The quantitative detection of oxygen is important for industrial, automotive and medical applications. We report on a reflection mode fiber optic oxygen sensor based on the ³O₂ quenching of the red emission from hexanuclear molybdenum chloride clusters. Measurements of the probe operating in a 0-21% gaseous oxygen environment have been obtained. The luminescence signal increases with decreasing oxygen concentration in accordance with theory. We observe clearly resolvable steps in the sensor response for changes of 0.1% absolute oxygen concentration in the 0 to 1.0% range. The response time of the fiber probe is theoretically predicted to be 1 s. The present probe is thermally stable to 200 ° C, limited by the polymer matrix. Immobilization of the clusters in a porous sol-gel matrix will enable oxygen sensing in gaseous environments at elevated temperatures as well as liquid environments with varying salinity and pH.

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