A novel composite structure of WO_3 nanowires/ porous silicon has been successfully synthesized via a convenient thermal evaporation method without using any catalysts. The diameters and lengths of nanowires are 40-60 nm and 20-30 fim, respectively, and the aspect ratio (length/diameter) of nanowires could be in range of 500-750. The obtained products were investigated by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The response to NO_2 of WO_3 nanowires/porous silicon composite was investigated. It was found that the composite sensor had a good response to NO_2 at 50 °C. The lowest concentration of NO_2 detected was lppm and the response could be up to 6.17 at NO_2 concentration of 6 ppm. The novel composite structure improved sensing properties which are significant for future applications.
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