Determination of pH using a polyaniline-coated piezoelectric crystal

A pH sensor was constructed with a polyaniline-coated piezoelectric crystal. Its resonant freqency is a function of pH in the range 2–12. It has a good selectivity, a long life and a wide linear resoponse range. In the present work, polyaniline films were electrochemically deposited onto one of the two gold surfaces on the quartz crystal by cyclic voltammetry. Some factors that influence the resonant oscillation frequency have been investigated in detail.