A bipyridazine fluorophore, DHP2, was explored as a pH sensor. A solution of bipyridazine showed
fluorescence intensity decrease as acid was added to the solution. The fluorescence intensity of the solution
containing DHP2 was highly sensitive to acidic solution in the range from 2 to 9.7, with a Stern-Volmer
quenching constant of K'<sub>acid</sub> as 9.7. However, the fluorescence intensity of DHP2 dissolved solution was not
significantly changed by the addition of base. DHP2 was successfully doped in a transparent polymer to
afford a thin film sensor. The fluorescent polymer film sensor was able to detect pH in the range from 3 to 12.