Enhanced triethylamine sensing performance of α-Fe2O3 nanoparticle/ZnO nanorod heterostructures

Chemiresistive gas sensor with high sensitivity, selectivity and fast response for specific target gas has many applications from environmental monitor to internet of things. Herein, a highly sensitive and selective nanostructured triethylamine (TEA) gas sensor is fabricated successfully by designing semiconductor heterostructures consisting of ZnO nanorods and alpha-Fe2O3 nanoparticles. ZnO nanorods grow directly on flat Al2O3 electrodes and alpha-Fe2O3 nanoparticles are deposited onto ZnO nanorods by pulsed laser deposition (PLD). Such alpha-Fe2O3/ZnO sensor has larger specific surface area (20.79 m(2)/g), adsorbs more oxygen ions and exhibits higher response (63 to 50 ppm TEA), lower detection concentration (1 ppm), and shorter response time (4 s), which are all much better than the controlled ZnO nanorods sensor. Besides the interface depletion layer at the alpha-Fe2O3/ZnO interface, we find that the surface depletion layer due to oxygen absorption is also very important for the sensor performance. Moreover, more surface adsorbed oxygen in the alpha-Fe2O3/ZnO sensor is proved by both XPS analysis and density functional theory (DFT) simulation, which highlights the significance of gas sensing mechanism study for such composite heterojunction structure.