resumo
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(epsilon-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)(H(2)O)(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)(H(2)O)(2) (44.2 versus 29.0%, respectively) reveals that complex anchoring to the PCL(530)-based host structure contributes to enhancement of the (5)D(0) quantum efficiency. However, when a complex that contains only strong chelating ligands, such as Eu(tta)(3)phen (where phen is 1,10-phenantroline), is incorporated into the same host medium, the effect is lost and the (5)D(0) 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)(H(2)O)(2) decreased 10% in 11 h, whereas that of PCL(530)/siloxane/Eu(tta)(3)phen decreased 25% in the same period of time.
palavras-chave
ORGANIC-INORGANIC NANOCOMPOSITES; FUNCTIONALIZED ORGANIC/INORGANIC HYBRIDS; CARBOXYLIC-ACID SOLVOLYSIS; BETA-DIKETONATE COMPLEX; FULL-COLOR PHOSPHORS; GEL-DERIVED SILICA; EMISSION RED-SHIFT; IN-SITU; EU3+ IONS; TRIS(2-THENOYLTRIFLUOROACETONATO)LANTHANIDE(III) COMPLEXES
categoria
Chemistry; Materials Science
autores
Fernandes, M; Bermudez, VD; Ferreira, RAS; Carlos, LD; Charas, A; Morgado, J; Silva, MM; Smith, MJ
nossos autores
Luís Carlos
Professor Catedrático