Abstract A fiber optic sensor for the determination of oxygen in liquids is presented. Potential applications range from environmental analytics to medical diagnostics and process control. The sensing principle is based on dynamic luminescence quenching by oxygen. A ruthenium complex used as oxygen-sensitive dye is immobilized on an optical fiber by adsorption and subsequent coating with a membrane. Excitation of the Ru complex is performed both by the evanescent field associated with light guided in the optical fiber and by direct irradiation, dependent on the refractive index profile of the fiber/membrane/medium system. The emitted light is collected by the same fiber. The temperature-controlled sensor is exposed to a liquid stream of defined oxygen concentration. Oxygen is detectable in the range 0–800 Torr, with a resolution of 2 Torr in the 0–100 Torr range and of 2% for oxygen partial pressures above 100 Torr. Response times are of the order of 30 s. Generally, sensor signals are affected by sample medium. Optimized sensors exhibit a good performance, with no effects of protein adsorption or background fluorescence, even in serum.
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