Hierarchical Zinc Oxide Architectures: Synthesis And Gas Sensing Properties

Gas sensors based on semiconductor Oxide have the advantages of lowfabrication price, simple structure, high response and good stability. It is oneof the hot topic in the research field. Zinc Oxide (ZnO) is a typical n-typesemiconductor and has been wild used in many areas such as gas sensors. Ithas been found that the gas sensing properties of devices are stronglydependent on the morphology of the sensing materials. Therefore, themorphological study of different materials makes a great sense to theresearch and application of gas sensors.In this study, we present a facile hydrothermal method for the synthesisof the hierarchical ZnO. The as-prepared products were investigated in termsof the crystallinity, morphology, and structure. The gas sensing properties ofthe sensors based on the hierarchical ZnO nanostructure to some gases hadbeen investigated.First, the unique flower-like hierarchical zinc oxide architectures weresuccessfully synthesized from a mixture of zinc acetate dihydrate andhydrazine hydrate by a facile hydrothermal method. According to thetime-dependent experiment results, combined with the growth properties ofZnO, a possible formation mechanism of the three-dimensional ZnOhierarchical nanostructures was proposed. In addition, the gas sensingproperties of as-prepared products were investigated. It was found that thesensor based on flower-like ZnO nanostructure exhibited high response, and good selectivity to hydrogen sulfide at150℃.Furthermore, palladium chloride was used as the doping agent. Thedoping effect of Pd on the material morphology and sensing properties wasinvestigated. The SEM images indicated that with the quality of thepalladium increase, the morphology of as-prepared products turned fromflowerlike hierarchical nanostructures to fusiform ZnO nanostructure. Fieldemission scanning electron microscopic and transmission electronmicroscopic results revealed that the lengths of these fusiform nanorodswere4-6μm, the diameters were about500nm. All the synthesizedsamples had good dispersibility. As a comparative study, the gas sensingproperties to ethanol were investigated based on the pure and Pd-dopedfusiform ZnO materials. It is indicated that the Pd-doped ZnO sensorexhibits better gas sensing properties than the pure ZnO sensor. In addition,the sensor based on Pd-doped fusiform ZnO nanostructure exhibited goodselectivity, high response and quick response-recovery to ethanol at275℃.Finally, self-assembly hierarchical zinc oxide (ZnO) nanostructures wereprepared using zinc nitrate hexahydrate, sodium hydroxide as raw materialsthrough a hydrothermal method. It was found that the sensor based onself-assembly hierarchical ZnO nanostructure exhibited high response, andgood selectivity to hydrogen sulfide high response and quickresponse-recovery to hydrogen sulfide ethanol at150℃.According to the research work above, the growth mechanism and sensing properties of ZnO has been investigate. Based on the experimentresults, high quality of semiconductor gas sensor can be fabricated throughadjusting the surface morphology.