Porous ZnO-SnO2-Zn2SnO4 heterojunction nanofibers fabricated by electrospinning for enhanced ethanol sensing properties under UV irradiation

An electrospinning technique followed by subsequent heat treatment with a high ramp rate (10 degrees C/min) was developed to construct porous ZnO-SnO2-Zn2SnO4 heterojunction nanofibers. Ethanol sensing results under UV light irradiation showed that the ZnO-SnO2-Zn2SnO4 nanofibers exhibited much higher response and lower operating temperature in comparison with the pure Zn2SnO4 nanofibers prepared with a low ramp rate of 2 degrees C/min. The response of ZnO-SnO2-Zn2SnO4 nanofibers to 200 ppm ethanol was up to 121.0 at 130 degrees C, which was 3.7 times higher than that of pure Zn2SnO4 nanofibers. The ethanol response of the ZnO-SnO2-Zn2SnO4 sensor can still up to 6.0-200 ppm under a high relative humidity of 82% at 130 degrees C. In addition, ZnO-SnO2-Zn2SnO4 heterojunction nanofibers also exhibited good ethanol reproducibility and selectivity. The enhanced sensing characteristics were mainly attributed to the synergetic effects of several factors including the formation of multiple n-n heterojunctions, increased oxygen species adsorption capacity, enhanced light absorption, reduced recombination rate of photoinduced electrons and holes, as well as increased specific surface area and porosity of ZnO-SnO2-Zn2SnO4 nanofibers. (C) 2020 Elsevier B.V. All rights reserved.