The Fabrication And Application Of Electrochemical Sensors Based On Graphene Nanomaterial

In recent years, the larger specific surface area, fast electron transfer rate and good biocompatibility of graphene, has make it an ideal material for fabricating electrochemical sensors. However, due to the strong van der Waals interactions and π-π stacking, graphene is hydrophobic and tends to form irreversible agglomerates, which limits the application of graphene. Therefore, some effective methods are needed to functionalize graphene to change its dispersibility. In this study, PVP-GR and PSS-GR was prepared through the non-covalent interactions between graphene and polymer, then was used as a material for modified electrode. By comprise a nanocomposite with quantum dots and gold nanoparticles, we bulit four electrochemical sensors, and explored their applications in real sample analysis. The results obtained provides a method study reference and basis for the synthesis of graphene-base nanocomposite and the construct of electrochemical sensors. This thesis mainly includes the following four aspects: 1. Determination of kaempferol based on PVP-GR-CdTe nanocomposite film modified glassy carbon electrodeIn this work, polyvinylpyrrolidone(PVP) was utilized through the non-covalent interaction between PVP and graphene, then mixed PVP-GR and CdTe quantum dots(CdTe QDs) as a ratio of 1:1 follow on ultrasonic 1h to obtain a novel nanocomposite PVP-GR-CdTe. Since the large specific surface area, ultrafast electron transfer rate and enrichment for kaempferol, PVP-GR-CdTe has excellent electrical catalysis. The as-prepared nanomaterial and modified electrodes were characterized by UV-vis, XRD, TEM and AC impendence, respectively. Cyclic voltammetry(CV) was used to investigate the electrochemical behaviors of kaempferol on PVP-GR-CdTe /GCE. Under the optimized experimental conditions, appling linear sweep voltammetry(LSV), a good linear relationship of the oxidation peak current and the concentrations of kaempferol in the range of 4.0×10-8~4.0×10-6 mol/L was achieved. The detection limit was 1.0×10-8 mol/L. The method was successfully applied for the determination of kaempferol in human plasma with satisfactory results. 2. Determination of daidzein based on PSS functionalized graphene film modified glassy carbon electrodeIn this section, poly(sodium 4-styrenesulfonate)(PSS) functionalized graphene(PSS-GR) was prepared via in situ reduction of GO in the presence of PSS. The as-prepared PSS-GR and modified electrodes were characterized by TEM, XRD, FT-IR and AC impendence, respectively. The nanocomposite exhibits excellent electrocatalytic activities towards the oxidation of daidzein. By using CV and LSV the electrochemical behavior of daidzein were studied, and the reaction mechanism was also explored. Under the optimal experimental conditions, the calibration curve of daidzein was established with a linear range of 2.0×10-8~2.0×10-6 mol/L, and the detection limit was 1.0×10-9 mol/L. 3. A sensitive electrochemical sensor based on PSS-GR-CTS nanocomposite for determination of dopamine in the presence of uric acidOn the basis of the previous chapter, a novel dopamine(DA) electrochemical sensor was fabricated based on PSS-Gr-chitosan composite film modified glassy carbon electrode. It was found that the composite exhibited excellent electrochemical activity towards the redox of DA. LSV was performed for the quantitative determination of DA in the presence of uric acid(UA). Under the optimum conditions, the oxidation peak current of DA was proportional to its concentration at the range of 6.0×10-9 mol/L to 8.0×10-6 mol/L with a detection limit of 1.0×10-9 mol/L. Besides, the electrochemical sensor can be also applied to detect UA under the condition of existence of DA, the range of linearity was from 2.0×10-7 mol/L to 1.0×10-4 mol/L and the detection limit was 4.0×10-8 mol/L. The proposed method was successfully applied for the determination of DA in human plasma with satisfactory recoveries. 4. A sensitive and selective electrochemical sensor based on graphene quantum dot/gold nanoparticle nanocomposite modified electrode for the determination of quercetin in biological samplesA simple and sensitive electrochemical sensor based on(graphene quantum dot)/(gold nanoparticle) nanocomposite(GQD/AuNP) modified glassy carbon electrode(GCE)(GQD/AuNP/GCE) was constructed and utilized for the determination of quercetin. The nanocomposite of GQDs and AuNPs not only can greatly accelerate the electron transfer rate and showed excellent synergistic electrocatalytic activity for the oxidation of quercetin, but also have good discernment capacity for the biological matrix and showed preferable selectivity for the determination of quercetin. Differential pulse voltammetry(DPV) was used for the quantitative determination of quercetin, the oxidation peak current was linear with the concentration of quercetin in the range of 1.0×10-8~2.0×10-6 mol/L with a detection limit of 2.0×10-9 mol/L which was more sensitive than most of the reported methods. Under the optimum conditions, the possible coexistence biological matrix including some metal ions, proteins, amino acids and other flavonoids with similar structures had no interference effect on the determination of quercetin. The proposed method was successfully applied to the sensitive determination of quercetin in human plasma samples with satisfactory recoveries.