| Ammonia is a common colorless toxic gas with pungent odor,which is usually produced in industrial refrigeration,automobile exhaust,etc.when people are exposed to 25 ppm ammonia for 8 h or even 35 ppm ammonia for 15 min,human eyes,skin,lung and respiratory system will be seriously damaged.In various fields of safety protection in production and life,real-time detection,monitoring or leakage alarm of ammonia are needed.Therefore,the research of ammonia gas detection sensor is of great significance and value.In order to meet the needs of human wearable devices for real-time detection of possible ammonia environment,such as industrial refrigeration,biomedical and other applications,this paper mainly studies the flexible ammonia sensor based on ZnO nanomaterials.The main work of this paper is as follows:(1)ZnO nanorods were prepared by hydrothermal method,and the low temperature gas sensing properties of commercial ZnO and ZnO nanorods were compared.The material properties,gas sensing and gas sensing mechanism of ZnO nanorods were tested and analyzed.The results show that the response value of ZnO nanorods rises to peak value first and then decreases gradually in the temperature range of 180-340 ?.The maximum value appears at260 ?,and the maximum sensitivity is 7.75.The results show that ZnO nanorods have better gas sensing properties for ammonia than commercial ZnO.Changing the ZnO morphology is an effective way to reduce the working temperature and improve the sensitivity of the sensor,which can reduce the power consumption of the sensor and make it have better detection accuracy.(2)The orthogonal experiment was used to design the experiment.Taking hydrothermal reaction time,hydrothermal reaction temperature and the molar ratio of zinc oxide to thiourea as three important variables in the orthogonal experiment,nine groups of representative ZnO ZnS samples with different process combinations were prepared by hydrothermal method.The structure and morphology of nine samples were characterized by XRD,SEM and EDS.two better preparation methods of ZnO-ZnS were selected.The gas sensing characteristics of two kinds of ZnO-ZnS and pure ZnO sensor samples were tested by static gas distribution method and compared.The results show that the high performance ZnO-ZnS nanomaterials show good sensitivity to ammonia gas,the sensitivity to 100 ppm ammonia gas at 300 ? is66.55,the response and recovery time is about 15 seconds,and they show good selectivity and stability to ammonia and acetone,The sensor with low power consumption can be fabricated.It provides a reference for the preparation of high-performance flexible ammonia sensor in the future.(3)ZnO-ZnS flexible ammonia sensor was prepared by screen printing and drop coating.The effects of film thickness,electrode spacing and other process parameters on its gas sensing characteristics were studied.The results show that the flexible ammonia sensor with narrow electrode spacing printed by screen printing has lower working temperature and higher sensitivity.When the film thickness reaches 0.09 mm,the sensitivity of the sensor is the highest,which reaches 62.07 at the concentration of 100 ppm ammonia,and shows good repeatability and selectivity at a certain concentration of ammonia.By testing the bending cycle characteristics of the flexible ammonia sensor,it is verified that the flexible ammonia sensor still maintains good gas sensing response and stability of initial resistance after multiple bending,showing good flexibility and bending resistance. |
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