Synthesis and Characterization of Y₂O₃:Er³⁺ Upconversion Materials with Nanoporous Structures

Y₂O₃:Er³⁺ upconversion materials with nanoporous structures were prepared by a hydrothermal method following a post-thermal treatment. The structure and morphology of the materials were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results indicated that the as-obtained Y₂O₃:Er³⁺ powders were of cubic-phase structure, and the nanoporous structure was formed in the annealing process. The optical results indicated that high annealing temperature could improve the upconversion properties, but it could destroy the nanoporous structure. Under 980 nm excitation, red (⁴F_9/2 → ⁴I_15/2) and green (²H_11/2, ⁴S_3/2 → ⁴I_15/2) upconversion luminescence was observed. The studies on the intensity dependence of upconversion emission indicated that two-photon processes were responsible for the green and red upconversion luminescence. This kind of multifunctional material has potential applications in nanocontainers for use as biomolecule and drugs carriers.