Navegando por Palavras-chave "Polipirrol"
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- ItemRestritoDesenvolvimento de eletrodos modificados baseados em compósitos de polipirrol e grafeno(Universidade Federal de São Paulo, 2021-09-24) Cardoso, Milton Alexandre [UNIFESP]; Simões, Fabio Ruiz [UNIFESP]; http://lattes.cnpq.br/4499541258914124; http://lattes.cnpq.br/3661354851092629Eletrodos modificados com polímeros condutores (PCs) e grafeno têm sido utilizados em diversas aplicações como na preparação de dispositivos de armazenamento de carga e sensores. Na fabricação de sensores, eletrodos baseados em compósitos destes materiais podem apresentar um efeito sinérgico como a diminuição à resistência à polarização, além de manter as propriedades eletrônicas e mecânicas dos PCs. Neste trabalho, compósitos de polipirrol (PPy) com óxido de grafeno reduzido (rGO) foram produzidos visando a aplicabilidade como sensores ambientais não-enzimáticos. O rGO foi obtido pela oxidação do grafite, exfoliação do grafite e pela subsequente redução com hidrazina (N2H6SO4). O PPy e seus compósitos com rGO foram produzidos variando as razões massa de 2 e 5 % de rGO em relação ao PPy (PPy-2%rGO e PPy-5%rGO, respectivamente) por meio de polimerização química in situ, utilizando persulfato de amônio, (NH4)2S2O8, como oxidante. Foram realizadas caracterizações por espectroscopia Raman, espectroscopia no infravermelho por transformada de Fourier (FT-IR), microscopia eletrônica de varredura (MEV), voltametria cíclica (VC) e espectroscopia de impedância eletroquímica (EIE). As caracterizações eletroquímicas foram realizadas por modificações por drop casting com tintas de PPy e do híbrido, em eletrodo de carbono vítreo (GCE) e em eletrodos serigrafados (SPE) e também por automontagem (SA). O processo de fabricação do SPE foi otimizado utilizando grafite e resina alquídica. Os SPE foram aplicados na determinação de Diuron. Os resultados obtidos nas caracterizações comprovaram a oxidação e redução do grafite, obtendo rGO, bem como a fabricação dos híbridos de PPy e rGO. As composições da tinta condutora do SPE foram otimizadas em 50% de grafite e 50% de resina alquídica com o uso de tolueno (C7H8) como solvente, resultando em uma área eletroativa de 1,82 cm². Nas modificações com o PPy ou com o PPy-2%rGO os voltamogramas cíclicos exibiram perfis característicos do PPy. Os resultados de EIE mostraram que o compósito PPy-2%rGO apresentou menor resistência de polarização quando comparado ao PPy. O Diuron foi avaliado e demonstrou ser dependente da protonação, com limites de quantificação e detecção comparáveis com os da literatura. Os SPE modificados com as tintas dos compósitos mostraram-se vantajosos em relação às técnicas de drop casting e SA, pois são mais simples e rápidos de serem produzidos, além de oferecerem a possibilidade de produção em larga escala.
- ItemAcesso aberto (Open Access)Desenvolvimento de filmes automontados baseados em compósitos de polipirrol e nanotubos de carbono para o monitoramento de pesticidas em ambiente marinho(Universidade Federal de São Paulo, 2017-03-24) Araujo, Gabriela Martins de [UNIFESP]; Simões, Fabio Ruiz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The development of sensor materials for the monitoring of endocrine disruptors substances such as pesticides, using electroanalytical methods like voltammetric techniques, have low cost and time analysis as advantages as well as offering the possibility of in-situ monitoring. Conducting polymers have as their main characteristic the electrical conductivity which can be regulated in a wide range, through interactions with acceptor and donors of electrons, which makes them attractive as transducers or active. Among the different conducting polymers the Polypyrrole is one of the most studied in the development of sensors. Already the carbon nanotubes have the ability to promote electron transfer reactions, increasing reaction speed and decreasing oxidation potentials. Thus, materials based on conducting polymer composites and carbon nanotubes have been developed and present synergistic properties like the increase of sensitivity and selectivity in relation to its separate materials. The aim of this work was to develop and characterize self-assembled films based on Polypyrrole and carbon nanotubes composites deposited on substrates of glass covered with indium-tin oxide and carbon screen-printed electrodes to monitor Diuron and Chlorothalonil pesticides which are commonly used in marine environment. The self-assembled films were characterized using the techniques of Cyclic Voltammetry, Electrochemical Impedance Spectroscopy, UV-Visible Spectroscopy and Scanning Electronic Microscopy. The applicability of the sensors was evaluated using the electroanalytical techniques of Square Wave Voltametry and Differential Pulse Voltammetry. The results showed the composite film on printed electrode substrate had more definite voltammetric peaks due to the synergism between the Polypyrrole and the carbon nanotubes resulting in an increase of the polymer currents, the reduction of the capacitive current and the decrease of the transfer resistance of load. The results of the applicability showed the composite film in printed electrode presented better sensitivity compared to the film of Polypyrrole due to the carbon nanotubes in their structure in the presence of the pesticide Diuron detecting this herbicide in oxidation potential of 0,58V being smaller than the potential already known in the literature that is around 1,1V. The LOQ and LOD were respectively 2,584. 10-6 mol.L-1 and 7,83.10-7 mol.L-1 for the analytical curve for the peak at 0,58V on the printed electrode made from the composite film.
- 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.
- ItemAcesso aberto (Open Access)Síntese do polipirrol com surfactantes aniônicos visando aplicações como absorvedores de micro-ondas(Associação Brasileira de Polímeros, 2014-06-01) Campos, Regiane Aparecida Medeiros; Faez, Roselena; Rezende, Mirabel Cerqueira [UNIFESP]; Instituto Tecnológico da Aeronáutica; Universidade Federal de São Carlos Departamento de Ciências da Natureza, Matemática e Educação Laboratório de Materiais Poliméricos e Biossorventes; Universidade Federal de São Paulo (UNIFESP)In this work different samples of polypyrrole (PPy) were synthesized varying the combination of FeCl3 and Fe2(SO4)3 as oxidant agents and sodium dodecylbenzenesulfonate (DBSNa) and dodecylbenzenesulfonic acid (DBSA) as surfactants. Infrared spectroscopy analyses showed no significant differences in the chemical structures of synthesized PPy samples. However, thermogravimetric, electrical conductivity and X-ray diffraction analyses showed that the anionic surfactants favored the preparation of samples which are more thermally stable, conducting and with a more ordered crystallographic structure. Reflectivity measurements of PPy/epoxy resin blends, in the frequency range from 8 to 12 GHz, showed microwave attenuation up to 95% of the incident radiation.