Plasma Surface Modification Of Graphene And Its Application In FET Sensor

Deoxyribonucleic acid(DNA)is the main carrier of biological genetic information,it can be used to predict and diagnose diseases due to the life information and the genetic factors at the molecular level detection.With the coming of the era of precision medicine,micro-biosensors based on molecular diagnostics have gradually become a research hotspot.Two-dimensional material field-effect transistor(FET)biosensor is one of them.It has the advantages of high sensitivity,good specificity,simple operation,label-free,and low cost.Graphene,the representative two-dimensional material,is widely used in FET biosensors due to its large specific surface area and super high carrier mobility.The goals of researchers are been to improve the sensitivity,specificity of sensors and reduce detection costs.The development of plasma technology provides an effective way for surface modification of sensing materials.Atmospheric pressure plasma with room temperature is used for graphene treatment,which has the characteristics of simplicity,efficiency,flexibility,environmental protection and low cost.The purpose of this thesis is to achieve graphene field effect transistor(FET)biosensor with high sensitivity,high specificity and low cost.Plasma jet installation is assembled and used for the surface modification of graphene and the preparation of DNA-FET sensor.Plasma jet installation with a pulse-modulated radio frequency(RF),atmospheric pressure,low-power and room temperature was assembled and used to modify the surface graphene.Argon plasma was chosen here for the surface modification of graphene: 1)Scanning electron microscope(SEM)and atomic force microscope(AFM)were used to analyze the surface morphology of graphene.2)X-ray photoelectron spectroscopy(XPS),Raman spectroscopy(Raman),and ultraviolet-visible light spectroscopy(UV-Vis)were used to characterize the effect of plasma treatment of graphene with the different time,and it was concluded that 30 s was the optimal time for treatment graphene.3)The wettability of graphene was analyzed with a contact angle tester.Since the hydrophilic functional group was formed after plasma treatment,it was more hydrophilic and conducive to the detection of organisms.4)The conductivity of the surface modification of graphene and the fluctuation of current with voltage were tested,showing that the conductivity of the graphene treatment by plasma was better.5)Based on the theory of the energy analysis model diagram,the energy changes in the process of plasma treatment of graphene were analyzed.This energy analysis explained the cleaning effect of plasma on graphene.DNA-FET sensor based on the surface modification of graphene was fabricated and the characteristics were analyzed.1)1-pyrenebutyric acid-succinimide resin(PBASE)was used to functionalize graphene and further bind DNA on the graphene surface.Raman test was used to analyze the binding effect of DNA,PBASE and graphene surface.2)The transfer characteristic curve was tested with a Keithley 4200-SCS semiconductor parameter analyzer.It was found that the graphene Dirac point after surface modification was shifted more significantly to the negative gate voltage.The sensor was changed from p-type to n-type.3)The affinity between the probe DNA and the target DNA was analyzed and become better than that of the untreated graphene.4)The sensitivity of surface-modified graphene was higher than that of the original graphene,and the detection limit(LOD)reached 10 a M,which was an order of magnitude higher than that reported by previous researchers.5)Single-stranded DNA was used as the specific aptamer for DNA detection and specific recognition.The probe DNA,binded to three mismatched base DNAs and the completely mismatched base DNAs,were all recognized.