Desenvolvimento de eletrodos modificados baseados em compósitos de polipirrol e grafeno
Data
2021-09-24
Autores
Cardoso, Milton Alexandre 
Orientadores
Simões, Fabio Ruiz
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Eletrodos 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.
Electrodes modified with conducting polymers and graphene have been used in several applications such as in the preparation of charge storage devices and sensors. In the manufacture of sensors, electrodes based on composites of these materials can present a synergistic effect, such as decreasing the resistance to polarization, keeping the electronic and mechanical properties of conducting polymers. In this work, composites of polypyrrole (PPy) with reduced graphene oxide (rGO) were produced aiming at applicability as non-enzymatic environmental sensors. rGO was obtained by oxidation of graphite, exfoliation of graphite and subsequent reduction with hydrazine (N2H6SO4). PPy and its composites with rGO were produced varying the mass ratios of 2 and 5% of rGO in relation to PPy (PPy-2%rGO and PPy-5%rGO, respectively) by means of chemical polymerization in situ, using persulfate of ammonium, (NH4)2S2O8, as an oxidizer. Characterizations were performed by Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical characterizations were carried out by modifications by drop casting with PPy and hybrid inks, in glassy carbon electrode (GCE) and in screen-printed electrodes (SPE) and also by self-assembly (SA). The SPE manufacturing process was optimized using graphite and alkyd resin. The SPE were applied in the determination of Diuron. The results obtained in the characterizations confirmed the oxidation and reduction of graphite, obtaining rGO, as well as the fabrication of PPy and rGO hybrids. The SPE conductive ink compositions were optimized at 50% graphite and 50% alkyd resin using toluene (C7H8) as a solvent, resulting in an electroactive area of 1.82 cm². In the modifications with PPy or with PPy-2%rGO, the cyclic voltammograms exhibited characteristic profiles of PPy. The EIE results showed that the composite PPy-2%rGO had lower polarization resistance when compared to PPy. Diuron has been evaluated and shown to be dependent on protonation, with quantification and detection limits comparable to those in the literature. SPE modified with composite inks proved to be advantageous in relation to drop casting and SA techniques, as they are simpler and faster to be produced, in addition to offering the possibility of large-scale production.
Electrodes modified with conducting polymers and graphene have been used in several applications such as in the preparation of charge storage devices and sensors. In the manufacture of sensors, electrodes based on composites of these materials can present a synergistic effect, such as decreasing the resistance to polarization, keeping the electronic and mechanical properties of conducting polymers. In this work, composites of polypyrrole (PPy) with reduced graphene oxide (rGO) were produced aiming at applicability as non-enzymatic environmental sensors. rGO was obtained by oxidation of graphite, exfoliation of graphite and subsequent reduction with hydrazine (N2H6SO4). PPy and its composites with rGO were produced varying the mass ratios of 2 and 5% of rGO in relation to PPy (PPy-2%rGO and PPy-5%rGO, respectively) by means of chemical polymerization in situ, using persulfate of ammonium, (NH4)2S2O8, as an oxidizer. Characterizations were performed by Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical characterizations were carried out by modifications by drop casting with PPy and hybrid inks, in glassy carbon electrode (GCE) and in screen-printed electrodes (SPE) and also by self-assembly (SA). The SPE manufacturing process was optimized using graphite and alkyd resin. The SPE were applied in the determination of Diuron. The results obtained in the characterizations confirmed the oxidation and reduction of graphite, obtaining rGO, as well as the fabrication of PPy and rGO hybrids. The SPE conductive ink compositions were optimized at 50% graphite and 50% alkyd resin using toluene (C7H8) as a solvent, resulting in an electroactive area of 1.82 cm². In the modifications with PPy or with PPy-2%rGO, the cyclic voltammograms exhibited characteristic profiles of PPy. The EIE results showed that the composite PPy-2%rGO had lower polarization resistance when compared to PPy. Diuron has been evaluated and shown to be dependent on protonation, with quantification and detection limits comparable to those in the literature. SPE modified with composite inks proved to be advantageous in relation to drop casting and SA techniques, as they are simpler and faster to be produced, in addition to offering the possibility of large-scale production.
Descrição
Citação
CARDOSO, Milton Alexandre. Desenvolvimento de eletrodos modificados baseados em compósitos de polipirrol e grafeno. 2021. 99 f. Dissertação (Mestrado em Química - Ciência e Tecnologia da Sustentabilidade) - Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo, Diadema, 2021.