Ambient Pressure X-ray Photoelectron Spectroscopy Study of Oxidation Phase Transitions on Cu(111) and Cu(110)

The surface structure effect on the oxidation of Cu has been investigated by performing ambient-pressure X-ray photoelectron spectroscopy (APXPS) on Cu(111) and Cu(110) surfaces under oxygen pressures ranging from 10⁻⁸ to 1 mbar and temperatures from 300 to 750 K. The APXPS results show a subsequential phase transition from chemisorbed O/Cu overlayer to Cu₂O and then to CuO on both surfaces. For a given temperature, the oxygen pressure needed to induce initial formation of Cu₂O on Cu(110) is about two orders of magnitude greater than that on Cu(111), which is in contrast with the facile formation of O/Cu overlayer on clean Cu(110). The depth profile measurements during the initial stage of Cu₂O formation indicate the distinct growth modes of Cu₂O on the two surface orientations. We attribute these prominent effects of surface structure to the disparities in the kinetic processes, such as the dissociation and surface/bulk diffusion over O/Cu overlayers. Our findings provide new insights into the kinetics-controlled process of Cu oxidation by oxygen.     

CuCl2-Catalyzed α-Chloroketonation of Aromatic Alkenes via Visible-Light-Induced LMCT

Here we report a copper-catalyzed protocol for the synthesis of α-chloroketones from aromatic alkenes including electron-deficient olefins under visible-light irradiation. Preliminary mechanistic studies show that the peroxo Cu(II) species is the key intermediate and hydroperoxyl (HOO⋅) and chlorine (Cl⋅) radicals can be generated by ligand-to-metal charge transfer (LMCT).     

Ligand-to-metal ratio controlled assembly of nanoporous metal-organic frameworks

Two bilayered metal-organic frameworks with nanoporous channels were synthesized at different ligand-to-metal ratios, which demonstrated an interesting crystal-to-crystal transformation property and a special fluorescent response to the different guest molecules included.     

Analysis of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction combined with gas chromatography

A novel method was developed for the determination of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD). Some experimental parameters that influence the extraction efficiency, such as the type and volume of the disperser solvents and extraction solvents, extraction time, and addition of salt, were studied and optimized to obtain the best extraction results. Under the optimum conditions, high enrichment factors for the compounds were achieved ranging from 824 to 912. The recoveries of fungicides in apples at spiking levels of 20.0 μg kg⁻¹ and 70.0 μg kg⁻¹ were 93.0–109.5% and 95.4–107.7%, respectively. The relative standard deviations (RSDs) for the apple samples at 30.0 μg kg⁻¹ of each fungicide were in the range from 3.8 to 4.9%. The limits of detection were between 3.0 and 8.0 μg kg⁻¹. The linearity of the method ranged from 10 to 100 μg kg⁻¹ for the three fungicides, with correlation coefficients (r ²) varying from 0.9982 to 0.9997. The obtained results show that the DLLME combined with GC–ECD can satisfy the requirements for the determination of fungicides in apple samples. Figure Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD) allows satisfactory determination of fungicides in apple samples     

Synthesis, Crystal Structure and Thermal Analysis of (TAGH)2(TNR)

A new energetic compound (TAGH)₂(TNR) (TAG: triaminoguanidine, TNR: 2,4,6-trinitroresorcinol) was prepared by reacting triaminoguanidine with 2,4,6-trinitroresorcinol (styphnic acid) in aqueous solution under nitrogen atmosphere, and characterized by elemental analysis and Fourier transform infrared (FTIR) spectra. Its crystal structure was determined by single crystal X-ray diffraction analysis. The crystal belonged to a monoclinic, C 2/c space group. The unit cell parameters were as follows: a=2.2892(6) nm, b=1.2802(3) nm, c=1.3661(4) nm, β=111.174(5)°, V=3.7333(16) nm³, and Z=8. The compound consisted of two cations C(N₂H₃)₃⁺ and an anion (C₆HN₃O₈)²⁻. The C(N₂H₃)₃⁺ and (C₆HN₃O₈)²⁻ were bonded together by electrostatic attraction and hydrogen bonds, and this effect made the compound more stable. The thermal analysis of the compound was studied by using differential scanning calorimetry (DSC), thermogravimetry-derivative thermogravimetry (TG-DTG). Under nitrogen atmosphere with a heating rate of 10 K·min⁻¹, the thermal decomposition of the compound contained only one intense exothermic decomposition process in the range of 450.1-477.7 K in the DSC curve, and the decomposition products were nearly gaseous products.     

有机催化不对称Mannich反应

有机催化的不对称合成反应是目前研究最为活跃的领域之一.不对称Mannich反应是合成光学活性β-氨基羰基化合物的有效手段.目前报道的催化不对称Mannich反应的有机催化剂主要有脯氨酸及其衍生物、手性磷酸、手性(硫)脲和金鸡纳碱衍生物等,取得了良好的催化活性和对映选择性.本文评述了各类有机催化剂在有机催化不对称Mannich反应中的应用研究进展,以及不对称诱导反应的机理、催化剂分子结构及反应条件对其催化活性和不对称诱导作用的影响.     

Influence of 3A molecular sieve on tetrahydrofuran (THF) hydrate formation

Visual observation of the THF hydrate formation process in the presence of a 3A molecular sieve has been made at normal atmosphere and below a temperature of zero by microscopy. The results indicate that a 3A molecular sieve can induce the nucleation of the THF hydrate and promote the THF hydrate growth. With the existence of a 3A molecular sieve, the growth rate of THF hydrate is between 0.01 and 0.05 μm/s. In comparison with the system without any 3A molecular sieve, the growth rate increases about 4 nm/s. After the THF hydrate grows into megacryst, the crystals will recombine and partially change under the same condition.     

Ultraselective fluorescent sensing of Hg2+ through metal coordination-induced molecular aggregation

A new type of fluorescent sensor has been developed from a perylene based molecule, N,N'-dideoxythymidine-3,4,9,10-perylene-tetracarboxylic diimide (TT-PTCDI); the strong, highly selective binding between the thymine ligand (T) and Hg2+ ion enables efficient sensing of mercury ions based on a fluorescence quenching mechanism, which is primarily caused by metal-coordination induced molecular aggregation.     

Interpolation inequalities for derivatives in variable exponent Lebesgue–Sobolev spaces

We show the interpolation inequalities for derivatives in variable exponent Lebesgue–Sobolev spaces by applying the boundedness of the Hardy–Littlewood maximal operator on L^p(⋅)$L^{p(\cdot )}$.     

Capillary electrophoresis for simultaneous analysis of heparin, chondroitin sulfate and hyaluronic acid and its application in preparations and synovial fluid

A simple and accurate capillary electrophoresis (CE) method was developed to simultaneously separate and quantify heparin, chondroitin sulfate and hyaluronic acid. The relative standard deviations (intra-day) of migration time, peak height and peak area for heparin, chondroitin sulfate and hyaluronic acid were lower than 1.11, 5.45 and 2.82%, respectively. The limits of detection of heparin, chondroitin sulfate and hyaluronic acid were 0.91, 0.12 and 9.04 × 10(-3) mg/mL, respectively. The developed electrophoretic method was successfully applied to the analysis of commercial drug products and biological samples containing chondroitin sulfate and/or hyaluronic acid. The recoveries for chondroitin sulfate and hyaluronic acid were in the range of 95.9 ~107.0%. This was the first time the content of hyaluronic acid in the synovial fluids from osteoarthritic rabbits was investigated by CE. The results suggested that hyaluronic acid in the synovial fluids from osteoarthritic rabbits may be further metabolized and the administration of chondroitin sulfate or hyaluronic acid could affect the content and metabolism of hyaluronic acid in the synovial fluids. The developed CE method was simple to implement without sample pretreatment such as depolymerisation, very repeatable and easily transferred from lab to lab.