Synthesis of porous ZnFe₂O₄/SnO₂ core-shell spheres for high-performance acetone gas sensing

For developing promising gas sensing materials, constructing porous and heterojunction structures within the whole semiconductor oxide composites was an ideal strategy. However, it was always difficult because there existed grain boundaries. Herein, the pre-synthesized tiny SnO2 nanospheres could be evenly combined with ZnFe2O4 to form the ZnFe2O4/SnO2 (ZFO/SNO) composite with porous core-shell spheres structure via a simple solvent thermal reaction followed by the calcination treatment. Molar ratios of Zn to Sn were adjusted, and the resultant porous ZFO/SNO composites with different morphology were obtained, and their gas sensing properties were investigated and compared. The result indicated that the porous ZFO/SNO composite with a Zn to Sn ratio of 1:0.7 (ZFO/SNO-0.7) showed much better acetone sensing performance than that of bare porous ZnFe2O4 spheres and other ZFO/SNO composites. It exhibited a high response value of 120 to 100 ppm of acetone at 210celcius with good stability, and the detection limit can reach 0.1 ppm. The remarkable sensor performance of the porous ZFO/SNO-0.7 composite was attributed to its rich heterojunctions, porous structure and small nanoparticle size.