Study of physicochemical properties and active oxygen in structures of layered mixed La4BaCu5-xMxO13+lambda (M = Mn, Co)

Two series of layered mixed oxides La4BaCu5-xMxO13+lambda(M = Mn, Co, x = 0 similar to 5) were prepared and characterized by means of XRD, XPS, O-2-TPD and chemical analysis. The results show that their structures are 5-layered ABO(3) perovskite, and the XPS and O-2-TPD investigation confirms that there exists synergistic effect between Cu ion and M when M ion is doped into the lattice of La4BaCu5O13+lambda,, and the synergistic effect between Mn and Cu is stronger than that of Cu-Co.

Electrocatalytic mechanism for formaldehyde oxidation on the highly dispersed gold microparticles and the surface characteristics of the electrode

Electrocatalytic mechanism for the electrochemical oxidation of formaldehyde (HCHO) on the highly dispersed Au microparticles electrodeposited on the surface of the glass carbon (GC) electrode in the alkaline Na2CO3/NaHCO3 solution and the surface characteristics of the Au microparticle-modified glass carbon (Au/GC) electrode were studied with in situ FTIR spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the final products of HCHO oxidation is HCOO- at the Au/GC electrode and CO2 at the bulk Au electrode. The difference may be ascribed to the different surface characteristics between the Au/GC electrode and the bulk Au electrode. (C) 1999 Elsevier Science B.V. All rights reserved.

Photophysical properties of rare earth complexes with 3,4-furandicarboxylic acid and 1,10-phenanthroline

Synthesis, IR spectra, UV-vis spectra and photophysical properties of Gd3+, Eu3+, Tb3+ complexes with 3,4-furandicarboxylic acid and 1,10-phenanthroline are reported. Intramolecular energy transfer process for these complexes is discussed in detail. It is found that the intramolecular energy transfer efficiency depends on the relative positions between the resonance energy levels of the central rare earth ions and the lowest triplet state energies of ligands.

Rare earth complexes with Ge-132 and their catalytic hydrolysis to phosphatide bond of mononucleotide

The complexes of a series of rare earths with Ge-132 have been prepared. The carboxyl anions of Ge-132 molecule were coordinated to rare earth ion with chelate style. In the complexes molecule, the GeO3/2 group of Ge-132 were hydrolyzed to become -Ge(OH)(3) group, and later does:not coordinate with rare earth ions. All of the complexes possess similar properties. In aqueous solution of pH 6 and 50 degrees C, these complexes can obviously selectively catalytically hydrolize the phosphatide bond of 5'-AMP and 5'-dAMP into phosphatic acid and riboside.

Synthesis, characterisation and catalytic activity of propionamide complexes of rare earth chlorides

Propionamide complexes of rare earth chlorides were synthesized, Formula of the complexes is LnCl(3). 3BA. The ligand is shown to behave as a normal amide donor With the oxygen of the carbonyl group coordinated to the metal ions. Binary system composed Elf propionamide and aluminum alkyl shows higher activity and stereospecificity for butadiene polymerization. The cis-1,4 content of polybutadiene is more than 98%.

Probing lanthanide ions binding on tRNA(Phe) by H-1 NMR

The structure of phenylalanine transfer ribonucleic acid (tRNA(Phe)) in solution was explored by H-1 NMR spectroscopy to evaluate the effect of lanthanide ion on the structural and conformational change. It was found that La3+ ions possess specific effects on the imino proton region of the H-1 NMR spectra for yeast tRNA(Phe). The dependence of the imino proton spectra of yeast tRNA(Phe) as a function of La3+ concentration was examined, and the results suggest that the tertiary base pair G(15). C-48, which is located in the terminal in the augmented dihydrouridine helix (D-helix), was markedly affected by La3+ (shifted to downfield by as much as 0.35). Base pair U-8. A(14) in yeast tRNA(Phe), which are stacked on G(15). C-48, was also affected by added La3+ when 1 similar to 2 Mg2+ were also present. Another imino proton that may be affected by La3+ in yeast tRNA(Phe) is that of the tertiary base pair G(19). C-56. The assignment of this resonance in yeast tRNA(Phe) is tentative since it is located in the region of highly overlapping resonances beween 12.6 and 12.2. This base pair helps to anchor the D-loop to the T Psi C loop. The binding of La3+ caused conformational change of tRNA, which is responsible for shifts to upfield or downfield in H-1 NMR spectra.

Studies on plant calmodulin and its interaction with antagonist W-7 by Ln(3+) luminescence probes

Plant calmodulin (CaM) has been extracted from cauliflower, and the purified CaM has been identified with the activation of NAD kinase (NADK) and the inhibition effect of CaM antagonist W-7. CaM's intrinsic fluorescence and Tb3+ fluorescence showed that there was one tyrosine residue and four metal-binding sites in cauliflower CaM. Based on Forster-type nonradiative energy theory, the distances of Tyr --> site III, IV have been determined, and these are 1.23 nm (Tyr --> site III ) and 1.18 nm(Tyr --> site IV). The Eu3+ and Tb3+ fluorescence probes showed that the combination of CaM with W-7 resulted in significant change on CaM's conformation, but did not affect coordination environment of metal-binding sites.

Extraction and separation of heavy rare earth (III) with Extraction Resin containing di(2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272)

Extraction resins, of the type of;levextrel, (which is a collective term for styrene/divinylbenzene based copolymers of predominantly macroporous structure that contain a selective extractant) are important for the recovery and separation of metal ions, as they combine features of solvent extraction and ion exchange resins. This paper presents the results of the adsorption of heavy rare earth ions (Ho(III), Er(III), Tm(III), Yb(III), Lu(III) and Y(III)) from hydrochloric acid solutions at 0.2 mol/L ionic strength and 50 degrees C by the extraction resin containing di (2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272) and the chromatographic separation of (Er(III), Tm(III) and Yb(III)). Technological separation products, with purity and yield of Tm2O3 >99.97%, >80%, Er2O3 >99.9%, >94% and Yb2O3 >99.8%, >80% respectively, have been obtained from a feed having the composition Tm2O3 60%, Er2O3 10%, and Yb2O3 3%, the others 27%. The distribution coefficients, extraction equilibrium constants and separation factors have been determined as a function of acidity, loading of the resin and rare earths, flow rates and column ratios. The resolutions and efficiencies of separation of Er/Tm/Yb each other have been calculated. The stoichiometry of the extraction of rare earth ions has been suggested as well.

Physico-chemical properties and catalytic behavior of LnSrNiO(4) mixed oxides for NO decomposition

A series of LnSrNiO(4)(A(2)BO(4), Ln = La, Pr, Nd, Sm, Gd) mixed oxides with K2NiF4 structure, in which A-site(Sr) was partly substituted by individual light rare earth element, was prepared. The solid state physico-chemical properties including crystal structure, defect structure, IR spectrum, valence state of H-site ion, nonstoichiometric oxygen, oxygenous species, the properties of oxidation and reduction etc. as well as the catalytic behavior for NO decomposition on these mixed oxides were investigated. The results show that all of these mixed oxide catalysts have high activity for the direct decomposition of NO(at 900 degrees C the conversion of NO is more than 90%). The effect of the substitution of light rare earth elements at A-site on catalytic behavior for NO decomposition was elucidated.

Synthesis, luminescence and magnetic properties of YGa3-xCrxB4O12

The synthesis temperature of YGa3B4O12 and the effect of the synthesis temperature and chromium doping on the luminescence properties were studied. YGa3-xCrxB4O12 were synthesized and their magnetic properties were described. Results show that the fluorescence intensity increases with the increasing of synthesis temperature. The structure of compounds was stabilized, and their emission spectra were changed when small quantity of chromium was doped in. The magnetic susceptibilities increase with the increasing of Cr3+ concentration.

Electrochemical behavior of Nd3+ and Ho3+ in LiCl-KCl eutectic melt

The electrochemical behavior of Nd3+ and Ho3+ ions on molybdenum electrode in the LiCl-KCl eutectic melts has been studied by cyclic voltammetry and open-circuit potentiometry. The results show that the reduction process of Nd3+ and Ho3+ ions on molybdenum electrode is one-step three electron reversible reaction. The diffusion coefficients of Nd3+ and Ho3+ ions are 1.13 x 10(-6) cm(2).s(-1)(450 degrees C) and 2.142 x 10(-5) cm(2).s(-1)(450 degrees C), respectively. The measured standard electrode potential of Ho3+/Ho is 2.987 V(vs. Cl/Cl-), being more negative than the theoretical one, the reason of which is also discussed.

Luminescence properties of Ce3+ in KMF3(M=Mg, Ca, Sr, Ba) hosts with perovskite structure

KMF3(M = Mg, Ca, Sr, Ba) compounds were synthesized by solid state reaction under argon atmosphere. Their structures were determined by X-ray diffraction. It belongs to cubic system with perovskite structure. The excitation and emission spectra of KMF3:Ce3+ were measured. According to the characteristics of spectral structures, the occupation site of Ce3+ is discussed.

High-yield extraction of endohedral rare-earth fullerenes

The technique of high-temperature high-pressure extraction with pyridine has been successfully utilized to extract a wide variety of endohedral rare-earth fullerenes of the type Ln@C-2n (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). Ln@C-80, Ln@C-82, and Ln(2)@C-80 for most of the rare-earth metals can be produced with high-yield and selectively extracted from the carbon-are evaporation soot. Metallofullerenes containing Sm, Eu, and Yb (which could have +2 oxidation states) are especially difficult to extract. Some possible reasons for the high-yield extraction are discussed. The laser desorption mass spectrometric characterization results indicate a relationship between the extraction yields of metallofullerenes and the oxidation states and ionic radii of the rare-earths.

Preparation of highly dispersed gold microparticles and their electrocatalytic activity for the oxidation of formaldehyde

The electrochemical preparation of highly dispersed Au microparticles on the surfaces of glassy carbon (GC) electrodes and their electrocatalytic activities for the oxidation of formaldehyde were studied. It was found that the reduction of Au3+ to Au is controlled by diffusion and the formation mechanism of Au microparticles on the GC surfaces corresponds to an instantaneous nucleation and diffusion-controlled three dimensional growth process. The particle size is about 80-90 nm in diameter after the electrochemical ageing treatment. These highly dispersed Au microparticles have high surface areas and exhibit better electrocatalytic activity than that of bulk-form Au toward the electrochemical oxidation of formaldehyde in alkaline media.

Roles of oxygen vacancy and lower valence metallic ion in direct decomposition of NO over La-2-x(Sr,Th)(x)CuO4+/-lambda

Two systems of La2-xSrxCuO4+/-lambda and La2-xThxCuO4+/-lambda, mixed oxides with K2NiF4 structure were synthesized. The compositions and structures of the catalysts were characterized by means of XRD, XPS, chemical analysis and so on. The catalytic behavior for the direct decomposition of NO has been investigated. The results show that the catalytic activity is closely related to the oxygen vacancy and lower valence metallic ion in the direct decomposition of NO. The presence of oxygen vacancy is necessary for mixed oxide to have steady activity in NO decomposition.