Zirconium metal organic framework for design of tetragonal rare earth-doped zirconia nanoparticles

Zirconium metal–organic frameworks ZrOBDC (where BDC = C₆H₄(COOH)₂, terephthalic acid) doped and co-doped with rare earth ions Ln (ZrOBDC:Ln³⁺, where Ln³⁺ = Eu³⁺ and Tb³⁺ as well as Er³⁺ and Yb³⁺) were used as precursors for the design of tetragonal rare earth doped zirconia nanoparticles (t-ZrO₂:Ln³⁺ NPs) through annealing process. Preparation, characterization and luminescence properties of ZrOBDC:Ln³⁺ and ZrO₂:Ln³⁺ NPs were investigated. The as-obtained t-ZrO₂:Ln³⁺ NPs have high purity with an average size of 20–30 nm. The luminescence spectra of ZrOBDC:Tb³⁺ and ZrOBDC:Eu³⁺ display strong green and red emission at around 544 and 611 nm which correspond to ⁵D₄ → ⁷F₅ and ⁵D₀ → ⁷F₂ transitions of Tb³⁺ and Eu³⁺ ions, respectively. The green and red up-conversion emissions of ZrO₂:Er³⁺,Yb³⁺ NPs due to ²H_11/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions of the Er³⁺ ions are observed under 976 nm laser excitation.