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 ¹ H, ³¹ P, ²⁹ Si 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.