Research On High Sensitivity Surface Acoustic Wave Hydrogen Sensors Based On Graphene Composite Sensitive Layers

Surface acoustic wave(SAW)gas sensors are widely used in various fields and they exhibit great potential in application in future.In this paper,a SAW hydrogen sensor using a graphene-based sensitive layer is studied.A redox graphene(RGO)sensitive layer is deposited on the surface of a LiNbO₃ piezoelectirc substrate and a platinum film is grown on the RGO layer as a catalyzer.This SAW hydrogen sensor has a high sensitivity and can be available for detection of hydrogen with a trace concentration.This paper is divided in five parts:Chapter One: The overview of SAW sensors and the properties of graphene are introduced.The advantages of graphene as a hydrogen-sensitive material and the application prospects in SAW hydrogen sensors are presented.Chapter 2: The technique to create a SAW hydrogen sensor using a graphene-based sensitive layer is studied.Improved Hummers method is adopted to produce graphene oxide,and RGO is obtained using hydrothermal rduction method.Pt is grown with magnetron sputtering method,which works as a catelyzer.Meanwhile,characterization methods,as scanning electron microscopy(SEM),Fourier infraced spectrum(FTIR),and so on are used to evaluate the sensitive layer.Chapter 3: The response to hydrogen and the sensing mechanism of the sensor are studied.Experiments show that the sensor has an extremely high sensitivity,which can be used to detect hydrogen with a trace concentration.The influences of the backgournd gases,humidity and holing periods on the performance of the sensor are evaluated.Furthermore,the sensing mechanism is discussed,which is used to analyze the experimental results.It is observed that the variation of the surface conductivity exert an important impact on the sensitivity.Chapter Four: Doping modification of the RGO sensitive layer is studied.Accoring to Zeta potential,two types of dispersants,a cationic dispersant and a nonionic dispersant is used in the experiments.Then,the RGO sensitive layers modified by different dispersants are obtianed.Finally,the influence of the doping on the hydrogen sensing is studied,which exhibits that doping can improve the performance in both response and recovery stages.Chapter Five: A summary to the paper and a prospect to the work in the future.