Structural and luminescent studies of erbium-doped CaZrO3 green-emitting nanophosphors

New near-infrared emissions and energy transfer in Er3+ -doped MgAl layered double hydroxides

A series of Er³⁺ -doped magnesium aluminium layered double hydroxides (Er³⁺ -doped, MgAl-LDHs) with different Mg²⁺ /(Al³⁺ +Er³⁺ ) molar ratios were synthesized using the hydrothermal method. Compositional and structural analyses suggest that the Er³⁺ -doped MgAl-LDHs kept a hexagonal structure while the Mg²⁺ /(Al³⁺ +Er³⁺ ) molar ratio was at 1.0-4.1. The downconverted emission spectra of the Er³⁺ -doped MgAl-LDHs showed a red emission at 650 nm and strong infrared emissions at 720, 780, and 850 nm. These infrared emissions were hardly observed in previous downconverted emission spectra of Er³⁺ -doped materials. In the analysis of the Er³⁺ energy levels and in relevant published literature, the energy transfer diagram for Er³⁺ -doped in MgAl-LDHs is described, and infrared emissions at 720, 780, and 850 nm may be attributed to ⁴ F_7/2 →⁴ I_13/2 , ² H_11/2 →⁴ I_13/2 , and ⁴ S_3/2 →⁴ I_13/2 transitions of Er³⁺ , respectively. Er³⁺ -doped MgAl-LDHs could have potential application as marking and targeting agents in the processes for drug delivery in consideration of the strong near-infrared Er³⁺ emissions, as well as the special layered structure of MgAl-LDH.