Desenvolvimento e aplicação de arranjos de nanossensores baseados em óxido de grafeno reduzido e nanopartículas de ouro para determinação eletroquímica de hidrazina

• Ano de defesa: 2020
• Autor(a) principal: Higino, Giane Silva
• Orientador(a): Pedrotti, Jairo José
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Presbiteriana Mackenzie
• Palavras-chave em Português: nanossensores; eletrodos modificados; rGO; nanopartículas de ouro; voltametria; hidrazina
• Área do conhecimento CNPq: CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Link de acesso: http://dspace.mackenzie.br/handle/10899/26441

Hydrazine (N2H4) is a volatile, flammable, water-miscible inorganic compound with great importance in fuel, catalysis, corrosion, agriculture and, pharmaceutical fields. More recently, due to its reducing activity, N2H4 has also been used as a reagent in the synthesis of nanomaterials, such as reduced graphene oxide - a nanomaterial with excellent chemical, mechanical and electrical properties, which has been used for fabrication of sensors, paints, and polymer films, electrodes for energy storage devices, among others. On the other hand, hydrazine presents high toxicity, and the development of fast, selective, and low-cost methods is attractive. This work describes a process of preparing gold microelectrodes modified with electrochemically reduced graphene oxide and gold nanoparticles (NPsAu) for the electrochemical detection of N2H4. For this purpose, the polymeric upper part of encapsulated electronic circuits with SMD (Surface Mounted Device) technology, provided with 8-20 terminals, was roughed using sandpaper with 800 - 2500 Mesh grain sizes until the exposure and rupture of gold microwires, which were originally used to do electrical contact between the active part of the CI and the external terminals of the chip. After the exposure of gold microdisks obtained from this mechanical process, the external terminals of the CI were welded to copper wires or in printed circuits and embedded in epoxy resin for making cylindrical or planar platforms. The characterizations of the gold substrate were carried out by optical and scanning electron microscopy, cyclic voltammetry and X-ray dispersive energy analysis (EDS-X). The modifications of the gold substrate were made by using two methods: (i) partial electrochemical reduction of graphene oxide (GO) 0.50 mg.mL-1 in Na2SO4 5 mmol.L-1 of support electrolyte and 0.05 mol.L-1 acetate buffer (pH 4.2) at potential range of +0.50 V at -1.20 V vs Ag/AgCl, followed by drop-casting of a solution of AuNPs 32 μmol.L-1 and (ii) partial electrochemical reduction of GO 0.50 mg.mL-1 and 0.30 mmol L-1 HAuCl4 in 0.010 mol.L-1 carbonate buffer (pH 9.0) on gold microdisks. The material characterization was made by UV-Vis and Raman spectroscopy and scanning electron microscopy (SEM) techniques. Better stability results with the modified nanosensors were obtained by using the method (ii). Using this strategy of modification, we prepared sensors that show a linear response to hydrazine in the concentration range of 20 to 140 μmol.L-1. The combination of a system of flow injection analysis (FIA) with amperometric detection allowed us to reach the limit of detection of 76 nmol.L-1 (3σ) with sample injections of 25μL. Under the 0.7 mL.min-1 flow rate of carrier solution, the analytical frequency was estimated at 65 determinations/hour. The new analytical system was used for N2H4 determination in tap water and laboratory liquid effluent samples.