Core-shell structured GdO:Ln@mSiO hollow nanospheres: synthesis, photoluminescence and drug release properties.

GdO:Ln@mSiO hollow nanospheres (GdO:Ln hollow spheres coated by a mesoporous silica layer) were successfully synthesized through a self-template method using Gd(OH)CO as template to form hollow precursors (named HPs), which involved the incorporation of the rare earth compound into the interior of the hydrophilic carbon shell, followed by coating with a mesoporous silica shell, and subsequent calcination in air. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA), photoluminescence spectroscopy, kinetic decays as well as N adsorption/desorption were employed to characterize the composites. The results indicate that the uniform GdO:Ln@mSiO composite with the particle size around 300 nm maintains the spherical morphology and good dispersibility of the precursor. Interestingly, the composite has a double-shell structure including an inner shell of GdO and an outer shell of mesoporous silica. Moreover, they also exhibit bright red (Eu, D→F) down-conversion (DC) emission and characteristic up-conversion (UC) emissions of Yb/Er. Under beam excitation, the hollow structured sample emits, which should have potential applications in biomedicine and other fields.