SiO₂ Coated Up-Conversion Nanomaterial Doped with Ag Nanoparticles for Micro-CT Imaging

In this study, a new method for synthesizing Ag-NaYF₄:Yb³⁺/Er³⁺ @ SiO₂ nanocomposites was introduced. Using a hydrothermal method, the synthesized Yb³⁺- and Er³⁺-codoped NaYF₄ up-conversion luminescent materials and Ag nanoparticles were doped into up-conversion nanomaterials and coated with SiO₂ up-conversion nanomaterials. This material is known as Ag-UCNPs@SiO₂, it improves both the luminous intensity because of the doped Ag nanoparticles and has low cytotoxicity because of the SiO₂ coating. The morphology of UCNPs was observed using scanning electron microscopy (SEM), and the mapping confirmed the successful doping of Ag nanoparticles. Successful coating of SiO₂ was confirmed using transmission electron microscopy (TEM). Fluorescence spectra were used to compare changes in luminescence intensity before and after doping Ag nanoparticles. The reason for the increase in luminescence intensity after doping with Ag nanoparticles was simulated using first-principles calculations. The cytotoxicity of Ag-UCNPs@SiO₂ was tested via the cell counting kit-8 (CCK-8) method, and its imaging ability was characterized using the micro-CT method.