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Titolo:
Structure and luminescence of Eu3+-doped class I siloxane-poly(ethylene glycol) hybrids
Autore:
Molina, C; Dahmouche, K; Santilli, CV; Craievich, AF; Ribeiro, SJL;
Indirizzi:
UNESP, Inst Chem, BR-14801970 Araraquara, SP, Brazil UNESP Araraquara SP Brazil BR-14801970 BC-14801970 Araraquara, SP, Brazil USP, Inst Phys, BR-09500900 Sao Paulo, Brazil USP Sao Paulo Brazil BR-09500900 BCt Phys, BR-09500900 Sao Paulo, Brazil
Titolo Testata:
CHEMISTRY OF MATERIALS
fascicolo: 9, volume: 13, anno: 2001,
pagine: 2818 - 2823
SICI:
0897-4756(200109)13:9<2818:SALOEC>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
ORGANICALLY MODIFIED SILICATES; LIGHT EMISSION; SCATTERING; MATRICES; XEROGELS; SYSTEMS; EU3+;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Engineering, Computing & Technology
Citazioni:
27
Recensione:
Indirizzi per estratti:
Indirizzo: Ribeiro, SJL UNESP, Inst Chem, POB 355, BR-14801970 Araraquara, SP, BrazilUNESP POB 355 Araraquara SP Brazil BR-14801970 BC, SP, Brazil
Citazione:
C. Molina et al., "Structure and luminescence of Eu3+-doped class I siloxane-poly(ethylene glycol) hybrids", CHEM MATER, 13(9), 2001, pp. 2818-2823

Abstract

Transparent, flexible, and luminescent EU3+-doped siloxane-poly(ethylene glycol) (PEG) nanocomposites have been obtained by the sol-gel process. The inorganic (siloxane) and organic PEG phases are usually linked by weak bonds (hydrogen bonds or van der Waals forces), and small-angle X-ray scattering (SAXS) measurements suggest that the structure of these materials consists of fractal siloxane aggregates embedded in the PEG matrix. For low Eu3+ contents, n = 300 and n = 80, the aggregates are small and isolated and their fractal dimensions are 2.1 and 1.7, respectively. These values are close to those expected for gelation mechanisms consisting of reaction-limited cluster-cluster aggregation (RLCCA) and diffusion-limited cluster-cluster aggregation (DLCCA). For high Eu3+ content, SAYS results are consistent with atwo-level structure: a primary level of siloxane aggregates and a second level, much larger, formed by the coalescence of the primary ones. The observed increase in the glass transition temperature for increasing Eu3+ content is consistent with the structural model derived from SAXS measurements. Extended X-ray absorption fine structure (EXAFS) and luminescence spectroscopy measurements indicate that under the experimental conditions utilized here Eu3+ ions do not strongly interact with the polymeric phase.

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Documento generato il 26/09/17 alle ore 09:25:39