Advancing the properties of selective and sensitive metal oxide based gas sensors is a challenging research topic for the detection of toxic, and pollutant gases. In the present research, we successfully deposited a three dimensional (3D) mesoporous ZnO nanostructure on a glass substrate by using a hydrothermal method, and tested the material for its gas sensing performance. These 3D mesoporous ZnO nanostructures were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and photoluminescence techniques. Gas sensing performance analysis was carried out for nitrogen dioxide (NO₂) gas at different temperatures and concentrations. The 3D mesoporous ZnO nanostructure revealed excellent gas sensing performance for NO₂ gas because of its large surface area. The larger surface area led to an increase in the gas sensitivity. In addition, the sensor based on the 3D mesoporous ZnO nanostructure could be used at a low operating temperature of 150 °C. This work suggests that the 3D mesoporous ZnO nanostructure is a versatile material for NO₂ gas sensing applications.

Novel hierarchical nanostructures of metal oxides have enormous potential in various applications. In this report, novel nanostructured maize-like ZnO was synthesized via a facile and economical modified successive ionic layer adsorption and reaction (M-SILAR) method and subsequent heat treatment at 300 °C for 30 min as a highly-sensitive NO₂ gas sensor. The M-SILAR technique described uses two bath solutions instead of the conventionally used four bath solutions. Their structural, morphological, and optical properties have been thoroughly characterized using advanced techniques such as X-ray diffraction, field-emission scanning electron microscopy and photoluminescence spectroscopy. The obtained hexagonal wurtzite ZnO structure appears as the hierarchical maize corn-like morphology with nano-granules. The ZnO maize based sensor contains numerous active sites, which afford beneficial conditions for gas adsorption and diffusion. Moreover, the synthesized sensor was proven to be an excellent NO₂ sensing material with high selectivity, superior sensitivity, and good response/recovery at relatively a low operating temperature. The peculiar structure of our sample, the preparation method and its nitrogen dioxide detection have wide application prospects.

In this report, 1-D interconnected CdS nanowires were prepared rapidly via a wet chemical route at relatively low temperature, using cadmium sulphate, thiourea and ammonia as raw materials. The formation of a CdS nanowire mesh (CdS NW mesh) and its structural, optical, surface morphological properties and elemental composition were studied by various characterization techniques. The cubic crystal structure of the CdS interconnected nanowire mesh was confirmed via X-ray diffraction and field emission scanning electron microscopy analysis. The photoluminescence spectroscopy measurements reveal the presence of defects in the as synthesized CdS NW mesh. However, the defect states are beneficial for the gas sensing behavior. Therefore, the gas sensing properties of the CdS NW mesh were studied using NO₂ as an analyte gas at moderate operating temperature. The nanowire mesh and inter-wire space were observed to play a crucial role in determining the gas sensing performance of the devices. The as synthesized CdS NW mesh shows a gas response of about 1850% to 100 ppm NO₂ gas. In particular, our CdS based gas sensor showed a fifty fold better gas response towards NO₂ gas than the earlier reports in the literature. Due to the high value of gas sensitivity, the reported CdS NW mesh could be a suitable candidate for NO₂ sensing.

NO₂ gas sensing mechanism of IZO nanorods synthesized by low cost and simple reflux method.