Impedance studies of a nano-structured conducting polymer and its application to the design of reliable scaffolds for impedimetric biosensors

Electrochemical impedance spectroscopy (EIS) as a powerful, non-invasive and informative technique was used to obtain important information about kinetics of doping process in conducting polymers. Polypyrrole (PPy) and its derivatives can form conducting polymer films which represent excellent charge transfer behaviors during doping processes. It can also have a wide range of applications in bioelectrochemistry. In the present study the conducting polymer of α-carboxy pyrrole (α-COOH-PPy), appended onto the underlying film of PPy, was prepared by electrochemical methods and its behavior was analyzed using EIS. From highly accurate fitting of impedance results it was found that the charging mechanism is governed by the diffusion process. In addition, the impedance analyses provided values for the bulk polymer parameters including diffusion coefficient (D), equilibrium capacitance (C0) and diffusion resistance (R0). The surface morphology of the polymeric film was characterized using scanning electron microscopy (SEM). The film was then used to immobilize the cytochrome C (cyt-C) and to perform its electrochemical studies. The modified cyt-C/α-COOH-PPy electrode was used for electrocatalytic reduction of H2O2 in solution and its viability as a new impedimetric biosensor was examined. Based on the calibration curve obtained for the proposed impedimetric biosensor, the limit of detection and relative standard deviation were evaluated as 0.25 μmol L−1 and 7%, respectively. Finally, the prolonged stability test was performed and high stability and reproducibility of the new biosensor was confirmed.