Navegando por Palavras-chave "Nanocomposite"
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- ItemAcesso aberto (Open Access)Estudo da interação entre nanopolímero conjugado e nanomaterial(Universidade Federal de São Paulo, 2023-10-20) Batista, Giovanna Silva [UNIFESP]; Philadelphi, Laura Oliveira Péres [UNIFESP]; Parolin, Giovana Artuzo; http://lattes.cnpq.br/5165382247780718; http://lattes.cnpq.br/7511492642565571; https://wwws.cnpq.br/cvlattesweb/PKG_MENU.menu?f_cod=0E27B800FE891EE12CC85CD1900E69D9#Os polímeros conjugados demonstram uma série de características que os tornam amplamente utilizados no ramo da eletrônica orgânica, principalmente relacionado as propriedades ópticas e semicondutoras para a produção de dispositivos como LEDs e células solares, como exemplo. O presente trabalho teve como objetivo a preparação e caracterização de um polímero conjugado em escala nano, e estudar o comportamento desse material quando unido à nanopartículas de prata em um compósito de nanomateriais, visando suas possíveis aplicações. O polímero poli-(9,9-dioctilfluoreno)-co-fenileno foi sintetizado via rota de Suzuki, e caracterizado por UV-vis, fluorescência e termogravimetria. O material foi obtido na escala nano através do procedimento de nanoprecipitação e as nanopartículas de prata por redução de nitrato de prata. Suas propriedades foram investigadas, principalmente quanto à estabilidade das nanopartículas e eletronicamente, usando-se técnicas de UV-vis e fluorescência, DLS e Potencial Zeta. Ambos os materiais foram estudados em dispersões aquosas e em filmes preparados através da técnica de casting com quitosana como matriz. De acordo com as análises de UV-vis e fluorescência, as soluções e filmes com os materiais apresentaram perfis semelhantes de absorção e emissão, apesar de demonstrarem maior estabilidade em estado sólido. Apesar das análises de Potencial Zeta que apresentaram altos valores de desvio ao longo do tempo, as nanopartículas apresentam boa estabilidade em solução, sendo confirmada pelo UV-vis. A diferença mais significativa ocorre entre o comportamento de emissão do polímero macro e nanopolímero, devido a diferença nas bandas no espectro. Além disso, o polímero macro também possui resistência a degradação térmica pelo menos 16% maior em relação a todos os filmes estudados. Foi realizado um trabalho de fotodegradação, no qual ambos os materiais demonstraram estabilidade quando submetidos a uma lâmpada de luz UV de 254 e 365 nm por um período de 3 e 6h.
- ItemSomente MetadadadosMethods to grow porous diamond film doped with boron and nitrogen by deposition on carbon nanotubes(Elsevier Science Sa, 2016) Pinheiro, Romario Araujo; Lima, Cintia Macedo de [UNIFESP]; Cardoso, Lays Dias Ribeiro; Trava-Airoldi, Vladimir Jesus; Corat, Evaldo JoseThe nanocomposite of diamond deposited on carbon nanotubes (CNTs) emerged as an alternative to get Boron Doped Diamond (BDD-CNTs) and Nitrogen-Doped Diamond (NDD-CNTs) porous films. This work got excellent wet individual seeding of each carbon nanotube of a CNT forest with minimum changes to its original morphology. The use of an oxygen plasma to graft polar groups on the CNT surface enabled efficient electrostatic self-assembling (ESA) of nanodiamonds from a dispersion in a KCI diluted solution. The use of other routes with polymer functionalization and/or polymer based nanodiamond dispersion always left some residues and promoted nanodiamond bridging among carbon nanotubes. Even though any of the alternatives may produce porous diamond-CNT composites, the one grown to reproduce closely CNT morphology may allow much better results, as a larger surface area. Thermal Chemical Vapor Deposition (CVD) via floating catalyst produced the CNTs. Two different procedures promoted functionalization, either by immersion in the cationic polymer PDDA (Poly Diallyldimethylammonium Chloride) or 02 plasma functionalization. Seeding went on from 4 nm diamond particles dispersed either in DI water with the anionic polymer Poly Sodium Styrenesulfonate (PSS), or with a KCI solution in DI water. A Hot Filament Chemical Vapor reactor deposited diamond film on the CNTs. The composites were characterized through Raman Spectroscopy, Scanning Electron Microscopy with a Field Emission Gun (FEG-SEM) and Energy Dispersive X-ray Spectroscopy (EDS). (C) 2016 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosProdução De Scaffolds De Poli(3-Hidroxibutirato-Co-3-Hidroxivalerato) Reforçados Com Nanocristais De Celulose Para Engenharia De Tecido(Universidade Federal de São Paulo (UNIFESP), 2017-12-15) Montanheiro, Thais Larissa Do Amaral [UNIFESP]; Lemes, Ana Paula [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)This work had as objective the production and characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and cellulose nanocrystals (CNC) scaffolds, by thermally induced phase separation (TIPS), for application in the area of tissue engineering. The effect of two modifications on CNC’s surface on the final properties of the scaffolds was evaluated, one of them being acetylation of CNC (CNC-Ac) and the other, the adsorption of polyethylene glycol (CNC-PEG). Both modifications were characterized and confirmed by transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta potential and thermogravimetry (TGA). TEM images showed the presence of agglomerates for CNC-Ac and CNC-PEG, confirming the reduction of hydrophilicity. On FTIR were observed new bands confirming the acetylation reaction, but the adsorption of PEG could not be confirmed by FTIR. The crystallinity index, obtained by XRD, was reduced about 12% after acetylation, and 18% after pegylation. Zeta potential of both samples was also changed, in both cases to more positive values. The thermal stability was reduced after both functionalizations, being more affected after the adsorption of PEG. The scaffolds were produced with 6% w/v PHBV/dioxane and using quenching temperature of -43 ± 2 °C. PHBV, PHBV/CNC, PHBV/CNC-Ac and PHBV/CNC-PEG scaffolds were then produced with concentrations of 1, 2 and 3 wt% of CNC, CNC-Ac and CNC-PEG. Morphological analysis showed that the scaffolds presented porous structure and interconnected pores. The introduction of CNC, CNC-Ac and CNC-PEG caused reduction in porosity values due to the changes in the solution behavior during phase separation. It was also detected that the nanoparticles could not be well dispersed in the samples. The addition of CNC, CNC-Ac and CNC-PEG caused, in general, a slight increase in the crystallinity degree the scaffolds. In the uniaxial compression tests were obtained values compatible for application as human articular cartilage, spinal disc, trabecular bone and skin. Gas chromatography analysis showed that there is no residual solvent in the scaffolds, and this result was confirmed by the cell viability assays, which showed lack of cytotoxicity in the samples, and stimulated cell proliferation/activity, with cell viability values above 84%.