Graphene And Its Derivatives Based Chemical Biosensors

People are paying more and more attention to health and safety with the development of society,which has made extensive research on sensors with advantages including light,portable,easily performed,and real-time detection.Graphene and its derivatives prepared on the basis of graphite oxide(GO)show a series of advantages,which provide a favorable foundation for the research of chemical biosensors.Therefore,it is necessary to explore the application of graphene and its derivatives in the field of chemical biosensors.This thesis focuses on the application of reduced graphene oxide(RGO)with different degrees of reduction and RGO composites in the field of chemical biosensors.The main contents are as follows:(1)Preparation,characterization and performance research of all-covalently-implanted RGO field effect transistors.The GO solution was prepared by the modified Hummers oxidation method.The covalent layer-by-layer(LBL)self-assembly of GO LBL films are used(3-aminopropyl)trimethoxysilane as covalent cross-linkages,which has controlled number of layers and a uniform density.RGO films with different degrees of reduction were obtained by controlling the conditions of thermal annealing.According to the difference in performance,the RGO with higher degree of reduction was used as the source/drain electrodes,and the lower one was used as the semiconductor layer.The device exhibits perfect ambipolar field-effect characteristics of an extremely sharp Dirac point.The average value of hole and electron mobility reaches 0.33 and 0.37 cm² V^-1 s^-1.The on-off ratio average value is 3000.Since the electrodes and semiconductor layer of the device are connected by covalent bonds,the device exhibits outstanding electrical stability and ultrahigh solvent resistibility.(2)Construction,characterization and diagnosis uses of all-covalently-implanted RGO field effect transistor immunosensors.The prepared all-covalently-implanted field effect transistor is used as an effective carrier for the immunosensor,and it is used for a label-free diagnosis of liver cancer biomarker,?-fetoprotein.Using 1-pyrenebutanoic acid succinimidyl ester as a cross-linker to immobilize sensitive probe molecules on the sensing area effectively,and using ethanolamine or bovine serum albumin as a blocking reagent to cap the excess sites of sensing area.It was found that the immunosensor constructed by these methods can effectively detect the targets with outstanding selectivity,sensitivity and stability.This work has guiding significance for the diagnosis of biomarkers and the design of stable sensors.(3)Construction,characterization and detection of cyclodextrin functionalized RGO for electrochemical chiral differentiation.GO was reduced with hydrazine hydrate to afford RGO,where?-,?-,and?-cyclodextrin(CD)were added in the reduction process affording the desired RGO-CD composites.RGO-CDs modified electrochemical sensors were fabricated by coating the RGO-CDs on electrode with methylene blue(MB)as the indicator and applied for the enantiorecognition of model racemic analytes.This work mainly takes the enantiomeric detection of tartaric acid(TA)as an example proves that RGO-?-CD-MB has greater advantages as an electrode modification material.The prepared electrochemical sensor can be used for qualitative and quantitative analysis of TA.