High-yield synthesis of ultrathin silica-based nanosheets and their superior catalytic activity in H2O2 decomposition

Ultrathin silica-based nanosheets with a thickness of ～1 nm are fabricated in a low-cost and high-yield system excluding alkali metal ions. Unlike the Na-zeolites with a long capillary and microporous structure, the ultrathin nanosheets exhibit highly effective surface and active sites. As a result, the 0.4 wt% Pt-loaded nanosheets exhibit superior catalytic activity in H(2)O(2) decomposition with an O(2) evolution rate of 342.5 mL g(-1) min(-1) in a clean aqueous system.     

Porous,Conductive Metal‐Triazolates and Their Structural Elucidation by the Charge‐Flipping Method

A new family of porous crystals was prepared by combining 1H‐1,2,3‐triazole and divalent metal ions (Mg, Mn, Fe, Co, Cu, and Zn) to give six isostructural metal‐triazolates (termed MET‐1 to 6). These materials are prepared as microcrystalline powders, which give intense X‐ray diffraction lines. Without previous knowledge of the expected structure, it was possible to apply the newly developed charge‐flipping method to solve the complex crystal structure of METs: all the metal ions are octahedrally coordinated to the nitrogen atoms of triazolate such that five metal centers are joined through bridging triazolate ions to form super‐tetrahedral units that lie at the vertexes of a diamond‐type structure. The variation in the size of metal ions across the series provides for precise control of pore apertures to a fraction of an Angstrom in the range 4.5 to 6.1 Å. MET frameworks have permanent porosity and display surface areas as high as some of the most porous zeolites, with one member of this family, MET‐3, exhibiting significant electrical conductivity.     

Graphene-supported hemin as a highly active biomimetic oxidation catalyst

Well supported: stable hemin-graphene conjugates formed by immobilization of monomeric hemin on graphene, showed excellent catalytic activity, more than 10 times better than that of the recently developed hemin-hydrogel system and 100 times better than that of unsupported hemin. The catalysts also showed excellent binding affinities and catalytic efficiencies approaching that of natural enzymes.     

Insight into the activity of efficient acid–base bifunctional catalysts for the coupling reaction of CO2

The fixation of carbon dioxide with epoxide catalysed by a series of carboxylic acidic functionalised ionic liquids (ILs) catalysts is investigated by density functional theory method. Except for the catalysts reported by the experiment, the catalytic activity of a new designed catalyst (4c see Scheme 1) is also explored. These ILs are categorised into four groups according to the different cation structures and number of functional groups. The effects of different chain length, anion, and cation structure on the catalytic activity are explored. The elongation of alkyl chain length in cation will increase the product yield, while increasing the chain bulk has almost negligible effect on the enhancement of catalytic activity. Utilisation of imidazole group as the cation is better than pyridine group. And the cation with two functional groups will have a better catalytic activity than that with one functional group.     

非Lipschitz系数下随机泛函微分方程适度解的存在唯一性及其渐近性态(英文)

本文主要运用Picard迭代和算子分数次幂方法,讨论了随机时滞偏微分方程适度解的存在性与唯一性,并对解的渐近性态进行了研究.这里方程的系数不满足Lipschitz条件,时滞r>0为有限的.最后给出了一个非Lipschitz条件的例子.     

Highly Selective and Sensitive Chemosensor for Hg2+ Based on the Naphthalimide Fluorophore

A new OFF-ON fluorescent chemosensor (H1) composed of a naphthalimide fluorophore and a 6-[(quinolin-8-yloxy)methyl]pyridin-2-ylmethanamine receptor has been synthesized and characterized by infra-red, (1)H NMR, (13)C NMR and mass spectrometry. The developed chemosensor H1 exhibited good turn-on and reversible responses toward Hg(2+), with excellent selectivity and sensitivity, in a neutral buffered aqueous solution. Other common metal ions did not interfere with the fluorescence-enhancement response to Hg(2+). Furthermore, the chemosensor H1, at a concentration of 10?μM, showed a rapid and linear response toward Hg(2+) in the concentration range 0-10?μM. On addition of 10?μM Hg(2+), the fluorescence intensity of H1 was enhanced about 4-fold. The detection limit was calculated to be 63?nM. The association constant was 1.11?×?10(5)?M(-1). The fluorescence quantum yield and lifetime of H1/Hg(2+) were 0.42 and 3.83?ns, respectively.     

溴化1-十二烷基-3-甲基咪唑与甲基橙的相互作用

利用电导法和表面张力法,研究了离子液体表面活性剂溴化1-十二烷基-3-甲基咪唑(C12mimBr)与阴离子染料甲基橙(MO)之间的相互作用。 通过分别测定C12mimBr、MO以及C12mimBr与MO混合溶液的电导率,计算了C12mimBr与MO的结合特性。 C12mimBr与MO以等摩尔比结合,在288.1、298.1和308.1 K下的结合常数分别为4.89×105、4.88×104和5.76×103 L/mol,该结合反应属于焓驱动的自发放热反应。 分别测定了C12mimBr与MO等摩尔混合体系及其在NaBr溶液中的临界胶束浓度(cmc),加入MO使C12mimBr的cmc从9.1×10-3 mol/L降低到7.3×10-5 mol/L,显著提高了C12mimBr的表面活性。     

钌钛复合氧化物及其载铂催化剂的制备与表征

以TiN纳米粉体和RuCl3为前驱体,采用浸渍热分解法合成了Ru0.1Ti0.9O2纳米粉体,并以其为载体利用固相反应制备了Pt/Ru0.1Ti0.9O2催化剂.通过X射线衍射和透射电镜观察到RuO2和TiO2之间形成了金红石相的固溶体,Pt被均匀地担载于Ru0.1Ti0.9O2表面.在0.5 mol/LH2SO4溶液中的极化曲线测试发现担载Pt与Ru0.1Ti0.9O2具有协同作用,因而具有优异的析氢、析氧电催化性能.质子交换膜燃料电池测试初步表明,Pt/Ru0.1Ti0.9O2具有高的氧阴极还原反应催化活性,进一步的反极实验证明其具有比Pt/C更高的稳定性.     

Integration with Respect to Fractional Local Time with Hurst Index 1/2 < H < 1

Let Open image in new window be the weighted local time of fractional Brownian motion B ^H with Hurst index 1/2?H?Open image in new window As an application, we investigate the weighted quadratic covariation \([f\big(B^H\big),B^H]^{(W)}\) defined by

$ \left[f\big(B^H\big),B^H\right]^{(W)}_t:=\lim_{n\to \infty}2H\sum_{k=0}^{n-1} k^{2H-1}\left\{f\big(B^H_{t_{k+1}}\big)-f\big(B^H_{t_{k}}\big)\right\} \left(B^H_{t_{k+1}}-B^H_{t_{k}}\right), $

where the limit is uniform in probability and t _k ?=?kt/n. We show that it exists and

Open image in new window

provided f is of bounded p-variation with \(1\leq p<\frac{2H}{1-H}\). Moreover, we extend this result to the time-dependent case. These allow us to write the fractional Itô formula for new classes of functions.

     

水合氢离子团簇从头算和ABEEM/MM的理论研究

应用高水平的从头计算方法和ABEEM/MM模型, 研究了水合氢离子团簇H3O＋(H2O)n (n＝1～6), 优化得到了低能构象, 探讨了其结合能和稳定性, 显示出H3O＋(H2O)3局域结构的优势存在．对H3O＋(H2O)6VIa团簇的ABEEM电荷分布进行分析, 表明第一水合层水分子与水合氢离子之间的氢键相互作用要明显强于与第二水层水分子的氢键相互作用. 研究结果表明, ABEEM/MM方法计算的结果和从头算得到的结果存在很好的一致性.