A series of Er 3+-doped magnesium aluminium layered double hydroxides (Er 3+-doped, MgAl-LDHs) with different Mg 2+ /(Al 3+ +Er 3+) molar ratios were synthesized using the hydrothermal method. Compositional and structural analyses suggest that the Er 3 +-doped MgAl-LDHs kept a hexagonal structure while the Mg 2+ /(Al 3+ +Er 3+) molar ratio was at 1.0-4.1. The downconverted emission spectra of the Er 3+-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 Er 3+-doped materials. In the analysis of the Er 3+ energy levels and in relevant published literature, the energy transfer diagram for Er 3+-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 Er 3+ , respectively. Er 3+-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 Er 3+ emissions, as well as the special layered structure of MgAl-LDH.

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