Preparation And Application Of Nitrogen-doped Carbon-based Nanocomposites In Electrochemical Luminescence

This thesis mainly studies the application of nitrogen-doped carbon-based nanomaterials in Luminol electrochemical luminescence technology.Electrochemical luminescence technology has a wide range of applications in biomolecular detection,immunoanalysis and other fields because of its high sensitivity,low background signal,convenient operation and other advantages.Luminol,as one of the commonly used luminescent bodies with high luminous efficiency,can not only generate luminol anode ECL signal,but also generate luminol cathode ECL signal at lower potential,which is more beneficial to prevent the damage of high potential on the electrode surface and detection molecules.In recent years,carbon-based nanomaterials such as carbon nanotubes and graphene have been widely used in electrocatalysis,sensors and other fields as catalytic materials comparable to metal Pt due to their high specific surface area and excellent electrical conductivity.With the development of research,in order to generate new properties and structures of carbon-based materials,doping heteroatoms into carbon-based nanomaterials has become a hot topic.In this paper,the application of nitrogen-doped carbon-based nanomaterials in luminol cathodic luminescence system is studied.It is found that the prepared materials can produce excellent ECL signals at low potential under neutral and weak alkaline conditions.Then,the catalytic mechanism of N-doped carbon-based nanomaterials was further explored and three different types of electrochemical luminescence(ECL)biosensors were constructed to explore their application in actual sample detection.The main research contents are as follows:(1)Preparation of carbonized polydopamine nanosheets and its application in Luminol electrochemiluminescenceUsing the Helolite nanotubes(HNTs)as the template,polydopamine(PDA)film was formed on the surface of Helolite nanotubes(HNTs)by self-polymerization of dopamine under alkaline conditions.After HNTs template removal and carbonization of PDA nanotubes at high temperature,nitrogen-doped carbonized dopamine nanotubes(C-PDANTs)were obtained.The electrochemical test showed that the prepared C-PDANTs had a significant catalytic effect on the electrochemical reduction of dissolved O2 or H2O2.The initial potential of electrochemical reduction of H2O2 was increased to positive potential,which promoted the generation of cathode electrochemical luminescence of Luminol/H2O2 system under positive potential,and effectively avoided the interference of dissolved O2.Finally,a novel cholesterol electrochemiluminescence sensor was prepared based on C-PDANTs/cholesterol oxidase(ChOx)modified electrode and Luminol/H2O2 system at positive potential cathode electrochemiluminescence.Cholesterol was oxidized by enzyme to produce H2O2.The content of H2O2 was measured by this sensor,and cholesterol was indirectly measured.The linear range of cholesterol detection is 8.0×10-6～1.2×10-3 M,and the detection limit is 4.2×10-6 M.It can be used for the detection of cholesterol content in human serum.(2)Preparation of carbon graphite phase carbon nitride-polypyrrole nanocomposites and its application in Luminol electrochemical luminescenceUsing g-C3N4 as sacrificial template and nitrogen source,polypyrrole(PPy)was loaded onto P-g-C3N4.By high temperature carbonization,graphite carbide phase carbon nitrous hybrid polypyrrole(C-PCN@PPy)nanomaterial was obtained.The morphology,structure and nitrogen content of the materials before and after carbonization were investigated by TEM,XPS and Raman characterization systems.C-PCN@PPy nanomaterials promote the generation of electrochemical luminescence in luminol/O2 system,and the electrochemical luminescence of the system at anode potential and cathode potential is significantly enhanced,which verifies the catalytic effect of C-PCN@PPy nanomaterials on the electrochemical oxidation of luminol and electrochemical reduction of dissolved oxygen.Therefore,based on the electrochemical luminescence of C-PCN@PPy cathode in Luminol/O2 system,the electrochemical luminescence signal was reduced by utilizing the ability of antioxidants to scour oxygen free radicals.Trolox solution was used as the index of total antioxidant capacity to construct an electrochemical luminescence sensor for detecting the total antioxidant capacity of solution.The detection linear range of the sensor is 5.0×10-5～7.0×10-4 M,and the detection limit is 2.4×10-5 M.Compared with the results of commercial ABTS standard kit,The relative error ranges from 0.38 to 14.1%.(3)Preparation of carbonized polyethyleneimide nanosheets and its application in Luminol electrochemical luminescencePolyethyleneimide(PEI)polymer was used as nitrogen source,montmorillonite(MMT)was used as template,electrostatic adsorption was used to obtain PEI supported MMT composite material,high temperature carbonization and acid-base etching to remove the template,to obtain carbonized Polyethyleneimide(C-PEI).C-PEI modified electrode can enable Luminol to generate electrochemical cathode luminescence at a lower position.The catalytic performance of C-PEI was investigated by electrochemical test,and it was found that C-PEI nanomaterial can catalyze the generation of oxygen reduction reaction and accelerate the generation of ROS.Therefore,based on the scavenging effect of glutathione on oxygen free radicals,an electrochemiluminescence biosensor based on C-PEI nanomaterials and Luminol/O2 system cathodic electrochemiluminescence was prepared for the determination of glutathione content in human serum.The detection linear range of glutathione(GSH)was 1.0×10-5～2.5×10-3 M.The detection limit is 9.9×10-6 M.