Sensing of H2O in D2O: is there an easy way?
We report luminescence sensor materials toward H2O detection in D2O with the highest sensitivity obtained to date (24 %/%(H2O)). The materials are based on the mixture of water-soluble terbium and europium compounds. High sensitivity, exceeding previously reported values by an order of magnitude, is reached thanks to the high number of the coordinated water molecules. Analytical description of the sensors based on the terbium-europium systems was performed. It proved that the sensitivity is proportional to the number of the inner-sphere water molecules, which makes impractical further search for such materials among insoluble coordination compounds with organic ligands. Thoughtful material selection allowed to develop and easy way toward sensing of H2O in D2O.