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

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.