Facile Fabrication of Rare-Earth-Doped Gd2O3 Hollow Spheres with Upconversion Luminescence, Magnetic Resonance, and Drug Delivery Properties

Abstract

Rare-earth (RE)-doped gadolinium oxide (Gd 2 O 3 ) hollow nanospheres have been successfully prepared on a large scale via a template-directed method using hydrothermal carbon spheres as sacrificed templates. Scanning electron microscope and transmission electron microscope images reveal that these hollow-structured nanospheres have the mesoporous shells that are composed of a large amount of uniform nanoparticles. By doping the RE ions (Yb/Er) into the Gd 2 O 3 host matrix, these NPs emitted bright multicolored upconversion emissions that can be fine-tuned from green to red by adjusting the codoped Yb/Er ratio under 980 nm NIR laser excitation. The possibility of using these upconversion nanoparticles for optical imaging in vivo has been demonstrated. It was also shown that these Gd 2 O 3 nanospheres brightened the T 1 -weighted images and enhanced the r 1 relaxivity of water protons, which suggested that they could act as T 1 contrast agents for magnetic resonance (MR) imaging. Moreover, these hollow spheres can be used as drug delivery host carriers, and drug storage/release properties were investigated using ibuprofen as the model drug. As a result, the so-prepared nanoscaled Gd 2 O 3 hollow spheres bearing upconversion luminescence, MR imaging, and drug delivery capabilities could be potentially employed for simultaneous MR/fluorescent imaging and therapeutic applications.