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Faculty of Graduate Studies

Amirhossein Alaghmandfard

  • BSc (Sharif University of Technology, 2018)

  • MSc (Sharif University of Technology, 2020)

Notice of the Final Oral Examination for the Degree of Master of Applied Science

Topic

Effect of Au Nanoparticles on Mitigating Negative Effect of Humidity on ZnO-Based Gas Sensors

Mechanical Engineering

Date & location

  • Thursday, January 11, 2024
  • 12:00 P.M.
  • Engineering Computer Science Building
  • Virtual Defence

Reviewers

Supervisory Committee

  • Dr. Mina Hoorfar, Department of Mechanical Engineering, University of Victoria (Supervisor)

  • Dr. Makhsud Saidaminov, Department of Mechanical Engineering, UVic (Member)

External Examiner

  • Dr. Sushanta Mitra, Department of Mechanical & Mechatronics Engineering, Waterloo Institute for Nanotechnology 

Chair of Oral Examination

  • Dr. Jay Cullen, School of Earth and Ocean Sciences, UVic

Abstract

This thesis presents ZnO-based gas sensors for the detection of analytes, using Au nanoparticles to reduce the destructive effects of humidity on gas detection. The ZnO nanostructures are fabricated using the thermal decomposition method for different lengths of time and at varying temperatures. These structures are characterized by the X-ray diffraction technique, revealing the wurtzite hexagonal close-packed ZnO structures. In addition, scanning electron microscopy is employed to characterize the morphology of the synthesized ZnO structures. The results show that the length of ZnO nanostructures increases by raising the calcination temperature for 12 hours. The changes in the electrical current of the sensor are studied to determine the presence of target gases at various concentrations. The results show that the ZnO nanostructures prepared at 380 oC revealed the best response toward different humidity levels due to a higher number of oxygen vacancies, which are perfect sites to react with the target gas molecules. After selecting the best ZnO-based sensor, Au nanoparticles are sputtered onto the ZnO nanostructures with different thicknesses. Based on the results, the 0.1-nm-thick Au layer creates the best sensors to reduce the effect of humidity while demonstrating a constant response toward the target gas at different humidity levels. The sensor also shows good sensitivity and selectivity toward the triethylamine gas target with a response of 17.57, which is 62.75, 60.59, 4.81, 8.29, 4.30, 42.85, 70.28, and 292.83 times higher than the response toward Acetone, Methanol, Diethyleneamine, Benzene, Toluene, Ethanol, 1-propanol, and H2, respectively. This sensor revealed fast response and recovery times of 4.4 s and 9.8 s, respectively and promising stability over 24 days.

 

Keywords: Zinc Oxide Semiconductors, Au Nanoparticles, Triethylamine, Gas Sensor, Humidity Effects

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