Energy transfer between rare earths in layered rare-earth hydroxides.

Energy transfer between rare earths in layered rare-earth hydroxides (LRHs) is worth the intensive study because the hydroxyls that act as the bridge connecting the neighbouring rare earths would generate non-radiative transitions. This study focuses on the energy transfer in the intralayer and the adjacent layers of LRHs. A series of LEu Tb Hs ( = 0, 0.05, 0.2, 0.5, 0.8, and 0.95) was synthesized, the basal spacing ( ) was adjusted from 8.3 to 46 Å through ion-exchange process, and unilamellar nanosheets were prepared through a delamination process. The luminescence behaviours of the samples demonstrated the following: (1) for the delaminated nanosheets, the quenching effect of both Eu and Tb was hardly observed. This implies that in the intralayer, the efficiency of energy transfer is extremely low, so that highly-concentrated co-doping does not influence the luminescence and by controlling the Eu/Tb molar ratio, white light can be obtained. (2) For small , , 27 Å, the fluorescence quenching of Tb and Eu was remarkable, while for large , , 46 Å, the emission of Tb emerged and the self-quenching between Eu ions weakened. (3) The energy transfer efficiency deceased with an increase in the distance between adjacent layers. In other words, either the energy transfer between Eu and Tb or the energy migration between Eu ions was more efficient when they were located in adjacent layers than in intralayers even when they were the nearest neighbours.