Avaliação de ferritas de níquel e seus compósitos com nanotubos de carbono como sensor eletroquímico não enzimático para determinação de glicose

Abstract

Mellitus is one of the most common diseases in the world and it is necessary to monitor glucose levels found in biological fluids such as blood, urine, and saliva. Among the sensors for glucose monitoring, non-enzymatic ones have been highlighted due to advantages such as stability, high sensitivity, and reproducibility. In the development of non-enzymatic sensors, materials such as nickel ferrites (NiFe2O4) are used, which are mixed oxides that have the general formula MFe2O4 and whose main characteristic is the ability to act as electrocatalysts in the oxidation of organic molecules. However, this class of material usually has a low specific surface area and low electrical conductivity and therefore, obtaining composites between NiFe2O4 and multi-walled carbon nanotube (MWCNT) is an excellent strategy to overcome these challenges. Thus, this work aims at the synthesis of nickel ferrites through the co-precipitation method with hydrothermal treatment, and the application of this material in the development of a non-enzymatic sensor for glucose through the formation of a composite of NiFe2O4 and MWCNT. Synthesis with hydrothermal treatment resulted in inverse spinel-type NiFe2O4 particles, and changes in temperature and time of synthesis showed that increasing these conditions results in a material with a higher degree of crystallinity. The characterization of the composite by Raman spectroscopy confirmed the presence of NiFe2O4 and MWCNT. The area calculation performed using the Randles-Sevcik Equation showed that modifying the NiFe2O4 sample with 50% MWCNT increased the area of about 5 times (from 0.018 to 0.094 cm2). Electrochemical tests showed that the presence of NiFe2O4 makes the system more reversible. Glucose sensitivity also increases in the presence of NiFe2O4, where a value of 0.05419 μAL μmol-1 was obtained. Furthermore, the presence of NiFe2O4 increases the electrochemical response to glucose, obtaining a linear range from 50 to 600 μmol L-1 and an LD of 28 μmol L-1. The memory effect test demonstrated that the angular coefficients of the ascending and descending curves present similar values, evidencing the absence of the memory effect. The synthetic urine test showed a recovery value of 94.73% for the concentration of 300 μmol L-1.