Dual Phase‐Controlled Synthesis of Uniform Lanthanide‐Doped NaGdF₄ Upconversion Nanocrystals Via an OA/Ionic Liquid Two‐Phase System for In Vivo Dual‐Modality Imaging

Abstract

Abstract A novel OA/ionic liquid two‐phase system combining the merits of thermal decomposition method, the IL‐based strategy, and the two‐phase approach is introduced to synthesize high‐quality lanthanide‐doped NaGdF 4 upconversion nanocrystals with different crystal‐phases in OA‐phase and IL‐phase through a one‐step controllable reaction. Oil‐dispersible cubic‐phase NaGdF 4 :Yb, Er (Ho, Tm) nanocrystals with ultra‐small size (∼5 nm) and monodispersity are obtained in the OA phase of the two‐phase system via an IL‐based reaction. More importantly, water‐soluble hexagonal‐phase NaGdF 4 :Yb, Er nanocrystals are obtained in the same system simply by adopting an extremely facile method to complete the dual phase‐transition (crystal‐phase transition and OA‐phase to IL‐phase transition) simultaneously. The synthesized lanthanide‐doped NaGdF 4 upconversion nanocrystals are effective for dual‐mode UCL imaging and CT imaging in vivo.