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Fabrication And Application Of Electrochemical Sensors Derived From Graphene-based Nanohybrid Material

Posted on:2017-04-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z G LiuFull Text:PDF
GTID:1318330512450226Subject:Environmental Science
Abstract/Summary:PDF Full Text Request
Graphene, a novel carbon nanomaterial with a flat monolayer of carbon atoms, was discovered in 2004. Graphene possesses many excellent properties, including electrical, optical, thermal and mechanical properties because of its unique structure. The fundamental and applied researches on graphene have been a hot point in the fields of materials science, chemistry, physics and engineering. In recent years, graphene based nanohybrids have been widely studied and used as enhanced material of electrode in electrochemical sensors. These nanohybrids not only exhibit the large specific surface area, high conductivity and electric catalytic activity properties of graphene, but also demonstrate the excellent properties of other components in hybrid materials. In this thesis, we prepared three kinds of nanohybrid materials by combining graphene with cyclodextrin, nickel nanoparticles, hemin and gold nanoparticles. We carried out a series of systematic research works on controlled synthesis, electrochemical performance and synergistic effects of these nanohybrids, as well as their sensing applications to the flavonoids, glucose and biomarker. The main achievements are as follows:1. Electrochemical sensor for ultrasensitive determination of isoquercitrin and baicalin based on DM-?-Cyclodextrin functionalized graphene nanosheets. In this study,2,6-dimethyl-?-cyclodextrin (DM-?-CD) functionalized graphene nanosheets (DM-?-CD-GNs) were successfully synthesized by a simple wet-chemical strategy. The as obtained DM-?-CD-GNs were characterized by UV-vis spectroscopy, Fourier transform Infrared (FT-IR) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The new nanocomposite possesses the unique properties of graphene (large surface area and high conductivity) and DM-?-CD (high supramolecular recognition and enrichment capability). Based on the above properties, a highly sensitive electrochemical sensor was developed to detect two flavonoid drugs (isoquercitrin and baicalin). At the DM-(3-CD-GNs modified glassy carbon electrode (DM-?-CD-GNs/GCE), the peak currents of the two drugs increased dramatically compared with that on the bare GCE and GNs/GCE which due to the synergetic effects of GNs and DM-?-CD molecules. The linear response ranges for isoquercitrin and baicalin are 10 nM?3.0 ?M and 0.04?M?3.0?M, with the detection limits of 4 nM and 10 nM, respectively. The method might open up a new possibility for the widespread use of electrochemical sensors for monitoring of ultra-trace flavonoid drugs owing to its advantages of simple preparation, low cost, high sensitivity, good stability and reproducibility.2. A high performance nonenzymatic electrochemical glucose sensor based on polyvinylpyrrolidone-graphene nanosheets-nickel nanoparticles-chitosan nanohybrid. In this work, a new nanocomposite was successfully synthesized by chemical deposition of nickel nanoparticles (NiNPs) on polyvinylpyrrolidone (PVP) stabilized graphene nanosheets (GNs) with chitosan (CS) as the protective coating. The as obtained nanocomposite (PVP-GNs-NiNPs-CS) was characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Benefiting from the synergistic effect of GNs (large surface area and high conductivity), NiNPs (high electrocatalytic activity towards the glucose oxidation) and CS (good film-forming and antifouling ability), a nonenzymatic electrochemical glucose sensor was established. The nanocomposite displays greatly enhanced electrocatalytic activity towards the glucose oxidation in NaOH solution. The PVP-GNs-NiNPs-CS based electrochemical glucose sensor demonstrates good sensitivity, wide linear range (0.1 ?M-0.5 mM), outstanding detection limit (30 nM), attractive selectivity, good reproducibility, high stability as well as prominent feasibility for real sample analysis. The proposed method might open up a new possibility for widespread use of non-enzymatic sensors for monitoring blood glucose owing to its advantages of low cost, simple preparation and excellent properties for glucose detection.3. Label-free electrochemical aptasensor for carcino-embryonic antigen based on ternary nanohybrid of gold nanoparticles, hemin and graphene. In this study, a label-free electrochemical aptasensor for carcino-embryonic antigen (CEA) was successfully developed based on a ternary nanocomposite of gold nanoparticles, hemin and graphene nanosheets (AuNPs-HGNs). This nanocomposite was prepared by decorating gold nanoparticles on the surface of hemin functionalized graphene nanosheets via a simple wet-chemical strategy. The aptamer can be assembled on the surface of AuNPs-HGNs/GCE (glassy carbon electrode) through Au-S covalent bond to form the sensing interface. Hemin absorbed on the graphene nanosheets not only acts as a protective agent of graphene sheets, but also as an in situ probe base on its excellent redox properties. Gold nanoparticles provide with both numerous binding sites for loading CEA binding aptamer (CBA) and good conductivity to promote the electron transfer. The current changes, which are caused by CEA specifically binding on the modified electrode, are exploited for the label-free detection of CEA in a very rapid and convenient protocol. Therefore, the method has advantages of high sensitivity, wide linear range (0.0001-10 ng mL-1), low detection limit (40 fg mL-1) and attractive specificity. The results illustrate that the proposed label-free electrochemical aptasensor has a potential application in the biological or clinical target analysis for its simple operation and low cost.4. Summarized the research results of this paper and speculated the future research directions according to the deficiency in the study.
Keywords/Search Tags:graphene, electrochemical sensor, flavonoid, glucose, carcino-embryonic antigen
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