The Design And Preparation Of Green Carbon Nanocomposites And Their Application In The Detection Of Food Dyes

Because of its special structures, good stability and catalytic activity properties, carbon nanomaterial has been applied in different fields such as environment, biotechnology, medicine, food control, electrochemical sensor and so on. Also carbon nanomaterial has been extensively applied in the preparation of electrochemical sensors. However, because of its poor dispersibility in water which restricted their further application.Considering the poor dispersibility of carbon nanomaterials, this thesis focuses on preparation of functionalized carbon nanomaterials with more better dispersibility, much larger speic surface and much higher conductivity. Novel dispersing agent was prepared here with facile method and the was further applicated in the functionalization of carbon nanomaterials. The application of the carbon materials in the analysis and detection was discussed. We further studied the diffusivity of ion in the electrode modifying materials, the adsorbing capacity of measured substance and electrochemical behavior of dyes.This dissertation includes the following four parts:1. Highly dispersed carbon nanotube in new ionic liquid-graphene oxides aqueous dispersions for simultaneous determination of Ponceau 4R, Allura red and TartrazineIn order to improve the dispersibility of carbon nanotube in water, new ionic liquid-graphene oxides aqueous dispersions (GO/IL) were presented by simply turning pH at room temperature. In basic condiction, the introduction of IL of 1-butyl-3-methylimidazolium hexafluorophosphate in to GO water not only resulted in high dispersibility of MWCNTs and also resulted in high conductivity. The introduction of [BMIM][PF6] not only minimize the defects of poor electrical conductivity of GO and more interesting is that the carbon nanotube (CNT) can be highly dispersed in this GO/[BMIM][PF6] water through a simple and facile ultrasonic method at room temperature, forming a new composite of GO/[BMIM][PF6]/CNT with high dispersibility. This novel composite enhanced its electrochemical signal obviously in the simultaneous determination of Ponceau 4R, Allura red and Tartrazine in alcoholic drink, the linear responses of Ponceau 4R, Allura red and Tartrazine were in the concentration ranges of 1.0×10-9-1.0×10-6, 8.0×10-10-5.0×10-7, and 1.0×10-8-1.0×10-6mol L’1 with the detection limits of 8.0×10-10,5.0×10-10, and 7.0×10-9mol L-1 (S/N=3), respectively. The fabricated sensors were further successfully applied for the detections of Ponceau 4R, Allura red and Tartrazine in practical samples. New GO/IL water provides a new material used to disperse other carbon materials such as graphene and fullerene. This electrochemical biosensor reported here should be applicable to build a broader application in biological and electrochemical analysis.2. The preparation of cyclodextrin-ionic liquid inclusion complexes functionalized reduced graphene oxide for determination of Sunset yellow in foodsIn order to improve the dispersibility of RGO in water, a new cyclodextrin-ionic liquid (IL@βCD) inclusion complexes was prepared by a simple method. And the new inclusion complexes was succefully used to disperse reduced graphene oxide in water. In this article, we demonstrate a simple wetchemical strategy for the preparation of IL@βCD/RGO composites, which exhibited high solubility and stability in polar solvent. The obtained IL@βCD/RGO were characterized by UV-vis spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy, and electrochemical impedance spectroscopy which confirmed that IL@βCD had been effectively functionalized on the surface of RGO. And the introduction of [BMIM][PF6] not only minimize the defects of poor electrical conductivity of βCD and more interesting is that the RGO can be highly dispersed in this IL@βCD inclusion complexes. This novel composite enhanced its electrochemical signal obviously in the measurement of Sunsetyellow in foods and exhibited a wider linear response ranging from 2.0×10-9 to 1.5×10-6mol L-1. The detection limit of 3.0×10-10 mol L-1 at a signal to-noise ratio of 3.0.3. The preparation of poypyrrole functionalized carbon nanotube composites and simultaneous determination of the isomers in foodsIn order to further improve the dispercibility of carbon nanotube in water, a novel polypyrrole-carbon nanotubes (ppy-CNT) composite was greenly prepared by in situ one-step polymerization of ppy in the presence of CNTs for fabrication of food sensors. Due to the increasing dispersibility and effective surface area of the CNT caused by decoration of ppy to the CNT, the proposed electrode exhibited excellent electrochemical sensitivity and high selectivity toward the oxidation of Amaranth and Ponceau 4R. The linear response ranges for Amaranth and Ponceau 4R were 5.0×10-9-5.0×10-7 mol L-1, and 8×10-9-1×10-6 mol L-1 and corresponding detection limits as low as 5.0×10-10 and 1.0×10-9 mol L-1, respectively. This method has been successfully applied in the simultaneous determination of Amaranth and Ponceau 4R in drinks. So the new ppy-CNT composites provide a good platform for food analysis.4. Facile synthesis of Au supported on ionic liquid functionalized reduced graphene oxide for simultaneous determination of Sunset yellow and Tartrazine in drinksIn orde to improve the dispersibilty and enhance the conductivity of reduced graphene oxide (RGO), a simple and green method was developed to directly attaching gold nanoparticles (Au-NPs) on onic liquid functionalized reduced graphene oxide (ILRGO). With the assistance of 1-allyl-3-methylimidazolium chloride (AMIM-Cl), ILRGO were dispersed easily in aqueous solution and exhibited an improved conductivity. Meanwhile, the Au nanoparticles uniformly loaded on the surfaces of the ILRGO from the TEM. These advantages made the ILRGO-Au composites were successfully employed in the fabrication of facile and sensitive electrochemical sensor applied to the simultaneous determination of Sunset yellow (SY) and Tartrazine (Tz) in drinks. In the presence of constant concentration of one of the components, the concentrations of SY or Tz gave linear response ranges equal to 4.0×10-9 to 1.0×10-6 mol L-1 for SY and 7.0×10-9to 1.5×10-6 mol L-1 for Tz with detection limits of 5.2×10-10 mol L-1 for SY and 8.3×10-10 mol L-1 for Tz (S/N=3), respectively. The new sensor showed good reproducibility and repeatability toward simultaneous determination of SY and Tz. And it was applied successfully in the determination of SY and Tz in Mirinda, Fanta and RIO cocktail drinks. This new method provides a good platform for food analysis and bioanalysis.