Spherical Gd₃TaO₇ Particles with Phase-Stabilized Structure for Multimodal Bioimaging Application

We report the polyol-mediated synthesis of spherical Gd3TaO7 particles with controlled morphology, phase purity, and luminescence, engineered as trimodal nanoprobes for bioimaging. The method yields monodisperse particles (∼170 nm) that retain their spherical morphology even after high-temperature annealing at 800 and 1000 °C, overcoming the morphological instability and aggregation typically observed in tantalate-based systems. Structural characterization confirms the stabilization of the disordered cubic fluorite-related phase, with Eu3+ ions acting as structural and luminescent probes. The doped particles exhibit broad-band red emission and long-lived excited states, suitable for optical detection. Notably, luminescence is significantly enhanced via postsynthetic coordination with 2-thenoyltrifluoroacetone (TTA), enabling clear intracellular visualization through confocal microscopy. In parallel, undoped Gd3TaO7 particles show excellent performance as T2-weighted MRI contrast agents (r2 = 71.5 mM–1 s–1 at 7 T) and demonstrate strong X-ray attenuation for CT imaging, attributed to the presence of Gd and Ta high-Z elements. Confocal imaging confirms cellular uptake, while cytotoxicity assays in NIH-3T3 mouse fibroblasts demonstrate over 95% viability up to 1000 μg/mL, attesting to their biocompatibility. This work establishes Gd3TaO7 -based nanoprobes as robust, compositionally engineered candidates for integrated MRI, CT, and optical imaging, with enhanced luminescence achievable via TTA sensitization for advanced bioimaging applications.