Control of calcium carbonate polymorphism and morphology through biomimetic mineralization by means of nanotechnology

In vitro biomimetic mineralization by means of nanotechnology allows the formation of calcium carbonate polymorphs at low temperatures (<25 degrees C) under a CO(2) atmosphere of 500-1500 ppm. A two-dimensional zinc-ion ordered array (zinc array), which acts as an active-site mimic of carbonic anhydrase, has been prepared by immersing the self-organized monolayer of 3-(2-imidazolin-1-y)propyltriethosilane on mica (ImSi substrate) into aqueous zinc solution. The zinc array mounted on the ImSi substrate catalyzed the conversion from CO(2) to HCO(3) (-), and accelerated the formation of calcium carbonate. In situ X-ray diffraction data of the formed calcium carbonate on the poly(L-aspartate)-coated chitin substrate (pAsp substrate), with calcium ion-recognition sites, demonstrated that the interaction between the zinc array and pAsp substrates formed both vaterite and calcite at low temperature (15 degrees C) and mainly vaterite at 25 degrees C; this interaction also controlled the morphology of calcium carbonate formed on pAsp substrate.     

Stereoselective formation of ansa-metallocenes in reactions of radical-anionic salts of acenaphthylene with lanthanide and calcium halides

ansa-Metallocenes (⁵:⁵-C₂₄H₁₆)M(THF)₂ (M = Sm (1), Yb (2), Ca (3)) and (⁵:⁵-C₂₄H₁₆)MI(THF) (M = Dy (8), Er (9), Tm (10), Lu (11)) were prepared in 50—90% yields by the in situ reactions of two equivalents of potassium acenaphthylenide K⁺C₁₂H₈ ^– with MI₂ or MI₃, respectively. Complexes 2 and 3 were also obtained by direct reduction of acenaphthylene with ytterbium and calcium naphthalenides, respectively. An ESR signal of the acenaphthylene radical anion, which was observed upon dissolution of compound 2 in THF, indicates that the [C₂₄H₁₆]^2– ansa-ligand dissociated into two [C₁₂H₈]^·– radical anions. Hydrolysis of complex 2 in benzene afforded 1,1",3,3"-tetrahydro-3,3"-biacenaphthylene (4) and 3,3",4,4"-tetrahydro-3,3"-biacenaphthylene (5). The reaction of complex 2 with ZrCl₄ and the reaction of compound 3 with Me₃SiCl proceeded with the cleavage of the C—C bond between two acenaphthylene fragments of the [C₂₄H₁₆]^2– ansa-ligand to produce (²-C₁₂H₈)ZrCl₂(THF)₃ (6) and bis(trimethylsilyl)acenaphthene (Me₃Si)₂C₁₂H₈ (7), respectively. Compounds 1—3, 6, 7, and 11 were characterized by ¹H and ¹³C NMR spectroscopy. The temperature dependence of the ¹H NMR spectrum of compound 11 in tetrahydrofuran is indicative of the dynamic exchange of the solvent molecules in the coordination sphere of the Lu atom. After cooling of the solution to 210 K, the dynamic process was terminated as evidenced by the nonequivalence of the ¹H signals of two acenaphthylene fragments. According to the X-ray diffraction data for complex 11, dimerization of two acenaphthylene radical anions at the Lu atom gave rise to the rac-ansa-metallocene structure. In compound 11, the Lu atom is ⁵-coordinated by two five-membered rings of the acenaphthylene ligands and also by the I atom and the THF molecule. The coordination environment about the Lu atom is a distorted tetrahedron. The average distance between the lutetium atom and the carbon atoms of the five-membered rings is 2.623 .     

冰点下降法测定正十六烷中TBP的活度系数

磷酸三正丁酯(TBP)是核燃料及多种稀有金属水冶过程中使用的重要萃取剂,Healy 等人用蒸气压法、Alcock 用溶解度法先后测定过它在一些溶剂中的活度系数,不同作者的数据分歧很大,测定的浓度范围一般也较小.高宏成等人用磷-32标记TBP 分配法在较大浓度范围内测定过TBP 在氯仿、四氯化碳、苯、正已烷等8～9种溶剂中的活度系数,     

Microgel-based engineered nanostructures and their applicability with template-directed layer-by-layer polyelectrolyte assembly in protein encapsulation

A novel strategy for the fabrication of microcapsules is elaborated by employing biomacromolecules and a dissolvable template. Calcium carbonate (CaCO(3)) microparticles were used as sacrificial templates for the two-step deposition of polyelectrolyte coatings by surface controlled precipitation (SCP) followed by the layer-by-layer (LbL) adsorption technique to form capsule shells. When sodium alginate was used for inner shell assembly, template decomposition with an acid resulted in simultaneous formation of microgel-like structures due to calcium ion-induced gelation. An extraction of the calcium after further LbL treatment resulted in microcapsules filled with the biopolymer. The hollow as well as the polymer-filled polyelectrolyte capsules were characterized using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and scanning force microscopy (SFM). The results demonstrated multiple functionalities of the CaCO(3) core - as supporting template, porous core for increased polymer accommodation/immobilization, and as a source of shell-hardening material. The LbL treatment of the core-inner shell assembly resulted in further surface stabilization of the capsule wall and supplementation of a nanostructured diffusion barrier for encapsulated material. The polymer forming the inner shell governs the chemistry of the capsule interior and could be engineered to obtain a matrix for protein/drug encapsulation or immobilization. The outer shell could be used to precisely tune the properties of the capsule wall and exterior. [Diagram: see text] Confocal laser scanning microscopy (CLSM) image of microcapsules (insert is after treating with rhodamine 6G to stain the capsule wall).     

Possible Mechanisms of Intercalation

Recent knowledge of the kinetics and intercalation mechanisms are summarized and accompanied by examples of intercalation reactions of water and ethanol into anhydrous vanadyl phosphate and redox intercalation of alkali metal cations into vanadyl phosphate dihydrate. Three possible mechanisms of intercalation are presented which are based on: (i) a concept of exfoliation of layers; (ii) the formation of stages and randomly stacked layers; (iii) co-existence of intercalated and non-intercalated parts of crystals of the host separated by an advancing phase boundary. The corresponding kinetic curves are ascribed to mechanisms (ii) and (iii).     

Mercury extraction by ionic liquids: temperature and alkyl chain length effect

The preliminary results described here show the complete transfer of Hg(II) ions, in the absence of a chelating agent in 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids; the lag time required to gain the quantitative metal ion partition turned out to be strongly dependent both on alkyl chain length on the imidazolium ring and on the working temperature.     

关于冷原子吸收法测定尿汞影响因素探讨

介绍了对尿汞快速测定法的改进，用消泡剂磷三丁酸消除尿中泡沫，并讨论了尿汞测定的最佳条件，本法的相对标准偏差为４．８－９．０％，回收率９４－１０１％。     

Preparation and Crystal Structure of Potassium Iron Hydrogen Phosphate,KFe3(HPO4)2(H2PO4)6 · 4 H2O

Single crystals of potassium iron hydrogen phosphate, KFe₃(HPO₄)₂(H₂PO₄)₆ · 4 H₂O, were prepared hydrothermally by heating a mixture of Fe₂O₃, H₃PO₄ and K₂CO₃ with a small amount of water. It crystallizes monoclinic, space group C2/c (N° 15 Int. Tab.) with Z = 4 and a = 1701(2), b = 960.4(5), c = 1750(1) pm, β = 90.88(7)°. The crystal structure was solved by using 1716 unique reflections F₀ > 4σ(F₀) with a final wR2 value of 0.126 (SHELXL-93). The main feature of the crystal structure are layers formed by PO₄-tetrahedra around the FeO₆-octahedra parallel to (001). K⁺ and H₂O molecules connect these layers. Effective Coordination Numbers (ECoN), Mean Fictive Ionic Radii (MEFIR), Charge Distribution (CHARDI) and the Madelung Part of Lattice Energy (MAPLE) are calculated for the title compound. The existence of hydrogen bonds is confirmed by these calculations.     

离子液体两相不对称氢甲酰化催化反应的研究

从(R)-BINAP出发制备水溶性磺酸钠盐配体(R)-BINAPS,采用离子液体BF4和PF6为介质,实现其Rh配合物对乙酸乙烯酯的两相不对称氢甲酰化反应.实验结果表明,在以BF4为介质的乙酸乙烯酯不对称氢甲酰化反应中,该催化剂在温和条件下显示出高于相应均相体系的产物ee值和异构醛选择性,并在6次循环使用中,反应产物的ee值、选择性和转化率均无明显改变;在离子液体体系中添加适当的甲苯时,油溶性配体(R)-BINAP与Rh组成的配合物催化剂亦可形成类似的两相反应体系,但其活性和选择性在重复使用中呈明显下降趋势.本文还考察了溶剂体系、膦铑比、温度、压力、时间等的影响,并尝试苯乙烯的两相不对称氢甲酰化反应.     

Crystal structure of sodium potassium zinc diphosphate NaKZnP2O7

Single crystals of NaKZnP₂O₇ were grown, and their crystal structure was determined by X-ray diffraction (space group P2₁/n, a = 12.585(5) Å, b = 7.277(5) Å, c = 7.428(5) Å, β = 90.00(5)°, Z = 4, 1916 F(hkl), R ₁ = 0.0461). The structure contains a 3D tetrahedral zinc phosphate framework with a system of intersecting channels running along the b and c axes. The sodium and potassium atoms are coordinated to six and seven oxygen atoms, respectively, and reside inside these channels; the potassium cations, which are larger than the sodium cations, are located at channel intersections.