Growth of lanthanide-doped LiGdF4 nanoparticles induced by LiLuF4 core as tri-modal imaging bioprobes.

Multimodal imaging can compensate for the deficiencies and incorporate the advantages of individual imaging modalities. In this paper, we demonstrated the synthesis of core-shell nanocomposites LiLuF4@LiGdF4:Yb,Er/Tm constituted of tetragonal LiLuF4 nanoparticles as core and Yb,Er/Tm-codoped LiGdF4 as shell. LiLuF4@LiGdF4:Yb,Er/Tm nanoparticles display brighter upconversion luminescence (UCL) than NaGdF4:Yb,Er/Tm nanoparticles with the same size under continuous-wave excitation at 980 nm. The active shell layer of LiGdF4:Yb,Er/Tm not only provide the UCL center, but also serve as magnetic resonance (MR) imaging contrast agent. To further improve the UCL intensity, the inert LiGdF4 shell was coated on the LiLuF4@LiGdF4:Yb,Er/Tm nanoparticles. Furthermore, LiLuF4@LiGdF4:Yb,Tm@LiGdF4 nanoparticles have been successfully applied to UCL/X-ray computed tomography (CT)/MR tri-modal imaging on the modal of tumor-bearing mice.