Quantum networks lie at the heart of distributed quantum computing and secure quantum communication - research areas that have seen a strong increase of interest over the last decade. Their basic architecture consist of stationary nodes composed of quantum processors which are linked via photonic channels. The key requirement, and at the same time the most demanding challenge, is the efficient distribution of entanglement between distant nodes. The two ground states of single spins confined in self-assembled InGaAs quantum dots provide an effective two-level system for the implementation of quantum bits. Moreover, they offer strong transition dipole moments with outstanding photonic properties allowing for the realisation of close to ideal, high-bandwidth spin-photon interfaces. These properties are combined with the benefits of working in the solid state, such as scalability and integrability of devices, to form a promising candidate for the implementation of fast entanglement distribution. In this dissertation we provide the first implementation of a unit cell of a quantum network based on single electron spins in InGaAs. We use a probabilistic scheme based on spin-photon entanglement and the erasure of which path information to project the two distant spins into a maximally entangled Bell state. The successful generation of entanglement is verified through a reconstruction of the final two-spin state and we achieve an average fidelity of $61.6\pm2.3\%$ at a record-high generation rate of $5.8\,\mathrm{kHz}$. One of the main constraints to the achieved fidelity is the limited coherence of the electron spin. We show that it can be extended by three orders of magnitude through decoupling techniques and develop a new measurement technique, allowing us to investigate the origins of the decoherence which has previously been obscured by nuclear feedback processes. Our results evidence that further extension of coherence is ultimately limited by intrinsic mechanisms closely related to local strain due to the growth method of self-assembled quantum dots. After establishing the intrinsic limits to the electron coherence we investigate the coherence properties of the single hole spin as an alternative two-level system with the potential for higher coherence times. We show that the hole spin coherence is indeed superior to the one of the electron and realise the first successful dynamic decoupling scheme implemented in these systems. We find that the decoherence at low external magnetic fields is still governed by coupling to the nuclear spins whereas it is dominated by electrical noise for fields exceeding a few Tesla. This noise source is extrinsic to the quantum dots and a better understanding offers the potential for further improvement of the coherence time. The findings of this work present a complete study of the coherence of the charge carriers in self-assembled quantum dots and provide the knowledge needed to improve the implementation of a quantum-dot based quantum network. In particular, the combination of spin-spin entanglement and the hole coherence times enable further research towards multidimensional photonic cluster states.

abstract: This research focuses on the stress and structure evolution observed in-situ during the earliest stages of thin film growth in Cu on Au(111)-reconstruction. For the research, an ultra high vacuum-scanning tunneling microscopy (UHV-STM) system was modified to have the additional capabilities of in-situ deposition and in-situ stress evolution monitoring. The design and fabrication processes for the modifications are explained in detail. The deposition source enabled imaging during the deposition of Cu thin films, while also being columnar enough to avoid negatively impacting the function of the microscope. It was found that the stress-induced changes in piezo voltage occurred over a substantially longer time scale and larger piezo scale than used during imaging, allowing for the deconvolution of the two sources of piezo voltage change. The intrinsic stress evolution observed at the onset of Cu growth was tensile in character and reached a maximum of 0.19 N/m at approximately 0.8ML, with an average tensile slope of 1.0GPa. As the film thickness increased beyond 0.8 ML, the stress became less tensile as the observation of disordered stripe and trigon patterns of misfit dislocations began to appear. The transport of atoms from the surface of enlarged Cu islands into the strained layer played an important role in this stage, because they effectively reduce the activation barrier for the formation of the observed surface structures. A rich array of structures were observed in the work presented here including stripe, disordered stripe and trigon patterns co-existing in a single Cu layer. Heteroepitaxial systems in existing literature showed a uniform structure in the single layer. The non-uniform structures in the single layer of this work may be attributed to the room temperature Cu growth, which can kinetically limit uniform pattern formation. The development of the UHV-STM system with additional capabilities for this work is expected to contribute to research for the stress and structure relationships of many other heteroepitaxial systems. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2012

Issues with the dissolution and diffusion of polysulfides in liquid organic electrolytes hinder the advance of lithium–sulfur (Li-S) batteries for next generation energy storage. To trap and re-utilize the polysulfides, brush-like, zinc oxide (ZnO) nanowires based interlayers were prepared ex-situ using a wet chemistry method and were coupled with a sulfur/multi-walled carbon nanotube (S/MWCNT) composite cathode. The cell with this configuration showed a good cycle life at a high current rate ascribed to (a) a strong interaction between the polysulfides and ZnO nanowires grown on conductive substrates; (b) fast electron transfer and (c) an optimized ion diffusion path from a well-organized nanoarchitecture. A praline-like flexible interlayer consisting of titanium oxide (TiO2) nanoparticles and carbon (C) nanofiber was further prepared in-situ using an electrospinning method, which allows the chemical adsorption of polysulfides throughout a robust conductive film. A significant enhancement in cycle stability and rate capability was achieved by incorporating this interlayer with a composite cathode of S/MWCNT. These results herald a new approach to building functional interlayers by integrating metal oxides with conductive frameworks. The derivatives of the TiO2/C interlayer was synthesized by changing the precursor concentration and carbonization temperature. Finally, a dual-interlayer was fabricated by simply coating titanium nitride (TiN) nanoparticles onto an electro-spun carbon nanofiber mat, which was then sandwiched with a sulfur/assembled Ketjen Black (KB) composite cathode with an ultra-high sulfur loading. The conductive polar TiN nanoparticles not only have a strong chemical affinity to polysulfides through a specific sulfur-nitrogen bond but also improve the reaction kinetics of the cell by catalyzing the conversion of the long-chain polysulfides to lithium sulfide. Besides, carbon nanofiber mat ensures mechanical robustness to TiN layer and acts as a physical barrier to block polysulfides diffusion. The incorporation of dual interlayers with sulfur cathodes offers a commercially feasible approach to improving the performance of Li-S batteries.

Dans le domaine stratégique des biocapteurs sans marquage, la détection de l'élément biologique est directement liée à la variation d'un paramètre physique donné du composé sensible (transducteur). Dans le cas de la détection de l'hybridation de l'ADN par spectroscopie d'impédance électrochimique non faradique (sans label redox), la détection se base sur le changement de conductivité de l'élément sensible. Celui-ci est généralement un matériau semi-conducteur. La présence sur sa surface, de charges électriques amenées par des biomolécules chargées, comme les brins d'ADN, induit, par un phénomène connu d' »effet de champ électrique », la création d'une zone de charge d'espace subsurfacique. Celle-ci se caractérise par la courbure vers la surface des niveaux énergétiques. En conséquence de quoi, l'impédance de l'interface électrolyte/ADN/semi-conducteur varie. Antérieurement, nous avions démontré la faisabilité de l'utilisation de films d'oxydes semi conducteurs, tels CdIn204, SnO2 pur ou dopé, présentant des surfaces denses 2D en tant qu'éléments sensibles dans des capteurs à ADN basés sur la détection par spectroscopie d'impédance électrochimique non faradique. Les résultats avaient montré que, si CdIn204 présentait une sensibilité supérieure à celle de SnO2, cet oxyde était en revanche très fragilisé durant les étapes de fonctionnalisation, ce qui n'est pas le cas de SnO2 qui est un oxyde stable et robuste chimiquement. L'objectif du présent travail a été (i) d'améliorer les performances des capteurs à base de SnO2 en utilisant cette fois des films nanostructurés (1 ou 3D) afin de développer la surface spécifique, et (ii) d'étudier comment la topologie de surface influe sur le signal de détection de l'hybridation de l'ADN. Dans un premier temps, différentes nanostructures de SnO2 ont été élaborées par la technique d'électrodéposition que nous avons montée et mise au point de façon à obtenir des films reproductibles. La morphologie désirée des films –nanofils 1D ou matrice nanoporeuse 3D- a été obtenue en modifiant la procédure et les paramètres de dépôt. Leurs caractéristiques microstructurales, morphologiques, chimiques et électriques ont été déterminées par DRX, MEB, XPS et spectroscopie d'impédance. Puis, en vue du greffage covalent d'ADN, un procédé de fonctionnalisation multi-étape a été réalisé. Enfin, dans un troisième temps, la détection de l'hybridation d'ADN sans marquage, réalisée par spectroscopie d'impédance électrochimique sur les deux types de films nanostructurés, a été réalisée. En parallèle, afin de valider l'hybridation de l'ADN, la détection par microscopie à fluorescence, soit en mode épifluorescence, soit en mode confocal, a été menée. En comparaison des surfaces denses 2D de SnO2 (étude antérieure), les résultats ont montré une sensibilité supérieure, avec une limite de détection observée d'ADN de 2 nM, montrant l'importance d'avoir une surface développée. La structuration en nanofils est plus favorable que la matrice nanoporeuse en terme de sensibilité. Par ailleurs, en utilisant des ADN cibles, soit non complémentaires, soit possédant une ou deux mutations, nous avons pu montrer le caractère hautement sélectif de notre capteur dans le cas des deux types de nanostructures. Ce travail fortement expérimental a aussi permis de montrer l'importance de l'organisation structurale et morphologique du matériau sensible sur la réponse du signal à l'hybridation d'ADN. En effet, dans le cas des nanofils, comme dans celui des films denses avec surface 2D, le signal de réponse donne systématiquement une augmentation d'impédance. Cela s'explique par le phénomène d'effet de champ explicité plus haut. En revanche, dans le cas de la matrice naporeuse de SnO2, l'hybridation d'ADN entraine une diminution de l'impédance ... / For environmental in situ diagnostic, as well as for medical point of care diagnostic, quick andaffordable sensing devices are of importance. Label-free biosensors based on electrical orelectrochemical detection methods can provide such features. In previous studies, we havedemonstrated for the first time the feasibility of using semiconductive SnO2 2D dense films fornon-faradic electrochemical impedance DNA detection. The aim of the present study is (i) toimprove the sensing performances by using SnO2 nanostructures in order to benefit from highspecific surface, and (ii) to study the influence of the morphology and microstructure on theimpedimetric DNA detection signal.We performed the cathodic electrodeposition of SnO2 nanostructures. By changing relevantprocessing parameters, two kinds of nanostructures were deposited: 3D nanoporous films and 1Dnanowires. Both nanostructures have been characterized in terms of morphology, microstructureand electrochemical properties.Our results emphasize the importance of both the microstructural and morphological organizationson the impedimetric signal upon DNA hybridization. Opposite tendencies are found. DNAhybridization induces a decrease of the impedance in the case of 3D-nanoporous films, whereasan increase of impedance is obtained in the case of 1D NWs. Indeed, following the dimensionalityof the nanostructures, either external cause - ion transport - or internal cause - field effectphenomenon - can contribute to the impedance variation.The performances of the sensors have also been analyzed, namely: sensitivity, selectivity andreusability. Compared to the 2D dense and 3D nanoporous films, the 1D SnO2 nanowires are morefavorable in term of sensitivity, showing a detection limit of 2 nM.

Made available in DSpace on 2014-10-09T12:35:36Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:01Z (GMT). No. of bitstreams: 1 16967.pdf: 124292 bytes, checksum: 48d74296a6938d168fb793ec26259ca9 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2016-12-08T17:19:21Z (GMT). No. of bitstreams: 1 Pricyla Correa_Materiais.pdf: 3021159 bytes, checksum: 54c96d18b375a9b34266d9355ec7a293 (MD5) Previous issue date: 2013-11-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Calcium phosphate nanostructured bioceramics present themselves as biomaterials for bone tissue reconstruction. Among calcium phosphates, hydroxyapatite is the biomaterial with the closest resemblance of bone tissue crystalline structure, also presenting good bioactivity and biocompatibility. Hydroxyapatite stands out on researches as synthetic bone matrix and in the making of nanocomposite biomaterials. The interest in the elaboration of nanocomposite biomaterials is associated with their mechanical properties, morphology modification, microstructural architecture, grain‟s surface area and microporosity. Another factor to consider is related to improving open porosity, wettability and capillarity. This research aimed at the wet synthesis of a nanostructured calcium phosphate bone matrix for later elaboration of the hydroxyapatite matrix and hydroxyapatite/α-alumina sol-gel nanocomposites at 1, 2, 3 and 5% concentrations in nanometric α-alumina volume. The synthesis method for obtaining hydroxyapatite was the dissolution/precipitation process, involving liquid/solid CaO phase and phosphoric acid. This method allowed the obtainment of hydroxyapatite nanostructured powders composed of fine agglomerated particles. The elaboration of the nanocomposite powders was accomplished with the aid of a high-energy attrition mill. The powders of all compositions were then compacted and sintered at 1250ºC/2h, supplying HA/α-Al2O3 nanocomposite biomaterials. The presented results refer to morphological (SEM), mineralogical (XRD), chemical (FTIR) and particle size distribution (laser particle analysis method and theoretical calculation of particle 13 surface area for nanostructured powders) characterization. Mechanical properties, open porosity and density by theoretical method for the different biomaterial compositions obtained from sintering at 1250ºC/2h have also been determined. / As biocerâmicas nanoestruturadas de fosfatos de cálcio se apresentam como biomateriais de reparação de defeitos e da reconstrução do tecido ósseo. Dentre os fosfatos de cálcio a hidroxiapatita é o biomaterial que mais apresenta similaridade com a estrutura cristalina do tecido ósseo, também oferece boa bioatividade e biocompatibilidade. A hidroxiapatita se destaca nas pesquisas como matriz óssea sintética e na elaboração de biomateriais nanocompósitos. O interesse na elaboração de biomateriais nanocompósitos está associado às propriedades mecânicas, modificação da morfologia, da arquitetura microestrutural, da área superficial de grãos e de microporos. Outro fator a ser levado em consideração está relacionado a melhorar a porosidade aberta e a capacidade de molhabilidade e capilaridade. O presente trabalho de pesquisa teve como objetivo a síntese via úmida de uma matriz óssea de fosfato de cálcio nanoestruturada para posterior elaboração da matriz hidroxiapatita e dos nanocompósitos hidroxiapatita/alumina-α sol-gel nas concentrações de 1, 2, 3 e 5% em volume de alumina-α nanométrica. O método de síntese para a obtenção da hidroxiapatita deu-se pelo processo de dissolução/precipitação, envolvendo fase sólida/líquida de CaO e ácido fosfórico. Este método permitiu a obtenção de pós nanoestruturados de hidroxiapatita formados por finas partículas aglomeradas. A elaboração dos pós nanocompósitos foi realizada com ajuda de um moinho atritor de alta energia. Os pós de todas as composições foram então compactados e sinterizados à 1250°C/2h fornecendo os biomateriais nanocompósitos HA/Al2O3-α. Os resultados apresentados se referem aos estudos de caracterização morfológica (MEV), mineralógica (DRX), química (FTIR), da distribuição do tamanho de partículas, utilizando o método de análise de 11 partículas por laser, e cálculo teórico da área superficial das partículas para os pós nanoestruturados. Determinaram-se também as propriedades mecânicas, porosidade aberta e densidade hidrostática pelo método teórico para as diferentes composições de biomateriais obtidos da sinterização a 1250°C/2h.

Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-05-02T23:02:56Z No. of bitstreams: 1 PALOMA LIMA DE OLIVEIRA – DISSERTAÇÃO (PPGEQ) 2017.pdf: 2052604 bytes, checksum: eb8835fec6a57dfd944520382ff5fd82 (MD5) / Made available in DSpace on 2018-05-02T23:02:56Z (GMT). No. of bitstreams: 1 PALOMA LIMA DE OLIVEIRA – DISSERTAÇÃO (PPGEQ) 2017.pdf: 2052604 bytes, checksum: eb8835fec6a57dfd944520382ff5fd82 (MD5) Previous issue date: 2017-04 / Um método considerado eficiente para degradação de moléculas orgânicas recalcitrantes, como é o caso do agrotóxico diuron, é o processo de fotocatálise heterogênea (FH) utilizando TiO2. O emprego do TiO2 no processo fotocatálitico é geralmente na forma de pó constituído de partículas nanométricas, o que dificulta a sua recuperação e reutilização. Uma alternativa que permite recuperar o nanocatalisador do meio reacional por separação magnética é a síntese do mesmo associado a uma fase com boa propriedade magnética (CoFe2O4). Assim o presente trabalho teve como objetivo sintetizar nanoestruturas magnéticas, xTiO2:yCoFe2O4 nas proporções mássicas x:y 90:10; 70:30 e 50:50, para serem utilizadas como catalisadores no processo de degradação e mineralização do diuron padrão em solução aquosa por fotocatálise heterogênea. Para isso foram sintetizadas as amostras CoFe2O4 pelo método de combustão e TiO2 e xTiO2:yCoFe2O4 pelo método Pechini, que foram submetidas as caracterizações de difração de raios X com refinamento Rietvield, composição química por fluorescência de raios X e análise textural. A atividade fotocatalítica dos nanomateriais foi avaliada na fotodegradação e mineralização do diuron padrão por meio da quantificação da concentração final de diuron e do carbono orgânico total (COT). Os efeitos do pH e da concentração de catalisador foram estimadas por meio de um planejamento fatorial 22. As nanoestruturas magnéticas permitiram a separação do meio reacional por um campo magnético. Todos os nanomateriais sintetizados promoveram 100% de degradação do diuron. As maiores remoções de COT para os catalisadores magnéticos foram obtida com pH 3 e 0,5 mg/mL de catalisador e para o TiO2 foi com pH 5 e 0,3 mg/mL de catalisador. / A method considered efficient for the recalcitrant organic molecules degradation, such as diuron agrochemical, is the heterogeneous photocatalysis (FH) process using TiO2. The TiO2 in photocatalytic process is generally used in powder form consisting of nanometric particles, which makes difficult its recovery and reuse. An alternative that allows recovering the nanocatalyst from the reaction medium by magnetic separation is the synthesis of the same compound associated to a good magnetic property phase (CoFe2O4). Thus the present work had as objective to synthesize magnetic nanostructures, xTiO2:yCoFe2O4 in the mass proportions of x:y 90:10; 70:30 and 50:50 to be used as catalysts in the degradation and mineralization process of the standard diuron in aqueous solution by heterogeneous photocatalysis. In order to accomplish it, CoFe2O4 samples were synthesized by the combustion method and TiO2 and xTiO2: yCoFe2O4 were synthesized by the Pechini method, which were subjected to X-ray diffraction characterization with Rietvield refinement, chemical composition by X-ray fluorescence and textural analysis. The photocatalytic nanomaterials activity was evaluated in the photodegradation and mineralization of the standard diuron by quantifying the final diuron concentration and total organic carbon (TOC). The pH effects and the catalyst concentration were estimated through a factorial design. The magnetic nanostructures allowed the reaction medium separation by a magnetic field. All synthesized nanomaterials promoted 100% diuron degradation. The highest TOC removals for the magnetic catalysts were obtained with pH 3 and 0.5 mg/mL of catalyst and for TiO2 it was with pH 5 and 0.3 mg/mL of catalyst.

Neste trabalho, foram desenvolvidos filmes finos de composição SrTi1-xFexO3 (0,00≤ x ≤0,150) nanoestruturados visando sua aplicação como sensor de gás ozônio. Os filmes finos foram depositados através da técnica de deposição por feixe de elétrons (EBD) cujo alvo utilizado foram pastilhas obtidas a partir do pó cristalino SrTi1-xFexO3 (0,00≤ x ≤0,150) sintetizadas através do método dos precursores poliméricos. Foi observado a partir das analises termogravimétrica e térmica diferencial que a incorporação de ferro no sistema diminui a temperatura de queima do pó precursor, sugerindo que o ferro atua como catalisador na cadeia polimérica. Os filmes depositados por DFE apresentam-se no estado amorfo sendo necessário um tratamento térmico ex-situ para que a fase cristalina desejada seja obtida. Todos os filmes apresentaram uma boa aderência aos diferentes tipos de substratos utilizados. Após o processo de cristalização, os filmes depositados sobre diferentes substratos foram caracterizados através das técnicas de difração de raios-X, espectroscopia UV-Vis e microscopia de força atômica (MFA). Foi observado que um aumento na temperatura de tratamento térmico dos filmes leva a um aumento no grau de cristalização e a uma diminuição no valor da energia de gap, calculada a partir dos espectros UV-VIS. A analise por MFA mostrou que a mudança do tipo de substrato utilizado não influencia as propriedades estruturais e microestruturais dos filmes. Através da realização de medidas de resistência elétrica, observou-se que os filmes cristalinos submetidos a um tratamento térmico ex-situ a 500oC por 4 horas apresentaram uma boa sensibilidade ao gás ozônio sendo possível detectar a presença de até 75 ppb de ozônio. / In this study, nanostructured thin films of SrTi1-xFexO3 (0.00 ≤ x ≤ 0.150) compositions were prepared looking their application as ozone gas sensor. The thin films were deposited using the technique of electron beam deposition (EBD) whose targets were obtained from polycrystalline SrTi1-xFexO3 (0.00 ≤ x ≤ 0.150) powders synthesized by the polymeric precursor method. It was observed from the thermogravimetric and differential thermal analysis that the incorporation of iron in the system decreases the calcination temperature of the precursor powders, suggesting that the iron acts as a catalyst in the polymer chain. The as obtained films deposited by EBD present an amorphous state being necessary a ex-situ heat treatment to obtain the desired crystalline phase. All films showed good adhesion to different substrates. After the crystallization process, the films deposited on different substrates were characterized through X-ray diffraction, UV-Vis spectroscopy and atomic force microscopy (AFM) trechniques. It was observed that an increase in the annealing temperature of the film results in an increase in the degree of crystallization and a decrease in the value of band gap energy, which was calculated from the UV-VIS spectra. The AFM analysis showed that changing the type of substrate does not influence the structural properties and microstructure of the films. By carrying out measurements of electrical resistance, it was observed that the crystalline films subjected to a ex-situ heat treatment at 500oC for 4 hours showed a good sensitivity to the ozone gas being possible to detect the presence of up to 75 ppb ozone.

Semicondutores orgânicos têm atraído cada vez mais atenção da comunidade científica e de indústrias. O grande interesse se divide entre a riqueza de fenômenos físicos e químicos a serem estudados e o seu grande potencial de aplicação tecnológica nas mais diversas áreas: diodos emissores de luz (OLEDs), células solares e fotodiodos, transistores, biosensores, sensores de radiação ionizante, entre outros. O objetivo deste trabalho foi de contribuir para o avanço de duas áreas de aplicação, ambas relacionadas com a interação de radiação eletromagnética com a matéria: células solares e dosimetria de radiação gama. Na área de células solares, foram explorados dois dos principais limitadores do aumento de eficiência de conversão de potência: a falta de materiais com absorção na região em que o Sol emite mais fótons (infravermelho próximo (NIR)) e a dificuldade de controle da morfologia interna das células. Foi demonstrado um novo conceito de fabricação de células solares através da nanoestruturação de filmes finos poliméricos. A metodologia de estruturação se baseia no processo de separação de fases em blendas poliméricas durante o processo de deposição por spin-coating e a subseqüente remoção de uma das componentes. Assim é possível obter uma camada ativa cobrindo todo o substrato e apresentando ondulações na superfície que podem ser variadas desde alguns nanômetros de altura e largura até micrômetros. O processo de nanoestruturação é discutido e dispositivos fotovoltaicos foram produzidos cobrindo filmes nanoestruturados de MEH-PPV com fulereno C60. A eficiência de conversão de potência destas células é três vezes maior do que o melhor resultado já reportado para este par de materiais até o momento e atinge quase 3% sob irradiação monocromática. Utilizando corantes cianinos, dispositivos fotovoltaicos e fotodiodos com resposta desde no visível até o infravermelhor próximo (~1000 nm) foram demonstrados e foi observado um papel importante dos íons móveis presentes nos corantes. Finalmente, foi demonstrada a aplicabilidade de um corante polimerizado como dosímetro de radiação gama. A faixa de operação do dosímetro pode ser alterada variando-se a concentração da solução do corante, que poderia ser utilizado na região de doses de irradiação de alimentos. / Organic semiconductors have atracted much attention from the scientific community and from the industry. The large interest is divided between the rich number of basic physical and chemical phenomena to be investigated and the great technological potential for application in different areas, such as light emitting diodes (OLEDs), solar cells, photodiodes, transistors, biosensors, ionizing radiation sensors, among others. The subject of this work was to contribute to a deeper understanding of two areas of application, both related to the interaction of electromagnetic radiation with matter: solar cells and gamma ray dosimetry. In the area of solar cells, the lack of materials absorbing in the near infrared (NIR) and the poor control of the morphology of the active films are limiting factor to increasing device efficiency. Therefore both this aspects were explored. A new concept of organic solar cell fabrication was presented based on the anostructuration of polymeric thin films. The methodology is based on phase separation of polymer blends during spin-coating followed by the selective removal of one component. This allows the controlled formation of thin films with characteristic features varying from a few nanometers to micrometers. The effects of molecular weigth, solvent and relative composition were investigated and discussed based on the analysis of AFM images and phase separation models. Devices using structured MEH-PPV layers, covered by C60 were fabricated and showed white light power conversion efficiencies (?) up to 400 % higher than a flat double layer device. Monochromatic ? achieved 2.95 % (480 nm), three times higher than the best reported value for this material combination so far. Using cyanine dyes, photovoltaic devices and photodiodes active in the NIR (~1000 nm) were demosntrated and an important effect of movable ions present in the dyes was observed. Finally, the application of a polymerized dye as gamma ray dosimeter was demonstrated. The operation range can be altered by varying the concentration of polymer in solution, and are useful in the range of low dose food irradiation.

Orientador: Cecilia Amelia de Carvalho Zavaglia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-11T17:34:54Z (GMT). No. of bitstreams: 1 Rodrigues_LeonardoRibeiro_M.pdf: 5401743 bytes, checksum: 54304af70cd892b8330f9b76b6da4067 (MD5) Previous issue date: 2008 / Resumo: A hidroxiapatita e a titânia são cerâmicas muito pesquisadas no mundo inteiro, graças às suas excelentes qualidades em diversas áreas, porém neste trabalho o foco foi a sua utilização como biomateriais. Neste trabalho é apresentada a síntese e a caracterização de hidroxiapatita e titânia nanoestruturadas e a fabricação e caracterização de compósitos a partir destes materiais. Os métodos de obtenção de hidroxiapatita foram as rotas sol-gel convencional, sol-gel com sacarose e sol-gel com glicose. Para a síntese da titânia foi utilizado um método desenvolvido no laboratório. Foram utilizados na caracterização da hidroxiapatita: difração de raios X associado com a equação de Scherrer, fluorescência de raios X, microscopia eletrônica de varredura e ensaio mecânico de compressão. Para a titânia foram utilizados os mesmos tipos de caracterização, porém com a adição da espectroscopia Raman. Os resultados foram excelentes podendo ser destacados: baixo custo dos reagentes, facilidade de realização dos processos de síntese, pequenos nanocristalitos com 52 a 100nm para hidroxiapatita e 27 a 62nm para a titânia. O compósito apresentou boa distribuição entre as partículas de hidroxiapatita e titânia e uma evidente melhora na resistência à compressão quando comparado com o pó compactado de hidroxiapatita sem reforço / Abstract: Hydroxyapatite and titania are ceramics which have been given a lot of attention around world because of their outstanding properties in multiple fields such as the one of biomaterials which is the aim of this work. The synthesis and caracterization of nanostructured hydroxyapatite and titania, for composites fabrication is presented in this work. The synthetic routes employed for the hydroxyapatite synthesis were the conventional sol-gel process, the sol-gel process with sucrose, and sol-gel process with glucose. The synthesis of titania was performed by a method developed in the laboratory. Hydroxyapatite characterization was made by: X-ray diffraction associate with the Scherrer equation, X-ray fluorescence, scanning electron microscopy and compression mechanical test. For titania it was used the same characterization procedures, however, they were complemented with Raman spectroscopy. From the results it could be concluded that the synthesis methods employed were efficient in obtaining nanocrystallites sized from 52 to 100nm and from 27 at 62nm for hydroxyapatite and titania, respectively. On the composite formulation hydroxyapatite and titania particles were well distributed and its mechanical resistance were higher than the one obtained by the hydroxyapatite without the titania reinforcement / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica