石墨烯-富勒烯铵碘盐复合载体负载Pd催化剂的制备及电催化氧化乙醇性能

采用水合肼水热还原法制备了不同比例还原氧化石墨烯(RGO)与n型自掺杂富勒烯铵碘盐(PCBANI)的复合载体RGO-PCBANI, 并在电极上用这些载体负载Pd纳米粒子制备了Pd/RGO-PCBANI电催化剂. 利用扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线衍射(XRD)及X射线光电子能谱(XPS)对RGO-PCBANI和Pd/RGO-PCBANI的形貌及结构进行了表征. 利用循环伏安和计时电流等电化学方法研究了该催化剂电催化氧化乙醇的性能. 结果表明, 所制备的RGO-PCBANI(6∶1)载体的分散性较好, 用其负载的Pd纳米粒子平均粒径为5.2 nm, 且Pd/RGO-PCBANI(6∶1)催化剂的催化活性最好, 质量电流密度达到1288.8 mA/mg.     

Bifunctional benzoxazines: Synthesis and polymerization of resorcinol based single isomers

Aside from their outstanding properties such as thermal and chemical stability and excellent mechanical performance, benzoxazines suffer from high polymerization temperatures. Isomeric mixtures of bifunctional benzoxazines based on resorcinol proved already to be highly reactive monomers enabling polymerizations at lower temperatures. This contribution describes the polymerization behavior of single benzoxazine isomers and furthermore the influence of different substituents at the aniline moiety on the curing temperature. Single isomers of bifunctional benzoxazines are now accessible in a straightforward one‐pot synthesis starting from resorcinol and the appropriate N‐phenyl functionalized aniline component. The asymmetric benzoxazine monomers bearing no (R‐a: T_peak = 179 °C) or electron‐donating substituents in meta position to N (R‐3,5dma: T_peak = 183 °C) succeed in lowering the polymerization temperature. Additionally, the impact of several initiating systems was studied resulting in a decrease of the polymerization temperature for all studied resorcinol derived benzoxazine isomers (down to 144 °C). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1243–1251     

Ionic Polymer Microspheres Bearing a CoIII–Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO2 and Epoxides

We report a unique strategy to obtain the bifunctional heterogeneous catalyst TBB‐Bpy@Salen‐Co (TBB=1,2,4,5‐tetrakis(bromomethyl)benzene, Bpy=4,4’‐bipyridine, Salen‐Co=N,N’‐bis({4‐dimethylamino}salicylidene)ethylenediamino cobalt(III) acetate) by combining a cross‐linked ionic polymer with a Co^III–salen Schiff base. The catalyst showed extra high activity for CO₂ fixation under mild, solvent‐free reaction conditions with no requirement for a co‐catalyst. The synthesized catalyst possessed distinctive spherical structural features, abundant halogen Br^? anions with good leaving group ability, and accessible Lewis acidic Co metal centers. These unique features, together with the synergistic role of the Co and Br^? functional sites, allowed TBB‐Bpy@Salen‐Co to exhibit enhanced catalytic conversion of CO₂ into cyclic carbonates relative to the corresponding monofunctional analogues. This catalyst can be easily recovered and recycled five times without significant leaching of Co or loss of activity. Moreover, based on our experimental results and previous work, a synergistic cycloaddition reaction mechanism was proposed.     

Pomegranate‐Inspired Design of Highly Active and Durable Bifunctional Electrocatalysts for Rechargeable Metal–Air Batteries

Rational design of highly active and durable electrocatalysts for oxygen reactions is critical for rechargeable metal–air batteries. Herein, we report the design and development of composite electrocatalysts based on transition metal oxide nanocrystals embedded in a nitrogen‐doped, partially graphitized carbon framework. Benefiting from the unique pomegranate‐like architecture, the composite catalysts possess abundant active sites, strong synergetic coupling, enhanced electron transfer, and high efficiencies in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The Co₃O₄‐based composite electrocatalyst exhibited a high half‐wave potential of 0.842 V for ORR, and a low overpotential of only 450 mV at the current density of 10 mA cm^?2 for OER. A single‐cell zinc–air battery was also fabricated with superior durability, holding great promise in the practical implementation of rechargeable metal–air batteries.     

Optimization of Bifunctional Antisense Oligonucleotides for Regulation of Mutually Exclusive Alternative Splicing of PKM Gene

Oligonucleotide tools, as modulators of alternative splicing, have been extensively studied, giving a rise to new therapeutic approaches. In this article, we report detailed research on the optimization of bifunctional antisense oligonucleotides (BASOs), which are targeted towards interactions with hnRNP A1 protein. We performed a binding screening assay, Kd determination, and UV melting experiments to select sequences that can be used as a high potency binding platform for hnRNP A1. Newly designed BASOs were applied to regulate the mutually exclusive alternative splicing of the PKM gene. Our studies demonstrate that at least three repetitions of regulatory sequence are necessary to increase expression of the PKM1 isoform. On the other hand, PKM2 expression can be inhibited by a lower number of regulatory sequences. Importantly, a novel branched type of BASOs was developed, which significantly increased the efficiency of splicing modulation. Herein, we provide new insights into BASOs design and show, for the first time, the possibility to regulate mutually exclusive alternative splicing via BASOs.     

Bifunctional transition metal‐based molecular catalysts for asymmetric C?C and C?N bond formation

This paper describes the recent advances in the conceptually new bifunctional Ir and Ru catalysts for asymmetric catalytic reactions. These reactions include the enantioselective Michael addition of 1,3‐dicarbonyl compounds to cyclic enones and nitroalkenes, and the enantioselective direct amination of α‐cyanoacetates with diazoesters. The outcome of these reactions in terms of reactivity and selectivity was delicately influenced by the catalyst structures and the reaction conditions including the solvents used. Even with a 1 : 1 molar ratio of donors to acceptors, the reactions proceeded smoothly to give the corresponding chiral adducts with an excellent yield and enantiomeric excess (ee). Preliminary mechanistic studies showed that the key stage of the catalytic cycle is the interaction of the bifunctional catalyst with a pronucleophilic reagent that leads to stereoselective formation of C‐, O‐, or N‐bound complexes. The resulting protonated catalyst bearing metal‐bound nucleophiles readily reacts with electrophiles to provide C? C and C? N bond formation products in a highly stereoselective manner. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 106–123; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20172     

Intramolecular synergistic catalysis for asymmetric alternating copolymerization of CO2 and meso-epoxides

Asymmetric alternating copolymerization of meso-epoxides and carbon dioxide (CO₂) is an efficient route to produce isotactic polycarbonates with main-chain chirality involving two contiguous stereogenic centers. Based on multi-chiral induction and bimetallic synergistic catalysis, herein, we design novel binaphthol-linked dinuclear aluminum complexes bearing quaternary ammonium salts anchored on the ligand with multiple chiralities for asymmetric copolymerization of CO₂ and meso-epoxides, affording the completely alternating polycarbonates with up to 99% enantioselectivity. Also, they are discovered to be highly active and enantioselective in catalyzing alternating copolymerization of phthalic anhydride and meso-epoxides in a controlled manner. The linked-chain length and steric hindrance at the para-position on the phenolate moieties of the ligand have significant effects on both activity and enantioselectivity. Notably, the bifunctional, multichiral complexes prove to be highly enantioselective and selective even at a low catalyst loading of 20 ppm, indicating an intramolecular synergistic effect between the tethered quaternary ammonium salts and the metallic ions.     

In-Situ Electrodeposition of Rhodium nanoparticles Anchored on Reduced Graphene Oxide nanosheets as an Efficient Oxygen Reduction Electrocatalyst

A simple, versatile, and cost-effective one-pot electrochemical deposition is used to fabricate rhodium (Rh) nanoparticles decorated surface of reduced graphene oxide (rGO) functionalized glassy carbon electrode (GCE) for oxygen reduction reaction (ORR) in alkaline media. The chemical and physical structure of the sample is probed via transmission electron microscopy, rotating disk electrode (RDE), X-ray photoelectron spectroscopy, linear sweep voltammetry, and Raman spectroscopy. The synergistic effects between the unique properties of Rh nanoparticles and rGO creates such innovative hybrid that exhibits a catalytic activity comparable to that of the commercial platinum electrocatalyst (Pt/C). As a result, the as-electrodeposited Rh@rGO hybrid exhibits outstanding ORR activity in alkaline media, as evidenced by a larger diffusion-limited current, greater positive onset potential, much better stability and methanol tolerance than Pt/C under the same conditions.     

Sodalite‐type Cu‐based Three‐dimensional Metal–Organic Framework for Efficient Oxygen Reduction Reaction

Inspired by copper‐based oxygen reduction biocatalysts, we have studied the electrocatalytic behavior of a Cu‐based MOF (Cu‐BTT) for oxygen reduction reaction (ORR) in alkaline medium. This catalyst reduces the oxygen at the onset (E_onset) and half‐wave potential (E^1/2) of 0. 940 V and 0.778 V, respectively. The high halfway potential supports the good activity of Cu‐BTT MOF. The high ORR catalytic activity can be interpreted by the presence of nitrogen‐rich ligand (tetrazole) and the generation of nascent copper(I) during the reaction. In addition to the excellent activity, Cu‐BTT MOF showed exceptional stability too, which was confirmed through chronoamperometry study, where current was unchanged up to 12 h. Further, the 4‐electrons transfer of ORR kinetics was confirmed by hydrodynamic voltammetry. The oxygen active center namely copper(I) generation during ORR has been understood by the reduction peak in cyclic voltammetry as well in the XPS analysis.