Modelagem e aplicação de sensores interdigitados para determinação de aditivos em misturas pseudo binárias de combustíveis

Abstract

Mixtures of non-compliant fuels can be harmful to the environment and human health, in addition, can cause harm to car owners. In this sense, it is necessary to develop methodologies capable of certifying the quality of diesel sold in Brazil quickly and accurately. Thus, the development of sensory units of the type of interdigitated electrodes appears as an alternative to such demands. In order to reduce costs, interdigitated electrodes were simulated using the finite element method. After simulations and definition of better geometry, interdigitated electrodes were produced and used to determine the quality of pseudo-binary mixtures of biodiesel / diesel. Therefore, the electrodes were characterized as to structure, morphology and electrical properties. The structural characteristics of the electrodes were determined by analyzing the X-ray diffractograms, in which diffraction peaks similar to two distinct phases on the electrode surface were observed, being: Au0 (conductor) and SiO2 (dielectric substrate). Regarding the electrode morphology obtained by Scanning Electron Microscopy, it was possible to verify some irregularities in the electrode surface and edges, such defects were attributed to the interdigitated electrode manufacturing method. The roughness of the electrodes was evaluated by Atomic Force Microscopy and from it we can see that they have a uniform texture, allowing for future surface modifications/functionalization. The depth obtained was 225.71 nm ± 0.0032 nm. Regarding electrical characterization, greater sensitivity was observed when amplitude of 0.2 V and frequency of 104 Hz was used. Through the analysis of equivalent circuit, it was possible to observe the linear dependence between the resistance (R2) and the concentration of biodiesel in diesel. Therefore, an analytical curve was proposed to determine possible non-conformities in the pseudo-binary mixture of biodiesel/diesel. However, it is still necessary to evaluate the detection limit, limit of quantification and sensitivity for greater robustness and reliability of the obtained values. Thus, the present work aimed to apply interdigitated electrodes capable of evaluating compositional variations in liquid fuel mixtures via impedance spectroscopy measurements.