Hybrid Eu-III Coordination Luminophore Standing on Two Legs on Silica Nanoparticles for Enhanced Luminescence

In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent Ln(III)-silica nanomaterials. A novel Eu-III-silica hybrid nanoparticle was developed by using a doubly binding TPPO-Si(OEt)(3) (TPPO: triphenyl phosphine oxide) linker. The TPPO-Si(OEt)(3) was confirmed by H-1, P-31, Si-29 NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)(3) and Eu(tfc)(3) moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO-Si(OEt)(3)-modified silica nanoparticles, producing Eu(hfa)(3)(TPPO-Si)(2)-SiO2 and Eu(tfc)(3)(TPPO-Si)(2)-SiO2, respectively. Eu(hfa)(3)(TPPO-Si)(2)-SiO2 exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported Eu-III-based hybrid materials. Eu(tfc)(3)(TPPO-Si)(2)-SiO2 showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)(3)(TPPO-Si(OEt)(3))(2) was found to be 39 %. These results confirmed that the TPPO-Si(OEt)(3) linker is a promising candidate for development of Eu-III-based luminescent materials

Effective Photosensitization in Excited-State Equilibrium: Brilliant Luminescence of Tb-III Coordination Polymers Through Ancillary Ligand Modifications

Molecular photosensitizers provide efficient light-absorbing abilities for photo-functional materials. Herein, effective photosensitization in excited-state equilibrium is demonstrated using five Tb-III coordination polymers. The coordination polymers are composed of Tb-III ions (emission center), hexafluoroacetylacetonato (photosensitizer ligands), and phosphine oxide-based bridges (ancillary ligands). The two types of ligand combinations induces a rigid coordination structure via intermolecular interactions, resulting in high thermal stability (with decomposition temperatures above 300 degrees C). Excited-triplet-state lifetimes of photosensitizer ligands (tau=120-1320 mu s) are strongly dependent on the structure of the ancillary ligands. The photosensitizer with a long excited-triplet-state lifetime (tau >= 1120 mu s) controls the excited state equilibrium between the photosensitizer and Tb-III, allowing the construction of Tb-III coordination polymer with high Tb-III emission quantum yield (>= 70 %)