Room-temperature fluorination of layered rare-earth hydroxide nanosheets leading to fluoride nanocrystals and elucidation of down-/up-conversion photoluminescence

摘要

In this work, we show that room-temperature fluorination of LREH-NO3- nanosheets (similar to 4 nm, RE= Y/Eu or Y/Yb/Er), directly crystallized without exfoliation, can lead to LREH-F-(anion exchange product), RE(OH)(1.57)F-1.43 hydroxyl fluoride, and the fluorolanthanates of NH4RE3F10 and NH4RE2F7 with increasing F/RE molar ratio. Unlike previous studies on nanoconversion which generally need hydrothermal treatment to drive reaction, the significant exposure of the [RE2(OH)(5)(H2O)(n)](+) main layers by the thinness of the nanosheets allows fast reaction kinetics and the products produced at room-temperature are well crystallized. Also, for down-/up-conversion photoluminescence, the REF3 nanocrystallites were obtained via facile calcination of the ammonium fluorolanthanates at 450 degrees C. The under lying mechanisms of phase conversion, the courses of structure/morphology evolution and the correlation between luminescent properties and crystal structure and chemical bonding have been unveiled. (C) 2016 Elsevier Ltd. All rights reserved.