Electrochemical Studies On Linear, Dendritic Functional Polymers And Their Application

In recent years, the polymer/metal nanocomposites have attracted a great deal of attention because of their unique properties and potential applications in functional materials, chemical/electrochemical sensors, bioelectrocatalysis. These nanocomposites can retain the bioactivity of proteins on the solid electrode surface, and play an important catalytic role in direct electron transfer of redox proteins.On the basis of relative literatures, a nove network nanocomposite was synthesized using the first generation polyamidoamine dendrimer (G1 PAMAM) as dispersant agent. And a third-generation horseradish peroxidase (HRP) biosensor was built on the glassy carbon electrode modified by multi-wall carbon nanotubes (MWCNTs) for the high sensitive detection of H2O2. Meanwhile, in-situ FTIR spectroelectro-chemisty and electrochemical quartz crystal microbalance (EQCM) were used to study the electro-oxidation and electropolymerization mechanism of a linear conductive molecule (1,4-bis(4-aminophenyletynyl)benzene, OPE-NH2) on the gold electrode. The main work is summarized as follows:(1) A novel nanocomposites with homogeneous size and distribution was prepared by the reduction of HAuCl4 by NaBH4 using the first generation polyamidoamine dendrimer as dispersing agent. The influences of reaction time, reaction rate, pH and the amount of reducing agent on the formation of nano-composite were investigated. The results have shown that [AuCl]- and PAMAM formed a complex after stirring for a certain time and the gold nano-composites were prepared by in situ-synthesis with reducing agents. Compared with the SEM image of neat gold nanoparticles, the nanocomposites prepared by the in situ-synthesis showed better dispersibility and three-dimensionally net-work ordered structure.(2) On the basis of the novel nanocomposites, HRP was immobilized on MWCNTs-COOH modified glassy carbon electrode (GCE). The direct electrochemistry of HRP was realized and the new enzymatic electrode exhibited very good performance for determination H2O2. Under the optimum conditions, the current response of the enzyme modified electrode at-0.3 V was linear with H2O2 concentration from 18μmol L-1 to 20.80 mmol L-1, with sensitivity as high as 377.78μA L mmol-1 cm-2 (r=0.9992) and detection limit down to 6.72μmol L-1 (S/N=3). The biosensor exhibited good stability and reproducibility.(3) The electrochemical process and oxidation mechanism of the OPE-NH2 linear molecule were investigated via real-time, on-line methods of in-situ FTIR spectroelectrochemisty and electrochemical quartz crystal microbalance (EQCM) for the first time. It was found that the monomer concentration and oxidation potential had great influence on the growth of the poly-OPE film. Companying with the increase in polymerization degree, the poly-OPE film became more and more smooth and compact, and exhibited poor electrical conductivity. Just behaved as aniline, OPE-NH2 could be electro-oxidized to radical cations, which were confirmed by in-situ spectroelectrochemistry to undergo para (N-N) or ortho (N-C) coupling reactions and produced polymer with a larger conjugatedπ-electron system.