Optical sensing of parts per million levels of water in organic solvents using redox-active osmium chromophore-based monolayers

Optical sensing of parts per million (ppm)-levels of H₂O (10-300 ppm) in an organic solvent with robust, osmium chromophore-based monolayers is demonstrated. The H₂O-induced reduction of the covalently bound osmium(III) complex is fully reversible and can be readily monitored by UV/vis absorption spectroscopy. The thermally robust sensor can be reactivated chemically within 3 min.