Publicação
Designed multifunctional ionogels for gas sensing
| Resumo: | Ionic liquids and liquid crystals are emerging options in gas sensing due to the richness of their chemical structures, important for sensor selectivity, and to their dynamic self-assembly nature, as a response to gaseous analytes. Nonetheless, their physical state is a serious limitation to this application. This thesis focused on the development of new bio-based, sustainable materials based on the entrapment of ionic liquids within a 3D matrix (ionogel) or liquid crystal droplets within a biopolymeric matrix (hybrid gels) to be apply as sensitive layers in gas sensing and electronic nose technologies. In ionogels, the ionic conductivity reversible changes in the presence of volatile organic compounds (VOCs). In hybrid gels, there is a reversible optical reorientation in the ionic liquid-liquid crystal droplets. Gelatin hybrid gels were coupled with artificial intelligence algorithms to develop a custom-made electronic nose. Moreover, the tunability of gelatin-based ionogels and hybrid gels towards humidity sensing was modified by simply changing the ionic liquid anion. The use of more or less hygroscopic ionic liquids in the gels composition not only influenced the gel humidity sensitivity and VOC sensing capability but also its mechanical properties. Gelatin-based gels optical and electrical properties changed upon exposure to humidity and VOCs (ethanol, acetone, toluene and hexane) under dry and humidified environments, revealing to be complementary. We explored the use of simple biological molecules such as peptides to gelate ionic liquids. The newly developed tripeptide ionogels were first studied as a function of ionic liquid:water content, contributing to a deeper knowledge of the self-assembly process. Afterwards, we have rationally designed a peptide ionogel. Peptide ionogels were explored as sensing materials in a tailor-made electronic nose. Specifically, we have shown their potential to act as humidity sensor and to discriminate between volatile organic compounds under environmental conditions. Overall, this work shows the potential of new stimuli-responsive and sustainable bio-based materials in the development of electro-optical devices able to perform under environmental conditions, which are promising for innovative applications in gas sensing and in artificial olfaction. |
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| Autores principais: | Esteves, Carina Alexandra Marques |
| Assunto: | gelatin (tri)peptide ionic liquid liquid crystal ionogel hybrid gel |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade Nova de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório Institucional da UNL |
| Resumo: | Ionic liquids and liquid crystals are emerging options in gas sensing due to the richness of their chemical structures, important for sensor selectivity, and to their dynamic self-assembly nature, as a response to gaseous analytes. Nonetheless, their physical state is a serious limitation to this application. This thesis focused on the development of new bio-based, sustainable materials based on the entrapment of ionic liquids within a 3D matrix (ionogel) or liquid crystal droplets within a biopolymeric matrix (hybrid gels) to be apply as sensitive layers in gas sensing and electronic nose technologies. In ionogels, the ionic conductivity reversible changes in the presence of volatile organic compounds (VOCs). In hybrid gels, there is a reversible optical reorientation in the ionic liquid-liquid crystal droplets. Gelatin hybrid gels were coupled with artificial intelligence algorithms to develop a custom-made electronic nose. Moreover, the tunability of gelatin-based ionogels and hybrid gels towards humidity sensing was modified by simply changing the ionic liquid anion. The use of more or less hygroscopic ionic liquids in the gels composition not only influenced the gel humidity sensitivity and VOC sensing capability but also its mechanical properties. Gelatin-based gels optical and electrical properties changed upon exposure to humidity and VOCs (ethanol, acetone, toluene and hexane) under dry and humidified environments, revealing to be complementary. We explored the use of simple biological molecules such as peptides to gelate ionic liquids. The newly developed tripeptide ionogels were first studied as a function of ionic liquid:water content, contributing to a deeper knowledge of the self-assembly process. Afterwards, we have rationally designed a peptide ionogel. Peptide ionogels were explored as sensing materials in a tailor-made electronic nose. Specifically, we have shown their potential to act as humidity sensor and to discriminate between volatile organic compounds under environmental conditions. Overall, this work shows the potential of new stimuli-responsive and sustainable bio-based materials in the development of electro-optical devices able to perform under environmental conditions, which are promising for innovative applications in gas sensing and in artificial olfaction. |
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