Uniform Gd-Based Coordination Polymer Hollow Spheres: Synthesis, Formation Mechanism and Upconversion Properties

In this work, Gd-based coordination polymer (GdCP) hollow spheres have been synthesized by a general, facile and template-free solvothermal strategy. The products were well characterized and analyzed. Results indicate that the uniform hollow nanospheres have diameters of 160–260 nm. Influential factors such as reaction temperature, time, and dosage of reagents on the morphology and size of the GdCP hollow spheres have been systematically investigated. An Ostwald ripening mechanism coupled with a self-assembly process for the hollow structures formation was proposed based on a series of time-dependent experiments. Furthermore, after doping with Yb3+/Er3+ ions, characteristic red upconversion emission from 4F9/2→4I1 5/2 of Er3+ was realized under 980 nm NIR irradiation.