Novel Humidity Sensor Based On Graphene Derivatives And Graphene Like Materials

Humidity monitoring is an important component of the environmental aspects,which was concerned with perception layer of internet of things in healthcare.With the continuous development of internet of things in recent years,many applications put forward higher requirements of humidity monitoring.The humidity sensors with high humidity sensitivity are required to control the environment humidity at low levels in many applications,such as IC industry,chemical transportation and agricultural storage.Fast response humidity sensors can meet the requirement for rapid humidity measurements,such as that in apnea monitors,lung disease surveillance,management of anesthesia patients,and atmospheric monitoring.Therefore,more research is needed on the humidity sensors with high-performance to meet the rising demand of humidity monitoring.Till now,novel nanostructure materials have frequently been adopted in the application of humidity sensors,and gradually become the main choice for fabricating humidity sensors with high performance.This dissertation centres on and spreads out from the humidity sensing properties of graphene derivatives(GO,QD-GO)and graphene like materials(MoS2),which are novel two dimension nanomaterial.We present several types of humidity sensor with different properties based on these materials.The main content summarized as follows:1.GO modified with Ag nanoparticles based humidity sensor with high sensitivity is developed.Novel capacitive humidity sensors based on GO with different concentrations of Ag nanoparticles were prepared.The microstructure and hydrophilic properties,which was tested through TEM,XRD,FTIR and contact angle indicated that GO/Ag film process stronger adsorption performance than GO film.According to the experiment result test by LCR meter,compared with GO sensor and traditional(such as polymide)sensors,the sensitivity of GO/Ag humidity sensor was increased 2 and 3 orders of magnitude,respectively.Sensing films exhibited the Schottky behavior due to IV test result.With the improving of RH levels,the schottky barrier decreases simultaneously and consequently increases the conductance of sensing film.Complex impedance spectra(CIS)shows that Ag nanoparticles can strengthen the formation of liquid water layers and the charge conduction of sensing films.For above reasons,GO/Ag sensing films obtained excellent humidity sensitivity.2.QD-GO based humidity sensors with fast response speed is realized.Impedance humidity sensor were fabricated with QD-GO coated on IDE.The response and recovery characters of humidity sensors were studied by series resistance partial voltage methods.According to the experiment,the fabricated sensors got fast response speed in subsecond level and the thickness of sensing films is inversely proportional to the response time of humidity sensors.In combination with characterization of microstructure,a possible theory of intersection density was proposed to explain the rapid response behavior of humidity sensors.According to the experiment,this kind of sensors can accurately monitor the humidity variation near the nose in the respiratory cycle and further reflect human breathing behaviors.It is a new choice for non-contact measuring respiratory rates using humidity sensor.3.A preparation method of QD-GO based humidity sensors with ultrafast humidity response speed is presented.The bilayer composite sensing films was prepared via electrostatic self-assembled method with QD-GO and PDDA.According to the experiment,the fabricated humidity sensors got ultrafast response speed(millisecond level)and excellent water tolerance.These properties expands the application of humidity sensors.4.A humidity sensor with high sensitivity based on MoS2/Ag composite films is prepared.Novel capacitive humidity sensors based on MoS2 with different concentrations of Ag nanoparticles were prepared.Microstructure and humidity sensing properties of sensing films were studied.According to the experiment,compared with pure MoS2 sensors,the sensitivity of MoS2/Ag humidity sensor was increased 2 orders of magnitude.The surface morphology characterization and contact angle of sensing films indicated that MoS2/Ag film has stronger adsorption performance than MoS2 film.Complex impedance spectra(CIS)shows that Ag nanoparticles can strengthen the charge conduction of sensing films.For these reasons,MoS2/Ag sensing films obtained excellent humidity sensitivity.5.A preparation method of fast response humidity sensor based on MoS2 braced by SiO2 microsphere layer is presented.The SiO2 microsphere bracing layers and MoS2 humidity sensing layers was loaded on IDE in turn,and the humidity sensors were prepared.The microstructure characters of bilayers and the humidity sensing properties of fabricated humidity sensors was studied.According to the experiment,compared with MoS2 sensor,the response speed of humidity sensor based on MoS2 braced by SiO2 microsphere layer was doubled.In combination with the structural property of MoS2 and the convex characteristics of SiO2 braced sensing films,the fast response mechanism was discussed.The possibility of miniature drip infusion rate detection using humidity sensor was verified through water dripping rate monitoring experiment.