Improved Performance of Acetone Gas Sensing through Oxygen Vacancy Formation of ZnO Nanoparticles
Authors: Kim Seong-Jun , Choi Youngmoon , Park Min-sun , Park Jong Hyeok , Lee Wooyoung 
Published: May 2020

Introduction

Recently, interest in gas sensors have been increasing in different fields of not only industry and medical applications but also development of smart city and detection of indoor air pollutants. In particular, acetone is a volatile organic compound (VOC) used as a biomarker to indicate various diseases in human exhalation, or has been importantly measured as one of the indicator gases for indoor pollution measurement [1]. Unlike industrial sensors that need to detect relatively high concentration gas, the detection of acetone for biomarkers requires highly sensitive sensing materials which can react with the gas quickly.
Metal oxide semiconductor (MOS) have been widely used as gas sensors because of their thermal and chemical stability and natural abundance. A lot of researches for detecting acetone gas using metal oxide semiconductor, for instance, WO3, SnO2 and ZnO through diverse method and morphology control, have been studied in recent [2]. Among them, ZnO is in the spotlight for various reasons due to their facile size and structure control, gas reactive surface and appropriate band gap. Many papers associated gas sensing of ZnO were published in multiple ways as metal doping and quantum dot control [3, 4]. In this study, oxygen vacancy was produced by simple H2O2 surface treatment of commercial ZnO, and the amount of oxygen vacancy by the degree of surface treatment was quantified. In addition, through evaluating acetone sensing performance according to the amount of oxygen vacancy, optimal vacancy amount showing significantly superior sensitivity was found. Chemical calculation described the reason of the outstanding response [5-8]. Further information will be discussed in detail.

Method

Surface oxygen vacancy is generated by a variety of H2O2 treatment with 400 ˚C annealing. ZnO controlled oxygen vacancy was reacted with 10 ppm acetone at 300 – 500 ˚C, and confirm response of the material. Response of varied temperature was confirmed through three or more repeated sensor measurements, and the measurement was performed at various concentration ranging from 0.01 ppm to 10 ppm under optimized temperature conditions. And the performance was identified under various humidity conditions and long-term stability.

Results and Conclusions

When H2O2 was treated on commercial ZnO, ZnO2 was produced. ZnO with oxygen vacancy was formed after 400 ˚C annealing on the obtained ZnO2. Treatment with high concentrated H2O2 results in more defects, breaking crystallinity and reducing the XRD peak sharpness. Therefore, we found optimal concentration conditions that create oxygen vacancy around the surface. The deficient oxygen and lattice oxygen peaks were deconvoluted from the O 1s peaks of the XPS spectrum and the vacancy to lattice ratio was obtained. Also, the formation of oxygen vacancy could be confirmed by the peak shift of Zn 2p3/2. The oxygen vacanced ZnO had a high sensitivity of 1692.1 (Fig. 1). This results showed the world’s best sensitivity compared with previous reported outcomes such as commercial ZnO (S=107), SnO2 nanorod arrays (S=511) and In-doped ZnO quantum dots (S=424). This study shows the possibility of commercialization through a simple surface treatment method that can be widely applied to a wide range of metal oxides, and it is widely applicable to systems of diverse fields where low concentrations of acetone have to be fairly sensitive.

References

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Figure 1