Near-Infrared Luminescence from Sol−Gel Materials Doped with Holmium(III) and Thulium(III) Complexes

A series of ternary Ln(tta) 3 L complexes (Ln = Ho, Tm; Htta = 2-thenoyltrifluoroacetone; L = 1,10-phenanthroline, 2,2′-bipyridine, or triphenyl phosphate oxide) and their corresponding sol−gel hybrid materials formed via the in situ synthesis process (designated as Ln-T-L gel) were reported. The complexes and the gels were studied in detail, which suggest the complexes have been successfully synthesized in the corresponding gels. After excitation at the maximum absorption of the ligands, the complexes and the gels all show the characteristic near-infrared (NIR) luminescence of the corresponding Ln 3+ ions, which is due to efficient energy transfer from the ligands to the central Ln 3+ ions via an antenna effect. The radiative properties of the Ho 3+ ion in the Ho-T-B gel are discussed by Judd-Ofelt analysis, indicating that the 5 F 5 → 5 I 6 transition of the Ho 3+ ion in the Ho-T-B gel could be a possible candidate for optoelectronics.