Eu3+-Assisted Short-Range Ordering of Photoluminescent Bridged Silsesquioxanes
authors Nobre, SS; Cattoen, X; Ferreira, RAS; Carcel, C; Bermudez, VD; Man, MWC; Carlos, LD
nationality International
journal CHEMISTRY OF MATERIALS
keywords ORGANIC-INORGANIC HYBRIDS; EMISSION QUANTUM YIELDS; FULL-COLOR PHOSPHORS; SOL-GEL PROCESS; ENERGY-TRANSFER; LANTHANIDE COMPOUNDS; BETA-DIKETONE; SILICA; DESIGN; NANOCOMPOSITES
abstract The bridged silsesquioxane precursor (EtO)(3)Si(CH2)(3)NH(C=O)NH-(CH2)(12)-N1-1(C=O)NH-(CH2)(3) Si(OEt)(3), combining polymerizable silylated groups, urea functionalities, and alkyl chains, undergoes fluoride (F-)-catalyzed sol-gel reactions in the presence or absence of EuCl3 center dot 6H(2)O. Supramolecular self-assembly of the growing structure relies primarily on the establishment of strong and ordered hydrogen bonding interactions. In the case of the Eu3+-containing hybrids the lanthanide ions play a totally unparallel dual-role acting simultaneously as structure directing agents and structural probes to sense locally morphological alterations. In the early stages of the synthesis, while a fraction of the Eu3+ ions promotes the formation of a unidirectional urea-urea hydrogen-bonded array, the remaining ions coordinate to silanol (Si-OH) groups inhibiting the growth of the siloxane network and yielding small anisotropic flakes (similar to 200 rim lone). These are subsequently assembled on the micrometer scale in a brick-like tile-to-tile arrangement that ends up with the formation of fibers or twisted bundles (3.0-4.0 mu m long and 0.5-1.0 mu m wide). At higher Eu3+ concentrations, Eu3+-based ionic interfiber cross-links hinder the solvent flow and force adjacent fibers to adopt a bow-tie form (3.0-4.0 mu m long and 3.0 mu m wide at the tips). The hybrids are room temperature multiwavelength emitters because of the convolution of the hybrids' intrinsic emission and the Eu3+ intra-4f(6) transitions. The photoluminescence features (D-5(0)-> F-7(0) energy, D-5(0) quantum efficiency, number of coordinated water molecules, and experimental intensity parameters) as a function of the Eu3+ content and acidic- and F--catalyzed conditions used in the synthesis are compared to address the effect of the morphology in the photoluminescence features of the hybrid materials.
publisher AMER CHEMICAL SOC
issn 0897-4756
year published 2010
volume 22
issue 12
beginning page 3599
ending page 3609
digital object identifier (doi) 10.1021/cm1009042
web of science category Chemistry, Physical; Materials Science, Multidisciplinary
subject category Chemistry; Materials Science
unique article identifier WOS:000278684000006
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