| Electrochemical sensors always attracted the researcher’s attention because of the advantages, such as fast response, high sensitivity, good stability, quantitative analysis, easy to miniaturization and low cost. In the chemical, biotechnology, medicine, environmental protection and other fields have used widely.Nano materials, referred to as "the most promising materials in the21st century", because of itself with different shape, size, composition, quantum size effect, small size effect and surface effect, they have presented many excellent properties. Such as the specific surface area, high surface reactivity, high catalytic rate, and the strong adsorption ability, becoming a cutting-edge attention of researchers. In the nano materials, the researchers are most interested in the metal nanoparticles due to its important properties and multiple applications. Metal nanoparticles have large specific surface area and high free energy, when modified electrodes, can make the sensitivity of the electrode increased significantly. Because of their excellent chemical stability, electrical conductivity and catalytic activity, silver nanoparticles get more and more attentions. It is a doable job to apply silver nanoparticles into the research of modified electrode to realize the detection of some certain substance. Dendrimers are currently developing new synthetic polymer. Dendrimers have three basic anatomical features:a core, repetitive branch units, and terminal functional groups, larger dendrimers are generally spherical in shape and contain interior void spaces. The unique properties of dendrimers resulting from their unusual structure, in surfactant, nano materials templates, gene carrier and membrane material show a broad application prospect. The preparation of nano materials using dendrimers as templates, not only stable, but the size and size distribution of nanoparticles can be controlled, and can be keep optical and catalytic properties of the nanoparticles. Since carbon nanotubes were found in1991, because of its unique mechanical characteristics, electrical properties and chemical stability, CNT has been one of the hotspots in nanotechnology research.The work of this paper focuses on the preparation of silver nanoparticles dendrimers nanocomposites and their application in electrochemical analysis. The main content is divided into the following several parts: Ⅰ.Electrochemical Oxidation of Glucose Based on Silver Nanoparticles/PAMAM/Multiwalled Carbon Nanotubes Modified Electrode.Silver nanoparticles by electrodeposition was immobilized onto the amino-terminated generation2PAMAM (G2PAMAM-NH2) molecular layer which bonded covalently with carboxylated multiwalled carbon nanotubes on the surface of glassy carbon electrode. Electrochemical oxidation of glucose was using this modified electrode as the working electrode to realize the research of glucose oxidation. The cycle voltammetric technique, AC impedance technology and chronoamperometry were employed to study the oxidation mechanism of glucose. The modified electrode has shown effective catalytic behavior in the studies of glucose oxidation. The experimental results indicate that modifing electrode by binding covalently is not easy to fall off, fast response and good signals. The initial catalytic oxidation of glucose was depended on AgO. Further oxidation of glucose was relied on Ag2O step wise. It helped in understanding the mechanism of glucose oxidation more clearly.Ⅱ. Preparation Silver Dendrimer Nanocomposites (Ag-DNCs) using Dendrimers as Templates and the Research of its Property.This work reports on the synthesis and characterization of a novel electrochemical nanocomposites. We use generation4.5dendrimers as template, larger dendrimers are generally spherical in shape and contain interior void spaces, G4.5/Ag+composite was synthesized by complexing Ag+with G4.5PAMAM dendrimers interior amino group, in this paper we use AgNO3as raw material, sodium borohydride as reducing agent, and then make Ag-PAMAM composite nano materials. The influence factors in the process of composite nano materials prepared were investigated. the molar ratio of silver ions to PAMAM dendrimers and the reaction time are proved to play an important role. UV-Vis spectrophotometer, X-ray photoelectron spectroscopy and TEM were used to characterize the obtained dendrimer nano composites. It was found that under the condition of pH7and6hour stiring, when the ratio of Ag+to PAMAM is30, NaBH4to Ag+is2, the resulting Ag-PAMAM nanocomposites were stable and showed a narrow distribution size. We have performed the DPASV analysis on a glassy carbon electrode with saturated calomel as a reference and platinum as an auxiliary electrode. The current value was lined with the concentration of Ag-PAMAM composite nano materials ranging from3.8×10-11～3.8×10-9M. The detection limit is1.14×10-12M. This method possesses of the advantages of high sensitivity, distinguished flexibility and easily operation.Ⅲ. Supplement:Electrochemical Behavior of L-Tyrosine at Poly-eriochrome Black T Film Modified Glassy Carbon ElectrodeA poly (eriochrome black T) modified electrode was fabricated by electrochemical polymerization of eriochrome black T on glassy carbon electrode. And the electrochemical behavior of L-Tyr at this modified electrode were investigated by using cyclic voltammetry (CV) in this paper.The influence factors such as different Buffer solution, pH and the speed of scanning are discussed. The experiment indicates when using pH=2.0of NaH2PO4-H3PO4as supporting electrolyte, the process of the electrochemical oxidation reaction of L-tyrosine is irreversible. There is a sensitive oxidation peak when reaches0.933V (vs. SCE), and the peak current is increasing greatly. The oxidation peak current has a good linear relationship with the concentration of L-Tyr, its linear equation is ip (μA)=0.0163c (μmol/L)+2.429, its linear equation R2=0.9911, and its detection limit is8×10-6mol/L, S/N=3. The average recycling of testing sample is98.15%. The method is simple and fast, the result is satisfactory. |
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