糖化学中锡介入的选择性反应

本文从糖锡络合物结构出发,揭示了锡介入方法进行选择性反应的原因.并对该方法在糖化学各类不同类型的反应如酰化,烃化,氧化,磺化所表现的选择性进行了详细的论述.     

Na(Y1.5Na0.5)F6:Yb3+/Er3+纳米棒的制备及其上转换发光特性

采用水热合成法,使用油酸作为乳化剂制备了Yb3+/Er3+共掺杂六角相Na(Y1.5Na0.5)F6纳米棒。通过X射线衍射(XRD)、扫描电子显微镜(SEM)以及荧光光谱等测试手段对所制备的样品进行表征。测试结果表明,Na(Y1.5Na0.5)F6纳米晶的晶格常数为a=b=0.600 nm,c=0.352 nm。在980 nm红外光激发下,Yb3+/Er3+共掺杂Na(Y1.5Na0.5)F6纳米棒发出从红光到近紫外的上转换荧光,其中红光、绿光和近紫外光分别对应于Er3+离子4F9/2→4I15/2,(2H11/2,4S3/2)→4I15/2和(2G11/2/2H9/2)→4I15/2的能级跃迁。详细讨论和分析了各荧光波段的上转换发射过程。     

Syntheses, structures and properties of silver(I) complexes with flexible 1,3,5-tris(pyridylmethoxyl)benzene ligands

Five new silver(I) complexes [Ag₂(L₂)₂](BF₄)₂·CH₃CN·CH₃OH (1), [Ag(L₂)(CF₃SO₃)] (2), [Ag(L₃)]ClO₄·CH₃OH (3), [Ag₂(L₃)₂](CF₃SO₃)₂·CH₃CN·CH₃OH·H₂O (4) and [Ag(L₃)]PF₆·2CH₃CN (5) [L₂=1,3,5-tris(2-pyridylmethoxyl)benzene, L₃=1,3,5-tris(3-pyridylmethoxyl)benzene] were synthesized and characterized by single crystal X-ray diffraction analyses. In complexes 1-5, ligands L₂ and L₃ show different conformations and act as three-connectors, while the Ag(I) atom serves as three-connecting node to result in the formation of 2D and 3D frameworks. Complexes 1 and 2 with different counteranions have similar 2D network structure with the same (4,8²) topology. Complex 3 has a 3D structure with (10,3)-a topology while complexes 4 and 5 have the same 2D (6,3) topological structure. The results showed that the structure of organic ligands and counteranions play subtle but important role in determining the structure of the complexes. In addition, the photoluminescence and anion-exchange properties of the complexes were investigated in the solid state at room temperature.     

An edge-grafting theorem on Laplacian spectra of graphs and its application

Let 𝒰(n,?d) be the class of unicyclic graphs on n vertices with diameter d. This article presents an edge-grafting theorem on Laplacian spectra of graphs. By applying this theorem, we determine the unique graph with the maximum Laplacian spectral radius in 𝒰(n,?d). This extremal graph is different from that for the corresponding problem on the adjacency spectral radius as done by Liu et al. [Q. Liu, M. Lu, and F. Tian, On the spectral radius of unicyclic graphs with fixed diameter, Linear Algebra Appl. 420 (2007), 449–457].     

Hydrothermal synthesis and the enhanced blue upconversion luminescence of NaYF4:Nd3+,Tm3+,Yb3+

Nd³⁺, Tm³⁺ and Yb³⁺ co-doped NaYF₄ upconversion (UC) material was synthesized by the hydrothermal method. The structure of the sample was characterized by the X-ray diffraction, and its UC luminescence properties were investigated in detail. Under the 980 nm semiconductor laser excitation, its UC spectra exhibited distinct emission peaks at 451 nm, 475 nm and 646 nm respectively. On the basis of the comparison of UC spectra between NaYF₄:Nd³⁺,Tm³⁺,Yb³⁺ and NaYF₄:Tm³⁺,Yb³⁺, it was indicated that the existence of Nd³⁺ ion enhanced the blue emission intensity. The law of luminescence intensity versus pump power proved that the blue emission at 475 nm, and the red emission at 646 nm were the two-photon processes, while the blue emission at 451 nm was a three-photon process.     

决策矩阵排序的投影法及其相关定理

针对属性权重已知而属性值为确数的多属性决策问题,提出了决策矩阵排序的投影法,并提出了关于投影法的三个定理及其证明.最后给出了两个相关例子说明本法的有效性和可行性.     

带有广义导子的素环

The concept of derivations and generalized inner derivations has been generalized as an additive function δ: R→ R satisfying δ(xy) = δ(x)y xd(y) for all x,y∈R,where d is a derivation on R.Such a function δis called a generalized derivation.Suppose that U is a Lie ideal of R such that u2 ∈ U for all u ∈U.In this paper,we prove that U(C)Z(R) when one of the following holds:(1)δ([u,v]) = uov (2)δ([u,v]) uov=O(3)δ(uov) =[u,v](4)δ(uov) [u,v]= O for all u,v ∈U.     

A solvothermal route to size- and shape-controlled CdSe and CdTe nanocrystals

The size- and shape-controlled CdSe and CdTe nanocrystals, which exhibit obvious quantum confinement effect, have been synthesized by a solvothermal route. It is found that initial precursor concentrations are key factors in controlling the shape of the resulting nanocrystals. Moreover, the obtained nanocrystals are all of zinc blende structure, regardless of their sizes and shapes. A possible mechanism for the formation and growth of the nanocrystals is put forward. It is inferred that the adhesion and subsequent recrystallization of nanocrystals with an assistance of remaining monomers should be a major reason for formation and growth of the elongated nanocrystals.     

Self-Assembly Behaviors of Heterogemini Surfactant in Aqueous Solution Investigated by Dissipative Particle Dynamics

As a preliminary study, self-assembly behaviors of heterogemini surfactant in aqueous solution are explored tentatively by means of dissipative particle dynamics simulation. Five kinds of heterogemini molecules are involved, and a variety of novel morphologies have been obtained. Results based on detailed comparisons among themselves and with traditional symmetric gemini surfactant show the proportion of hydrophilic to hydrophobic chain lengths in one monomer is the most important, more difference between proportions in the two monomers can induce more diverse self-assembly morphologies. The second important is the hydrophilic chain length, in which a small change can lead to obvious difference in self-assembly behaviors. While the length of hydrophobic chain has a less important influence, only the concentration for self-assembly morphologies appearing can be affected by its change. The microscopic morphology of heterogemini surfactant in its self-assembly structure can be embodied through its radius of gyration. Our simulation results can undoubtedly provide a theoretical guide to further research towards self-assembly behaviors of heterogemini surfactants and practical applications of these matters.     

联苯二甲酸铒(Ⅲ)配合物的合成及其晶体结构与热性能

2,2’-联苯二酸(H2BPDA)和Er2O3经水热法合成了配合物[Er(BPDA)1.5(H2O)](1),其结构经IR,元素分析和单晶X-射线表征。1属单斜晶系,C2/c空间群的一维链结构,晶胞参数a=20.962 0(11),b=21.3086(11),c=8.156 4(4),β=104.141 0(10)°,V=3 526.8(3)3,Z=8,Dc=2.055 g.cm-3,μ=4.804mm-1,F(000)=2 112,R1=0.019 8,wR2=0.051 0,S=1.061。Er1(Ⅲ)采取八配位的反四棱柱几何构型,而Er2(Ⅲ)采取八配位的四棱柱几何构型,配体BPDA2-的2个羧基分别采用μ2-η2:η1和μ2-η1:η1配位模式,BP-DA2-作为μ3-桥连结Er(Ⅲ)形成1D链结构,进一步通过C-H┈O氢键将1D链连结在一起形成2D和3D结构。1的第一热分解温度为167℃,第二热分解温度为167℃～710℃。