Selective Cation Exchange Enabled Growth of Lanthanide Core/Shell Nanoparticles with Dissimilar Structure

Core/shell nanostructure is versatile for improving or integrating diverse functions, yet it is still limited to homeomorphism with isomorphic core and shell structure. Here, we delineate a selective cation exchange strategy to construct lanthanide core/shell nanoparticles with dissimilar structure. Hexagonal NaLnF 4, a typical photon conversion material, was selected to grow cubic CaF 2 shell to protect surface exposed Ln 3+ . Preferential cation exchange between Ca 2+ and Na + triggered the surface hexagonal-to-cubic structure evolution, which remediated the large barrier for heteroepitaxy of monocrystalline CaF 2 shell. The heterostructured CaF 2 shell leads to greatly enhanced upconversion emission with increased absolute quantum yield from 0.2% to 3.7%. Moreover, it is advantageous in suppressing the interfacial diffusion of Ln 3+, as well as the leakage of Ln 3+ from nanoparticle to aqueous system. These findings open up a new avenue for fabricating heterostructured core/shell nanoparticles, and are instructive for modulating various properties.