Preparation Of Graphene Nanocomposite Film Chemical Modified Electrodes And Their Analytical Applications

For their outstanding advantages such as high sensitivity, good selectivity, fast detection speed, and low cost, chemically modified electrodes?CMEs? have applied more and more widely and become one of hot topics of research in the field of electrochemistry and electroanalytical chemistry. Graphene, one of the new two-dimensional nanometer carbonmaterials, has drawn the attention of the people in the field of nanoscience and nonotechnology owing to its unique structure and excellent physical and chemical properties. In this present thesis, three kinds electrochemical sensing platforms respectively for biphenol A?BPA?, caffeine?CAF? and ultraviolet ray absorber 2- hydroxyl-4-methoxy-2-benzophenone?BP-3? with high sensitivity, good selectivity and high stability were prepared based on excellent electrical conductivity, large specific surface area, high catalytic activity and strong biological compatibility of grapheme based composites, and their applications in environmental and food analyses were studied. The main investigation contents consisted of four parts as follows:1. Concept, principle and preparation methods of CMEs were introduced briefly, and the advances on applications of CMEs, especally grapheme based CMEs, in environmental and food analyses were reviewed in detail.2. Graphene oxide?GO? was prepared from graphite power by a modified Hummers method at first, and then a 3D gold nanoparticles-poly?L-glutamic acid?/grapheme oxide composite film modified electrode was prepared by combining the outstanding properties of nanometer gold?AuNPs? and L-glutamic acid?L-GA?. Surface morphology and structure of the modified electrode were characterized by scanning electron microscopy?SEM?, Fourier transform infrared spectroscopy?FT-IR? and X ray powder diffraction?XRD? and the electrochemical behavior of BPA on the modified electrode was investigated in detail by cyclic voltammetry and differential pulse voltammetry. The results showed that the modified electrode displayed good electrical catalytic ability toward oxidation of BPA in phosphate buffer solution?PBS? of pH = 6.0. Under the optimum experimental condition, the oxidation peak current of BPA was directly proportional to its concentration in the ranges of 0.009 to 0.13 umol L^-1 and 0.13 to 1.15 umol L^-1 respectively with a detection limit down to 0.3nmol L^-1. The proposed method was successfully applied to determine bisphenol A in wastewater with a satisfactory result.3.Graphene?Gr? was prepared from graphene oxide by NH₂NH₂.H₂ O reduction method, and its morphology and structure were observed by scanning electron microscopy?SEM?, X-ray photoelectron spectroscopy?EDS?, Fourier transform infrared spectrometer?FT-IR?, Raman spectroscopy?Raman? and powder X-ray diffraction?XRD?. And then based on prepared Gr, a 3D Au NPs- poly?L-cysteine?/Nafion/Gr composite film modified electrode was prepared by electrochemical polymerization method and the electrocemical behavior of CAF was exammed on this modified electrode by cyclic voltammetry and differential pulse voltammetry. The results showed that the modified electrode has outstanding electro-catalytical properties for the electrochemical oxidation of CAF. A new analytical method for CAF detection was developed based on this modified electrode with a linear range from 1 to 100?mol L^-1?R² = 0.9983, N = 6? and a detection limit as low as1.0 nmol L^-1 and applied successfully for determination of CAF in functional beverages.4. A chitosan?CS?/ionic liquid?IL?/graphene oxide?GO? composite modified electrode was fabricated by using a drop coating method, and its morphology and structure were characterized by scanning electron microscope?SEM? and Fourier transform infrared spectrometer?FT-IR?. At the same time, the electrochemical behavior of the ultraviolet ray absorber 2- hydroxyl- 4-methoxy-2-benzophenone?BP-3? was observed by cyclic voltammetry and differential pulse voltammetry. It was found that the modified electrode exhibited a high catalytic activity toward oxidation of BP-3. Under the optimum experimental conditions, a favorable linear relationship was obtained between the oxidation peak current and the concentration of BP-3 in the range of 282¹992 nmol L^-1, and the detection limit was 0.15 umol L^-1?S/N=3?. The modified electrode, with a high long-term stability and good reproducibility, had been successfully applied for the determination of BP-3 in the sewage.