Biocompatible sphere, square prism and hexagonal rod Gd₂O₃:Eu³⁺@SiO₂ nanoparticles: The effect of morphology on...

The cubic structure Gd₂O₃:Eu³⁺@SiO₂ particles with homogeneous multiform morphologies (pH 6: sphere, pH 10: square prism and pH 12: hexagonal rod) were prepared by pH modifiers: nitric acid- and ammonium hydroxide-assisted solvothermal reaction. The effect of synthesis conditions (reaction time and pH value) on the morphology and the particle growth mechanisms were researched. The photoluminescence (PL), magnetic resonance imaging (MRI) and X-ray computed tomography (CT) studies of Gd₂O₃:Eu³⁺@SiO₂ showed strong dependence on the morphology alteration. The longitudinal relaxivity value of Gd₂O₃:Eu³⁺@SiO₂ was 10.24 (pH 6), 14.52 (pH 10) and 25.68 (pH 12) s^-1 mM^-1 at 3 T, which is equivalent to 2.4, 3.8 and 6.2 times higher than to the Dotarem (commercial clinical MRI contrast agent). Furthermore, the Gd₂O₃:Eu³⁺@SiO₂ with different pH values (6, 10 and 12) has the good biocompatibility. This study provides the useful multifunctional contrast agents based on multiform Gd₂O₃:Eu³⁺@SiO₂ particles.