聚吡咯@二氧化锰/碳纳米管薄膜电极的制备及在高性能锌离子电池中的应用

中性/弱酸性水系锌锰电池因其能量密度高、价格低廉、环境友好等优势受到广泛关注。然而,现有的二氧化锰正极材料存在导电性能差,在充放电过程中易于溶解等问题。这严重影响了电池的倍率性能和循环稳定性,阻碍了中性锌锰电池的应用。为了解决上述问题,本文设计了以碳纳米管(CNT)网络薄膜为导电基底沉积聚吡咯(PPy)包覆二氧化锰(PPy@MnO₂/CNT)的多级结构电极。碳纳米管和聚吡咯组装形成高比表面积的三维交联导电网络,为活性材料提供了快速的电子、离子传输通道;聚吡咯包覆纳米级二氧化锰能够有效地抑制二氧化锰的溶解,进而提升电池的倍率特性和循环稳定性。以PPy@MnO₂/CNT作为正极材料组装的水系锌锰电池在1 A·g^-1的电流密度下,比容量达到210 mAh·g^-1,循环1000圈后,电池依然具有较高的容量保持率(85.7%)。本工作的导电聚合物包覆活性物质的策略可为发展高稳定柔性储能器件提供新思路。     

A Multifunctional Polymer as an Interfacial Layer for Efficient and Stable Perovskite Solar Cells

Metal-cation defects and halogen-anion defects in perovskite films are critical to the efficiency and stability of perovskite solar cells (PSCs). In this work, a random polymer, poly(methyl methacrylate-co-acrylamide) (PMMA-AM), was synthesized to serve as an interfacial passivation layer for synergistically passivating the under-coordinated Pb²⁺ and anchor the I^- of the [PbI₆]⁴⁻ octahedron. Additionally, the interfacial PMMA-AM passivation layer cannot be destroyed during the hole transport layer deposition because of its low solubility in chlorobenzene. This passivation leads to an enhancement in the open-circuit voltage from 1.12 to 1.22 V and improved stability in solar cell devices, with the device maintaining 95 % of the initial power conversion efficiency (PCE) over 1000 h of maximum power point tracking. Additionally, a large-area solar cell module was fabricated using this approach, achieving a PCE of 20.64 %.     

Ultrasound‐assisted aqueous two‐phase extraction of phenylethanoid glycosides from Cistanche deserticola Y. C. Ma stems

An efficient ultrasound‐assisted aqueous two‐phase extraction and enrichment process for phenylethanoid glycosides from Cistanche deserticola Y. C. Ma stems was developed in this work. An ethanol/ammonium sulfate system was chosen for the aqueous two‐phase system due to its fine partitioning and recycling behaviors. Single‐factor experiments and response surface methodology were used to optimize the process parameters of the ultrasound‐assisted aqueous two‐phase extraction. The optimal conditions were as follows: a salt concentration of 23.5%, an ethanol concentration of 20%, an extraction time of 37 min, an extraction temperature of 30°C, a liquid/solid ratio of 30:1 w/w, and an ultrasound power of 300 W. Under the above conditions, the extraction yields of echinacoside and acteoside (the main components of phenylethanoid glycosides) reached 5.35 and 6.22 mg/g dry material weight, respectively. The contents of echinacoside and acteoside in the extracts reached 27.56 and 30.23 mg/g, respectively, which were 2.46‐ and 2.58‐fold higher than the amounts obtained in ultrasound‐assisted extraction. In conclusion, ultrasound‐assisted aqueous two‐phase extraction was an efficient, ecofriendly, and economical method, and it may be a promising technique for extracting and enriching bioactive components from plants.     

Application of nano-scale zero-valent iron adsorbed on magnetite nanoparticles for removal of carbon tetrachloride: Products and degradation pathway

Nano-scale zero-valent iron (nZVI) attached to Fe₃O₄ nanoparticles (Fe⁰@Fe₃O₄), which has better dispersibility and a larger specific surface area than the nanoparticles alone, were prepared and applied to the reductive dechlorination of carbon tetrachloride (CT). CT removal efficiencies by Fe⁰@Fe₃O₄ composites with different ratios of the two components were compared. Under optimum conditions, when the Fe⁰/Fe₃O₄ ratio was 1:2, almost no CT was detected after 50 min and it took only about 30 min to reach a removal efficiency of 90%, compared with 120 min for an Fe⁰/Fe₃O₄ ratio of 1:4. An increase in the amount of nZVI in the catalyst effectively improved the removal of CT and accelerated the reaction rate. Chloroform was the main product. Compared with Fe₃O₄ alone, a significant increase in the solution concentrations of ferrous and ferric ions occurred in the Fe⁰@Fe₃O₄ system: both Fe²⁺ and Fe³⁺ reached their maximum concentrations at 60 min and then tended to decline over the next 60 min. The increase in Fe²⁺ concentration was attributed to the reaction between nZVI and CT, which produces ferrous ions when electrons transfer from Fe⁰ to organic chlorides. Synergistic effects between the composite constituents promoted the relative rates of mass transfer to reactive sites and Fe²⁺ generated in solution facilitated the reduction of chlorinated organic pollutants by magnetite. Thus, Fe⁰@Fe₃O₄ nanoparticles effectively achieved reductive dechlorination of CT and provide an improved nZVI catalyst for the remediation of chlorinated organic compounds.     

MOF-derived ZnO/ZnFe2O4@RGO nanocomposites with high lithium storage performance

ZnO/ZnFe₂O₄@reduced graphene oxide (RGO) nanocomposites have been successfully synthesized through annealing treatment of Zn/Fe MOF-5@GO composites. The ZnO/ZnFe₂O₄ nanoparticles with a diameter of 12–15 nm are evenly distributed on the surface of RGO. The ZnO/ZnFe₂O₄@RGO nanocomposites show superior rate capacity and cyclic stability of 655 mAh/g after 200 cycles at 0.2 A/g for lithium ion battery (LIB) anode. The superior electrochemical property benefits from the unique structure of ZnO/ZnFe₂O₄@RGO nanocomposites, which can provide a buffer space for volume expansion, and enhance conductivity in the charge/discharge cycle.

     

Modeling and analysis of the spread of computer virus

Based on a set of reasonable assumptions, we propose a novel dynamical model describing the spread of computer virus. Through qualitative analysis, we give a threshold and prove that (1) the infection-free equilibrium is globally asymptotically stable if the threshold is less than one, implying that the virus would eventually die out, and (2) the infection equilibrium is globally asymptotically stable if the threshold is greater than one. Two numerical examples are presented to demonstrate the analytical results.     

Fabrication of Nb2O5/Carbon Submicrostructures for Advanced Lithium-Ion Battery Anodes

Nb₂O₅ possesses superior fast Li⁺ storage capability for LIB anodes, benefiting from its fast pseudocapacitive behavior and low volumetric change within the cycling processes. However, the poor electric conductivity for Nb₂O₅ restricts its reaction kinetics and rate property. Herein, Nb₂O₅/carbon (C) submicrostructures are fabricated by solvothermal method followed by calcination process. The Nb₂O₅/C submicrostructures exhibit outstanding rate behavior and cyclic performance (332 (194) mAh g⁻¹ after 1000 cycles at 1 (5) A g⁻¹). The superior electrochemical property is attributed to the distinctive structure for Nb₂O₅/C submicrostructures, in which Nb₂O₅ nanoparticles uniformly distributed within Nb₂O₅/C composite can protect Nb₂O₅ nanoparticles from agglomeration, and the porous carbon matrix can enhance electron/ion conductivity. This work furnishes a novel strategy for fabricating Nb₂O₅/C submicrostructures with superior Li⁺ storage performance, which can be potentially used to design other metal oxide/C submicrostructures for second battery anode.     

1550 nm单模光纤中的量子密钥分配

从实验中实现了红外波段的远程量子密钥分配。系统采用双不等臂M-Z干涉仪相位编码方式，工作波长为1550nm。通过分析量子密钥分配系统传输距离与误码率之间相互关系，给出了理论上理想不等臂M-Z系统与实际系统的最低误码率与传输距离间的关系，以及系统实测传输距离与误码率的关系。实验结果显示，本密钥分配系统已非常接近理想实验系统的性能。     

The First Europium(III) β‐Diketonate Complex Functionalized Polyhedral Oligomeric Silsesquioxane

The first europium(III) β‐diketonate complex functionalized polyhedral oligomeric silsesquioxane (POSS) has been obtained by immobilization of such a complex at a silicon vertex of the POSS cage through the complexation of Eu³⁺ ions with thenoyltrifluoroacetone‐functionalized POSS. The new molecular hybrid material is liquid at room temperature, and shows bright‐red emission when irradiated with UV light due to energy transfer from the thenoyltrifluoroacetone ligand to the coordinated Eu³⁺ ions. Thermal analysis has revealed a significant improvement in the thermal stability of the material compared with tris(2‐thenoyltrifluoroacetonate)europium(III) dihydrate, [Eu(TTA)₃] ? 2 H₂O. In the context of recent advances in printable electronic technology, this novel luminescent organic liquid with the characteristic emission of Eu³⁺ may potentially be useful in the development of next‐generation organic devices such as flexible displays.