Optimized Synthesis and Properties of Dumbbell-Shaped NaYF₄:Yb,Tm@NaGdF₄:Eu@NH₂-MIL-53(Fe) Core-Shell Nanocomposite

Cancer theranostics urgently demands multifunctional nanomaterials capable of simultaneously enabling high-sensitivity imaging and multimodal synergistic therapy. In this study, a three-layer core-shell nanocomposite, NaYF₄:Yb,Tm@NaGdF₄:Eu@NH₂-MIL-53(Fe), was designed and synthesized. The NaYF₄:Yb,Tm nanoparticle core provides upconversion luminescence upon near-infrared (NIR) excitation and can serve as an excitation source for photodynamic therapy. An epitaxially grown NaGdF₄:Eu intermediate shell was introduced to enhance luminescence and provide T₁-weighted magnetic resonance imaging (MRI) capability. The outermost NH₂-MIL-53(Fe) metal-organic framework shell was subsequently coated to provide potential chemodynamic therapy (CDT) capability. The effects of the Eu³⁺ doping concentration, reaction temperature, reaction time, and oleic acid (OA)/1-octadecene (ODE) ratio on the anisotropic growth into a dumbbell-like morphology were examined to determine the optimal conditions. Under the optimal conditions (10 mol% Eu³⁺, 300 °C, 60 min, OA/ODE = 4:16), core-shell nanocrystals with regular morphology, uniform size, and the strongest upconversion luminescence were obtained. Polyvinylpyrrolidone (PVP)-mediated surface functionalization successfully induced the in situ growth of the NH₂-MIL-53(Fe) outer shell, thereby constructing a three-layer core-shell nanocomposite as a potential theranostic platform. Various characterizations confirmed that the resulting composite integrates upconversion luminescence, paramagnetism, and hydroxyl radical generation capability, suggesting potential for NIR-driven dual-modal imaging-guided synergistic therapy.