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.