Voltammetric Properties of All-solid State Ion-selective Electrodes with Multiwalled Carbon Nanotubes-poly(3- octylthiophene-2,5-diyl) Nanocomposite Transducer

Voltammetric response of an all-solid-state ionselective electrode was studied on example of potassiumselective sensor with poly(vinyl chloride) based membrane and nanocomposite transducer containing poly(3- octylthiophene-2,5-diyl) and multiwalled carbon nanotubes. Factors limiting the rate of the electrochemical process and the response were discussed. The challenge in voltammetric applications of ion-selective electrodes is thickness of the plastic membrane. It was found that although a relatively thick ion-selective membrane was applied, as typically used in potentiometric studies, the position of the reduction peak, corresponding to potassium ions incorporation, was dependent on ions concentration in a Nernstian manner. This opens possibility of deviation from the paradigm of ultrathin membranes in voltammetric applications, thus potentially extending the sensors lifetime. The high resistance of the membrane did not affect the voltammetric characteristics, because the resistance was independent of ions concentration in solution. On the other hand, high resistance results in charge trapping effect in the solid contact material, leading to advantageous retention of the oxidized-conducting state of the solid contact, independently of the applied electrode potential.