Submitted by Naiara Letícia Marana null (namarana@fc.unesp.br) on 2017-06-23T18:05:03Z No. of bitstreams: 1 Marana_Naiara_Letícia_Tese.pdf: 4675285 bytes, checksum: acbe2527f22092d1278a0801ad362524 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-06-28T16:26:20Z (GMT) No. of bitstreams: 1 marana_nl_dr_bauru.pdf: 4675285 bytes, checksum: acbe2527f22092d1278a0801ad362524 (MD5) / Made available in DSpace on 2017-06-28T16:26:20Z (GMT). No. of bitstreams: 1 marana_nl_dr_bauru.pdf: 4675285 bytes, checksum: acbe2527f22092d1278a0801ad362524 (MD5) Previous issue date: 2017-04-25 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A química computacional tem se mostrado uma ferramenta muito útil no meio científico e tem sido cada vez mais utilizada na pesquisa de novos materiais. Dentre os muitos sistemas estudados com o auxílio da química computacional, destaca-se o óxido de zinco (ZnO), muito utilizado em diversos dispositivos eletrônicos tais como, sensores, células solares, diodos de emissão de luz UV e diodos a laser. À temperatura e pressão ambientes, a estrutura cristalina mais estável do ZnO é hexagonal do tipo wurtzita, na qual os átomos de zinco estão coordenados a quatro átomos de oxigênio. Devido a coordenação tetraédrica e falta de centro de simetria dessa estrutura, o ZnO apresenta propriedades piezoelétricas podendo ser aplicado em sensores piezoelétricos, por exemplo. Atualmente, existem muitos trabalhos científicos relacionados com o ZnO, porém o número de trabalhos teóricos em relação aos trabalhos experimentais ainda é pequeno. Neste sentido, este projeto teve como objetivo a análise das propriedades do ZnO em três morfologias diferentes, bulk, superfícies e nanotubos, aplicando as principais técnicas de modelagem computacional aplicada ao estado sólido tais como escolha do funcional de densidade e funções de base, otimização da geometria, dopagem por substituição de átomos, cálculo de constantes elásticas e piezoelétricas, simulação de pressão hidrostática aplicada a célula unitária, secção do bulk para gerar superfícies, substituição de átomos para formar interfaces, nanotubos e adsorção de moléculas nos nanotubos. Os cálculos foram realizados aplicando-se a Teoria do Funcional de Densidade, com o auxilio do programa CRYSTAL14, utilizando o funcional híbrido B3LYP, com o conjunto de funções de base all-electron. A metodologia aplicada conserva a periodicidade dos sistemas cristalinos (1D para nanotubos, 2D para superfícies ou 3D para bulk), em que os blocos de construção são compostos por células unitárias e podem ser replicados pelo operador de simetria. As análises topológicas foram realizadas aplicando-se a Teoria Quântica de átomos em Moléculas de Bader. Após a escolha do nível de teoria, as propriedades estruturais, eletrônicas, vibracionais, topológicas e constantes elásticas e piezoelétricas foram analisadas para o bulk. Partindo da estrutura otimizada, os átomos de zinco foram substituídos por Mn2+ e Al3+, simulando sistemas dopados. Paralelamente, foi realizado o estudo do comportamento das constantes elásticas e piezoelétricas em função da variação de pressão hidrostática, que mostrou a resposta piezoelétrica do ZnO aumenta em função da pressão. Após o estudo do bulk, as superfícies (101 ̅0), (112 ̅0) e (0001) foram analisadas e estudadas através de sua energia superficial, propriedades estruturais, eletrônicas e topológicas. A partir da monocamada da superfície (0001), os nanotubos armchair, zigzag e quiral foram gerados e estudados de acordo com sua obtenção, estabilidade e diferentes propriedades. A adsorção de moléculas de NH3 à parede dos nanotubos armchair e zigzag foi estudada onde foram investigadas as alterações nas propriedades decorrentes da adsorção, mostrando que os nanotubos de ZnO são possíveis de serem aplicados em sensores de gás amônia. Por fim, o estudo de sistemas com interface ZnO/GaN foram estudadas para as superfícies (101 ̅0) e (112 ̅0) e nanotubos armchair e zigzag. Ao final, concluiu-se que os sistemas de interface podem ser aplicados em LEDs, por exemplo, pois o controle de espessura e material pertencente à camada externa da interface leva a diferentes emissões no espectro eletromagnético, indo do UVA ao Verde. Com este estudo, pretendeu-se investigar o máximo das três morfologias do ZnO na fase wurtzita e sugerir algumas possíveis aplicações. / Computational chemistry has proved to be a very useful tool in the scientific field and has been increasingly used in the research of new materials. Among the many systems studied with the aid of computational chemistry, we highlight zinc oxide (ZnO), widely used in many electronic devices such as sensors, solar cells, UV light emitting diodes and laser diodes. At room temperature and pressure, the most stable crystalline structure of ZnO is hexagonal of the wurtzite type, in which the zinc atoms are coordinated to four oxygen atoms. Due to the tetrahedral coordination and lack of center of symmetry of this structure, the ZnO presents piezoelectric properties and can be applied in piezoelectric sensors, for example. Currently, there are many papers related to ZnO, however the number of theoretical articles in relation to the experimental works are still small. In this sense, this project aimed the analysis of ZnO properties in three different morphologies, bulk, surfaces and nanotubes, applying the main techniques of computational modeling to solid state such as the choice of density functional and basic functions, optimization of geometry, doping by atom replacement, calculation of elastic and piezoelectric constants, hydrostatic pressure simulation applied to unit cell, bulk section to generate surfaces, replacement of atoms to form interfaces, nanotubes and adsorption of molecules in nanotubes. The calculations were performed applying the Density Functional Theory, with the help of the CRYSTAL14 program, using the hybrid function B3LYP, with the set of all-electron base functions. The applied methodology preserves the periodicity of the crystalline systems (1D for nanotubes, 2D for surfaces or 3D for bulk), in which the building blocks are composed of unit cells and can be replicated by the symmetry operator. The topological reviews were performed applying the Quantum Theory of atoms in Bader's Molecules. After choosing the level of theory, the structural, electronic, vibrational, topological and elastic and piezoelectric constants were analyzed for bulk. From the optimized structure, the zinc atoms were replaced by Mn2+ and Al3+, simulating doped systems. In parallel, a study of the behavior of the elastic and piezoelectric constants was conducted due to the hydrostatic pressure variation, which showed that the piezoelectric response of ZnO increases according to the pressure. After the bulk study, the surfaces (101 ̅0), (112 ̅0) and (0001) were analyzed and studied through their surface energy, structural, electronic and topological properties. From the surface monolayer (0001), the armchair, zigzag and chiral nanotubes were generated and studied according to their obtainment, stability and different properties. The adsorption of NH3 molecules to the wall of the armchair and zigzag nanotubes was studied and an investigation of the changes in the adsorption properties was carried out, showing that ZnO nanotubes are possible to be applied in ammonia gas sensors. Finally, the study of systems with ZnO/GaN interface was conducted for the surfaces (101 ̅0) and (112 ̅0), and armchair and zigzag nanotubes. At the end, it was concluded that the interface systems can be applied in LEDs, for example, because the control of thickness and material belonging to the outer layer of the interface leads to different emissions in the electromagnetic spectrum, going from UVA to green. This study aimed to investigate the maximum of three ZnO morphologies in the wurtzite phase and to suggest some possible applications. / FAPESP: 2013/19713-7 / FAPESP: 2016/07954-8

abstract: Titanium oxide (TiO2), an abundant material with high photocatalytic activity and chemical stability is an important candidate for photocatalytic applications. The photocatalytic activity of the TiO2 varies with its phase. In the current project, phase and morphology changes in TiO2 nanotubes were studied using ex-situ and in-situ transmission electron microscopy (TEM). X-ray diffraction and scanning electron microscopy studies were also performed to understand the phase and morphology of the nanotubes. As prepared TiO2 nanotubes supported on Ti metal substrate were amorphous, during the heat treatment in the ex-situ furnace nanotubes transform to anatase at 450 oC and transformed to rutile when heated to 800 oC. TiO2 nanotubes that were heat treated in an in-situ environmental TEM, transformed to anatase at 400 oC and remain anatase even up to 800 oC. In both ex-situ an in-situ case, the morphology of the nanotubes drastically changed from a continuous tubular structure to aggregates of individual nanoparticles. The difference between the ex-situ an in-situ treatments and their effect on the phase transformation is discussed. Metal doping is one of the effective ways to improve the photocatalytic performance. Several approaches were performed to get metal loading on to the TiO2 nanotubes. Mono-dispersed platinum nanoparticles were deposited on the TiO2 nanopowder and nanotubes using photoreduction method. Photo reduction for Ag and Pt bimetallic nanoparticles were also performed on the TiO2 powders. / Dissertation/Thesis / M.S. Materials Science and Engineering 2014

Made available in DSpace on 2018-06-27T18:56:06Z (GMT). No. of bitstreams: 3 Alexandra Nava.pdf: 7405065 bytes, checksum: 98440f22cb0a32ce958d08b696afa588 (MD5) Alexandra Nava.pdf.txt: 147318 bytes, checksum: 2efcb934aeddafd9aa0074818849ced7 (MD5) Alexandra Nava.pdf.jpg: 3394 bytes, checksum: 0468f8b34b379928f05335b2f501d0b1 (MD5) Previous issue date: 2010-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Carbon nanotubes (CNT) appear as a new class of materials that have special properties and are the focus of many studies in the biological area. Toxicity studies are important to evaluate the biocompatibility and the possible risks of exposure to the CNT. In this context, we evaluated the reproductive toxicity of exposure to multi-walled carbon nanotubes (MWCNT) in pregnant mice. To this end, pregnant females were exposed orally 100 μl MWCNT/day, suspended in PBS / Tween 80® at a concentration of 5 mg/ml and 15 mg/ml during the implantation period (1st to 6th day of pregnancy), organogenesis (7th to 12th day of pregnancy) or during the fetal period (13th to the 18th day of pregnancy). The females were evaluated for changes in weight and consumption of food and water throughout the experiment. In the 18th day of pregnancy, females were undergoing cesarean section and recorded the number of live fetuses, resorptions and dead. The fetuses were weighed, measured and fixed in 70% alcohol (v/v) for analysis of skeletal changes. Maternal organs, liver, kidney, spleen, heart and lung were collected, weighed and fixed in formaldehyde 10% (v/v) for histological analysis. There were mild signs of maternal toxicity, viewed mainly by histological organs and all embryofetal observed changes occurred in animals exposed during the period of organogenesis. Exposure to MWCNT at a dose of 0.5 mg/day showed an increase in the number of resorptions and reduced number of live fetuses in the control group. The exposure to MWCNT 1.5 mg/day showed an increase in the proportion of resorptions, the average of dead fetuses and a reduction in the proportion of live fetuses, resulting in increased rates of prenatal losses. Changes in body weight of fetuses measures were observed in a dosedependent. Analysis of the skeleton showed a marked delay of ossification, also in a dosedependent. These data support the conclusion that exposure to MWCNT at doses of 0.5 mg/day and 1.5 mg/day, cause an increase in losses and prenatal growth retardation, intrauterine, when administered during organogenesis, and these changes may be related to the direct action of the body MWCNT or fetal abnormalities observed in the morphology of the mother's organs. / Os nanotubos de carbono (NTC) surgem como uma nova classe de materiais que apresentam propriedades especiais e estão sendo foco de muitos estudos na área biológica. Estudos de toxicidade tornam-se importantes para avaliação da biocompatibilidade e dos possíveis riscos da exposição à NTC. Neste contexto, avaliou-se a toxicidade reprodutiva da exposição à nanotubos de carbono de paredes múltiplas (NCPM) em camundongos prenhes. Para tanto, fêmeas grávidas foram expostas oralmente a 100 μL NCPM/dia, suspensos em solução de PBS/Tween 80® na concentração de 5mg/mL e 15 mg/mL, durante o período de implantação (1º ao 6º dia de gestação - ddg), organogênese (7º ao 12º ddg) ou durante o período fetal (13º ao 18º ddg). As fêmeas foram avaliadas quanto a alterações de peso e no consumo de água e ração durante todo o experimento. No 18º ddg, as fêmeas foram submetidas à cesariana sendo registrado o número de fetos vivos, mortos e reabsorções. Os fetos foram pesados, medidos e fixados em álcool 70% (v/v) para análise de alterações esqueléticas. Os órgãos maternos, fígado, rim, baço, coração e pulmão foram coletados, pesados e fixados em formol 10% (v/v) para análise histológica. Observaram-se leves sinais de toxicidade materna, visualizados principalmente por alterações histológicas nos órgãos e todas as alterações embriofetais observadas ocorreram nos animais expostos durante o período da organogênese. A exposição à NCPM, na dose de 0,5 mg/dia mostrou aumento no número de reabsorções e redução no número de fetos vivos em relação ao grupo controle. A exposição a 1,5 mg NCPM/dia mostrou o aumento na proporção de reabsorções, na média de fetos mortos e uma redução na proporção de fetos vivos, culminando no aumento do índice de perdas pré natais. Alterações no peso corporal dos fetos foram observadas de forma dose-dependente. A análise do esqueleto demonstrou um intenso retardo de ossificação, também de forma dose dependente. Esses dados permitem concluir que a exposição à NCPM, nas doses de 0,5 mg/dia e 1,5 mg/dia, causam aumento nas perdas pré-natais e retardo de crescimento intra-uterino, quando administrados durante o período da organogênese e essas alterações podem estar relacionadas com a ação direta dos NCPM no organismo embriofetal ou com as alterações observadas na morfologia dos órgãos maternos.

Submitted by MARCIA ROVADOSCHI (marciar@unifra.br) on 2018-08-14T19:29:34Z No. of bitstreams: 2 Dissertacao_AlexandreNava.pdf: 7409778 bytes, checksum: e53af9a26d93c0c8d78123589cb1a973 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-14T19:29:34Z (GMT). No. of bitstreams: 2 Dissertacao_AlexandreNava.pdf: 7409778 bytes, checksum: e53af9a26d93c0c8d78123589cb1a973 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2010-03-30 / Carbon nanotubes (CNT) appear as a new class of materials that have special properties and are the focus of many studies in the biological area. Toxicity studies are important to evaluate the biocompatibility and the possible risks of exposure to the CNT. In this context, we evaluated the reproductive toxicity of exposure to multi-walled carbon nanotubes (MWCNT) in pregnant mice. To this end, pregnant females were exposed orally 100 μl MWCNT/day, suspended in PBS / Tween 80® at a concentration of 5 mg/ml and 15 mg/ml during the implantation period (1st to 6th day of pregnancy), organogenesis (7th to 12th day of pregnancy) or during the fetal period (13th to the 18th day of pregnancy). The females were evaluated for changes in weight and consumption of food and water throughout the experiment. In the 18th day of pregnancy, females were undergoing cesarean section and recorded the number of live fetuses, resorptions and dead. The fetuses were weighed, measured and fixed in 70% alcohol (v/v) for analysis of skeletal changes. Maternal organs, liver, kidney, spleen, heart and lung were collected, weighed and fixed in formaldehyde 10% (v/v) for histological analysis. There were mild signs of maternal toxicity, viewed mainly by histological organs and all embryofetal observed changes occurred in animals exposed during the period of organogenesis. Exposure to MWCNT at a dose of 0.5 mg/day showed an increase in the number of resorptions and reduced number of live fetuses in the control group. The exposure to MWCNT 1.5 mg/day showed an increase in the proportion of resorptions, the average of dead fetuses and a reduction in the proportion of live fetuses, resulting in increased rates of prenatal losses. Changes in body weight of fetuses measures were observed in a dosedependent. Analysis of the skeleton showed a marked delay of ossification, also in a dosedependent. These data support the conclusion that exposure to MWCNT at doses of 0.5 mg/day and 1.5 mg/day, cause an increase in losses and prenatal growth retardation, intrauterine, when administered during organogenesis, and these changes may be related to the direct action of the body MWCNT or fetal abnormalities observed in the morphology of the mother's organs. / Os nanotubos de carbono (NTC) surgem como uma nova classe de materiais que apresentam propriedades especiais e estão sendo foco de muitos estudos na área biológica. Estudos de toxicidade tornam-se importantes para avaliação da biocompatibilidade e dos possíveis riscos da exposição à NTC. Neste contexto, avaliou-se a toxicidade reprodutiva da exposição à nanotubos de carbono de paredes múltiplas (NCPM) em camundongos prenhes. Para tanto, fêmeas grávidas foram expostas oralmente a 100 μL NCPM/dia, suspensos em solução de PBS/Tween 80® na concentração de 5mg/mL e 15 mg/mL, durante o período de implantação (1º ao 6º dia de gestação - ddg), organogênese (7º ao 12º ddg) ou durante o período fetal (13º ao 18º ddg). As fêmeas foram avaliadas quanto a alterações de peso e no consumo de água e ração durante todo o experimento. No 18º ddg, as fêmeas foram submetidas à cesariana sendo registrado o número de fetos vivos, mortos e reabsorções. Os fetos foram pesados, medidos e fixados em álcool 70% (v/v) para análise de alterações esqueléticas. Os órgãos maternos, fígado, rim, baço, coração e pulmão foram coletados, pesados e fixados em formol 10% (v/v) para análise histológica. Observaram-se leves sinais de toxicidade materna, visualizados principalmente por alterações histológicas nos órgãos e todas as alterações embriofetais observadas ocorreram nos animais expostos durante o período da organogênese. A exposição à NCPM, na dose de 0,5 mg/dia mostrou aumento no número de reabsorções e redução no número de fetos vivos em relação ao grupo controle. A exposição a 1,5 mg NCPM/dia mostrou o aumento na proporção de reabsorções, na média de fetos mortos e uma redução na proporção de fetos vivos, culminando no aumento do índice de perdas pré natais. Alterações no peso corporal dos fetos foram observadas de forma dose-dependente. A análise do esqueleto demonstrou um intenso retardo de ossificação, também de forma dose dependente. Esses dados permitem concluir que a exposição à NCPM, nas doses de 0,5 mg/dia e 1,5 mg/dia, causam aumento nas perdas pré-natais e retardo de crescimento intra-uterino, quando administrados durante o período da organogênese e essas alterações podem estar relacionadas com a ação direta dos NCPM no organismo embriofetal ou com as alterações observadas na morfologia dos órgãos maternos.

Submitted by MARCIA ROVADOSCHI (marciar@unifra.br) on 2018-08-16T13:45:47Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_NaraMariaBeckMartins.pdf: 7512915 bytes, checksum: 196398dd32ccc4f1db2d9fd1d3a831d4 (MD5) / Made available in DSpace on 2018-08-16T13:45:47Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_NaraMariaBeckMartins.pdf: 7512915 bytes, checksum: 196398dd32ccc4f1db2d9fd1d3a831d4 (MD5) Previous issue date: 2011-03-31 / Carbon nanotubes (CNT) belong to a new group of materials which have special properties and have been the focus of many studies in the biomedical area. Researches on toxicity are important to evaluate the possibility of using them in organic beings. In that context, we analyzed the histological changes of multi-walled carbon nanotubes (MWCNT) in mice, after oral exposure. To this end, female mice were orally exposed to 100 μL of MWCNT/day, suspended in a PBS/Tween 80® solution, at a concentration of 5 mg/mL, for 7 days. A group of mice was sacrificed on the 7th day and another on the 30th day. Liver, spleen, heart, lungs, kidneys and brain were collected and fixed in formaldehyde 10% for histological analysis (v/v). MWCNT accumulation in the organs was detected, deeper in mice from the second group. Inflammation in the liver was also observed in mice that were sacrificed on the 30th day. These inflammatory disturbances can be related to the direct action of MWCNT in organism. The data analysis suggests that oral exposure to a 0,5 mg/day dose of MWCNT causes accumulation of the material in organs and time-dependent hepatic inflammatory signals. / Nanotubos de carbono (NC) pertencem a uma nova classe de materiais que apresentam características especiais e estão sendo foco de muitas pesquisas para uso na área biomédica. Estudos de toxicidade são importantes para avaliar a possibilidade do uso em organismos vivos. Neste contexto, foram analisadas as alterações histológicas provocadas pela administração oral de nanotubos de carbono de paredes múltiplas (NCPM) em camundongos. Para tanto, camundongos fêmeas foram expostos oralmente a 100μL NCPM/dia suspensos em solução de PBS/Tween 80® na concentração de 5 mg/mL, durante 7 dias. Um grupo foi sacrificado no 7º dia e outro grupo no 30º dia. Fígado, baço, coração, pulmões, rins e cérebro foram coletados e fixados em formol 10% (v/v) para análise histológica. Observou-se deposição de NCPM nos órgãos, mais acentuadas no grupo sacrificado no 30º dia e sinais de inflamação no fígado neste grupo. Estas alterações inflamatórias podem estar relacionadas com a ação direta dos NCPM no organismo. Estes dados permitem concluir que a exposição por via oral a NCPM na dose de 0,5mg/dia causam deposição do material nos órgãos e sinais inflamatórios hepáticos dependentes do tempo.

Orientador: Vitor Baranauskas, Walkyria Mara Gonçalves Volpini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-23T06:56:53Z (GMT). No. of bitstreams: 1 Camilo_DanielaFranchiPereiradaSilva_M.pdf: 7402339 bytes, checksum: 4a71443f20b4e716e5328394cdea307b (MD5) Previous issue date: 2013 / Resumo: Os nanotubos de carbono (NTC) têm sido utilizados em larga escala com finalidades industriais e avaliados, por sua estrutura e propriedades, como ferramenta para aplicação biomédica. Tanto a manipulação humana direta na produção industrial como a perspectiva do uso em medicina suscitaram amplas pesquisas para avaliar seu risco na saúde humana e o impacto ambiental. O presente trabalho teve como objetivo determinar os efeitos em longo prazo da administração sistêmica de nanotubos de parede múltipla (MWNTC) não funcionalizados na evolução do diabetes autoimune espontâneo do camundongo "Non Obese Diabetic" (NOD). O protocolo consistiu do tratamento de fêmeas NOD/Uni, de 6 semanas de vida, com uma única injeção intraperitoneal de MWNTC (100 ?g/animal) ou do veículo Pluronic (grupo controle) e do estudo longitudinal de parâmetros clínicos, histológicos e de resposta imunológica, até 24 semanas após administração. Os dados histológicos demonstraram que o MWNTC não funcionalizado foi absorvido da cavidade peritoneal e permaneceu retido em células fagocitárias de linfonodos peri-pancreáticos, baço e fígado, onde causou uma resposta inflamatória granulomatosa, e também em parede de ductos pancreáticos, tendo confirmada sua identificação estrutural in situ, dentro de fagolisossomos de macrófago e no epitélio ductal, por microscopia eletrônica de transmissão (HRTEM). Apesar de não ter havido diferenças na frequência de desenvolvimento do diabetes clínico ou das características morfológicas da insulite pancreática, as fêmeas NOD tratadas com MWNTC apresentaram flutuação média de glicemias significativamente maior em relação ao grupo controle, até o final do estudo (p<0,0001; Wilcoxon), com tendência a antecipação do aparecimento do diabetes clínico. Neste estudo, foi analisado um perfil de citocinas pró e anti-inflamatórias previamente avaliadas no laboratório, em fase aguda após a exposição à MWNTC. Foi focada a expressão evolutiva destas citocinas em linfonodos peri-pancreáticos, sítio de ativação de células T auto-reativas contra antígenos da célula ? pancreática. O MWNTC induziu uma resposta Th1 mais acentuada nos animais tratados, entre a 14ª e a 20ª semana de vida (momento de insulite extensa), com aumento da expressão de INF? e aumento da relação INF?/TGF? e INF?/IL10. Esta relação permanece elevada na 30ª semana de vida das fêmeas NOD tratadas, com reduzida expressão de TGF?. Nossos dados compreendem um dos mais longos seguimentos in vivo após administração sistêmica de MWNTC, demonstrando que o MWNTC não funcionalizado pode ser transportado e retido no sistema reticulo-endotelial e persistir no corpo por longo tempo, como detectado, neste estudo, em células fagocitárias de linfonodos regionais peri-pancreáticos de animais tratados, mesmo 6 meses após sua administração. Os nanotubos comerciais utilizados em diversos campos da tecnologia moderna são partículas não modificadas. Mesmo compreendendo a necessidade de se modificar a nanoestrutura para vislumbrar sua aplicação em medicina, relevância deve ser dada para o risco da exposição humana e ambiental ocorrendo neste momento. Uma resposta inflamatória crônica, com aumento da relação entre citocinas pró/antiinflamatórias, pode ser associada à maior gravidade de doenças autoimunes em organismos suscetíveis / Abstract: Carbon nanotubes (CNT) have been used in large scale for industrial purposes and evaluated for its structure and properties as a tool for biomedical application. Both the direct human manipulation in industrial production as the prospect of use in medicine attracted extensive research to assess their risk to human health and environmental impact. This study aims to determine the long-term effects of systemic administration of multi-wall carbon nanotubes (MWCNT) not functionalized in the evolution of spontaneous autoimmune diabetes in "Non Obese Diabetic" mice (NOD). The protocol consisted of the treatment of 6 weeks female NOD/Uni, with a single intraperitoneal injection of MWCNT (100 ?g/animal) or vehicle Pluronic (control group) with longitudinal study of clinical and histological parameters and immunological response until 24 weeks after administration. The histologic data demonstrated that non-functionalized MWCNT was absorbed from the peritoneal cavity and was retained on phagocytic cells of peripancreatic lymph nodes, spleen and liver, where it caused a granulomatous inflammatory response, and also in the wall of the pancreatic ducts, and their structural identification in situ was confirmed within macrophage phagolysosomes and ductal epithelium by transmission electron microscopy (HRTEM). Although there were no differences in the frequency of development of overt diabetes or morphological characteristics of pancreatic insulitis, MWCNT treated NOD females had average blood glucose fluctuation significantly higher than control group until the end of the study (p<0,0001; Wilcoxon), with a tendency to anticipate the onset of clinical diabetes. In this study we analyzed a profile of previously evaluated pro-inflammatory and antiinflammatory in the acute phase after exposure to MWCNT. We focused on the evolutive expression of these cytokines in peri-pancreatic lymph nodes, site of activation of T cells reactive against pancreatic ? cell antigens. MWCNT induced a stronger Th1 response in treated animals, between the 14th and 20th weeks of life (time of extensive insulitis), with increased expression of IFN? and increased ratio of INF?/TGF? and INF?/IL10. This ratio remains high at treated NOD females aged 30 weeks, with reduced expression of TGF?. Our data comprise one of the longest in vivo follow-up after systemic administration of MWCNT, demonstrating that nonfunctionalized MWCNT can be transported and retained in the reticulo-endothelial system and persist in the body for long time, as detected in this study, in phagocytic cells of peri-pancreatic regional lymph nodes, even six months after its administration. The nanotubes used in various commercial fields of modern technology are unmodified. Even comprising the need to modify the nanostructure to effective its application in medicine, importance should be given to the risk of human and environmental exposure occurring at this time. A chronic inflammatory response, with an increased ratio of pro/anti-inflammatory cytokines may be associated with greater severity of autoimmune diseases in susceptible organisms / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestra em Engenharia Elétrica

Three systems of electrospun composite membranes with piezoelectric polymer polyvinylidene fluoride (PVDF) as matrix incorporating: 1) Carbon based fillers: carbon nanotube (CNT) and graphene oxide (GO); 2) Ceramic based fillers-barium titanate (BT), zinc oxide (ZnO) and nanoclays (halloysite and bentonite); 3) Cellulosic fillers: microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC) at different loadings were prepared by electrospinning process. Influence of filler type and loading on total PVDF crystallinity (Xc), relative fraction of β phase (piezoelectric phase) in total crystalline PVDF (Fβ), volume fraction of β phase in the samples (vβ) and piezoelectric coefficient d33 were characterised and analysed. Correlation between vβ and piezoelectric performance (d33) will be focused by this work. A common situation was observed for the composites-d33 increased while vβ is reduced by the fillers, so it can be concluded that d33 of the composites is not totally up to their vβ, there are other factors that need to be taken into account. For example, for carbon based filler like CNT, it increased electric conductivity of sample during and after electrospinning process, making it easier for charges produced by β crystals from inside of sample to be transferred to surfaces of the sample, and possibly promoting orientation of β crystals in d33 direction, therefore enhanced d33 of the composites though β phase formation was significantly hindered by inclusion of CNT; For piezoelectric ceramic fillers like BT and ZnO, a possible combined piezoelectricity from filler and β phase PVDF might enhanced d33 though less β phase was formed; And for non-piezoelectric and non-conductive fillers, enhancement in orientation of β crystals might play a major role in promotion of d33. Keywords: electrospinning; polyvinylidene fluoride (PVDF); nanocomposites; piezoelectric coefficient d33; energy harvesting.

The discovery of carbon nanotubes (CNTs) in 1991 by Iijima revealed the possibility of ultra-strong materials exploiting the properties of materials at smaller length scales. The superior strength, stiffness, and ability to perform under extreme conditions motivated researchers to investigate further on CNTs and similar materials at nanoscale. This resulted in discovery of various nanostructures such boron nitride nanotubes (BNNTs), graphene, hexagonal boron nitride sheets etc. Many of such nanostructures exhibited superior strength and stiffness comparable to that of CNTs. Out of these nanotubes, BNNTs have recently attracted attention from researchers due to their excellent mechanical properties similar to that of CNTs along with better chemical and thermal stability. Thus, BNNTs can be used for varieties of applications such as protective shield for nanomaterials, optoelectronics, bio-medical, nano spintronics, field-emission tips in scanning tunneling and atomic force microscope, and as reinforcement in composites. BNNTs are also used in other applications such as water cleansing, hydrogen storage, and gas accumulators. To exploit these ultra-strong materials, the mechanics of materials under different conditions of loading and failure need to be studied and understood. Also, to make use of the material in a nanocomposite or other applications, the material properties should be evaluated. The present work is focused on the computational study of the mechanics of nanotubes with special reference to BNNTs and CNTs. Note that the attention is not given to the material but to the nanostructure and mechanics. Hence depending on the state-of-the-art, BNNTs and CNTs are used wherever it is appropriate along with justifications. The chapter-wise outline of the present work is given below. The first chapter is an introduction along with a state-of-the-art literature review. The second chapter introduces the molecular simulation methodology in brief. The chapters from the third to the seventh present the work in detail and describe the major contributions. The final chapter summarizes the work along with a few possible directions to extend the present work. Chapter 1 In this chapter, the importance of computational techniques to study the mechanics at the nanoscale is outlined. A brief introduction to various nanostructures and nanotubes are also given. A detailed literature review on the mechanics of nanotubes with special attention to elastic properties, buckling, tensile failure, and as reinforcement in nanocomposites is presented. Chapter 2 In this chapter, the molecular simulation technique is outlined. The molecular dynamics (MD) simulation is one of the most common simulation techniques used to study materials at the nanoscale. A few interatomic potentials that are used in an MD simulation are explained. Theories linking continuum mechanics with the molecular dynamics are also explained here. Chapter 3 In this chapter, the elastic behavior of single-walled BNNTs under axial and torsional loading is studied. Molecular dynamics (MD) simulation is carried out with a tersoff potential for modeling the interatomic interactions. Different chiral configurations with similar diameter are considered to study the effect of chirality on the elastic and shear moduli. Furthermore, the effects of tube length on elastic modulus are also studied by considering different aspects ratios. It is observed that both elastic and shear moduli depend on the chirality of a nanotube. For aspect ratios less than 15, the elastic modulus reduces monotonically with an increase in the chiral angle. For chiral nanotubes the torsional response shows a dependence on the direction of loading. The difference between the shear moduli against and along the chiral twist directions is maximum for a chiral angle of 15◦, and zero for zigzag (0◦) and armchair (30◦) configurations. Chapter 4 Buckling of nanotubes have been studied using many methods such as MD, molecular mechanics, and continuum based shell theories. In MD, motion of the individual atoms are tracked under an applied temperature and pressure, ensuring a reliable estimate of the material response. The response thus simulated varies for individual nanotubes and is only as accurate as the force field used to model the atomic interactions. On the other hand, there exists a rich literature on the understanding of continuum mechanics based shell theories. Based on the observations on the behavior of nanotubes, there have been a number of shell-theory-based approaches to study the buckling of nanotubes. Although some of these methods yield a reasonable estimate of the buckling stress, investigation and comparison of buckled mode shapes obtained from continuum analysis and MD are sparse. Previous studies show that a direct application of shell theories to study nanotube buckling often leads to erroneous results. In this chapter, the nonlocal effect on the mechanics of nanostructures is studied using Eringen’s nonlocal elasticity. The buckling of carbon nanotubes is considered as an example to demonstrate and understand the nonlocal effect in the nanotubes. Single-walled armchair nanotubes with the radius varying from 3.4nm to 17.7nm are considered and their critical buckling stresses are predicted based on multiscale modeling techniques including classical and nonlocal continuum mechanics theories and MD simulation. Fitting nonlocal mechanics models to MD simulation yields a radius-dependent length-scale parameter, which increases approximately linearly with the radius of carbon nanotube. In addition, the nonlocal shell model is found to be a better continuum model than the nonlocal beam model due to its ability to include the circumferential nonlocal effect. Chapter 5 In this chapter, the effects of geometrical imperfections on the buckling of nanotubes are studied. The present study reveals that a major source of the error in continuum shell theories in calculating the buckling stress can be attributed to the geometrical imperfections. Here, geometrical imperfections refer to the departure of the shape of the nanotube from a perfect cylindrical shell. Analogous to the shell buckling in the macro-scale, in this work the nanotube is modeled as a thin-shell with initial imperfection. Then a nonlinear buckling analysis is carried out using the Riks method. It is observed that this proposed approach yields significantly improved estimate of the buckling stress and mode shapes. It is also shown that the present method can account for the variation of buckling stress as a function of the temperature considered. Hence, this turn out to be a robust method for a continuum analysis of nanotubes taking in the effect of variation of temperature as well. Chapter 6 In this chapter, the effects of Stone-Wales (SW) and vacancy defects on the failure behavior of BNNTs under tension are investigated using MD simulations. The Tersoff-Brenner potential is used to model the atomic interaction and the temperature is maintained close to 300 K. The effect of a SW defect is studied by determining the failure strength and failure mechanism of nanotubes with different radii. In the case of a vacancy defect, the effect of an N-vacancy and a B-vacancy is studied separately. Nanotubes with different chirality but similar diameter are considered first to evaluate the chirality dependence. The variation of failure strength with the radius is then studied by considering nanotubes of different diameter but same chirality. It is observed that the armchair BNNTs are extremely sensitive to defects, whereas the zigzag configurations are the least sensitive. In the case of pristine BNNTs, both armchair and zigzag nanotubes undergo brittle failure, whereas in the case of defective BNNTs only the zigzag ones undergo brittle failure. An interesting defect-induced plastic behavior is observed in defective armchair BNNTs. For this nanotube, the presence of a defect triggers mechanical relaxation by bond breaking along the closest zigzag helical path, with the defect as the nucleus. This mechanism results in a plastic failure. Chapter 7 In this chapter, the utility of BNNTs as reinforcement for nanocomposites with metal matrix is studied using MD simulation. Due to the light weight, aluminium is used as the matrix. The influence of number of walls on the strength and stiffness of the nanocomposite is studied using single-and double-walled BNNTs. The three body tersoff potential is used to model the atomic interactions in BNNTs, while the embedded atom method (EAM) potential is used to model the aluminium matrix. The van der Waals interaction between different groups — the aluminium matrix with the nanotube or the between the concentric tubes in double walled BNNT — is modeled using a Lennard Jones potential. A representative volume element approach is used to model the nanocomposite. The constitutive relations for the nanocomposite is also proposed wherein the elastic constants are obtained using the MD simulation. The nanocomposite with reinforcement shows improved axial stiffness and strength. The double-walled BNNT provides more strength to the nanocomposite than the single-walled BNNT. The BNNT reinforcement can be used to design nanocomposites with varying strength depending on the direction of the applied stress. Chapter 8 The summary of the work with a broad outlook is presented in this chapter. The major conclusions of the work are reiterated and possible directions for taking the work further ahead are mentioned.

The fields of nanomaterial and nanostructures are some of the fastest growing fields in material science today. Carbon nanotubes are at the forefront of these fields and their unique mechanical and electrical properties are of great interest to those working in multiple engineering fields. The overall objective of this study was to design and develop a new process and the equipment necessary, to synthesize carbon nanotubes using high voltage and a high-frequency induction field. This was the first time that a high voltage and an induction field have been used simultaneously in high yield production of carbon nanotubes. The source of carbon came from acetylene with cobalt used as the doping agent. The carbon was molded into carbon nanotubes by the high-voltage field. The carbon nanotubes were characterized using electron microscope techniques. Raman spectroscopy was also used to reveal the defects and graphitic structures of the carbon nanotubes.

La photonique silicium est reconnue comme la technologie à même de répondre aux nouveaux défis des interconnexions optiques. Néanmoins, la photonique silicium doit faire face à d'importants défis. En effet, le Si ne peux pas émettre ou détecter de la lumière dans la plage de longueurs d'onde des télécom (1,3 µm à 1,5 µm). Par conséquent, les sources et les détecteurs sont mis en œuvre avec du Ge et des matériaux III-V. Cette approche multi-matériaux complique la fabrication des dispositifs et augmente le coût final du circuit. Cependant, les nanomatériaux ont été identifiés comme alternative pour la mise en œuvre d’émetteurs-récepteurs moins chers et plus petits.Cette thèse est dédiée à l'étude et au développement de dispositifs optiques et optoélectroniques sur la plateforme photonique silicium basés sur l’utilisation de nanotubes de carbone mono paroi (SWCNT). L’objectif principal est de démontrer les blocs fonctionnels de base qui ouvriront la voie à une nouvelle technologie photonique dans laquelle les propietés actives proviennent des nanotubes de carbone.Les nanotubes de carbone ont été étudiés comme matériaux pour la nanoélectronique avec la démonstration de transistors ultra-compacts à hautes performances. De plus, les SWCNTs semi-conducteurs (s-SWCNTs) sont également des matériaux très intéressants pour la photonique. Les s-SWCNTs présentent une bande interdite directe qui peut être ajustée dans la gamme de longueurs d'onde du proche infrarouge en choisissant le bon diamètre. Les s-SWCNT présentent une photoluminescence et une électroluminescence, pouvant être exploitées pour la mise en œuvre de sources de lumière. Ils présentent également diverses bandes d’absorption pour la réalisation de photodétecteurs. Ces propriétés font que les nanotubes de carbone sont des candidats très prometteurs pour le développement de dispositifs optoélectroniques pour la photonique.Le premier objectif de la thèse était l'optimisation des solutions de nanotubes de carbone. Une technique de tri par ultra-centrifugation assistée par polymère a été optimisée, donnant des solutions de haute pureté en s-SWCNT. Sur cette base, plusieurs solutions de s-SWCNTs ont été élaborées pour obtenir des SWCNTs émettant dans les longueurs d'onde comprise entre 1µm et 1,6µm.Le deuxième objectif était d’étudier l'interaction des s-SWCNT avec des guides d'onde silicium et des résonateurs optiques. Plusieurs géométries ont été étudiées dans le but de maximiser l'interaction des s-SWCNT avec le mode optique en exploitant la composante transverse du champ électrique. D'autre part, une approche alternative a été proposée et démontrée en utilisant la composante longitudinale du champ électrique. En utilisant la composante longitudinale, une amélioration de la photoluminescence, un seuil d’émission avec la puissance de pompe ainsi qu’un rétrécissement de la largeur spectrale des résonances dans les microdisques ont été observés. Ces résultats sont un premier pas très prometteur vers la démonstration d’un laser intégré à base de SWNTs.Le troisième objectif était d'étudier les dispositifs optoélectroniques à base de s-SWCNTs. Plus spécifiquement, une diode électroluminescente (DEL) et un photodétecteur ont été développés, permettant la démonstration du premier lien optoélectronique sur puce basé sur les s-SWCNT.Le dernier objectif de la thèse était d'explorer le potentiel de s-SWCNT pour l’optique non linéaire. Il a été démontré expérimentalement, qu’en choisissant la chiralité des s-SWCNTs, le signe du coefficient Kerr pouvait être soit positif ou négatif. Cette capacité unique ouvre un nouveau degré de liberté pour contrôler les effets non linéaires sur puce, permettant de compenser ou d'améliorer les effets non linéaires pour des applications variées. / Silicon photonics is widely recognized as an enabling technology for next generation optical interconnects. Nevertheless, silicon photonics has to address some important challenges. Si cannot provide efficient light emission or detection in telecommunication wavelength range (1.3μm-1.5μm). Thus sources and detectors are implemented with Ge and III-V compounds. This multi-material approach complicates device fabrication, offsetting the low-cost of Si photonics. Nanomaterials are a promising alternative route for the implementation of faster, cheaper, and smaller transceivers for datacom applications.This thesis is dedicated to the development of active silicon photonics devices based on single wall carbon nanotubes (SWCNTs). The main goal is to implement the basic building blocks that will pave the route towards a new Si photonics technology where all active devices are implemented with the same technological process based on a low-cost carbon-based material, i.e. SWCNT.Indeed, carbon nanotubes are an interesting solution for nanoelectronics, where they provide high-performance transistors. Semiconducting SWCNT exhibit a direct bandgap that can be tuned all along the near infrared wavelength range just by choosing the right tube diameter. s-SWCNTs provide room-temperature photo- and electro- luminescence and have been demonstrated to yield intrinsic gain, making them an appealing material for the implementation of sources. SWCNTs also present various absorption bands, allowing the realization of photodetectors.The first objective of this thesis was the optimization of the purity of s-SWCNT solutions. A polymer-sorting technique has been developed and optimized, yielding high-purity s-SWCNT solutions. Based on this technique, several solutions have been obtained yielding emission between 1µm and 1.6µm wavelengths.The second objective was the demonstration of efficient interaction of s-SWCNT with silicon photonics structures. Different geometries have been theoretically and experimentally studied, aiming at maximizing the interaction of s-SWCNT with optical modes, exploiting the electric field component transversal to light propagation. An alternative approach to maximize the interaction of s-SWCNT and the longitudinal electric field component of waveguide modes was proposed. Both, a power emission threshold and a linewidth narrowing were observed in several micro disk resonators. These results are a very promising first step to go towards the demonstration of an integrated laser based on CNTs.The third objective was to study optoelectronic SWCNT devices. More specifically, on-chip light emitting diode (LED) and photodetector have been developed, allowing the demonstration of the first optoelectronic link based on s-SWCNT. s-SWCNT-based LED and photodetector were integrated onto a silicon nitride waveguide connecting them and forming an optical link. First photodetectors exhibited a responsivity of 0.1 mA/W, while the complete link yielded photocurrents of 1 nA/V.The last objective of the thesis was to explore the nonlinear properties of s-SWCNT integrated on silicon nitride waveguides. Here, it has been experimentally shown, for the first time, that by choosing the proper s-SWCNT chirality, the sign of the nonlinear Kerr coefficient of hybrid waveguide can be positive or negative. This unique tuning capability opens a new degree of freedom to control nonlinear effects on chip, enabling to compensate or enhancing nonlinear effects for different applications.