In this study, ZnO/TiO 2 nanosheets were synthesized using a hydrothermal method followed by annealing. The resulting hierarchical ZnO–TiO 2 heterostructures exhibited improved gas-sensing performance compared with pure ZnO. We demonstrated that tuning the ratio of Zn to Ti components in the heterostructure allowed us to adjust the sensor stability , with the best- performing sample having a Zn:Ti ratio of 2:1. A notable reduction was observed in both the sensor response and recovery times, down to 22 and 17 s, respectively, by utilizing nanosheet- structured ZnO/TiO 2 heterojunctions. To gain insight into the interaction between the sensing materials and formaldehyde (HCHO) molecules, we performed first-principles calculations to examine the density of states , charge transfer, and energy of adsorption. Our approach to constructing heterogeneous structures contributes to overcoming the low desorption efficiency and slow response-recovery time of pure ZnO for gas-sensing applications.
Lijia Zhao,Shupeng Sun,Su Zhang,Zhi Liu,Baoyu Huang,Nan Wang,Jianwei Zhang,Xiaogan Li
The hollow ZnO @ TiO 2 heterostructured nanospheres were synthesized by hydrothermal method using carbon nanospheres as sacrificed templates. With UV activation, the response of ZnO @ TiO 2 based chemiresistive-type sensors to 10 ppm formaldehyde is 11.02 at room temperature which is 5.48 times larger than that of the pure hollow ZnO. The response and recovery time significantly reduced to 14 s and 16 s. Selectivity, stability and repeatability of the hollow ZnO @ TiO 2 based sensor under UV-activation have also been examined. The sensing mechanism of the sensor to formaldehyde have been investigated by AC impedance spectroscopy , in-situ DRIFTS , and DFT theoretical calculation.
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