| Graphene,as a new type of carbon nanomaterial, has been widely used in the preparation of the biosensor due to its good electrical conductivity, large specific surface area, strong electrocatalytic property and good biocompatibility. Meanwhile, metal nanoparticles possess unique properies such as large specific surface area, high surface energy, and good catalytic activity, so it can replace the enzyme to build nonenzyme biosensor. The synergistic effect of both can improve the performance of the sensor and effectively promote the development of electrochemical sensor. This dissertation focused on the studies of the sensors based on graphene or graphene-metal nanoparticle composites modified electrodes, and realized the detection of hydrogen peroxide（H2O2） and β-nicotinamide adenine dinucleotide（NADH）. The main contents were summarized as follows:1、A kind of water-dispersible Pt nanoparticle-reduced graphene oxide hybrid material（Pt-PDDA-rGO） has been prepared by in situ reduction of both graphene oxide（GO） and the Pt（Ⅳ） precursor in acidic solution using metallic Zn powder, and poly（diallyldimethylammonium chloride）（PDDA） is used as a dispersing agent and stabilizer. And then build a nonenzyme sensor based on the hybrid material modified glassy carbon electrode to detect H2O2. The H2O2 can be effectively detected by the sensor because graphene provided large amounts of anchoring sites for achieving a high dispersion of small size PtNPs, which will lead to higher catalytic ability for H2O2. The experimental results demonstrated that the constructed sensor exhibited excellent catalytic activity toward H2O2, and obtained a wide linear range from 1.0×10-9 to 1.4×10-3mol/L with a low limit of detection（LOD） of 3.4×10-10 mol/L, and the selectivity and reproducibility is good. Moreover, it can also be used for the real sample analysis, and the electrocatalytic mechanism of the constructed sensor was briefly discussed.2、Based on the research of the above chapter, we constructed an simple electrochemical sensor for highly sensitive sensing of NADH using PDDA functionalized reduced graphene oxide nanocomposite modified glassy carbon electrode（PDDA-rGO/GCE）. The experimental results demonstrated that the constructed sensor exhibited excellent electrocatalytic activity on the oxidation of NADH with a decreased about 200 mV in peak potential and 5.0-fold increment in the peak current compared to a bare GCE, which was mainly ascribed to the large specific surface, fast electron transfer character of PDDA-rGO and its strong adsorption effect on NADH. Furthermore, a wide linear range from 1.0×10-7 to 2.9×10-3 mol/L with low limit of detection（LOD） of 3.4×10-8 mol/L（S/N of 3） was obtained, and the electrocatalytic oxidation mechanism of NADH at the PDDA-rGO/GCE was also discussed.3、In this chapter, the thiol functional graphene-AuNPs composites（CTAB-G-S-Au） was synthed successfully by wet chemical methods. First, cetyl trimethyl ammonium bromide（CTAB） was used to non-covalent functionalize graphene oxide to improve dispersibility, and then hydrobromic acid was applied to achieve simultaneous reduction and bromination effects on graphene oxide. Subsequent addition of thiourea followed by hydrolysis with sodium hydroxide gave thiol-functionalized graphene（CTAB-G-SH）. As a result, hydroxyl and epoxide groups of GO were targeted for thiolation. Then, AuNPs were covalently immobilized onto graphene using S-Au bond to gain the final product CTAB-G-S-Au. Finally, the composite was modified on the electrode and build a new type electrochemical sensor to detect NADH. The experimental results show that the sensor showed high electric catalytic activity and lower detection limit on the oxidation of NADH, indicating that the modified materials can be used for biological sensing applications. |
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