New near-infrared emissions and energy transfer in Er -doped MgAl layered double hydroxides.

A series of Er -doped magnesium aluminium layered double hydroxides (Er -doped, MgAl-LDHs) with different Mg /(Al +Er ) molar ratios were synthesized using the hydrothermal method. Compositional and structural analyses suggest that the Er -doped MgAl-LDHs kept a hexagonal structure while the Mg /(Al +Er ) molar ratio was at 1.0-4.1. The downconverted emission spectra of the Er -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 -doped materials. In the analysis of the Er energy levels and in relevant published literature, the energy transfer diagram for Er -doped in MgAl-LDHs is described, and infrared emissions at 720, 780, and 850 nm may be attributed to F → I , H → I , and S → I transitions of Er , respectively. Er -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 emissions, as well as the special layered structure of MgAl-LDH.