Ethanol gas sensor based on Al-doped ZnO nanomaterial with many gas diffusing channels

ZnO nanomaterial with multi-microstructures is synthesized by using normal pressure thermal evaporation and then doped with different Al₂O₃ contents by grinding in an agate mortar. The as-prepared Al-doped ZnO nanomaterials are characterized by X-ray diffraction and scanning electron microscopy. The characterization results show that all the compounds are wurtzite with hexagonal structure and are well crystallized. Channels/connecting holes arising from many kinds of ZnO microstructures are abundant. Both annealing and Al₂O₃-doping contributes to an increase in the quasi-one-dimensional and tri-dimensional microstructures. The as-prepared Al-doped ZnO nanomaterials show excellent gas responses to ethanol. The sensing mechanism of the ZnO-based nanomaterials with multi-microstructures is further analyzed by using the Effective Specific Surface Model. Excellent sensitivity (200) companied with short response time (8 s) and recovery time (10 s) to 3000 ppm ethanol is obtained with a ZnO-based sensor with 2 at.% Al₂O₃ at the operating temperature of 290 °C after the sensor is annealed at 500 °C.