Hexagonal/monoclinic phase junction modulated WO3 heterostructures for the detection of ammonia

Engineering the formation of phase junctions in the metal oxide is a powerful way to improve their gas-sensing performance. Here, we report a successful synthesis of different WO3 nanostructures. A simple and cost-effective hydrothermal technique was employed for the synthesis of monoclinic (m-WO3) and mixed hexagonal-monoclinic WO3 nanostructures (h-/m-WO3). The h-/m-WO3 exhibits a higher response than m-WO3 at 200℃. Among the various reducing gases, h-/m-WO3 is more sensitive toward ammonia whereas m-WO3 is sensitive toward H2S. The h-/m-WO3 device could detect a low ammonia concentration of 10 ppm and show spontaneous recovery, good repeatability, and long-term stability.