Fabrication of ZnO-MWCNT nanocomposite sensor and investigation of its ammonia gas sensing properties at room temperature

Abstract

Ammonia is one of the most hazardous gases, which plays a vital role in industry. Detection of low concentrations of this gas in the air is of particular importance for conservation and environmental purposes. In this study, ZnO-MWCNT nanocomposite is prepared by the in-situ method inclusive magnetron sputtering and spray pyrolysis. Then, its structural properties are studied regarding XRD spectra, FESEM, and EDX images. These studies show that nanotubes fill the porous spaces between ZnO nanoparticles and make the surface of the film rough. Hence, the surface area of the sensor and the probability of contact between gas and sensor increase. Also, sensing experiments are carried out for different concentrations of CH4 and CO gases at room temperature. Then, the results of this sensor for NH3 gas are compared with ZnO sensor results, which indicates that the sensitivity of ZnO-MWCNT sensor to NH3 is higher and more stable. However, its sensitivity to CH4 and CO is too low to be taken into consideration. Therefore, it can be claimed that MWCNTs could improve the sensing properties of ZnO film to detect NH3 gas with low concentrations such as 10 and 20 ppm. The response time and recovery time of ZnO-MWCNT sensor for 10 ppm of NH3 gas are 1.022, 13.687 s, and 107.109 s. Therefore, we suggest that ZnO-MWCNT nanocomposite could be used in a new generation of NH3 sensors.