Hierarchical Nanoflowers of Colloidal WS2 and Their Potential Gas Sensing Properties for Room Temperature Detection of Ammonia

A one-step colloidal synthesis of hierarchical nanoflowers of WS2 is reported. The nanoflowers were used to fabricate a chemical sensor for the detection of ammonia vapors at room temperature. The gas sensing performance of the WS2 nanoflowers was measured using an in-house custom-made gas chamber. SEM analysis revealed that the nanoflowers were made up of petals and that the nanoflowers self-assembled to form hierarchical structures. Meanwhile, TEM showed the exposed edges of the petals that make up the nanoflower. A band gap of 1.98 eV confirmed a transition from indirect-to-direct band gap as well as a reduction in the number of layers of the WS2 nanoflowers. The formation of WS2 was confirmed by XPS and XRD with traces of the oxide phase, WO3. XPS analysis also confirmed the successful capping of the nanoflowers. The WS2 nanoflowers exhibited a good response and selectivity for ammonia.