STABILITY OF POLYPYRROLE AND POLY(3,4-ETHYLENEDIOXYTHIOPHENE) FOR BIOSENSOR APPLICATION

The electrochemical polymerization of pyrrole and 3,4-ethylenedioxythi ophene (EDT) in phosphate buffer solutions in the presence of poly(sty rene sulfonate) (PSS) was investigated by means of cyclic voltammetry and chronoamperometry. From the measurements it was found that the ele ctrochemical polymerization of pyrrole and EDT could be initiated at 6 00 mV and 800 mV respectively in the phosphate buffer. To evaluate the stability of polypyrrole + poly(styrene sulfonate) (PPy + PSS) and po ly(3,4-ethylenedioxythiophene) + poly(styrene sulfonate) (PEDT + PSS) films, a constant potential was applied to films immersed in phosphate buffer solutions. PEDT + PSS was found to be much more stable than PP y + PSS under constant polarization conditions. After polarization for 16 h at 400 mV and pH 7.5 only 5% of the original electrochemical act ivity of PPy + PSS remained, whereas PEDT + PSS retained 89% of its or iginal activity. The stability is strongly dependent on the magnitude of the polarization potential and the pH of the buffer solution.