição ambiental (NTA). Adicionalmente, o tamanho micrométrico das partículas geradas torna sua detecção em uma cena de crime ou em um suspeito uma tarefa difícil, podendo originar falsos-negativos. Neste sentido, tem sido proposto o uso de materiais luminescentes para a marcação química e óptica de munições. O presente trabalho aborda o desenvolvimento de marcadores luminescentes baseados na rede metal-orgânica (MOF) [Ln(BTC)] (em que BTC = ácido trimésico), desde a sua síntese, aplicação e avaliação da toxicidade, assim como seu uso na codificação de munição e sua caracterização junto aos resíduos orgânicos de disparo (OGSR). Por isto, este trabalho é dividido em cinco capítulos. No primeiro são discutidos aspectos relativos à síntese da MOF [Eu(BTC)] e à sua influência nas propriedades estruturais, térmicas e espectroscópicas dessa rede. Para tal, os métodos de síntese hidrotermal convencional e hidrotermal assistido por micro-ondas (MW), com diferentes tempos de síntese e proporções metal:ligante, são analisados. Com os métodos adotados, a MOF [Eu(BTC)] foi obtida com elevada cristalinidade, estabilidade térmica e luminescência. Adicionalmente, sínteses mais curtas e proporção metal:ligante 1:1 produziram redes com maior pureza de fase. Neste caso, o método assistido por micro-ondas se destacou devido ao rápido tempo de síntese. No segundo capítulo é apresentada a eficiência dessa MOF como marcador luminescente de munições. Com esta rede, além da detecção visual dos resíduos luminescentes (LGSR), técnicas como espectroscopia de emissão e microscopia eletrônica de varredura acoplada a espectroscopia por dispersão de energia (MEV/EDS) foram usadas para caracterizar e confirmar a presença do LGSR nos resíduos coletados, tanto da arma como das mãos do atirador. No terceiro capítulo são apresentados os dados relativos à avaliação da toxicidade oral aguda e subaguda da MOF [Eu(BTC)] em ratos. Para avaliação da toxicidade aguda, o protocolo 423 da OECD (Organisation for Economic Co-operation and Development) foi utilizado. Como resultado, nenhum sinal de toxicidade foi observado até mesmo para a dosagem mais elevada, e a dose letal média (DL50) foi estimada em 5000 mg/kg. Com isto, a MOF [Eu(BTC)] foi classificada na categoria menos tóxica do GHS (Globally Harmonized System). A toxicidade subaguda foi avaliada através da administração por 7 dias consecutivos de 300 mg/kg e, apesar de observados sinais graves de toxicidade, estes foram atribuídos à aspiração do material particulado para o pulmão, e não a toxicidade do marcador. Estes resultados atribuem a MOF [Eu(BTC)] uma elevada margem de segurança para aplicação como marcador de GSR. No quarto capítulo é proposto um método de codificação de munição baseado no uso de marcadores co-dopados [Y1-xLnx(BTC)] com os íons Eu3+, Sm3+, Tb3+ e/ou Yb3+. Após a realização de disparos, o marcador utilizado em cada munição foi identificado por MEV/EDS em função da composição química dos resíduos em 100% dos casos (sem que o analista tivesse conhecimento do marcador presente em cada munição). Além disso, foi possível estabelecer correlações atirador-arma-local do disparo através da composição dos resíduos em 89% dos casos. E no último capítulo é abordada a caracterização simultânea dos resíduos orgânicos e luminescentes por meio da microscopia Raman. Com a metodologia proposta, através de uma única medida foi possível determinar o tipo de marcador e pólvora utilizados, fornecendo um código muito seguro para caracterização e classificação inequívoca dos resíduos como provenientes de disparo de arma de fogo. Além disso, o LGSR atuou como sonda luminescente ajudando a coletar o OGSR em distâncias acima daquelas normalmente abordadas na literatura. / Gunshot residue (GSR) are physical evidences of great forensic value in firearms-related crimes. Despite its importance, there is a methodologic need for the characterization of GSR from non-toxic ammunition (NTA). In addition, the micrometric size of the generated particles makes its detection in a crime scene or on a suspect a hard task, which may produce false-negatives. In this sense, the use of luminescent materials has been proposed for chemical and optical marking of ammunition. This work presents the development of luminescent markers based on the metal-organic framework (MOF) [Ln(BTC)], since its synthesis, application and toxicity evaluation, as well as its ability to encode ammunitions and its simultaneous characterization with the organic gunshot residue (OGSR). Hence, this work is divided in five chapters. In the first chapter, aspects related to the synthesis of the MOF [Eu(BTC)] and its influence on the structural, thermal and spectroscopic properties are discussed. To this end, conventional hydrothermal synthesis and microwave(MW)-assisted hydrothermal synthesis, with different reaction times and metal:ligand proportions are analyzed. With the chosen methods, the MOF [Eu(BTC)] was obtained with high crystallinity, thermal stability and luminescence. However, faster synthesis and 1:1 metal:ligand proportion produced frameworks with higher phase purity. In this case, the MW-assisted method stood out due to the faster reaction time. In the second chapter, the efficiency of the MOF [Eu(BTC)] as a luminescent marker for ammunition is presented. With this framework, besides visual detection of the luminescent residues (LGSR), techniques as emission spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (MEV/EDS) were used to characterize and confirm the presence of LGSR in the residues collected, both on the gun and in the shooter’s hand. In the third chapter, data related to the evaluation of acute and subacute oral toxicity of the MOF [Eu(BTC)] in rats is presented. For evaluation of acute oral toxicity, the OECD (Organisation for Economic Co-operation and Development) 423 guideline was used. As a result, no signs of toxicity was observed even at the highest dose, and the median lethal dose (LD50) estimated was 5000 mg/Kg. There by, the MOF [Eu(BTC)] was classified in the less toxic category of GHS (Globally Harmonized System). The subacute toxicity was evaluated by consecutive administration of 300 mg/Kg for 7 days and, despite severe toxicity signs were observed, they were attributed to the aspiration of the particulate material into the lungs, but not to the marker’s toxicity. These results give a high safety margin for application of this MOF as a GSR marker. In the fourth chapter an ammunition encoding method is proposed based on the use of the co-doped markers [Y1-xLnx(BTC)] with the ions Eu3+, Sm3+, Tb3+ and/or Yb3+. After shots, the markers used in each ammunition was identified by SEM/EDS due the chemical composition of the residues, in 100% of the cases (without the analyst’s knowledge of which marker was present in each ammunition). Furthermore, shooter-weapon-location correlations was established by the composition of the residues in 89% of the cases. And in the last chapter the simultaneously characterization of the organic and luminescent residues was performed by Raman microscopy. With the proposed methodology, the type of marker and gunpowder used were identified by a single run, providing a security code for its characterization and the unequivocal classification of the residues as coming from firearm discharge. Furthermore, the LGSR acted as a luminescent probe, helping to collect the OGSR further than those reported in the literature.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Hybrid coordination networks such as metal-organic networks, also known as MOF (Metal Organic Framework), have attracted great attention from the scientific community due to their wide diversity and wide range of applications, however, the investigation of applications of these structures still forms a large area of research, with great exploration potential, either through experimental or theoretical chemistry. The present work aims at the use of computational chemistry methods with focus on semiempirical methods for the study of MOFs, so we will initially address results regarding the evaluation of the prediction capacity of solid phase structures of MOFs containing lanthanide as a metallic center. Performed using the semi-empirical methods Sparkle/AM1, Sparkle/PM3, Sparkle/PM6, Sparkle/PM7, Sparkle/RM1 and RM1. The results obtained from the calculation of optimization of the structures suggest that the Sparkle/PM3 and Sparkle/RM1 methods provide more accurate results, with less variability and great agreement with the experimental data, both structural and luminescent. The health application study initially evaluated the structure of the drug doxorubicin and MOF ZnDBC ([Zn(BDC)(H2O)2]n), and then evaluated the drug’s anchoring potential, in order to obtain results that justify the MOF to be chosen as a candidate for application as a drug carrier. This analysis resulted in obtaining a viable anchorage between the MOF lamellae. A simulation of the effects of temperature variation on the structure of the MOF EuBTC ([Eu2(MELL)(H2O)6]) and its effect on the luminescent properties was performed to obtain data that could validate your application with gunshot residues marker, aiming at its use in public safety. This analysis explored the potential of structural description of Sparkle/PM3 as well as the obtaining of luminescent properties, which led to the conclusion that the increase in temperature resulted in an increase in the emission quantum yield caused by the loss of water molecules contained in the first sphere of the coordinating polyhedron. For the application of MOFs in energy, an investigation was carried out regarding the degree of adsorption of the hydrogen gas and methane in the IRMOF-8 and in this one after the doping of its aromatic rings with aluminum atoms, in order to elucidate the effect that the realization of this Doping brings the storage capacity of these gases, for use in gas storage cylinders used in motor vehicles. And it was verified a slight reduction in the storage capacity of the methane gas, since for the hydrogen gas no significant changes were verified. Finally, a study was carried out to evaluate the capture capacity of carbon dioxide and hydrogen sulfide gases in IRMOF-8 and in this doped with aluminum, so the same structure of the previous study was used. It was found that doping gave a considerable increase in the degree of adsorption, being more effective for the carbon dioxide, whose interactions had energy of magnitude of a chemical adsorption. / As redes metalorgânicas também conhecidas como MOF (do inglês Metal Organic Framework) têm atraído grande atenção da comunidade científica devido a sua ampla diversidade e vasta gama de aplicações. Entretanto, a investigação de aplicações destas estruturas ainda configura uma grande área de pesquisa, com potencial de exploração, seja por meio de um viés experimental ou teórico. O presente trabalho tem como objetivo o uso de métodos de química computacional com foco em métodos semiempíricos para o estudo das MOFs. Assim, inicialmente abordaremos resultados referentes à avaliação da capacidade de predição das estruturas em fase sólida de MOFs contendo íons lantanídeos como centro metálico. Este estudo foi realizado através do uso dos métodos semiempíricos Sparkle/AM1, Sparkle/PM3, Sparkle/PM6, Sparkle/PM7, Sparkle/RM1 e o RM1. Os resultados obtidos a partir do cálculo de otimização das estruturas sugerem que o método Sparkle/PM3 e o Sparkle/RM1 proporcionam resultados mais exatos, com menor variabilidade e grande concordância com os dados experimentais, tanto estruturais como luminescentes. Foi avaliado o potencial de ancoragem da doxorrubicina na MOF ZnDBC ([Zn(BDC)(H2O)2]n). Esta análise mostrou viabilidade de ancoragem entre as lamelas da MOF. Além disso, foi realizada uma simulação dos efeitos da variação da temperatura sobre as propriedades luminescentes da MOF EuBTC ([Eu2(MELL)(H2O)6). Com isso, buscou-se validar a aplicação desta MOF como marcador de resíduos de disparo de arma de fogo. Esta análise explorou o potencial de descrição estrutural do Sparkle/PM3, bem como obtenção de propriedades luminescentes. A elevação da temperatura resultou no aumento do rendimento quântico de emissão, causado pela perda de moléculas de água contidas na primeira esfera do poliedro de coordenação. Para aplicação de MOFs na área de energia, foi realizada uma investigação referente ao grau de adsorção de gás hidrogênio e metano na IRMOF-8. Foi realizada a inclusão de átomos de alumínio nos anéis aromáticos, visando elucidar qual o efeito provocado sobre a capacidade de armazenamento desses gases. A dopagem levou a uma leve redução na capacidade de armazenamento do gás metano. Já para o gás hidrogênio não foram verificadas alterações significativas. Por fim, foi feito um estudo de avaliação da capacidade de captura dos gases dióxido de carbono e sulfeto de hidrogênio na IRMOF-8, tanto pura quanto dopada com alumínio. Notou-se que a dopagem proporcionou um considerável aumento no grau de adsorção, sendo mais efetivo para o dióxido de carbono, cujas interações tiveram energia de magnitude de uma adsorção química. / São Cristóvão, SE

De nouveaux précurseurs borates-triéthoxysilanes comprenant le closo-decahydrodecaborate ont été préparés et immobilisés dans la silice. L'introduction des groupements trialkoxysilyles sur les clusters (NH4)2B10H10, a été réalisée par condensations électrophiles faisant appel à des réactifs nucléophiles dans des conditions douces, tout en épargnant l'utilisation d'électrophiles ou de catalyseurs coûteux. Les borates-trialkoxysilanes obtenus ont été caractérisés par RMN 1H, 13C, 11B, 29Si, 31P, IRTF, analyse élémentaire et spectroscopie de masse. Comme preuve de concept, ces précurseurs ont été incorporés de manière covalente dans les pores d'une silice mésoporeuse, SBA-15. Tous les matériaux hybrides mésoporeux et modifiés avec du borate-triéthoxysilane ont été caractérisés par RMN solide 11B et 29Si, DRX, MET, les analyses élémentaires et étude de l'adsorption d'azote (méthode BET). Les précurseurs silylés-borate ont été combinés avec des nanoparticules de silice pour une utilisation éventuelle dans BNCT, où des NPs d'environ 100 nm ont été synthétisées comprenant deux types de centres luminescents différents. FITC silylé (isothiocyanate de fluorescéine) et complexe Eu (III) silylé ont été respectivement immobilisés dans des nanoparticules de silice par le procédé sol-gel. Les deux types de nanoparticules luminescentes ont été fonctionnalisés par les groupes silylés-borates et caractérisés par RMN du solide 11B, 31P et 29Si, DLS, MET, analyses élémentaires, d'adsorption d'azote et spectrophotométrie. / New borate-triethoxysilane precursors comprising the closo-decahydrodecaborate cluster were prepared and immobolized into hybrid silica materials. The synthesis of silylated clusters starting from (NH4)2B10H10 and silane precursors R-Si(OEt)3 through Electrophilic Induced Nucleophilic Reactions was performed under mild conditions, the silylated clusters were analyzed by 1H, 13C, 11B, 29Si, 31P NMR, IR, elemental analyses and mass spectroscopy ES-ESI. As a proof of concept, the borate-triethoxysilane precursors were covalently incorporated into the pores of mesoporous silica, SBA-15 type. All mesoporous materials modified with borate-triethoxysilane were characterized by 11B and 29Si solid state NMR, XRD, TEM, elemental analyses and Nitrogen sorption studies. The silylated-borate precursors were combined with dye-doped silica nanoparticles for possible future use in BNCT technique, where ~100 nm nanoparticles were synthesized comprising two different types of luminescent centers. Silylated FITC (fluorescein isothiocyanate) and silylated Eu(III) complexes were embedded into silica nanoparticles through sol-gel process. Both types of luminescent nanoparticles were functionalized with the silylated-borate clusters and characterized by 11B, 31P and 29Si solid state NMR, DLS, TEM, elemental analyses, Nitrogen sorption studies and spectrophotometer.

Les propriétés spectroscopiques des monocristaux de α-ZnAl2S4, semi-conducteurs de type spinelle avec une large bande interdite, dopées par les ions des métaux de transition sont investigués et leur interprétation est donnée. Les monocristaux, obtenus par la méthode de transport chimique en phase vapeur avec la concentration des impuretés dopantes compris entre 0.01 – 0.1% at., représentent des octaèdres homogènes optique avec des faces orientent (111). Les analyses par les rayons X ont confirmé que tous les échantillons ont cristallisés dans une structure normale de type spinelle avec la symétrie cubique Fd3m (Oh7). Les monocristaux de α-ZnAl2S4 : Ti manifestent des propriétés radiatives dans le domaine spectral du proche infrarouge 0.8–1.4μm. Les résultats spectroscopiques obtenus dans l’intervalle des températures 10-300K (les spectres de la photoluminescence stationnaire et résolue en temps, de l’absorption et de l’excitation de la photoluminescence) sont interprétés dans les termes d’un cluster composé par un ion de Ti4+ dans une configuration octaédrique des six ions de soufre. Les bandes spectrales observées sont attribuées à des transitions électroniques survenues d’un transfert de charge ligand Ti4+ pour les sites octaédriques de titane, qui est en concordance avec la évidence expérimentale de l’absence du RPE signale des ions de Ti. Les constantes vibroniques des niveaux excités et l’auteur de la barrière potentielle entre eux ont étés calculés. La structure des spectres d’absorption et de la luminescence des monocristaux de α-ZnAl2S4 :Co est déterminé par les transitions électroniques des ions de Co2+ localisés dans des sites tétraédriques. Quatre composantes spectrales radiatifs sont révélés en utilisant la spectroscopie résolue en temps sous différentes longueur d’onde d’excitation et il est montré que la photoluminescence des monocristaux de α-ZnAl2S4 : Co est dû aux transitions électroniques entre les niveaux excités des ions de Co2+. Les valeurs calculées des constantes de l’interaction spin – orbite des niveaux excités indiquent une faible influence du part de champ cristallin et une forte interaction spin – orbite. L’absorption optique et la photoluminescence des monocristaux de α-ZnAI2S4 : V sont déterminées des transitions électroniques du vanadium trivalent situé dans des sites octaédriques. L’augmentation de la température est accompagnée par l’amplification de la luminescence intégrale et l’élargissement du spectre centré à λ =1.4μm. Trois composantes spectrales radiatifs de α-ZnAI2S4 : V révélés aux basses températures sont dû aux transitions électroniques des ions de V3+. D’après l’analyse comparative des propriétés spectroscopiques des monocristaux de type spinelle de α-ZnAl2S4 dopés par les ions des métaux de transition Ti, Co, et V, le plus favorable comme milieux actifs laser, est le composée α-ZnAl2S4 : V3+, qui pourrais assurer l’émission dans le domaine des longueurs d’ondes 1.2-1.6μm, ce qui correspondent à la région spectrale utilisée par les systèmes des communications sur fibre optique. / Spectroscopic properties of α-ZnAl2S4 spinel-type single crystals of the wide band gap semiconductor doped by the transition metals Ti, Co and V are investigated and their interpretation is presented. The crystals, grown by the chemical vapour transport method, with activator impurities concentrations 0.01 – 0.1% at., correspond to optically homogeneous octahedrons with (111) - oriented mirror-like faces. The x-ray analyses confirm that all samples crystallised into the normal spinel type structure with Fd3m (Oh7) cubic symmetry. It is found out that α-ZnAl2S4:Ti single crystals exhibit luminescence in the IR spectral range 0.8–1.4μm. The spectroscopic results obtained in the temperature range 10-300K (steady-state and time resolved photoluminescence, optical absorption and excitation luminescence spectra) are interpreted in terms of a cluster composed of the central Ti4+ ion in an octahedral coordination of six sulphur ions. The observed spectral bands are assigned to the electronic transitions arising from the ligand – Ti4+ charge transfer for octahedral sites of titanium that is in agreement with the experimental evidence for the absence of the EPR signal from Ti ions. The vibronic coupling constant for the excited levels and the barrier height between them are calculated. The structure of the absorption and luminescence spectra of α-ZnAl2S4:Co crystals is determined by the electronic transitions of Co2+ ions located in tetrahedral sites. Four radiative spectral components are revealed using the time-resolved spectroscopy at different excitation wavelengths and it is shown that the luminescence of α-ZnAl2S4:Co crystals is due to the electronic transitions between the excited levels of Co2+ ions. The calculated values of the spin-orbit coupling constants of the excited levels indicate a weak crystal field influence and a strong spin-orbit coupling. It is determined that the absorption and luminescent properties of α-ZnAl2S4:V spinel type crystals are the result of electronic transitions of trivalent vanadium ions located in octahedral sites. The rise of temperature leads to the enhancement of the integral luminescence intensity and to the broadening of the spectrum centered at λ =1.4μm. Three main spectral components of the α-ZnAI2S4:V IR spectra revealed at low temperatures are caused by electronic transitions of V3+ ions. The coexistence of a broad band with the narrow lines at low temperatures, when the thermal energy kBT is much less than the height of the potential barrier between the excited states, is explained assuming that there is a phonon assisted tunnelling between these states. On the base of the comparative analysis of spectroscopic properties of α-ZnAl2S4 spinel type crystals doped with transition metals Ti, Co, and V it is established that α-ZnAl2S4:V3+ compounds are the most appropriate for applications as active media for solid state IR-lasers tunable in the 1.2-1.6μm wavelength range, which corresponds to the spectral region used in the fibre-optics communication systems.

Filmes amorfos de nitreto de alumínio (AlN) foram preparados por sputtering de rádio frequência convencional em um alvo de Al+Cr e plasma de nitrogênio puro. A área relativa de Al-Cr determina o conteúdo de Cr, o qual esteve em um intervalo de concentração de ~ 0 3.33 at.% no presente estudo. A deposição dos filmes foi seguida por tratamento térmico das amostras até 1050 ºC e por caracterização espectroscópica através de medidas de EDS (Energy Dispersive Spectrometry), Foto-luminescência e Transmissão Óptica. De acordo com os resultados experimentais, as propriedades óptico-eletrônicas dos filmes de AlN contendo Cr são altamente influenciadas tanto pela concentração de Cr como pela temperatura de tratamento térmico. Na verdade, o tratamento térmico a 1050 ºC induz o desenvolvimento de estruturas que, devido ao seu tamanho típico e características espectrais exclusivas, foram designadas por micro-estruturas de rubi (RbMSs). Estas RbMSs são rodeadas por um meio rico em nitrogênio no qual os íons Cr3+ apresentam características luminescentes não encontradas na literatura. A emissão de luz apresentada pelas RbMSs e suas vizinhanças foram investigadas de acordo com o conteúdo de Cr e a temperatura de medida permitindo a identificação de várias linhas luminescentes relatadas do Cr3+. As principais características destas linhas luminescentes e correspondentes processos de recombinação-excitação são apresentados e discutidos tendo em vista uma análise espectroscópica detalhada. / Films of amorphous aluminum-nitride (AlN) were prepared by conventional radio frequency sputtering of an Al+Cr target in a plasma of pure nitrogen. The Cr-to-Al relative area determines the chromium content, which stayed in the ~ 0 3.33 at.% concentration range in the present study. Film deposition was followed by thermal annealing the samples up to 1050 ºC and by spectroscopic characterization through energy dispersive spectrometry (EDS), Photo-luminescence and Optical Transmission measurements. According to the experimental results, the optical-electronic properties of the Cr-containing AlN films are highly influenced by both the Cr concentration and the temperature of the thermal treatments. In fact, thermal annealing at 1050 °C induces the development of structures which, because of their typical size and unique spectral characteristics, were designated by ruby microstructures (RbMS\'s). These RbMS\'s are surrounded by a nitrogen-rich environment in which Cr3+ ions exhibit luminescent features with no counterpart in the literature. The light emission presented by the RbMS\'s and surroundings were investigated according to the Cr content and temperature of measurement allowing the identification of several Cr3+-related luminescent lines. The main characteristics of these luminescent lines and corresponding excitation-recombination processes are presented and discussed in view of a detailed spectroscopic analysis.