Luminescence lifetime-based sensor for relative air humidity

The development of new sensitive coatings for fibre-optic sensors that utilize the Langmuir-Blodgett technique is described. Monomolecular thin solid films containing phosphorescent water-soluble Pt- and Pd-porphyrins and amphiphilic surface-active polymer have been prepared by an original method and transferred onto solid supports. The solid-state coatings thus obtained show intense long-decay phosphorescence in ambient air, which is found to be sensitive to the water content in the environment, i.e., the relative humidity (RH) of air. The coatings have been studied by optical methods with emphasis on luminescence quenching and lifetime measurements. The results are applied to luminescence lifetime-based sensing of RH and a corresponding fibre-optic prototype device has been created.