<title>Fiber optic oxygen sensors based on the sol-gel coating technique</title>

Abstract

Two fiber optic oxygen sensor designs were demonstrated by sol-gel coatings doped with an organo-metallic complex, ruthenium (II) tris-4,7-diphenyl-1,10-phenanthroline. The first design implemented a porous optical fiber coated with sol-gel that showed high sensitivity (less than 1 ppm) towards oxygen gas and a dynamic range up to 1% oxygen. The second optical sensor was based on a collimator device which involved a sol-gel film that was spin coated onto a silica glass disk. Compared to the porous fiber approach, a faster response time and lower oxygen gas sensitivity were determined for this sensor configuration. According the lifetime decay behavior of a sol-gel spin coating, the luminescence decay of the ruthenium complex followed a single exponential decay in nitrogen and air. Also, the spin coated sample showed a greater degree of quenching according to the Stern-Volmer ratio, at greater oxygen concentrations than the ratio calculated for the monolithic film. Analysis of the lifetime decay behavior of the different forming methods revealed that the micro-structure of the gel was dependent upon the type of sol-gel deposition. In this case, spin coated gels resulted in a denser coating than the monolithic film. As a result, these differences in the sol- gel micro-structure were used to discuss the different behavior of the collimator sensor with respect to the porous fiber oxygen sensor.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.