Hydrothermal Targeted‐Explosion Synthesis of Hollow/Porous Upconversion Nano‐ and Microcrystals with Potential for Luminescent Displays and Biological Imaging

Abstract A facile, one‐pot, hydrothermal ‘targeted‐explosion’ strategy was developed to construct β‐NaGdF₄ and β‐NaYF₄ hollow/porous upconversion nano‐ and microcrystals. We found that potassium sodium tartrate (PST) strongly complexes rare earth ions, which can reduce the reaction speed between rare earth ions and fluorine ions, leading to size‐ and morphology‐controlled crystals in a hydrothermal synthesis. Moreover, we simulated the ‘targeted‐explosion’ reaction process through structural mechanics finite element calculations to validate the feasibility of a ‘layer‐by‐layer blasting’ mechanism. Finally, we fabricated various models to show the potential of these materials for luminescent displays and as rare earth illuminants excited by near‐infrared light. In addition, the synthesized hollow/porous upconversion crystals were used for different types of biological imaging.