ZnO/MWCNT Sensors: Rejuvenation and Analysis of UV-Degassing Effects for Hydrocarbon Gases

In the recent decade, there has been a tremendous demand for the hydrocarbon gas sensors, in various industries as well as for home-monitoring. With the increasing incidence of industrial and household accidents and greater rise in the global warming in the recent years, it is crucial to continuously monitor the concentration of the harmful substances in the environment, hydrocarbons being the one. The thesis discusses on the Multi-walled Carbon nanotubes (MWCNT) based hetero-structure gas sensors functionalized with metal oxide (MOX) nanoparticles and their properties. UV-degassing and photo-activation of these hetero-structures are investigated for hydrocarbons detection. ZnO/MWCNT chemiresistive sensors are chosen for the study. The study focusses on obtaining faster recovery and improved sensitivity in order to achieve the baseline. The differences in UV-Degassing effects on the ZnO/MWCNT structures when exposed to Methane (CH4) and VOCs are discussed. It is observed that the UV degassing mechanism is oxygen dependent. MOX based gas sensors are limited by their low stability over time and long range signal drift, which leads to uncertain results and the need to recalibrate or replace the sensors frequently. The gradual aging occurs due to the presence of relative humidity in the ambient room temperature conditions and also, with continuous exposure to the target gas over the time. A process to rejuvenate the aged sensors was established and the results were analysed.