In(OH)(3) and In2O3 nanorod bundles and spheres: Microemulsion-mediated hydrothermal synthesis and luminescence properties

Indium hydroxide, In(OH)(3), nano-microstructures with two kinds of morphology, nanorod bundles (around 500 nm in length and 200 nm in diameter) and caddice spherelike agglomerates (around 750 - 1000 nm in diameter), were successfully prepared by the cetyltrimethylammonium bromide (CTAB)/water/cyclohexane/n-pentanol microemulsion-mediated hydrothermal process. Calcination of the In(OH)(3) crystals with different morphologies (nanorod bundles and spheres) at 600 degrees C in air yielded In2O3 crystals with the same morphology. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. The pH values of microemulsion play an important role in the morphological control of the as-formed In(OH)(3) nano-microstructures from the hydrothermal process. The formation mechanisms for the In( OH) 3 nano- microstructures have been proposed on an aggregation mechanism. In2O3 nanorod bundles and spheres show a similar blue emission peaking around 416 and 439 nm under the 383-nm UV excitation, which is mainly attributed to the oxygen vacancies in the In2O3 nano-microstructures.

Synthesis and structural characterization of beta-diketiminate-lanthanide Amides and their catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone

The synthesis and catalytic activity of lanthanide monoamido complexes supported by a beta-diketiminate ligand are described. Donor solvents, such as DME, can cleave the chloro bridges of the dinuclear beta-diketiminate ytterbium dichloride {[(DIPPh)(2)nacnac]YbCl(mu-Cl)(3)Yb[(DIPPh)(2)nacnac](THF)} (1) [(DIPPh)(2)nacnac = N,N-diisopropylphenyl-2,4-pentanediimine anion] to produce the monomeric complex [(DIPPh)(2)nacnac]YbCl2(DME) (2) in high isolated yield. Complex 2 is a useful precursor for the synthesis of beta-diketiminate-ytterbium monoamido derivatives. Reaction of complex 2 with 1 equiv of LiNPr2i in THF at room temperature, after crystallization in THF/toluene mixed solvent, gave the anionic beta-diketiminate-ytterbium amido complex [(DIPPh)(2)nacnac]Yb(NPr2i)(mu-Cl)(2)Li(THF)(2) (3), while similar reaction of complex 2 with LiNPh2 produced the neutral complex [(DIPPh)(2)nacnac]Yb(NPh2)Cl(THF) (4). Recrystallization of complex 3 from toluene solution at elevated temperature led to the neutral beta-diketiminate-lanthanide amido complex [{(DIPPh)(2)nacnac}Yb(NPr2i)(mu-Cl)](2) (5). The reaction medium has a significant effect on the outcome of the reaction.

Systematic synthesis and characterization of single-crystal lanthanide phenylphosphonate nanorods

Using low-temperature hydrothermal methods, nanoscale lanthanide phenylphosphonates species with different morphologies, namely, nanoparticles and nanorods, have been systematically synthesized. The possible growth mechanism of these nanorods was discussed. X-ray diffraction, transmission electron microscopy, electron diffraction, and photoluminescence spectra were used to characterize these materials. The photoluminescent properties of EU(O3PC6H5)(HO3PC6H5) and La0.91EU0.09(O3PC6H5)(HO3PC6H5) nanorods were discussed.

Synthesis and characterization of RGD peptide grafted poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-glutamic acid) triblock copolymer

Advances in tissue engineering require biofunctional scaffolds that can provide not only physical support for cells but also chemical and biological cues needed in forming functional tissues. To achieve this goal, a novel RGD peptide grafted poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-glutamic acid) (PEG-PLA-PGL/RGD) was synthesized in four steps (1) to prepare diblock copolymer PEG-PLA-OH and to convert its -OH end group into -NH2 (to obtain PEG-PLA-NH2), (2) to prepare triblock copolymer PEG-PLA-PBGL by ring-opening polymerization of NCA (N-carboxyanhydride) derived from benzyl glutamate with diblock copolymer PEG-PLA-NH2 as macroinitiator, (3) to remove the protective benzyl groups by catalytic hydrogenation of PEGPLA-PBGL to obtain PEG-PLA-PGL, and (4) to react RGD (arginine-glycine-(aspartic amide)) with the carboxyl groups of the PEG-PLA-PGL. The structures of PEG-PLA-PGL/RGD and its precursors were confirmed by H-1 NMR, FT-IR, amino acid analysis, and XPS analysis. Addition of 5 wt % PEG-PLA-PGL/RGD into a PLGA matrix significantly improved the surface wettability of the blend films and the adhesion and proliferation behavior of human chondrocytes and 3T3 cells on the blend films. Therefore, the novel RGD-grafted triblock copolymer is expected to find application in cell or tissue engineering.

Synthesis and surface morphology of tetraaniline-block-poly(L-lactate) diblock oligomers

Tetraaniline-block-poly(L-lactide) diblock oligomers are synthesized via ring-opening polymerization. The diblock oligomers cast from all L-lactide selective solvent (chloroform) show spherical aggregates for the leucoemeraldine state, and ring-like structures that are composed of much smaller spherical aggregates for the emeraldine state. The formation mechanisms of the two different surface morphologies are discussed in detail.

Synthesis and characterization of a novel biodegradable, thermoplastic polyurethane elastomer

A series of biodegradable, thermoplastic polyurethane elastomers poly (epsilon-caprolactone-co-lactide)polyurethane [PCLA-PU] were synthesized from a random copolymer Of L-lactide (LA) and epsilon-caprolactone (CL), hexamethylene diisocyanate, and 1,4-butanediol. The effects of the LA/CL monomer ratio and hard-segment content on the thermal and mechanical properties of PCLA-PUs were investigated. Gel permeation chromatography, IR, C-13 NMR, and X-ray diffraction were used to confirm the formation and structure of PCLA-PUs. Through differential scanning calorimetry, tensile testing, and tensile-recovery testing, their thermal and mechanical properties were characterized. Their glass-transition temperatures were below -8 degrees C, and their soft domains became amorphous as the LA content increased. They displayed excellent mechanical properties, such as a tensile strength as high as 38 MPa, a tensile modulus as low as 10 MPa, and an elongation at break of 1300%. Therefore, they could find applications in biomedical fields, such as soft-tissue engineering and artificial skin.

Synthesis and characterization of new carbazole/fluorene-based derivatives for blue-light-emitting devices

2,7-Bis(9-ethylcarbazol-3-yl)-9,9-di(2-ethylhexyl)fluorene and a segmented copolymer composed of the same chromophores alternated with hexamethylene fragments were synthesized. The obtained materials possess good solubility in common organic solvents, high thermal stability with 1% weight loss temperature of 350-370 degrees C, and suitable glass transition temperatures. Both derivatives show blue fluorescence in dilute solutions as well as in solid state, demonstrating that excimers are not formed in the thin films. The fluorescence spectra of the materials do not show any peaks in the long-wavelength region even after annealing at 200 degrees C in air. An organic LED with the configuration of ITO/copolymer/Al generates blue electroluminescence with the maximum peak at 416 nm, rather low turn-on voltage (4.0 V), and brightness of about 400 cd/m(2). The heterostructure device based on model derivative emitted stable blue light with low operation voltage (100 cd/m(2) at similar to 11 V) and demonstrated luminescence efficiency of 0.8 cd/A.

Crosslinkable poly(propylene carbonate): High-yield synthesis and performance improvement

A crosslinking strategy was used to improve the thermal and mechanical performance of poly(propylene carbonate) (PPC): PPC bearing a small moiety of pendant C=C groups was synthesized by the terpolymerization of allyl glycidyl ether (AGE), propylene oxide (PO), and carbon dioxide (CO2). Almost no yield loss was found in comparison with that of the PO and CO2 copolymer when the concentration of AGE units in the terpolymer was less than 5 mol %. Once subjected to UV-radiation crosslinking, the crosslinked PPC film showed an elastic modulus 1 order of magnitude higher than that of the uncrosslinked one. Moreover, crosslinked PPC showed hot-set elongation at 65 degrees C of 17.2% and permanent deformation approaching 0, whereas they were 35.3 and 17.2% for uncrosslinked PPC, respectively. Therefore, the PPC application window was enlarged to a higher temperature zone by the crosslinking strategy.

Sol-gel synthesis and characterization of SiO2@CaWO4, SiO2@CaWO4 : Eu3+/Tb3+ core-shell structured spherical particles

Nanocrystalline CaWO4 and Eu3+ (Tb3+)-doped CaWO4 phosphor layers were coated on non-aggregated, monodisperse and spherical SiO2 particles by the Pechini sol-gel method, resulting in the formation of SiO2@CaWO4, SiO2@CaWO4:Eu3+/Tb3+, core-shell structured particles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), time-resolved PL spectra and lifetimes were used to characterize the core-shell structured materials. Both XRD and FT-IR indicate that CaWO4 layers have been successfully coated on the SiO2 particles, which can be further verified by the FESEM and TEM images. The PL and CL demonstrate that the SiO2@CaWO4 sample exhibits blue emission band WO42- with a maximum at 420 nm (lifetime = 12.8 mu s) originated from the 4 groups, while SiO2@CaWO4:Eu3+ and SiO2@CaWO4:Tb3+ show additional red emission dominated by 614 nm (Eu3+:D-5(0)-F-7(2) transition, lifetime = 1.04 ms) and green emission at 544 nm (Tb3+:D-5(4)-F-7(5) transition, lifetime = 1.38 ms), respectively.

Sol-gel synthesis and photoluminescence properties of spherical SiO2@LaPO4 : Ce3+/Tb3+ particles with a core-shell structure

LaPO4: Ce3+ and LaPO4: Ce3+, Tb3+ phosphor layers have been deposited successfully on monodispersed and spherical SiO2 particles of different sizes ( 300, 500, 900 and 1200 nm) through a sol - gel process, resulting in the formation of core - shell structured SiO2@ LaPO4: Ce3+/ Tb3+ particles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microcopy (SEM), transmission electron microscopy (TEM), and general and time-resolved photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting SiO2@ LaPO4: Ce3+/ Tb3+ samples. The XRD results demonstrate that the LaPO4: Ce3+, Tb3+ layers begin to crystallize on the SiO2 templates after annealing at 700 degrees C, and the crystallinity increases on raising the annealing temperature. The obtained core - shell phosphors have perfectly spherical shape with a narrow size distribution, non-agglomeration, and a smooth surface. The doped rare-earth ions show their characteristic emission in the core - shell phosphors, i.e. Ce3+ 5d - 4f and Tb3+5D4 - F-7(J) (J = 6 - 3) transitions, respectively. The PL intensity of the Tb3+ increased on increasing the annealing temperature and the SiO2 core particle size.

Synthesis and characterization of ABC ternary segregated H-shaped copolymers

The synthesis of a novel ABC ternary segregated H-shaped copolymer is described, of which a central poly(ethylene glycol) (PEG) chain is terminated on both sides by polystyrene (PS) and poly(tert-butylacrylate) (PtBA) chains. The synthetic procedure involves functionalization of PEG by 2-bromosuccinic anhydride followed by esterification of 1,6-hexanediol, which gives its ends the bifunctional nature that allows sequential growth of two PS, then two PtBA arms via atom transfer radical polymerization (ATRP). The resulting segregated H-shaped copolymers were characterization by NMR spectroscopy and gel permeation chromatography (GPC). All these copolymers were affirmed to have well-defined structures and narrow molecular weight distributions.

Synthesis and properties of soluble polyimides based on isomeric ditrifluoromethyl substituted 1,4-bis(4-aminophenoxy)benzene

A new fluorinated diamine monomer, [1,4-bis(4-amino-3-trifluoromethylphenoxy)benzene (2)], and a known isomeric analog 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (3) were synthesized. A series of organosoluble polyimides Ia-d and IIa were prepared from the diamines (2, 3) and dianhydrides (a-d) by a high-temperature one-step method. The effects of the trifluoromethyl substituents on the properties of polyimides were evaluated through the study of their soluble, thermal, optical, and gas permeability properties. Polyimides (Ia-d) had glass transition temperatures between 229 and 279 degrees C, and the temperatures at 5% weight loss ranged from 510 to 533 degrees C under nitrogen. These polyimides could be cast into flexible and tough membranes from DMAc solutions. The membranes had tensile strengths in the range of 137-169 MPa, tensile modulus in the range of 1.6-2.2 GPa and elongations at break from 11% to 14%. The polyimide la with trifluoromethyl groups ortho to the imide nitrogen exhibited enhanced gas permeability, solubility, transparency, and thermal stability compared with the isomeric polyimide IIa with the CF3 group meta to the imide nitrogen.

Synthesis and characterization of the biodegradable polycaprolactone-graft-chitosan amphiphilic copolymers

A novel synthetic approach to biodegradable amphiphilic copolymers based on poly (epsilon-caprolactone) (PCL) and chitosan was presented, and the prepared copolymers were used to prepare nanoparticles successfully. The PCL-graft-chitosan copolymers were synthesized by coupling the hydroxyl end-groups on preformed PCL chains and the amino groups present on 6-O-triphenylmethyl chitosan and by removing the protective 6-O-triphenylmethyl groups in acidic aqueous solution. The PCL content in the copolymers can be controlled in the range of 10-90 wt %. The graft copolymers were thoroughly characterized by H-1 NAM, C-13 NMR, FT-IR and DSC. The nanoparticles made from the graft copolymers were investigated by H-1 NMR, DLS, AFM and SEM measurements. It was found that the copolymers could form spherical or elliptic nanoparticles it? water. The amount of available primary amines on the surface of the prepared nanoparticles was evaluated by ninhydrin assail, and it can be controlled by the grafting degree of PCL.

Silica supported submicron SiO2@Y2SiO5 : Eu3+ and SiO2@Y2SiO5 : Ce3+/Tb3+ spherical particles with a core-shell structure: Sol-gel synthesis and characterization

X-1-y(2)SiO(5):Eu3+ and X-1-Y2SiO5:Ce3+ and/or Tb3+ phosphor layers have been coated on nonaggregated, monodisperse, submicron spherical SiO2 particles by a sol-gel process, followed by surface reaction at high temperature (1000 degrees C), to give core/shell structured SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), TEM, photoluminescence (PL), low voltage cathodoluminescence (CL), and time-resolved PL spectra and lifetimes are used to characterize these materials. The XRD results indicate that X-1-Y2SiO5 layers have been successfully coated on the sur- face Of SiO2 particles, as further verified by the FESEM and TEM images. The PL and CL studies suggest that SiO2@Y2SiO5:Eu3+, SiO2@Y2SiO5:Tb3+ (or Ce3+/Tb3+), and SiO2@Y2SiO5:Ce3+ core/shell particles exhibit red (Eu3+, 613 rim: D-5(0)-F-7(2)), green (Tb3+, 542nm: D-5(4)-F-7(5)), or blue (Ce3+, 450nm: 5d-4f) luminescence, respectively. Pl, excitation, emission, and time-resolved spectra demonstrate that there is an energy transfer from Ce3+ to Tb3+ in the SiO2@Y2SiO5:Ce3+,Tb3+ core/shell particles.

Highly efficient iridium(III) complexes with diphenylquinoline ligands for organic light-emitting diodes: Synthesis and effect of fluorinated substitutes on electrochemistry, photophysics and electroluminescence

A series of novel cyclometalated iridium(III) complexes bearing 2,4-diphenylquinoline ligands with fluorinated substituent were prepared and characterized by elemental analysis, NMR and mass spectroscopy. The cyclic voltammetry, absorption, emission and electroluminescent properties of these complexes were systematically investigated. Electrochemical studies showed that the oxidation of the fluorinated complexes occurred at more positive potentials (in the range 0.57-0.69 V) than the unfluorinated complex 1 (0.42 V). In view of the energy level, the lowering of the LUMO by fluorination is significantly less than that of the HOMO. The weak and low energies absorption bands in the range of 300-600 nm are well resolved, likely associated with MLCT and (3)pi-pi* transitions. These complexes show strong orange red emission both in the solution and solid state. The emission maxima of the fluorinated complexes showed blue shift by 9, 24 and 15 nm for 2, 3 and 4, respectively, with respect to the unfluorinated analogous 1. Multilayered organic light-emitting diodes (OLEDs) were fabricated by using the complexes as dopant materials. Significantly higher performance and lower turn-on voltage were achieved using the fluorinated complexes as the emitter than that using the unfluorinated counterpart 1 under the same doping level.