ZnFe₂O₄ Nanoparticles on ZIF-8-Derived ZnO for Enhanced Acetone Sensing

The development of uniform heterostructures for gas-sensing materials is promising to achieve both a fast response and recovery time at low gas levels and good selectivity at significantly high interference gas levels. Here we report the preparation of a ZIF-8-derived metal oxide semiconductor nanocomposite with a heterojunction structure and its application as acetone gas sensor. This heterojunction composite was fabricated through in situ growth of ZnFe2O4 nanoparticles (10-20 nm) on the outer surface of rhombic dodecahedral-shaped ZnO. Through the derivative strategy, the ZnFe2O4/ZnO heterojunction sensor had a high response value of 225 +/- 15 and a fast response time of 6 s to 100 ppm of acetone at the optimum working temperature of 260 degrees C. Furthermore, the response value reached 5.1 for only 1.8 ppm of acetone even under extremely high humidity (85%). To obtain a demonstration of the concept, an in-depth investigation of the sensing performances and the microstructure and surface state of ZnO and ZnFe2O4/ZnO heterojunction materials was carried out. We found that the excellent acetone sensitivity enhancement could largely be attributed to the ultrahigh number of free electrons and the abundant active sites generated by the tightly bound n-n heterojunction structure of ZnFe2O4/ZnO and the morphological characteristics. The large specific surface area of every sensing domain was the secondary factor in enhancing the gas-sensing properties. It suggests that this design for fabricating uniform and sensitive gas sensors may facilitate potential applications in detecting acetone gas.