Lifetime-based pH sensor system based on a polymer supported ruthenium(II)complex

A new luminescence lifetime-based pH sensor system is described. The system is based on [Ru(Ph(2)phen)(2)DCbpy](2+) (DCbpy = 4,4'-dicarboxy-2,2'-bipyr idine) immobilized in a mixed domain network copolymer utilizing hydrophobi c regions in a hydrophilic, water-swellable, poly(ethylene oxide) matrix. T he metal complex binds irreversibly to the hydrophobic domains leaving the pH-sensing COOHs projecting into an aqueous-rich poly(ethylene oxide) regio n. The complex shows a strong pH dependence of its lifetime (3-4-fold) and provides a usable pH range of about 3-5. The long (similar to 1 mu s) excit ed-state lifetime and visible absorption of the sensor simplifies measureme nts. A model for the combined pH and oxygen-quenching sensitivity of the co mplex is provided; this allows use of the pH system over a wide range of ox ygen concentrations. The combined polymer sensor is easy to prepare and req uires no covalent chemistry. Further, the polymers enhance the luminescence of the complex and minimize interference from oxygen quenching.