Design, fabrication and evaluation of photo-activated gas sensors based on semiconducting nanostructures
department or school: Applied Science, Faculty of
department or school: Chemical and Biological Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Espid, Ehsan
issued: 2021-08-31T07:00:00Z
issued: 2020
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: In this research, UV-LED-activated metal-oxide gas sensors were studied, where the electrochemical properties of the sensing material were enhanced by manipulation of sensor operating parameters as well as material structure and composition. In the first phase, the sensing characteristics of several favorable metal oxide semiconductors were investigated under different wavelengths, irradiances, and pulsation frequencies. The results showed that UVA-LEDs (i.e. 365 nm) could result in better responses due to resonant absorption. At a constant photon energy (i.e. 3.4 eV), increasing irradiance enhanced the photo-desorption of adsorbed components and reduced the response. Pulsed UV irradiation could significantly enhance the response as a result of increased residence time of adsorbates. Also, a set of strategies were applied to investigate and modify the sensing layer structure and composition. Firstly, Ag was incorporated into ZnO nanoparticle structure which resulted in an increase in sensor response toward 5 ppm NO₂ (ΔR/R = 0.98), compared to pristine ZnO (0.5) potentially due to layer charge carrier enhancement. Secondly, a sensing material structure was designed based on ZnO nanowires decorated with Pt nanoparticles, as metallic co-catalytic sites. The ZnO nanowires showed an increased response (1.6) compared to nanoparticles due to their higher surface area. Furthermore, decorating the surface of ZnO nanowires with Pt nanoparticles remarkably enhanced the sensing performance, whereas 0.1 wt% Pt decorated ZnO nanowires sensor exhibited nearly 4-times higher and 50s faster response compared to ZnO nanoparticles, in identical photo-activation settings. Thirdly, ZnO nanowires were used as a core for a thin layer of a secondary semiconductor to develop ZnO-In₂O₃ and ZnO-SnO₂ core-shell gas sensors. The relative responses of the ZnO-In₂O₃ (2.49) and ZnO-SnO₂ (2.21) sensors were higher than that of pristine ZnO NWs (1.6), possibly due to the improved photon absorption, …
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/75678
note: i Design, Fabrication and Evaluation of Photo-activated Gas Sensors based on Semiconducting Nanostructures by Ehsan Espid B.A.Sc., University of Tehran, 2012 M.A.Sc., University of Tehran, 2014 M.A.Sc., University of British Columbia, 2015 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (CHEMICAL AND BIOLOGICAL ENGINEERING) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) © Ehsan Espid, 2020 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the dissertation entitled: Design, Fabrication and Evaluation of Photo-activated Gas Sensors based on Semiconducting Nanostructures submitted by Ehsan Espid in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical and Biological Engineering Examining Committee: Fariborz Taghipour, Chemical and Biological Engineering Supervisor John Madden, Electrical & Computer Engineering Supervisory Committee Member David Wilkinson, Chemical and Biological Engineering Supervisory Committee Member Peyman Servati, Electrical & Computer Engineering University Examiner Előd Gyenge, Chemical and Biological Engineering University Examiner iii Abstract In this research, UV-LED-activated metal-oxide gas sensors were studied, where the electrochemical properties of the sensing material were enhanced by manipulation of sensor operating parameters as well as material structure and composition. In the first phase, the sensing characteristics of several favorable metal oxide semiconductors were investigated under different wavelengths, irradiances, and pulsation frequencies. The results showed that UVA-LEDs (i.e. 365 nm) could result in better responses due to resonant absorption. At a constant photon energy (i.e. 3.4 eV), increasing irradiance enhanced the photo-desorption of adsorbed components and reduced the response. Pulsed UV…
has type: Thesis/Dissertation
date issued: 2020-11
is shown at: 10.14288/1.0392947
language: eng
degree discipline: Chemical and Biological Engineering
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/75678