Orientador: Iris Concepcion Linares de Torriani / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T13:36:14Z (GMT). No. of bitstreams: 1 Aguero_OscarEnrique_D.pdf: 9568417 bytes, checksum: db4b9632a94f1d1cb2691c4eeb1404ec (MD5) Previous issue date: 2007 / Resumo: Uma serie de compostos ineditos ou pouco estudados foram sintetizados e as propriedades físicas foram estudadas usando difração de raios X e medidas magneticas em função da temperatura. Neste tipo de compostos as propriedades estruturais estão fortemente correlacionadas com as propriedades magnéticas e de transporte. Neste trabalho apresentaremos a síntese, caracterização estrutural e magnética de ligas metálicas nanoestruturadas de Cu-Fe, compostos intermetálicos R3M4Sn13(R= terra rara, M= Co e Ir), e cobaltitas (Nd1-xC axCoO3 e GdBaCo2O5,5). Parâmetros de cela, tamanho de domínios e tensões de ligas nanoestruturadas Cu1-xFex (0<x<0,5) preparadas por ball-milling foram determinados usando difração de pó. Todos as amostras apresentam a estrutura FCC do Cu. Os parâmetros de cela aumentam com x. Usando métodos de análise do perfil de difração (largura integrada e Warren-Averbach), determinamos o tamanho dos domínios cristalinos e tensões na rede. O tamanho dos domínios decresce e as tensões aumentam com x. As estruturas cristalinas dos compostos R3M4Sn13(R= terra rara, M= Co e Ir) foram determinadas por difração de monocristais à temperatura ambiente. Todos os compostos R3C o4Sn13 e Eu3I r4Sn13 cristalizam com uma cela cúbica Pm-3n, com parâmetros de cela a~ 9,5- 9,8 Å. Os compostos R3I r4Sn13 (R= La, Ce, Pr, Nd) apresentam uma superestrutura cúbica de corpo centrado com a¿~2a. Os compostos de Yb e Eu mostram um comportamento anômalo associado a um estado de valência diferente das outras terras raras. Estudos de difração de pó a baixas temperaturas para os compostos R3Co4Sn13 (R= La, Ce, Pr, Nd e Gd) mostram uma transição abaixo de T=150 K para uma superestrutura cúbica de corpo centrado com parâmetro de cela a¿~2a. Os compostos R3Ir4Sn13 não apresentam transições de fase até 20 K. As propriedades estruturais e magnéticas das cobaltitas Nd1-xCaxCoO3 (0 =x =0,4), foram estudadas usando difração de pó, magnetização dc e susceptibilidade ac em função da temperatura (2-800 K). Todos os compostos cristalizam com uma estrutura ortorrômbica (Pnma) no intervalo de temperatura estudado (20-800 K). Para x =0,1 o sistema mostra um comportamento paramagnético até 2 K, com os íons Co3+ e Co 4+ em estados de baixo spin (LS) para T<180 K. Para 0,2 =x =0,4, duas transições magnéticas são observadas para T<60 K. Estas transições estão associadas a estados de "spin glass" ou "cluster glass". Um diagrama de fases magnéticas e de estados de spin foi construído e comparado com outros sistemas similares. Foi realizada a síntese do composto GdBaCo2O5,50 e estudadas as propriedades estruturais e de transporte em função da temperatura (2-800 K). Sucessivas transições de fase magnéticas foram observadas a: TPM= 70 K, TN~ 260 K; TC~ 273 K. Observamos uma transição metal isolante a TMI~ 360 K, simultânea com uma transição de spin dos íons de Co3+ . Os resultados magnéticos são compatíveis com estados de spin: 50%Co3+ (IS)+50% Co3+ (LS) para T<TMI e 50% Co3+ (IS)+50% Co3+ (HS) para T > TMI. Estudos estruturais usando difração de pó com fonte convencional e luz de síncrotron, mostram que a TMI uma transição de spin LS ÎHS ocorre para os íons Co3+ nos octaedros. Uma transição ortorrômbica-tetragonal, de tipo ordem-desordem, foi observada a TOD~ 760 K / Abstract: A series of new compounds have been synthesized and their physical properties studied using X-ray diffraction and magnetic measurements as a function of temperature. In this type of compounds, structural properties are strongly correlated with their magnetic and transport properties. In this work we present details of the synthesis as well as the structural and magnetic characterization of nanostructured metallic alloys (Cu-Fe), intermetallic compounds of the type R3M4Sn13 (R=rare earth, M= Co, Ir), and the cobaltates Nd1-xCaxCo03 and GdBaCo2O5,5. The lattice parameters, crystallite size and lattice strain of nanostructured Cu1-xFex(0< x <0,5) alloys prepared by the ball milling method were determined from X-ray powder diffraction analysis. All samples present the Cu FCC structure. The lattice parameter of the Cu1-xFex phases increases with x. The X-ray diffraction peaks were analyzed using the Warren-Averbach and Integral Breadth methods. The crystallite size decreases and the lattice strain increases with Fe concentration. Crystal structures of the R3M4Sn13 (R= rare earth, M=Co, Ir) intermetallic compounds were determined from single crystal X-ray diffraction at room temperature. All R3Co4Sn13 and Eu3Ir4Sn13 compounds crystallize in the cubic Pm-3n space group with cell parameters a~9,5-9,7 ÿ. The R3IrSn13(R= La, Ce, Pr, Nd) compounds present a body centered cubic superstructure with aÂ' ~2a. In this series, the Yb and Eu compounds exhibit an anomalous behavior associated to valence states different from those of the other rare earths. Low temperature X-ray powder diffraction studies for R3Co4S n13(R= La, Ce, Pr, Nd and Gd) show a phase transition below 150 K from a simple cubic to a body centered cubic superstructure with cell parameter aÂ'~ 2 a. The temperature of the phase transition decreases with the rare earth ionic radii. No phase transitions were observed for the R3Ir4Sn13 series for temperatures down to 20 K. The structural and magnetic properties of the cobaltates Nd1-xCaxCoO3(0 =x =0,4), were studied using powder X-ray diffraction, dc magnetization and ac susceptibility measurements as a function of temperature (2-800 K). All compounds crystallize with an orthorhombic (Pnma) structure in the temperature range (20- 800 K). For x =0,1 the Nd1-xCaxCoO3system shows a paramagnetic behavior down to 2 K, with the Co3+e Co4+ions in low spin state (LS) for T<180 K. For 0,2 =x =0,4, two magnetic transitions were observed for T<60 K. These transitions are associated to a spin or cluster glass states. A magnetic phase and spin state diagram was constructed for comparison with similar systems. The compound GdBaCo2 O5.50was synthesized and the structural and transport properties were studied as a function of temperature [2-800 K]. Successive magnetic phase transitions were observed: TPM= 70 K, TN~ 260 K; TC~ 273 K. A metal-insulator transition is observed at TMI~ 360 K, with a simultaneous spin transition of the Co 3+ions. The magnetic measurements results are compatible with the spin states 50%Co3+(IS)+50% Co3+(LS) for T<TMI and 50%Co3+(IS)+50%Co3+(HS) for T>TMI. Structural studies using powder diffraction with a conventional X-ray source and synchrotron radiation show that the LS Ã?HS spin state transition occurs only for the Co3+ions in the octahedrons. An orthorhombic-tetragonal transition of the order-disorder type was observed at TOD~ 760 K / Doutorado / Física da Matéria Condensada / Doutor em Ciências

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / à medida que o limite de miniaturizaÃÃo da eletrÃnica baseada no silÃcio aproxima-se do seu limite, alternativas em estado sÃlido devem ser investigadas na busca da diminuiÃÃo da escala de tamanho de dispositivos operacionais, ao mesmo tempo em que se deve considerar problemas de crescente interessse como dissipaÃÃo de calor e ruÃdo associado com a baixa dimensionalidade. Nesta busca, jà està claro que nanosistemas semicondutores de carbono sÃo candidatos de primeiro pelotÃo para comporem os blocos bÃsicos para dispositivos em escala atÃmica e molecular. Grafeno e nanotubos de carbono sÃo os sistemas mais estudados desta classe de estruturas que se estende por uma vasta coleÃÃo de sistemas. Estas nanoestruturas de carbono apresentam uma riqueza de propriedades fÃsicas e quÃmicas que se reflete no enorme nÃmero de artigos cientÃficos tendo esses sistemas como foco. Apesar de a ciÃncia das nanoestruturas de carbono ainda ter um longo caminho pela frente antes de alcanÃar as prateleiras das lojas depois de ter sido transformada em tecnologia, a comunidade cientÃfica tem caminhado rapidamente no sentido de entender e controlar tais sistemas de modo a diminuir esta distÃncia. Nesta tese nÃs realizamos um estudo teÃrico das propriedades eletrÃnicas e de transporte de um nÃmero de nanoestruturas de carbono, tais como nanosistemas toroidais e nanofitas de carbono de arranjo complexo. Nossos cÃlculos de estrutura eletrÃnica sÃo baseados em um modelo tight-binding que inclui um Hamiltoniano de Hubbard para descrever a influÃncia do spin sobre os estados eletrÃnicos. As propriedades de transporte eletrÃnico foram calculadas utilizando o formalismo de Landauer e o mÃtodo de funÃÃes de Green para determinar a transmitÃncia quÃntica em sistemas em nanoescala. Parte destes cÃlculos foram realizados com pacotes computacionais desenvolvidos especialmente para esta tese. Em particular, nÃs desenvolvemos uma extensÃo de um algorÃtmo eficiente para o cÃlculo de funÃÃo de Green em uma infraestrutura computacional em paralelo. Nanotoroides de carbono apresentam estrutura eletrÃnica especÃfica se comparados aos nanotubos de carbono, jà que sua geometria impÃe um grau suplementar de confinamento espacial. Como consequÃncia, condiÃÃes adicionais devem ser impostas à sua geometria para que a estrutura seja metÃlica. Aqui nos analizamos nanotoroides de carbono a partir de duas perspectivas diferentes: sistemas de dois terminais com um Ãngulo variÃvel entre os eletrodos e estruturas de mÃltiplos terminais. Esses sistemas possuem potencial para serem aplicados em nanoeletrÃnica graÃas à sua geometria particular que permite que a corrente flua atravÃs do sistema por diferentes caminhos eletrÃnicos. Isso resulta em propriedades de transporte interessantes, as quais sÃo ditadas por efeitos de interferÃncia eletrÃnica que variam com o Ãngulo entre os eletrodos e com os detalhes da estrutura atÃmica da junÃÃo nanotoroide-terminal. NÃs mostramos que a presenÃa de mÃltiplos terminais acrescenta novos aspectos ao transporte eletrÃnico destes toroides jà que o nÃmero de possibilidades para o fluxo eletrÃnico cresce rapidamente com o nÃmero de eletrodos. Observa-se que a condutÃncia à caracterizada por um conjunto de picos resonantes que sÃo relacionados com caminhos eletrÃnicos especÃficos. Estes resultados sÃo racionalizados em termos de uma sÃrie de regras para se determinar o caminho para a corrente elÃtrica como uma funÃÃo da energia do elÃtron incidente. Na segunda parte da tese, nÃs estudamos as propriedades fÃsicas de uma classe de fitas de carbono as quais nÃs chamamos de fitas sinuosas (ou simplesmente wiggles, em inglÃs). A estrutura atÃmica destas wiggles pode ser descrita por um conjunto reduzido de fatores jà que elas podem ser construÃdas utilizando-se fitas de carbono de borda reta como blocos bÃsicos. NÃs mostramos que essas wiggles de carbono apresentam um conjunto de propriedades eletrÃnicas e magnÃticas ainda mais amplo quando comparadas com os seus constituintes bÃsicos (fitas de carbono de borda reta). Isso à especialmente devido à formaÃÃo de domÃnios nas bordas, resultantes da sucessiva repetiÃÃo de setores de fitas retas paralelas e obliquas ao longo da direÃÃo periÃdica da wiggle. NÃs demonstramos que as wiggles de carbono apresentam mÃltiplos estados magnÃticos que podem ser explorados para se manipular as propriedades fÃsicas desses sistemas. Estes diferentes estados magnÃticos resultam em propriedades eletrÃnicas e de transporte distintas, de modo que a corrente eletrÃnica pode ser controlada pela escolha de valores especÃficos da energia do elÃtron incidente no sistema, assim do spin eletrÃnico e do estado magnÃtico da wiggle. Essas propriedades tornam as nanowiggles potenciais candidatas para novas aplicaÃÃes em nanodispositivos. Finalmente, nos esperamos que o trabalho apresentado nesta tese constitua uma importante contribuiÃÃo para a investigaÃÃo das propriedades fÃsicas de nanoestruturas de carbono. NÃs mostramos que nanotoroides e nanowiggles de carbono apresentam uma sÃrie de novas propriedades que podem tornar possÃvel o seu uso em nanoeletrÃnica. à medida que estudos experimentais em nanomateriais de carbono tÃm sido desenvolvidos a passos largos, nÃs projetamos que os resultados apresentados nesta tese se tornarÃo uma Ãtima oportunidade para se confrontar teoria e experimento na proposta de novos dispositivos em nanoescala com propriedades eletrÃnicas e de transporte especÃficas.

Na primeira parte desta dissertação, nos concentramos na utilização de uma abordagem baseada na remoção oxidativa controlada de sementes/núcleos promovida pela adição de HCl na síntese poliol de nanofios de prata (Ag). Isto possibilitou um controle fino sobre a espessura dos nanofios gerados na faixa de de 65 a 765 nm, no qual as larguras obtidos apresentaram um aumento linear em função do aumento na concentração de HCl utilizado na reacção. Embora a largura também se mostrou dependente de outros parâmetros experimentais, tais como a concentração de AgNO3 e polivinilpirrolidona (PVP) e temperatura, remoção oxidativa promovida por HCl possibilitou o controle sobre uma faixa de tamanhos mais ampla. Também investigamos as propriedades ópticas dos nanofios de Ag em função do seu tamanho e sua aplicabilidade como substratos para detecção atraves do fenômeno de espalhamento Raman intensificado por superfície (SERS). Na segunda parte deste trabalho, nanotubos de Ag-Au, Ag-Pt e Ag-Pd contendo morfologias de superfície controladas foram obtidos através da reação de substituicão galvânica entre os nanofios de Ag e íons AuCl4-, PtCl62-, e PdCl42-, respectivamente. Nesse caso, superfícies lisas foram obtidas a 100 oC enquanto superfícies rugosas foram observadas a temperatura ambiente. Mostramos ainda que superfícies lisas também puderam ser obtidas usando-se uma solução saturada de NaCl como solvente durante a reação galvânica. Na terceira parte deste trabalho, investigamos o efeito da excitação da ressonância plasmônica de superfície (SPR) nos nanofios de Ag sobre a atividade catalítica frente a redução do 4-nitrofenol. Contudo, nossos resultados mostraram um queda da atividade catalítica pela excitação SPR, mostrando que a excitação do SPR também pode levar a efeitos detrimentais sobre a atividade catalítica dependendo do mecanismo de reação estudado e natureza de intermediários na etapa determinante da velocidade de reação. Como as propriedades de nanoestruturas metálicas são fortemente dependentes de tamanho, forma e composição, acreditamos que os resultados apresentados aqui relatados podem ter implicações importantes para o design de nanomateriais unidimensionais com características/propriedades desejadas para aplicações em diversas áreas, incluindo óptica e catalise. / In the first part of this thesis, we focused on the utilization of an approach based on controlled oxidative etching for the removal of seeds/nuclei promoted by the addition of HCl in the polyol synthesis of silver nanowires (Ag). This allowed a precise control over the width of the Ag nanowires in the 65-765 nm range. In this case, the widths showed a linear increase with the HCl concentration employed in the reaction. While the width was also dependent on other experimental parameters such as the concentration of AgNO3 and polyvinylpyrrolidone (PVP) as well as the temperature, oxidative etching promoted by HCl enabled the control over a wider range of sizes. We also investigated the optical properties of Ag nanowires as a function of their size and their applications as substrates for surface enhanced Raman scattering (SERS). In the second part of this work, Ag-Au, Ag-Pt, and Ag-Pd nanotubes displaying controlled surface morphologies were obtained by galvanic replacement reaction between the Ag nanowires and AuCl4-, PtCl62-, e PdCl42- ions, respectively. In this case, while smooth surfaces were obtained at 100 °C, rough surfaces were observed at room temperature. We also showed that smooth surfaces could be obtained by using a saturated solution of NaCl as the solvent during the galvanic reaction. Finally, in the third part of this study, we investigated the effect of surface plasmon resonance (SPR) excitation on Ag nanowires over the catalytic activity towards the 4-nitrophenol reduction. However, our results indicated a drop in catalytic activity with SPR excitation, showing that the SPR excitation can also lead to detrimental effects on the catalytic activity depending on the nature of the chemical reaction mechanism and intermediates in the rate-determining step of the reaction. As properties in metallic nanostructures are strongly dependent on size, shape and composition, we believe that the results reported here may have important implications for the design of one-dimensional nanomaterials design with desired features/properties for applications in various fields that include optics and catalysis.

Orientador: Ronei Jesus Poppi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-24T17:49:24Z (GMT). No. of bitstreams: 1 MamianLopez_MonicaBenicia_D.pdf: 23169913 bytes, checksum: cf40556e2a6f09ccb3f2b2bf36b0b234 (MD5) Previous issue date: 2014 / Resumo: Foi utilizada a espectroscopia Raman amplificada por superfície SERS, em conjunto com ferramentas quimiométricas de resolução de curvas e alguns algoritmos complementares, em quatro aplicações analíticas que incluíram imagem SERS, monitoramento de um sistema dinâmico multicomponente e quantificação de nicotina e moxifloxacina em urina. Como intensificadores do sinal foram empregados um sistema coloidal de ouro, sintetizado segundo o método de Lee-Miesel e um substrato sólido comercial de ouro nanoestruturado / Abstract: In this work, four chemometric-assisted analytical procedures using surface-enhanced Raman spectroscopy are proposed. A multivariate curve resolution method in conjuction with others algorithms were employed to quantify the alkalloid nicotine in presence of two related compounds; determinate the antibiotic moxifloxacin in urine and to study its photolyitic degradation. Besides, SERS imaging was applied to study the paracetamol distribution in polymeric films. As SERS enhancers were used colloidal gold and a nanostructured gold substrate / Doutorado / Quimica Analitica / Doutora em Ciências

Orientador: Monica Alonso Cotta / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-04T02:49:32Z (GMT). No. of bitstreams: 1 Bortoleto_JoseRobertoRibeiro_D.pdf: 16802950 bytes, checksum: 1ef2bf92db0b00f30e5db9c5e3e3f34d (MD5) Previous issue date: 2005 / Resumo: Neste trabalho estudamos os mecanismos de crescimento durante a epitaxia de estruturas III-V baseadas na liga InP. Em particular, o principal objetivo foi correlacionar os mecanismos cinéticos durante a nucleação de nanoestruturas auto-formadas com as propriedades estruturais da camada que serve de substrato. Todas as amostras foram crescidas usando um sistema de epitaxia por feixe químico (CBE). De forma geral as amostras foram caracterizadas usando microscopia de força atômica (AFM), microscopia eletrônica de transmissão (TEM), difração de elétrons de alta energia (RHEED) e difração de raios-X. Na primeira parte deste trabalho correlacionamos as mudanças morfológicas nos filmes homoepitaxiais de InP com o padrão de RHEED exibido durante o crescimento epitaxial. Mostramos que as mudanças morfológicas de 3D para 2D com os parâmetros de crescimento estão diretamente relacionadas com as reconstruções superficiais 2x1 e 2x4, respectivamente. Além disso, indicamos que a formação de defeitos morfológicos é devido à dimerização In-P, através da ativação local do mecanismo de bias na difusão. Por outro lado, também investigamos o efeito dos parâmetros de crescimento (temperatura, taxa de crescimento e quantidade de material) na nucleação e auto-formação de ilhas de InP sobre InGaP/GaAs. Na segunda parte desta tese concentramos nossa atenção no efeito das propriedades da camada buffer de InGaP sobre nanoestruturas auto-formadas, principalmente sobre a sua organização espacial. Para tanto, em primeiro lugar, investigamos as propriedades de bulk da liga de InGaP e a dependência com os parâmetros de crescimento. Nossos resultados mostram que o InGaP exibe tanto ordenamento atômico de rede quanto modulação de composição. Estes dois fenômenos estão correlacionados com o tipo de reconstrução superficial. Em específico, a liga de InGaP apresenta ordenamento CuPtB quando a superfície exibe reconstrução superficial 2x1, conforme descrito na literatura. Por outro lado, a reconstrução superficial 2x4 desempenha um papel importante no fenômeno de modulação de composição. De fato, tanto a modulação de composição quanto a morfologia superficial do filme depende dos mecanismos cinéticos de superfície, que envolvem tanto os átomos adsorvidos de In quanto de Ga. Por fim mostramos que a modulação de composição na liga de InGaP pode organizar espacialmente a nucleação de ilhas de InP em uma rede quadrada. Além disso, mostramos que é possível criar redes bidimensionais de pontos quânticos de InAs/GaAs a partir do arranjo espacialmente ordenado das ilhas de InP/InGaP / Abstract: In this work we study the growth mechanisms during epitaxy of III-V structures based on InP. The main goal was to correlate the kinetic mechanisms during nucleation of self-assembled nanostructures with the bulk properties of the buffer layer. All samples were grown by chemical beam epitaxy (CBE) and characterized using atomic force microscopy (AFM), transmission electron microscopy (TEM), reflection high-energy electron diffraction (RHEED) and X-ray diffraction. In the first part of this work we correlate the morphological changes in homoepitaxial InP films with the RHEED pattern during growth process. We show that the morphological transition from 3D to 2D with growth parameters is related to changes in surface reconstruction, from 2x1 to 2x4. Moreover, we point out that the formation of morphological defects is due to mixed In-P dimerization, via the local activation of the diffusion bias mechanism. On the other hand, we also investigate the influence of the growth parameters (temperature, growth rate and amount of deposited material) on the nucleation and selfassembly of InP islands grown on InGaP/GaAs layers. In the second part of this work we concentrate our attention on the InGaP bulk properties, and their effect on the self-assembled InP nanostructures, mainly regarding their spatial ordering. In this way, we first investigate the dependence of InGaP bulk properties with the growth parameters. Our results show that our InGaP layers exhibit atomic ordering as well as compositional modulation. Both phenomena are correlated to the surface reconstruction exhibited by the InGaP surface during growth process. The InGaP alloy presents CuPtB atomic ordering when the RHEED pattern shows 2x1 reconstruction, in agreement with reports in literature. On the other hand, the 2x4-type reconstruction plays an important role in the compositional modulation phenomena. Actually, both compositional modulation and surface morphology of InGaP films depend on surface kinetic mechanisms, and thus on In and Ga adatom mobilities. At last we show that the compositional modulation in the InGaP alloy can be used to organize spatially the InP islands in a square lattice. Moreover, we point out that it is possible to produce bidimensional lattices of InAs/GaAs quantum dots starting from a template of laterally organized InP/InGaP nanostructures / Doutorado / Física da Matéria Condensada / Doutor em Ciências

Cette thèse présente un banc d’écriture de réseaux de diffraction de grande surface dont la période peut varier de 100 nm à plusieurs micromètres. Le principe est basé sur l’écriture au vol qui permet d’écrire des longs réseaux en balayant continûment un substrat recouvert de résine photosensible sous un interférogramme de petite dimension créé par un masque de phase. Deux types de masques ont été fabriqués. Le premier, pouvant être décrit comme un interféromètre de type Mach-Zehnder monolithique, présente l’intérêt d’écrire des réseaux de grandes périodes sans limite supérieure. Il est composé de trois réseaux de diffraction, écrits sur la même face d’un substrat épais grâce à destechniques standards de lithographie (e-beam, gravure RIE) accessibles lors d’un échange à l’UEF àJoensuu. A la longueur d’onde 442 nm, ce masque a permis d’écrire un réseau de période de 2 µmde grande dimension à l’aide d’une nappe de lumière divergente. Le second type de masque est monolithique en matériau haut indice. Il est utilisé en immersion à la longueur d’onde de 244 nm; des réseaux de période de 100 nm ont été écrits. La structure capable de supprimer l’ordre zéro transmis a été modélisée et les masques ont été fabriqués par trois partenaires européens du réseau d’excellence NEMO. La gravure du LuAG a également été étudiée en vue de fabriquer un masque de phase pour la longueur d’onde 193 nm. Afin d’écrire des réseaux larges et homogènes, une étude des différentes techniques d’élargissement de faisceau a été réalisée en vue de disposer d’une ligne de lumière avec un profil d’intensité homogène dit « top-hat », et une méthode de fabrication d’un long masque de phase a été développée / This PhD thesis presents a bench capable to write highly coherent diffraction gratings on a large area (potentially one square meter) with periods varying from 100 nm to several micrometers. The strategy is based on the “write on the fly” method, which allows writing long and stitchingless gratings by scanning a photoresist-coated substrate under a small area interferogram generated by a phase mask. The main object of this thesis concerns the design of the phase-mask. Two different types have been developed. The first type can be described as a monolithic Mach-Zehnder interferometer comprising three diffraction gratings at the same side of a thick fused silica substrate. This approach has the advantage of writing large periods without any upper limitation. Standard lithography techniques (e-beam, RIE) have been used to fabricate the mask during a two months stay at UEF at Joensuu. At the wavelength of 442 nm, a large 2 µm period grating has been made with exposure by a divergent beam. The second type of mask is binary and made in a layer of high refractive index material. It has been used at the 244 nm wavelength and under immersion to write a 100 nm period grating. The modeling was performed to find the optimal structure capable of suppressing the zeroth transmitted order. The masks were made by three European partners within the Network of Excellence NEMO. The etching of LuAG has also been studied in view of making a 193 nm phase-mask. To write large and homogeneous gratings, various methods of beam expansion were compared to generate a light line with a homogeneous intensity profile (top-hat). Solutions for the fabrication of long phase-masks have also been demonstrated

Complex magnetic oxides represent a unique intersection of immense technological importance and fascinating physical phenomena originating from interwoven structural, electronic and magnetic degrees of freedom. The resulting energetically close competing orders can be controllably selected through external fields. Competing interactions and disorder represent an additional opportunity to systematically manipulate the properties of pure magnetic systems, leading to frustration, glassiness, and other novel phenomena while finite sample dimension plays a similar role in systems with long-range cooperative effects or large correlation lengths. A rigorous understanding of these effects in strongly correlated oxides is key to manipulating their functionality and device performance, but remains a challenging task. In this dissertation, we examine a number of problems related to intrinsic and extrinsic low dimensionality, disorder, and competing interactions in magnetic oxides by applying a unique combination of standard magnetometry techniques and unconventional magnetocaloric effect and transverse susceptibility measurements. The influence of dimensionality and disorder on the nature and critical properties of phase transitions in manganites is illustrated in La0.7Ca0.3MnO3, in which both size reduction to the nanoscale and chemically-controlled quenched disorder are observed to induce a progressive weakening of the first-order nature of the transition, despite acting through the distinct mechanisms of surface effects and site dilution. In the second-order material La0.8Ca0.2MnO3, a strong magnetic field is found to drive the system toward its tricritical point as competition between exchange interactions in the inhomogeneous ground state is suppressed. In the presence of large phase separation stabilized by chemical disorder and long-range strain, dimensionality has a profound effect. With the systematic reduction of particle size in microscale-phase-separated (La, Pr, Ca)MnO3 we observe a disruption of the long-range glassy strains associated with the charge-ordered phase in the bulk, lowering the field and pressure threshold for charge-order melting and increasing the ferromagnetic volume fraction as particle size is decreased. The long-range charge-ordered phase becomes completely suppressed when the particle size falls below 100 nm. In contrast, low dimensionality in the geometrically frustrated pseudo-1D spin chain compound Ca3Co2O6 is intrinsic, arising from the crystal lattice. We establish a comprehensive phase diagram for this exotic system consistent with recent reports of an incommensurate ground state and identify new sub-features of the ferrimagnetic phase. When defects in the form of grain boundaries are incorporated into the system the low-temperature slow-dynamic state is weakened, and new crossover phenomena emerge in the spin relaxation behavior along with an increased distribution of relaxation times. The presence of both disorder and randomness leads to a spin-glass-like state, as observed in γFe2O3 hollow nanoparticles, where freezing of surface spins at low temperature generates an irreversible magnetization component and an associated exchange-biasing effect. Our results point to distinct dynamic behaviors on the inner and outer surfaces of the hollow structures. Overall, these studies yield new physical insights into the role of dimensionality and disorder in these complex oxide systems and highlight the sensitivity of their manifested magnetic ground states to extrinsic factors, leading in many cases to crossover behaviors where the balance between competing phases is altered, or to the emergence of entirely new magnetic phenomena.

Deoxyribonucleic acid (DNA) is arguably the most studied and most important biological molecule. Recently, it has also been established as a potential candidate for nanoconstruction. Self-assembly of DNA molecules has emerged as a simple yet elegant technique to organize matter with sub-nanometer precision. The unique base-pairing properties which helps DNA to carry genetic information, also makes it a suitable building block for creating stable and robust nanostructures. Recent decades have witnessed a major revolution in the synthesis of different topological structures made of DNA molecules at nanoscale like, two dimensional arrays, nanotubes, polyhedra, smiley faces, three dimensional crystals etc. Due to their easier design, high fidelity and automated chemistry, DNA nanostructures have proposed applications in diverse fields of bio-nanotechnology and synthetic biology. The field of structural DNA nanotechnology is just entering in adulthood and offer paramount challenge towards the journey of DNA-based nanostructures from the laboratory to their practical implementation in the real world. The aim of my dissertation is to develop a de novo computational framework to investigate the nanoscale structure and properties of DNA-based nanostructures. This will help to understand the molecular origin of interaction governing the structure and stability of DNA nanostructures. In this thesis, we have studied the in-solution behavior of self-assembled DNA nanostructures. The state of art all atom molecular dynamics (MD) simulation has been extensively implemented to understand the various thermodynamic properties of these self-assembled soft matter systems. We expect that the results presented here will lead to better design of self-assembled DNA nanostructures to address the real world challenges. In particular, we have developed algorithms to build very accurate atomistic models of various DNA nanostructures like crossover DNA molecules, DNA nanotubes (DNTs) and DNA icosahedron (IDNA). Further, we discuss a computational framework to understand the in situ structure and dynamics of these DNA nanostructures using state-of-art MD simulation. We carried out several hundred nanosecond long MD simulations on these systems which sometimes contains close to one million atoms. Following the trajectories of nanostructures in physiological conditions, we predicted numerous properties like equilibrium solution structure behavior and elastic properties which are difficult to measure in experiments. DNTs are self-assembled tubular templates where the circular double helical domains, kept at the vertices of a polygon, are connected at crossovers junctions. Ned Seeman and co-workers at New York University have synthesized different kind of DNTs using tile-based self-assembly of oligonucleotides. To investigate their microscopic structure, stability and mechanical properties, we have come up with 3d atomistic models of various DNTs which will facilitate further studies of these nanotubes towards their proposed nanotechnological and biological applications. In chapter 3 of this thesis, we discuss the analysis of several nanoseconds long all-atom MD simulation trajectories of various DNTS in the presence of explicit salt solution. We conclude that 6-helix DNT (6HB) structures are most stable and well behaved due to the better crossover designs and geometry. There has been considerable interest to investigate and enhance the mechanical strengths of DNTs to create rigid motifs. One simple way to increase the rigidity is to add further helices to the 6HB, which is known to be the most stable design of DNT, with the same tile-based crossover method. In chapter 4, we report atomistic models of 6HB flanked symmetrically with two double helical DNA pillars (6HB+2) and 6HB flanked symmetrically by three double helical DNA pillars (6HB+3). From the fluctuation analysis of the equilibrium MD simulation trajectories, we calculated the stretch modulus and persistence length of these DNTs. The measured persistence lengths of these nanotubes are ∼10 μm, which is 2 orders of magnitude larger than that of dsDNA. We also find a gradual increase of persistence length with an increasing number of pillars, in quantitative agreement with previous experimental findings. We also carried out non-equilibrium Steered-Molecular-Dynamics (SMD) to measure the stretch modulus from the force-extension behavior of these pillared DNTs. The values of the stretch modulus calculated using contour length distribution of equilibrium MD simulations are similar to those obtained from non-equilibrium SMD simulations. The addition of pillars makes these DNTs very rigid. Engineering the synthetic nanopores through lipid bilayer membrane to access the interior of a cell is a long standing challenge in biotechnology. Recently, a new class of DNA nanopores through the lipid bilayer membranes has been characterized using advanced imaging techniques and transmembrane ionic current recordings. In chapter 5 of the thesis, we present a MD simulation study of 6HB embedded in POPC lipid bilayer membranes. The analyses of 0.2 µs long equilibrium MD simulation trajectories demonstrate that structure is stable and well behaved. We observe that the head groups of the lipid molecules close to DNT cooperatively tilt towards the hydrophilic sugar-phosphate backbone of DNA to form a toroidal structure around the patch of DNT protruding in the membrane. Based on this observation, we propose a new mechanism, which has been largely overlooked so far, to explain the stability to this DNA-lipid molecular self-assembly. We further explore the effect of monovalent ionic concentrations to the in-solution structure and stability of the nanocomposite. Transmembrane ionic current measurements during the constant electric field simulation provide the I-V characteristics of the water filled DNT lumen in lipid membrane. The conductivity of the DNT lumen turns out to be several nS and increases with ionic concentration. Recently, Krishnan’s research group at NCBS Bangalore and Chicago University have characterized DNA icosahedra (IDNA) using advance imaging techniques and validated it for biological targeting and bioimaging in vivo. A high resolution structural model of such polyhedra would be critical to widening their applications in both materials and biology. In chapter 6 of this thesis, we discuss an atomistic model of this well-characterized IDNA to study the in-solution behavior using MD simulation. We provide quantitative estimate of the surface and volume of the equilibrium structure which is essential to estimate its maximal cargo carrying capacity. Importantly, our simulation of gold nanoparticles (AuNP) encapsulated within DNA icosahedra (IAuNP) revealed enhanced stability of the AuNP loaded structure as compared to the empty icosahedra. This is consistent with experimental results that show high yields of cargo-encapsulated DNA icosahedra that have led to its diverse applications for precision targeting. These studies reveal that the stabilizing interactions between the cargo and the DNA scaffold powerfully positions DNA polyhedra as targetable nanocapsules for payload delivery. The insights from our study can be further exploited for precise molecular display for diverse biological applications. Finally, in chapter 7, we give a summary of the main results presented in this dissertation. We also briefly discuss the ongoing research work and the bright future of this emerging field of DNA nanotechnology. We believe that this thesis deepens the microscopic understanding of the recent experimental observation and provides impetus in the real world application of DNA nanostructures in vitro and well as in vivo.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to develop and to evaluate the therapeutic efficacy of liposomes diminazene aceturate and in vitro and by using mice experimentally infected with Trypanosoma evansi. In vitro tests were performed in culture medium at concentrations of 0.25, 0.5, 1, 2 and 3 mg/ml of diminazene aceturate convetional (CDMZ) and liposomal (L-DMZ). A total of 114 rats (Rattus norvegicus) were used of in vivo test. These rats were divided into 6 groups (A, B, C, D, E and F). Group A served as a negative control (uninfected and untreated). Rats in Group B served as a positive control and were infected with T. evansi. Animals in Group C were infected and treated with L-DMZ (single dose, 3.5 mg/kg-1), Group D was composed with infected and treated with C-DMZ animals (single dose, 3.5 mg/kg-1), Group E infected treated with L-DMZ animals for 5 consecutive days (3.5 mg/kg-1/dia) and Group F infected treated with C-DMZ animals for 5 consecutive days (3.5 mg/kg-1/dia). In vitro, a dose-dependent trypanocidal effect of L-DMZ was observed against the parasite. In vivo, the efficacy of L-DMZ and C-DMZ in different therapeutic protocols was similar. The analysis of biochemical and histological parameters on the 7th and 40th post-treatment revealed alterations in liver and kidney enzymes, and histological alterations in the structure of organs, especially in the animals treated with L-DMZ at 5 consecutive days. The results of this study showed that liposomal formulations may be a new alternative for the treatment of tripanosomoses, but future research could be undertaken to improve the conduction of liposomes and direction for greater efficiency. / Este estudo teve como objetivo desenvolver e testar lipossomas de aceturato de diminazeno em testes in vitro e in vivo visando o controle de Trypanosoma evansi. O teste in vitro foi realizado em meio de cultura nas concentrações de 0,25, 0,5, 1, 2 e 3 μg/mL de aceturato de diminazeno convencional (C-DMZ) e lipossomal (L-DMZ). Para os testes in vivo foram utilizados 114 ratos (Rattus norvegicus) divididos em seis grupos (A, B, C, D, E e F) em dois experimentos, um para avaliar a eficácia e outro para analisar os parâmetros bioquímicos e histológicos. O grupo A foi utilizado como controle (animais sadios), B (animais infectados e não tratados), C (animais infectados e tratados com aceturato de diminazeno lipossomal com dose única 3,5 mg/kg-1), D (animais infectados e tratados com aceturato de diminazeno convencional com dose única 3,5 mg/kg-1), E (animais infectados e tratados com aceturato lipossomal por 5 dias consecutivos com a dose de 3,5 mg/kg-1/dia) e grupo F (animais e infectados tratados com aceturato convencional por 5 dias consecutivos com a dose de 3,5 mg/kg-1/dia). O teste in vitro com o lipossoma de aceturato de diminazeno mostrou uma maior mortalidade dose-dependente do T. evansi em meio de cultura se comparado ao medicamento comercial e os parasitos morreram mais rapidamente que nos grupos de aceturato de diminazeno convencional e controle. Nos resultados dos testes in vivo, a eficácia do aceturato de diminazeno lipossomal e convencional nos diferentes protocolos terapêuticos foram similares. A análise dos parâmetros bioquímicos e histológicos realizados no 7º e 40º pós-tratamento revelaram alterações nas enzimas hepáticas e renais, além de modificações na estrutura dos órgãos, principalmente nos animais tratados com lipossomas na maior dosagem. Os resultados obtidos neste estudo demonstraram que as formulações lipossomais podem ser uma nova alternativa para o tratamento das tripanossomoses. Futuras pesquisas poderiam ser realizadas para melhorar o carreamento e a direção dos lipossomas para uma maior eficácia.

This diploma thesis discusses the gas sensor preparation via anodic oxidation. It names sensor types, deals with the sensing principle of electrochemical sensors in detail and submits sensor parameters. It describes preparation technology and characterization technology methods. In the experimental part, it focuses on both the measurement methodology and the electrochemical oxygen sensor covered with titanium dioxide nanocolumns fabrication. Not the least it discusses acquired research results.