The structure and stability of Si60 and Ge60 cages: a computational study

Structural studies of fullerene-like Si(60) and Ge(60) cages using ab initio methods were augmented by density functional tight-binding molecular dynamics (DFTB-MD) simulations of finite temperature effects. Neither the perfect I(h) symmetry nor the distorted T(h) structures are true minima. The energies of both are high relative to distorted, lower symmetry minima, C(i) and T, respectively, which still preserve C(60)-type connectivity. Both Si(60) and Ge(60) favor C(i) symmetry cages in which Si and Ge vertexes exhibit either near-trigonal or pyramidal geometries. These structural variations imply significant reactivity differences between different positions. The small magnetic shielding effects (NICS) indicate that aromaticity is not important in these systems. The inorganic fullerene cages have lower stabilities compared with their carbon analogs. Si(60) is stable towards spontaneous disintegration up to 700 K according to DFTB-MD simulations, and thus has potential for experimental observation. In contrast, Ge(60) preserves its cage structure only up to 200 K.     

Structural modification of BODIPY: Improve its applicability

The synthesis of biocompatibility and tissue penetrating BODIPY dyes have been summarized.     

N,N′—二(芳磺酰)磺酰亚胺—S—(2—苯并咪唑)钠、银盐的合成及应用

芳磺酰氯胺钠是一类化学活性很强的物质,由它们参予的许多反应已引起化学工作者浓厚的兴趣。Boberg,Koide和Bruchmann等在这方面做了很多工作。Bruchmann用2—巯基吡啶酮与二分子芳磺酰氯胺钠(氯胺T,氯胺Cl,氯胺N,氯胺B和氯胺M)合成了相应的N,N′—二(芳磺酰)磺酰亚胺—S—(2—吡啶)钠盐化合物。众所周知2—巯基苯并咪     

藏红T作为电化学探针线扫极谱法测定透明质酸

在pH 1.5的B ritton-Rob inson(B-R)缓冲溶液中,藏红T(ST)在-0.35 V(vs.SCE)处有一个灵敏的线性扫描二阶导数极谱还原波。当加入一定量的透明质酸(HA)后,由于此条件下ST带正电荷,而HA带负电荷,两者之间通过静电力作用形成一种生物超分子复合物,导致溶液中游离的ST的浓度降低,相应的还原峰电流降低。实验优化了结合反应条件和电化学测定条件。在最佳条件下,还原峰电流的降低值与HA的浓度在3.0~100.0 mg/L范围内呈线性关系,线性回归方程为Δip(″nA/s-2)=27.23 15.18C(mg/L)(n=14,r=0.996),本方法成功应用于HA模拟样品的测定。     

A thin-layer spectroelectrochemical study of 3,3′,5,5′-tetramethylbenzidine at SnO2:F film optically transparent electrode

The electrooxidation of 3,3′, 5,5′-tetramethylbenzidine (TMB) is dependent on the pH value of Britton-Robinson (B-R) buffer solution. In this work, the electrooxidation behavior of TMB was investigated with a SnO2:F film optically transparent thin-layer spectroelectrochemical cell. TMB underwent one two-electron electrooxidation process in the pH range from 2.0 to < 4.0, and two successive one-electron electrooxidation processes in the pH range from 4.0 to < 7.0 in the B-R buffer solution. At pH 6.5, the electrooxidative product of TMB generated a subsequent chemical reaction to yield an azo compound. Several spectroelectrochemical techniques, such as thin-layer cyclic voltammetry, thin-layer cyclic voltabsorptometry, thin-layer potential-controlled electrolysis absorptometry, thin-layer single-potential-step chronoabsorptometry, thin-layer double-potential-step chronoabsorptometry, thin-layer single-potential-step open-circuit relaxation chronoabsorptometry, were applied to this investigation. The formal potential E^0′ and the electron transfer number corresponding to the electrooxidation of TMB in B-R buffer solution, and the reaction rate constant of the subsequent chemical reaction were determined.     

Structures and energies of isolobal (BCO)n and (CH)n cages

The structures and energies of isolobal (CH)n and (BCO)n polyhedral species, computed at the B3LYP density functional theory level, reveal contrasts in behavior. The strain energies of the (BCO)n cages are much smaller. Also unlike the (CH)n cages, the most stable (BCO)n polyhedra (n > or = 10) prefer structures with the largest number of three-membered rings. The planar (or nearly planar) faces of the cage systems were modeled by computations on planar, isoelectronic (CH2)n (Dnh) and (HBCO)n (Cnv) rings. While the strain energies of all the planar carbon rings, relative to the most stable D5h (CH2)5, were large, the strain energies of all the planar (HBCO)n (Cnv) rings were small. Remarkably, the three-membered (HBCO)3 (C3v) ring was the most stable. Finally, large (BCO)n systems prefer tubelike rather than cage structures.     

Voltammetric studies on the interaction of amikacin with methyl blue and its analytical application

A new method to determine the concentration of amikacin(AMK)using methyl blue(MB)as electrochemical probe was developed in this paper.In pH 4.5 Britton-Robinson(B-R)buffer solution,the MB reacted with AMK to form ion association complexes,which led to the reductive peak current of MB at-0.275 V(versus SCE)to decrease,and the decreases were linear with the concentration of AMK in the range of 1.0-60.0 mg/L,the regression of equation isΔIp(nA)=-8.48 102.36c(mg/L), correlation coefficientγis 0.997.The conditions for determining the concentration of AMK using linear sweep voltammetry(SLV) were optimized.The method was used to determine the content of amikacin commercially available with satisfactory results.     

三维经阴道超声对宫腔粘连患者宫腔容积及血流变化的评估

为了观察宫腔粘连患者行三维经阴道超声(3D-TVS)检查时宫腔容积及血流的变化,本文纳入2016年11月~2018年11月于我院收治的68例宫腔粘连患者为观察组,另选取同期来我院体检的健康女性68例为对照组,均于月经周期中晚期行3D-TVS检查,并以病理诊断结果为金标准,观察了3D-TVS诊断宫腔粘连的灵敏度及特异度。同时,对比了两组患者3D-TVS参数如子宫内膜容积(EV)、血流指数(FI)、血管血流指数(VFI)及内膜区血管指数(VI)的变化,并分析了宫腔粘连不同分级患者上述3D-TVS参数的变化情况。经病理确诊的68例患者中,3D-TVS诊断为宫腔粘连64例,其中Ⅰ型21例,Ⅱ型31例,Ⅲ型9例,Ⅳ型3例。3D-TVS诊断宫腔粘连的灵敏度为92.65%,特异度为98.53%,准确率为95.59%,阳性预测值为98.44%,阴性预测值为93.06%,Kappa值为0.91。观察组EV、FI、VFI、VI均显著低于对照组。Ⅰ型宫腔粘连者EV显著大于Ⅱ、Ⅲ、Ⅳ型者,Ⅱ型宫腔粘连者EV显著大于Ⅲ、Ⅳ型者,Ⅲ型宫腔粘连者EV显著大于Ⅳ型者;Ⅰ型宫腔粘连者的VFI、VI显著大于Ⅲ、Ⅳ型者。上述结果证实3D-TVS对宫腔粘连患者宫腔容积及血流变化具有重要的评估价值。     

Modification of silica surfaces by grafting of alkyl chains. I — Characterization of silica surfaces by inverse gas-solid chromatography at zero surface coverage

Summary The surface properties of fumed and precipitated silicas were modified by esterifying their surface silanol groups with methanol and hexadecanol. Characterization of the silicas by inverse gas-solid chromatography at zero surface coverage revealed that the surface properties of the initial solids varied with their method of preparation. Thermodynamic functions (ΔG, ΔH, ΔS) changed significantly with grafting. Grafting resulted in an significant decrease in the dispersive and specific components of the surface free energy of the solid. The changes were shown to be dependent on the method of preparation of the filler (the biggest effects being particularly observed with fumed silicas) and on the size of the grafted chain (hexadecyl grafts yielding the largest change).     

Fabrication of CuO pricky microspheres with tunable size by a simple solution route

A simple aqueous solution route was introduced for the fabrication of CuO pricky microspheres (CPMs) using CuCl(2) x 2H(2)O, Na(2)(C(4)H(4)O(6)) x 3H(2)O and NaOH as starting materials. The CPMs were composed of compressed nanothorns exhibiting tapering feature with tip size of less than 10 nm, and the size of CPMs could be tuned from 100-200 nm to 4-6 microm. The effects of the molar ratios of tartrate anions and NaOH to Cu(2+) cations, reagent concentration, and reaction temperature on the products were investigated, showing that the morphology of CPMs was determined by the molar ratio of tartrate to Cu(2+) cations and the size was greatly affected by reagent concentration and the molar ratio of NaOH to Cu(2+) cations in the precursor solution. The fabrication of CPMs went through rapid nucleation of Cu(OH)(2), aggregation and in situ dehydration of Cu(OH)(2), oriented-aggregation-based growth, and normal crystal growth of CuO nanothorns. The nucleation and crystal growth were successfully separated by controlled releasing of Cu(2+) and OH(-) ions through the reversible reaction of Cu(2+) cations, OH(-), and C(4)H(4)O(6)(2-) anions.