LUMINESCENCE AND ENERGY-TRANSFER OF RARE-EARTH-METAL IONS IN MG2Y8(SIO4)(6)O-2

The photoluminescence of Ce3+, Tb3+ and Sm3+, and energy transfer from Ce3+ to Tb3+, Dy3+ and Sm3+ in Mg2Y8(SiOd(4))(6)O-2 are reported and discussed. The Ce3+ ion shows blue luminescence under UV excitation, and occupies simultaneously the 4f site and 6h site in the host lattice. The optimum concentrations for the D-5(3) and D-5(4) emissions of Tb3+ and the (4)G(5/2) emission of Sm3+ are determined to be 0.04, 0.20 and 0.10 mol in every mol of Mg2Y8(SiO4)(6)O-2, respectively. The critical distances responsible for the cross-relaxation between the D-5(3)-D-5(4) and F-7(6)-F-7(0) transitions of Tb3+ and between the (4)G(5/2)-F-4(9/2) and H-6(5/2)-F-4(9/2) transitions of Sm3+ are estimated to be 1.43 and 1.06 nm, respectively. Both Tb3+ and Dy3+ can be sensitized by Ce3+, but Ce3+ and Sm3+ quench each other.

INTERACTIONS OF RARE-EARTH LENS WITH BOVINE BLOOD CU(ZN)-SUPEROXIDE DISMUTASE

The interactions of lanthanium trichloride and terbium trichloride with bovine blood Cu (Zn)-superoxide dismutase [Cu(Zn)-SOD] in the aqueous solution of hexamethylenetetrarnine buffer (pH = 6.3) have been studied by using fluorescece, CD and ESR spectra. The results indicated that rare earth ions were coordinated to the carboxyl groups of acidic amino acid residues which were far from active center of the Cu(Zn)-SOD molecule and only lightly disturbed the secondary structure of the enzyme protien, and made the coordination structure of enzyme-bound CU2+ come from the rhombchedron to the axial shape at 77 K and the activity of Cu(Zn)-SOD enzyme was not nearly changed at room temperature.

CHEMICAL-BONDS AND DIELECTRIC-CONSTANTS OF REM (RE=RARE EARTH, M=N, P, AS, SB) CRYSTALS

By using Pillips and van Vechten theory, the chemical bond parameters and dielectric constants of REM (RE=rare earth, M=N, P, As, Sb) crystals were calculated. The values calculated of dielectric constants agree with the experimental values.

CHEMICAL-IONIZATION MASS-SPECTROMETRY OF SOME NITRO-CONTAINING BIFUNCTIONAL AROMATIC-COMPOUNDS - LOCATION OF PROTONATION SITE

It is found that the nitro substituent of some aromatic bifunctional compounds shows unusual reactivity towards protonation. In the chemical ionization mass spectra of nitrobenzoic acids and their esters and amides, and of nitrophenols and their ethers, protonations on the carboxyl, ester, amide, hydroxyl or alkoxyl groups are highly suppressed by that on the nitro group. As a result, fragmentations based on protonation on these groups unexpectedly become negligible. Ortho effects were observed for all the ortho isomers where the initial protonation on the nitro group is followed by an intramolecular proton transfer reaction, which leads to the expected 'normal' fragmentations. Protonation on the nitro substituent is much more favourable in energy than on any of the other substituents. The interaction of the two substituents through the conjugating benzene ring is found to be responsible for this 'unfair' competitive protonation. The electron-attracting nitro group strongly destabilizes the MH+ ions formed through protonation on the other substituent; although the COR (R = OH, OMe, OEt, NH2) groups are also electron-withdrawing, their effects are weaker than that of NO2; thus protonation on the latter group produces more-stable MH+ ions. On the other hand, an electron-releasing group OR (R = H, Me, Et) stabilizes the nitro-protonated species; the stronger the electron-donating effect of this group the more stable the nitro-protonated ions.

Preparation and properties of rare earth hydroxides and oxides ultrafine powders in alcohol

A series of rare earth hydroxides and oxides ultrafine powders have been prepared by precipitation method using alcohol as dispersive and protective reagent. It was first to find that the crystallite size of cubic rare earth oxides had Lanthanide shrinking effect,but average crystal lattice distortion rate possessed lanthanide swelling effect;the change of diffraction intensity with atomic number presented an inverted W type, and double peaks structure was formed.

THE SYNTHESIS AND PHYSICAL-PROPERTIES OF THE NEW LAYERED LANTHANIDE ALKALINE-EARTH COBALT OXIDES [LN2MCO2O7 (LN=SM,GD M=SR,BA)]

Three new oxides Sm2SrCo2O7, Sm2BaCo2O7 and Gd2SrCo2O7 have been successfully synthesized by a solid state reaction method.The X - Ray diffraction spectra show that they are all isostructural with Sr8Ti 2O7, Ln2SrCo2O7(Ln=Sm, Gd) crystallized in the tetra

THE DEHYDRATION BEHAVIOR OF RARE-EARTH COMPLEXES OF M-NITROBENZOIC ACID

Rare earth complexes of m-nitrobenzoic acid (LnL3.2H2O, Ln = La-Lu and Y, except Pm, HL = m-nitrobenzoic acid) were synthesized and characterized by elemental analysis, chemical analysis, IR spectroscopy and X-ray diffraction analysis. The dehydration beh

ELECTROCATALYTIC OXIDATION AND AMPEROMETRIC DETERMINATION OF SULFHYDRYL COMPOUNDS AT A COPPER HEXACYANOFERRATE FILM GLASSY-CARBON ELECTRODE IN LIQUID-CHROMATOGRAPHY

Electrocatalytic oxidation of sulfhydryl compounds was effective on a copper hexacyanoferrate (CuHCF) film glassy carbon electrode, at a significantly reduced overpotential (0.55 to 0.65 V) and for a broader pH range (2.0 to 7.0). The electrocatalysis was

RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN WITH RARE EARTH-CONTAINED CATALYSTS

Rare earth trifluoroacetates, Ln(CF3CO2)(3) (Ln = thirteen rare earth elements), combined with R(n)AlH(3-n) (R = methyl, octyl, n = 3; R = ethyl, i-Butyl, n = 2, 3) were used as catalysts for the polymerization of tetrahydrofuran (THF). The activity increased by adding propylene oxide (PO), as a promoter, to the polymerization system, producing high molecular weight polytetrahydrofuran (PTHF). The effects of Ln, PO/Ln, and Al/Ln, and others on the polymerization of THF were also studied. (C) 1993 John Wiley & Sons, Inc.

RARE-EARTH ION-SELECTIVE ELECTRODES

In this article, we report the rare earth ion selective electrodes developed in our laboratory. Rare earth containing functional copolymers, rare earth oxides, and chelates have been used as active materials. Methods for preparing raw materials, behavior of electrodes, and application of rare earth ion selective electrodes in flow injection analysis have been discussed as well.

SYNTHESES, CHARACTERIZATION AND CRYSTAL-STRUCTURES OF THE COMPLEXES OF RARE-EARTH WITH O-CHLOROBENZOIC ACID

REL3.H2O (RE=Y, La is similar to Lu; HL = o-chlorobenzoic acid) were synthesized. Their thermal decomposition and IR spectra were studied. The crystal structures of the complexes of neodymium, terbium and lutetium were determined by X-ray diffraction method. They crystallize in the monoclinic space group P2(1)/n and show infinite chain structures. The coordination numbers of rare earth ions are nine.