Study Of Acetone Gas Sensor And Room Temperature Humidity Sensor Based On Nickel Oxide P-n Heterojunction

As a tool for human beings to understand and perceive nature,sensor technology has become the most popular research field,which has a very broad application value and commercial significance.Among them,the gas sensor and humidity sensor as the most basic two kinds of sensors have been studied by scientists.They are widely used in daily life and industrial production:for example,the detection of toxic and harmful,flammable and explosive gases,the monitoring of gas and humidity atmosphere in the production environment,and the monitoring of indoor environment are inseparable from gas and humidity sensors.Therefore,the research and development of low-cost,high sensitivity,high stability and high-performance gas sensors and humidity sensors has been a hot topic in the sensor field.In recent years,high sensitivity acetone gas sensor has been widely concerned and developed.Acetone,as a common volatile organic compound,has its emission sources in natural environment and human activities,such as biological emissions,automobile exhaust,solvent utilization and industrial emissions.When acetone gas is mixed with air,it will easily burn and explode in case of open fire and high temperature,which will cause serious safety problems.In addition,acetone is also irritant,which will cause serious adverse effects on human health and may lead to life danger.Some studies have shown that there is a certain concentration of acetone in the exhaled gas of human beings,and the concentration of acetone in the exhaled gas of healthy people and diabetic patients is different,so acetone can be used as a biomarker to detect diabetes.Obviously,the detection of acetone gas has become a new research hotspot.Humidity is an important feature of the environment.Accurate measurement,continuous monitoring and real-time control of humidity play an important role in many fields such as meteorology,agriculture and electronic equipment storage.For example,in order to obtain an ideal surrounding environment,it is necessary to monitor,detect and control the environmental humidity through precise sensors under different conditions of low temperature,high temperature or mixing with other gases.Combining intelligent system and network,using humidity sensor to monitor soil moisture during agricultural irrigation,or to diagnose corrosion and erosion in infrastructure and civil engineering,is also one of the important applications of humidity sensor.In fact,in order to meet the needs of people for high-performance acetone gas sensor and humidity sensor,scientists have carried out a lot of research on them based on a variety of organic,inorganic or hybrid materials,using physical and chemical preparation methods.Inorganic metal oxide semiconductors and their composites have been proved to be ideal sensing materials in the field of sensing.Nickel oxide?NiO?,as a typical wide band gap p-type transition metal oxide semiconductor material,has good sensing performance.Although compared with most n-type metal oxide semiconductors,its performance still needs to be further improved,however,NiO has many significant advantages,such as high thermal mechanical stability and catalytic activation performance,which is still a gas sensitive and humidity sensitive material with great research value sensitive material.In this paper,p-type wide-band gap semiconductor NiO two-dimensional nano chip self-assembled hierarchical flower microspheres are studied.By adding other n-type metal oxide semiconductors,the composite with p-n heterostructure is prepared,and the micro morphology of the composite is controlled to improve the sensing performance of the material.Specific research contents include:?1?NiO-CeO composite with different ratio?0.5 mol%,1 mol%,2 mol%,3 mol%?was synthesized by hydrothermal method with CeCl₃·7H₂O and NiCl₂·6H₂O as Ce source and Ni source respectively.The response of NiO-CeO composite to acetone has good stability.The recovery time needs to be further shortened to improve its practicability.?2?Using Zn?NO₃?₂·6H₂O as zinc source and Ni?NO₃?₂·6H₂O as nickel source,the layered flower like structure NiO-ZnO Composite with different ratio was synthesized by hydrothermal synthesis method,and characterized systematically.A gas sensor based on NiO-ZnO composite was prepared and tested for its sensitivity to acetone.The experimental results show that the response time of NiO-ZnO Composite to acetone is only 15 s under the condition of 50 ppm acetone,and the response value increases linearly with the increase of acetone concentration.?3?In this chapter,the humidity sensitive properties of NiO-CeO materials at room temperature were studied.At room temperature,the response recovery,frequency characteristics and humidity hysteresis effect of the material in the range of 11%-95%RH were measured,and its humidity sensitive mechanism was analyzed by complex impedance test.The experimental results show that NiO-CeO has a rapid response to humidity?30 s?,good stability?the response is stable during the cycle test?,and has the potential to prepare high-performance humidity sensor.