Co3O4 nanosheets: synthesis and catalytic application for CO oxidation at room temperature

Hexagonal β-Co(OH)2 nanosheets with edge length of 50 nm and thickness of 10 nm were hydrothermally synthesized with the aid of triethylamine.Upon calcination at 350°C in air,the β-Co(OH)2 nanosheets was converted into Co3O4 nanosheets with a similar dimension.Structural analyses during the calcination process identified that the β-Co(OH)2 precursor was initially dehydrated to HCoO2 and subsequently transferred into Co3O4.When being applied to catalyze CO oxidation at room temperature,the Co3O4 nanosheets exhibited a higher activity than the conventional spherical nanoparticles.This was perhaps related to the partial exposure of the{112}planes over the Co3O4 nanosheets.The porous structure generated during the calcination process also provided significant amounts of surface defects,which might contribute to the enhanced catalytic activity as well.     

In-situ structural evolution analysis of Zr-doped Na3V2(PO4)2F3 coated by N-doped carbon layer as high-performance cathode for sodium-ion batteries

With great superiorities in energy density,rate capability and structural stability,Na₃V₂(PO₄)₂ F₃(NVPF)has attracted much attentions as cathode of sodium ion battery(SIB),but it also faces challenges on its poor intrinsic electronic conductivity and the controversial de/sodiation mechanism.Herein,a series of Zr-doped NVPF coated by N-doped carbon layer(~5 nm in thickness,homogenously)materials are fabricated by a sol-gel method,and the optimized heteroatom-doping amounts of Zr and N doping improve intrinsic properties on enlarging lattice distance and enhancing electronic conductivity,respectively.Specifically,among all samples of Na₃ V_2-xZr_x(PO₄)₂ F₃/NC(NVPF-Zr-x/NC,x=0,0.01,0.02,0.05,and 0.1),the optimized electrode of NVPF-Zr-0.02/NC delivers high reversible capacities(119.2 mAh g^-1 at0.5 C),superior rate capability(98.1 mA h g^-1 at 20 C)and excellent cycling performance.The structural evolution of NVPF-Zr-0.02/NC electrode,in-situ monitored by X-ray diffractometer,follows a step-wise Na-extraction/intercalation mechanism with reversible multi-phase changes,not just a solid-solutionreaction one.Full cells of NVPF-Zr-0.02/NC//hard carbon demonstrate high capacity(99.8 mA h g^-1 at 0.5 C),high out-put voltage(3.5 V)and good cycling stability.This work is favorable to accelerate the development of high-performance cathode materials and explore possible redox reaction mechanisms of SIBs.     

新型针孔点背光发光模型与实验研究

纳秒级强激光(～1014 W/cm2)与固体靶相互作用可以获得高亮度的Multi-keV能段X射线.在当前的高能量密度物理研究中利用这样的X射线背光源照相方式可以获得高质量的物理图像,具有重要的应用价值.以模拟计算与神光Ⅱ激光装置实验结果相结合的方式研究了激光等离子体发光模型.在该模型的基础上改进了针孔点背光成像技术,独立发展了针对低Z靶材料K线的准单能背向针孔点背光和针对中Z靶材料L带的高亮度侧向针孔点背光.在神光Ⅱ激光装置上通过新型针孔点背光对惯性约束聚变靶丸样品成像获得了高质量的静态靶丸流线图像,空间分辨优于10μm.实验结果表明新型的针孔点背光具备高亮度,高空间分辨,高图像衬度等优点可以广泛应用于高能量密度物理和惯性约束聚变的研究中.     

Symmetric Identities for Euler Polynomials

In this paper we establish two symmetric identities on sums of products of Euler polynomials.     

Increased optical damage resistance of Zr:LiNbO3 crystals

Zr: LiNbO₃ crystals has been grown. The crystal composition and phase are analyzed by X‐ray diffration. The optical damage resistance ability of Zr: LiNbO₃ crystals is studied by the Sénarmont compensation method and the transmitted beam pattern distortion method. The saturated value of the birefringence change of 6 mol% Zr: LiNbO₃ crystal is 1.01×10^‐4, which is seven times smaller than that of congruent pure LiNbO₃ crystal. The results of UV‐Visible and IR absorption spectra of Zr: LiNbO₃ crystals powerfully confirm that the optical damage resistance threshold concentration of the Zr⁴⁺ ions doped in LiNbO₃ crystals is about 6 mol% in the melt. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Iron(III) tetrakis(pentafluorophenyl)porpholactone catalyzes nitrogen atom transfer to C=C and C-H bonds with organic azides

We have demonstrated that iron porpholactones could be effective catalysts for nitrogen atom transfer reactions such as aziridination of alkenes and amidation of alkanes using organic azides.     

介质表面附近微波大气击穿的理论研究

将麦克斯韦方程组和简化等离子体方程耦合求解, 对介质表面附近大气击穿形成等离子体的过程进行了理论研究. 分别使用一维、二维模型对等离子体的形成过程及等离子体对电磁波的反射、吸收过程进行了模拟研究. 一维计算结果发现在n_e = 0, j = 0两种边界条件下, 虽然形成的等离子体密度分布相差较大, 但二者得到的微波反射、吸收、透射波形彼此相差不大. 初始电子数密度厚度为20 mm的条件下, 得到界面附近的等离子体密度大于5 mm厚度的情况. 二维计算结果发现, 由于TE10模在波导中心位置处的微波电场最强, 电子碰撞电离首先在中心位置处形成等离子体, 当等离子体密度达到一定值(临界密度附近)时, 波导中心介质表面处微波场强减小, 等离子体区域沿着介质表面向两侧移动. TE10模在波导边缘处微波电场强度小于击穿阈值, 因此等离子体区域不可能移动到波导边缘附近.     

Spectroscopic properties of Er<Superscript>3+</Superscript> in Sc:LiNbO<Subscript>3</Subscript> crystal

The results of Er³⁺ ion spectroscopic analysis in Sc:LiNbO₃ crystals were reported. The line strengths from the ground state to the excited state were evaluated from the measured unpolarized absorption spectrum and analyzed by using standard Judd–Ofelt theory. For Sc(3 mol. %):Er (1 mol. %):LiNbO₃ crystal, the obtained intensity parameters are: Ω₂=3.72×10^-20 cm², Ω₄=1.07×10^-20 cm², and Ω₆=0.98×10^-20 cm². The fluorescence spectra and microsecond time-resolved spectra were investigated in the visible region. The excited state absorption transition strengths at 800 nm excitation were evaluated based on Judd–Ofelt theory. The results obtained here were compared to results from other research on Er:LiNbO₃ crystals. PACS 71.20.Eh; 77.84.Dy; 42.70.Hj; 42.62.Fi; 42.65.Ky     

Cu(Ⅱ)-catalyzed aerobic oxidative amidation of azoarenes with amides

A method for Cu(Ⅱ)-catalyzed dehydrogenative amidation of azoarene using air as the terminal oxidant was developed. Various amides, such as arylamides, alkylamides, lactams, and imides, are all effective amidation reagents and provide the desired products in moderate to excellent yields. Notably, good yields can also be obtained on a gram-scale with this amidation reaction.In this protocol of azoarene amidation, the catalyst(Cu(OAc)_2) and oxidant(air) are inexpensive and readily available, and the process is highly efficient and atom economical.     

鸡血藤中7种金属元素的形态分析

对鸡血藤中铁、锰、铜、锌、钙、镁和锶7种金属元素的化学形态进行分析;分别用0.45μm微孔滤膜、LSA-10大孔吸附树脂、正辛醇-水萃取体系,将鸡血藤中各元素分离为可溶态与悬浮态、有机态与无机态、醇溶态与水溶态,用电感耦合等离子体-原子发射光谱法(ICP-AES)测定7种元素的各形态含量。结果表明:鸡血藤中7种元素在原药中的含量高低依次为:钙、镁、铁、锰、锶、铜和锌,水煎液中锌和镁的提取率大于50%,其次是铜为45.2%;铜的颗粒吸附率最高为26.3%;镁的KOW参数在肠、胃液酸度下均大于1,铁和锰的KOW参数均小于1,元素的KOW值受pH影响。