ZnO nanoplates surfaced-decorated by WO 3 nanorods for NH 3 gas sensing application

Zinc oxide (ZnO) nanoplates and tungsten trioxide (WO 3 ) nanorods were synthesized by hydrothermal treatment from zinc nitrate/potassium hydroxide and sodium tungstate/hydrochloric acid, respectively. The structure, morphology and compositions of the as-prepared WO 3 /ZnO nano-composites were characterized by x-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The obtained ZnO nanoplates have regular shape, single-crystal wurtzite structure with the thickness of 40 nm and 200 versus 400 nm in lateral dimensions. The WO 3 nanorods possess the average diameter of 20 nm and the length of approximately 120 nm which were distributed on the surfaces of ZnO nanoplates. The WO 3 /ZnO nano-composites were prepared by grinding WO 3 nanorods powder with ZnO nanoplates powder in various weight ratios (1:2, 1:1 and 2:1). The NH 3 gas sensing properties of WO 3 /ZnO nano-composites were examined through the electrical resistance measurement. The gas sensing performance of the WO 3 /ZnO composite with weight ratio of 1:1 was better compared with that of other samples. For this sample, the maximum response to 300 ppm NH 3 was 24 at the operating temperature of 250 °C. In addition, the gas sensing mechanism of the WO 3 /ZnO composites was discussed.