Structural, optical and X-ray attenuation properties of Tb3+:BaXCe1-xF3-x (x = 0.18-0.48) nanospheres synthesized in polyol medium

Abstract

Uniform BaCeF nanospheres have been obtained after aging a solution of barium and cerium nitrates and sodium tetrafluoroborate in a mixture of ethylene glycol and water at 120 °C for 20 hours. The diameter of the spheres could be tailored from 65 nm to 80 nm by varying the NaBF concentration while maintaining their colloidal stability in aqueous suspension. Increasing the aging temperature led to a phase transformation from hexagonal to cubic symmetry and to a concomitant increase of the Ba/Ce ratio, which reached a value close to the nominal one (50/50) at 240 °C. The same method was successful in obtaining Tb-doped nanospheres with homogeneous cation distribution and the same morphological features as the undoped material. An intense green emission was observed after the excitation of the Tb-doped samples through the Ce-Tb energy transfer (ET) band. The ET efficiency increased with increasing Tb content, the maximum emission being observed for the 10% Tb-doped nanospheres. Aqueous suspensions of the latter sample showed excellent X-ray attenuation values that were superior to those of an iodine-based clinically approved contrast agent. Their fluorescence and X-ray attenuation properties make this material a potential dual bioprobe for luminescence bioimaging and X-ray computed tomography.