Au-Decorated ZnFe₂O₄ Yolk-Shell Spheres for Trace Sensing of Chlorobenzene

Noble metals supported on metal oxides are promising materials for widely applying on gas sensors because of their enviable physical and chemical properties in enhancing the sensitivity and selectivity. Herein, pristine ZFO yolk-shell spheres composed of ultrathin nanosheets and ultrasmall nanoparticles decorated with nanosized Au particles with a diameter of 1-2 nm are fabricated using the method of solution-phase deposition-precipitation. As a result, the Au@ZFO yolk-shell sphere based sensor exhibits significantly sensing performances for chlorobenzene (CB). In comparison with pristine ZFO, the response (R_air/R_gas= 90.9) of a Au@ZFO based sensor with a low detection limit of 100 ppb increases 4-fold when exposed to 10 ppm chlorobezene at 150 °C. Excitingly, the sensing response for chlorobenzene is the highest among metal oxides semiconductor based sensors. Moreover, the sensors can be further applied in the field of chlorobenzene monitoring, owing to its outstanding selectivity. The results elaborated that the enhanced sensing mechanism is mainly attributed to the effects of electronic sensitization and chemical sensitization, which are induced by the Au nanoparticles on the surface of ZFO yolk-shell spheres. Density functional theory (DFT) calculations further illustrated that the existence of Au nanoparticles exhibits higher adsorption energy and net charge transfer for CB. In addition, the relationship between the sensing performances of pristine ZFO and Au@ZFO yolk-shell spheres for chlorobenzene and the factors of Au loading amount, operating temperature, and humidity was also fully investigated in this work.