Hydrothermal synthesis porous silicon/tungsten oxide nanorods composites and their gas-sensing properties to NO₂ at room temperature

Highlights: • Porous silicon is prepared (PS) by a double groove electrochemical etching method. • PS/WO₃ nanorods composite is synthesized by a seed-induced hydrothermal method. • The morphology of WO₃ nanorods depends on the annealing temperature of seed layers. • The results show a high response and good selectivity to NO₂ at room temperature. - Abstract: In this paper, well-ordered one-dimensional single crystalline hexagonal WO₃ nanorods were synthesized directly on the porous silicon substrates by a seed-induced hydrothermal method without using any template, catalyst. And the effect of the annealing temperature of WO₃ seed layers on the microstructure and NO₂-sensing properties was studied. The morphology and crystal structure of the porous silicon/WO₃ nanorods composites were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The gas-sensing properties of the porous silicon/WO₃ nanorods composite gas sensors to NO₂ with the concentration ranging from 100 ppb to 3 ppm were examined. The results indicate that well-ordered WO₃ nanorods can greatly improve the gas-sensing properties of the sensor. The sensor exhibited a high response (∼3.38) and excellent selectivity toward 1 ppm NO₂ at room temperature. And the NO₂-sensing mechanism of this sensor was further explained.