Performance of near-IR luminescent xerogel materials covalently bonded with ternary lanthanide (ErIII, NdIII, YbIII) complexes

A series of near-infrared (NIR) luminescent ternary lanthanide (Ln = Er, Nd, Yb) complexes covalently linked to xerogels by a chelate ligand 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline (phen-Si) were synthesized in situ via a sol–gel method. The obtained xerogel materials (named xerogel-bonded Ln complex) are rigid, and appear homogeneous confirmed by SEM images. Upon excitation at the maximum absorption wavelength of the ligands, all these xerogel materials with different lanthanide complex concentration show the characteristic NIR luminescence of the corresponding lanthanide ion, as a result of the efficient energy transfer from the ligands to the lanthanide ion. For the xerogel-bonded Er complex, the full width at half maximum (FWHM) of the 4I13/2 → 4I15/2 transition is 76 nm, which enables a wide gain bandwidth for the optical amplification. Based on the Judd–Ofelt theory, the radiative properties of the xerogel-bonded Nd complex (with Nd/Si molar ratio of 1/11 in the reaction) were studied.