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TitleStructure and photoluminescent features of di-amide cross-linked alkylene-siloxane hybrids
Author(s)Nunes, Sílvia
Zea Bermudez, V. de
Cybinska, J.
Ferreira, R. A. Sá
Carlos, Luís
Silva, Maria Manuela
Smith, Michael John
Ostrovskii, David
Rocha, João
KeywordsSol-gel synthesis
Thermal stability
Issue date2005
PublisherRoyal Society of Chemistry
JournalJournal of Materials Chemistry
Citation"Journal of Materials Chemistry". ISSN 0959-9428. 15:35/36 (2005) 3876-3886.
Abstract(s)Novel amide cross-linked alkylene/siloxane hybrid materials (di-amidosils) synthesized by the sol-gel process have been investigated. Two samples identified by the notation d-A(x) with x = 4 and 8 (where x is the number of methylene groups of the alkylene chain) have been produced as transparent, amorphous, rigid monoliths, thermally stable up to about 381 and 400 ºC, respectively. In the d-A(8) hybrid the siliceous framework is composed of [(SiO)3Si(CH2)-] and [(SiO)2(HO)Si(CH2)-] substructures. Structural unit distances of 4.1 and 4.2 Å and average interparticle distances of 12 and 17 Å have been determined for d-A(4) and d-A(8), respectively. In these compounds the alkyl chains are disordered and adopt gauche conformations. While a negligible proportion of the amide linkages remain non-bonded, the great majority of these groups belong to highly disordered strong hydrogen-bonded amide-amide associations. The hybrids introduced are room temperature white light emitters, presenting an emission large, broad band in the blue/purplish-blue spectral region. The origin of such band have been ascribed to the convolution of donor-acceptor pair (D-A) recombinations that occur in the NH groups of the urea linkages and in the siliceous nanodomains. The maximum quantum yield value of the d-A(8) di-amidosil is 5.4 %.
Publisher version
AccessOpen access
Appears in Collections:CDQuim - Artigos (Papers)

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