Luminescence properties of sol-gel derived spherical SiO2@Gd-2(WO4)(3): Eu3+ particles with core-shell structure

Monodisperse, core-shell structured SiO2@Gd-2(WO4)(3):Eu3+ particles were prepared by the sol-gel method. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy, photoluminescence (PL) and low-voltage cathodoluntinescence (CL). PL and CL study revealed that the core-shell structured SiO2@Gd-2(WO4)(3):Eu3+ particles show strong red emission dominated by the D-5(0)-F-7(2) transition of Eu3+ at 615 nm with a lifetime of 0.89 ins. The PL and CL emission intensity can be tuned by the coating number of Gd-2(WO4)(3):Eu3+ phosphor layers on SiO2 particles, the size of the SiO2 core particles, and by accelerating voltage and the filament current, respectively.

Electrochemical characteristics and microstructure of Zr0.9Ti0.1Ni1.1Mn0.6V0.3-LaNi5 composite hydrogen storage alloys

AB(2-x)%LaNi5 (x =0, 1, 5, 10) composite alloys were prepared by melting Zr0.9Ti0.1Ni1.1Mn0.6V0.3 with a small amount of LaNi5 alloy as addition. The microstructure and electrochemical characteristics of the composite alloys were investigated by means of XRD, SEM, EDS and electrochemical measurements. It was shown that LaNi5 addition does not change the basic hexagonal C14 Laves phase of AB(2) alloys, but some second phases have segregated. It was found that the addition of LaNi5 greatly improves the activation property, high-rate dischargeability (HRD) and charge-discharge cycling stability of AB(2) Laves phase alloy. At current density of 1200 mA/g, HRD of the alloy increases from 38.92% (x =0) to 60.09% (x = 10). The capacity retention of the alloy after 200 charge-discharge cycles increases from 57. 10% (x = 0) to 83.86% (x = 5) and 67.31% (x = 10). The improvement of the electrochemical characteristics caused by LaNi5 addition seems to be related to formation of the second phases.

Synthesis and characterization of Gd(OH)(3) nanobundles

Gd(OH)(3) nanobundles, which consisted of bundle-like nanorods, have been prepared through a simple and facile hydrothermal method. The crystal, purity, morphology and structural features of Gd(OH)(3) nanobundles are investigated by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive X-ray (EDX). A possible formation mechanism of Gd(OH)(3) nanobundles is briefly discussed.

VIV-UV excited luminescent properties of LnCa4O(BO3)3 : RE3+(Ln = Y, La, Gd; Re=Eu, Tb, Dy, Ce)

Calcium lanthanide oxyborate doped with rare-earth ions LnCa(4)O(BO3)(3):RE3+ (LnCOB:RE, Ln = Y, La, Gd, RE = Eu, Tb, Dy, Cc) was synthesized by the method of solid-state reaction at high temperature. Their fluorescent spectra were measured from vacuum ultraviolet (VUV) to visible region at room temperature. Their excitation spectra all have a broadband center at about 188 nm, which is ascribed to host absorption. Using Dorenbos' and J phi rgensen's work [P. Dorenbos, J. Lumin. 91 (2000) 91, R. Resfeld, C.K. J phi rgensen. Lasers and Excite States of Rare Earth [M], Springer, Berlin, 1977, p. 45], the position of the lowest 5d levels E(Ln,A) and charge transfer band E-ct were calculated and compared with their excitation spectra.Eu3+ and Tb3+ ions doped into LnCOB show efficient luminescence under VUV and UV irradiation. In this system, Ce3+ ions do not show efficient luminescence and quench the luminescence of Tb3+ ions when Tb3+ and Ce3+ ions are co-doped into LnCOB. GdCOB doped with Dy3+ shows yellowish white light under irradiation of 254 nm light for the reason that Gd ions transfer the energy from itself to Dy.

Photoluminescent properties of sol-gel derived (La, Gd)MgB5O10 : Ce3+/Tb3+ nanocrystalline thin films

Ce3+ and/or Tb3+-doped (La,Gd)MgB5O10 nanocrystalline thin films were deposited on silica glass substrates by a sol-gel dip-coating process using triethyl borate B(OC2H5)(3) as the boron source. The results of XRD indicated that the films have fully crystallized after annealing at 800 degrees C. The films are transparent, uniform and crack free with a thickness of about 300 nm, consisting of particles with an average grain size of 50 nm. The luminescence and energy transfer properties of Ce3+ and Tb3+ have been studied in the films. It is confirmed that the excitation energy of Ce3+ transfers to the Gd3+, migrates over the Gd3+ sublattices, trapped by the Tb3+ and resulted in its characteristic green emission (D-5(4)-F-7(5) at 543 nm) in GdMgB5O10 nanocrystalline films as in the powder phosphors.

The structure and electrochemical characteristics of La0.67Mg0.33 (Ni0.8Co0.1Mn0.1)(x) (x=2.5-5.0) multiphase alloys for nickel-metal hydride batteries

This paper presents results concerning structure and electrochemical characteristics of the La0.67Mg0.33 (Ni0.8Co0.1Mn0.1) (x) (x=2.5-5.0) alloy. It can be found from the result of the Rietveld analyses that the structures of the alloys change obviously with increasing x from 2.5 to 5.0. The main phase of the alloys with x=2.5-3.5 is LaMg2Ni9 phase with a PuNi3-type rhombohedral structure, but the main phase of the alloys with x=4.0-5.0 is LaNi(5)phase with a CaCu5-type hexagonal structure. Furthermore, the phase ratio, lattice parameter and cell volume of the LaMg2Ni9 phase and the LaNi5 phase change with increasing x. The electrochemical studies show that the maximum discharge capacity increases from 214.7 mAh/g (x=2.5) to 391.1 mAh/g (x=3.5) and then decreases to 238.5 mAh/g (x=5.0). As the discharge current density is 1,200 mA/g, the high rate dischargeability (HRD) increases from 51.1% (x=2.5) to 83.7% (x=3.5) and then decreases to 71.6% (x=5.0). Moreover, the exchange current density (I-0) of the alloy electrodes first increases and then decrease with increasing x from 2.5 to 5.0, which is consistent with the variation of the HRD. The cell volume reduces with increasing x in the alloys, which is detrimental to hydrogen diffusion and accordingly decreases the low-temperature dischargeability of the alloy electrodes.

Structures and electrochemical characteristics of several kinds of alloys

The structures and the electrochemical characteristics of La0.7-xCexMg0.3Ni2.8Co0.5 (x = 0.1-0.5) alloy, Ti0.25-xZrxV0.35Cr0.1Ni0.3 (x = 0.05-0.15) alloy and AB(3

Coating nano-hemalite on (Y,Gd)BO3 : Eu3+ phosphors by a facile method

(Y, Gd) BO3:Eu3+ particles coated with nano-hematite were prepared by a facile method I for example (humid) solid phase reaction at room temperature. The resulted hematite-coated (Y, Gd)BO3:Eu3+ particles were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and photoluminescence spectra (PL). The SEM and EDS analyses indicate that the particles are coated with a very thin layer of iron oxide. XPS results further confirmed that the coating was hematite, and the coating thickness was in nanometer range. XRD patterns showed that either the hematite coating was too thin or the content of hematite was too small, so that the XRD cannot detect it. The emission spectra illustrate that the peak near 580 nm disappears due to the coating of iron oxide, and when the coating is very thin, the ratio of D-5(0)-> F-7(2) to D-5(2)-> F-7(1) of coated particles is higher than that of uncoated ones, which indicates that the color purity of the phosphor is increased by coating nano-hematite.

Computer simulation of Zn(II) speciation and effect of Gd(III) on Zn(II) speciation in human blood plasma

The speciation and distribution of Zn(II) and the effect of Gd(III) on Zn(II) speciation in human blood plasma were studied by computer simulation. The results show that, in normal blood plasma, the most predominant species of Zn(II) are [Zn(HSA)] (58.2%), [Zn(IgG)](20.1%), [Zn(Tf)] (10.4%), ternary complexes of [Zn(Cit)(Cys)] (6.6%) and of [Zn(Cys)(His)H] (1.6%), and the binary complex of [Zn(CYS)(2)H] (1.2%). When zinc is deficient, the distribution of Zn(II) species is similar to that in normal blood plasma. Then, the distribution changes with increasing zinc(II) total concentration. Overloading Zn(II) is initially mainly bound to human serum albumin (HSA). As the available amount of HSA is exceeded, phosphate metal and carbonate metal species are established. Gd(III) entering human blood plasma predominantly competes for phosphate and carbonate to form precipitate species. However, Zn(II) complexes with phosphate and carbonate are negligible in normal blood plasma, so Gd(III) only have a little effect on zinc(II) species in human blood plasma at a concentration above 1.0x10(-4) M.

Luminescence properties of RP1-xVxO4: A (R=Y, Gd, La; A=Sm3+Er3+ x=0, 0.5, 1) thin films prepared by pechini sol-gel process

Thin film phosphors with compositions of RP1-xVxO4: A (R = Y, Gd, La; A = Sm3+, Et3+; x = 0, 0.5, 1) have been prepared by a Pechini sol-gel process. X-Ray diffraction, atomic force microscopy (AFM), photoluminescence excitation and emission spectra were utilized to characterize the thin film phosphors. The results of XRD showed that a solid solution formed in YVxP1-xO4: A film series from x = 0 to x = 1 with zircon structure, which also held for GdVO4: A film. However, LaVO4: A film crystallized with a different structure, monazite. AFM study revealed that the phosphor films consisted of homogeneous particles ranging from 90 to 400 nm depending on the compositions. Upon short ultraviolet excitation, the films exhibit the characteristic Sm(3+ 4)G(5/2)-H-6(J) (J=5/2, 7/2, 9/2) emission in the red region and Er3+ H-2(11/2), S-4(3/2)-I-4(15/2) emission in the green region, respectively With the increase of x values in YVxP1-xO4: SM3+ (Er3+) films, the emission intensity Of SM3+ (Er3+) increases due to the increase of energy transfer probability from VO43- to Sm3+ (Er3+). Due to the structural effects, the Sm3+ (Er3+) shows similar spectral properties in YVO4 and GdVO4 films, which are much different from those in LaVO4 film.

共沉淀法合成稀土正磷酸盐(La,Gd)PO_4∶RE~(3+)(RE=Eu,Tb)及其真空紫外光谱特性

采用共沉淀法制备了稀土正磷酸盐荧光粉 ( La,Gd) PO4∶ RE3 +( RE=Eu,Tb) .红外光谱分析发现Gd PO4的红外光谱吸收峰与 La PO4一致 ,只是峰位向高波数方向移动 . ( La,Gd) PO4∶ RE3 +的真空紫外光谱特性研究表明 ,Gd3 +在能量传递过程中起中间体作用 .XPS研究揭示 ,La PO4的价带由 O2 -的 2 p能级构成 ,而 Gd PO4的价带则是由 O2 - 的 2 p能级和 Gd3 +的 4 f能级共同构成.

Synthesis and evaluation of novel polysaccharide-Gd-DTPA compounds as contrast agent for MRI

Macromolecular conjugates of two kinds of natural polysaccharides, that from Panax quinquefolium linn (PQPS) and Ganoderma applanatum pat (GAPS), with gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) have been synthesized and characterized by means of FTIR, elementary analysis and ICP-AES. Their stability was investigated by competition study with Ca2+, EDTA (ethylenediaminetetraacetic acid) and DTPA. Polysaccharide-bound complexes exhibit T-1 relaxivities of 1.5-1.7 times that of Gd-DTPA in D2O at 25degreesC and 9.4T. MR imaging of Sprague-Dawley (SD) rats showed remarkable enhancement in rat liver and kidney after i.v. injection of these two complexes: liver parenchyma 60.9+/-5.6%, 57.8+/-7.4% at 65-85 min; kidney 144.9+/-14.5%, 199.9+/-25.4% at 10-30 min for PQPS-GdDTPA, GAPS-Gd-DTPA at gadolinium dose of 0.083 and 0.082 mmol/kg, respectively. Our preliminary in vivo and in vitro study indicates that the two kinds of polysaccharide-bound complexes are potential tissue-specific contrast agents for MRI.

Comparison between Gd-DTPA and several bisamide derivatives as potential MRI contrast agents

Four neutral gadolinium complexes of diethylenetriaminepentaacetic acid (DTPA)-bisamide derivatives have been synthesized and characterized. Their potential application as tissue-specific and low-osmolarity MRI contrast agents has been evaluated by in vitro and in vivo experiments. Their measured relaxivities in D2O, bovine serum albumin and human serum transferrin solutions showed favorable relaxation ability. In vivo studies have proven that Gd(DTPA-BDMA), Gd(DTPA-BIN), and Gd(cyclic-DTPA-1,2-pn) could be promising liver-specific MRI contrast agents and Gd(DTPA-BDMA), and Gd(cyclic-DTPA-1,2-pn) have favorable renal excretion capability. Among them, Gd(cyclic-DTPA-1,2-pn) is a more powerful hepatic contrast agent and Gd(DTPA-BIN) provides the stable imaging contrast for several hours. They also show a lower toxicity.

Computer simulation of Gd(III) speciation in human interstitial fluid

The speciation and distribution of Gd(III) in human interstitial fluid was studied by computer simulation. Meantime artificial neural network was applied to the estimation of log beta values of complexes. The results show that the precipitate species, GdPO4 and Gd-2(CO3)(3), are the predominant species. Among soluble species, the free Gd(III), [Gd(HSA)], [Gd(Ox)] and then the ternary complexes of Gd(III) with citrate arc main species and [Gd-3(OH)(4)] becomes the predominant species at the Gd(III) total concentration or 2.2x10(-2)mol/L.

Novel indigo light emitting long-lasting phosphors CdSiO3: RE3+ (RE = Y, La, Gd, Lu)

A series of novel indigo light emitting long-lasting phosphors CdSiO3: RE3+ (RE = Y, La, Gd, Lu) was prepared by the conventional high-temperature solid-state method. The XRD, photoluminescence (PL) spectra and afterglow intensity decay were used to characterize the synthesized phosphors. These phosphors emitted indigo light and showed long-lasting phosphorescence. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254-nm UV irradiation have been removed for more than 30 min.