石墨炉原子吸收分光光度法测定血清中铜

铜系人体内含有的微量元素。测定血清中Cu/Zn比值,有助于病因分析和提供诊断依据。目前,测定血清铜所用的仪器分析方法甚多。本法无需对血清样进行预处理,取样量仅20—50μl。碱金属和碱土金属卤化物无干扰。特征质量m。为5.6pg/0.0044A.S,回收率98～102%,变异系数1.7-2.7%。     

Novel construction of the brassinolide side chain

A stereoselective synthesis of brassinolide, which involves construction of the side chain by a highly stereoselective aldol reaction between 20S-6β-methoxy-3α,5-cyclo-5α-pregnane-20-carboxaldehyde 2 and ketone 3 or 4 catalyzed by l-proline, is described.     

碳纳米管/ZnO纳米复合体的制备和表征

通过将不同直径的ZnO纳米颗粒与碳纳米管连接制备了碳纳米管/ZnO纳米复合体. 将团聚的ZnO纳米颗粒分散并用表面活性剂CTAB使纳米颗粒带正电. 化学氧化碳纳米管使其带负电. ZnO/CTAB微团通过碳管表面羧基与CTAB的静电作用与碳纳米管连接形成纳米复合体. 研究了复合体形成的不同实验条件, 表征了碳纳米管/ZnO纳米复合体的结构并研究了纳米复合体的光学特性. 研究表明, 与碳纳米管连接的ZnO纳米颗粒是互不连接的并保持量子点的特性. 光致发光研究表明ZnO纳米颗粒的激发在纳米复合体中有淬灭.     

Preparation of α-amino acids via Ni-catalyzed reductive vinylation and arylation of α-pivaloyloxy glycine

This work emphasizes easy access to α-vinyl and aryl amino acids via Ni-catalyzed cross-electrophile coupling of bench-stable N-carbonyl-protected α-pivaloyloxy glycine with vinyl/aryl halides and triflates. The protocol permits the synthesis of α-amino acids bearing hindered branched vinyl groups, which remains a challenge using the current methods. On the basis of experimental and DFT studies, simultaneous addition of glycine α-carbon (Gly) radicals to Ni(0) and Ar–Ni(ii) may occur, with the former being more favored where oxidative addition of a C(sp²) electrophile to the resultant Gly–Ni(i) intermediate gives a key Gly–Ni(iii)–Ar intermediate. The auxiliary chelation of the N-carbonyl oxygen to the Ni center appears to be crucial to stabilize the Gly–Ni(i) intermediate.

We have developed Ni-catalyzed reductive coupling of N-carbonyl protected α-pivaloyloxy glycine with Csp²-electrophiles that enabled facile preparation of α-amino acids, including those bearing hindered branched vinyl groups.     

Electronic density of levels in a disordered system

Three-, two-, and one-dimensional disordered systems with randomly distributed, purely repulsive scattering centers, known as Lorentz models, are studied in the low energy limit [1]. Using a functional integral representation and a version of the “replica trick”, we have found in the D-dimensional system the density of electronic levels of the form

$\text{n(E)=b}{}_0\text{Eγ}\text{exp}\text{(?b}{}_1\text{E}{}^{\mathrm{<mtext>?(</mtext><mtext>D</mtext><mtext>2</mtext><mtext>)</mtext>}}\text{+b}{}_2\text{E}{}^{\mathrm{<mtext>?(</mtext><mtext>D</mtext><mtext>2</mtext><mtext>)+1</mtext>}}\text{+·+b}{}_{\mathrm{D}}\text{E}{}^{\mathrm{<mtext>?(</mtext><mtext>1</mtext><mtext>2</mtext><mtext>)</mtext>}}\text{)(1+O(}\text{E}\text{))}$

and the constants b₀, b₁,…, b_D, and γ have been determined.     

Two-Dimensional Supramolecular from the Self-Assembly of Dissymmetrical Oxamidato-Bridged Heterometallic Trinuclear Building Blocks: Synthesis, Crystal Structure, and Magnetic Properties

Two heterometallic trinuclear complexes {[Cu(oxbp)]₂Co(H₂O)₂}1.5DMF0.5H₂O (complex 1) and {[Cu(oxbm)]₂Co(H₂O)₂}2DMF (complex 2) were obtained from the self-organization of two new dissymmetrical oxamidato-bridged copper(II) building blocks [Cu(oxbp)]^– and [Cu(oxbm)]^–[H₃oxbp=N-benzoato-N'-(3-aminopropyl)oxamido, H₃oxbm=N-benzoato-N'-(2-amino-2-methylethyl)oxamido, DMF=dimethylformamide]. The crystal structure of complex 1 has been determined. Complex 1 crystallize in triclinic system, space group P-1, a=8.0609(16) Å, b=10.661(2) Å, c=22.279(5) Å, =85.32(3), =86.64(3), =70.90(3), and Z=1. The crystal structure of complex 1 consists of neutral trinuclear complex units, and hydrogen bond involved DMF and water molecules. Through the hydrogen bonds, weak coordination and CuCu weak interactions, complex 1 features a 2-D supramolecular structure. Magnetic susceptibility measurements (5–100 K) indicate that the central Co(II) and terminal copper metal ions are antiferromagnetically coupled with J=–28.09 and J=–29.70 cm^–1 for complex 1 and 2, respectively.     

Preparation and Characterization of Microencapsulated Hexadecane Used for Thermal Energy Storage

Polyurea microcapsules about 2.5μm in diameter containing phase change material for thermal energy storage application were synthesized and characterized by interfacial polycondensation method with toluene-2,4-diisocyanate and ethylenediamine as monomers in an emulsion system. Hexadecane was used as a phase change material and OP, which is nonionic surfactant, and used as an emulsifier. The chemical structure and thermal behavior of the microcapsules were investigated by FTIR and thermal analysis respectively. The results show encapsulated hexadecane has a good potential as a solar energy storage material.     

Highly selective two-photon chemosensors for fluoride derived from organic boranes

[reaction: see text] Three organoboron compounds are shown to be two-photon fluorescent sensors for fluoride anion with high sensitivity and selectivity. The recognition mechanism is attributed to the unique steric structure of the bulky dimesitylboryl group and the Lewis acid-base interaction between trivalent boron atom and fluoride anion.     

锂离子蓄电池正极材料LiFePO4研究进展

锂离子电池正极材料正在向着高比能量、长寿命、低成本、环境友好的方向发展,而具有橄榄石结构的LiFePO_4正极材料以其结构稳定、成本低、无污染等优点成为21世纪最理想的绿色电源,但自身也存在缺点。综述了锂离子电池正极材料LiFePO_4的研究进展。系统地阐述了LiFePO_4的晶体结构特征及性能、多种合成方法以及掺杂多种导电材料和控制晶体生长制备纳米粉体对材料性能的影响。对该材料的应用前景进行了展望,并提出了下一步可能的研究趋势。