Sol–gel immobilised ruthenium(II) polypyridyl complexes as chemical transducers for optical pH sensing

A range of fluorescent ruthenium(II) polypyridyl complexes have been employed in an optical sensor device for pH analysis. The dye materials were immobilised in a sol–gel glass matrix and characterised upon exposure to aqueous buffer solutions. Changes of below 0.1 pH units were detectable using these dye-doped glass films, and linear ranges as large as pH 3–9 were observed. Sol–gel immobilisation effectively enhanced the operating range of these materials compared to solution. Interference from fluorescence quenching due to molecular oxygen was found to place important restrictions on the nature of dyes suitable for this application.