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.

La thèse porte sur l’étude des verres d’encapsulation pour des cellules solaires en silicium monocristallin. Deux pistes ont été explorées pour réduire les pertes d’efficacité dues à l’encapsulation : la réduction de la réflexion de verres à base de silice avec des couches antireflets ainsi que l’utilisation de verres fluorés dopés terres rares à conversion de fréquence. Dans le premier cas, des couches antireflets ont été déposées sur des verres à base de silice par la méthode sol-gel. Les caractérisations optiques des verres ont été réalisées par spectrophotométrie et ellipsométrie et l’influence des différents verres sur les caractéristiques densité de courant-tension (J-V) ont été testées sous simulateur solaire dans des conditions standards (AM1.5 et 100 mW/cm2) pour une ou plusieurs cellules de référence. Une autre piste explorée a été celle des verres fluorés dopés terres rares ayant des propriétés de conversion de fréquence (conversion de photons non absorbés vers une énergie proche du gap optique du silicium). Des matrices fluorées de type ZBLA et ZLAG dopées terres rares (Pr3+, Tm3+, Yb3+) ont été utilisées. L’influence du dopage sur les performances électriques des cellules encapsulées a été étudiée en corrélation avec les propriétés physiques et optiques (transfert d’énergie, photoluminescence, transmittance) des verres. Le bénéfice de la conversion de fréquence a pour la première fois été montrée sur les caractéristiques J-V pour des échantillons co-dopés Pr3+-Yb3+. De plus, les caractéristiques des cellules de référence en utilisant ces nouveaux verres d’encapsulation ont été comparées à celles des verres utilisés habituellement dans l’industrie. / The thesis studies the encapsulation glass for monocrystalline silicon solar cells. Two ways were explored to reduce the efficiency loss due to encapsulation: reducing reflection losses of silica based glasses with antireflection layers and the use of rareearth- doped fluoride glass for frequency conversion. On the one hand, antireflection layers have been deposited on the silica glass by sol-gel method. The optical characterizations were carried out by spectrophotometry and ellipsometry and the influence of different encapsulation glasses on the current density-voltage characteristics (J-V) were measured under solar simulator irradiation in standard conditions (AM1.5 and 100 mW/cm2) for various reference cells. On the other hand, the rare-earth-doped fluoride glasses which they can convert frequencies in order to change the energy of photons to energies adapted to the optical gap of the silicon has been investigated. The glasses used are fluorinated matrix ZLAG and ZBLA doped with rareearth elements (Pr3+, Tm3+, Yb3+). The effect of doping on the electrical performance of encapsulated cells was studied correlated with physical and optical properties of glasses (energy transfer, luminescence, transmittance). Frequency conversion was demonstrated by luminescence for all of the rare-earth-doped samples. Then the most promising results for encapsulating was found for codoped Yb3+-Pr3+ ZBLA glass. The benefit of the frequency conversion was shown for the first time in J-V characteristics. Then, characteristics of the reference cells with these new encapsulating glasses were compared to those from glasses commonly used in the photovoltaic modules industry

Die 17 Elemente der Seltenen Erden sind Bestandteil vieler Hochtechnologieprodukte, wie Elektromotoren, Spezialgläsern oder Katalysatoren, dennoch liegt die Recyclingrate aus End-of-Life-Produkten derzeit unter 1 %. Mit der Feststoffchlorierung wurde im Rahmen dieser Arbeit eine chemikalien- und kostensparende Methode für den Aufschluss Seltener Erden aus Leuchtstoff- und Magnetabfällen untersucht. Dabei wurden die gemahlenen Edukte mit NH4Cl vermischt und anschließend im Drehrohrofen erhitzt. Durch thermische Zersetzung des NH4Cl wird HCl- und NH3-Gas freigesetzt. Ersteres überführt die Seltenen Erden in die wasserlöslichen Metallchloride, während der NH3 im Prozess als Lösung in 5N-Reinheit anfiel. Die Seltenerdausbeuten lagen je nach Ausgangsstoff zwischen 83,9 und 99,9 %. Die Optimierung der Feststoffchlorierung erfolgte anhand statistischer Versuchspläne, wodurch neue, überraschende Erkenntnisse im Hinblick auf Reaktionsverläufe, Selektivitäten und Prozessführung gewonnen werden konnten.

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.

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.

Luminescent materials find numerous applications in recent times and have enriched human lives in several different ways. From display and lighting technologies to security, sensing and biological investigations, luminescent organic compounds have become indispensible and often preferred over their inorganic counterparts. The versatility of organic materials arises from their comparative low costs, ease of fine-tuning, low toxicity and the possibility to develop flexible devices. Even until very recent times, the investigations and usage of organic luminescent materials were mostly limited to solution-state properties. However, with progress of available characterisation techniques and parallel development of their usage in solid-state devices and other applications (e.g. security, forensics, sensing etc.), significantly greater attention has been paid to the development and investigations of solid-state emissive organic materials. In solid-state applications, apart from the molecular properties of any given material, their cumulative i.e. bulk physical properties are of even greater importance. Thus, investigations of structure-property relationships in organic luminescent compounds to understand their molecular and bulk properties are of fundamental interest. In this thesis, NPI (1,8-naphthalimide) and BODIPY (boron-dipyrromethene) dyes were investigated to provide a broad overview of their structure-property correlations. Among commonly encountered organic luminescent materials, NPIs and BODIPYs have emerged as two broad classes of luminescent organic compounds, finding applications as functional luminescent materials in various fields. However, lack of understanding for controlling the cumulative emissive properties of these compounds has limited their usage as active solid-state emitters in various applications. This thesis presents several new insights into the molecular and bulk emissive properties of these two classes of luminescent dyes (NPIs and BODIPYs). The contents of the six chapters contained in this thesis are summarised below. Chapter 1 summarises the available understanding of the basic concepts of photoluminescence and the design strategies to develop solid-state luminescent and AIE (aggregation-induced emission) active materials. This chapter also emphasises in the basic nature of the NPI and BODIPY compounds, their substitution patterns and their inherent characteristics and touches upon the relatively unexplored properties of NPI and BODIPY based materials. The importance and scope of the work reported in the thesis is outlined at the end of the chapter. Chapter 2 describes a detailed investigation of a series of seven (4-oxoaryl substituted) NPI compounds (1-7) providing an insight into the molecular and cumulative photophysical behaviour of these compounds. The low ICT characteristics of the NPIs, coupled with the twisted geometry, facilitated solid-state luminescence in these materials. The solution and solid-state luminescent properties of these compounds can be directly correlated to their structural rigidity, nature of substituents and solid-state intermolecular interactions (e.g. π-π stacking, C-H•••O interactions etc.). The solid-state crystal structures of the NPI siblings are profoundly affected by the pendant substituents. All of the NPIs (1-7) show antiparallel dimeric π-π stacking interactions in the solid-state which can further extend in parallel, alternate, orthogonal or lateral fashion depending on the steric and electronic nature of the C-4′ substituents. Structural investigations including Hirsfeld surface analysis methods reveal that while strongly interacting systems show weak to moderate emission in their condensed states, weakly interacting systems show strong emission yields under the same conditions. The nature of packing and extended structures also affects the emission colors of the NPIs in the solid-state. DFT computational studies were utilized to understand the molecular and cumulative electronic behavior of the NPIs. Apart from the investigation of solid-state luminescence, other functional potentials of these NPIs were also explored. One of the compounds (i.e. 4) shows chemodosimetric response towards aqueous Hg(II) species with a ‘turn-on’ response. Also, depending on the molecular flexibility of the compounds, promising AIEE (aggregation-induced emission enhancement) features were observed in these NPIs. Later (in Chapter 3), we developed a systematic investigation in a series of purely organic NPIs, restricting various parameters, to attain a thorough understanding of such AIEE properties. Chapter 3 describes a detailed experimental and computational study in order gain an insight into the AIE (aggregation-induced emission) and AIEE mechanisms in NPI compounds. Systematic structural perturbation was used to fine tune the luminescence properties of three new 1,8-naphthalimides (8-10) in solution and as aggregates. The NPIs (8-10) show blue emission in solution state and the fluorescence quantum yields depend on their molecular rigidity. In concentrated solutions of the NPIs, intermolecular interactions were found to result in quenching of fluorescence. In contrast, upon aggregation (in THF:H2O mixtures), two of the NPIs show aggregation-induced-emission-enhancement (AIEE). The NPIs also show moderately high solid-state emission quantum yields (~10-12.7 %). The AIEE behaviors of the NPIs depend on their molecular rigidity and nature of intermolecular interactions. The NPIs (8-10) show different extents of intermolecular (π-π and C-H•••O) interactions in their solid-state structures depending on their substituents. Detailed photophysical, computational and structural investigations suggest that only an optimal balance of structural flexibility and intermolecular communication is the effective recipe for achieving AIEE characteristics in these NPIs. Chapter 4 presents the design, synthesis and detailed investigations and potential applications of a series of NPI-BODIPY dyads (11-13). The NPI and BODIPY moieties in these dyads are electronically separated by oxoaryl bridges and the compounds only differ structurally with respect to methyl substitutions on the BODIPY fluorophore. The NPI and BODIPY moieties retain their optical features in these molecular dyads (11- 13). Dyads 11-13 show dual emission in solution state originating from the two separate fluorescent units. The variations of the dual emission in these compounds are controlled by the structural flexibility of the systems. The dyads also show significant AIES (Aggregation-Induced-Emission Switching) features upon formation of nano-aggregates in THF-H2O mixtures with visual changes in emission from green to red color. Whereas the flexible and aggregation prone system (i.e. compound 11) shows aggregation-induced enhancement of emission, rigid systems with less favorable intermolecular interactions (i.e. compound 12-13) show aggregation-induced quenching of emission. The emission-intensity vs. the structural-flexibility correlations were found to be reverse in solution and aggregated states. Photophysical and structural investigations suggest that the intermolecular interactions (e.g. π-π stacking etc.) play major role in controlling emission of these compounds in aggregated states. Similar trends were also observed in the solid-state luminescence of these compounds. The applications of the luminescent dyads 11-13 as live-cell imaging dyes was also investigated. Chapter 5 describes investigations of photophysical properties of a series of six BODIPY dyes (14-19) in which there is a systematic alteration of a common -C6H4Si(CH3)3 substituent. Inrelated constitutional isomers, the systematic increment of steric congestion and lowering of molecular symmetry around the BODIPY core result in a steady increment of solution and solid- state fluorescence quantum yields. The increasing fluorescence quantum yields (solution, solid state) with increasing steric congestions show that the molecular free rotation and aggregation-induced fluorescence quenching of BODIPYs can be successfully suppressed by lowering the flexibility of the molecules. Photophysical and DFT investigations reveal that the electronic band gap in any set of these constitutional isomers remain almost similar. However, the crystal structures of the compounds reveal that the solid-state colour and quantum yields of the compounds in solid-state are also related to the nature of intermolecular interactions. Chapter 6 demonstrates the use of DFT computational methods to understand the effect of alkyl groups in governing the basic structural and electronic aspects of BODIPY dyes. As demonstrated in Chapter 4 and Chapter 5, apparently electronically inactive alkyl groups can be of immense importance to control the overall photophysics of BODIPYs. In this context, a systematic strategy su was utilized considering all possible outcomes of constitutionally-isomeric molecules to understand the effects of alkyl groups on the BODIPY molecules. Four different computational methods were employed to ascertain the unanimity of the observed trends associated with the molecular properties. In line with experimental observations, it was found that alkyl substituents in BODIPY dyes situated at 3/5-positions effectively participate in stabilization as well as planarization of such molecules. Screening of all the possible isomeric molecular systems was used to understand the individual properties and overall effects of the typical alkyl substituents in controlling several basic properties of such BODIPY molecules.

A luminescência persistente é um fenômeno em que o material emite radiação de segundos a várias horas após cessada a irradiação (luz, radiação UV, feixe de elétrons, etc.). No entanto, os mecanismos que geram o fenômeno da luminescência persistente ainda não são totalmente estabelecidos. Neste trabalho os materiais Lu2O3:TR3+,M (TR,M: Pr,HfIV; Eu, Ca2+ ou Tb,Ca2+) foram preparados pelo método de estado-sólido assistido por micro-ondas (MASS) e comparados com aqueles sintetizados pelo método cerâmico. As vantagens do método MASS incluem curto tempo de processamento, aquecimento dielétrico seletivo, baixo consumo de energia e uso de equipamentos de baixo custo (forno micro-ondas doméstico), muitas vezes produzindo produtos de alta pureza e alto rendimento. Os materiais foram caracterizados pelas técnicas de espectroscopia de absorção na região do infravermelho (IR), espectroscopia Raman, difração de raios X método do pó (DRX), microscopia eletrônica de varredura (MEV), X-ray absorption near edge structure (XANES), Extended X-ray absorption fine structure (EXAFS), X-ray Excited Optical Luminescence (XEOL), espectroscopia de fotoluminescência na região do UV-Visível, espectroscopia de fotoluminescência na região do UV-UV vácuo e termoluminescência (TL). Os fósforos Lu2O3:TR3+,M (TR,M: Pr,HfIV; Eu, Ca2+ ou Tb,Ca2+) foram preparados em um curto período de tempo (22-26 min) pelo método MASS utilizando forno micro-ondas doméstico, carvão ativado como susceptor, fluxos (H3BO3 ou Na2CO3) e sem a aplicação de gases. Todos materiais preparados com fluxo de H3BO3 exibem impurezas de LuBO3 que foram quantificadas por refinamento Rietveld. Os fluxos e os dopantes não alteraram consideravelmente a estrutura cristalina da matriz C-Lu2O3. As micrografias MEV sugerem que o fluxo de Na2CO3 e os precursores nitratos geram partículas de Lu2O3 com tamanho menor devido a evolução de gases provenientes da decomposição destes compostos. Por outro lado, quando é usado óxidos como precursores os materiais apresentam maiores tamanhos de partícula e na presença de H3BO3 leva a maior agregação. Os dados de XANES indicam que houve completa redução do íon TbIV &#8594 Tb3+ e parcial do PrIV &#8594 Pr3+, devido ao uso de carvão ativado que gera CO(g) durante o tratamento térmico. Os espectros da luminescência persistente indicam emissões nas regiões do vermelho/NIR, vermelho alaranjado e verde atribuídas as transições 4fN &#8594 4fN características dos íons Pr3+, Eu3+ e Tb3+, respectivamente. As diferenças entre os espectros registrados sob excitação UV e após cessada a irradiação podem ser explicadas pela emissão da luminescência persistente predominante dos íons TR3+ no sítio S6 do que no C2. Além disso, a co-dopagem aliovalente com os íons HfIV e Ca2+ aumentam a intensidade e duração da luminescência persistente. Isto ocorre através da geração de armadilhas provenientes dos dois co-dopantes nos sítios de Lu3+ e por defeitos produzidos na compensação de carga. Os materiais fotônicos preparados pelo método MASS com fluxo de H3BO3 apresentam maior intensidade e duração da luminescência persistente comparados aos preparados pelo método cerâmico ou sem a presença de H3BO3. Os mecanismos da luminescência persistente foram desenvolvidos através de princípios similares baseados nos dados experimentais da energia do band gap, posição dos níveis de energia dos íons TR3+/2+ na matriz e energia das armadilhas. Isto confirma a solidez da interpretação dos dados experimentais dos materiais Lu2O3:TR3+,M exibindo luminescência persistentes e encoraja a expansão de modelos similares para outros materiais apresentando esse fenômeno. Os fósforos Lu2O3:Pr3+,HfIV,Lu2O3:Eu3+(,Ca2+) e Lu2O3:Tb3+,Ca2+) apresentaram sintonização de cores de emissão tanto para o fenômeno da fotoluminescência como da luminescência persistente, podendo atuar como bons candidatos nas aplicações de bioimageamento ou sensibilizadores de células solares. / Persistent luminescence is a phenomenon where the material emits radiation from seconds to several hours after cessation of irradiation (light, UV radiation, electron beam, etc.). The persistent luminescence mechanisms are not entirely established, however. In this work, the materials Lu2O3:TR3+,M (TR,M: PrHfIV; Eu, Ca2+ or Tb,Ca2+) were prepared by MASS method as well as compared to these materials synthetized by ceramic method. The advantages of MASS method include short processing time, selective dielectric heating, low energy consumption and use of inexpensive equipment (domestic microwave oven), often affording high-purity and high-yield products. The materials were characterized by Infrared absorption spectroscopy (IR), Raman spectroscopy, X-ray powder diffraction (XPD), Scanning electron microscopy (SEM), X-ray absorption near edge structure (XANES), Extended X-ray absorption fine structure (EXAFS), X-ray excited optical luminescence (XEOL), photoluminescence spectroscopy in the UV-Visible range, photoluminescence spectroscopy in the UV-UV vacuum region and thermoluminescence (TL). The phosphorsLu2O3:TR3+,M (TR,M: Pr,HfIV; Eu, Ca2+ or Tb,Ca2+) were rapidly (22-26 min) and successfully prepared by MASS method using a domestic microwave oven, carbon as susceptor, fluxes (H3BO3 or Na2CO3) and without special gases application. All materials prepared with H3BO3 flux exhibit LuBO3 impurities that were quantified by Rietveld refinement. The flux and dopants does not considerably affect the crystalline structure of the C-Lu2O3 host matrix. Scanning electron micrographs suggest that Na2CO3 flux and nitrates precursors produce Lu2O3 particles of small size due to the gases evolution from the decomposition of these compounds. On the other hand, the materials prepared from oxides precursors have particles of large size and H3BO3 flux induces particle xi aggregation. The carbon used as the susceptor generates CO gas, leading to complete reduction of TbIV to Tb3+ and partial conversion of PrIV to Pr3+ present in the Tb4O7 and Pr6O11 precursors, as indicated by XANES. Persistent luminescence spectra of the materials show emission in the red/NIR, reddish orange and green ranges assigned to the 4fN &#8594 4fN transitions characteristics of Pr3+, Eu3+ and Tb3+ ions, respectively. Differences between the spectra recorded under UV excitation and after ceased the irradiation can be explained by the predominant persistent luminescence emission of TR3+ ion in the S6 site rather than TR3+ in the C2 site. In addition, inclusion of HfIV and Ca2+ codopants in the Lu2O3 host increases the emission intensity and duration of persistent luminescence due to generation of traps caused by charge compensation in the lattice as well as these metal ions in the Lu3+ sites. The photonic materials prepared by MASS method with H3BO3 flux show higher persistent luminescence performance than those prepared by the ceramic method or MASS without flux. The persistent luminescence mechanisms were developed through similar principles based on experimental data of band gap energy, energy level positions of TR3+/2+ ions in the host and traps energy. This similarity confirms the consistency of the interpretation of experimental data for the Lu2O3:TR3+,M materials and encourages the expansion of similar models for other persistent luminescence materials. Color tuning of persistent luminescence in Lu2O3:TR3+,M (TR,M: Pr,HfIV; Eu,Ca2+ or Tb,Ca2+) provides potential applications in bioimaging as well as in solar cell sensitizers.

Neste trabalho apresenta-se a obtenção e caracterização de materiais luminescentes baseados em matrizes mesoporosas incorporadas com espécies moleculares altamente emissivas; o corante rodamina 6G (R6G) e o complexo de irídio (III) (N,N-trans-[Ir-(1-benzil-4-(2,4-difluorofenil)-1,2,3-triazol)2(4,4´-dimetil-2,2´-bipiridina)]+). Na incorporação da R6G foram explorados xerogéis mesoporosos sílica de composições puramente inorgânica e modificada com grupos aromáticos, além de vidros mesoporosos sódio aluminosilicato. O complexo de Irídio (III) foi incorporado somente aos vidros sódio aluminosilicato. As matrizes hospedeiras preparadas por metodologia sol-gel foram planejadas e desenvolvidas em consonância com as propriedades físico-químicas das espécies emissoras, a fim de promover maior incorporação e dispersão molecular via diferentes interações químicas. Por exemplo, no caso da sílica modificada com grupos aromáticos, espera-se que haja interação por afinidade química entre tais grupos e as ligações insaturadas das moléculas de R6G, resultando em maior taxa de incorporação e de retenção do centro emissor, bem como minimizando agregações moleculares. No caso dos vidros sódio aluminosilicato, a incorporação de ambas espécies catiônicas, o corante e o complexo de Ir(III), ocorre via troca iônica com íons Na+, que atuam como compensadores de carga dos sítios (AlO4)- da rede. Neste caso, um controle de dispersão molecular do centro emissor foi proposto variando-se a relação Si/Al na matriz (entre 2 e 9), a fim de promover a distribuição espacial dos sítios aniônicos ativos (AlO4)- entre os sítios neutros SiO4. A partir dessas abordagens foram obtidos materiais luminescentes quimicamente estáveis, com alto grau de dispersão molecular, fácil preparação, e excelentes propriedades fotofísicas. Previamente à incorporação, as matrizes foram caracterizadas do ponto de vista estrutural por diversas técnicas de RMN de estado sólido, DRX e sorção de N2. As propriedades fotofísicas dos emissores em solução e em estado sólido foram caracterizadas por medidas de absorção UV-Vis, espectroscopia óptica, tempo de vida de estado excitado e rendimento quântico absoluto. Adicionalmente, as matrizes contendo R6G foram submetidas a testes de ação laser e fotoestabilidade. Os resultados destes sistemas foram analisados com base na teoria do éxciton (em inglês, Single Exciton Theory). No que concerne os sistemas contendo o complexo de Irídio (III), suas propriedades fotofísicas foram relacionadas à eletrônica do centro emissor obtida por teoria do funcional de densidade (em inglês, Density Functional Theory, DFT). Neste caso, a partir do tratamento convencional realizado para moléculas em estado líquido, foram desenvolvidos e analisados métodos alternativos para tratar o problema em uma matriz hospedeira. O formalismo aplicado contribuiu para uma descrição detalhada da estrutura eletrônica do complexo, bem como mudanças devido à inserção deste na matriz. / This work presents the preparation and characterization of luminescent materials based on mesoporous host matrices loaded with highly emissive molecular species (the organic dye Rhodamine 6G (R6G), and the Iridium (III) complex (N,N-trans-[Ir-(1-benzyl-4-(2,4-difluorophenyl)-1,2,3-triazole)2(4,4´-dimethyl-2,2´-bipyridine)]+). In the case of R6G loading we have explored purely inorganic and organically modified silica compositions, as well as sodium-aluminosilicate glasses. The Ir(III) complex was loaded solely into the sodium-aluminosilicate glasses. The host matrices were designed and developed, via sol gel methodology, in consonance with the physicalchemical properties of the emitters aiming at improved molecular incorporation and dispersion through various chemical interactions. For instance, in the case of silica modified with aromatic groups, interaction among such groups with the unsaturated bonds of the R6G molecule is expected, resulting in higher molecular incorporation and retention efficiencies, as well as decreased aggregation. In the case of the sodium-aluminosilicate glasses, the loading of both cationic species, dye and Ir(III) complex, takes place via ionic exchange with Na+ at the (AlO4)- network sites. In this case, control of molecular dispersion of the emitting center was attempted by varying the Si/Al ratio in the matrix (between 2 and 9), so as to promote the spatial distribution of the active anionic sites among neutral SiO4 sites. Through these approaches, we were able to obtain materials with high chemical stability, high molecular dispersion, facile and low cost obtainment and excellent photophysical properties. Prior to loading, the matrices were characterized from the structural point of view through several solid state NMR techniques, XRD and N2 sorption. The photophysical properties of the emitters in solution and in the solid state were characterized and compared through UV-Vis absorption and emission, excited state lifetimes and absolute quantum yields measurements. Moreover, the R6G loaded materials were tested in a laser cavity with respect to their laser efficiencies and photo stabilities. The results of these systems were analyzed in terms of the Single Exciton Theory. As for the materials loaded with Ir(III) complex, the photophysical studies were complemented by a theoretical approach though Density Functional Theory, DFT. From the conventional treatment performed for iridium (III) complexes in liquid state, alternative methods were developed and analyzed for treating the problem in the host matrix. The applied formalism contributed to a detailed description of the electronic structure of the complex, as well as of the changes perceived due to insertion in the matrix.

Materiais cerâmicos têm se mostrado atrativos para o desenvolvimento de novos materiais funcionais avançados no estado-da-arte especialmente devido às suas propriedades ópticas, magnéticas e eletrônicas moduláveis. Materiais luminescentes (incluindo os materiais fosforescentes, fluorescentes e persistentes), são promissores para muitas aplicações tecnológicas como LEDs, sinalização de atenção, biomarcadores etc.; assim, o estudo dos seus fenômenos ópticos tem um papel fundamental na engenharia de materiais mais eficientes. Os materiais que apresentam o fenômeno de luminescência persistente são capazes de emitir luz por longos períodos de tempo após cessada a fonte de irradiação. O método cerâmico, no qual altas temperaturas (> 1000 °C) e longos tempos de tratamento térmico (> 10 h) são requeridos, é o método de síntese mais usado para obtenção dessa classe de materiais. Portanto, há a necessidade do desenvolvimento de métodos mais rápidos, de menor consumo de energia e mais baratos para síntese desses compostos. Nesta tese, compostos com luminescência persistente de fórmula geral Sr2MgSi2O7:Eu2+,TR3+ foram preparados pelos métodos cerâmico-CCM (TR3+: Y, La-Lu) de coprecipitação-CPC (TR; Dy) e de estado sólido assistido por micro-ondas-MASS(TR: Dy) com o objetivo de investigar a influência dos métodos de síntese nas suas propriedades fotônicas. A caracterização dos materiais foi feita para explorar aspectos fundamentais dos compostos por uma ampla variedade de técnicas utilizadas, tais como, TGA, DTA, FTIR, XRD, SEM, NTA, XAS, PL e TL. De forma concisa, os principais resultados desta tese incluem a obtenção da fase cristalina desejada para o material particulado, com especial atenção às amostras obtidas em apenas 25 minutos de síntese pelo método MASS, correspondendo a um processo quase 20 vezes mais rápido do que o método cerâmico tradicional. Os materiais apresentaram uma larga banda de excitação entre 225 e 450 nm, atribuída às transições 4f7(8S7/2)&38594;4f65d1(2D) do íon Eu2+, indicando que estes materiais absorvem luz do UV ao visível. O comportamento de emissão destes materiais é bem descrito pela banda larga em 470 nm atribuída à transição 4f65d1(2D)→4f7(8S7/2) do íon Eu2+ na região do azul. A eficiência da luminescência persistente se mostrou um parâmetro fortemente dependente do codopante utilizado e do método de síntese. Os resultados de termoluminescência e de decaimento de luminescência persistente indicam que os materiais codopados com Tm3+ e Dy3+ são aqueles com maior tempo de emissão da luminescência persistente e que o método MASS o que produz materiais mais eficientes. Sendo assim, foi possível demonstrar a obtenção e os aspectos fundamentais das propriedades fotônicas do composto Sr2MgSi2O7:Eu2+,TR3+ com luminescência persistente de mais de 125 minutos, usando um método de síntese mais rápido, mais barato e de menor consumo de energia. / Ceramic materials have been attractive to the development of new state-of-the-art advanced functional materials, especially due to their tunable optical, magnetic and electronic properties. Luminescent materials (including phosphorescent, fluorescent and persistent materials) are promising to many technological applications such as LEDs, warning signs, medical biomarkers, etc.; thus, the studies of their optical phenomena play an important role in efficient materials engineering. Materials presenting persistent luminescence phenomenon are capable to emit light for long periods of time after ceased the irradiation source. The Ceramic Method, in which high temperatures (>1000 °C) and long-time thermal treatments (>10 h) are required, is the most common synthesis method used to obtain this class of materials. Therefore, the development of faster, energy-efficient and lower-prices synthesis methods is needed. In this work, persistent luminescent compounds with general formulae Sr2MgSi2O7:Eu2+,TR3+ were prepared via: ceramic method (CCM - RE3+: Y, LaLu), co-precipitation method (CPC, RE3+: Dy) and microwave-assisted solid-state method (MASS - RE3+: Dy) in order to investigate the influence of synthesis method parameters in their photonic properties. Important aspects of the materials characterization were explored using a wide range of techniques such as TGA, DTA, FTIR, PXRD, SEM, NTA, XAS, PL and TL. In summary, the main results of the thesis include the obtention of the desired phase powder materials, with special attention to the samples prepared via MASS method within 25 min of synthesis time, almost 20 times faster than the CCM method. The materials have shown a broad absorption band (from 225 to 450 nm) assigned to the Eu2+ 4f7(8S7/2)→ 4f65d1(2D) transition, showing that the materials absorb light from UV to visible. The emission behavior of these materials is well described by its 470 nm-centered broad emission band in the blue region of the visible range. The persistent luminescence efficiency is strongly dependent on the co-dopants as well as synthesis methods. The thermoluminescence and the persistent emission decay analysis indicate that Tm3+ and Dy3+ co-doped materials have the longest emission time and that MASS synthesis produce the most efficient materials. All pointed, we have demonstrated the obtention and the fundamental aspects of photonic properties of the Sr2MgSi2O7:Eu2+,TR3+ materials with persistent luminescence lasting for more than 125 min using a faster, cheaper and lower-energy synthesis method.

Neste trabalho apresenta-se a obtenção e caracterização de materiais luminescentes baseados em matrizes mesoporosas incorporadas com espécies moleculares altamente emissivas; o corante rodamina 6G (R6G) e o complexo de irídio (III) (N,N-trans-[Ir-(1-benzil-4-(2,4-difluorofenil)-1,2,3-triazol)2(4,4´-dimetil-2,2´-bipiridina)]+). Na incorporação da R6G foram explorados xerogéis mesoporosos sílica de composições puramente inorgânica e modificada com grupos aromáticos, além de vidros mesoporosos sódio aluminosilicato. O complexo de Irídio (III) foi incorporado somente aos vidros sódio aluminosilicato. As matrizes hospedeiras preparadas por metodologia sol-gel foram planejadas e desenvolvidas em consonância com as propriedades físico-químicas das espécies emissoras, a fim de promover maior incorporação e dispersão molecular via diferentes interações químicas. Por exemplo, no caso da sílica modificada com grupos aromáticos, espera-se que haja interação por afinidade química entre tais grupos e as ligações insaturadas das moléculas de R6G, resultando em maior taxa de incorporação e de retenção do centro emissor, bem como minimizando agregações moleculares. No caso dos vidros sódio aluminosilicato, a incorporação de ambas espécies catiônicas, o corante e o complexo de Ir(III), ocorre via troca iônica com íons Na+, que atuam como compensadores de carga dos sítios (AlO4)- da rede. Neste caso, um controle de dispersão molecular do centro emissor foi proposto variando-se a relação Si/Al na matriz (entre 2 e 9), a fim de promover a distribuição espacial dos sítios aniônicos ativos (AlO4)- entre os sítios neutros SiO4. A partir dessas abordagens foram obtidos materiais luminescentes quimicamente estáveis, com alto grau de dispersão molecular, fácil preparação, e excelentes propriedades fotofísicas. Previamente à incorporação, as matrizes foram caracterizadas do ponto de vista estrutural por diversas técnicas de RMN de estado sólido, DRX e sorção de N2. As propriedades fotofísicas dos emissores em solução e em estado sólido foram caracterizadas por medidas de absorção UV-Vis, espectroscopia óptica, tempo de vida de estado excitado e rendimento quântico absoluto. Adicionalmente, as matrizes contendo R6G foram submetidas a testes de ação laser e fotoestabilidade. Os resultados destes sistemas foram analisados com base na teoria do éxciton (em inglês, Single Exciton Theory). No que concerne os sistemas contendo o complexo de Irídio (III), suas propriedades fotofísicas foram relacionadas à eletrônica do centro emissor obtida por teoria do funcional de densidade (em inglês, Density Functional Theory, DFT). Neste caso, a partir do tratamento convencional realizado para moléculas em estado líquido, foram desenvolvidos e analisados métodos alternativos para tratar o problema em uma matriz hospedeira. O formalismo aplicado contribuiu para uma descrição detalhada da estrutura eletrônica do complexo, bem como mudanças devido à inserção deste na matriz. / This work presents the preparation and characterization of luminescent materials based on mesoporous host matrices loaded with highly emissive molecular species (the organic dye Rhodamine 6G (R6G), and the Iridium (III) complex (N,N-trans-[Ir-(1-benzyl-4-(2,4-difluorophenyl)-1,2,3-triazole)2(4,4´-dimethyl-2,2´-bipyridine)]+). In the case of R6G loading we have explored purely inorganic and organically modified silica compositions, as well as sodium-aluminosilicate glasses. The Ir(III) complex was loaded solely into the sodium-aluminosilicate glasses. The host matrices were designed and developed, via sol gel methodology, in consonance with the physicalchemical properties of the emitters aiming at improved molecular incorporation and dispersion through various chemical interactions. For instance, in the case of silica modified with aromatic groups, interaction among such groups with the unsaturated bonds of the R6G molecule is expected, resulting in higher molecular incorporation and retention efficiencies, as well as decreased aggregation. In the case of the sodium-aluminosilicate glasses, the loading of both cationic species, dye and Ir(III) complex, takes place via ionic exchange with Na+ at the (AlO4)- network sites. In this case, control of molecular dispersion of the emitting center was attempted by varying the Si/Al ratio in the matrix (between 2 and 9), so as to promote the spatial distribution of the active anionic sites among neutral SiO4 sites. Through these approaches, we were able to obtain materials with high chemical stability, high molecular dispersion, facile and low cost obtainment and excellent photophysical properties. Prior to loading, the matrices were characterized from the structural point of view through several solid state NMR techniques, XRD and N2 sorption. The photophysical properties of the emitters in solution and in the solid state were characterized and compared through UV-Vis absorption and emission, excited state lifetimes and absolute quantum yields measurements. Moreover, the R6G loaded materials were tested in a laser cavity with respect to their laser efficiencies and photo stabilities. The results of these systems were analyzed in terms of the Single Exciton Theory. As for the materials loaded with Ir(III) complex, the photophysical studies were complemented by a theoretical approach though Density Functional Theory, DFT. From the conventional treatment performed for iridium (III) complexes in liquid state, alternative methods were developed and analyzed for treating the problem in the host matrix. The applied formalism contributed to a detailed description of the electronic structure of the complex, as well as of the changes perceived due to insertion in the matrix.