Structural investigation of the Tb(III)-Ln(III) (Ln=Nd, Sm) binary system in molten LiCl-KCl eutectic salt by fluorescence resonance energy transfer

The structural change of Lncl63− and the complexation between metal chloride ions in the Tb(III)-Ln(III) (Ln=Nd, Sm) binary molten salt were investigated for the first time based on fluorescence resonance energy transfer (FRET). Tb(III) was used as a donor because the emission of Tb(III) is significantly overlapped with the absorption of various lanthanide elements. The collisional (or dynamic) quenching due to the energy transfer between Tb(III) and Ln(III) was evidently clarified in terms of fluorescence intensity and lifetime of the Tb(III) donor ions relative to the increasing concentration of acceptor ions, which were decreased at equal fraction. The Förster energy transfer was employed to measure the Förster distance (R0) and the center-to-center distance between lanthanide chloride ions in the molten LiCl-KCl eutectic. The Förster distance (R0) in the Tb(III)-Ln(III) binary system was firstly obtained and the center-to-center distance between lanthanide chlorides was calculated using the Förster distance (R0) and the energy transfer efficiency. Based on the FRET results, the structural change of Lncl63− and the complexation between metal chloride ions of interest were not found under the experimental conditions.