resumo
An organic molecule, (EtO)(3)Si(CH(2))(3)NH(C =O) NH-(CH(2))(12) - NH(C = O) NH(CH(2))(3)Si(OEt)(3), combining urea functionalities and a 12-carbon alkyl chain, underwent sol - gel reactions in the presence of an acid catalyst, a large excess of water and variable amounts of EuCl(3), giving rise to the formation of crystalline hybrids through a self- directed organization process in which hydrogen bonding interactions play a key role. Three photoluminescent lamellar Eu(3+)- doped silsesquioxane hybrids incorporating 1.01, 1.83 and 15.04% Eu(3+) were prepared and fully characterized. The lamellar hybrids are room temperature multi-wavelength emitters due to the convolution of the hybrid's emitting centres and the Eu(3+) intra- 4f(6) transitions. Their emission colour can be easily tuned along the Commission Internationale d'Eclairage chromaticity diagram from the bluish- purple region to the pink area, either by changing the excitation wavelength or the Eu(3+) amount. The Eu(3+) first coordination shell is very similar for the three photoluminescent lamellar Eu3+- doped silsesquioxane hybrids incorporating oxygen atoms of the carbonyl group, Cl atoms and water molecules, despite the minor variations found in the (5)D(0) quantum efficiency ( 16.3 - 19.2), number of water molecules ( 1.7 - 2.0) and experimental intensity Omega(2) parameter (8.9 - 10.1 x 10(-20) cm(2)) with the increase of Eu(3+) content.
palavras-chave
ORGANIC-INORGANIC HYBRIDS; BETA-DIKETONATE COMPLEX; CARBOXYLIC-ACID SOLVOLYSIS; FULL-COLOR PHOSPHORS; LONG ALKYLENE CHAINS; WHITE-LIGHT EMISSION; X-RAY-DIFFRACTION; SOLID-STATE NMR; THIN-FILMS; LUMINESCENCE PROPERTIES
categoria
Chemistry; Materials Science
autores
Nobre, SS; Brites, CDS; Ferreira, RAS; Bermudez, VD; Carcel, C; Moreau, JJE; Rocha, J; Man, MWC; Carlos, LD
nossos autores
Carlos Brites
Professor associado
João Rocha
Prof. Catedrático
Luís Carlos
Professor Catedrático
Maria Rute de Amorim e Sá Ferreira André
Professor Catedráticoagradecimentos
The support of NoE FAME, Fundacao para a Ciencia e Tecnologia (FCT) (POCI/V. 5/A0067/2005) and FEDER is gratefully acknowledged. The authors would like to thank the collaboration of AG Macedo, Aveiro University, in the AFM measurements and Bruno Caetano and C. Santilli, UNESP, Brazil, during SAXS measurements. S. S. Nobre and C. D. S. Brites thank FCT grants (SFRH/BD/28739/06 and 38472/07, respectively).