Abstract
ZnO hollow microspheres with a diameter of approximately 1.4 μm were successfully synthesized by a facile one-step chemical precipitation method using trisodium citrate dihydrate as a morphology control agent. The ZnO hollow microspheres consisted of nanoplates and had good dispersibility. Control experiments revealed that trisodium citrate dihydrate played an important role in regulating the morphologies of ZnO products. The morphology of the ZnO product evolved from nanowires to hollow microspheres with the addition of trisodium citrate dihydrate. The sensor response of ZnO hollow microspheres toward 100 ppm n-butanol reached 86.6 at the optimum operating temperature of 340 °C, which was approximately three times higher than that of ZnO nanowires. In addition, the ZnO hollow microspheres also displayed good selectivity and long-term work stability toward n-butanol. The excellent gas sensing performance of ZnO hollow microspheres may be ascribed to the unique hollow sphere structure with high exposed polar crystal surface.
Highlights
ZnO, as a typical wide band gap (3.37 V) n-type metal oxide semiconductor, has been widely studied and utilized due to its advantages of low cost, good stability, and versatile design [1,2]
We examined the gas sensing properties of ZnO gas sensors with different microstructures, which were prepared by varying the amount of trisodium citrate dihydrate (TCD)
ZnO hollow microspheres with a diameter of approximately 1.4 μm were synthesized by a wet chemistry method at 90 °C
Summary
ZnO, as a typical wide band gap (3.37 V) n-type metal oxide semiconductor, has been widely studied and utilized due to its advantages of low cost, good stability, and versatile design [1,2]. Xu synthesized ZnO porous nanosheets with (0001) facets, which displayed enhanced ethanol gas sensing performance. ZnO with unique microstructures has been synthesized for enhancing gas sensing performance One dimensional nanostructures such as nanowires, nanorods, nanofibers; two dimensional nanostructures such as nanosheets, nanobelts, nanodisks; and three dimensional nanostructures such as nanoflowers, hierarchical structures, and nanospheres [20,21,22,23,24]. ZnO nano/microspheres with hollow structures have been seen as attractive for advanced gas sensors due to their high active surface area. It is obvious that polar surface and hollow microspheres are both beneficial in enhancing the gas sensing performance of ZnO. We tried to improve the gas sensing properties of ZnO by designing hollow microspheres with high active polar surface. The mechanism of improved gas sensing performance is discussed
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