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 α-Fe2O3 nanoparticles. ZnO nanorods grow directly on flat Al2O3 electrodes and α-Fe2O3 nanoparticles are deposited onto ZnO nanorods by pulsed laser deposition (PLD). Such α-Fe2O3/ZnO sensor has larger specific surface area (20.79 m2/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 α-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 α-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.