Abstract
ZnO nanostructures with different morphologies (nanowires, nanodisks, and nanostars) were synthesized hydrothermally. Gas sensing properties of the as-grown nanostructures were investigated under thermal and UV activation. The performance of the ZnO nanodisk gas sensor was found to be superior to that of other nanostructures (Sg ∼ 3700% to 300 ppm ethanol and response time and recovery time of 8 and 13 s). The enhancement in sensitivity is attributed to the surface polarities of the different structures on the nanoscale. Furthermore, the selectivity of the gas sensors can be achieved by controlling the UV intensity used to activate these sensors. The highest sensitivity value for ethanol, isopropanol, acetone, and toluene are recorded at the optimal UV intensity of 1.6, 2.4, 3.2, and 4 mW/cm2, respectively. Finally, the UV activation mechanism for metal oxide gas sensors is compared with the thermal activation process. The UV activation of analytes based on solution processed ZnO structures pave the way for better quality gas sensors.
Highlights
The controlled synthesis of nanostructures has progressed rapidly in the past decade.Understanding the relationship between morphology, property, and application is very important to fabricate highly functional materials for practical devices
The sensing mechanism of metal oxide nanostructures is based on the activation of atmospheric oxygen on the surface at high temperatures
ZnO nanostructures such as nanowires (ZNWs) are single crystals growing along the [0001] direction as confirmed by the selected area electron diffraction (SAED) pattern in the inset of figure 1a and their side surfaces are nonpolar {10 ̅0} planes, as is typically reported in the literature.[1,2,3,4,5]
Summary
The controlled synthesis of nanostructures has progressed rapidly in the past decade.Understanding the relationship between morphology, property, and application is very important to fabricate highly functional materials for practical devices. The responses of the UV activated gas sensors to different ethanol concentrations at the optimum intensity are shown in figure 2d.
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