Emerging zinc stannate and its application in volatile organic compounds sensing

The demand for real-time detecting volatile organic compounds (VOCs) has contributed to the rapid expansion of metal oxide semiconductor gas sensors. Among various metal oxides, zinc stannate with low visible adsorption (band gap similar to 3.1-3.9 eV), high electrical conductivity (similar to 104 S center dot cm(-1)) and electron mobility (10-15 cm(2)center dot V-1 center dot S-1) has been considered as a candidate sensing material for the analysis of VOCs. Herein, the crystal structure and sensing mechanism of zinc stannate towards the reducing VOCs are introduced. Besides, the drawbacks including low sensitivity, slow response/recovery speeds (similar to 1/2 min) and high working temperature (200-600 degrees C) of zinc stannate-based gas sensors towards VOCs are highlighted. Then strengthening methods including doping, surface modification, newly designed crystal structures, self-doping of oxygen vacancy are proposed to significantly enhance the sensing properties, represented by the reduction of working temperature, the improvement of sensitivity and selectivity, and the enhancement of humidity resistance, of zinc stannate-based sensing materials. Meanwhile, the limitations of these optimization strategies are also discussed. Most importantly, the working temperature should be reduced to a low temperature (25-100 degrees C) to avoid the damage of the unique structure of zinc stannate and/or the decomposition of the detected VOCs. Additionally, this work provides an insight into the challenge and future research direction of the application of zinc stannate-based gas sensors. It is ultimately excepted that this article can offer a basic theory for breaking the bottleneck of zinc stannate, and further push forward its large-scale application especially in disease screening or agricultural food quality inspecting.