Tungsten oxide nanostructures and thin films for optical gas sensors

Identifier:  TDX:1393

Handle: https://hdl.handle.net/20.500.11797/TDX1393

Authors:  Qadri, Muhammad Usman

Abstract:
n this doctoral thesis, WO3 based thin films and nanostructures have been investigated for optical gas sensing. The nano structured material synthesis, device fabrication and their gas sensing properties have been studied. WO3 thin films with thicknesses around 550 nm, grown by RF sputtering have been investigated for optical gas sensing using absorbance spectroscopy. These films were doped with Pt nanoparticles and subjected to optical gas sensing under the influence of H2, CO and NOx. These films showed fast response and recovery under the influence of mentioned gases. The response and recovery time is in the range of seconds. The bare WO3 films show a measureable optical response to NOx. The films doped with Pt nanoparticles show a response to H2 at room temperature. Similarly, the gasochromic response of WO3 nanoneedles was investigated upon the exposure to NH3. The nanoneedles decorated with Au and Pt show optical response when exposed to NH3 gas at room temperature. The optical response at room temperature of these nanoneedles is presented in this doctoral thesis for the first time. Similarly to thin films, nanoneedles have also shown a fast response and recovery time in the range of seconds. In summary, this PhD research program successfully fulfilled its objectives to investigate and develop novel WO3 optical sensors based on nanostructures and thin films. During the work the author has successfully employed this material for optically sensing the mentioned gases such as NH3, CO, NOx, and H2. The evaluation of these results indicates that WO3 is a good candidate for designing future devices for optical gas sensing.