STUDY ON SOLUBLE POLYPYRROLE AS A COMPONENT IN ALL-SOLID-STATE ION-SENSORS

Soluble conducting polypyrrole (PPy) was chemically synthesized by usi ng dodecylbenzene sulfonic acid (DBSA) as dopant. Electrodes were prep ared by solution casting on glassy carbon (GC) substrates. They were c haracterized by potentiometric, cyclic voltammetric (CV) and electroch emical impedance spectroscopic (EIS) measurements. PPy(DBSA) modified electrodes showed good reproducible cationic response to Ca with the s ensitivity of 27.2 +/- 0.2 mV decade(-1) which remained practically co nstant over 10 d. The standard potential, however, was found to drift 70 mV over the same time period. The doping process of the PPy(DBSA) f ilm was investigated by cyclic voltammetry and EIS in 0.1 M CaCl2. The most significant change in the impedance spectra of the PPy(DBSA) fil m takes place between -500 mV and -400 mV which coincides with the beg inning of the oxidation wave in the cyclic voltammogram of the film. T he impedance spectra were fitted to an equivalent circuit and the redo x sensitivity of the PPy(DBSA) film was also studied. (C) 1998 Elsevie r Science Ltd. All rights reserved.