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Abstract: We reported a facile and controllable route to prepare nest-like ZnO without any complicate experimental equipments, pressure and gas control procedures. The nest-like ZnO was made within a muffle furnace in air atmosphere under normal pressure through a simple carbon thermal reduction reaction. The product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), field emission scanning electron microscope (FESEM) and photoluminescence (PL). The results showed that the product was wurtzite ZnO and had an interesting hollow nest-like microstructure with a prickly porous shell. The shell consisted of ZnO nanospheres, and a few ZnO nanorods grew on the shell surface. The gas sensing test indicated that the nest-like ZnO had an excellent gas sensing behavior toward ethanol. The response of the sensor to 50ppm ethanol was about 100, which was at least four times more than other gases. Moreover, even down to 1ppm ethanol, the response still reached 3.8. Both the response time and recovery time of the sensor were short. All of these proved that the nest-like ZnO is a promising gas sensing material for ethanol detecting. [Copyright &y& Elsevier]

Herein, we focused on the effects of exposed crystal planes on the gas sensing property of ZnO. For this purpose, we designed and synthesized two porous ZnO nanosheets with different exposed crystal facets (0001) and (10 1 ¯ 0) by a facile hydrothermal routes. The characterization results show that both the porous nanosheets have a near specific surface area about 7.5 m 2 /g, thickness about 100 nm, diameter about 5 μm and pore size of tens of nanometers. However, their dominating exposed crystal facets are (0001) and (10 1 ¯ 0), respectively. When employed them as sensing materials in gas sensors, porous ZnO nanosheets with dominating exposed (0001) facet exhibit a superior sensitivity than the (10 1 ¯ 0) one. The enhanced gas response is attributed to a large amount of oxygen vacancy defects and unsaturated dangling bonds existing in the ZnO nanosheets with exposed crystal facet (0001), which is favorable for the adsorption of gas molecular on the sensor surface and result in improvement of the gas response. Finally, the calculation of the chemisorption energy of oxygen on ZnO crystal facets also proves the reactive-facet-enhanced gas sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: A series of SnO2/V2O5 composites were designed and developed for selectively sensing BTEX (benzene, toluene, ethylbenzene, and xylol) based on a catalytic oxidation reaction. These composites were prepared with a facile solid phase reaction using sol–gel synthesized SnO2 and commercial V2O5 as raw materials. XRD and TEM were employed to characterize these composites. The results revealed forming process of the SnO2/V2O5 composites. Gas sensing tests of side-heating sensors showed that the SnO2/V2O5 composites had a much better response to BTEX rather than other VOCs such as ethanol, acetone, methanal, methanol and acetic acid compared with pure SnO2. Among these composites, the one containing 10wt% V2O5 has the best selectivity and response (R a/R g) toward BTEX. At 270°C, an optimal working temperature, the values of gas response to 50ppm (parts per million) BTEX are more than 5 times, meanwhile the limit of detection is as low as 0.5ppm. The influence of V2O5 on BTEX sensing of SnO2-based gas sensor was also discussed. [Copyright &y& Elsevier]