Synthesis of tungsten oxide nanowires/porous silicon composites and their application in NO2 sensors

Tungsten oxide (WO3) nanowires with diameters of 20-30 nm and lengths of 1-2 mu m were grown directly on the porous silicon (PS) through thermal annealing of tungsten film. The as-obtained WO3 nanowires/PS composites were investigated by field emission scanning electron microscopy and X-ray diffraction. The morphology of products was greatly affected by the annealing temperature, and the optimal annealing temperature was 700 degrees C. In addition, NO2-sensing properties of WO3 nanowires/PS composites were also investigated. It was found that the sensor based on WO3 nanowires/PS composites had a good response and selectivity to NO2 at a low operating temperature of 150 degrees C. The lowest concentration of NO2 detected was 250 ppb. The novel WO3 nanowires/PS composites improved sensing properties which are significant for future applications. (C) 2013 Elsevier B.V. All rights reserved.