Gas Sensor with Nanostructured Oxide Semiconductor Materials

Metal oxides are often the choice for conductometric gas sensing due to their thermal and environmental stability as well as good response reversibility. Due to the fact that sensing with these materials relies on interactions with the surface, one strategy to enhance the sensitivity is to increase the surface area or active sites by decreasing their physical dimensions. Nanoscale metal oxides such as nanoparticles, nanospheres, nanotubes, nanobelts and nanowires are routinely synthesized for development of solid-state gas sensors with improved sensing properties. In this review, gas sensing applications of a variety of metal oxide nanostructures in various device configurations; bulk, two-terminal and field effect transistor (FET) sensors are presented. The application of nanostructures as building blocks for sensor can be achieved by implementing effective assembly and integration techniques to transfer the nanostructures from growth substrates onto their respective device substrates. Two common methods have been reviewed which include transfer printing and dielectrophoretic alignment of nanowires. In essence, these approaches employ external forces to align the nanostructures via dry and wet media respectively. Finally, the non conventional substrates sensors such as textile and free standing nanowire sheet are reviewed. The non conventional substrates have the advantages of being flexible, shock proof, wearable and portable etc.