Evaluation of a luminescent ruthenium complex immobilized inside Nafion as optical pH sensor

The development of an optical pH sensor based on immobilization of a luminescent ruthenium complex, [Ru(bpy)2(dhphen)]2+ (bpy = 2,2′-bipyridine, dhphen = 4,7-dihydroxy-1,10-phenanthroline) in Nafion film is described. The sensor has a useful pH range of 1–8. The typical response time of the sensing film is 2–5 min. The polyanionic nature of the Nafion film eliminates interference from anions. The sensor also shows minimal interference effects from alkali metal and divalent cations and has good photostability and reproducibility.