One‐Pot Synthesis of Pomegranate‐Structured Fe3O4/Carbon Nanospheres‐Doped Graphene Aerogel for High‐Rate Lithium Ion Batteries

A unique hierarchically nanostructured composite of iron oxide/carbon (Fe₃O₄/C) nanospheres‐doped three‐dimensional (3D) graphene aerogel has been fabricated by a one‐pot hydrothermal strategy. In this novel nanostructured composite aerogel, uniform Fe₃O₄ nanocrystals (5–10 nm) are individually embedded in carbon nanospheres (ca. 50 nm) forming a pomegranate‐like structure. The carbon matrix suppresses the aggregation of Fe₃O₄ nanocrystals, avoids direct exposure of the encapsulated Fe₃O₄ to the electrolyte, and buffers the volume expansion. Meanwhile, the interconnected 3D graphene aerogel further serves to reinforce the structure of the Fe₃O₄/C nanospheres and enhances the electrical conductivity of the overall electrode. Therefore, the carbon matrix and the interconnected graphene network entrap the Fe₃O₄ nanocrystals such that their electrochemical function is retained even after fracture. This novel hierarchical aerogel structure delivers a long‐term stability of 634 mA h g^?1 over 1000 cycles at a high current density of 6 A g^?1 (7 C), and an excellent rate capability of 413 mA h g^?1 at 10 A g^?1 (11 C), thus exhibiting great potential as an anode composite structure for durable high‐rate lithium‐ion batteries.     

Highly Selective Transmembrane Transport of Exogenous Lithium Ions through Rationally Designed Supramolecular Channels

Lithium ions have been applied in the clinic in the treatment of psychiatric disorders. In this work, we report artificial supramolecular lithium channels composed of pore-containing small aromatic molecules. By adjusting the lumen size and coordination numbers, we found that one of the supramolecular channels developed shows unprecedented transmembrane transport of exogenous lithium ions with a Li⁺/Na⁺ selectivity ratio of 23.0, which is in the same level of that of natural Na⁺ channels. Furthermore, four coordination sites inside channels are found to be the basic requirement for ion transport function. Importantly, this artificial lithium channel displays very low transport of physiological Na⁺, K⁺, Mg²⁺, and Ca²⁺ ions. This highly selective Li⁺ channel may become an important tool for studying the physiological role of intracellular lithium ions, especially in the treatment of psychiatric disorders.     

Valence-variable Catalysts for Redox-controlled Switchable Ring-opening Polymerization

As a representative class of sustainable polymer materials, biodegradable polymers have attracted increasing interest in recent years. Despite significant advance of related polymerization techniques, realizing high sequence-control and easy-handling in ring-opening (co)polymerizations still remains a central challenge. To this end, a promising solution is the development of valence-variable metal-based catalysts for redox-induced switchable polymerization of cyclic esters, cyclic ethers, epoxides, and CO₂. Through a valence-determined electron effect, the switch between different catalytically active states as well as dormant state contributes to convenient formation of polymer products with desired microstructures and various practical performances. This redox-controlled switchable strategy for controlled synthesis of polymers is overviewed in this Review with a focus on potential applications and challenges for further studies.     

High‐order compact schemes for fractional differential equations with mixed derivatives

In this article, we consider two‐dimensional fractional subdiffusion equations with mixed derivatives. A high‐order compact scheme is proposed to solve the problem. We establish a sufficient condition and show that the scheme converges with fourth order in space and second order in time under this condition.© 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 2141–2158, 2017     

Simulation of nuclide migration in a middle- and low-level radioactive waste repository based on GMS

Journal of Radioanalytical and Nuclear Chemistry - Groundwater is the most important factor contributing to the diffusion and migration of radionuclides in the repository. In this paper, the...     

无催化剂下醇和酚的高效O-硅基化

硅醚类化合物广泛应用于有机合成、 分离分析和精细化工等领域. 六甲基二氮硅烷是近年来发展的一种新型硅基化试剂, 被用于硅醚的高效合成, 但由于六甲基硅烷较为惰性, 通常需要加入催化剂活化. 本文报道了一种无催化剂下醇、 酚的高效硅基化新方法. 研究结果表明, 该方法可以兼容一级苄醇、 杂芳基苄醇、 脂肪醇, 二级醇甚至三级醇, 多数反应可以实现定量转化, 无需柱层析即可实现产物的分离纯化. 该方法可以拓展到酚的高效硅醚化, 也可以很方便地放大到100 mmol, 收率达到99%, 表明该方法具有较好的实用价值.     

Impact of post-injection strategy on the physicochemical properties and reactivity of diesel in-cylinder soot

Post injection has significant benefit in the reduction of diesel soot emissions. Therefore, there is a need to understand the effect of post-injection strategy on soot physicochemical properties and reactivity because they play an important role in soot oxidation process that governs the final soot emissions. This work focuses on the impact of post injection on the physicochemical properties and reactivity of diesel in-cylinder soot using a main plus post injection (M*P) and a single injection (M) strategy. The soot was sampled by a developed total cylinder sampling system, and the dividing points of soot formation-dominant and oxidation-dominant phases were used for studying the impacts of post injection on the characteristics of in-cylinder soot. The physicochemical properties of the soot samples, including primary particle size, nanostructure, carbon chemical state and surface functional groups, were characterized. The soot reactivity was evaluated in terms of peak temperature, burnout temperature and apparent activation energy. In the oxidation-dominant phase, the M*P soot initially possesses smaller primary particle size, shorter fringe length, larger tortuosity, lower sp²/sp³ hybridization ratio of carbon atoms and higher content of aliphatic CH groups than the M soot. The beneficial influence of physicochemical properties on soot reactivity when using post injection is validated by the thermogravimetric data, which shows that the M*P soot is more reactive than the M soot at the onset of the oxidation-dominant phase. In the M*P case, the soot generated from the main-injection combustion has lower reactivity than the soot from the post-injection combustion after they experience the soot formation-dominant phase. The results indicate that the use of post injection leads to in-cylinder soot with physicochemical properties that favor reactivity. The enhancement of reactivity means that the soot will be more readily oxidized in the subsequent combustion process, and consequently contributes to a reduction in final soot emissions.     

Copper‐Catalyzed Reaction Cascade of Thiophenol Hydroxylation and S‐Arylation through Disulfide‐Directed C−H Activation

Copper‐catalyzed thiophenol C?H activation is described. Through an initial attempt to conduct C‐arylation with arylboronic acid, a rather surprising sequential C?H activation and S‐arylation was discovered. Mechanistic investigation revealed the disulfide intermediate as the key component in directing C?H oxidation. The overall reaction proceeded under mild conditions with molecular oxygen as the oxidant. Discovery of disulfide as the directing group provides a potential new direction for catalytic C?H functionalization under mild conditions.     

Responsive Gels with the Polymer Containing Alternating Naphthalene Diimide and Fluorinated Alkyl Chains: Gel Formation and Responsiveness as Well as Electrical Conductivity of Polymer Thin Films

A new electroactive polymer 1 with alternating NDI (naphthalene diimide) moieties and fluorinated alkyl chains was prepared and characterized. Gels of polymer 1 were formed in several solvents. Interestingly, gels of polymer 1 exhibited responsiveness toward N₂H₄, F^? and CN^?. Absorption and ESR spectroscopic studies revealed that such responsiveness is owing to the reduction of NDI moieties into the respective NDI^.?. In addition, thin films of polymer 1 were easily prepared with spin‐coating technique and the electrical conductivity of thin films reached 52.4 S/m after exposure to N₂H₄ vapor.