Full-Range Ratiometric Detection of D2O in H2O by a Heterobimetallic Uranyl/Lanthanide Framework with 4f/5f Bimodal Emission

A uranyl–europium heterobimetallic compound, (TEA)3[(UO2)6Eu­(H2O)4(PPA)6] (H3PPA = phosphonoacetic acid, TEA = tetraethylammonium cation), was synthesized under mild hydrothermal conditions. The emission spectrum contains characteristic electronic transition features of both Eu3+ and UO22+, while the peak intensity of Eu3+ is notably higher than that of UO22+. This is primarily attributed to the energy transfer from uranyl to europium in the structure. Significantly, a positive correlation between the Eu3+ peak intensity at 621 nm and the D2O content can be established in the aqueous system, while the uranyl peak intensity is almost unchanged, allowing for the full-range ratiometric detection of D2O in H2O.