Flower-like MoS₂-Induced α-Fe₂O₃/Fe₂(MoO₄)₃ Nanocomposite as an Ultrafast Sensor for Ethanol Detection

An ultrafast-responsive α-Fe₂O₃/Fe₂(MoO₄)₃ nanocomposite was developed for the detection of ethanol vapor. The α-Fe₂O₃/Fe₂(MoO₄)₃ nanocomposite was synthesized utilizing a green, normal-pressure, microwave-assisted method followed by an in situ solid-state reaction process with flower-like MoS₂ as a unique precursor. The resulting α-Fe₂O₃/Fe₂(MoO₄)₃ composite presents a porous, agminated petal-like structure with α-Fe₂O₃ nanoparticles homogeneously attached to the surfaces of Fe₂(MoO₄)₃ nanosheets. Systematic analyses have demonstrated that the α-Fe₂O₃/Fe₂(MoO₄)₃ composite excels in gas-sensing performance, exhibiting an ultrafast response/recovery, high sensitivity, and selectivity for ethanol vapor concentrations ranging from 1 to 50 ppm. The 5-Fe₂O₃/Fe₂(MoO₄)₃ sensor exhibits the best gas-sensing properties in comparison with sensors of other ratios. At an optimal temperature of 200 °C, the 5-Fe₂O₃/Fe₂(MoO₄)₃ sensor achieves a peak response to 50 ppm ethanol with an ultrafast response time of 5 s and a high response of 12.8. Notably, the sensor boasts a response time of an impressive 3 s to 50 ppm ethanol at 240 °C, while maintaining response times of under 6 s and recovery times within 1 min across the temperature range of 160 to 240 °C. In addition, the 5-Fe₂O₃/Fe₂(MoO₄)₃ sensor demonstrates good selectivity and long-term stability. The enhanced ethanol-sensing properties of the α-Fe₂O₃/Fe₂(MoO₄)₃ nanocomposite could be attributed to its unique three-dimensional porous structure, the synergistic effect between α-Fe₂O₃ and Fe₂(MoO₄)₃ species, and the presence of oxygen vacancy defects.