Research On QCM-based Graphene Film Humidity Detection System And Its Sensing Properties

As a physical quantity,relative humidity has an important influence in many fields,healthy life and safe social production are inseparable from the humidity measurement,high-performance humidity sensor has always been the focus of scientific research.QCM sensor is a new kind of mass-sensitive device,it uses quartz crystal as a conversion element and changes QCM surface quality into frequency signal output,it has many advantages,such as high sensitivity,real-time digital frequency output,good stability,low cost etc.At present,the application of QCM in the field of humidity detection has become the focus of scholars.In order to realize the research on graphene film humidity detection system and sensing properties based on QCM,this paper mainly carried out the following research work:Investigated the basic theory of quartz crystal and compared a variety of common QCM signal detection methods.Taking into account all kinds of factors,determined to use ordinary oscillator circuit as QCM drive circuit.Temperature,pressure,and self-aging can cause QCM have frequency drift,adopt the difference-frequency circuit to reduce the influence of these factors.Fourth order Butterworth lowpass filter circuit was designed to reduce the interference of high harmonics to the QCM output frequency interference.At the same time to complete the design of hardware circuit,design the next crew and upper computer program based on STM32 and LabVIEW,finally completed the design of QCM signal detection platform.Based on the humidity sensitive characteristics of GO,PANI/GO,PDDA/GO and PANI/SnO₂/GO film QCM humidity sensors were prepared by electrostatic self-assembly technology and in-situ polymerization method to realize the effective modification of polymer and metal oxide to GO.XRD,SEM,FT-IR and other characterization techniques were used to analyze the surface morphology and microstructure of the humidity sensitive film.The QCM signal detection platform was used to test the dynamic switching response,response/recovery time,repeatability,stability and selectivity of QCM sensors.The impedance characteristics of QCM sensor were investigated by impedance analyzer.The sensitive response mechanism of the composite film to humidity is revealed based on the physical and chemical properties of sensitive materials,the modification of polymer and metal oxides,the molecular adsorption kinetics model.This subject designed the QCM signal detection system and explored the humidity sensitive characteristics of the fabricated nanoparticle modified GO film QCM sensor.The QCM humidity sensor with high sensitivity was developed,which provided an important theoretical guidance and engineering reference for the development of humidity sensing device.This has an important reference value for accurate and rapid detection of humidity.