Synthesis and Characterization of ZnO Bicrystalline Nanosheets Grown via Ag-Au Alloy Catalyst

ZnO bicrystalline nanosheets have been synthesized by using Ax=AU1-x alloy catalyst via the vapor transport and condensation method at 650 ℃. High resolution transmission electron microscopy characterization reveals a twin boundary with {01-13} plane existing in the bicrystalline. A series of control experiments show that both AgxAu1-x alloy catalyst and high supersaturation of Zn vapor are prerequisites for the formation of ZnO bicrystalline nanosheet. Moreover, it is found that the density of ZnO bicrytalline nanosheets can be tuned through varying the ratio of Ag to Au in the alloy catalyst. The result demonstrates that new complicated nanostructures can be produced controllably with appropriate alloy catalyst.     

An organic hydrogel as a matrix for the growth of calcite crystals

The growth of calcite in an aqueous gel of was studied and the appearance of the crystals was found to change over time. Crystals removed from the gel at progressively longer times showed severely affected surfaces resulting from dissolution. If crystals were removed from the gel after 3.5 hours, at which point there were no etch pits, and then placed in either buffer or pure water, etch pits, similar to those observed on crystals that are left in the gel, were observed. Control calcite crystals exposed to similar conditions (water or buffer) show no significant dissolution after equivalent times. A probable cause of the altered dissolution is the non-specific occlusion of gelator aggregates at sites of imperfection. The gel appears to provide a microenvironment in which the molecules that form the matrix also participate in the crystallization. This system allows the study of the unique properties of a gel for influencing the nucleation and growth of inorganic crystals, some of which may be important for better understanding biomineralization.     

Insights on the mechanism for synthesis of methylenedianiline from aniline and formaldehyde through HPLC-MS and isotope tracer studies

The mechanism for synthesis of 4,4-methylenedianiline(MDA) via condensation reaction of aniline with formaldehyde has been studied extensively in this paper.The intermediate and by-products were isolated and identified.The combination of isotope labeling and HPLC-MS characterizations disclosed that the reaction proceeded through an S_N2 reaction mechanism.Moreover,the effect of aniline/formaldehyde molar ratio on the formation of MDA was investigated.This work would be of significance to understand the reaction mechanism deeply and provide valuable information for further improving the yield of desired product.     

Synthesis and positive inotropic evaluation of 1-(benzylamino)-3-(4,5-di-hydro[1,2,4]trizaolo[4,3-a]quinolin-7-yloxy)propan-2-ol derivatives

In an attempt to search for more potent positive inotropic agents,a series of 1-(benzylamino)-3-(4,5-dihydro[1,2,4]trizaolo[4,3- a]quinolin-7-yloxy)propan-2-ol derivatives was synthesized in four steps using 6-hydroxy-3,4-dihydro-2(1H)-quinolinone as a starting material,and their positive inotropic activities were evaluated by measuring the coronary blood flow(CBF)and the left ventricular pressure(LVP)followed by calculating the rate of pressure development(dp/dt_(max)values)in the preparation of rat Lan...     

A new flavonoid from Selaginella tamariscina

6-(2-Hydroxy-5-acetylphenyl)-apigenin (1),a new flavonoid with a phenyl substituent,was first isolated from Selaginella tamariscina.Its structure was elucidated on the basis of 1D and 2D NMR as well as ESI-HR-MS spectroscopic analysis.     

Hydrothermal Synthesis and Crystal Structure of a Keggin Polyoxometalate [Co^Ⅱ（2,2′-bipy）2（H2O）]2[SiW^Ⅵ12O40]·2H2O

A Keggin-type tungstosilicate compound [Co^Ⅱ（2,2′-bipy）2（H2O）]2[SiW^Ⅵ12O40]·2H2O 1 （bipy = bipyridine） was prepared by a hydrothermal method for the first time. Single-crystal X-ray diffraction revealed that 1 （C40H40Co2N8O44SiW12） crystallizes in the triclinic system, space group P1 with a = 10.4979（6）, b = 13.3946（7）, c = 13.5756（8）A, α= 70.0769（18）, β = 68.910（3）, γ = 74.186（4）°, V = 1649.84（16）A^3, Mr = 3688.95, Z = 1, Dc = 3.713 mg·m^-3, μ = 21.432 mm^-1, F（000） = 1644, S = 1.058, the final R = 0.0511 and wR =0.1023 for 6523 observed reflections （I 〉 2σ（I））. Compound 1 consists of two coordinated cation fragments [Co^Ⅱ（2,2′-bipy）2（H2O）]^2＋, one normal Keggin polyanion unit [SiW^Ⅵ12O40]^4- and two lattice water molecules. To be noted, each polyanion unit is linked to two cation fragments by its two surface terminal oxygen atoms and two cobalt atoms of two cation fragments forming an organic-inorganic hybrid unit in 1. Furthermore, the compound shows strong photoluminescence property in the solid state at room temperature.     

Thermal,chemical, biological and mechanical properties of chitosan films with powder of eggshell membrane for biomedical applications

Journal of Thermal Analysis and Calorimetry - The objective of this work was to develop chitosan films incorporated with the eggshell membrane powder (MCO) by the solvent evaporation method with...     

Acid-base cooperativity of heterogeneous catalyst containing acidic framework and sterically hindered base for aldol condensation

A bifunctional heterogeneous catalyst containing two mutually incompatible acidic and basic sites,which exhibits cooperative catalytic behavior in the aldol condensation of acetone and various aldehydes,was synthesized by postgrafting of 1,5,7- triazabicyclo[4.4.0]dec-5-ene(TBD,a sterically hindered organic base) onto Al-MCM-41 molecular sieve.     

一个极限定理

本文给出一个与同余和有关的极限定理,它在计算机模式识别中有应用。