Desenvolvimento de sensores nanoestruturados baseados em compósitos de polianilina e óxido de grafenovisando o monitoramento de desreguladores endócrinos
Arquivos
Data
2022-03-11
Autores
Araújo, Gabriela Martins de 
Orientadores
Simões, Fabio Ruiz
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Eletrodos 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.
Electrodes based on conductive polymers such as Polyaniline (PAni) and graphene have been widely used in applications such as sensors and charge storage devices. In the manufacture of electrodes for application in sensors, these composite materials have a synergistic effect with the reduction of electrical resistance, promoting an increase in sensitivity, in addition to causing the displacement of potentials, providing better selectivity when applied as sensor materials. In this work, PAni composites with different forms of graphene were prepared aiming at electrode modification by different methods such as layer by layer, electropolymerization and screen printing. Graphene oxide (GO) was produced by the modified Hummers method and then reduced with the reducing agent ascorbic acid and hydrazine sulfate. The composites were produced by in situ chemical polymerization varying the mass ratios of 1.0%, 2.5% and 5.0% of reduced graphene oxide (rGO) in relation to the aniline monomer. Graphitederived materials as well as composite materials were characterized by Fourier transform infrared spectroscopy and Raman spectroscopy. The results showed the formation of graphitederived materials as well as the composites from the characteristic bands and peaks. Subsequently, PAni and its composites (PAniX%rGO) were used for the modification of tindoped indium oxide (ITO) coated glass substrates through the layerbylayer technique. The modified substrates were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ultravioletvisible spectroscopy and scanning electron microscopy. The results indicated the growth of films on the substrate coated with ITO, in addition to showing by electrochemical analysis that the most suitable concentration is 1.0% of rGO in the polymer matrix, not altering the redox properties of PAni. Flexible screen printed electrodes (SPE) were also manufactured with conductive inks based on mixtures of alkyd resin (50%), graphite (45%) and PAni or its PAniX%rGO (5.0%). In the second modification method, the PAni film was electropolymerized on the SPE prepared using a conductive graphite ink (50%) dispersed in alkyd resin (50%) using CV. The PAniGO films were prepared by predispersing GO in the monomer solution, using 2.5% and 5.0% in relation to aniline. After fabrication, the modified SPEs were characterized by CV and EIS. The CV results for both SPE modification methods showed peaks characteristic of the redox behavior of PAni, in addition to the EIS results showing a significant decrease in polarization resistance with increasing GO or rGO mass ratio. The results showed that graphene in the PAni matrix improves the charge transfer process. Thus, these methods developed to produce electrodes based on composites of PAni and graphene, with synergistic properties, are an alternative for applications such as sensors in the detection of the hormone Progesterone and the pesticide Chlorothalonil.
Electrodes based on conductive polymers such as Polyaniline (PAni) and graphene have been widely used in applications such as sensors and charge storage devices. In the manufacture of electrodes for application in sensors, these composite materials have a synergistic effect with the reduction of electrical resistance, promoting an increase in sensitivity, in addition to causing the displacement of potentials, providing better selectivity when applied as sensor materials. In this work, PAni composites with different forms of graphene were prepared aiming at electrode modification by different methods such as layer by layer, electropolymerization and screen printing. Graphene oxide (GO) was produced by the modified Hummers method and then reduced with the reducing agent ascorbic acid and hydrazine sulfate. The composites were produced by in situ chemical polymerization varying the mass ratios of 1.0%, 2.5% and 5.0% of reduced graphene oxide (rGO) in relation to the aniline monomer. Graphitederived materials as well as composite materials were characterized by Fourier transform infrared spectroscopy and Raman spectroscopy. The results showed the formation of graphitederived materials as well as the composites from the characteristic bands and peaks. Subsequently, PAni and its composites (PAniX%rGO) were used for the modification of tindoped indium oxide (ITO) coated glass substrates through the layerbylayer technique. The modified substrates were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ultravioletvisible spectroscopy and scanning electron microscopy. The results indicated the growth of films on the substrate coated with ITO, in addition to showing by electrochemical analysis that the most suitable concentration is 1.0% of rGO in the polymer matrix, not altering the redox properties of PAni. Flexible screen printed electrodes (SPE) were also manufactured with conductive inks based on mixtures of alkyd resin (50%), graphite (45%) and PAni or its PAniX%rGO (5.0%). In the second modification method, the PAni film was electropolymerized on the SPE prepared using a conductive graphite ink (50%) dispersed in alkyd resin (50%) using CV. The PAniGO films were prepared by predispersing GO in the monomer solution, using 2.5% and 5.0% in relation to aniline. After fabrication, the modified SPEs were characterized by CV and EIS. The CV results for both SPE modification methods showed peaks characteristic of the redox behavior of PAni, in addition to the EIS results showing a significant decrease in polarization resistance with increasing GO or rGO mass ratio. The results showed that graphene in the PAni matrix improves the charge transfer process. Thus, these methods developed to produce electrodes based on composites of PAni and graphene, with synergistic properties, are an alternative for applications such as sensors in the detection of the hormone Progesterone and the pesticide Chlorothalonil.