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Fabrication Of Graphene-based Film Sensor And Its Humidity Sensing Properties

Posted on:2015-02-28Degree:MasterType:Thesis
Country:ChinaCandidate:J TongFull Text:PDF
GTID:2308330503975026Subject:Control Science and Engineering
Abstract/Summary:PDF Full Text Request
Humidity detection plays a very important role in various fields of atmospheric monitoring, industrial production and biomaterials and medical devices. It is indicated that graphene is one of ideal materials for gas and humidity sensor due to its excellent electrical, thermal, and mechanical properties such as metallic conductivity, large surface-to-volume ratio, high adsorption capacity. Graphene and its derivative, such as graphene oxide(GO) and reduced graphenen oxide(RGO), open up a new way to develop new humidity sensors. In order to relize a highly sensitive and rapid responding humidity sensor, in this thesis, GO-based and RGO-based films are deposited onto self-designed elctrodes via researching the film fabrication methods, and their humidity sensing properties are investigated and discussed.Two kinds metal interdigitate electrode are designed and fabricated, one is hard-board device with PCB as substrate and the other is flexible device with polyimide PI as substrate. Graphene and its composite membranes are prepared based on drop-casting method, static induced layer-by-layer(LbL) self-assembly method and hydrobromic acid reducing method, and by using SEM and XRD analysis, the surface morphology and microstructure of the nano films are observed. In this paper, humidity sensors are fabricated based on three kinds of films, including drop-casting RGO film, resistance-type PDDA/RGO film and capacitance-type PDDA/GO film. Saturated salt solution method is adopted to establish the humidity testing environment, the humidity sensing properties of the film sensors are investigated at room temperature, consisting of sensitivity, response-recovery features, hysteresis, stability and continuous switching characteristics. The testing results reveal the sensitive relationship between electrical characteristics of the film senors and the external humidity level, and the humidity sensing mechanism is also discussed deeply. Research shows that the hysteresis of the dorp-casting RGO film sensor is very large in high humidity range, thus not suitable for high humidity detection. The Lb L resistance-type PDDA/RGO film sensor efficiently and nondestructively reduced by hydrobromic acid has good humidity sensing performance as well as small hysteresis, applicable for humidity measurement over a wide humidity range. The capacitance-type PDDA/GO film humidity sensor has ultrahigh sensitivity(265640%) and faster response-recovery time, its humidity sensing performance is significantly superior to the current existing humidity sensors, and it is successfully applied to the detection of respiration rate. By analyzing the complex impedance plots and bode diagrams of the PDDA/GO film humidity sensor, a general equivalent circuit model is proposed by Zview software simulation.
Keywords/Search Tags:Graphene oxide, reduced graphene oxide, humidity sensing properties, layer-by-layer, film sensor
PDF Full Text Request
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