Synthesis And Characterization Of New Conducting Polymers And Biological Sensors

3 & ABSTRACT 1.Electrochemical synthesis and properties of poly(azure B) A blue poly(azure B) film has been synthesized using repeated potential cycling between ?.25 and 1.10 V (versus SeE). The electrolytic solution consisted of 2.5 mmcl dm~3 azure B, 0.5 mci dm3 NaC1 and 0.2 mel dm~3 NaH2PO4 at the pH range of 2.0 to 11.0. The in situ visible spectrum during electrolysis of azure B shows that the intensity at 740 nm peak increases with increasing numbers of potential cycles, attributing to the formation of poly(azure B). The wavelength of its corresponding absorption peak is 98 nm . longer than that of azure B. The polymerization rate is strongly affected by pH values. The anodic peak potential and cathodic peak potential of the poly(azure B) in a solution of pH 3.0 are not affected by increasing the scan rate from 25 to 600 mV s? Poly(azure B) has good electrochemical reversibility and fast charge transfer characteristic at the pH range of 2.0 and 11.0. The conductivity of poly(azure B) is 1.5 x l0~?S cm? According to the differences between FTIR spectra of poly(azure B) and azure B, an electrochemical polymerization mechanism of azure B is proposed in this paper. 2. Detection of intermediate during the electrochemical polymerization of azure B and growth of poly(azure B) film The electrochemical polymerization of azure B has been studied using the rotating ring-disk electrode(RRDE) and the electrochemical quartz crystal niicrobalance(EQCM). The electrolytic solution consisted of 2.5 mmcl dm?azure B, 0.2 mel din?NaH2PO4 and 0.5 mci din?NaC1 with various pH values. An intermediate 4 ~H )v*~眎~ generated at the disk electrode was collected at the ring electrode. The collection efficiency increases with decreasing ring potential as well as increasing rotation rate. Thus, the intermediate is to carry a positive charge species and not too stable. Based on the determination of the frequency response of the EQCM, the polymerization rate of azure B increases slowly before the fifteenth cycle, and then increases quickly with increasing number of potential cycles. The EQCM is a very useful tool for determination of the starting polymerization potential of azure B, which is 0.60 V(vs.S CE) in this case. The maximum frequency difference during the oxidation and A reduction processes of poly(azure B) film in the solution with pH 3.0 is 174.7 Hz, which corresponds to the mass change of 0.99 ~.tg cm~2. 3. Electrochemical copolymerization of aniline and azure B The electrochemical copolymerization of aniline and N,N,.N?triinethylthionin (azure B) in aqueous solutions has been carried out using potential sweep method. The optimum conditions for the coelectrodeposition are that the pH value and the temperature of electrolytic solution were controlled at 5.57 and 30C, respectively, and the scan potential range was set between ?.25 and 1.10 V (versus SeE). The copolymerization rate of aniline and azure B is about 3 times larger than that of aniline in the absence of azure B. The copolymerization of aniline and azure B was verified from the results of visible spec...