Polypyrrole Nanospheres – Electrochemical Properties and Application as a Solid Contact in Ion-selective Electrodes

Polypyrrole nanospheres of uniform size, close to 40 nm, of highly active and unblocked surface were obtained. The novel synthetic approach applied used poly(n-butyl acrylate) microspheres to deliver the monomer (pyrrole) to the oxidant (iron(III) nitrate) aqueous solution. Small portions of dispersion of these nanoparticles were coated on glassy carbon electrodes, yielding stable films suitable for electrochemical studies. Electrochemical experiments: Cyclic voltammetry and electrochemical impedance spectroscopy revealed high transport rate of ions inside the polymer and high charge transfer reactions rate, manifested in highly capacitive characteristics of such layers. These properties are different from those of classical electrochemically obtained polypyrrole. Due to their capacitive properties, polypyrrole nanospheres layers were applied as a solid contact in ion-selective electrodes, on example of a potassium-selective potentiometric sensor. Although the capacitance of the conducting polymer was much lower than in the absence of the ion-selective membrane, it was sufficiently high to obtain sensors with stable potentiometric signals.