Highly uniform Gd2O3 hollow microspheres: template-directed synthesis and luminescence properties.

Well-dispersed, uniform Gd(2)O(3) hollow microspheres have been successfully fabricated via a urea-based homogeneous precipitation method in the presence of colloidal melamine formaldehyde (MF) microspheres as templates, followed by subsequent heat treatment. The main process was carried out under aqueous conditions without any organic solvents, surfactants, or etching agents. The as-obtained Gd(2)O(3) microspheres with a spherical shape and hollow structure are uniform in size and distribution, and the thickness of the shell is about 200 nm. The lanthanide ion (Ln(3+))-doped Gd(2)O(3) hollow microspheres exhibit bright down- and upconversion luminescence with different colors coming from different activator ions under ultraviolet or 980 nm light excitation, which might find potential applications in fields such as drug delivery or biological labeling because of their excellent dispersing and luminescence properties. Furthermore, this synthesis route may be of great significance in the preparation of other hollow spherical materials.