Optical thin-film sensors for the determination of aqueous halide ions

Fourteen thin-film optical sensors in which halide-sensitive fluorophores are immobilized in a thin copolymer film (approximate to 50 mu m, dry) have been developed and characterized. The sensor films use rhodamine, 6-methoxyquinoline, and harmane dyes which have been functionalized and bound to a hydrophilic copolymer. The sensor films are reversibly capable of determining aqueous bromide and iodide with approximate to 4 and 2% accuracy, respectively, at concentrations of around 10(-3) mol dm(-3), and are more sensitive than previous plastic sensor fabrications. The 90% response time to molar iodide is approximate to 30-60 s. A combination of sensor films allows the simultaneous determination of both I- and Br- in a mixed-halide solution. The interference of several ions, including pseudo-halides, on the sensor films has been studied.