原子吸收光谱法测定桃叶中K,Mg,Sr,Fe,Cu,Mn和Zn等元素

本文采用桃叶作标准样品，讨论了湿法消化法与炭化－灰化法两种样品处理方法对测定结果的影响及方法操作效果比较，并进一步讨论了温度对炭化－灰化法的影响情况。由此建立起该法的适宜条件。在此条件下，用原子吸收光谱法测定桃叶及冷杉树枯枝、叶中多种元素。其精密度和准确度均能满足测定要求。     

SU(3) spin-orbit coupled fermions in an optical lattice

We propose a scheme to realize the SU(3)spin-orbit coupled three-component fermions in an one-dimensional optical lattice.The topological properties of the single-particle Hamiltonian are studied by calculating the Berry phase,winding number and edge state.We also investigate the effects of the interaction on the ground-state topology of the system,and characterize the interaction-induced topological phase transitions,using a state-of-the-art density-matrix renormalization-group numerical method.Finally,we show the typical features of the emerging quantum phases,and map out the many-body phase diagram between the interaction and the Zeeman field.Our results establish a way for exploring novel quantum physics induced by the SOC with SU(N)symmetry.     

Paired Oxidative and Reductive Catalysis: Breaking the Potential Barrier of Electrochemical C(sp3)−H Alkenylation**

Due to the intrinsic inertness of alkanes, strong oxidative conditions are typically required to enable their C(sp³)−H functionalization. Herein, a paired electrocatalysis strategy was developed by integrating oxidative catalysis with reductive catalysis in one cell without interference, in which earth-abundant iron and nickel are employed as the anodic and cathodic catalysts, respectively. This approach lowers the previously high oxidation potential required for alkane activation, enabling electrochemical alkane functionalization at the ultra-low oxidation potential of ≈0.25 V vs. Ag/AgCl under mild conditions. Structurally diverse alkenes, including challenging all-carbon tetrasubstituted olefins, can be accessed using readily available alkenyl electrophiles.     

The effect of one valence electron: contrasting (PNP)Ni(CO) with (PNP)Ni(NO) to understand the half-bent NiNO unit

Reaction of a (PNP)Ni radical with NO finishes in the time of mixing to form a 1:1 adduct with a NO stretching frequency of 1654 cm (-1). NMR data of this diamagnetic product indicate C 2 v symmetry, which is contradicted by the X-ray structure, which shows it to be nonplanar at Ni, with a geometry intermediate between planar and tetrahedral; the planar geometry is thus the transition state for fluxionality giving time-averaged C 2 v symmetry. The X-ray structure, together with DFT calculations, reveals that the "half-bent" NiNO unit and the intermediate coordination geometry result from a Ni --> NO charge transfer, which has a nonintegral value, resulting in a continuum between NO (+) (hence Ni (0)) and NO (-) (hence Ni (II)). This is related to the nonaxially symmetric character of the Ni --> NO back-donation caused by the (PNP) environment on Ni. Steric effects of ( t )Bu and even chelate constraints are ruled out as the cause of the unusual electronic and structural features.     

Dechlorination of carbon tetrachloride by Nanoscale Nickeled Zero‐Valent Iron @ Multi‐Walled Carbon Nanotubes: Impact of reaction conditions,kinetics and mechanism

The nanoscale nickeled zero‐valent iron @ multi‐walled carbon nanotubes (NF@MWCNTs) were synthesized, characterized and used to dispose carbon tetrachloride (CT) in aqueous solution. Scanning electron microscopy (SEM), X‐ray energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) gas sorptometry measurements were conducted to characterize the microstructure of the NF@MWCNTs. And batch experiments under different operation parameters were conducted to investigated the activity of NF@MWCNTs on degrading CT, including the content of NF@MWCNTs composites, temperature, catalyst dosage, initial pH and different anions. The experimental results showed that 4% nickel content of Ni/Fe bimetal and 2:1 doping ratio of Fe/MWCNTs were the wise choices in this study, which provided excellent degradation efficiency of CT when compared with nanoscale zero‐valent iron (nZVI) (97.44% and 55.28%, respectively). That was benefited from the fact that MWCNTs as an excellent support material could reduce the activation energy of 7.952 kJ/mol, and the nickel metal further reduced the reaction activation energy of 11.022 kJ/mol as presented in the conceptual model. Beyond that, NF@MWCNTs showed good reusability after five times consecutive reaction. Based on these, the reaction mechanism and degradation pathway also had been discussed.     

小慈姑自然居群异交率的定量估测

用自然居群取样和单位点同工酶遗传标记的方法对小慈姑（Ｓａｇｉｔａｒｉａｐｏｔａｍｏｇｅｔｉｆｏｌｉａ）湖南茶陵居群中两个亚居群的异交率作了研究．密度较低的亚居群Ⅰ与密度较高的亚居群Ⅱ的异交率估计值分别为ｔ—∧Ⅰ＝（８１．９±２４．１）％和ｔ—∧Ⅱ＝（５０±２４．５）％．作者认为，对雌雄同株的小慈姑而言，居群中一定水平的自交应归因于同株不同花序间雌雄花的交配，异交率的高低不取决于居群密度而主要取决于同期开花花序在２个或２个以上的植株的数量．     

Degradation of Carbon Tetrachloride by nanoscale Zero‐Valent Iron @ magnetic Fe3O4: Impact of reaction condition,Kinetics, Thermodynamics and Mechanism

Nano‐scale zero‐valent Iron (nZVI) attached on the Fe₃O₄ nanoparticles were prepared and creatively applied in the reductive dechlorination of Carbon Tetrachloride (CT). The characterization results of the synthesized composite indicated a main component of nZVI particles assembled on the surface of Fe₃O₄ with a layer of iron‐oxide film on the periphery, of which the dispersibility was better and the specific surface area was larger. The effects of different reaction conditions like temperature, initial pH values, Fe⁰@Fe₃O₄ dosage and initial CT concentrations on the removal of CT were evaluated. Under the optimum conditions, the Fe⁰@Fe₃O₄ composites showed a CT removal efficiency of 89.1% in 60 min, which was much greater than that of nZVI (61.7%) and Fe₃O₄ particles (14.3%). The removal process obeyed the pseudo‐first‐order kinetic model. Synergy effects of the constituents in the composite which can promote the relative rates of mass transfer to reactive sites were proposed to be existed and the magnetism of Fe₃O₄ could help to overcome the aggregation and surface passivation problem of nZVI. Thus, Fe⁰@Fe₃O₄ nanoparticles in our study can effectively complete the reductive dechlorination of CT and an improved nZVI catalyst is provided for the remediation of chlorinated organic compounds.     

聚环氧乙烷聚合物电解质基高电压固态锂金属电池的研究进展

采用液态碳酸酯电解质的锂离子电池在遭遇极端工况时, 极易发生泄露、燃烧、甚至爆炸等重大安全事故. 相对比, 聚环氧乙烷(PEO)固态聚合物电解质可以显著提升锂电池的安全性, 并且其优异的可塑性使其可以被制成特定形状进而满足特殊领域的差异化需求; 更为重要的是: PEO固态聚合物电解质与锂金属负极兼容性好. 然而, PEO固态聚合物电解质电化学氧化窗口低, 难以匹配高电压正极材料(≥4 V), 极大限制了其在高电压、高能量密度固态聚合物锂金属电池中的进一步应用. 近期经过国内外科研工作者在PEO固态聚合物电解质结构设计、PEO端羟基改性、含硼锂盐引入、功能型粘结剂设计开发以及正极界面层构筑等方面所做出的不懈努力, PEO固态聚合物电解质基高电压固态锂金属电池取得了系列化重大科研进展. 基于此, 本综述主要从以下八个方面: (1)高电压正极片表面修饰超薄聚合物层、(2)高电压正极颗粒包覆、(3)对碳黑颗粒进行包覆、(4)使用富含羧基的粘结剂、(5)不对称固态聚合物电解质结构设计、(6)正极界面原位形成耐高电压界面层、(7)醚氧官能团(-OCH₃)封端PEO, 提升其本征耐高电压性能、(8)含硼锂盐做添加剂, 详细综述了采用PEO固态聚合物电解质构建的高电压固态锂金属电池所取得的最新研究进展以及相应的高电压固态锂金属电池界面稳定作用机制. 最后还对未来PEO固态聚合物电解质在高电压固态锂金属电池方面所存在的巨大挑战和发展趋势进行了详细展望和总结阐述.     

金属-有机框架材料在光电催化水分解领域的研究进展

光催化分解水是将太阳能转化为化学能的有效手段之一. 相比于粉末光催化, 采用H型电解池的光 电催化方法具有材料选择范围大、 载流子迁移和分离效率高、 电极易于回收等优点. 近年来, 金属有机框架 材料(MOFs)在光电催化水分解领域得到越来越多的应用. 相比于传统无机催化剂, MOFs光电极具有比表面积大、 结构易于调控等独特优势. 本文按照MOFs的应用形式分为纯MOFs、 MOFs与其它催化剂的复合结构和MOFs衍生物3类, 总结了近年来MOFs在光电催化水分解领域的研究现状和进展, 介绍了光催化/电催化领域的部分典型研究成果, 最后讨论了MOFs在光电催化水分解领域研究的重点和热点, 并对其未来发展做出了展望.