Synthesis and enhanced gas sensing properties of flower-like SnO2 hierarchical structures decorated with discrete ZnO nanoparticles

Flower-like ZnO/SnO2 hierarchical structures with different ZnO contents were successfully prepared via a flexible two-step synthesis method, in which nanosheets-assembled flower-like SnO microstructures were prepared in advance through a solvothermal method, and then were used as sacrificial templates to prepare ZnO/SnO2 composites by annealing with Zn(CH3COO)2⋅2H2O. Through the annealing process, the as-prepared flower-like SnO was oxidized to SnO2 without changing the morphology, and ZnO nanoparticles (NPs) with the size about 10-50 nm were simultaneously decorated on the surface of sheet-like SnO2 petals. The dispersion of ZnO NPs was found to have a close relationship with the ZnO content of ZnO/SnO2 composite. The gas sensing properties of the prepared ZnO/SnO2 composites with different ZnO contents were investigated. The composite with 10 wt.% ZnO exhibits remarkably higher sensitivity to ethanol than the pure SnO2 and the composites with 5 wt.% and 15 wt.% ZnO contents. The influences of ZnO NPs and ZnO/SnO2 heterojunctions on the gas sensing properties of ZnO/SnO2 composites were discussed.