Enhanced NO2 gas sensing properties of WO3 nanorods encapsulated with ZnO

The influence of the encapsulation of WO3 nanorods with ZnO on the NO2 gas sensing properties was examined. WO3-core/ZnO-shell nanorods were fabricated by a two-step process comprising the catalyst-free thermal evaporation of a mixture of WO3 and graphite powders in an oxidizing atmosphere and atomic layer deposition of ZnO. Multiple networked WO3-core/ZnO-shell nanorod sensors showed the response of 281 % at 5 ppm NO2 at 300 °C. This response value was approximately 9 times larger than that of bare WO3 nanorod sensors at 5 ppm NO2. The response values obtained from the WO3-core/ZnO-shell nanorods in this study were more than 5 times higher than those obtained previously from the SnO2-core/ZnO-shell nanofibers at the same NO2 concentration range. The significant enhancement in the response of WO3 nanorods to NO2 gas by encapsulating them with ZnO can be accounted for based on the space-charge model.