Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Coordination of Eu3+ ions in siliceous nanohybrids containing short polyether chains and bridging urea cross-links
Autore:
Bermudez, VD; Ferreira, RAS; Carlos, LD; Molina, C; Dahmouche, K; Ribeiro, SJL;
Indirizzi:
Univ Tras Os Montes & Alto Douro, Dept Quim, P-5001911 Vila Real, PortugalUniv Tras Os Montes & Alto Douro Vila Real Portugal P-5001911 , Portugal Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal Univ Aveiro Aveiro Portugal P-3810193 pt Fis, P-3810193 Aveiro, Portugal UNESP, Inst Quim, BR-14801970 Sao Paulo, Brazil UNESP Sao Paulo Brazil BR-14801970 BCQuim, BR-14801970 Sao Paulo, Brazil
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 17, volume: 105, anno: 2001,
pagine: 3378 - 3386
SICI:
1520-6106(20010503)105:17<3378:COEIIS>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
ORGANICALLY MODIFIED SILICATES; EARTH-METAL SALTS; INFRARED TEMPERATURE; LITHIUM PERCHLORATE; SPECTROSCOPIC ANALYSIS; POLYMER ELECTROLYTES; PROPYLENE CARBONATE; MODEL POLYURETHANES; LIGHT EMISSION; URETHANE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
86
Recensione:
Indirizzi per estratti:
Indirizzo: Bermudez, VD Univ Tras Os Montes & Alto Douro, Dept Quim, Apartado 202, P-5001911 Vila Real, Portugal Univ Tras Os Montes & Alto Douro Apartado 202 Vila Real Portugal P-5001911
Citazione:
V.D. Bermudez et al., "Coordination of Eu3+ ions in siliceous nanohybrids containing short polyether chains and bridging urea cross-links", J PHYS CH B, 105(17), 2001, pp. 3378-3386

Abstract

Infrared and photoluminescence spectroscopies have been used to investigate the local environment of the Eu3+ ions in luminescent sol-gel derived materials-di-ureasils-based on a hybrid framework represented by U(600). This host is composed of a siliceous backbone grafted, through urea cross-links,to both ends of polymer segments incorporating 8.5 oxyethylenerepeat units. The active centers have been introduced as europium perchlorate, Eu(ClO4)(3). Samples with compositions n = 232, 62, 23, 12, and 6 (where n denotes the ratio of (OCH2CH2) moieties per lanthanide ion) have been examined. Thecombination of the information retrieved from the analysis of characteristic bands of the FTIR spectra-the perchlorate and the Amide I/Amide II features-with that obtained from the photoluminescence data demonstrates that atcompositions: n = 232 and 62 the anions are free, whereas the EU3+ ions are complexed by the heteroatoms of the polyether chains. At higher salt concentration, the cations are bonded, not only to the ClO4- ions, but also to the ether oxygen atoms of the organic segments and to the carbonyl oxygen atoms of the urea linkages. The dual behavior of U(600) with respect to cation coordination has been attributed to the presence in this nanohybrid of strong hydrogen-bonded urea-urea structures, which, at low salt content, cannot be disrupted, thus inhibiting the formation of Eu3+. . .O=C(urea) contacts and promoting the interaction between the lanthanide ions and the (OCH2CH2) moieties. The present work substantiates the claim that the activationof the coordinating sites of the di-ureasil framework can be tuned by varying either the guest salt concentration at constant chain length or the length of the organic segments at constant salt concentration This relevant property opens challenging new prospects in the fields of application of thisclass of hybrids.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 26/09/17 alle ore 09:17:39