IMB-CNM Thesis: Semiconducting metal oxide structures with surface nanoscale interfaces for gas sensing
Milena Tomić.
- Thesis director: Stella Vallejos Vargas
- Research group: MESSI
- University: Universitat Autònoma de Barcelona
Abstract
Sensor technologies contribute to raising living standards and quality of life. In gas sensors, the exploitation of this potential needs, amongst others, the contribution of precise synthesis procedures for nanomaterials to provide sensitivity, selectivity, stability, and power efficiency to the sensor. Hence, this thesis presents strategies for developing optimized gas-sensitive semiconducting metal oxides (SMOXs) for chemoresistive gas sensors. The work focuses on different n-type SMOx structures synthesized via bottom-up techniques and their surface modification. The SMOXs included in this study are WO3, ZnO, and Fe2O3 tuned morphologically to obtain high surface-to-volume-ratio films. Initially, the thesis deal with the influence of surface interfaces formed by these host SMOXs with metal nanoparticles or other n-type or p-type SMOXs such as CeO2, Fe2O3, and CuO on the gas sensing properties. In the second stage, the studies are directed to explore the sensing properties of interfaces formed by the host SMOX and organofunctional molecules, taking as study case WO3 nanowires modified with (3-aminopropyl)triethoxysilane (APTES). The thesis centers the discussion on the sensing mechanism of these modifications and their impact on sensing gases such as nitrogen dioxide, acetone, and ethanol, which are of high importance in air quality, medicine, or food safety. Results validate the materials and methods to fabricate miniaturized gas sensors and the paths to tune the sensor performance and operating temperature by incorporating controlled interfaces at the SMOXs' surface.