Template-free synthesis of hierarchical ZnFe2O4 yolk-shell microspheres for high-sensitivity acetone sensors.

Metal oxides with hierarchical microstructures have attracted tremendous attention with respect to their enhanced gas sensing properties. Herein, we reported the facile synthesis of hierarchical ZnFe2O4 yolk-shell microspheres via a template-free solvothermal strategy and the subsequent annealing and chemical etching process. Electron microscopy images undoubtedly demonstrated that the novel ZnFe2O4 architecture was constructed of a large number of nanosheet subunits with a thickness around 20 nm. As a proof-of-concept demonstration of the function, when evaluated as gas sensing materials, the as-prepared ZnFe2O4 yolk-shell microspheres manifested an extremely high response and a low detection limit to acetone at the operating temperature of 200 °C. Significantly, the response to 20 ppm acetone was retained well even after 200 cycles and continuous measurement for 30 days, indicating superior cyclability and long-term stability.