Formation and structures of Pd(II) N,S-heterocyclic carbene-pyridyl mixed-ligand complexes

Mononuclear mixed-ligand complexes of Pd(II) containing a N,S-heterocyclic carbene (NSHC) with a secondary alkyl N-substituent and pyridyl ligand, with the general formula [PdI₂(C₁₀H₁₁NS)L] (C₁₀H₁₁NS = 3-isopropylbenzothiazolin-2-ylidene; L = pyridine, 2-aminopyridine, 3-iodopyridine and 4-tert-butyl-pyridine) have been synthesized and characterized by X-ray single-crystal crystallography. Both solution and solid-state structures, as evident from their ¹H NMR spectra and X-ray structures, show anagostic γ-hydrogen interactions of metal with methine of the substituent on the carbene or pyridyl ligand giving 5-membered-chelate-like structures.     

Surface modification studies of edge-oriented molybdenum sulfide nanosheets

We have synthesized edge-oriented MoS2 nanosheets by the evaporation of a single source precursor based on Mo(IV)-tetrakis(diethylaminodithiocarbomato). The surface chemistry of the MoS2 nanosheets has been studied in order to evaluate the chemical reactivities of the basal planes and edges. By irradiating the MoS2 nanosheet with a scanning infrared laser, micron-scale lithographical structures can be created due to laser-induced oxidation of MoS2 to form nanocrystalline MoO3. Preferential reactivities of the MoS2 basal edges in an electrochemical environment and during vapor phase deposition have been demonstrated. Functionalization of the basal plane with 1-pyrene acetic acid allows the immobilization of DNA and immunoglobins on the MoS2 basal plane.     

Detection of acetaminophen using cyclic voltammetry on MnFe2O4/polyaniline

A novel sensing material, MnFe₂O₄/polyaniline (PANI), was fabricated by doping PANI to MnFe₂O₄ on a modified glassy carbon electrode (GCE). This sensing material was characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and high‐resolution transmission electron microscopy (HR‐TEM). Using a cyclic voltammetry electrochemical‐sensing method, we tested MnFe₂O₄/PANI, and an acetaminophen concentration of 0.0625–5 mM was recorded. Furthermore, the sensor responses were 2.05–22.44. The detection limit was 2.23 × 10^?7 M. Strong selectivity was observed for MnFe₂O₄/PANI, which is a possible sensing mechanism.     

A Highly Sensitive and Recyclable Ln‐MOF Luminescent Sensor for the Efficient Detection of Fe3+ and CrVI Anions

Two new three‐dimensional (3D) Ln^III metal‐organic frameworks (MOFs) were designed and successfully obtained via a solvothermal reaction between lanthanide(III) nitrates and a semi‐flexible carbazole tetracarboxylate acid linker as a high‐performance chromophore. 1 and 2 possess porous 3D networks with channels along the a axis, and more importantly, they show a highly sensitive and selective fluorescence quenching response to Fe³⁺ and Cr^VI anions. The sensing mechanism investigation revealed that the weak interactions of Fe³⁺ with nitrogen atoms of carbazole and deprotonated carboxylic acids protruding into the pores of MOFs quenched the luminescence of 1 and 2 effectively. In addition, the competition absorption also played an important role in the luminescence quenching detection of Fe³⁺ based on 1 , and Cr^VI anions based on 1 and 2 . Therefore, 1 and 2 represent an alternative example of regenerable luminescence based sensors for the quantitative detection of Fe³⁺ and Cr^VI anions.     

Biosynthesis of Streptolidine Involved Two Unexpected Intermediates Produced by a Dihydroxylase and a Cyclase through Unusual Mechanisms

Streptothricin‐F (STT‐F), one of the early‐discovered antibiotics, consists of three components, a β‐lysine homopolymer, an aminosugar D ‐gulosamine, and an unusual bicyclic streptolidine. The biosynthesis of streptolidine is a long‐lasting but unresolved puzzle. Herein, a combination of genetic/biochemical/structural approaches was used to unravel this problem. The STT gene cluster was first sequenced from a Streptomyces variant BCRC 12163, wherein two gene products OrfP and OrfR were characterized in vitro to be a dihydroxylase and a cyclase, respectively. Thirteen high‐resolution crystal structures for both enzymes in different reaction intermediate states were snapshotted to help elucidate their catalytic mechanisms. OrfP catalyzes an Fe^II‐dependent double hydroxylation reaction converting L ‐Arg into (3R,4R)‐(OH)₂‐L ‐Arg via (3S)‐OH‐L ‐Arg, while OrfR catalyzes an unusual PLP‐dependent elimination/addition reaction cyclizing (3R,4R)‐(OH)₂‐L ‐Arg to the six‐membered (4R)‐OH‐capreomycidine. The biosynthetic mystery finally comes to light as the latter product was incorporation into STT‐F by a feeding experiment.     

铂/L分子筛重整催化剂烷烃芳构化反应机理

铂/L分子筛新型重整催化剂具有碱性、单功能与独特的孔结构。与双功能催化剂对比,它对n-C_6～n-C_8直链烷烃有极高的芳构化活性和选择性,其芳构化机理可能与双功能催化剂不同。本文应用正己烷(n-C_8)、正庚烷(n-C_7)、正辛烷(n-C_8),2-甲基己烷(2MHx)、甲基环戊烷(MCP)等探针分子,在脉冲微反装置上考察了它们在Pt/BaL催化剂上的芳构化性能和产物分布。提出烷烃分子(≥C_6)主链的1,6位碳原子经与     

Polarographic Behavior of Bivalent Germanium in Alkaline Solution

Bivalent germanium was polarographically studied in sodium hydroxide solution at various concentrations. A well-defined reduction wave with half-wave potential varying from ?0.90 to ?0.98 volt vs. S.C.E. was observed for 1×10^?4 M Ge(II) in concentration range of 0.2 to 2.0 F with respect to NaOH, and from ?0.70 to ?0.88 volt vs. S.C.E. in the pH range 9.0–12.1 at 25°. The value of i_d/C is 5.43 μα/mM and that of i_d/C m^for t^1/8 is 5.21. Dependence of E_1/2 upon pH is expressed by —E_1/2 =0.18+0.058 pH. Experimental result suggests that the reaction proceeds in two-steps involving an irreversible two-electron reduction: Ge(OH)₂+OH^?→HGeO₂^?+H₂O and HGeO₂^?+H₂O+2e→Ge⁰+3OH^?.     

石墨烯和铂/石墨烯的合成及其表征

以天然鳞状石墨为原料,采用化学氧化法合成氧化石墨,在此基础上采用低温热解膨胀结合微波加热乙二醇还原法合成石墨烯(Gr)以及铂/石墨烯(Pt/Gr)复合材料。SEM和TEM显示所制备的石墨烯为层状结构的半透明薄膜。采用X射线光电子能谱(XPS)和傅立叶转换红外光谱(FTIR)分别确定氧化石墨、膨胀石墨及石墨烯表面含氧官能团的数量和性质。以所制备的碳氧原子比5.94的石墨烯作为载体制备出可用于质子交换膜燃料电池的高负载量的Pt/Gr催化剂,在铂载量高达60%时,表面铂粒子依然具有高分散性,平均粒径为3.8 nm。     

介入治疗用非血管可降解支架的研究进展

介入治疗是介于外科和内科治疗之间的新兴治疗方法,其中用于胆管、食管和气管等官腔的支架属于非血管介入治疗。非血管可降解支架与官腔具有良好的生物相容性,并且支架置入人体后,可以在一定时间内降解,转化为对人体无害的小分子排除体外。本文综述了介入治疗用非血管可降解支架的研究进展,重点介绍了非血管可降解支架的材料选择,外形设计,支架工艺(包括支架成型,覆膜改性,载药处理),性能测试(包括物理性能,力学性能,生物相容性,降解性能等)及临床应用进展。