Sensing of H2O in D2O: is there an easy way?

We report Tb-Eu based luminescence sensor materials toward H2O detection in D2O with the highest sensitivity of 24%/%(H2O), exceeding the previously reported ones by an order of magnitude. The theoretical description of such sensors based on the terbium-europium systems was performed and proved that the sensitivity is proportional to the number of inner-sphere water molecules.