Fibre optic oxygen sensor for long term use in jet fuel, featuring phosphorescent dye chemically bonded to functionalised silica

Abstract Five new compounds, termed “metallo-porphyrin silicas”, have been synthesised by the reaction of functionalised silicas with platinum (II) meso tetrakis (pentafluorophenyl) porphyrin. The reaction resulted in the elimination of hydrogen fluoride to create a covalent bond between a functional group of the silica and the para carbon atom of a pentafluorophenyl group. Four out of the five new compounds exhibited phosphorescence under irradiation with u.v. light at ∼400 nm, and in all four cases the phosphorescence was quenched by molecular oxygen. Stern Volmer plots of the four phosphorescent compounds showed that the aminopropyl derivative gave the largest response at 400 nm over a concentration range of 0–20% oxygen. Further tests were undertaken on this compound that showed that the output was dependant not only on oxygen concentration but also temperature (−17 °C–40 °C). A prototype probe suitable for testing oxygen content in aviation fuels was developed using an optical fibre. It was possible to detect changes in oxygen concentration in jet fuel. The results demonstrate the potential of this approach to provide a low cost, low power resilient probe for the detection of oxygen in aviation fuel.