Preparation Of Graphene-based Nanocomposites And Their Biosensing Applications

Graphene,a kind of two-dimensional carbon materials with high specific surface area,good biocompatibility,excellent electrical conductivity,high chemical and thermal stability.In recent years,graphene has been widely used for the applications in photocatalysis,biosensors and biomedical domain.In this thesis,graphene was prepared and combined separptately with hemin?bovine serum albumin?BSA??poly?3,4-ethylenedioxythiophene??PEDOT??Pt-Pd bimetal nanoparticles?Pt-Pd NPs??carboxylated single-walled carbon nanotube?CNTs-COOH?and so on to establish three sensing and detection platforms for the efficient analysis of small molecule metabolites,H₂O₂ and carcinoembryonic antigen?CEA?,respectively.The contents of the thesis mainly include:?1?A kind of PEI-rGO-Hemin-BSA nanocomposites were synthesized,and nanocomposites showed an excellent peroxidase-like activity.Importantly,through the glutaradelhyde crosslinking,PEI-rGO-Hemin-BSA could be further simply combined with various oxidases such as glucose oxidase?GO_x?,cholesterol oxidase?CO_x?,lactate oxidase?LO_x?and choline oxidase?ChO_x?to preparate PEI-rGO-Hemin-BSA-GO_x,PEI-r GO-Hemin-BSA-CO_x,PEI-rGO-Hemin-BSA-LO_x and PEI-rGO-Hemin-BSA-ChO_x for the detection and quantitative measurement of multiple metabolites including glucose,cholesterol,lactate and choline.?2?A colorimetric method has been developed using Hemin-rGO-CNTs-COOH-Pd-Pt peroxidase mimetic for the detection and quantitative measurement of H₂O₂.The linear response of the absorbance versus the H₂O₂ concentration 0.05-500?M with a detection limit of 0.01?M.Of note,combined with layer-by-layer electrostatic assembly technique,cost-effective test strips were designed for convenient H₂O₂ detection.Both enzyme?Hemin-rGO-CNTs-COOH-Pd-Pt nanocomposite?and TMB have been immobilized on different layers of the modified paper,using the formation of a“functional wafer-like”layered film of PAH/PSS polyelectrolytes system coating.Based on these facts,the test strip was successfully applied to detect H₂O₂ in real tap water,milk and contact lens solution samples with satisfactory results.?3?We successfully fabricated a metal@protein nanoflower of CNTs-COOH/rGO/Ag@BSA and the conducting polymer was adsorbed onto the obtained CNTs-COOH/r GO/Ag@BSA to form CNTs-COOH/rGO/Ag@BSA/PEDOT with distinguished electrochemical activity,good biocompatibility,high electric conductivity and high specific surface area.The as-prepared nanocomposites were then deposited onto an Au electrode together with subsequent immobilization of CEA antibody?anti-CEA?and BSA to construct the electrochemical immunosensor?Au/CNTs-COOH/rGO/Ag@BSA/PEDOT/anti-CEA/BSA?.The immunosensor offers a linear relationship between the electrochemical responses and the CEA concentrations from 0.002-50 ng/m L with a detection limit of 1×10^-4 ng/m L.Therefore,this simple and sensitive strategy might find a valuable application in clinical analysis and diagnosis.