| Electrochemiluminescence(ECL) is a kind of chemiluminescence produced by electrochemical reaction. Because it does not need external excitated light source and has the features of low background signal, wide linear range and simple equipment, it has now become a kind of widely used testing method with high sensitivity and selectivity. Electrochemiluminescence immunosensor could combine the advantages of chemiluminescence technology and immune technology. The study on how to enhance the immune signal and how to immobilize antibody and antigen on the surface of sensors has always been an important field of immune analysis. In recent years, the new nanomaterials, signal enhancement technique and protein immobilization technology were used in the study of electrochemical immunosensor for the detection of tumor markers. The combination of nanotechnology and immunoassay provided a new thought for the development of immunoassay, especially unique properties of nanocomposites which play a very important role in the development of sensors with high sensitivity.In recent years, a new type of carbon nanomaterials such as carbon nanotubes(CNTs) and graphene(G), carbon quantum dots(CQDs) were widely used in many fields due to their unique properties. Graphene with the outstanding advantages of large specific surface area, high mechanical strength, high chemical stability and thermal conductivity is widely used in the field of energy storage and conversion, catalysis, medicine, biological sensors and so on. Carbon quantum dots with the features of stable chemical composition, low toxicity, luminous excellent performance, low cost of preparation and biological compatibility etc. has a good application prospect in the field of biological imaging, photoelectric catalysis, oxygen reduction, drug identification and other fields.Our works mainly targeted at the synthesis, functionalization of carbon quantum dots and carbon quantum dots and the application in electrochemical biosensors and the following research work was carried out : 1. The preparation and characterization of carbon quantum dots and functionalized carbon quantum dots with hetero atomsIn this work, carbon quantum dots(CQDs) and functionalized carbon quantum dots were successfully synthesized. The transmission electron microscope(TEM) images were used to characterize their appearance shapes and ultraviolet absorption spectrum, fluorescence spectrum and ECL were used to study their optical behaviors and electrochemical luminescence behavior. According to the results, the as-prepared CQDs and functionalized carbon quantum dots with hetero atoms possessed the features of uniform particles, controllable light resistance, and stable electrochemical luminescence signals. In addition, gold nanoparticles(AuNPs) was successfully prepared by the redox reaction between CQDs and HAuCl4. Here, AuNPs has structure of polyhedron which is different from that prepared by the traditional method. 2. A novel sandwiched electrochemiluminescence immunosensor for the detection of arcinoembryonic antigen based on carbon quantum dotsIn this study, a novel sandwiched electrochemiluminescence(ECL) immunosensor for the detection of carcinoembryonic antigen(CEA) was developed. The nanocomposite of polydopamine and Ag nanoparticles(PDA-AgNPs) was prepared by the redox reaction between Ag+ and dopamine. This nanocomposite not only provided an effective matrix for the immobilization of primary antibody( Ab1) but also enhanced the conductivity of the electrode. Carbon quantum dots(CQDs) were immobilized on the poly(ethylenimine) functionalized graphene oxide(PEI-GO) through amido bond. Then Au nanoparticles were decorated on the CQDs modified PEI-GO matrix, which was used to link secondary antibody(Ab2). The CQDs can be connected to the electrode surface through the combination of CEA with Ab1 and Ab2, and then the electrochemiluminescence of CQDs was obtained. Under the optimal conditions, the ECL intensity was proportional to the logarithm value of CEA concentration with a good linear range from 5 pg mL-1 to 500 ng mL-1 and a detection limit of 1.67 pg mL-1 for CEA detection. The immunosensor was applied for the CEA detection in real samples with satisfactory results. The proposed ECL immnuosensor showed good performance with high sensitivity, specificity, reproducibility, stability and will be potential in clinical detection. 3. A novel electrochemiluminescence(ECL) sensor based on the coreaction between CQDs and Ru(bpy)32+ for the detection of bisphenol A(BPA)In this study, a novel electrochemiluminescence(ECL) sensor based on the coreaction between CQDs and Ru(bpy)32+ for the detection of bisphenol A(BPA) was developed. Firstly, CQDs was immobilized on the polypyrrole functionalized graphene oxide(PPy-GO), and then the compound of PPy-GO-CQDs was immobilized onto the electrode surface. PPy-GO was not only able to load a large number of CQDs but also can accelerate the electron transfer between the electrode and solution, thus the sensitivity was improved. Then the modified electrode worked in the solution containing Ru(bpy)32+. Based on the ECL quenching effect of BPA on luminescence system of Ru(bpy)32+/CQDs, the concentration of BPA was detected. Under the optimized conditions, the proposed electrochemiluminescence immunosensor showed a linear range from 5 nmol·mL-1 to 1000 nmol·mL-1 with the detection limit of 2 nmol mL-1(S/N=3). In addition, the proposed immunosensor exhibited good stability and reproducibility and wide linear range. 4. Highly sensitive and selective detection of carcinoembryonic antigen based on carbon quantum dots as co-reactants of Ru(bpy)32+ ECLIn this study, a novel sandwiched electrochemiluminescence(ECL) immunosensor for the detection of carcinoembryonic antigen(CEA) based on the coreaction between carbon quantum dots and Ru(bpy)32+ was developed. Carbon quantum dots(CQDs) were assembled onto the surface of the poly(ethylenimine) functionalized graphene oxide(PEI-GO) and the complex of PEI-GO-CQDs was used to immobilize primary antibody(Ab1). Mesoporous silicon(MSN) was utilized to load Ru(bpy)32+ which served as chemiluminescence signal and Au nanoparticles were introduced to accelerate the electron transport and then to amplify the ECL signals. At the same time, the functionalized MSN was employed to label secondary antibody(Ab2). In this work, CQDs acted as the co-reactants of the anodic electrochemiluminescence of Ru(bpy)32+. Under the optimized conditions, the proposed electrochemiluminescence immunosensor showed a linear response to CEA in the range of 1 pg·mL-1 to 1000 ng·mL-1 with a detection limit of 0.33 pg mL-1(S/N=3). In addition, the proposed immunosensor exhibited good selectivity, acceptable stability and reproducibility. |
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