Synthesis, characterization and up-conversion luminescence properties of α -NaYF4:Yb3+/Er3+/PVP/MOFs multilayer nanocrystals

Abstract

The precursor PVP-capped α -NaYF₄:Yb³⁺/Er³⁺ nanospheres were used as the templates for preparing the α -NaYF₄:Yb³⁺/Er³⁺/PVP/MOFs multilayer nanocrystals with a self-template method. By using iron (III) carboxylate and zeolitic imidazolate frameworks dissolved in dimethylformamide (DMF) solution containing 25% of diethylene glycol (DEG), the sphericalshaped α -NaYF4:Yb³⁺/Er³⁺/PVP/MIL-100 and α -NaYF₄:Yb³⁺/Er³⁺/PVP/ ZIF-8 multilayer nanocrystals were successfully prepared with the sizes of 300-500 nm at 100oC for one hour. Under a 976 nm laser excitation at room temperature, the α -NaYF₄:Yb³⁺/Er³⁺/PVP/MIL-100 and α-NaYF₄:Yb³⁺/ Er³⁺/PVP/ZIF-8 multilayer nanocrystals exhibited strong up-conversion luminescence with three emission bands centered at around 520 nm, 540 nm, and 655 nm corresponding to ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 transitions of Er³⁺ ions, respectively.