Highly Photostable Luminescent Poly(implied by-caprolactone)siloxane Biohybrids Doped with Europium Complexes

摘要

In this paper, we propose for the first time that the combination of a sol-gel derived diurethane cross-linked siloxane-based biohybrid host including short poly(implied by-caprolactone) segments (PCL(530)) and lanthanide aquocomplexes incorporating beta-diketonate ligands yields an effective protecting cage that efficiently encapsulates the emitting centers and reduces luminescence quenching. The results obtained using the Eu(tta)_3(H2O)_2 (where tta~ is 2-thenoyltrifluoracetonate) complex demonstrate that 1 (2) carbonyl oxygen atoms of the host matrix enter the Eu~(3+) coordination shell, thus replacing the labile water molecule-(s). The significant increase in the quantum efficiency q of the doped hybrid with respect to that of Eu(tta)_3(H2O)_2 (44.2 versus 29.0%, respectively) reveals that complex anchoring to the PCL(530)-based host structure contributes to enhancement of the ~5Do quantum efficiency. However, when a complex that contains only strong chelating ligands, such as Eu(tta)_3phen (where phen is 1,10-phenantroline), is incorporated into the same host medium, the effect is lost and the ~5Do nonradiative paths in the doped hybrid are higher than those existing in the complex itself. Under UVA exposure, the emission intensity of PCL(530)/siloxane/Eu(tta)_3(H2O)_2 decreased 10% in 11 h, whereas that of PCL(530)/siloxane/Eu-(tta)_3phen decreased 25% in the same period of time.