ZnO超微粒子的EPR特性和光催化性能

利用XRD,TEM,XPS和EPR等研究了ZnO超微粒子的EPR特性和光催化性能.前驱物碱式碳酸锌在320,430,550和700℃经热处理制得的ZnO超微粒子粒径分别为13.5,19.3,26.1和38.5nm,属六方晶系纤锌矿结构;室温下ZnO超微粒子表现出稳定的单一谱线的EPR信号,其强度随粒径的增大而减小.而在液氮温度下,ZnO超微粒子的EPR谱具有6条强度不等的超精细谱线,在光催化氧化C₇H₁₆和SO₂过程中,其光催化活性随其EPR信号强度的减小而下降.说明O₂-空位在光催化反应中起重要作用.     

几种双核簇合物的EPR谱

本文报导了四个双铜,四个双钼簇合物的EPR谱。这些谱可分成两类:一种类似于单核化合物的EPR谱,谱参数与单核谱相近,但谱强度较单核谱弱,文中称之为“碎片型”;另一类的谱参数与双核偶合的体系相同,谱的强度与双核偶合程度有关、反映双核偶合成簇的性质,称之为“簇型”。两类谱受温度和溶剂的影响分别呈现正常与反常的顺磁性。本文对它们与簇合物结构-性质间的关系作了初步探讨。     

蝎型螯合过渡金属配合物的研究(Ⅰ)──氢三(3-对甲氧基苯基吡唑-1)硼酸铜(Ⅱ)配合物的合成、表征及晶体结构

合成了一种蝎合配体氢三(3-对甲氧基苯基吡唑-1)硼酸钾KTp^An.室温下,等物质的量的KTp^An与Cu(O₂CMe)₂·H₂O在THF溶液中反应得配合物[Cu(O₂CMe)(HB{pz^An}₃)](Ⅰ);KTp^An与等物质的量的无水CuCl₂反应则得不同的产物CuCl(pz^AnH)(HB{pz^An}₃)(Ⅱ).对标题化合物进行了元素分析、红外光谱、顺磁共振谱和电化学研究.配合物Ⅰ和Ⅱ的苯溶液的EPR谱研究表明中心金属铜的基态电子构型为拟轴对称的{dx₂-y₂}¹.Ⅱ的X射线衍射晶体结构分析表明,铜离子的配位环境为畸变的四方锥结构,与其配位的有配体Tp^An上3个吡唑氮原子、3-对甲氧基苯基吡唑氮原子和1个氯离子,晶体属空间群P2₁/c.a=1.1643(2)nm,b=2.7081(5)nm,c=1.4494(3)nm,β=105.37(3)°,V=4.4066(14)nm³,Z=4,R=0.0604.分子中存在弱的分子内氢键N-H…Cl,其中Cl₁…N₁=0.3009nm,∠Cl1…H1B-N1=120.3°.     

三核钼原子簇化合物的EPR和电子结构

本文报道一个新的三核钼原子簇化合物在室温和77K固态和液态的EPR谱,这些谱均呈现出a,b两套谱线的叠加,分析谱线的强度比,线宽和谱参数,认为g值较大的a谱归属于三核钼原子簇化合物,而b谱归属于单核钼杂质。从由X射线晶体结构方法确定的空间结构出发,三核钼原子簇化合物可能有两种分子形式:Mo3(μ3-S)(μ2-S)3Cl[S2P(OEt)2]4 1Mo3(μ3-S)(μ2-S)(μ2-Cl)2Cl[S2P(OEt)2]4 2分别用简单量子化学理论和EHMO法计算出未配对电子所处的分子轨道,求出g1和g1,并与EPR实验值相比较,认为该化合物的分子式应为2,簇骼{Mo3}属七电子体系,在77K温度下,其未配对电子主要局域在三个钼原子所组成的近似等腰三角形簇骼的顶点钼原子周围。     

三种Gd~(3+)直链醚席夫碱配合物的EPR波谱研究

本文考察了三种新的Gd~(3+)直链醚席夫碱配合物在不同温度下的多晶粉末和它们在有机溶剂中的EPR波谱,首次观测到Gd~(3+)配合物多晶粉末谱显现九个特征峰,低温玻璃态显现四个特征峰,藉S=7/2体系的自旋Hamilton作出颇为满意的解释。文中还揭示了EPR图谱特征与配合物中晶体场强度和Gd~(3+)周围局部对称性的关系,估算了配合物的晶体场参数b_2~0不对称参数λ’,得到一系列规律性及新结果。     

乙酰胺基阿维菌素的成分分析与鉴定

用元素分析,13CNMR,IR,以及正负离子质谱对乙酰胺基阿维菌素（EPR）工业品的主要成分进行了确证.用HPLC-ESI MS对EPR工业品的组成成分进行了分离,并根据其准分子离子和特征紫外光谱鉴定了它的5个组分,其主要成分是EPR-B1a.     

部分还原二氧化钛的NMR和EPR研究（英文）

部分还原TiO_2纳米材料由于具备可见光催化及降解活性而引起广泛研究关注。本研究采用~(17)O和~1H魔角旋转固体核磁共振(MASNMR)谱学,结合电子顺磁共振(EPR)谱学研究了锐钛矿型部分还原TiO_2(Re-A-TiO_2)纳米颗粒的表面结构,并与非还原样品(A-TiO_2)作了对比。EPR结果显示,Re-A-TiO_2的顺磁物种(氧空位(OV)和Ti3+)含量远高于A-TiO_2,并且EPR信号的强度受吸附水含量的显著影响,我们结合~1H NMR数据,探讨了这一过程中的结构变化。~(17)O NMR谱中,两种样品除了表面2配位氧(m2-O)的信号有明显差异外,还发现在Re-A-TiO_2表面有更多的羟基(OH),显示该样品表面有较高比例的(001)晶面暴露。综合EPR和NMR数据,可推断羟基主要来源于顺磁中心与吸附水分子反应。~1H→~(17)O交叉极化(CP)-MAS和二维异核相关(2D HETCOR)NMR谱确认了强吸附的水物种和一种羟基的归属,另外位于约11 ppm的~1H NMR信号可归属为分子内氢键中的氢物种。这些表面结构的差异应与两种材料光降解甲基橙性能差别直接相关。     

一种新的16金属笼状物[HN(C_2H_5)_3]_4-[Mo_3~VMo_6~(VI)V_7~(IV)O_(40)(PO_4)]·2[N(C_2H_5)_3]的水热合成和结构

报道了一种新的杂多化合物[HN(C_2H_5)_3]_4-[Mo_3~VMo_6~(VI)V_7~(IV)O_(40)(PO_4)]·2[N(C_2H_5)_3]的合成,并用元素分析、EPR、IR谱、及X--射线单晶衍射等手段进行了表征。结果表明,该杂多酸盐属于单斜晶系,空间群P21/n,a=14.0841(3),b=14.2505(3),c=19.6089(3)?b=94.213(1),V=3925.0(1)?,Z=2,Dc=2.171g/cm3,Mr=2566.18,m=2.284mm-1,F(000)=2516,R=0.0477,wR=0.0945.杂多阴离子是1个16金属笼状物,笼中心包含1个PO4四面体客体。     

单晶Cr~(3+)/Na_3(AlMo_6O_(24)H_6)·8H_2O的EPR研究

本文研究了Na_3[CrMo_6O_(24)H_6]·8H_2O单晶磁性稀释在同构的Na_3[CrMo_6O_(24)H_6]·8H2O单晶后Cr(Ⅲ)离子在室温X波段的EPR波谱。从主轴平面上的EPR数据用最小二乘法获得了g张量的主值g_(ZZ)=1.904,g_(XX)=1.973,g_(YY)=1.933和零场分裂张量参数D=0.275cm~(-1),E=0.05cm~(-1)。根据这些实验参数,计算了磁场处在主轴平面上相对主轴的不同取向的磁性基态能级,并导出了主轴平面上EPR谱随磁场取向角度变化的等频曲线。这个计算曲线与主轴平面上实验数据曲线符合很好。     

异双Schiff碱及其稀土配合物的合成、机理与波谱

利用2,6-二氨基己酸(赖氨酸)具有两端不对称结构的－NH~2基,合成了一端与水杨醛,另一端与2,4-二羟基苯甲醛缩合形成空间结构不对称的异双Schiff碱及其与稀土元素配合物。以元素分析、热分析、摩尔电导、红外光谱、EPR以及^1HNMR,^1^3C-^1HCOSY谱、固体高分辨^1^3C谱等表征,研究了这类不对称Schiff碱的形成机理和配位方式。     

Geometry Optimization of Ba2+(H2O)n Clusters Using a Fast Hybrid Global Optimization Algorithm

A global optimization called fast hybrid global optimization algorithm was proposed based on genetic algorithm, fast simulated algorithm and conjugated gradient algorithm. We employ it to search the global minimum energy structures of Ba²⁺(H₂O)_n clusters for n = 1–30 within the TIP4P model. The results show that Ba²⁺(H₂O)_n clusters have the n+0 structure while n = 1–8. When n is in the range 9 ≤ n ≤ 18, the number of water molecules in the first shell around the barium ion is 8 and the other water molecules arrange in the outer shell. In the global minimum structure of Ba²⁺(H₂O)₁₉, the number of the first shell water molecules adds up to 9, and the value is kept until n = 30. According to the computational results, a conclusion that hydration numbers for Ba²⁺ is 9 can be drawn, which is in agreement with the result by a Monte Carlo simulation.     

Computer-assisted structure simulation, synthesis, and phase formation of molybdophosphates A1−x Zr2(PO4 3−x (MoO4)x (A is an alkali metal)

Structure simulation is performed for molybdophates of variable composition A_1?x Zr₂(PO₄)_3?x (MoO₄)_x, where A is Na (0≤x≤0.6), K (0≤x≤0.6), K (0≤x≤0.3), Rb (0≤x≤0.2), or Cs (0≤x≤0.1), using the minimization of the interatomic interaction energy; these molybdophosphates crystallize in the NaZr₂(PO₄)₃ (NZP) structure type. The results of the computer-assisted structure simulation are verified by the synthesis of the molybdophosphates and their characterization by X-ray powder diffraction and IR spectroscopy. The crystallization field of the NZP molybdophosphate shrinks as the alkali cation size increases. The key factors that govern the stability of the NZP structure in alkali zirconium molybdophosphates are determined.     

Radial distribution function of a hard-sphere fluid for the nearest neighbor surroundings

An expression for RDF as a function of two variables, the distance r and the packing factor η, was obtained by approximating the results of Monte Carlo simulation of a hard-sphere fluid. The mean square accuracy of the expressions presented is about ±0.0002 (1 ≤ r ≤ 1.5, 0 ≤ η ≤ 0.5). A continuous extension of RDF to the region of r < 1 is proposed, which provides the continuity of the first and second derivatives of RDF at the point r = 1. Analysis of the problem of determining the hard sphere diameter in WCA theory of simple liquids shows that the proposed expression makes it possible to directly calculate the hard sphere diameter without any simplifying approximations.     

Die bestimmung kinetischer parameter endothermer zersetzungsreaktionen unter nicht-isothermen bedingungen

By using the kinetic parameters calculated from non-isothermal measurements according to Freeman and Carroll a computer programm is given, which permits the determination of the more probable reaction mechanism by use of 17 different kinetic equations. The computer programm includes the kinetic equation for chemical reaction, nucleation, phase boundary reaction and diffusion and can easily be extended to other equations. The evaluation of the experimental values by a distinct kinetic equation is quantitatively characterized by means of the correlation coefficient.The kinetic parameters are calculated on the basis of a regression analysis. By dividing the thermogravimetric curve in different reaction intervals a differential calculation is possible.Decomposition of CaCO₃, MgCO₃ and CaSO₄·2H₂O is discussed from the results of the computer calculation. It is seen that the kinetic parameters and the reaction mechanism are not constant during the reaction. Further experiments for a physical interpretation are being carried out.     

Moment analysis method as applied to the 2S --> 2P transition in cryogenic alkali metal/rare gas matrices

The moment analysis method (MA) has been tested for the case of 2S --> 2P ([core]ns1 --> [core]np1) transitions of alkali metal atoms (M) doped into cryogenic rare gas (Rg) matrices using theoretically validated simulations. Theoretical/computational M/Rg system models are constructed with precisely defined parameters that closely mimic known M/Rg systems. Monte Carlo (MC) techniques are then employed to generate simulated absorption and magnetic circular dichroism (MCD) spectra of the 2S --> 2P M/Rg transition to which the MA method can be applied with the goal of seeing how effective the MA method is in re-extracting the M/Rg system parameters from these known simulated systems. The MA method is summarized in general, and an assessment is made of the use of the MA method in the rigid shift approximation typically used to evaluate M/Rg systems. The MC-MCD simulation technique is summarized, and validating evidence is presented. The simulation results and the assumptions used in applying MA to M/Rg systems are evaluated. The simulation results on Na/Ar demonstrate that the MA method does successfully re-extract the 2P spin-orbit coupling constant and Landé g-factor values initially used to build the simulations. However, assigning physical significance to the cubic and noncubic Jahn-Teller (JT) vibrational mode parameters in cryogenic M/Rg systems is not supported.     

Pu在Gd2Zr2O7基质中的模拟固化: (Gd1-xCex)2Zr2O7+x的热物理性能研究

采用高温固相反应,以NaF作助熔剂,在1000 ℃的温度下合成了锕系元素Pu的模拟固化体(Gd_1-xCe_x)₂Zr₂O_7+x (0 ≤ x ≤ 0.7).研究了模拟固化体的物相、热膨胀系数(TEC)、热导率(TC)随温度及组成的变化规律.粉末X射线衍射(XRD)测试结果表明: Gd₂Zr₂O₇基质本身呈弱有序烧绿石结构,而用Ce⁴⁺取代Gd³⁺的模拟固化体都呈缺陷萤石结构. (Gd_1-xCe_x)₂Zr₂O_7+x的Ce(3d) X射线光电子能谱(XPS)有六个峰,结合能分别位于881.7, 888.1, 897.8, 900.4, 907.1, 916.1 eV处,与CeO2的XPS图谱非常相似,说明Ce为四价.随着温度的升高,所有样品的热膨胀系数总体上呈增大趋势.在室温至750 ℃附近,大部分样品的热导率随温度的升高而降低,之后热导率又呈小幅上升.在相同温度下,固化体(Gd_1-xCe_x)₂Zr₂O_7+x (0 ≤ x ≤ 0.7)的热膨胀系数及热导率随组成变化呈相同趋势:在0 ≤ x ≤ 0.1范围内随x的增大而增大,随后在x = 0.1-0.7时逐渐减小.     

Molecular dynamics simulations of cyclosporin A: The crystal structure and dynamic modelling of a structure in apolar solution based on NMR data

Summary The conformation of the immunosuppressive drug cyclosporin A (CPA), both in apolar solution and in crystalline state, has been studied by computer simulation techniques. Three molecular dynamics (MD) simulations have been performed: one modelling the crystal structure and two modelling the structure in apolar solution, using a restrained MD approach in which data from nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy are taken into account. The simulation of the crystalline state (MDC) concerns a system of 4 unit cells containing 16 cyclosporin A molecules and 22 water molecules, which is simulated using crystalline periodic boundary conditions. The simulations modelling the apolar solvent conformation (MDS) concern one isolated cyclosporin A molecule. In these simulations an extra term in the interatomic potential function is used, which forces the molecule to satisfy a set of 57 atom-atom distance constraints originating from nuclear Overhauser effects (NOEs) obtained from NMR spectroscopy and one distance constraint deduced from IR spectroscopy.From a comparison of the results of the crystal simulation to those of the X-ray experiment in terms of structure, atomic fluctuations, hydrogen bond pattern, etc., it is concluded that the force field that is used yields an adequate representation of crystalline cyclosporin A. Secondly, it is shown that the dynamic modelling technique that is used to obtain a structure in a polar solution from NMR distance information works well. Starting from initial conformations which have a root mean square difference of 0.14 nm both distance restrained MD simulations converge to the same final solution structure. A comparison of the crystal structure of cyclosporin A and the one in apolar solution shows that there are significant differences. The overall difference in atomic positions is 0.09 nm for the C_x atoms and 0.17 nm for all atoms. In apolar solution, the molecule is slightly more bent and the side chains of 1 MeBmt and 10 MeLeu adopt a different conformation.Abbreviations MeBmt (4R)-4[(E)-2-butenyl]-4-methyl-l-Threonine - MD Molecular dynamics - EM Energy minimization - MDC Molecular dynamics simulation of the crystal - MDS1 Restrained molecular dynamics simulation to obtain the structure in solution starting from the crystal structure - MDS2 Like MDS1, but starting from the SMS structure - SMS Proposed structure in solution, obtained by model building - XRAY An X-ray structure - CPA Cyclosporin A - NMR Nuclear magnetic resonance spectroscopy - NOE Nuclear Overhauser enhancement - MDS1 Mean simulated structure obtained by averaging over the time period 20–40 ps of the MDS1 simulation - MDS2 Mean simulated structure obtained by averaging over the time period 10–30 ps of the MDS2 simulation - Mean simulated structure obtained by averaging over the time period 7–15 ps and over the 16 asymmetric units in the computational box of the MDC simulation.     

Driven Brownian coagulation of polymers

We present an analysis of the mean-field kinetics of Brownian coagulation of droplets and polymers driven by input of monomers which aims to characterize the long time behavior of the cluster size distribution as a function of the inverse fractal dimension, a, of the aggregates. We find that two types of long time behavior are possible. For 0≤a<1/2 the size distribution reaches a stationary state with a power law distribution of cluster sizes having exponent 3/2. The amplitude of this stationary state is determined exactly as a function of a. For 1/2相似文献   

DSC曲线的模拟及峰面积计算

<正> 差示扫描量热法(DSC)曲线峰面积的简便、准确地计算是热分析工作者所关注的。七十年代初Lind、Wendlandt等人曾设想用计算机处理数据。七十年代后期,国外已有DSC和微型机联用。但仍有采用求积仪(或面积计planimeter),并认为求积仪比“剪纸称重”法偏差低。     

Topochemical synthesis of co-fe layered double hydroxides at varied fe/co ratios: unique intercalation of triiodide and its profound effect

Co-Fe layered double hydroxides at different Fe/Co ratios were synthesized from brucite-like Co(2+)(1-x)Fe(2+)(x)(OH)(2) (0 ≤ x ≤ 1/3) via oxidative intercalation reaction using an excess amount of iodine as the oxidizing agent. A new redoxable species: triiodide (I(3)(-)), promoted the formation of single-phase Co-Fe LDHs. The results point to a general principle that LDHs with a characteristic ratio of total trivalent and divalent cations (M(3+)/M(2+)) at 1/2 may be the most stable in the oxidative intercalation procedure. At low Fe content, e.g., starting from Co(2+)(1-x)Fe(2+)(x)(OH)(2) (x < 1/3), partial oxidation of Co(2+) to Co(3+) takes place to reach the M(3+)/M(2+) threshold of 1/2 in as-transformed Co(2+)(2/3)-(Co(3+)(1/3-x)-Fe(3+)(x)) LDHs. Also discovered was the cointercalation of triiodide and iodide into the interlayer gallery of as-transformed LDH phase, which profoundly impacted the relative intensity ratio of basal Bragg peaks as a consequence of the significant X-ray scattering power of triiodide. In combination with XRD simulation, the LDH structure model was constructed by considering both the host layer composition/charge and the arrangement of interlayer triiodide/iodide. The work provides a clear understanding of the thermodynamic and kinetic factors associated with the oxidative intercalation reaction and is helpful in elucidating the formation of LDH structure in general.