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Development and performance analysis of substrates coated with metal-organic framework for gas sensing applications

Al Abdulla, Shamma Saqer Ibrahim
A Master of Science thesis in Mechanical Engineering by Shamma Saqer Ibrahim Al Abdulla entitled, “Development and performance analysis of substrates coated with metal-organic framework for gas sensing applications”, submitted in April 2023. Thesis advisor is Dr. Mehdi Ghommem and thesis co-advisor is Dr. Rana Sabouni. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
This thesis investigates the potential use of Zeolitic Imidazolate Frameworks (ZIF-8) as a sensing material for CO2 detection. Three synthesis techniques namely room temperature, microwave-assisted, and ball milling were explored for the preparation of ZIF-8. The latter is a green and facile alternative for synthesis with its solvent-free, room temperature operation. In addition, ZIF-8 samples produced through ball milling exhibited excellent CO2 adsorption and detection characteristics, as confirmed by fluorescence measurements. To understand the structural morphology, the thermal stability, and elements content of the different ZIF-8 samples, a range of characterization tests including XRD, FTIR, TGA, FE-SEM and EDS were conducted The characterization tests revealed the formation of a new phase of ZIF-8 (ZIF-L) when deploying the ball milling technique with different structure, morphology, response to CO2 exposure and thermal stability compared to its counterparts. The ZIF-8 samples obtained from the different ZIF-8 samples were evaluated in terms of limit of detection (LOD), selectivity, and recyclability using fluorescence measurements. The ZIF-8 sample synthesized based on ball milling had a LOD of 815.2 ppm, while the LODs of samples obtained from microwave and room temperature-based synthesis techniques were 1780.6 ppm and 723.8 ppm, respectively. This shows that the room temperature and ball milling produced MOFs with comparable LODs. However, the room temperature procedure requires the use of methanol, a harmful solvent. The range of LOD demonstrates the suitable use of ZIF-8 for indoor air quality monitoring and other industrial applications. Finally, the ZIF-8 obtained from ball milling was coated on a substrate using ball milling at different milling speeds 100 rpm, 300 rpm and 500 rpm. The 300 rpm sample resulted in a favorable coating and CO2 adsorption, thus, making it suitable to be deployed as a sensing layer for a miniature gas sensor.
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