Recent anthropogenic environmental destruction and ecological crisis are urgently demanding relevant gas sensors for detecting various harmful air pollutants including carbon oxides and nitrogen oxides. In the field of solid-state gas sensors, chemiresistive gas sensors based on semiconducting metal oxides have been extensively investigated since the observation of the gas sensing effect in zinc oxide (ZnO) films via a change in electrical resistivity for a variation of the gas composition by Seiyama et al. as early as 1962. Among useful semiconducting metal oxides as sensing materials, tin oxide and zinc oxide are known to be two of the most reliable materials in the fabrication of semiconducting metal oxide gas sensors for the detection of various gases. Here, our attention is focused on the detection of nitric oxide (NO) because the NO gas is an air pollutant produced by cigarette smoke, automobile engines and power plants. In this study, we report the NO gas sensing properties of the polycrystalline ZnO wire-like films synthesized by thermal oxidation of sputtered Zn nanowire films in dry air. Structural and morphological characterization reveal that we synthesize polycrystalline hexagonal wurtzite ZnO films of a wire-like nanostructure with a width of 100-150 nm and a length of several microns. It is found from the gas sensing measurements that the ZnO wire-like thin film gas sensor shows a significant high response with a maximum value of 29.2 for 2 ppm NO at 200 ºC as well as a reversible fast response to NO with a very low detection limit of 50 ppb. In addition, the ZnO wire-like thin film gas sensor also displays the NO-selective sensing response for NO, O₂, H₂, NH₃ and CO gases. Our results illustrate that the polycrystalline ZnO wire-like thin films are potential sensing materials for the fabrication of NO-sensitive high-performance gas sensors.

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