Navegando por Palavras-chave "Polianilina"
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- ItemAcesso aberto (Open Access)Desenvolvimento de sensores nanoestruturados baseados em compósitos de polianilina e óxido de grafenovisando o monitoramento de desreguladores endócrinos(Universidade Federal de São Paulo, 2022-03-11) Araújo, Gabriela Martins de [UNIFESP]; Simões, Fabio Ruiz [UNIFESP]; http://lattes.cnpq.br/4499541258914124; http://lattes.cnpq.br/1339110239980571Eletrodos baseados em polímeros condutores como a Polianilina (PAni) e grafeno têm sido cada vez mais usados em aplicações como sensores e dispositivos de armazenamento de carga. Na fabricação de eletrodos visando a aplicação em sensores esses materiais compósitos apresentam efeito sinérgico com a redução da resistência elétrica, promovendo aumento da sensibilidade, além de ocasionar o deslocamento de potenciais, proporcionando melhor seletividade quando aplicados como materiais de sensores. Neste trabalho, compósitos de PAni com diferentes formas de grafeno foram preparados visando a modificação de eletrodos por diferentes métodos como camada a camada, eletropolimerização e serigrafia. O óxido de grafeno (GO) foi produzido pelo método Hummers modificado e, em seguida, reduzido com o agente redutor ácido ascórbico e sulfato de hidrazina. Os compósitos foram produzidos por polimerização química in situ variando as relações de massa de 1,0%, 2,5% e 5,0% de óxido de grafeno reduzido (rGO) em relação ao monômero de anilina. Os materiais derivados do grafite bem como os materiais compósitos foram caracterizados por espectroscopia de infravermelho com transformada de fourier e espectroscopia Raman. Os resultados evidenciaram a formação dos materiais derivados do grafite bem como a dos compósitos a partir das bandas e picos característicos. Posteriormente, PAni e seus compósitos (PAni-X%rGO) foram utilizados para a modificação de substratos de vidro revestidos com óxido de estanho dopado com índio (ITO) por meio da técnica de camada a camada. Os substratos modificados foram caracterizados pelas técnicas de voltametria cíclica (CV), espectroscopia de impedância eletroquímica (EIS), espectroscopia no ultravioleta-visível e microscopia eletrônica de varredura. Os resultados indicaram o crescimento de filmes sobre o substrato revestidos com ITO, além de mostrar por análise eletroquímica que a concentração mais adequada é 1,0% de rGO na matriz polimérica, não alterando as propriedades redox da PAni. Eletrodos serigrafados flexíveis (SPE) também foram fabricados com tintas condutoras baseadas em misturas de resina alquídica (50%), grafite (45%) e PAni ou seus PAni-X%rGO (5,0%). No segundo método de modificação, o filme de PAni foi eletropolimerizado no SPE preparado usando uma tinta de grafite condutora (50%) dispersa em resina alquídica (50%) usando CV. Os filmes de PAni-GO foram preparados pela pré-dispersão do GO na solução de monômero, utilizando 2,5% e 5,0% em relação à anilina. Após a fabricação, os SPE modificados foram caracterizados por CV e EIS. Os resultados de CV para ambos os métodos de modificação dos SPE apresentaram picos característicos do comportamento redox da PAni, além dos resultados de EIS mostrarem uma diminuição significativa na resistência de polarização com o aumento da razão de massa GO ou rGO. Os resultados mostraram que o grafeno na matriz da PAni melhora o processo de transferência de carga. Assim, esses métodos desenvolvidos para produzir eletrodos baseados em compósitos de PAni e grafeno, com propriedades sinérgicas, é uma alternativa para aplicações como sensores na detecção do hormônio Progesterona e do pesticida Clorotalonil.
- ItemAcesso aberto (Open Access)Métodos alternativos para proteção à corrosão da liga de alumínio 2024-T3(Universidade Federal de São Paulo, 2015-03-06) Xavier, Thiago Henrique Andrade [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)This work presents the anti-corrosion behavior of a soluble copolymer of polyaniline (PAni), called poly (phenylene sulfide phenylamine) - PPSA, deposited on the Al 2024-T3 alloy. The motivation for the use of this copolymer is that it shows electroactivity similar to PAni, but it is soluble in various organic solvents, allowing its deposition by casting. Additionally, the anti-corrosion performance of polypyrrole (PPy) electrodeposited in ionic liquid was also studied. The use of ionic liquid as electrolyte was motivated because the Al alloy is not corroded in this medium. The efficiency of PPSA and PPy films in the corrosion protection of Al 2024-T3 alloy was investigated by open circuit potential tests, potentiodynamic polarization curves, electrochemical impedance spectroscopy, immersion tests and scanning electron microscopy. The PPSA film, in reduced form, produced with six subsequent depositions of its solution in tetrahydrofuran (4 mg/mL) resulted in the best performance against corrosion. Thicker films do not show satisfactory results due to their lower adhesion on the Al alloy. The PPSA film with six depositions was more compact and homogeneous, which afforded better performance in the corrosion protection, probably preventing the penetration of aggressive species, such as chloride ions. The PPy was efficiently electrodeposited on the Al 2024-T3 alloy by cyclic voltammetry. The morphology of this film was dependent on the scan rate used. The micrographs showed that in all experimental conditions, the films are quite porous, giving low efficiency of these coatings in the corrosion protection of the alloy.
- ItemAcesso aberto (Open Access)Preparação de nanopartículas de prata e seus compósitos com polímeros condutores m moldes flexíveis e líquidos iônicos(Universidade Federal de São Paulo, 2013-11-13) Correa, Cintia Marques [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Ionic liquids (IL), liquid salts at room temperature, show self-organization due to the electrostatic interactions between their ions and the van der Waals among the alkyl chains of the cationic species, being classified as structure directing agent for nanomaterials and polymers synthesis. This works will present the preparation, studying some synthetic parameters (different molar ratio between oxidant/monomer (K) and oxidant agent concentration (C)) of silver and two conductive polymers composites, called polyaniline (PANI), and polypyrrole (PPY), using as structure directing agent two ionic liquids, 1-butyl-3-methylimidazolium (BMIM) bis(trifluoromethanesulfonyl)imide (Tf2N) and tetrafluoroborate (BF4) and silver salts soluble in the LI . With the variation of the synthetic parameters was possible to evaluate their influence on the composites properties. PANI/Ag composites were obtained successfully and all characterizations confirmed the presence of PANI in the emeraldine form and metallic silver in nanoscale. Depending on the used conditions (K and C) electrical conductivity values ranged from 55 until 830 S.cm-1, which are higher than those of pure PANI. PPY/Ag composite exhibited electrical conductivity value around 10-1 S.cm-1. Silver nanoparticles were also prepared from Ag+ reduction using tetrabutylammonium borohydride in different ionic liquids based on imidazolium cations, called 1-butyl-3-methylimidazolium (BMIM) or 1-butyl-2,3-dimethylimidazolium (BMMIM) or 1-methyl-3-octylimidazolium (OMIM) bis(trifluoromethanesulfonyl)imide (Tf2N) and tetrafluoroborate (BF4). Although, nanoparticles have been obtained in all cited ionic liquids, in ionic liquids containing Tf2N. The dispersions showed greater stability than in IL containing BF4. The presence of polyvinylpyrrolidone (PVP) was crucial to increase the stabilization of the nanoparticles and at higher polymer concentration, the higher the nanoparticles stability. The dispersions are viscous and yellow, without precipitates and containing nanoparticles with diameters around 6-12 nm. Finally, tetrabutylammonium citrate was used for the preparation of silver nanoparticles, acting as both solvent as reducing agent. This method promoted the preparation of silver nanoparticles dispersions in the absence of any stabilizing agent, highly concentrated and containing nanoparticle with diameter of 2-6 nm.
- ItemSomente MetadadadosPreparação e avaliação de membranas de celulose com propriedades condutoras e microbicidas(Universidade Federal de São Paulo (UNIFESP), 2020-06-02) Oliveira, Roselaine Da Silva [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Universidade Federal de São PauloThere is a growing interest in developing methods that allow the immobilization of different types of materials (polymers and nanomaterials) in biopolymers. Among them, cellulose (CEL) is of the most indicated because it is natural, abundant, and non-toxic. In this thesis, new methods of immobilizing a conductive polymer and silver nanoparticles on cellulose membranes were developed. In order to overcome the insolubility and difficult processing of cellulose, in these procedures the biopolymer was dissolved in an ionic liquid called 1-butyl-3-methylimidazolium chloride (BMImCl). To simplify the comprehension of this thesis, it was divided into three chapters. In the first chapter (CHAPTER 1), the preparation of electrically conductive cellulose membranes, containing silver nanoparticles and polyaniline (PANI), which is a conductive polymer, will be shown. These membranes (CEL / PANI / Ag) showed high electrical conductivity and catalytic activity toward the reduction of p-nitrophenol. In the second chapter (CHAPTER 2), the preparation of several aqueous and non-aqueous dispersions (1-butanol) of silver nanoparticles (AgNP) with high metal concentration will be presented. A simple and fast method was developed, under mild reaction conditions. The dispersions presented excellent microbicidal activities. In the third chapter (CHAPTER 3) a new method of immobilizing the dispersions of AgNP produced in chapter 2 on cellulose membranes will be presented. These membranes will have their microbiological activity evaluated. An illustration of the chapters of thesis is in Figure 1.
- ItemAcesso aberto (Open Access)Preparação e avaliação de propriedades de materiais híbridos de celulose com polianilina e polióxido de etileno(Universidade Federal de São Paulo, 2017-12-11) Maeda, Vinicius Cavalheiro [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)In recent years, there has been a growing interest in the development of methods which employ biopolymers as support to immobilize other polymeric materials. Among the biopolymers, cellulose is one of the most used due to its abundance, non-toxicity, and because it is obtained from a natural resource. Nevertheless, due its insolubility in common solvents, the biopolymer is not easily processed. Therefore, the search for new methods to overcome this problem is very required. In this Project, it was showed new methods to prepare films of a modified cellulose, called hydroxypropyl methylcellulose (HPMC) and polyaniline (PANI) to be used as conductive papers (GOAL 1) and to obtain films of non-modified cellulose (CEL) and poly(ethylene oxide) (PEO) for lithium-ion batteries (GOAL 2). The films of HPMC and PANI were prepared in homogeneous medium (aqueous medium), where both HPMC and PANI were soluble. It was obtained self-supported and green films. The green color is characteristic of polyaniline on the most conductivity form, the emeraldine form. The films have showed electroativity characteristic of polyaniline and conductivity around 10-3Scm-1 . Therefore, they can be classified as conductive papers. It was also noted that the addition of HPMC in PANI, enhanced the mechanical properties of the films. Films of PEO containing different amounts of non-modified cellulose (CEL) were also prepared by a new method, where cellulose is dissolved in ionic liquid. The addition of cellulose decreased PEO crystallinity, as desired. However, the conductivity of the film of PEO containing 5% of cellulose and lithium salt showed values around 10-5Scm-1, which is not enough to be employed as electrolyte for lithium-ion battery.