Ultra-sensitive ethanol gas sensors based on nanosheet-assembled hierarchical ZnO-In₂O₃ heterostructures

Developing efficient sensing materials with super sensitivity and selectivity is imperative to fabricate high-performance gas sensors for satisfying future needs. Herein, we report the preparation of ultrathin nanosheet-assembled 3D hierarchical ZnO/In₂O₃ heterostructures for the sensitive and selective detection of ethanol by sintering the 3D hierarchical Zn/In glycerolate precursors consisting of ultrathin nanosheets synthesized through a facile solvothermal method. The obtained ZnO/In₂O₃ heterostructures were carefully characterized by XRD, SEM, HRTEM, BET and XPS. The results showed that the 20%ZnO/In₂O₃ heterostructure is built up by many ultrathin nanosheets composed of intimately connected ZnO and In₂O₃ nanoparticles and have a specific surface area as high as 137.1 m² g^-1. Because of the unique hierarchical structure, abundant mesoporous and formation of ZnO-In₂O₃ n-n heterojunctions, the 20%ZnO/In₂O₃ heterostructure based sensor was ultra-sensitive to ethanol gas at 240 °C and exhibited a response as high as 170 toward 50 ppm of ethanol, which is about 3.3 times higher than that of pure In₂O₃ based sensor. Moreover, the sensor based on 20%ZnO/In₂O₃ heterostructure has virtues of excellent selectivity, good long-term stability and moderate response and recovery speed (35/46 s) toward ethanol. Therefore, the ultrathin nanosheet-assembled 3D hierarchical heterostructures are promising materials for fabricating high-performance gas sensors.