Robust core-shell supramolecular assemblies based on cationic vesicles and ring-shaped {Mo-154} polyoxomolybdate nanoclusters: Template-directed synthesis and characterizations

Substantial progress has been made recently in extending the supramolecular assembly of biomimetic structures to vesicle-based sophisticated nanocomposites and mesostructures. We report herein the successful preparation of unilamellar surfactant vesicles coated with a monolayer of ring-shaped {Mo-154} polyoxometalate (POM) nanoclusters, (NH4)(28)[Mo-154 (NO)(14)O(448)Hi(4)(H2O)(70)].approximate to 350H(2)O, by coulomb attractions using preformed didodecyldimethylammonium bromide (DDAB) surfactant vesicles as templates. The resultant vesicle-templated supramolecular assemblies are robust (they do not disintegrate upon dehydration) both at room-temperature ambient and vacuum conditions, as characterized by conventional transmission electron microscopy (TEM) and atomic force microscopy (AFM). The flexibility of the complex soft assemblies was also revealed by AFM measurements. The effect of POM-vesicle coulomb attractions on the dimensions of the templating vesicles was also investigated by using dynamic light scattering (DLS).Although origins of the structure stability of the as-prepared supramolecular assemblies are not clear yet, the nanometer scale cavities and the related properties of macroions of the POM clusters may play an important role in it.

Hydrothermal synthesis and crystal structure of a sulfur-bridged binuclear copper(II) coordination polymer generated by a spontaneous reduction

A simultaneous reduction SO42- to S2- by 2,5-pyridinedicarboxylate under hydrothermal conditions produced a new binuclear copper(II) coordination polymer [CuS(4,4'-bipy)](n) (4,4-bipy = 4,4'-bipyridine) (1). Single crystal X-ray analysis revealed that compound I consisted of sulfur-bridged binuclear copper(II) units with Cu-Cu bonding which were combined with 4,4-bipy to generate a three-dimensional network constructed from mutual interpenetration of two-dimensional (6,3) nets. Crystal data for 1:C10H8CuN2S, tetragonal 14(1)/acd, a = 14.0686(5) Angstrom, b = 14.0686(5) Angstrom, c = 38.759(2) Angstrom, Z = 32. Other characterizations by elemental analysis, IR, EPR and TGA analysis were also described in this paper.

Synthesis and luminescence properties of Gd2O3 : Eu3+ phosphors

Gd2O3: EU3+ phosphors were prepared by urea homogeneous precipitation with different surfactant and sol-gel method. XRD patterns show that all the obtained samples are in cubic Gd2O3, and the results of FTIR and fluorescent spectra conformed that OP is a good surfactant for preparing the Gd2O3: Eu3+ phosphors. The SEM photographs show that the particles prepared by urea homogeneous precipitation method are all spherical and well-dispersed, and grain morphology can be controlled by different surfactant. XRD and SEM indicate that the particle sizes prepared by sol-gel method are in the range of 5 similar to 30 nm, and the grain sizes increase with increasing of heated temperatures. Luminescence spectra indication that the main emission peaks of all samples are at 610 nm, the intensities are different from samples prepared with different surfactant and the luminescence intensities increase with increasing of annealed temperatures.

Synthesis and characterization of Tb3+ trimesic acid fluorescence system

The luminescent complex of Tb3+-trimesic acid was synthesized in an alcohol and water mixed solvent. The chemical components of the complex TbL.5H(2)O was characterized by the element analysis, thermal analysis and FTIR. The results of the XRD patterns and SEM photographs indicate that the complex is composed of a lot of bar-shaped crystal grain with 5 similar to 10 mum long. The results of the photoluminescence show that the complex emitted the characteristic green fluorescence of Tb3+.

Synthesis and photoluminescence of the Y2O3 : Eu3+ phosphor nanowires in AAO template

The monodisperse array and nanowires Of Y2O3:Eu3+ phosphor were synthesized using anodic aluminum oxide (AAO) template by sol-gel method. Scanning electron microscope (SEM) images indicated that Y2O3:Eu3+ nanowires are parallelly arranged, all of which are in uniform diameter of about 50 nm. The high-magnification SEM image showed that each nanowire is composed of a lot of agglutinating particles. The patterns of selected-area electron diffraction confirmed that Y2O3:EU3+ nanowires mainly consist of polycrystalline materials. Excitation and emission spectra Of Y2O3:E U3+/AAO composite films were measured. The characteristic red emission peak of EU3+ ion attributed to D-5(0)-->F-7(2) transition in Y2O3:EU3+/AAO nanowires broadened its halfwidth.

Synthesis and characterization of SiO2/Gd2O3 : Eu core-shell luminescent materials

Europium-doped Gd2O3 with an average size of similar to15 nm was coated on the surface of preformed silica nanospheres by the wet chemical method. SEM and TEM photographs showed that SiO2/Gd2O3:Eu core-shell submicrospheres are obtained. XRD patterns indicated that the Gd2O3:Eu shell is crystalline after heat treatment. FTIR and XPS spectra showed that the Gd2O3:Eu shell is linked to the silica surface by forming a Si-O-Gd bond. Photoluminescence studies showed that the luminescent properties are still retained after coating on an inert silica core; additionally, we noted that the emitting peaks are broadened, which results from size effects and interface effects of nanocrystal.

Synthesis and chirooptical properties of optically active poly(ester imide)s based on axially asymmetric 1,1 '-binaphthyls

A series of optically active poly(ester imide)s (PEsI's) has been synthesized by the polycondensation reactions of new axially asymmetric dianhydrides, that is, (R)-2,2'-bis(3,4-dicarboxybenzoyloxy)-1,1'-binaphthyl dianhydride and (S)-2,2'-bis(3,4-dicarboxybenzoyloxy)-1,1'-binaphthyl dianhydride, and various diamines with aromatic, semiaromatic, and aliphatic structures. The polymers have inherent viscosities of 0.45-0.70 dL/g, very good solubility in common organic solvents, glass-transition temperatures of 124-290 degreesC, and good thermal stability. Wide-angle X-ray crystallography of these polymers shows no crystal diffraction. In comparison with model compounds, an enhanced optical rotatory power has been observed for the repeat unit of optically active PEsI's based on aromatic diamines, and it has been attributed to a collaborative asymmetric perturbation of chiral 1,1'-binaphthyls along the rigid backbones.

Synthesis and properties of novel polyimides derived from 2,2 ',3,3 '-benzophenonetetracarboxylic dianhydride

A new synthetic route to 2,2',3,3'-BTDA (where BTDA is benzophenonetetracarboxylic dianhydride), an isomer of 2,3',3',4'-BTDA and 3,3',4,4'-BTDA, is described. Single-crystal X-ray diffraction analysis of 2,2',3,3'-BTDA has shown that this dianhydride has a bent and noncoplanar structure. The polymerizations of 2,2',3,3'-BTDA with 4,4'-oxydianiline (ODA) and 4,4'-bis(4-aminophenoxy)benzene (TPEQ) have been investigated with a conventional two-step process. A trend of cyclic oligomers forming in the reaction of 2,2',3,3'-BTDA and ODA has been found and characterized with IR, NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and elemental analyses. Films based on 2,2',3,3'-BTDA/TPEQ can only be obtained from corresponding polyimide (PI) solutions prepared by chemical imidization because those from their polyamic acids by thermal imidization are brittle. PIS from 2,2',3,3'-BTDA have lower inherent viscosities and worse thermal and mechanical properties than the corresponding 2,3',3',4'-BTDA- and 3,3',4,4'-BTDA-based PIs. PIs from 2,2',3,3'-BTDA and 2,3',3',4'-BTDA are amorphous, whereas those from 3,3',4,4'-BTDA have some crystallinity, according to wide-angle X-ray diffraction.

Synthesis and properties of polyimides derived from cis- and trans-1,2,3,4-cyclohexanetetracarboxylic dianhydrides

Cis-1,2,3,4-cyclohexanetetracarboxylic dianhydride (cis-1,2,3,4-CHDA) was synthesized. It was found that under such conditions as heating or boiling in acetic anhydride, cis-1,2,3,4-CHDA could be converted to its trans-isomer. The process of thermal isomerization was monitored by H-1 NMR spectra and the mechanism of conversion was proposed. Their absolute structures of cis- and trans-1,2,3,4-CHDAs were elucidated by single crystal X-ray diffraction. The polycondensations of cis- and trans-1,2,3,4-CHDAs with aromatic diamines such as 4,4'-oxydianiline (ODA), 4,4'-methylenedianiline (MDA), 4,4'-diamino-3,3'-dimethyldiphenylmethane (DMMDA), 4,4'-bis(4-aminophenoxy)benzene (TPEQ), 2,2-bis[4-(4-aminophenoxy)phenyl] propane (BAPP) were studied. It is easy to obtain higher molecular weight polyimides from trans-1,2,3,4-CHDA using conventional one-step or two-step methods. However, higher molecular weight polyimides derived from cis-1,2,3,4-CHDA could not be prepared by the usual methods (solid content ca. 10%) owing to the trend of forming cyclic oligomers.

Synthesis and catalytic application of chiral 1, 1 '-binaphthyl polymers

The synthesis of a new type of polymers with main chain chirality based on BINOL skeleton is described. Titanium-BINOLate catalysts are easily generated from these polymers and applied to the asymmetric reaction of Et2Zn with benzaldehyde. The products are obtained in good yields with moderate enantioselectivities.

Synthesis and properties of polyquinolines and polyanthrazolines containing pyrrole units in the main chain

A series of eight new polyquinolines and polyanthrazolines with pyrrole isomeric units in main chain were synthesized and characterized. The new polymers showed high glass transition temperatures (T-g = 242-339 degreesC) and excellent thermal stability (T-5% = 398-536 degreesC in air, TGA). Compared to the series of polyanthrazolines, the series of polyquinolines exhibited higher thermal stability, better solubility in common organic solvents, and lower maximum absorption wavelengths (lambda(max)(a)). Polyanthrazolines with 2,5-pyrrole linkage showed an unusually high lambda(max)(a) (565 nm) and small band gap (2.02 eV). All polymers in solution had low photoluminescence quantum yields between 10(-2%) and 10(-5%) and excited-state lifetimes of 0.28-1.29 ns. The effects of molecular structure, especially pyrrole linkage structures, on the electronic structure, thermodynamics, and some of the optical properties of the polymers were explored. A model of hydrogen bonds in the main chain of the polymers was suggested to explain the difference in the properties of the isomer polymers. In addition, a polyquinoline (PBM) was chosen to examine the proton conductivity; the result indicated that the PBM/H3PO4 complex exhibited a high conductivity of 1.5 x 10(-3) S cm(-1) at 157 degreesC.

Synthesis and characterization of beta-diketiminate terbium complex

The terbium complex supported by beta-diketiminate was synthesized and structurally characterized. Due to an efficient energy transfer from the ligand to the central Tb3+, this complex shows a strong emission corresponding to Tb3+5D4-F-7(J) (J = 6,5,4,3) transitions, with D-5(4)-F-7(5) (550 nm) green emission as the most prominent group. The decay behavior of Tb3+ luminescence depends strongly on the excitation wavelengths.

Citrate-gel synthesis and luminescent properties of alpha-Zn-3(PO4)(2) doped with Eu3+

By using inorganic salts as raw materials and citric acid as complexing agent, alpha-Zn-3(PO4)(2) and Eu3+ doped alpha-Zn-3(PO4)(2) phosphor powders were prepared by a citrate-gel process. X-ray diffraction, (XRD), TG - DTA, FT - IR and luminescence excitation and emission spectra were used to characterize the resulting products. The results of XRD reveal that the powders begin to crystallize at 500 degreesC and pure alpha-Zn-3(PO4)(2) phase is obtained at 800 degreesC. And the results of XRD reveal that Eu3+ exists Lis EoPO(4) ill the powder. In the phosphor powders, the Eu3+ shows its characteristic red-orange (592 nm, D-5(0) - F-7(1)) emission and has no quenching concentration.

Synthesis and characterization of Y0.9-xGdxEu0.1BO3 phosphors by spray drying process

Y0.9-xGdxEu0.1BO3 phosphors were synthesized by spray drying (SD) method, and the results were compared with those by conventional solid state (SS) and citrate gel (GC) methods. The PL intensity of phosphors increases with the increase of x value in Y0.9-xGdxEu0.1BO3 (prepared by SD) due to an energy migration process like Gd3+ - (Gd3+)(n) - Eu3+ occurred in the material. Compared with the latter two methods, the phosphor particles prepared by spray drying method have a better morphology, such as homogeneous size (about 1similar to3 mum) with spherical shape and smooth surface. Furthermore, the spray drying-derived phosphors have higher photoluminescence (PL) intensity than those by citrate gel method, but still a little lower than those by the solid state method.

The synthesis and catalytic activity of poly(bis(imino)pyridyl) iron(II) metallodendrimer

The first and second generation carbosilane dendrimers with silicon hydride terminated were synthesized, and then reacted with bis(imino)pyridyl containing allyl [4-CH2==CHCH2-2,6-(Pr2C6H3N)-Pr-i==CMe(C5H3N)MeC==N(2,6-'Pr2C6H3)], in the presence of H2PtCl6 as a hydrosilylation catalyst, to afford the first and second generation carbosilane supported ligands. Complexation reactions with FeCl(2)(.)4H(2)O give rise to iron-containing carbosilane dendrimers with FeCl2 moieties bound on the periphery. The metallodendrimers were used as catalyst precursors, activated with modified methylaluminoxane, for the polymerization of ethylene. In the case of low Al/Fe molar ratio, the metallodendrimers display much higher catalytic activity towards ethylene polymerization and produce much higher molecule weight polyethylenes than the corresponding single-nuclear complex under the same conditions.