Bimetallic amine-bridged bis(phenolate) lanthanide aryloxides and alkoxides: synthesis,characterization, and application in the ring-opening polymerization of rac-lactide and rac-β-butyrolactone

A series of neutral bimetallic lanthanide aryloxides p-C6H4[OLnL(THF)n]2 [Ln = Y(1), Yb(2), Sm(3)(n = 1) and La(4)(n = 2), L = Me2NCH2CH2N{CH2-(2-O–C6H2–tBu2-3,5)}2] and alkoxides p-C6H4CH2[OLnL(THF)]2 [Ln = Y(5), Yb(6)] supported by an amine-bridged bis(phenolate) ligand have been synthesized through one-pot reactions of Ln(C5H5)3(THF), LH2 with p-benzenediol and 1,4-benzenedimethanol, respectively. All complexes have been fully characterized by elemental analyses, single-crystal X-ray diffraction analysis, and IR and multi-nuclear NMR spectroscopy(in the cases of 1, 4 and 5). Study of their catalytic behavior revealed that, in general, all complexes are efficient initiators for the polymerization of rac-lactide(LA) and rac-β-butyrolactone(BBL), except for 3 and 4 in the case of BBL. The influence imposed by lanthanides of different ionic radii and initiating groups of different structures on the activity, controllability, and stereoselectivity of polymerization were systematically studied and compared. Highly heterotactic PLA(Pr up to 0.99) and syndiotactic PHB(Pr ≈ 0.81) with high molecular weight and narrow polydispersity formed and were automatically capped with hydroxyl functionality at both ends.     

Electrochemical Properties of Hollow‐Structured MnS–Carbon Nanocomposite Powders Prepared by a One‐Pot Spray Pyrolysis Process

Spherical, hollow MnS? C composite powders were prepared from a solution of manganese salt, thiourea, and sucrose by one‐pot spray pyrolysis. The MnS? C composite powders were generated by direct sulfidation of MnO with hydrogen sulfide gas generated in situ by decomposition of thiourea during spray pyrolysis. Sucrose, which is used as a carbon source material, plays a key role in the formation of the MnS? C composite powders by improving the reducing atmosphere around the powders. Dot‐mapping images of the composite powders demonstrated uniform distribution of the manganese, sulfur, and carbon components within the MnS? C composite powder. Fine crystals of MnS were uniformly mixed with carbon derived from polymerization and carbonization of sucrose. The carbon content of the MnS? C composite powders was 26 wt %. The discharge capacities of the MnS? C composite powders in the 2nd and 200th cycles were 863 and 967 mA h g^?1, respectively, at a current density of 1000 mA g^?1. The spherical and hollow morphology of the MnS? C composite powders was completely retained, even after 200 cycles. The enhanced cycling and rate performance of the MnS? C composite powders is ascribed to the structural stability of the composite powders.     

Preparation of Yolk‐Shell and Filled Co9S8 Microspheres and Comparison of their Electrochemical Properties

In this study, we report the first preparation of phase‐pure Co₉S₈ yolk–shell microspheres in a facile two‐step process and their improved electrochemical properties. Yolk–shell Co₃O₄ precursor microspheres are initially obtained by spray pyrolysis and are subsequently transformed into Co₉S₈ yolk–shell microspheres by simple sulfidation in the presence of thiourea as a sulfur source at 350 °C under a reducing atmosphere. For comparison, filled Co₉S₈ microspheres were also prepared using the same procedure but in the absence of sucrose during the spray pyrolysis. The prepared yolk–shell Co₉S₈ microspheres exhibited a Brunauer–Emmett–Teller (BET) specific surface area of 18 m² g^?1 with a mean pore size of 16 nm. The yolk–shell Co₉S₈ microspheres have initial discharge and charge capacities of 1008 and 767 mA h g^?1 at a current density of 1000 mA g^?1, respectively, while the filled Co₉S₈ microspheres have initial discharge and charge capacities of 838 and 638 mA h g^?1, respectively. After 100 cycles, the discharge capacities of the yolk–shell and filled microspheres are 634 and 434 mA h g^?1, respectively, and the corresponding capacity retentions after the first cycle are 82 % and 66 %.     

Direct Photocatalysis for Organic Synthesis by Using Plasmonic‐Metal Nanoparticles Irradiated with Visible Light

Recent advances in direct‐use plasmonic‐metal nanoparticles (NPs) as photocatalysts to drive organic synthesis reactions under visible‐light irradiation have attracted great interest. Plasmonic‐metal NPs are characterized by their strong interaction with visible light through excitation of the localized surface plasmon resonance (LSPR). Herein, we review recent developments in direct photocatalysis using plasmonic‐metal NPs and their applications. We focus on the role played by the LSPR of the metal NPs in catalyzing organic transformations and, more broadly, the role that light irradiation plays in catalyzing the reactions. Through this, the reaction mechanisms that these light‐excited energetic electrons promote will be highlighted. This review will be of particular interest to researchers who are designing and fabricating new plasmonic‐metal NP photocatalysts by identifying important reaction mechanisms that occur through light irradiation.     

Flame Spray Pyrolysis for Finding Multicomponent Nanomaterials with Superior Electrochemical Properties in the CoOx‐FeOx System for Use in Lithium‐Ion Batteries

High‐temperature flame spray pyrolysis is employed for finding highly efficient nanomaterials for use in lithium‐ion batteries. CoO_x‐FeO_x nanopowders with various compositions are prepared by one‐pot high‐temperature flame spray pyrolysis. The Co and Fe components are uniformly distributed over the CoO_x‐FeO_x composite powders, irrespective of the Co/Fe mole ratio. The Co‐rich CoO_x‐FeO_x composite powders with Co/Fe mole ratios of 3:1 and 2:1 have mixed crystal structures with CoFe₂O₄ and Co₃O₄ phases. However, Co‐substituted magnetite composite powders prepared from spray solutions with Co and Fe components in mole ratios of 1:3, 1:2, and 1:1 have a single phase. Multicomponent CoO_x‐FeO_x powders with a Co/Fe mole ratio of 2:1 and a mixed crystal structure with Co₃O₄ and CoFe₂O₄ phases show high initial capacities and good cycling performance. The stable reversible discharge capacities of the composite powders with a Co/Fe mole ratio of 2:1 decrease from 1165 to 820 mA h g^?1 as the current density is increased from 500 to 5000 mA g^?1; however, the discharge capacity again increases to 1310 mA h g^?1 as the current density is restored to 500 mA g^?1.     

Synthesis of High Molecular Weight Cyclic Poly(ε‐caprolactone)s of Variable Ring Size Based on a Light‐Induced Ring‐Closure Approach

High molecular weight cyclic poly(ε‐caprolactone)s (cPCLs) with variable ring size are synthesized via light‐induced ring closure of α,ω‐anthracene‐terminated PCL (An‐PCL‐An). The ring size of cPCL is tunable simply by adjusting the polymer concentration from 10 to 100 mg mL⁻¹ in THF. The cyclo­addition via the bimolecular cyclization of An‐PC‐An is well characterized by a variety of analyses such as ¹H NMR and UV–vis spectroscopies, gel‐permeation chromatography, and differential scanning calorimetry. The reversible dimerization of An induced by heating enables the cyclic PCL to have a switchable “on–off” capability. This novel light‐induced ring‐closure technique can be one of the most powerful candidates for producing various well‐defined cyclic polymers in highly concentrated polymer solution.

     

硅表面活性剂增强的双网络耐高温多孔有机硅弹性体

采用聚醚改性三硅氧烷表面活性剂、 丙烯酸酯改性硅油和水3种组分制备了稳定的油包水(W/O)乳液, 经酸碱催化水解、 紫外引发聚合和干燥除水过程得到了双网络多孔有机硅弹性体. 扫描电子显微镜(SEM)分析结果表明, 所制备的有机硅弹性体具有丰富的孔径结构分布. 压缩强度测试结果表明, 弹性体具备良好的耐压缩性能, 45%压缩应变下循环50次, 仍具备良好的回弹性能. 有机硅弹性体具有优异的耐高温性能, 分解温度为370 ℃, 高于绝大多数多孔有机硅弹性体材料的分解温度. 丙烯酸酯改性硅油的制备工艺成熟、 廉价易得, 显著降低了多孔有机硅弹性体的生产成本, 为规模性开发有机硅材料提供了新的思路和应用前景.     

Investigation on the Interaction of Dy(Ш)/Rutin Complexes with Bovine Serum Albumin by Spectroscopic Methods

Journal of Solution Chemistry - The interaction between Dy(Ш)/Rutin complexes and bovine serum albumin (BSA) was studied by fluorescence, ultraviolet (UV) absorption, three-dimensional...     

Process prediction of Ni–SiC coatings based on RBF-BP model

The preparation of Ni–SiC coatings using magnetic field-assisted jet electrodeposition under various plating settings is described in this study. A RBF-BP composite neural network with 4 × 4 × 4 × 7 × 10 × 1 was used to predict the corrosion resistance of Ni–SiC coatings prepared by employing different plating parameters. The results show that the fitting degree between the expected value and the actual value of the RBF-BP composite neural network is 0.97497. Moreover, the hybrid neural network can accurately predict the corrosion resistance of Ni–SiC coatings prepared under different process parameters. The corrosion weight loss of the coating is the lowest at the current density of 4 A/dm², a jet rate of 3 m/s, a SiC particle concentration of 8 g/L, and at a magnetic field intensity of 0.8 T, demonstrating its corrosion resistance under these conditions. According to the coating characterization analysis, the coating's grain size was significantly refined, and the surface was smoother with a high amount of uniformly sized SiC nanoparticles.