An improved optical pH sensor based on polyaniline

An optical pH sensor based on polyaniline is presented in this paper. Polyaniline films were prepared by chemical oxidation at room temperature. By increasing reaction time for up to 12 h, the stability of the polyaniline film was significantly improved. The film showed rapid reversible color change upon pH change. Solution pH could be determined by monitoring either absorption at a fixed wavelength or the maximum absorption wavelength of the film. The optical pH sensors can be exposed in air for over 1 month without any deterioration in sensor performance.