Made available in DSpace on 2015-04-22T22:02:01Z (GMT). No. of bitstreams: 1 Dissertacao Julio Rodolfo Pessoa Iank.pdf: 2962867 bytes, checksum: cae054b70271d4b5155110e9b2d9641e (MD5) Previous issue date: 2009-06-15 / Fundação de Amparo à Pesquisa do Estado do Amazonas / Currently the study of fullerene or buckyballs C60, C70, C82, etc. has generated great interest for theoretical research and experimental in discover its chemical and physical properties, including the ability of encapsulation of different chemicals species. These searches resulted in the development and possible production by synthesis of new buckyballs, but also with homologous series of C70 molecules with encapsulated metal ions that can be used as superconducting, photoluminescent materials, ferromagnetic materials and also in developing new systems of accumulation and storage of hydrogen gas. This study aims to examine the relative stability of C60 and its derivatives, through a theoretical and computational approach in DFT level with B3LYP hybrid functional using bases 3-21G and 6-31 G++. The results showed that buckyballs and their derivatives are stable against the fragmentation structural, changes were observed only from the C20, C18 and C16, and the latter buckyball does not support encapsulated hydrogen. The characterization of systems C60@(2, 5, 8, 11 and 15)H2 shows a large transfer of charge between hydrogens and carbons in all systems studied which suggests a high probability of acceptance of electrons and limited capacity of the containment least 15 molecules of H2 of encapsulated C60, at the same time demonstrates the great capacity of encapsulation of H2. Other relevant results showed high reactivity to only two molecular systems C60@11H2 and C60@15H2, demonstrating that the C60 is more reactive with high index of H2 encapsulated. / Atualmente o estudo de fulerenos ou buckyballs C60, C70, C82, etc tem geradoum grande interesse para pesquisa teórica e experimental em desvendar suas propriedades químicas e físicas, entre elas a capacidade de encapsulamento de diferentes substâncias químicas. Estas pesquisas resultaram no desenvolvimento e possível produção por síntese de novas buckyballs, como também séries homólogas com moléculas de C70, que podem ser usados como supercondutores, materiais fotoluminescentes, materiais ferromagnéticos e também no desenvolvimento de novos sistemas de acumulação e armazenamento de gás hidrogênio. Este trabalho tem por objetivo analisar as estabilidades relativas do C60 e seus derivados, através de uma abordagem teórico-computacional, em nível DFT com funcional híbrido B3LYP utilizando bases 3-21G e 6-31 G++. Os resultados mostraram que as buckyballs e seus derivados são estáveis frente à fragmentação estrutural, tendo sido observadas mudanças somente a partir do C20, C18 e C16, sendo que a última buckyball não suporta hidrogênio encapsulado. A caracterização de sistemas C60@(2, 5, 8, 11 e 15)H2 demonstra uma grande transferência de carga entre hidrogênios e carbonos em todos os sistemas estudados o que sugere uma altaprobabilidade de aceitação de elétrons e limitada capacidade de confinamento de pelo menos 15 moléculas de H2 encapsuladas do C60, ao mesmo tempo em que demonstra a grande capacidade de encapsulamento de H2. Outros resultados relevantes mostraram alta reatividade molecular somente para dois sistemas C60@11H2 e C60@15H2, demonstrando que o C60 é mais reativo com alto índice de H2 encapsulado.

Ce travail de thèse de doctorat propose et évalue différentes solutions pour caractériser, avec des outils optiques et électromagnétiques non intrusifs, les nanoparticules et agrégats observés dans différents systèmes physiques : suspensions colloïdales, aérosols et plasma poussiéreux. Deux types de modèles sont utilisés pour décrire la morphologie d'agrégats fractals (p. ex. : suies issues de la combustion) et agrégats compacts (qualifiés de « Buckyballs » et observés dans des aérosols produits par séchage de nano suspensions). Nous utilisons différentes théories et modèles électromagnétiques (T-Matrice et approximations du type dipôles discrets) pour calculer les diagrammes de diffusion (ou facteur de structure optique) de ces agrégats, de même que leurs spectres d'extinction sur une large gamme spectrale. Ceci, dans le but d'inverser différentes données expérimentales. Différents outils numériques originaux ont également été mis au point pour parvenir à une analyse morphologique quantitative de clichés obtenus par microscopie électronique. La validation expérimentale des outils théoriques et numériques développés au cours de ce travail est focalisée sur la spectrométrie d'extinction appliquée à des nano agrégats de silice, tungstène et silicium. / This Ph.D. work provides and evaluates various solutions to characterize, with optical/electromagnetic methods nanoparticles and aggregates of nanoparticles found in suspensions, aerosols and dusty plasmas. Two main models are introduced to describe the morphology of particle aggregates with fractal-like (for particles in plasmas and combustion systems) and Buckyballs-like (aerosols, suspensions) shapes. In addition, the author proposes various solutions and methods (T-Matrix, Rayleigh type approximations) to calculate the scattering diagrams (optical structure factors) of fractal aggregates as well as algorithms to inverse extinction spectra. As a reference case for the performed analysis, several tools to describe the morphology of fractal aggregates from electron microscopy images have been also developed. The experimental validation carried out with the Light Extinction Spectrometry (LES) technique (for nano silica beads, tungsten, dusty plasma and silicon aggregates) clearly proves the validity of the algorithms developed as well as the potential of the LES technique.