Compósitos nanoestruturados baseados em polímero condutor/cerâmica como plataforma sensorial para detecção de gás amônia

Abstract

The development of novel nanostructured platforms for application as gas sensor has intensified over the last few decades. In this scenario, it is worth mentioning the importance of monitoring ammonia gas in poultry farms. Such environments are rich in ammonia, carbon monoxide, hydrogen sulfide, and organic matter arising from the poultry waste decomposition, which remain in the air as bioaerosol. Ammonia, which is produced by the microbial degradation of uric acid present in the poultry waste, causes significant economic losses to poultry farmers and is harmful to the workers. Although some studies found in the literature present sensors capable to detect low concentrations of ammonia, it is still necessary to optimize these devices in order to improve their performance in terms of the sensitivity, limit of detection (LOD) and reliability. Thus, the present thesis aims to contribute to the development of sensors with high sensitivity and low LOD for detecting ammonia through the study of different nanostructured platforms. Zinc oxide (ZnO) nanoparticles were obtained through the optimization of the synthesis and treatment parameters using conventional hydrothermal method, while polymeric nanofibers were produced by electrospinning technique. Both techniques allowed to produce nanostructured platforms by a combination of ZnO nanoparticles and conjugated polymers in the form of fibers, film and coating architecture. The sensitivity and performance of such platforms were evaluated against different concentrations of ammonia aiming to understand the heterojunction influence among the materials on the performance of the platforms as an ammonia sensor at room temperature. Both the ZnO nanoparticles and the composite platforms developed in this work had their structural, morphological and electrical properties studied in detail. Synthesis parameters as well as the platforms deposition parameters were optimized for attaining superior electrical and morphological properties that improved the sensor performance regarding ammonia detection. Sensing tests were carried out against different concentrations of ammonia under controlled atmosphere confirming the best performance of the composite materials when compared to their constituents separately. In this context, the influence of the platform composition, as well as materials structural conformation were evaluated to help to understand the electrical properties and detection mechanisms.