CO加氢合成C2含氧化合物Rh-Sm/SiO2催化剂的研究

使用加压下的CO加氢反应、程序升温还原(TPR)、吸附氢的程序升温脱附(H2-TPD)以及CO和H2吸附等技术,研究了Rh-Sm/SiO2催化剂上Sm促进剂对合成二碳含氧化合物的促进效应.结果表明,Sm加入到Rh/SiO2中使催化剂的活性和二碳含氧化合物的选择性显著提高,催化剂上的Sm3+不易被还原,Sm的加入起着提高Rh分散度的作用,使催化剂上CO和H2的吸附量增大,倾向于促进乙酸和乙醛的生成.     

绿色催化二氧化碳、炔丙醇和亲核试剂的三组分反应

近些年来,将CO₂转化为高附加值化学品受到广泛关注。其中,CO₂、炔丙醇和亲核试剂的三组分反应可用于制备用途广泛的羰基化合物,该方法具有步骤经济性、原子经济性等优点。由于CO₂分子具有热力学稳定性和动力学惰性,多数CO₂参与的化学反应在热力学上不支持。然而,CO₂、炔丙醇和双亲核试剂三组分反应是热力学有利的CO₂转化反应,实现了邻二醇或氨基醇和CO₂到环状碳酸酯以及2-噁唑啉酮的高效转化。本综述旨在于总结并讨论近年来CO₂、炔丙醇和亲核试剂三组分反应制备多种羰基化学物的主要进展。     

Alloying n‐Butylamine into CsPbBr3 To Give a Two‐Dimensional Bilayered Perovskite Ferroelectric Material

Cesium‐lead halide perovskites (e.g. CsPbBr₃) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr₃, we design the first cesium‐based two‐dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C₄H₉NH₃)₂CsPb₂Br₇ ( 1 ). Strikingly, 1 shows a high Curie temperature (T_c=412 K) above that of BaTiO₃ (ca. 393 K) and notable spontaneous polarization (ca. 4.2 μC cm^?2), triggered by not only the ordering of organic cations but also atomic displacement of inorganic Cs⁺ ions. To our knowledge, such a 2D bilayered Cs⁺‐based metal–halide perovskite ferroelectric material with inorganic and organic cations is unprecedented. 1 also shows photoelectric semiconducting behavior with large “on/off” ratios of photoconductivity (>10³).     

高效液相色谱荧光衍生法检测醇和酸的进展

高效液相色谱荧光衍生化醇和酸能提高检测灵敏度,改善分离效果,综述了最近十多年来高效液相色谱荧光衍生法检测醇和酸的进展情况。列出了衍生化试剂的结构,评述了衍生化的反应条件。指出了今后的发展方向。     

高效毛细管电泳对农药手性拆分的进展

环境中使用的农药绝大多数都具有位置或光学异构体,而且同一农药的不同对映体通常也具有不同的药效和毒性,但是目前有关手性农药的研究还很少,高效毛细管电泳是一门特别适于手性分离研究的技术,综述了近年来利用高效毛细管电泳技术对手性农药进行拆分的研究,最后对该工作的发展前景进行了讨论。     

Removal of Cr (VI) from aqueous solution using magnetic biochar synthesized by a single step method

Magnetic biochar, as an adsorbent, was synthesized by a single step method, where iron salt was directly mixed with pinewood sawdust by chemical co-precipitation and subsequently pyrolyzed at 700°C for Cr (VI) removal from aqueous solution. The effects of some important parameters including adsorbent dosage (0.4–2.8?g/L), pH (1–10) of the solution, contact time (0–1440 minutes), initial concentration (30–120?mg/L), and temperature (20–40°C) were investigated in batch experiments. Both pre- and post-adsorbents were characterized by SEM-EDX and XPS to investigate the adsorption mechanism. The maximum adsorption capacity of the tested magnetic biochar under the certain experimental conditions determined as optimal was 42.7?mg/g for Cr (VI). The adsorption data were proved to be suitable for the pseudo-second order model for kinetics and the Langmuir model for isotherms with correlation R²?=?0.9996 andR²?>?0.9980, respectively, after fitting with four kinetic models (pseudo-first order, pseudo-second order, W-M model, and Elovich) and three isotherm models (Langmuir, Freundlich, and Temkin). The characteristic analyses further verified that the efficient particle was a mixture of iron oxides in essence, and it had a strong effect on the spontaneous and endothermic adsorption process.     

Influence of Linkage Stereochemistry and Protecting Groups on Glycosidic Bond Stability of Sodium Cationized Glycosyl Phosphates

Energy-resolved collision-induced dissociation (ER-CID) experiments of sodium cationized glycosyl phosphate complexes, [GP _x +Na]⁺, are performed to elucidate the effects of linkage stereochemistry (α versus β), the geometry of the leaving groups (1,2-cis versus 1,2-trans), and protecting groups (cyclic versus non-cyclic) on the stability of the glycosyl phosphate linkage via survival yield analyses. A four parameter logistic dynamic fitting model is used to determine CID_50% values, which correspond to the level of rf excitation required to produce 50% dissociation of the precursor ion complexes. Present results suggest that dissociation of 1,2-trans [GP _x +Na]⁺ occurs via a McLafferty-type rearrangement that is facilitated by a syn orientation of the leaving groups, whereas dissociation of 1,2-cis [GP_x+Na]⁺ is more energetic as it involves the formation of an oxocarbenium ion intermediate. Thus, the C1?C2 configuration plays a major role in determining the stability/reactivity of glycosyl phosphate stereoisomers. For 1,2-cis anomers, the cyclic protecting groups at the C4 and C6 positions stabilize the glycosidic bond, whereas for 1,2-trans anomers, the cyclic protecting groups at the C4 and C6 positions tend to activate the glycosidic bond. The C3 O-benzyl (3 BnO) substituent is key to determining whether the sugar or phosphate moiety retains the sodium cation upon CID. For 1,2-cis anomers, the 3 BnO substituent weakens the glycosidic bond, whereas for 1,2-trans anomers, the 3 BnO substituent stabilizes the glycosidic bond. The C2 O-benzyl substituent does not significantly impact the glycosidic bond stability regardless of its orientation.

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Graphical abstract ?

     

An isothermal strand displacement amplification strategy for nucleic acids using junction forming probes and colorimetric detection

The authors describe a method for DNA target recognition and signal amplification that is based on the target-induced formation of a three way junction. The subsequent assembly of two DNA probes releases the inhibitory strand and triggers a downstream strand displacement amplification. This causes the formation of a G-rich single sequence that binds to a hemin monomer with its peroxidase-mimicking properties. The resulting peroxidase (POx) activity is quantified by using H₂O₂ and TMB as the substrate. In the presence of an inhibitor, in contrast, the POx-like activity is strongly reduced. This forms the basis for a highly sensitive DNA assay. It has a 0.8 pM detection limit when operated at a wavelength of 450 nm and was applied to the isothermal determination of target DNA with high selectivity.

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Graphical abstract Schematic of the assay: Introduction of target results in the formation of a three way junction. The subsequent assembly of two probes releases the inhibitory strand and triggers a downstream strand displacement amplification, generating amount of G-rich single sequence which causes peroxidase-mimicking activity on binding to a hemin monomer.

     

Decompositions of functions and Dirichlet problems in the unit disc

In this paper, we establish a decomposition theorem for polyharmonic functions and consider its applications to some Dirichlet problems in the unit disc. By the decomposition, we get the unique solution of the Dirichlet problem for polyharmonic functions (PHD problem) and give a unified expression for a class of kernel functions associated with the solution in the case of the unit disc introduced by Begehr, Du and Wang. In addition, we also discuss some quasi-Dirichlet problems for homogeneous mixed-partial differential equations of higher order. It is worthy to note that the decomposition theorem in the present paper is a natural extension of the Goursat decomposition theorem for biharmonic functions.     

Holomorphic map with unipotent jacobian matrices in C 3

We prove that the holomorphic unipotent Jacobian conjecture is valid when n = 3.