CHARACTERIZATION OF A CHEMORESISTOR PH SENSOR-BASED ON CONDUCTING POLYPYRROLE

An electrode based on chemically polymerized polypyrrole has been fabr icated for use as a pH sensor. The electrode is basically a polypyrrol e film connected by two carbon conductors to form a chemoresistor. The changes in resistance of the polypyrrole (PPy) film are determined by either drawing a constant current through the film and monitoring the potential changes or applying a constant potential across the film an d monitoring the current changes. The electrode fabrication is optimiz ed. The resulting electrodes are subjected to stability tests in vario us media. A response to hydronium ion in terms of electrical resistanc e is obtained in a wide range of pH buffers. The selectivity for hydro nium ion and the effect of ionic strength on the electrode response ha ve been investigated.