ZnO quantum dots sensitized ZnSnO3 for highly formaldehyde sensing at a low temperature

Developing gas sensors for formaldehyde vapor detection is necessary. Metal oxide semiconductor (MOS) exhibited good formaldehyde sensing properties but with high working temperature and unsatisfactory selectivity. Herein, ZnSnO3 was sensitized by ZnO QDs modification for high-performance formaldehyde sensing at low working temperatures via simple immersion method. Meanwhile, SnO2 QDs instead of ZnO QDs was also modified on ZnSnO3 nanocubes. The result indicated both ZnO QDs and SnO2 QDs modification greatly improved gas sensing response and lower the working temperature of ZnSnO3 to formaldehyde. Whereas, the obtained ZnSnO3/ZnO QDs composite (ZSO/ZQD) containing 5 wt% ZnO QDs (ZSO/ZQD-0.05) showed a highest response value of 613.3–100 ppm formaldehyde at 70℃ with good reversibility and stability, which was nearly 20 times of bare ZnSnO3 and 6 times of SnO2 QDs modified ZnSnO3. The detection limit reached 100 ppb formaldehyde. The formaldehyde sensing performance of ZSO/ZQD-0.05 composite was checked in presence of simulated indoor pollutants. Its improved sensor performance was mainly attributed to ZnO QDs, which played roles in forming rich heterojunctions with ZnSnO3, increasing the surface area, and providing oxygen deficiency for formaldehyde sensing reaction. This provided an alternative way to improving the sensing properties of MOS by QDs modification.