abstract
Organic-inorganic hybrids incorporating Eu(TPI)(3)center dot 3H(2)O or Eu(TPI)(3)center dot 2TOPO [where TPI and TOPO stand for 3-phenyl4-(4-toluoyl)-5-isoxazolone and tri-n-octylphosphane oxide, respectively] were synthesized either by acetic acid solvolysis or a conventional hydrolysis sol-gel route. The host framework of these materials, named as di-ureasil, consists of a siliceous skeleton grafted, through urea cross-linkages, to both ends of poly(ethylene oxide) chains. The resulting Eu3+-based di-ureasils were characterized by X-ray diffraction and Fourier transform mid-IR, Si-29 and C-13 NMR, and photoluminescence spectroscopy. The room-temperature photoluminescence (PL) spectra of the Eu3+-based di-ureasils display the typical Eu3+ red emission, assigned to transitions between the first excited state (D-5(0)) and the ground multiplet (F-7(0-4)). Enhanced D-5(0) quantum efficiency (eta = 13 % vs. 32 %) and a longer lifetime (tau = 0.30 vs. 0.42 ms) was noticed for the hybrid incorporating the Eu(TPI)(3)center dot 3H(2)O complex, compared with the undoped complex. The enhancement is explained by the coordination ability of the organic counter part of the host structure, which is strong enough to displace the water molecules of the Eu(TPI)(3)center dot 3H(2)O complex from the Eu3+ neighborhood in the hybrids. On the other hand, a decrease in the 5 Do quantum efficiency (eta = 76 % vs. 61 %) and lifetime (tau = 0.98 vs. 0.75 ms) was noticed for the hybrid incorporating the Eu(TPI)(3)center dot 2TOPO complex, relative to the undoped complex, probably because of an increase in the nonradiative transition probability.
keywords
FUNCTIONALIZED ORGANIC/INORGANIC HYBRIDS; CARBOXYLIC-ACID SOLVOLYSIS; WHITE-LIGHT EMISSION; FULL-COLOR PHOSPHORS; MODIFIED SILICATES; COMPLEXES; IONS; UREA; PHOTOLUMINESCENCE; NANOHYBRIDS
subject category
Chemistry
authors
Lima, PP; Junior, SA; Malta, OL; Carlos, LD; Ferreira, RAS; Pavithran, R; Reddy, MLP
our authors
Luís Carlos
Full professor
Maria Rute de Amorim e Sá Ferreira André
Full professor