Controlled synthesis and upconversion luminescence properties of Yb~(3+)/ Er~(3+) co-doped Bi_2O_3 nanospheres for optical and X-ray computed tomography imaging

摘要

Bi2O3 nanospheres co-doped with Yb3+/Er3+ upconverting ions pair have been successfully synthesized via a facile hydrothermal method followed by a heat treatment. The resulting Bi2O3:Yb3+, Er3+ nanospheres show a monodisperse spherical morphology with narrow size distribution (similar to 180 nm) and display intense upconversion luminescence under 980 nm laser excitation. It is found that the crystal structure, morphology and upconversion luminescence properties of nanospheres have a direct relationship with the doping concentration of Yb3+ and the subsequent calcination temperature. These Bi2O3:Yb3+, Er3+ nanospheres can be prepared in large quantities and can be easily modified with a layer of biocompatible polyethyleneimine (PEI) molecules. The yielded nanospheres could not only maintain uniform size and morphological characteristics, but also show good water dispersibility and biocompatibility. Remarkably, these Bi2O3:Yb3+, Er3+ upconversion nanophosphors could also act as an effective contrast agent for X-ray computed tomography (CT) imaging, which show higher contrast efficacy than commercial iodine-based contrast agent. The proposed facile synthetic mute and inexpensive matrix materials pave the way for broad use of these Bi2O3:Yb3+, Er3+ nanospheres as ideal dual-mode bioimaging probes in biomedical field.