Optical pH sensitive material based on bromophenol blue-doped polypyrrole

Optical pH sensitive materials have been developed using electrochemically synthesized polypyrrole (Ppy) film doped with bromophenol blue (BPB). The results have shown that the system Ppy–BPB color derives from a synergistic effect, where the sensitive pH range of the resulting film is larger than the individual species. The material is suitable for the optical determination of pH between 1.5 and 11.0 and is stable (more than 300 h), reproducible, and reversible. The results in saline solution show potential application of the Ppy–BPB film on physiological samples. However, Ppy–BPB films undergo irreversible spectral changes assigned to irreversible reduction when exposed to pH 11.0.