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Sensores químicos para a detecção de compostos voláteis orgânicos e misturas binárias

Authors
  • Rodrigues, Rafael
Publication Date
Sep 14, 2018
Source
Repositório Digital Institucional da UFPR
Keywords
License
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Abstract

Abstract: In the last decades, devices were developed, to monitor changes in the concentration of volatile componds of the atmosphere. These devices, denominated sensors, have several applications in the industry, i.e., controlling the release of nocive substances to the environment, or even in the medicine, providing early detection of diseases and improving clinical analysis. In the first part of this thesis it is developed a pattern recognition technique, called generalized tristimulus analysis (GTA) which can be applied in the response of a set of three sensors, with either positive or negative sensitivities, in order to discriminate diferent analytes and binary mixtures of them, because it uncouple the response of the sensor from the concentration information. This technique was applied in literature data, applying in binary mixture of analyte problems, in order to test it robustness. In the second part of this thesis, it was experimentally characterized the sensing behavior of a set of three unspecific resistive sensors based on indium sulphide (?-In2S3), indium selenide (In2Se3) and reduced graphene oxide (rGO) for methanol, formaldehyde and formic acid and its capability to discriminate these analytes in binary mixtures. The sensors characterization was performed measuring the impedance of the devices in a dry nitrogen atmosphere (RH~15%) at room temperature (~ 23 °C). Low concentrations (from 5 ppm to 25 ppm) were used to determine the limit of detection and the limit of quantification of the sensors. An almost linear dependence of the responses with the analyte concentration was also observed at medium concentration, from 200 ppm to 2000 ppm. The binary mixture measurements were performed in the low relative concentration of 100%, 75%, 50%, 25% and 0% in the chamber, measuring the response in the saturation regime. It was compared the response obtained for mixtures with the expected response when independent responses are assumed, discussing deviations from this idealization. Keywords: Condensed matter physics. Organic electronic. Chemical sensors. Nanostructures. Carbon.

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