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Ribeiro, Sidney José Lima; Dahmouche, K.; Ribeiro, Clóvis Augusto; Santilli, Celso Valentim; Pulcinelli, Sandra Helena

doi:10.1023/a:1008673211834

Cited by 109 publications

(127 citation statements)

References 5 publications

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“…In fact, the ureasil hybrids are room-temperature white light phosphors ͑multiwavelength emitters͒ combining narrow yellow-red Eu 3ϩ luminescence with broad green-blue emission. [29][30][31][32] The white light phosphor nature of these urea cross-linked organically modified silicates has already been reported for the undoped ureasil host, i.e., on the absence of any activator metal ion. 29,30,42,43 The achievement of full color displays is one of the main challenging tasks on the field of luminescent materials.…”

Section: Introductionmentioning

confidence: 98%

“…24 A different route in order to overcome both the crystallization character and the high hygroscopic tendency of lanthanide-based POE electrolytes can be achieved by the sol-gel synthesis of similar luminescent polymers based on organic/inorganic hybrid materials. [29][30][31][32][33] In recent years the use of the sol-gel approach for the synthesis of a wide range of novel materials has attracted considerable scientific interest. 34 In particular, the advantages of the rich chemistry of silicon-based networks have been employed to synthesize amorphous and transparent hybrid organic/inorganic structures incorporating lanthanide salts.…”

Section: Introductionmentioning

confidence: 99%

“…[38][39][40][41][42][43] The relevance of the sol-gel method for the synthesis of a different family of europium-based hybrid materials, classed as ureasils, based on a siliceous backbone to which oxyethylene units are covalently grafted by means of urea linkages was recently shown by our two groups. [29][30][31][32] These organically modified silicates are obtained as transparent elastomeric and essentially amorphous thin monoliths-thermally stable up to about 200°C-and, besides the observed decrease in its crystalline nature and hygroscopic propensity, they clearly present several marked emissions advantages relatively to the analogous Eu 3ϩ -based polymer electrolytes. In fact, the ureasil hybrids are room-temperature white light phosphors ͑multiwavelength emitters͒ combining narrow yellow-red Eu 3ϩ luminescence with broad green-blue emission.…”

Section: Introductionmentioning

confidence: 99%

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White light emission ofEu3+-based hybrid xerogels

et al. 1999

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The luminescence spectra and extended x-ray-absorption fine-structure ͑EXAFS͒ measurements of a series of Eu 3ϩ -based organic/inorganic xerogels were reported and related to the local coordination of the lanthanide cations. The hybrid matrix of these organically modified silicates, classed as U (2000) ureasils, is a siliceous network to which short organic chains containing oxyethylene units are covalently grafted by means of urea bridges. The luminescent centers were incorporated as europium triflate, Eu͑CF 3 SO 3 ͒ 3 , and europium bromide, EuBr 3 , with concentrations 200уnу20 and nϭ80, 40, and 30, respectively-where n is the number of ether oxygens in the polymer chains per Eu 3ϩ cation. EXAFS measurements were carried out in some of the U (2000) n Eu͑CF 3 SO 3 ͒ 3 xerogels ͑nϭ200, 80, 60, and 40͒. The obtained coordination numbers N ranging from 12.8, nϭ200, to 9.7, nϭ40, whereas the average Eu 3ϩ first neighbors distance R is 2.48-2.49 Å. The emission spectra of these multiwavelength phosphors superpose a broad green-blue band to a series of yellow-red narrow 5 D 0 → 7 F 0 -4 Eu 3ϩ lines and to the eye the hybrids appeared to be white, even at room temperature. The ability to tune the emission of the xerogels to colors across the chromaticity diagram is achieved by changing the excitation wavelength and the amount of salt incorporated in the hybrid host. The local environment of Eu 3ϩ is described as a continuous distribution of closely similar low-symmetry network sites. The cations are coordinated by the carbonyl groups of the urea moieties, water molecules, and, for U (2000) n Eu͑CF 3 SO 3 ͒ 3 , by the SO 3 end groups of the triflate anions. No spectral evidences have been found for the coordination by the ether oxygens of the polyether chains. A mean radius for the first coordination shell of Eu 3ϩ is calculated on the basis of the emission energy assignments. The results obtained for U (2000) n Eu͑CF 3 SO 3 ͒ 3 , 2.4 Å for 90 уnу40 and 2.6 and 2.5 Å for nϭ30 and 20, respectively, are in good agreement with the values calculated from EXAFS measurements. The energy of the intraconfigurational charge-transfer transitions, the redshift of the 5 D 0 → 7 F 0 line, with respect to the value calculated for gaseous Eu 3ϩ , and the hypersensitive ratio between the 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 transitions, point out a rather low covalency nature of the Eu 3ϩ first coordination shell in these xerogels, comparing to the case of analogous polymer electrolytes modified by europium bromide. ͓S0163-1829͑99͒03138-0͔

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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White light emission ofEu3+-based hybrid xerogels

et al. 1999

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“…[54] Up to now, research has been disclosed gradually and towards distinct purposes ranging from fundamental aspects of the Ln 3þ spectroscopy (e.g., the calculus of the radiative and nonradiative transition rates and the 4f-4f transition intensities) to the host-to-Ln 3þ energy-transfer mechanisms, and from the use of Ln 3þ ions as local probes to materials' design and functionalization. All this research activity has been focused on amorphous organic-inorganic hybrids, either incorporating ionic salts [55][56][57][58][59][60][61][62][63][64][65][66][67] and organic complexes [23,30,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82] or formed through the covalent attachment bonding grafting of those complexes to the siliceous domains, [83][84][85][86][87][88][89][90][91][92][93][94][95][96]…”

Section: Introductionmentioning

confidence: 99%

Lanthanide‐Containing Light‐Emitting Organic–Inorganic Hybrids: A Bet on the Future

et al. 2009

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Interest in lanthanide-containing organic-inorganic hybrids has grown considerably during the last decade, with the concomitant fabrication of materials with tunable attributes offering modulated properties. The potential of these materials relies on exploiting the synergy between the intrinsic characteristics of sol-gel derived hosts (highly controlled purity, versatile shaping and patterning, excellent optical quality, easy control of the refractive index, photosensitivity, encapsulation of large amounts of isolated emitting centers protected by the host) and the luminescence features of trivalent lanthanide ions (high luminescence quantum yield, narrow bandwidth, long-lived emission, large Stokes shifts, ligand-dependent luminescence sensitization). Promising applications may be envisaged, such as light-emitting devices, active waveguides in the visible and near-IR spectral regions, active coatings, and bio-medical actuators and sensors, opening up exciting directions in materials science and related technologies with significant implications in the integration, miniaturization, and multifunctionalization of devices. This review provides an overview of the latest advances in Ln(3+)-containing siloxane-based hybrids, with emphasis on the different possible synthetic strategies, photoluminescence features, empirical determination.

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“…7 F 1 transition is independent of the chemical environment of the ion, and that the radiative lifetime can be calculated from its emission spectrum. [26][27][28][29][30][31] The photoacoustic (PA) technique is the complement of luminescence spectroscopy. The PA signal is obtained by detecting the heat generated through the nonradiative relaxation re-leased by the sample after absorbing periodically modulated incident light.…”

Section: Introductionmentioning

confidence: 99%

Listening to Lanthanide Complexes: Determination of the Intrinsic Luminescence Quantum Yield by Nonradiative Relaxation

Yang

Liu

et al. 2008

ChemPhysChem

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The photophysical properties of lanthanide complexes have been studied extensively; however, fundamental parameters such as the intrinsic quantum yield as well as radiative and nonradiative decay rates are difficult or even impossible to measure experimentally. Herein, a photoacoustic (PA) method is proposed to determine the intrinsic quantum yield of lanthanide complexes with lifetimes in the order of milliseconds. This method is used to determine the intrinsic quantum yields for europium(III)‐containing metallomesogens as well as terbium(III) complexes. The results show that the PA signal is sensitive to both the lifetime and the ratio of the fast‐to‐slow heat component of the samples. It is found that there is an efficient ligand sensitization and a moderate intrinsic quantum yield for the complexes. The intrinsic quantum yield of Eu3+ in the metallomesogens exhibits an obvious increase upon the isotropic liquid to smectic A transition. The proposed PA method is quite simple, and can contribute to a clearer understanding of the photophysical processes in luminescent lanthanide complexes.

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Untitled

Cited by 109 publications

References 5 publications

White light emission ofEu3+-based hybrid xerogels

White light emission ofEu3+-based hybrid xerogels

Lanthanide‐Containing Light‐Emitting Organic–Inorganic Hybrids: A Bet on the Future

Listening to Lanthanide Complexes: Determination of the Intrinsic Luminescence Quantum Yield by Nonradiative Relaxation

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