WO3-SnO2 nanosheet composites: Hydrothermal synthesis and gas sensing mechanism

WO3-SnO2 nanosheet (NS) composites consisting of inner WO3 nanosheets surrounded by outer mixed phase SnO2 nanoparticles (NPs) were successfully synthesized by a simple two-step hydrothermal method. The density of SnO2 NPs on WO3 NSs can be controlled from sparse discrete state to complete shell structure by varying the amount of tin precursor. Apparent interface state density dependent gas sensing responses were observed for the WO3-SnO2 nanocomposites. The response of the WO3-SnO2 nanocomposites coated with complete SnO2 shell to 50 ppm acetone vapor is as high as 32.1, ∼10 times higher than that of the pristine WO3 NS sensor, with a response time less than 2 s. The improvement in response and selectivity of the WO3-SnO2 nanocomposite sensors upon exposure to acetone molecules can be mainly attributed to the multifunctional interfaces between WO3 NSs and SnO2 NPs, exposed special facets of WO3 NSs, core-shell type nanostructures as well as the special physical and chemical properties of acetone molecules.