Layer-by-layer multilayer films self-assembled from a rare-earth-containing poly-oxometalate Na-9[Eu(W5O18)(2)] and poly (allylamine hydrochloride) and their photoluminescent properties

Ultrathin multilayer films of a rare-earth-containing polyoxometalate Na-9[Eu(W5O18)(2)] (EW) and Poly (allyamine hydrochloride) (PAH) have been prepared by layer-by-layer self-assembly from dilute aqueous solutions. The fabrication process of the EW/PAH multilayer films was followed by UV-vis spectroscopy and ellipsometry, which show that the deposition process is linear and highly reproducible from layer to layer. An average EW/PAH bilayer thickness of ca. 2.1 nm was determine,by ellipsometry. In addition, the scanning electron microscopy (SEM) image of the EW/PAH film indicates that the film sufface is relatively uniform and smooth. The photoluminescent properties of these films were also investigated by fluoresence spectroscopy.

Preparation and luminescence properties of the mesoporous MCM-41s intercalated with rare earth complex

Rare earth complex Eu(DBM)(3)phen (DBM: dibenzoylmethane, phen: 1.10-phenanthroline) hits been incorporated into unmodified MCM-41 and modified MCM-41s by aminopropyltriethoxysilane (APTES) or N-[(3-triethoxysilyl)propyl]ethylenediamine(TEPED). Thus, the assemblies of unmodified or modified MCM-41s with rare earth (RE) complex have been obtained. XRD spectra. NMR spectra. diffuse reflectance spectra. and the luminescence spectra were used to characterize the pure RE complex and the corresponding assemblies. The assemblies have better luminescence properties under UV irradiation. and their fluorescence lifetimes on the excited state are longer than that of the corresponding pure complex. The possible mechanisms are also discussed in the context.

Synthesis and crystal structure of cyclopentylindene rare earth complex (C5H9C9H6)(3)SMCl-Li+ (THF)(4)

Rare earth complex (C5H9C9H6)(3)SmCl-Li+ (THF)(4)( I ) was synthesized by reacting anhydrous SmCl3 with two equivalents of C5H9C9H6Li. From mix-solvent of THF and hexane, red color single crystals were obtained. The crystal belongs to a cubic system, space group P2(1)3 with unit cell parameters a= b=c= 1. 754 0(2) nm, alpha=beta=gamma=90degrees, V=5. 396 4(11) nm(3), Z = 4. The ten-coordinated samarium atom is bonded to three cyclopentylindenyl rings and a chlorine atom to form the anionic part of the title complex, ring centroids and the chlorine atom form a tortured tetrahedron around samarium. In the cationic part, lithium atom coordinates to four oxygen atoms of THF molecules to form a normal tetrahedron. The Sm-C(within the same ring) distance varies from 0. 268 to 0. 299 nm.

Photoluminescent organic-inorganic composite films layer-by-layer self-assembled from the rare-earth-containing polyoxometalate Na-9[EuW10O36] and poly(allylamine hydrochloride)

Photoluminescent organic-inorganic composite films incorporating the rare-earth-containing polyoxometalate Na-9[EuW10O36] (EW) and poly(allylamine hydrochloride) (PAH) have been prepared by the layer-by-layer self-assembly method. UV-vis spectroscopy and ellipsometry were used to follow the fabrication process of the EW/PAH composite films. The experimental results show that the deposition process is linear and highly reproducible from layer to layer. An average EW/PAH bilayer thickness of ca. 2.1 nm was determined by ellipsometry. In addition, scanning electron microscopy and atomic force microscopy images of the EW/PAH composite films indicate that the film surface is relatively uniform and smooth. The photoluminescent properties of these films were investigated by fluorescence spectroscopy.

Sol-gel deposition and luminescent properties of oxyapatite Ca-2(Y,Gd)(8)(SiO4)(6)O-2 phosphor films doped with rare earth and lead ions

Rare-earth and lead ions (Eu3+, Tb3+, Dy3+, Pb2+) doped Ca2Y8 (SiO4)(6)O-2 and Ca2Gd8(SiO4)(6)O-2 thin films have been dip- coated on silicon and quartz glass substrates through the sol- gel route. X- Ray diffraction (XRD), TG- DTA, scanning electron microscopy (SEM), atomic force microscopy (AFM), FT- IR and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resulting films. The results of XRD reveal that these films remain amorphous below 700 degreesC, begin to crystallize at 800 degreesC and crystallize completely around 1000 degreesC with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM and AFM micrographs, where particles with various shapes and average size of 250 nm can be resolved. Eu3+ and Tb3+ show their characteristic red (D-5(0)-F-7(2)) and green (D-5(4) - F-7(5)) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime and emission intensity of Eu3+ increase with the temperature treatment from 700 to 1100 degreesC, while those of Tb3+ show a maximum at 800 degreesC. Energy transfer phenomena have been observed by activating the oxyapatite film host- lattice Ca2Gd8(SiO4)(6)O-2 with Tb3+ (Dy3+). In addition, Pb2+ can sensitize the Gd3+ sublattice in Ca2Gd8(SiO4)(6)O-2.

Preparation, patterning and luminescence properties of rare earth-doped YVO4 nanocrystalline phosphor films via sol-gel soft lithography

In this presentation, nanocrystalline YVO4:A (A=Eu3+, Dy3+, SM3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography (micro-molding in capillaries). XRD, FT-IR, AFM and optical microscope, absorption spectra, photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 400 degrees C and the crystallinity increased with the increase of annealing temperatures. Transparent nonpattemed phosphor films were uniform and crack free, which mainly consisted of grains with an average size of 90nm. Patterned crystalline phosphor film bands with different widths (5-30 mu m) were obtained. The doped rare earth ions (A) showed their characteristic emission in crystalline YVO4 phosphor films due to an efficient energy transfer from vanadate groups to them. The Sm3+ and Er3+ ions also showed upconversion luminescence in YVO4 film host. The optimum concentration for Eu3+ was determined to be 7 mol% and those for Dy3+, Sm3+, Er3+ were 2 Mol% of Y3+ in YVO4 films, respectively.

Preparation, characterization and photophysical properties of layered zirconium bis(monohydrogenphosphate) intercalated with rare earth complexes

Two kinds of rare earth (RE) complexes were intercalated into zirconium bis(monohydrogenphosphate) (alpha -ZrP) by exchanging the RE complexes into the p-methyoxyaniline (PMA) preintercalated compound Zr(O3POH)(2). 2PMA (alpha -ZrP . 2PMA). Powder X-ray diffraction patterns reveal that Eu(DBM)(3)phen (DBM: dibenzoylmethane, phen: 1,10-phenanthroline) and Tb(AA)(3)phen (AA: acetylacetone) intercalated into alpha -ZrP . 2PMA. This was confirmed by the UV-visible spectra of both the RE complexes and the assemblies. At the same time, the assemblies have better luminescent properties, and the fluorescent lifetimes of RE3+ in the excited state in the assemblies are much longer than those in the complexes. The stabilities of the assemblies under UV radiation are much better than those of the RE complexes.

Species of rare earth (III), calcium (II) and zinc (II) in the presence of L-histidine and L-typtophane

Rare earth(III)-histidine (His)- tryptophane (Trp). Ca(II)-His-Trp and Zn(II)-His-Trp systems were studied by potentiometric titration and computer simulation under physiological conditions. The species of the systems and their stability constants were determined. The distributions of species of rare earth(III), Ca(II) and Zn(II) were discussed.

Preparation and characterization of luminescent thin films doped with rare earth (Tb3+, Eu3+) complexes derived from a sol-gel process

Sol-gel derived luminescent thin films doped with rare earth (RE) complexes were prepared using an in-situ synthesis method with a two-step hydrolysis process and the luminescence spectra were measured. Fluorescence Lifetime and thermal stability were investigated. The results show that a broad excitation band indicates the formation of RE complexes in the solid thin films. RE ions, which are restrained in a silica matrix, present longer lifetime and higher thermal stability than that in DMF/PVB films containing the corresponding pure complexes. (C) 2000 Elsevier Science B.V. All rights reserved.

Synthesis, characterization, stability and relaxation behaviours of rare earth heteropolymetalates

Two rare earth heteropolymetalates K9GdW10O36 and K-11[Gd(PW11O39)(2)] have been synthesized and characterized by IR and elemental analysis. Their stability has been studied by TG - DTA. The TG - DTA analysis show that both complexes are of good thermal stability. Their relaxivity in D2O is 6.89 and 5.27 mmol(-1).s(-1) respectively. Interaction with BSA has also been investigated. The results indicate that the two rare earth heteropolymetalate may be potential contrast agent for MRI.

Preparation of borates doped with divalent rare earth ions (RE2+) in air and spectroscopy of divalent rare earth ions (RE2+ = Sm, Eu, Tm, Yb)

The spectroscopic feature of divalent Sm2+, Eu2+, Tm2+ and Yb2+ is discussed in this paper. Especially the spectroscopic properties of some berates containing tetrahedral BO4 group such as SrB4O7, SrB6O10 and BaB8O13 doped with these divalent ions are reported. When the divalent alkaline earth ion in these berates is replaced partially by the above trivalent rare earth ion, the charge carried in the produced defects can be used as reductant to reduce the doped rare earth ion into divalent state at high temperature even in air. Therefore, a convenient and safe method is provided to prepared phosphors doped with these divalent rare earths.

Preparation and characterization of layered compound zirconium bis(monohydrogenphosphate)intercalated with rare earth complex

Layered compound zirconium bis(monohydrogenphosphate)(alpha-ZrP) intercalated with rare earth complex Eu(DBM)(3)phen was prepared. The pre-intercalation of p-methoxyaniline into alpha-ZrP makes the interlayer separation large enough to exchange PMA with europium complex, thus, the luminescent assembly was prepared. This was confirmed by X-ray diffraction, UV-visible spectra and elemental analysis. The fluorescence spectra and lifetime of the assembly were also presented.

Effects of rare earth ions and calmodulin on the activity of lactate dehydrogenase

In this paper, the effects of rare earth ions (La3+, Eu3+, Dy3+, Yb3+) and their complexes with calmodulin on the activity of lactate dehydrogenase (LDH) were investigated. The results reveal that whether binding with calmodulin or not, rare earth ions show a minor activation effects on LDH when their concentrations are less than 3 mu mol (.) L-1, but indicate some strong inhibitory effects on LDH activity when the concentrations are above 5 mu mol (.) L-1. Calmodulin, which is a calcium-dependent regulator, can stimulate LDH activity and release the inhibitory effects of rare earth ion. Diethylenetriamine pentaacetic acid(DTPA) and its derivatives bisdimethylamide-diethylenetriamine pentaacetic acid (DTPA-BDMA), bisisonicotinyl-diethylenetriamine pentaacetic acid (DTPA-BIN), which are often used as ligands to metal ions, inhibit LDH activity when their concentrations are above 5 mu mol (.) L-1. Calmodulin can also release their inhibitory effects at the same time.

Copolymerization of carbon dioxide and propylene oxide with Ln(CCl3COO)(3)-based catalyst: The role of rare-earth compound in the catalytic system

A highly alternative copolymer of carbon dioxide and propylene oxide was obtained using a lanthanide trichloroacetates-based ternary catalyst. The rare-earth compound in the ternary catalyst was critical to dramatically raise the yield and molecular weight of the copolymer in addition to maintaining a high alternating ratio of the copolymer. (C) 2001 John Wiley & Sons, Inc.

Preparation, characterization and luminescent properties of MCM-41 type materials impregnated with rare earth complex

Hybrid materials incorporating Eu-(TTA)(3). 2H(2)O (7hereafter designated as Eu-TTA, with TTA: thenoyltrifluoroacetone) in unmodified or modified MCM-41 by 3-aminopropyl-triethoxysilane (APTES) were prepared by impregnation method. The obtained materials were characterized using X-ray diffraction (XRD), IR and diffuse reflectance spectroscopy and luminescence spectra. All the hybrid samples exhibited the characteristic emission bands of EU3+ under UV light excitation at room temperature, and the excitation spectra showed significant blue-shifts compared to the pure rare-earth complex. Although the red emission intensity in the modified hybrid was almost the half of the red emission intensity in the pure Eu-TTA complex at room temperature, the hybrid showed a much higher thermal stability due to the shielding character of the MCM-41 host.