52 research outputs found

    Palladium-Catalyzed Intramolecular Aminoacetoxylation of Unactivated Alkenes with Hydrogen Peroxide as Oxidant

    No full text
    A palladium-catalyzed intramolecular aminoacetoxylation of unactivated alkenes was developed in which H<sub>2</sub>O<sub>2</sub> was used as the sole oxidant. A variety of 3-acetoxylated piperidines were obtained in good yields with good to excellent regio- and diastereoselectivities. Mechanistic study revealed that the addition of di­(2-pyridyl) ketone (dpk) ligand was crucial to promote the oxidative cleavage of the C–Pd­(II) bond by H<sub>2</sub>O<sub>2</sub> to give the C–OAc bond

    Pd-Catalyzed Intramolecular Aminohydroxylation of Alkenes with Hydrogen Peroxide as Oxidant and Water as Nucleophile

    No full text
    A palladium-catalyzed intramolecular aminohydroxylation of alkenes was developed, in which H<sub>2</sub>O<sub>2</sub> was applied as the sole oxidant. A variety of related alkyl alcohols could be successfully obtained with good yields and excellent diastereoselectivities, which directly derived from oxidation cleavage of alkyl C-Pd bond by H<sub>2</sub>O<sub>2</sub>. Facile transformation of these products provided a powerful tool toward the synthesis of 2-amino-1,3-diols and 3-ol amino acids. Preliminary mechanistic studies revealed that major nucleophilic attack of water (S<sub>N</sub>2 type) at high-valent Pd center contributes to the final C-O­(H) bond formation

    Improved Interfacial Affinity and CO<sub>2</sub> Separation Performance of Asymmetric Mixed Matrix Membranes by Incorporating Postmodified MIL-53(Al)

    No full text
    Asymmetric mixed matrix membranes­(MMMs) with MOFs hold great application potential for energy-efficient gas separations. However, the particle aggregation and nonselective interfacial microvoids restrict the gas separation performance of asymmetric MMMs. Herein, nanoporous metal–organic framework (MOF) of MIL-53­(Al) was modified with aminosilane after solvothermal synthesis. The postfunctionalization by grafting alkyl chains can form hydrogen bonds with polymer chains to enhance the affinity with polymer matrix and facilitate the preferential adsorption of CO<sub>2</sub> by dipole–quadrupole interaction with the functional group. Then the postmodified MIL-53­(Al) was incorporated as filler into poly­(ether imide) Ultem1000 to fabricate high-quality asymmetric MMMs with well dispersed particles in polymer matrix and good adhesion at the MOFs-polymer interface. The Ultem/S-MIL-53­(Al) asymmetric MMMs exhibited remarkable combinations of gas permeance and ideal selectivity for CO<sub>2</sub>/N<sub>2</sub> separation at 10 wt % filler loading. The CO<sub>2</sub> permeance achieved 24.1 GPU, an increase of 165% compared with pure Ultem membrane. Meanwhile, the ideal CO<sub>2</sub>/N<sub>2</sub> selectivity also increased from 31.0 up to 41.1. The strategy of post covalent modification for MOFs provides an effective way to improve the interfacial affinity and gas separation performance

    Facile Preparation and Characterization of Modified Polyurethane Sponge for Oil Absorption

    No full text
    Oil spills have devastating effects on the environment. Utilization of absorbents for oil spill cleanup has been practiced; however, the development of cheap, reliable, environmentally friendly absorbents is both desirable and urgent. In this study, we illustrate a novel oil absorbent fabricated by modifying polyurethane (PU) sponges with TiO<sub>2</sub> sol. The attachment of TiO<sub>2</sub> nanoparticles reduced the hydrophilicity of the modified PU sponge significantly by increasing its surface roughness and changing the chemical composition of the surface. The modified PU sponges exhibited oil absorption capacity of 95–110 g/g with negligible water uptake under both static and dynamic conditions. The modified PU sponge was found to be reusable up to 12 cycles holding 70% of its initial uptake capacity. The modified PU sponges can be effectively used in oil spill cleanup

    Facile Preparation and Characterization of Modified Polyurethane Sponge for Oil Absorption

    No full text
    Oil spills have devastating effects on the environment. Utilization of absorbents for oil spill cleanup has been practiced; however, the development of cheap, reliable, environmentally friendly absorbents is both desirable and urgent. In this study, we illustrate a novel oil absorbent fabricated by modifying polyurethane (PU) sponges with TiO<sub>2</sub> sol. The attachment of TiO<sub>2</sub> nanoparticles reduced the hydrophilicity of the modified PU sponge significantly by increasing its surface roughness and changing the chemical composition of the surface. The modified PU sponges exhibited oil absorption capacity of 95–110 g/g with negligible water uptake under both static and dynamic conditions. The modified PU sponge was found to be reusable up to 12 cycles holding 70% of its initial uptake capacity. The modified PU sponges can be effectively used in oil spill cleanup

    Facile Preparation and Characterization of Modified Polyurethane Sponge for Oil Absorption

    No full text
    Oil spills have devastating effects on the environment. Utilization of absorbents for oil spill cleanup has been practiced; however, the development of cheap, reliable, environmentally friendly absorbents is both desirable and urgent. In this study, we illustrate a novel oil absorbent fabricated by modifying polyurethane (PU) sponges with TiO<sub>2</sub> sol. The attachment of TiO<sub>2</sub> nanoparticles reduced the hydrophilicity of the modified PU sponge significantly by increasing its surface roughness and changing the chemical composition of the surface. The modified PU sponges exhibited oil absorption capacity of 95–110 g/g with negligible water uptake under both static and dynamic conditions. The modified PU sponge was found to be reusable up to 12 cycles holding 70% of its initial uptake capacity. The modified PU sponges can be effectively used in oil spill cleanup

    Multilayer Three-Dimensional Structure Made of Modified Stainless Steel Mesh for in Situ Continuous Separation of Spilled Oil

    No full text
    A multilayer three-dimensional (3D) structure made of hydrophobic stainless steel mesh has been designed for in situ continuous oil/water separation. The hydrophobic stainless steel mesh was prepared via a facile and environmental friendly method by etching with FeCl<sub>3</sub> solution and coating with <i>n</i>-octadecylthiol. The as-prepared mesh allows oils (gasoline, diesel oil, engine oil) and organic solvents (hexane, liquid paraffin) to pass through and repels water. A separation device equipped with the multilayer 3D structure can continuously separate the aforementioned oils from oil–water mixtures. The separation efficiency of continuous separation is more than 99.0 wt % and shows little decrease after 10 cycles

    Sacrificial Template Synthesis and Photothermal Conversion Enhancements of Hierarchical and Hollow CuInS<sub>2</sub> Microspheres

    No full text
    Hierarchical and hollow CuInS<sub>2</sub> microspheres are synthesized on the basis of sacrificial templates with solid and hollow CuS microspheres as sacrificial templates, respectively. Transformations from CuS solid microspheres to CuInS<sub>2</sub> hierarchical microspheres and CuS hollow microspheres to CuInS<sub>2</sub> hollow microspheres can be achieved by a solvothermal process at 180 °C for 24 h with <i>N</i>,<i>N</i>-dimethylformamide as both solvent and reductant. The products are well characterized, and the formation mechanisms are proposed. The as-synthesized products have strong optical absorption from 1000 to 2000 nm in addition to normal absorption from 400 to 800 nm, which has not be reported in the literature. The as-synthesized products exhibit a significant photothermal conversion effect under an irradiation of a 1064 nm laser. At a laser power of 0.05 W·cm<sup>–2</sup>, up to 30% and 20% enhancement of photothermal conversion is observed in the aqueous suspension containing 0.1 wt % CuInS<sub>2</sub> hollow microspheres and hierarchical microspheres, respectively. The mechanisms for the enhancements of photothermal conversion in the as-synthesized products are also discussed

    Alternative Immunomodulatory Strategies for Xenotransplantation: CD80/CD86-CTLA4 Pathway-Modified Immature Dendritic Cells Promote Xenograft Survival

    Get PDF
    <div><p>Background</p><p>Xenotransplantation is a promising approach to circumventing the current organ shortage. However, T-cell-dependent anti-xenoresponses are a major challenge to successful xenografts. Given the advantages of the use of CTLA4-Ig in the survival of allografts, the purpose of the study was to investigate the therapeutic potential of CTLA4-IgG4 modified immature dendritic cells (imDCs) in the prevention of islets xenograft rejection.</p><p>Methods</p><p>CTLA4-IgG4 was constructed by the fusion of the extracellular regions of porcine CTLA4 to human the hIgG4 Fc region. The imDCs were induced and cultured from porcine peripheral blood mononuclear cells (PBMC). The CTLA4-IgG4 modified imDCs were delivered via the portal vein to the liver of diabetic mice (insulin-dependent diabetes mellitus) before islet xenografting, and mCTLA4-Ig was administered intravenously after xenotransplantation.</p><p>Results</p><p>The xenograft survival of mice receiving unmodified imDCs was approximately 30 days. However, following administration of CTLA4-IgG4 modified imDCs before grafting and mCTLA4-Ig after grafting, xenografts survived for more than 100 days. Flow cytometric analysis showed that the CD4<sup>+</sup>CD25<sup>+</sup>Foxp3<sup>+</sup> Treg population was increased in spleens. The efficacy of donor CTLA4-IgG4 modified imDCs correlated partially with the amplification of Tregs.</p><p>Conclusions</p><p>These results confirm that selective inhibition of the direct and indirect pathways of T-cell activation by donor CTLA4-IgG4 modified imDCs and receptor CTLA4-Ig is a highly effective strategy to promote survival of xenografts.</p></div
    • …
    corecore