611 resultados para EU3
Resumo:
SrMgF4xEuyTbEu3+Eu2+TbEu3+Eu2+Eu2+ESREu3+Tb3+Eu3+Tb3+Eu2+Tb4+.
Resumo:
Energy transfer phenomena have been observed by activating the oxyapatite host-lattice Ca2Gd8(SiO4)6O2 with Eu3+, Tb3+, Dy3+, Sm3+. This is based on the energy migration in the Gd3+ sublattice and trapping by the activators. The trapping efficiency for G
Resumo:
Alkaline earth (Mg, Ca. Sr) yttrium silicate oxyapatites doped with Eu3+ show red luminescence with comparable intensity. In this system of phosphors, the Eu3+ ions enter 4f sites and 6h sites simultaneously according to the fluorescence spectra, in which
Resumo:
The Angular Overlap Model (AOM) is applied to the LaOX:Eu3+(X = Cl, Br, I) series involving sigma, pi, delta and phi effects based on the experimental energy levels. The calculations are made in two cases. (1) Consider oxygen and halogen having the same bond-length. (2) Consider the real structure. In both cases, the results show that for sigma-bonding parameters, the values of e(sigma) decrease with increasing charge number of halogen, i.e. Cl- > Br- > I-, this indicates that the bonding ability also decreases with this order. The absolute values of each parameter are much larger than zero-therefore they all must be included in a practical analysis. In the second case, the values of the e(pi) parameter are negative, which means a ''back-bonding'' is formed, and this is profitable for the formation of sigma-bonding, usually referred to as ''synergic effect''.
Resumo:
At room temperature, the Bi3+ ion shows broad band characters of its luminescence in Ca2B2O5, M3B2O6 ( M=Ca,Sr ) and SrB4O7. The maxima of the Bi3+ S-1(0)-->P-3(1) absorption bands are located in the range of 240-300nm, but the energy variation of the corresponding P-3(1)-->S-1(0) emissions is very large. The maxima of these emission bands change from 350nm in Ca3B2O6;Bi3+ to 586nm in SrB4O7:Bi3+. The Stokes shift of the Bi3+ luminescence increases from 6118 cm-1, in Ca2B2O5:Bi3+, to 24439 cm-1, in SrB4O7:Bi3+. The emission intensity of the Bi3+ luminescence increases with the decreasing Stokes shift. It has been found that in Ca2B2O5, the Bi3+ ion could transfer its excitation energy to the R3+ ions ( R=Eu, Dy, Sm, Tb ) , but in, Ca3B2O6 and Sr3B2O6, only Bi3+-->Eu3+ was observed. No energy transfer from Bi3+ to R3+ was detected in SrB4O7.
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Six compounds of M2F3 center dot 1.2H(2)O (M=EU, Ga, Tb, Y, Er, LU: H2F=Fumaric acid) have been synthesized. The structures of Eu(III), T b(III), Y(III), Er(III) and Lu(III) compounds have been determined by singal crystal X-ray diffraction method. The complex of Eu(III) crystallizes in tri-clinic space group P (1) over bar, and the coordination number of Eu3+ is ten. The other four complexes crystallize in monclinic space P2(1)/c, and the coordination numbers of the metal ions are eight. Each of the complexes shows a three-dimensional net structures.
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In this paper, the yellow-to-blue intensity ratio of Dy3+ (Y/B) and the red-to-orange intensity ratio of Eu3+ (R/O) were studied in relation to the compositions and structures of alkaline-earth borates. The dependence of the energy of the Eu3+ charge-transfer band (CTB) and of the emission intensity of Dy3+ on the alkaline-earth ions and the boron content of the hosts is discussed.
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A new nonadentate ligand, N, N, N-1, N-1-[2,6-bis(3'-aminomethyl-1 1'-pyrazolyl)-4-phenylpyridine]tetrakis(acetic acid) (BPTA) for a Tb3+ fluorescent complex was synthesized. The Tb3+ complex is strongly fluorescent, having a large fluorescence quantum yield of 1.00 and very long fluorescence lifetime of 2.681 ms in 0.05 M berate buffer of pH 9.1. Streptavidin (SA) was labeled with SPTA by using its succinimidyl monoester, and the BPTA-Tb3+-labeled SA was used in sandwich-type time-resolved fluoroimmunoassay (TR-FIA) of alpha -fetoprotein (AFP) and carcinoembryonic antigen (CEA) in human sera. The Tb3+-labeled SA was also used in competitive type TR-FIA of bensulfuron- methyl (BSM) in water. The detection limits of these assays are 42 pg/mL for AFP, 70 pg/mL for CEA, and 0.4 ng/mL for BSM. In addition, a new simultaneous measurement method for AFP and CEA in a human serum sample was developed by using 4,4'-bis(1 " ,1 " ,1 " ,2 " ,2 " ,3 " ,3 " -heptafluoro-4 " ,6 " -hexanedion-6 " -yl)chlorosulfo-o-terphenyl ((BHHCT)-Eu3+-labeled anti-AFP antibody, biotinylated anti-CEA antibody, and BPTA-Tb3+-labeled SA. The concentrations of AFP and CEA in 39 human serum samples were determined, and the results were compared with those of the independently determined AFP and CEA by TR-FIA with a single-label method. A good correlation was obtained with the correlation coefficients of 0.991 for AFP and 0.994 for CEA.
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New silica-based europium fluorescent nanoparticles having surface amino groups were prepared by a covalent binding-copolymerization technique. In the nanoparticles, the fluorescent Eu3+ chelate molecules were covalently bound to silicon atoms to protect the nanoparticles from dye leaking in bio-applications. The amino groups on the surface of nanoparticles made the surface modification and bioconjugation of nanoparticles easier. The nanoparticles were characterized and developed as a new type of fluorescence probe for a highly sensitive time-resolved fluoroimmunoassay (TR-FIA) of human hepatitis B surface antigen (HBsAg).
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Two new polyacid derivative ligands of thienyl-substituted terpyridine analogues, N,N,N-1,N-1-[4'-(2"'-thienyl)-2,2':6',2"-terpyridine-6,6"-diyl]bis(methylenenitrilo) tetrakis(acetic acid) (TTTA) and N,N,N-1,N-1-[2,6-bis(3'-amino-methyl-1'-pyrazolyl)-4-(2"-thienyl)pyridine] tetrakis(acetic acid) (BTTA), were synthesized, and the luminescence properties of their Eu3+ and Tb3+ chelates were investigated. The Eu3+ chelates of the two ligands are strongly luminescent having luminescence quantum yields of 0.150 (TTTA-Eu3+) and 0.114 (BTTA-Eu3+), and lifetimes of 1.284 ms (TTTA-Eu3+) and 1.352 ms (BTTA-Eu3+), whereas their Tb3+ chelates are weakly luminescent. The TTTA-Eu3+ chelate was used for streptavidin (SA) labeling, and the labeled SA was used for time-resolved fluoroirnmunoassay of insulin in human sera. The method gives the detection limits of 33 pg ml(-1). (C) 2003 Elsevier B.V. All rights reserved.
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The first Eu3+ chelate-based phosphorescence probe specific for singlet oxygen has been designed, synthesized and characterized. The probe is highly sensitive, selective and water soluble for time-resolved luminescence detection of singlet oxygen with a detection limit of 2.8 nM.
Resumo:
The extraction of both UO22+ and trivalent lanthanide and actinide ions (Am3+, Nd3+, Eu3+) by dialkylphosphoric or dialkylphosphinic acids from aqueous solutions into the ionic liquid, 1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide has been studied and compared to extractions into dodecane. Radiotracer partitioning measurements show comparable patterns of distribution ratios for both the ionic liquid/aqueous and dodecane/aqueous systems, and the limiting slopes at low acidity indicate the partitioning of neutral complexes in both solvent systems. The metal ion coordination environment, elucidated from EXAFS and UV-visible spectroscopy measurements, is equivalent in the ionic liquid and dodecane solutions with coordination of the uranyl cation by two hydrogen-bonded extractant dimers, and of the trivalent cations by three extractant dimers. This is the first definitive report of a system where both the biphasic extraction equilibria and metal coordination environment are the same in an ionic liquid and a molecular organic solvent.
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The halide derivatives of yttrium ortho-oxomolybdate YX[MoO4] (X = F, Cl) both crystallize in the monoclinic system with four formula units per unit cell. YF[MoO4] exhibits a primitive cell setting (space group P2(1)/c, a = 519.62(2) pm, b = 1225.14(7) pm, c = 663.30(3) pm, beta = 112.851(4)degrees), whereas the lattice of YCl[MoO4] shows face-centering (space group C2/m; a = 1019.02(5) pm, b = 720.67(4) pm, c = 681.50(3) pm, beta = 107.130(4)degrees). The two compounds each contain crystallographically unique Y3+ cations, which are found to have a coordination environment of six oxide and two halide anions. In the case of YF[MoO4], the coordination environment is seen as square antiprisms, and for YCl[MoO4], trigon-dodecahedra. are found. The discrete tetrahedral [MoO4](2-) units of the fluoride derivative are exclusively bound by six terminal Y3+ cations, while those of the chloride compound show a 5-fold coordination around the tetrahedra with one edge-bridging and four terminal Y3+ cations. The halide anions in each compound exhibit a coordination number of two, building up isolated planar rhombus-shaped units according to [Y2F2](4+) in YF[MoO4] and [Y2Cl2](4+) in YCl[MoO4], respectively. Both compounds were synthesized at high temperatures using Y2O3, MoO3, and the corresponding yttrium trihalide in a molar ratio of 1:3:1. Single crystals of both are insensitive to moist air and are found to be coarse shaped and colorless with optical band gaps situated in the near UV around 3.78 eV for the fluoride and 3.82 eV for the chloride derivative. Furthermore, YF[MoO4] seems to be a suitable material for doping to obtain luminescent materials because the Eu3+-doped compound shows an intense red luminescence, which has been spectroscopically investigated.
Resumo:
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 con contribute to a clearer understanding of the photophysical processes in luminescent lanthanide complexes.
