XANES at Eu-L-3 edge and valence of europium in SrB4O7 : EU and BaB8O13 : Eu

The luminescent materials SrB4O7:Eu and BaB8O13:Eu were synthesized, and the valence states of europium in the materials were measured by means of XANES at Eu-L-3 edge. It is found that the Ed(3+) and Eu2+ ions are all present in the materials, and more Eu3+ ions can be reduced in SrB4O7:Eu than in BaB8O13:Eu. The excitation and emission spectra of Eu3+ in SrB4O7:Eu and BaB8O13:Eu were determined.

Synthesis, electrochemistry, and photophysics of a novel binuclear polypyridyl Ru ( II ) complex with an 1,8-adipoylamido-bis(1, 10-phenanthroline-5-yl) ligand

The present paper covers the syntheses of 1,8-adipoylamido-bis(1,10-phenanthroline-5-yl)(bphaa) and its binuclear complex {[(bpy)(2)Ru](2)(bphaa)} (PF6)(4), where bpy is 2,2'-bipyridine. The two novel compounds were confirmed by means of elemental analysis, IR, and LD-MS and H-1 NMR, and H-1 NMR spectra were completely assigned in virtue of H-1-H-1 COSY. chemical behavior of the binuclear Ru (I) complex was obtained using cyclic and voltammetry. Its photophysical property was investigated by electronic absorption, excitation and emission spectra.

Optical spectroscopy properties and charge compensation of BaLiF3 doped with Ce3+

The excitation and emission spectra of the BaLiF3:Ce3+ phosphors synthesized through solid state reaction have been measured. By investigating the properties of the excitation spectra we point out that the variation in the excitation spectra with the amount of CeF3 dopant results from the different patterns of charge compensation in the matrices. The vacancies of Li+ ions are the favorable charge compensation pattern at low concentration of CeF3 doped, but interstitial F- ions are the major charge compensation pattern when the concentration of CeF3 doped goes beyond a certain value. (C) 2000 Academic Press

Vibronic transitions and site substitution of Eu2+ and codoped ions in KMgF3 : Eu-X (X=Ce, Cr, Gd, Cu) system

The high-resolution emission spectra of KMgF3 : Eu and KMgF3 : Eu-X(X = Ce, Cr, Gd, Cu) single crystals were measured at 300 and 77 K. The vibronic side bands of Eu2+ were characterized and an assignment of the normal mode frequencies to particular vibrations has been made. The correlation between the vibronic frequencies of Eu2+ and the site substitution of other co-dopcd ions was first found. The relationship between vibronic intensity of Eu2+ and other doped ions concentration showed that Cr3+, Gd3+ ions competed K+ sites with Eu2+ ions. Ce3+ and Eu3+ occurred the electron transference. The introduction of Cu+ made for Eu2+ substuting for K+ sites.

Site substitution and energy transfer of Eu2+ and Ce3+ in KMgF3 : Eu and KMgF3 : Eu-Ce single crystals

The high-resolution emission spectra of KMgF3 : Eu and KMgF3 : Eu-Ce single crystals were measured at 77 K. The site substitution of Eu2+ and Eu2+-Ce3+ co-doped system in KMgF3 was discussed. Eu2+ substituted for K+ sites on three different site-symmetry: cubic, trigonal and tetragonal. The attribution of all lines occurring in the emission spectra were ascertained. The indirect energy transfer from P-6(5/2) states of Eu2+ to 4f5d states of Ce3+ in KMgF3 : Eu-Ce was observed and the energy transfer mechanism was studied. The d-d interaction among levels was proposed.

The luminescence of the phosphor Sr2ZrO4 with one-dimensional chains structure

A new type of phosphor Sr2ZrO4 with one-dimensional structure was prepared by solid reaction and its luminescence is seen at room temperature. The excitation and emission spectra were measured and display broad maximum at 354 nm and 386 nm respectively. The mechanism of this luminescence is ascribed to charge transfer.

The site symmetry of Eu3+ in ZnS : Eu nanoparticle

Nanosized ZnS doped with different concentrations of Eu3+ were prepared and analyzed by x-ray diffraction technique. The experimental results show that ZnS belongs to the cubic structure. From the photoluminescence (PL) emission spectra, it can be seen that the ratio of the emission intensity of Eu3+ 616 nm to that at 590 nm increases as the increasing of Eu3+. This phenomenon reveals that the site symmetry of Eu3+ reduces as the increasing of Eu3+.

Electrochemical growth and characterization of polyoxometalate-containing monolayers and multilayers on alkanethiol monolayers self-assembled on gold electrodes

A general strategy has been developed for fabrication of ultrathin monolayer and multilayer composite films composed of nearly all kinds of polyoxometalates (POMs), including isopolyanions (IPAs), and heteropolyanions (HPAs). It involves stepwise adsorption between the anionic POMs and a cationic polymer on alkanethiol (cysteamine and 3-mercaptopropionic acid) self-assembled monolayers (SAMs) based on electrostatic interaction. Here a Keggin-type HPA SiMo11VO405- was chosen as a main representative to elucidate, in detail, the fabrication and characterization of the as-prepared composite films. A novel electrochemical growth method we developed for film formation involves cyclic potential sweeps over a suitable potential range in modifier solutions. It was comparatively studied with a commonly used method of immersion growth, i.e., alternately dipping a substrate into modifier solutions. Growth processes and structural characteristics of the composite films are characterized in detail by cyclic voltammetry, UV-vis spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), micro-Fourier transform infrared reflection-absorption spectroscopy (FTIR-RA), and electrochemical quartz crystal microbalance (EQCM). The electrochemical growth is proven to be more advantageous than the immersion growth. The composite films exhibit well-defined surface waves characteristic of the HPAs' redox reactions. In addition, the composite films by the electrochemical growth show a uniform structure and an excellent stability. Ion motions accompanying the redox processes of SiMo11VO405- in multilayer films are examined by in situ time-resolved EQCM and some results are first reported. The strategy used here has been successfully popularized to IPAs as well as other HPAs no matter what structure and composition they have.

The change of Eu3+-surroundings in the system Al2O3-B2O3 containing Eu3+ ions

The change of Eu3+-surroundings with the Al/B ratio varying from 4.5 to 2 and Eu/(Al + B) = 0.02, was investigated through X-ray diffraction, infrared spectra, excitation and emission spectra, and phonon sideband. The results show coexistence of the crystal phase Al18B4O33 and the amorphous phase and Eu3+ ions of the samples with the Al/B ratio from 3 to 2 are incorporated into the amorphous phase. It was also found that electron-phonon coupling strength decreases with the Al/B ratio from 3 to 2, non-radiative decay rate decreases, resulting in an increase of the Eu3+-emission intensity. (C) 1999 Elsevier Science Ltd. All rights reserved.

Crystallization kinetics of poly(ether ether ketone) (PEEK) from its metastable melt

After isothermal crystallization of the amorphous poly(ether ether ketone), double endothermic behaviour can be found through differential scanning calorimetry experiments. During the heating scan of semicrystalline PEEK, a metastable melt, which comes from the melt of the thinner lamellar crystal populations, can be obtained between these two endotherms. The metastable melt can recrystallize immediately just above the lower melting temperature and form slightly thicker lamellae than the original ones. The thickness and the perfection depend upon the crystallization time and the crystallization temperature. By comparing the TEM morphological observations of the samples before and after partial melting, it can be shown that lamellar crystals, having different thermodynamic stability, form during isothermal crystallization. After partial melting, only the type of lamellar crystal exhibiting the higher thermodynamic stability remains. Wide angle X-ray diffraction measurements shows a slightly change in the crystallinity of the samples before and after the partial melting. Small angle X-ray scattering results exhibit a change in the long period of the lamellar crystals before and after the partial melting process. The crystallization kinetics of the metastable melt can be determined by means of differential scanning calorimetry. The kinetic analysis showed that the isothermal crystallization of the metastable PEEK melt proceeds with an Avrami exponent of n = 1.0 similar to 1.4, reflecting that probably one-dimensional or an irregular line growth of the crystal occurred between the existing main lamellae with heterogeneous nucleation. (C) 1998 Elsevier Science Ltd. All rights reserved.

Multilayer assemblies of colloidal ZnS doped with silver and polyelectrolytes based on electrostatic interaction

Multilayer assemblies of silver doped ZnS colloid and polycation were fabricated by a self-assembly technique exploiting electrostatic interaction. UV/Vis spectra showed the uniform deposition process and X-ray photoemission spectroscopy (XPS) confirmed the coexistence of silver. It was found that the emission spectra of the silver doped ZnS colloid red-shifted to 528 nm comparing with undoped ZnS colloid. However, the most important finding was that the luminescence intensity of doped ZnS assembled in films was much stronger than that of undoped ZnS in films and that of doped ZnS in the spin-casting film. The mechanism of the enhancement luminescence was discussed. (C) 1998 Elsevier Science S.A. All rights reserved.

Structure, luminescence and magnetic properties of AgLnW(2)O(8) (Ln = Eu, Gd, Tb and Dy) compounds

Four new compounds AgLnW(2)O(8) (Ln = Eu, Gd, Tb and Dy) are prepared by solid-state reactions. They crystallize with a scheelite-related monoclinic symmetry. Infrared (IR) spectra show complicated absorption transitions in the region of 1000-400 cm(-1) that are similar to those of AgLnMo(2)O(8). Broad excitation and emission bands of the tungstate group are observed in AgGdW2O8 and AgTbW2O8 with a large Stokes shift, 12 573 and 12 387 cm(-1), respectively. Excitation and emission spectra of AgLnW(2)O(8) (Ln = Eu, Gd and Tb) show that energy transfer from the tungstate to EU3+, Gd3+ and Tb3+ occurs and that Eu3+ ions occupy a single crystallographic site with the C-2 Site symmetry. (C) 1997 Elsevier Science Ltd. All rights reserved.

Application of digital image analysis to the study of banded spherulite during growing and melting process

A digital image analysis(DIA) technique can be applied directly to the image obtained by polarizing microscope. The time-resolved DIA apparatus including image collecting, showing and data analysis has been home-made. As an example, it has been used to study the banded spherulite in the blends of poly(epsilon-caprolactone) (PCL) and poly(styrene-ran-acrylonitrile) (SAN).

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.

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.