Cation exchange in lanthanide fluoride nanoparticles

摘要

Cation exchange in lanthanide fluoride nanoparticles is reported. Typically, dispersible LnF_3 nanoparticles were exposed to another lanthanide ion that was roughly 5 times the amount of Ln~(3+) in the nanoparticles. Results show that cation exchange of GdF_3 nanoparticles with La~(3+) was almost complete in 1 min, and it also happens reversibly although the degree of exchange is not as much as the forward reaction. However, cation exchange with lanthanide ions close to each other, such as GdF_3 with Eu~(3+) and NdF_3 with La ~(3+), did not end up with nearly full exchange, but with a significant amount of the two lanthanides. A relatively small driving force for the cation exchange is suggested by the experimental results, which is also confirmed by calculations based on a thermodynamic cycle. This unprecedented finding in the field of lanthanide-based nanoparticles raises the question whether reported core-shell structures were indeed made and, at the same time, it opens up new pathways to make nanomaterials that cannot be made directly.