Polypyrrole-based amperometric cation sensor with tunable sensitivity

Abstract

This article presents a novel technique to quantify the kinetics of faradaic response in polypyrrole (doped with dodecylbenzenesulfonate) (PPy(DBS)) and its application in developing a cation sensor. This technique is based on the analysis of the impedance/admittance transfer function of PPy(DBS) and the representation of its reduction chronoameprometric response using system poles and residues. The results presented in this paper demonstrate that the pole of the transfer function is an intrinsic quantity and the residue corresponding to the system pole is an extrinsic quantity. The residue of the system pole for a redox-step potential is dependent on the concentration of cations and is observed to have linear dependence on electrolyte concentration ( R2 > 0.9). Thus, the residues can be used to accurately estimate the concentration of cations in an electrolyte solution and enables the use of PPy(DBS) as a high-precision cation sensor. The experimental investigation supporting this analysis demonstrates that the sensitivity of residue to concentration can be varied by equilibrating PPy(DBS) a priori in the cation containing solution of known concentration and by varying the morphology of PPy(DBS).