Neste trabalho são relatados os estudos sobre as propriedades fotoluminescentes dos tungstatos de terras raras Eu2(WO4)3 e Gd2(WO4)3:TR3+ (TR3+ = Eu, Sm e Tb) obtidos via três métodos diferentes de preparação: i) método cerâmico, que é o mais antigo e envolve altas temperaturas (>1000 ºC) e períodos prolongados de aquecimento, consistindo na mistura física dos reagentes na forma de pó, trituração e calcinação; ii) método Pechini, que utiliza complexação de cátions em meio de ácido cítrico e etileno glicol, formando uma cadeia polimérica que promove a formação dos tungstatos de TR em temperaturas mais baixas (~750 ºC) e iii) método de combustão, que envolve uma reação exotérmica entre os nitratos metálicos e um combustível orgânico, atingindo bruscamente altas temperaturas (>1000 ºC). A caracterização dos tungstatos de TR foi feita a partir das seguintes técnicas: a) difratometria de raios-X - os difratogramas apresentaram picos característicos dos tungstatos descritos na literatura, que são isoestruturais na série lantanídica formando estrutura de scheelita ; b) espectroscopia IV - os espectros continham bandas de absorção nas regiões espectrais atribuídas à unidade [WO4], confirmando o grupo pontual Td; c) análise térmica - as curvas TG/DTG evidenciaram que a temperatura de obtenção dos tungstatos de TR encontra-se ao redor de 750 ºC; d) microscopia eletrônica de varredura e de transmissão - as micrografias ilustraram a morfologia e o tamanho das partículas dos sistemas obtidos e e) espectroscopia de reflectância difusa - o espectro de reflectância confirmou a posição da banda de transferência de carga O→W em torno de 265 nm. As propriedades fotoluminescentes dos compostos foram estudadas com base nas transições intraconfiguracionais, f5 (Sm3+), f6 (Eu3+) e f8 (Tb3+). Os espectros de excitação apresentaram bandas largas na região do UV, atribuídas à banda de transferência de carga LMCT O→W e O→TR33+ . Para o composto de Eu2(WO4)3, quando a excitação é monitorada na transição intraconfiguracional, 7F0→5L6 do íon Eu3+ (394 nm), seus espectros de emissão apresentam bandas finas oriundas do nível emissor 5D0 e também dos estados 5DJ (J = 1, 2 e 3) em ambas temperaturas 298 e 77 K. Por outro lado, quando os espectros de emissão são monitorados nas bandas LMCT O→W (260 nm) e O→Eu3+ (310 nm) não apresentam bandas oriundas dos níveis emissores 5D3, 5D2 e 5D1 (5DJ→7FJ´). Esse fenômeno evidencia o cruzamento ressonante entre os estados LMCT e os níveis 5DJ (J = 1, 2 e 3). O alto valor dos parâmetros de intensidade Ω2 dos compostos de Eu3+ reflete o comportamento hipersensível da transição 5D0→7F2, indicando que o íon TR3+ encontra-se em um ambiente químico altamente polarizável. Os valores de eficiências quânticas para os compostos Gd2(WO4)3:Eu3+ são maiores que para os compostos Eu2(WO4)3 devido à maior contribuição radiativa nos sistemas dopados. Deve-se considerar que o composto Eu2(WO4)3 contém maior concentração de íons Eu3+, gerando uma maior proximidade e resultando na transferência de energia não-radiativa entre esses íons. Observa-se que o maior valor de eficiência quântica obtida foi para o sistema Gd2(WO4)3:Eu3+ (1%), obtido pelo método Pechini. As micrografias mostraram que a morfologia e o tamanho das partículas dos compostos dependem do método utilizado. As coordenadas CIE (Commission Internationale d\'Eclairage) foram determinadas. / The studies about the photoluminescent properties of the rare earth tungstates Eu2(WO4)3 and Gd2(WO4)3:RE3+ (RE3+ = Eu, Sm and Tb) obtained via three different methods of preparation were reported: i) ceramic method, which is the older one and uses high temperatures (>1000 ºC) and long periods of heating, with the physical mixture of the reagents in the powder form, grinding and calcination, ii) Pechini method, which consists on the complexation of cations in citric acid and ethylene glycol medium, forming a polymeric network that promotes the formation of RE tungstates at lower temperatures (~750 ºC) and iii) combustion method, which is based on a exothermic reaction between metal nitrates and an organic fuel, reaching rapidly high temperatures (>1000 ºC). The characterization of the RE tungstates was made using the following techniques: a) X-Ray diffraction - the XRD patterns showed characteristic peaks of the tungstates described in the literature, which are isostructural in the lanthanidic series, forming the scheelite structure; b) IV spectroscopy - absorption bands assigned to the unit [WO4] were observed in the spectra, confirming the Td point group; c) thermal analysis - the TG/DTG curves evidenced that the obtaining temperature of the RE tungstates lies around 750 ºC; d) scanning and transmission electronic microscopes - the micrographs illustrated the morphology and the particle size of the obtained systems and e) diffuse reflectance spectroscopy - the reflectance spectrum confirmed the position of the O→W charge transfer band around 265 nm. The photoluminescent properties of the compounds were studied based on the intraconfigurational transitions f5 (Sm3+), f6 (Eu3+) and f8 (Tb3+). The excitation spectra showed broad bands in the UV region, assigned to the LMCT O→W and O→TR3+ LMCT. In the case of the Eu2(WO4)3 compound, when the excitation is monitored in the 7F0→5L6 intraconfigurational transition of the Eu3+ ion (394 nm), the emission spectra show narrow bands coming from the 5D0 emitting level and also from the 5DJ states (J = 1, 2 and 3) at both temperatures 298 and 77 K. On the other hand, when the emission spectra are monitored in the O→W (260 nm) and O→Eu3+ (310 nm) LMCT bands, they do not show bands coming from the 5D3, 5D2 and 5D1 (5DJ→7FJ´) emitting levels. This phenomenon evidences the resonance crossover between the LMCT states and the 5DJ levels (J = 1, 2 and 3). The high value of the Ω2 intensity parameters of the Eu3+ compounds reflects the hypersensitive behavior of the 5D0→7F2 transition, indicating that the TR3+ ion lies in a highly polarizable chemistry environment. The quantum efficiencies values for the Gd2(WO4)3:Eu3+ compounds are higher than for the Eu2(WO4)3 compound due to the major radiative contribution in the doped systems. We must consider that the Eu2(WO4)3 compound contains higher concentration of Eu3+ ions, generating proximity and resulting in the non-radiative energy transfer among these ions. We observed that the highest quantum efficiency value was for the Gd2(WO4)3:Eu3+ (1%) system, which was obtained by the Pechini method. The micrographs and the XRD patterns showed that the morphology and the crystallites size of the compounds depend on the used method. The CIE (Commission Internationale d\'Eclairage) coordinates were determined.

Este trabalho apresenta o processo para obtenção de partículas de sílica amino-funcionalizadas contendo complexos de TR3+ utilizando os métodos de Stöber e por micro-ondas. Os espectros de absorção no infravermelho das partículas TR-BTC-Si preparadas pelo método de micro-ondas exibiram bandas de absorção atribuídas aos modos vibracionais dos complexos TR-BTC e da rede de sílica, indicando a incorporação destes complexos na matriz SiO2. Por outro lado, os complexos Eu-(β-dicetonatos) preparados pelo método Stöber mostraram apenas as bandas atribuídas à estrutura da rede de sílica, devido à dupla camada de revestimento de sílica. As morfologias das partículas de sílica amino-funcionalizadas contendo complexos de TR3+ foram visualizadas usando a técnica MEV. As diferenças nas morfologias entre o complexo precursor e o material amino-funcionalizado pode ser atribuído a presença da sílica na superfície do material. Além do mais, o método da ninidrina indicou a presença de grupos amina (-NH2) na superfície destes materiais. Os espectros de emissão dos materiais funcionalizados com os complexos de Eu3+ e Tb3+ apresentaram as bandas de emissão da transição intraconfiguracional dos íons Eu3+ (5D0→7FJ, J = 0-6) e Tb3+ (5D4→7FJ, J = 6-0), exibindo cores características de emissão vermelha e verde, respectivamente. É observado um decréscimo nos valores dos parâmetros Ω2 dos materiais Eu-(β-dicetonato)-Si e Eu-BTC-Si comparados com os respectivos complexos, devido a diminuição da intensidade da transição 5D0→7F2, indicando um maior caráter centrossimétrico. Conseqüentemente, os íons Eu3+ nos materiais com sílica estão em um ambiente químico menos polarizável do que nos complexos, sugerindo uma menor contribuição do mecanismo de acoplamento dinâmico. Os altos valores dos Ω4 para os sistemas com sílica Eu-(&#946-dicetonato)-Si e Eu-BTC-Si comparados com os valores de Ω2 reflete a intensidade extremamente alta da transição 5D0→7F4 observada nos espectros de emissão. Este resultado corrobora com o maior caráter centrossimétrico e evidencia a incorporação dos complexos de Eu3+ na rede de sílica. Foi realizado um fluoroimunoensaio usando os compostos amino-funcionalizados, que mostraram uma luminescência e propriedades físico-químicas eficientes para atuarem como marcadores biológicos. O marcador óptico foi conjugado com o anticorpo anti-oxLDL, que se liga a um suporte específico com o antígeno oxLDL. Portanto, estes materiais são candidatos promissores para conjugação molecular em clínicas de diagnóstico. / This work presents the process to obtain amino-functionalized silica particles containing complexes of trivalent rare earth ions (RE3+) using Stöber and microwave methods. Infrared spectra of the TR-BTC-Si particles prepared by microwave method exhibited absorption bands assigned to the vibrational modes of the TR-BTC complexes and silica network, indicating that the complexes have been incorporated in the SiO2 matrix. However, due to double coating of the silica network, the IR spectra of the Eu-(β-diketonates) complexes prepared by Stöber method showed only bands assigned to the silica structure. The morphologies of the amino-functionalized silica particles containing RE3+ complexes were examined using SEM technique. The difference in morphology between the complex precursor and amino-functionalized material can be attributed to the silica network on the material surface. Besides, the ninhydrin method confirmed the presence of amine groups (-NH2) in the functionalized materials. The emission spectra of the functionalized materials containing Eu3+ and Tb3+ complexes showed the emission bands originated from the intraconfigurational transitions of the Eu3+ (5D0→7FJ, J = 0-4) and Tb3+ (5D4→7FJ, J = 6-0), exhibiting red and green color emission, respectively. It is observed decreasing values of experimental intensity parameters (Ω2) of the Eu-(β-diketonate)-Si and Eu-BTC-Si materials when compared with the complex precursors, owing to the decreased intensity of the 5D0→7F2 transition, indicating a higher centrosymmetric character. As a result, the Eu3+ ions in silica materials are located in a chemical environment less polarizable than in the complexes, suggesting a smaller contribution of dynamic coupling mechanism. On the other hand, an abnormally high intensity of the 5D0→7F4 transition was observed, which is reflected by the high values of Ω4 of the silica systems, Eu-(β-diketonate)-Si and Eu-BTC-Si, compared with the Ω2 ones. These spectroscopic data corroborate with a higher centrosymmetric character, indicating the incorporation of the Eu3+ complexes in the silica network. A fluoroimmunoassay was developed using the amino-functionalized compounds that exhibit efficient luminescence and physical and chemical properties suitable for optical label. The biolabel was then chemically conjugated to anti-oxLDL antibody, which is linked in a specific support with oxLDL antigen. The result showed that it is a promising candidate for molecular conjugation in clinical diagnosis.

Neste trabalho, os complexos tetrakis(ß-dicetonato) de terras-raras, (Q)[TR(&#946;-dicetonato)4 ] {(Q = Li+ , Na+ , K+ , (Et3 NH)+ , (Morf)+ , (TMPip)+ e (Diciclo)+ ); (TR3+ = Eu3+ , Gd3+ , Tb+ e Tm3+ ) e (&#946;-dicetonato = acac, dbm e tta), foram sintetizados, caracterizados e suas propriedades ópticas investigadas por meio de espectroscopia luminescente. Os dados de microanálises de CHN e titulação complexométrica evidenciaram a fórmula geral (Q)[TR(&#946;-dicetonato)4 ]. Os espectros de absorção na região do infravermelho indicaram o caráter anidro da maioria dos complexos, 3+ exceto para (Li)[TR(dbm))4 ].4H2 O, e que a coordenação dos &#946;-dicetonatos aos íons TR3+ ocorre através dos átomos de oxigênio dos grupos carbonila. Os difratogramas de raios-X (método do pó) evidenciam que os complexos com ligante acac e cátions derivados de metais alcalinos são mais cristalinos em relação aos compostos contendo bases nitrogenadas. O estudo fotoluminescente dos complexos (Q)[TR(&#946;-dicetonato)4] foi realizado a partir dos espectros de excitação e emissão registrados a 298 e 77K, e pela curva de decaimento luminescente. Os espectros de emissão dos compostos de Eu3+ , Tb3+ e Tm3+ apresentaram bandas finas características das transições intraconfiguracionais exibindo cores de emissão vermelha oriundas do íon Eu3+ (5 D0 7Fj J = 0-6), verde do íon Tb3+ (5D5 ? Fj, J = 6-0) e azul para do íon Tm3+ (1G4&#8594; 3H6 , e a 1G4&#8594;3 F4 ). Os desdobramentos e a intensidade das transições 5D0&#8594; 7Fj dos complexos de európio sugerem que este íon encontra-se em um ambiente químico D2d distorcido para C4v ou S4 . Com base nos dados espectrais foram determinados os parâmetros de intensidade experimentais (&#937;2, &#937;4 e &#937;6), os coeficientes de emissão radiativa (A<SUBrad) e não radiativa (A<SUBnrad) e a eficiência quântica de emissão experimental do nível 5D0 do íon Eu3+ (&#951;). Para os sistemas tetrakis contendo o ligante tta, o complexo com o contra-cátion (TMPip)+ apresentou o maior valor de &#9372 (42,1x10-20 cm-1) evidenciando um ambiente químico mais polarizável com o maior caráter covalente da ligação Eu3+ (&#946;-dicetonato). Os valores de eficiência quântica (&#951; ) do 5D0 , dos complexos tetrakis(&#946;-dicetonato) de Eu3+ , são altos quando comparados 0 com os compostos tris. Os complexos (Morf)[Eu(tta)4 ] e (TMPip)[Eu(tta)4 ] apresentaram os maiores valores de eficiência quântica &#951; = 88 e 92%, respectivamente. Portanto, estes complexos comportam-se como promissores dispositivos moleculares conversores de luz (DMCLs). A atribuição dos estados T dos ligantes acac, dbm e tta foram feitas a partir dos espectros de emissão dos complexos de gadolínio, (Q)[Gd(&#946;-dicetonato acac)4 ], registrados no estado estacionário e resolvido no tempo, a 77K. Os espectros de emissão dos complexos tetrakis, (Q)[Tm(acac)4] onde Q = Li+, Na+ e K apresentaram a transição 1G4&#8594; 3H6 bastante intensa, indicando a alta luminescência azul. Os espectros de emissão dos complexos tetrakis, (Q)[Tb(acac)4 ], Q = Li+ , Na+ e K+ mostram bandas de emissão finas características das transições 5D4&#8594;7Fj (J = 6-0) e não exibem as emissões originárias do ligante acac, indicando uma transferência de energia intramolecular 3+ eficiente do ligante acetilacetonato ao íon Tb3+ . Os dispositivos OLEDs, bicamada e tricamada, contendo os complexos tetrakis Li[Eu(dbm)4] e Li[Tb(acac)4], como camada emissora e transportadora de elétrons exibiram alta intensidade eletroluminescente vermelha e verde, oriundas das transições 5D0&#8594;7F0-4 e 5D4&#8594;7F6-0 dos íons Eu3+ e TbSUP>3+ , respectivamente. Os espectros triboluminescentes (TL) do complexo (TMPip)[Eu(tta)4 ] apresentam as transições intraconfiguracionais 5D0&#8594;7Fj (J = 0 a 4), com a transição hipersensível 5D0&#8594;7F2 proeminente na região de 612 nm. / This work reports the synthesis, characterization, spectroscopic properties of tetrakis(&#946;-diketonate) complexes of rare earths, (Q)[RE(&#946;-diketonate)4] {(Q+ = Li+, Na+, K+, (Et3NH)+, (Morf)+, (TMPip)+ and (Diciclo)+); (RE3+ = Eu3+, Gd3+, Tb+ and Tm3+) and (&$946;-diketonate = acac, dbm and tta)}. The elemental analysis of CHN and complexometric titration suggest the general formula (Q)[RE(&#946;-diketonate)4]. The infrared spectra indicated the anhydrous character of the complexes, except for (Li)[RE(dbm)4].4H2O, and the coordination between &$946;-diketonate ligands and RE3+ ions occurs through the oxygen atoms of carbonyl groups. The X-ray diffractograms (powder method) confirmed that the complexes with acac ligand and derived alkaline metals cations are more crystalline when compared with the complexes containing nitrogenated bases. The photoluminescence study of the (Q)[RE(&#946;-diketonate)4] complexes was performed through the excitation and emission spectra at 298 and 77K, and luminescence decay curves. The emission spectra of the Eu3+, Tb3+ and Tm3+ complexes displayed characteristic narrow bands arising from intraconfigurational transitions of trivalent rare earths ions and exhibited red color emission for the Eu3+ ion (5D0&#8594;7FJ, J = 0-6), green for the Tb3+ ion ( 5D4&#8594;7FJ, J = 6-0) and blue for the Tm3+ ion ( 1G4&#8594;3H6, and 1G4&#8594;3F4). The splitting and intensity of the 5D0&#8594;7FJ transitions of the europium complexes suggest the distortion of chemical environment around this Eu3+ ion from D2d to C4v or S4. Based on the spectroscopy data, the experimental intensity parameters (&#9372, &#937;4 e &#937;6), the coefficients of radioactive (Arad) and non-radioactive (Anrad) emissions and the quantum efficiency of experimental emission of the emitting 5D0 level of Eu3+ ion (&#951;) were determined. For tetrakis systems containing tta ligand, the complex with (TMPip)+ countercation presented the highest value of &#937;2 (42.1x10-20 cm-1), suggesting the presence of a highly polarizable chemical environment and consequently, indicating the highest covalent character of the Eu3+ - (&#946;-diketonate) bond. The values of quantum efficiency (&#951;) of the emitting 5D0 state of the tetrakis(&#946;-diketonate) complexes of Eu3+ were higher compared with those tris-complexes. The (Morf)[Eu(tta)4] and (TMPip)[Eu(tta)4] complexes presented highest values of quantum efficiency &#951; = 88 and 92%, respectively. Therefore, these complexes can act as potential candidates for Light Conversion Molecular Devices (LCMDs). The triplet states of the acac, dbm and tta ligands were determined from the emission spectra of gadolinium complexes, (Q)[Gd(&#946;-dicetonato acac)4], recorded by steady-state and time-resolved photoluminescence measurements, at 77K. The emission spectra of the tetrakis complexes, (Q)[Tm(acac)4] where Q+ = Li+, Na+ and K+ presented high intensity 1G4&#8594;3H6 transition, showing a intense blue luminescence. The emission spectra of tetrakis complexes, (Q)[Tb(acac)4], Q+ = Li+, Na+ e K+, exhibit characteristic narrow emission bands of the 5D4&#8594;7FJ (J = 6-0) transitions, however, the absent of the broaden band arising from the acac ligand suggests the efficient intramolecular energy transfer from the acetylacetonate ligand to Tb3+ ion. The double-layer and triple-layer OLEDs devices, containing Li[Eu(dbm)4] and Li[Tb(acac)4] tetrakis complexes as emitting layer and electron transport layer, exhibited high electroluminescent intensity with red and green emissions arising from the 5D0&#8594;7F0-4 and 5D4&#8594;7F6-0 transitions of Eu3+ and Tb3+ ions, respectively. The spectra of triboluminescence (TL) of the (TMPip)[Eu(tta)4] complex present intraconfigurational 5D0&#8594;7FJ transitions (J = 0 a 4), with the hypersensitive 5D0&#8594;7F2 transition prominent in the region around 612 nm.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-07-10T11:42:20Z No. of bitstreams: 2 Dissertação - Raphael Lucas de Sousa e Silva - 2017.pdf: 3882688 bytes, checksum: 6b33233b331ed11ce579c9148910d0d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-07-10T11:46:08Z (GMT) No. of bitstreams: 2 Dissertação - Raphael Lucas de Sousa e Silva - 2017.pdf: 3882688 bytes, checksum: 6b33233b331ed11ce579c9148910d0d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-10T11:46:09Z (GMT). No. of bitstreams: 2 Dissertação - Raphael Lucas de Sousa e Silva - 2017.pdf: 3882688 bytes, checksum: 6b33233b331ed11ce579c9148910d0d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Among the various iron oxides studied, a magnetite (Fe3O4) stands out due to its superparamagnetic behavior and its high biocompatibility. Luminescent properties working cooperatively in magnetic nanoparticles with which the material converts certain types of energy into emission of electromagnetic radiation at the same time, which enables an interaction by magnetic fields. In the present work, an investigation and structural, elemental and morphological analysis of superparamagnetic / luminescent particles formed by coating of iron oxide by an SiO2 base network was carried out. The Fe3O4 oxide was synthesized by the coprecipitation method, and in the Eu3+ rare earth together with the 1,10-phenanthroline linker in the network, were responsible for energy transfer processes in systems that checked as optical materials for materials. The nanocomposites synthesized obeyed the formation of a core-shell system and was verified by micrographs obtained by Electron Transmission Electron Microscopy, evidencing a formation of nanoparticles of varied sizes. As the compositions of the phases of the materials were characterized by X-ray Diffraction, Radiated Spark Energy and Absorption Spectroscopy in the Infrared region, showing a crystal phase of the magnetic oxide and a formation of nanocomposite. The properties of interest (magnetism and photoluminescence) were evaluated and the respective results presented agreed with each other, with characteristic emissions of Eu3+ emitting a pink coloration, and an emission intensity for a concentration of this species in the material. The materials presented a superparamagnetic behavior, evidencing that the oxide coating did not change as Fe3O4 magnetic characteristics, and is in turn presented in a saturation magnetization of 55 emu / g with a magnetic domain of 8.9 nm. As nanoparticles have dimensions that indicate that a part has a magnetic domain. / Entre os diversos óxidos de ferro estudados, a magnetita (Fe3O4) destaca-se, devido ao seu comportamento superparamagnético e a sua alta biocompatibilidade. Propriedades luminescentes trabalhando de forma cooperativa em nanopartículas magnéticas faz com que o material converta certos tipos de energia em emissão de radiação eletromagnética ao mesmo tempo, que possibilita a interação por campos magnéticos. No presente trabalho, foi investigada a síntese e a caraceterização estrutural, elementar e morfológica de partículas superparamagnéticas/luminescentes formadas pelo revestimento do óxido de ferro por uma rede a base de SiO2. O óxido Fe3O4 foi sintetizado pelo método de coprecipitação, e o íon terra-rara Eu3+ juntamente com ligante 1,10-fenantrolina na rede, foram responsáveis por processos de transferência de energia inter e intrasistemas que conferiram as propriedades ópticas aos materiais. Os nanocompósitos sintetizados obedeceram a formação de um sistema core-shell sendo comprovado pelas micrografias obtidas por Microscopia Eletrônica de Transmissão, evidenciando a formação de nanopartículas de tamanhos variados. As composições das fases dos materiais foram caracterizadas por Difração de Raios X, Energia Dispersiva de Raios X e Espectroscopia de Absorção na região do Infravermelho, mostrando a fase cristalina do óxido magnético e a formação do nanocompósito. As propriedades de interesse (magnetismo e fotoluminescência) foram avaliadas e seus respectivos resultados apresentaram concordância entre si, com emissões características do íon Eu3+ emitindo uma coloração rosa, e a intensidade de emissão foi equivalente a concentração desta espécie no material. Os materiais apresentaram um comportamento superparamagnético, evidenciando que o recobrimento do óxido não alterou as características magnéticas do Fe3O4, e este por sua vez apresentou uma magnetização de saturação de 55 emu/g com domínio magnético de 8,9 nm. As nanopartículas apresentaram dimensões que indicaram que majoritariamente uma partícula possui apenas um domínio magnético.

Metal-halide perovskites show great promise as solution-processable semiconductors for efficient solar cells and LEDs. In particular, the diffusion range of photogenerated carriers is unexpectedly long and the luminescence yield is remarkably high. While much effort has been made to improve device performance, the barriers to improving charge transport and recombination properties remain unidentified. I first explore charge transport by investigating a back-contact architecture for measurement. In collaboration with the Snaith group at Oxford, we develop a new architecture to isolate charge carriers. We prepare thin films of perovskite semiconductors over laterally-separated electron- and hole-selective materials of SnOₓ and NiOₓ, respectively. Upon illumination, electrons (holes) generated over SnOₓ (NiOₓ) rapidly transfer to the buried collection electrode, leaving holes (electrons) to diffuse laterally as majority carriers in the perovskite layer. We characterise charge transport parameters of electrons and holes, separately, and demonstrate that grain boundaries do not prevent charge transport. Our results show that the low mobilities found in applied-field techniques do not reflect charge diffusivity in perovskite solar cells at operating conditions. We then use the back-contact architecture to investigate recombination under large excess of one charge carrier type. Recombination velocities under these conditions are found to be below 2 cm s⁻¹, approaching values of high quality silicon and an order of magnitude lower than under common bipolar conditions. Similarly, diffusion lengths of electrons and holes exceed 12 μm, an order of magnitude higher than reported in perovskite devices to date. We report back-contact solar cells with short-circuit currents as high as 18.4 mA cm⁻², giving 70% external charge-collection efficiency. We then explore the behaviour of charge carriers in continuously illuminated metal-halide perovskite devices. We show that continuous illumination of perovskite devices gives rise to a segregated charge carrier population, and we find that the distance photo-induced charges travel increases significantly under these conditions. Finally, we examine intermittancy in the photoluminescence intensity of metal-halide perovskite films.

Neste trabalho são relatadas as propriedades fotoluminescentes e eletroluminescentes dos compostos de &#946;-dicetonato de terras raras trivalentes (onde TR3+ = Eu, Sm e Gd) contendo ligantes fosfinóxidos e sulfóxidos. A preparação dos complexos foi feita pela reação do precursor &#946;-dicetonato hidratado [TR(TTA)3(H2O)2] (TTA = tenoiltrifluoroacetonato) com os ligantes fosfinóxidos [trifenilfosfinóxido (TPPO)] e sulfóxidos [dibenzilsulfóxido (DBSO) e difenilsulfóxido (DPSO)] em solução etanólica. Os complexos foram caracterizados por análise elementar, análise termogravimétrica, DRX pelo método do pó e monocristal e espectroscopia IV. Os dados de microanálise e titulação complexométrica evidenciaram que os complexos apresentam a fórmula geral [TR(TTA)3(L)2]. As curvas TG/DTG apresentaram etapas de decomposição térmica bem definidas para os compostos anidros e indicaram que os complexos sintetizados mostram maior estabilidade térmica que o complexo hidratado. Os espectros de absorção na região do infravermelho indicaram que a coordenação do ânion TTA- e ligantes fosfinóxidos e sulfóxidos ao íon TR3+ ocorre através dos átomos de oxigênio. Através da técnica de difratometria de raios-X por monocristal elucidou-se a estrutura molecular do complexo bis(trifenilfosfinóxido )-tris(tenoilfluoracetonato )európio(III) [Eu(TTA)3(TPPO)2]. O complexo em questão apresenta sistema triclínico, com grupo espacial P-1. Oito átomos de oxigênio estão coordenados ao íon central e a esfera de coordenação apresenta-se como um antiprisma quadrado com moléculas de TPPO ocupando faces opostas. Os espectros de emissão mostram que os desdobramentos das transições 5D0&#8594;7Fj (J = 0 a 4) para os complexos de Eu3+ e 4G5/2 &#8594; 6HJ (J = 5/2-11/2) para o Sm3+ obedecem à regra de seleção do número máximo de componentes, sugerindo um grupo pontual de baixa simetria. O alto valor dos parâmetros de intensidade &#937;2 dos complexos de Eu3+ reflete o comportamento hipersensível da transição 5D0&#8594;7F2, indicando que o íon Eu3+ encontra-se em um ambiente químico altamente polarizável. As curvas de decaimento, para os sistemas com os íons Eu3+ e Sm3+, ajustam-se a uma exponencial de primeira ordem, sugerindo que não há outro processo de depopulação para o nível 5D0 e o valor do tempo de vida indica que o processo de transferência de energia é bastante operante. Os compostos preparados com os ligantes sulfóxidos e fosfinóxidos apresentam maior tempo de vida em relação ao complexo [Eu(TTA)3(H2O)2], este fato está associado a ausência de processos de desativação não radiativa referente ao acoplamento vibrônico com as moléculas de água. Os complexos contendo ligantes sulfóxidos e fosfinóxidos apresentam maiores valores de eficiência quântica e rendimento quântico de emissão experimental em relação ao complexo hidratado devido à substituição das moléculas de água, extinguindo assim, a supressão da luminescência pelos osciladores OH. O espectro de fosforescência do composto [Gd(TTA)3(TPPO)2] apresenta bandas referentes aos estados tripletos (T) do TTA- (~ 525 nm). Estas bandas não são observadas no espectro de emissão dos complexos de Eu3+ e Sm3+ indicando que a transferência de energia do estado T de menor energia do TTA- para os níveis emissores 5D0 (Eu3+) e 4G5/2 (Sm3+) é bastante eficiente. O complexo [Eu(TTA)3(TPPO)2] foi utilizado como camada emissora na construção de dispositivos eletroluminescentes com estruturas: ITO/TPD/[Eu(TTA)3(TPPO)2]/Alq3/Al,ITO/MTCD/[Eu(TTA)3(TPPO)2]/Alq3/Al e ITO/MTCD/[Eu(TTA)3(TPPO)2]/Al apresentaram valor máximo de eficiência EL em torno de 0,0011 cd/A em 23 V. Os espectros EL apresentaram emissão características das transições 5D0&#8594;7FJ oriundas do íon Eu3+. As coordenadas da Comissão Internacional de l\'Eclairage (CIE) foram determinadas e mostraram que os dispositivos emitem cor vermelha monocromática. / In this work the photo and electroluminescent properties of the trivalent rare earth (RE3+ = Eu, Sm and Gd) &#946;-diketonate compounds with phosphine oxide and sulfoxide ligands are related. The TR3+ complexes were prepared by the reaction between the hydrated &#946;-diketonate [TR(TTA)3(H2O)2] (TTA = thenoyltrifluoroacetonate) and the phosphine oxides and sulfoxides ligands in ethanolic solution. The complexes were characterized by elemental analysis, thermogravimetric analysis, XRD by powder and monocrystal methods, and IR spectroscopy. The microanalysis and complexometric titration data evidenced that complexes present the general formula [RE(TTA)3(L)2] (where L = triphenilphosphine oxide TPPO, diphenilsulfoxide DPSO and dibenzilsulfoxide DBSO). The TG/DTG curves ofthe anhydrous compounds showed well-defined stages with higher thermal stability when compared to the hydrated complex. The absorption spectra in the infrared region showed that the coordination of TTA anion and ligands to RE3+ ions occurs through the oxygen atoms. The molecular structure of the complex europium (III) tris(&#945;-tenoyltrifluoroacetonate) bistriphenylphosphine oxide [Eu(TTA)3(TPPO)2] was elucidated utilizing the monocrystal X-ray difractometry technique. This complex has a triclinic system, with spatial group P-1, where eight oxygen atoms are coordinated to the rare earth ion and the coordination polyhedron which is best approximated as a squared antiprism whereas there are two TPPO molecules occupying the opposite faces. The emission spectra showed that the 5D0&#8594;7Fj (J = 0-4) and 4G5/2 &#8594; 6HJ (J = 5/2-11/2) transitions of the europium and samarium complexes, respectively splitting in the maximum number components, indicating that the rare earth ions are in a low site symmetries. The high value of the intensity parameters &#937;2 of the Eu3+ complexes reflect the hypersensitive behavior of the 5D0&#8594;7F2 transition indicating that the Eu3+ ion is in a highly polarizable chemical environment. The luminescence decay curves of the systems containing Eu3+ and Sm3+ ions, adjust to a first order exponential, suggesting that there is no other channel for the depopulation to the level 5D0 and the value of lifetime indicate that the transfer energy process is operant. The [Eu(TTA)3(TPPO)2] has a higher lifetime value than europium tris(thenoyltrifluoroacetonate) dihydrate [Eu(TTA)3(H2O)2] due to the absence of the deactivation channel non-radiative by the vibronic coupling from the water molecules. It has been observed an increase in the emission quantum yield ( and emission quantum efficiency) of &#946;-diketonate complexes when the TPPO, DPSO and DBSO ligands substitute the two water molecules. The phosphorescence spectrum of the [Gd(TTA)3(TPPO)2] complex shows bands referent to the triplet states (T) of the TTA-. These bands are not observed in the emission spectra of the Eu3+ e Sm3+ complexes, corroborating that the energy transfer from the lower energy T of the TTA- to the emitting level 5D0 (Eu3+) e 4G5/2 (Sm3+) is very effective. The [Eu(TTA)3(TPPO)2] complex was utilized as emitting layer in the construction of electroluminescent devices with the structure ITO/TPD/[Eu(TTA)3(TPPO)2]/Alq3/Al, ITO/MTCD/[Eu(TTA)3(TPPO)2]/Alq3/Al and ITO/MTCD/[Eu(TTA)3(TPPO)2]/Al and showed high efficiency around 0.0011 cd/A at 23 V The EL spectra presented characteristic emission originated from the Eu3+ ion. The chromaticity coordinates of the Commission Internationale de l\'Eclairage (CIE) was determined and showed that the constructed devices emit a monochromatic red light.

L'utilisation récente des fibres optiques (FOs) à base de silice dans des environnements extrêmes, a incité les chercheurs à accélérer leurs études de vulnérabilité. De tels défis sont fortement liés à la bonne compréhension des effets à la fois macroscopiques et microscopiques des différents types de radiations sur la réponse des FOs. Cette thèse de doctorat présente une étude complémentaire aux études précédemment menées sur les différents défauts ponctuels dans les FOs à base de silice par Cathodoluminescence (CL). Cette technique offre la possibilité de détecter les centres luminescents mais aussi de suivre leurs distributions spatiales, leurs cinétiques de création et de guérison en fonction de l'irradiation électronique. Dans ce manuscrit, nous introduisons tout d'abord un résumé des connaissances actuelles sur les défauts liés à la silice pure et différemment dopée.Les détails de notre procédure expérimentale sont discutés dans le 2ème chapitre où nous montrons que les doses déposées lors des mesures CL sont très importantes. Dans le 3ème chapitre nous présentons une étude systématique de la réponse en CL des différentes classes de FOs, dans lesquelles différentes bandes d'émission sont discutées. Le 4ème chapitre traite l'impact d'une variation des conditions d'irradiation électronique sur les centres GLPC, l'un des défauts liés au Ge les plus importants. Enfin, dans le 5ème chapitre, nous avons montré la possibilité de produire des nanoparticules à base de silice par ablation laser, et la capacité de la technique CL de caractériser ce type de matériaux, ce qui ouvre la porte à d'autres utilisations de cette technique pour la caractérisation de nanoparticules. / The recent use of silica-based optical fibers (OFs) in harsh environments pushed the researchers to accelerate their vulnerability and hardening studies. Such challenges are strongly linked to the good understanding of the macroscopic as well as the microscopic effects of different types of radiations on the silica-based OF's response. This PhD thesis presents a complementary study to previous researches on the properties of different point defects in silica-based OFs by Cathodoluminescence (CL). Such technique offers the ability to both detect the luminescent centers and to follow their spatial distribution, their growth and decay kinetic as a function of the electron beam characteristics. ln the present manuscript we first summarize the current knowledge regarding point defects in pure silica or silica glass doped with Ge, P, Ce, N or Al. Details of the experimental procedure are discussed in the 2nd chapter in which we highlight that the equivalent dose deposited during the various configuration of CL measurements are very large. ln the 3rd chapter, we perform an overview study of the CL responses of different classes of OFs, in which many emission bands related to the different dopants were discussed. The 4th chapter focuses on the study of the effects of varying beam conditions on the signature of Germanium Lone Pair Center (GLPC), one of the most important Ge-related point defects. Finally, in chapter V, we demonstrate the possibility to produce silica-based nanoparticles by laser ablation process, and the ability of the CL technique to characterize such materials, which opens the door to other employments of this technique for future studies on nanoparticles.

This thesis devoted to the experimental studies of yellow and blue luminescence (YL and BL relatively) bands in Gallium Nitride samples doped with C and Si. The band BLC was at first observed in the steady-state photoluminescence spectrum under high excitation intensities and discerned from BL1 and BL2 bands appearing in the same region of the spectrum. Using the time-resolved photoluminescence spectrum, we were able to determine the shape of the BLC and its position at 2.87 eV. Internal quantum efficiency of the YL band was estimated to be 90\%. The hole capture coefficient of the BLC related state was determined as 7 10-10 cm3/s. Properties of BLC were investigated. The YL and BLC bands are attributed to electron transitions via the (0/-) and (+/0) transition levels of the CN defect.

Im Rahmen dieser Arbeit wurde die Methode der Synchrotronröntgenaktivierung entwickelt, um Edelmetallpartikel in Natron-Kalk-Silicatgläsern zu erzeugen. Diese Photoaktivierung ermöglichte es, den Nukleations- vom Wachstumsprozess der Metallteilchen zu trennen und somit sehr kleine Partikel und die Frühstadien des Wachstumsprozesses zu identifizieren. Die Gläser wurden mit Photolumineszenz-, UV-Vis-Absorptions-, EPR-, SAXS- sowie XANES-Spektroskopie untersucht. So konnten in synchrotronaktivierten Gold-dotierten Gläsern Golddimere nachgewiesen werden. Die thermische Behandlung bei 550°C führte über eine heterogene Nukleation zum Wachstum von Goldnanopartikeln. Als Modell für das Nukleationszentrum wurde das an eine Silanolateinheit gebundene Golddimer entwickelt. In synchrotronaktivierten Silber-dotierten Gläsern bildeten sich zunächst Silberatome. Während das Tempern bei 300°C zur Entstehung kleiner lumineszierender Silberteilchen führte, induzierte die thermische Behandlung bei 500°C das Wachstum von Silbernanopartikeln. Die Frühstadien des Gold- und Silberpartikelwachstums wurden als effiziente Donoren in Photolumineszenz-Energietransferprozessen identifiziert. Durch die Anwendung eines Sol-Gel-Spin-Coating-Verfahrens konnten Gold-dotierte Silicat-Titanat-Glasschichten mit einer Goldkonzentration von bis zu 20 mol% hergestellt werden. Die Goldnanopartikel, welche durch Tempern bei 300°C erzeugt wurden, waren durch eine dreiphotonisch induzierte nichtlineare Lumineszenz charakterisiert. Weiterhin konnte die Methode der Titan:Saphir-Laseraktivierung entwickelt und damit Goldnanopartikel-haltige, nanometergroße Strukturen in die Glasschichten geschrieben werden. TEM- und REM-Studien haben gezeigt, dass die Goldnanopartikel nicht nur in die Glasschicht eingebettet sind, sondern sich auch auf der Oberfläche befinden. Die Zugänglichkeit gegenüber Biomolekülen konnte durch den Nachweis der Oberflächen-verstärkten Ramanstreuung adsorbierter Adeninmoleküle bewiesen werden. / Within this work, the technique of synchrotron X-ray activation has been developed to generate noble metal particles in soda-lime silicate glasses. The photoactivation has enabled the separation of nucleation and growth of noble metal particles. Thus, very small particles and the early stages of the cluster growth process could be identified. The glasses have been characterized by photoluminescence, UV-Vis absorption, EPR, SAXS and XANES spectroscopy. As a result, gold dimers could be identified in synchrotron activated gold-doped glasses. Thermal annealing at 550°C has induced the growth of gold nanoparticles by heterogeneous nucleation. As a model for the nucleation center a gold dimer bound to a silanolate center has been suggested. In contrast to gold, in synchrotron activated silver-doped glasses non-luminescent silver atoms have been generated. Annealing at 300°C has induced the growth of small luminescent silver particles. After a thermal treatment at a higher temperature of 500°C silver nanoparticles have been generated. The early stages of the gold and silver cluster growth process have been identified as efficient donators in photoluminescence energy transfer processes. An unprecedented increase of the gold amount of up to 20 mol% has been achieved by the preparation of ultrathin silicate-titanate layers with a sol-gel spin-coating approach. The nonlinear photoluminescence of the gold nanoparticles generated by annealing at 300°C could be excited by a three-photon induced process. Furthermore, the technique of titanium:sapphire laser activation has been developed to write nanometer-sized patterns containing gold nanoparticles into the glassy layers. TEM and SEM studies have shown that the gold nanoparticles are not only embedded within the thin films, but are also located on top of the glassy layers. Their accessibility to biological molecules has been proven by determining the surface-enhanced Raman scattering of adsorbed adenine molecules.

The cost of crystalline silicon solar cells must be reduced in order for photovoltaics to be widely accepted as an economically viable means of electricity generation and be used on a larger scale across the world. There are several ways to achieve cost reduction, such as using thinner silicon substrates, lowering the thermal budget of the processes, and improving the efficiency of solar cells. This thesis examines the use of plasma enhanced chemical vapour deposited silicon nitride to address the criteria of cost reduction for n-type crystalline silicon solar cells. It focuses on the surface passivation quality of silicon nitride on n-type silicon, and injection-level dependent lifetime data is used extensively in this thesis to evaluate the surface passivation quality of the silicon nitride films. The thesis covers several aspects, spanning from characterisation and modelling, to process development, to device integration. The thesis begins with a review on the advantages of using n-type silicon for solar cells applications, with some recent efficiency results on n-type silicon solar cells and a review on various interdigitated backside contact structures, and key results of surface passivation for n-type silicon solar cells. It then presents an analysis of the influence of various parasitic effects on lifetime data, highlighting how these parasitic effects could affect the results of experiments that use lifetime data extensively. A plasma enhanced chemical vapour deposition process for depositing silicon nitride films is developed to passivate both diffused and non-diffused surfaces for n-type silicon solar cells application. Photoluminescence imaging, lifetime measurements, and optical microscopy are used to assess the quality of the silicon nitride films. An open circuit voltage of 719 mV is measured on an n-type, 1 Ω.cm, FZ, voltage test structure that has direct passivation by silicon nitride. Dark saturation current densities of 5 to 15 fA/cm2 are achieved on SiN-passivated boron emitters that have sheet resistances ranging from 60 to 240 Ω/□ after thermal annealing. Using the process developed, a more profound study on surface passivation by silicon nitride is conducted, where the relationship between the surface passivation quality and the film composition is investigated. It is demonstrated that the silicon-nitrogen bond density is an important parameter to achieve good surface pas-sivation and thermal stability. With the developed process and deeper understanding on the surface passivation of silicon nitride, attempts of integrating the process into the fab-rication of all-SiN passivated n-type IBC solar cells and laser doped n-type IBC solar cells are presented. Some of the limitations, inter-relationships, requirements, and challenges of novel integration of SiN into these solar cell devices are identified. Finally, a novel metallisation scheme that takes advantages of the different etching and electroless plating properties of different PECVD SiN films is described, and a preliminary evalua-tion is presented. This metallisation scheme increases the metal finger width without increasing the metal contact area with the underlying silicon, and also enables optimal distance between point contacts for point contact solar cells. It is concluded in this thesis that plasma enhanced chemical vapour deposited silicon nitride is well-suited for n-type silicon solar cells.