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UBC Theses and Dissertations

Development of SnO₂/PEO nanofiber gas sensor for THC detection Mehrabi, Pouria


This thesis presents the development of a metal oxide semiconductor (MOS) sensor for detection of volatile organic compounds (VOCs) which is of great importance in many applications involving either control of hazardous chemicals or noninvasive diagnosis. There are numerous methods for detection of VOCs where their efficacy is assessed by their sensitivity, selectivity, recovery time and portabily. Commercial MOS sensors are embedded in a housing, blocking the gas diffusion path and also limiting their application in the handheld VOC detectors. In this research, the sensor is fabricated based on tin dioxide (SnO₂)/ Poly Ethylene Oxide (PEO) using electrospinning. The sensitivity of the proposed sensor is further improved by calcination and gold doping. The gold doping of the composite nanofibers is achieved using sputtering, and the calcination is performed using a high temperature oven. The performance of the sensor with different doping thicknesses and different calcination temperatures is investigated to identify the optimum fabrication parameters resulting in high sensitivity. The results show that the sensing properties of the sensing layer, including response and recovery time, are significantly affected by the doping and calcination procedure. The optimum calcination temperature and duration are found to be 350°C and 4 hours, respectively. Also, the optimum thickness of the gold dopant is found to be 10 nm. The sensor with the optimum fabrication process is then embedded in a microchannel coated with several metallic and polymeric layers. The role of the channel is to enhance the selectivity of the sensor against different VOCs or mixtures. The performance of the sensor is compared against a commercial sensor. The comparison is performed for methanol and a mixture of methanol and Tetrahydrocannabinol (THC) which is the psychoactive element in cannabis. Segregation of the responses obtained for methanol and the mixture of methanol and THC is presented in a 3D feature space. It is shown that the proposed sensor outperforms the commercial sensor when it is embedded inside the channel. The proposed sensor integrated with the microchannel has a potential to be used as a breath analyzer for detection of THC in the breath. Keywords- Gas Sensor, electrospinning, SnO2 nanofibers, gold doping, sensitivity.

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Attribution-NonCommercial-NoDerivatives 4.0 International