| In recent years, air pollution has been becoming more and more serious with the development of industry and the increase of people life. Recently, gas sensors based on tungsten trioxide have been considered as one of the most promising gas sensing materials to detecting NOx, O3, H2S, NH3, and so on owing to their simple structure, low cost, high sensitivity. On the other hand, the application investigation of the most promising WO3 gas sensing materials with one-dimensional nanostructures, especially for detecting H2, NH3 and CO gases is still rarely found in the literature. The present study will focus on the preparation of tungsten trioxide nanowires and the gas sensing properties for H2, NH3 and CO gases.Tungsten trioxide nanowires have been prepared by a simple hydrothermal method and the effects of reaction conditions on structures, morphology and BET surface area of nanowires have been studied. The optimum reaction conditions were obtained and the well-crystallized nanowires with diameter of about 10～20nm and length of up to several micrometers were obtained. The influence of slurry preparation, sintering process and electrode materials on the gas sensing properties of nanowires sensing film has been investigated in detail. The results show the films sintered at 350°C for 1h in air have good adhesiveness to Al2O3 base plate, well morphology and surface activity, which are the most excellent sensing films. Tungsten trioxide nanowire sensing film with various patterns have been directly prepared on AAO template by a new design method, which will afford a powerful theory basis for the rapid development and practicality of one-dimensional nanostructures metal oxides gas sensors.H2, NH3 and CO sensing properties and sensing mechanisms of the nanowire film operated at the temperature ranges from 200 to 350°C for low concentrations (5～100ppm) were investigated. The results indicate the film has high sensitivity,selectivity, good response-recovery characteristics and repeatability. Temperature is the important factor and its effect on sensitivity is more significant than that of gas concentration. The sensing mechanisms are mainly because of the adsorption, dissociation, desorption and reaction of reducing gases on the film surface.The atmosphere modification of WO3 thick film improved the morphology of the sensing materials as well as CO gas sensing properties. It shows that in some certain conditions atmosphere modification of sensors will be one of the effective means for improving the gas sensing properties of sensors when exploring new gas sensing materials.
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