Eu3+, Tb3+, and Co2+ salts of polymers containing carboxylic acid and sulfonic acid ligands were prepared and characterized. The polymers investigated were poly(acrylic acid) (PAA), copolymers of styrene-acrylic acid (PSAA), styrene-maleic acid (PSM), and methyl methacrylate-methacrylic acid (PMM/MA), and partially carboxylated and sulfonated polystyrenes (CPS and SPS). The lanthanide salts of these polymers showed characteristic lanthanide ion fluorescence in the solid state on excitation with UV light. The fluorescence excitation and emission spectra of these salts excepting carboxylated polystyrene showed characteristic spectra of the free ions, indicating that no energy is transferred from the polymer matrix to the ions. The carboxylated polystyrene-Eu3+ and -Tb3+ showed broad excitation spectra similar to the spectrum of the polymer and emission from the lanthanide ions, suggesting energy transfer from the polymer to the ion. The fluorescence intensities of the lanthanide salts of PAA, PSM, CPS, and SPS were found to increase linearly with the metal ion content. However, the salts of PSAA and PMM/MA displayed typical fluorescence concentration quenching behavior, reaching a maximum at 4-6 wt % of metal and decreasing with further increases in metal content. These results suggest that PSAA and PMM/MA contain ionic aggregates in which Eu and Tb ions are located close together. The energy transfer from Tb3+ to Co2+ and Eu3+ was evaluated from the Tb3+ fluorescence quenching. This was much more efficient in PSAA than in CPS and SPS systems.These results confirm that ion aggregates exist in PMM/MA and PSAA but not in the CPS and SPS systems at low metal concentration (<6 mol %). The probability Pd~a of dipole-dipole transfer between Tb3+ and Co2+ statistically distributed in a polymer matrix and the quenching characteristics were calculated by using Forster's equation. Experimental fluorescence quenching behaviors for PASS, CPS, and SPS are discussed as compared with the calculated quenching curve.
.5Ti4O13 (I) is prepared by solid state reaction of KNO 3, Bi2O3, and TiO2 (Al2O3 crucible, 750 C, 16 h). Compound (I) crystallizes in the space group Bb21m (synchrotron powder X-ray and neutron powder diffraction) and consists of a quadruple-stacked (n = 4) perovskite layer with K occupying the rock salt layer and its next nearest A site. The hydrated form K 2.5Bi2.5Ti4O13·H2O crystallizes in the space group Pb2 1m and is shown to remove the offset between stacked perovskite layers relative to (I). Computational methods show that the hydrated phase consists of H2O molecules in a vertical "pillared" arrangement bridging across the interlayer space. In situ diffraction data for the dehydrated phase reveal a broad second-order structural phase transition from orthorhombic to tetragonal (space group I4/mmm) at 600 C. In situ dielectric measurements show the contribution of H 2O to the dielectric constant which disappears after dehydration. -(LIU*, S.; AVDEEV, M.; LIU, Y.; JOHNSON, M. R.; LING, C. D.; Inorg.
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