Tri-channel photon emission of lanthanides in lithium-sublattice core-shell nanostructures for multiple anti-counterfeiting

Lithium-sublattice nanoparticles have recently shown to be a promising nano-sized host candidate for photon upconversion of lanthanides. However, it remains a challenge for the controllable synthesis of high-quality lithium-sublattice core-shell nanostructures due to its tetragonal crystal structure in contrast to the commonly investigated hexagonal (or cubic) sodium-sublattice counterparts. Herein, we present a novel synthetic strategy of using the pre-synthesized optically-active (sensitive or emissive) seeds to guide the epitaxial growth of LiGdF4-based core-shell nanostructures. By further constructing the Gd3+-mediated interfacial energy transfer in such nanoparticles, both upconverting and down-shifting emissions from a set of lanthanide ions including Eu3+, Tb3+, Dy3+, Sm3+ and Nd3+ were realized. Such core-shell nanoparticles also show good spectral Stark-splitting feature owing to their lower local structural symmetry compared to other nano-sized hosts. Moreover, the tri-channel emission from a single nanoparticle was achieved by integrating upconverting and down-shifting emissions under the dual wavelength excitations (980/254 nm), exhibiting a great promise in the multiple anti-counterfeiting identification. These results open a door to the research on new kinds of efficient luminescent nanomaterials, and further help the design of multi-functional nanostructures towards emerging cutting-edge applications.