Effects of amino acids on crystal growth of CaC2O4 in reverse microemulsion

Crystal growth of calcium oxalate (CaC2O4) in bulk aqueous solution, reverse microemulsion of p-octyl polyethylene glycol phenylether (OP)/iso-octyl alcohol (IOA)/cydohexane/water and above microemulsions containing different kinds of amino acids, such as aspartic acid (Asp), tyrosine (Tyr) and tryptophan (Trp) were studied. The results indicated that different crystallization types of the crystals, which were calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD) and calcium oxalate trihydrate (COT), existed in bulk aqueous solution. But CaC2O4 growth mainly paralleled with (1 01) plane of COM in reverse microemulsion because of the induction of surfactant at water/oil interface. After adding amino acids into microemulsions, the growth of CaC2O4 crystals mainly influenced by the varieties of amino acids and the pH values of the amino acid aqueous solution. When pH values of the solutions was higher than isoelectric points of amino acids, CaC2O4 crystal paralleled with (1 01) plane of COM more easily with the addition of Trp, Tyr, Asp in turn; however, when pH of the solutions was lower than isoelectric points of Trp, CaC2O4 crystal growth paralleled with (020) face of COM. It is obviously that amino acids, pH values of the solutions and surfactant played important roles in the process of crystal growth of CaC2O4 in the microemulsions. The formation mechanism of CaC2O4 was also discussed in different microemulsions at last.     

A novel biological strategy for morphology control of PbWO4 crystals in tomato extract

PbWO(4) crystals were readily synthesized by reacting lead oxide (PbO(2)) with sodium tungstate (Na(2)WO(4)·2H(2)O) at room temperature in the presence of tomato extract. Biomolecules such as vitamins, proteins in the extract played both the roles of reductant and template. The size and morphology of the PbWO(4) crystals could be controlled by adjusting the concentration of the reactants. When the concentration ratio of PbO(2) and Na(2)WO(4) was increased, the morphologies of the products varied from spherical to fusiform. Room-temperature fluorescence spectra indicated the products had a slight blue shift compared to the solid structure, which may be due to the structure defects in the crystals. The possible mechanism of PbWO(4) crystal growth in tomato extract was discussed.     

Sorption mechanisms of cadmium onto nano-hydroxyapatite: Comparative uptake studies and correlative solubility analysis

Hydroxyapatite (HAP) nanorod was synthesized by using ordered bicontinuous microemulsion, and was characterized by X-ray diffraction spectrum, scanning electron microscopy and high-resolution transmission electron microscopy. The solubility was investigated using ion chromatogram measurement, and was sensitively dependent on the value of pH. The capabilities to capture cadmium ions of HAP nanorods and micro-particles from aqueous salt solution were studied, and besides, X-ray diffractometry was used in order to characterize the mechanisms of cadmium uptake. As Cd²⁺ adsorption occurred, it has undergone the coprecipitation of Cd₂P₂O₇ crystal to give multiple solids composed of HAP and Cd₂P₂O₇ crystallites, which affected the dissolution of hydroxyapatite. During Cd²⁺ sorption process, solubility variations of the sediments showed a more complex pattern than previously reported. Contribution of surface mechanisms, in association with precipitation of cadmium phosphate phases, could explain this behavior.     

A novel method to realize the transition from silver nanowires to nanoplates based on the degradation of DNA

Journal of Nanoparticle Research - Silver “nano-necklaces” and nanoplates in DNA/Tris–EDTA (TE) solution are prepared using hydrothermal method. The nano-necklaces are composed of...     

New Lamé function and its application to nonlinear equations

In this Letter, a new kind of Lamé functions are given. Based on the new Lamé functions and Jacobi elliptic function, the perturbation method is applied to the nonlinear equations, and many multi-order solutions of novel forms are derived. In addition, it is shown that different Lamé functions can exist in the first order solutions of nonlinear system.     

Periodic structures of oceanic Rossby wave under the influence of wind stress

A simple oceanic barotropic potential vorticity equation on β-plane with the influence of wind stress is applied to investigate the nonlinear Rossby wave in a shear flow. By the reductive perturbation method, we derived the rotational modified KdV (rmKdV for short) equation. And then with the help of Jacobi elliptic functions, we obtain various periodic structures for these equatorial Rossby waves. It is shown that the wind stress is very important for these periodic structures of rational form.     

三级环氧醇与PCC的非对映性氧化反应研究

报道一类新颖的氯铬酸吡啶盐(PCC)与三级环氧醇的非对映选择性氧化反应,就反应的立体选择性、化学选择性和可能的反应机理进行了讨论。该反应不仅可用于制备手性的三级环氧醇,同时还可以用于合成含有手性季碳中心的1,3-二酮。     

Growth of calcium oxalate crystals induced by complex films containing biomolecules

Nucleation and growth of calcium oxalate (CaC₂O₄) crystals induced by films composed of phosphatidylcholine (PC), cholesterol (CS) and human serum albumin (HSA), and of PC, CS and dextran have been carried out. The products obtained were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and ultraviolet‐visible spectroscopy. The results indicate that hexagonal calcium oxalate monohydrate (COM) and club‐shaped calcium oxalate trihydrate (COT) crystals are obtained on the PC/CH/HSA film, and the microstructure and properties of the PC/CH/HSA film depend on the weight ratio of PC to CS. With an increase in the PC‐to‐CS ratio, the number of COM crystals decreases gradually, and finally disappear, suggesting that PC inhibits the growth of COM crystals. On the PC/CS/dextran film, irregular COM and COT crystals are formed. The possible formation mechanisms of CaC₂O₄ on the two complex films are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Removal of heavy metal ions by biogenic hydroxyapatite: Morphology influence and mechanism study

Based on the synthesis of hydroxyapatite (HA) with different morphologies, such as nanorod-like, flower-like and sphere-like assembled HA nanorods, a new strategy has been developed for the removal of heavy metal ions such as Pb²⁺, Cu²⁺, Mn²⁺, Zn²⁺. The dependence of removal efficiency on the morphology and the suspended concentration of trapping agent, the removal time and selectivity were evaluated and discussed. The experimental results proved that the removal capacity of flower-like assembled HA nanorods (NAFL-HA) was the best, and the maximum removal ratio for Pb²⁺ ion was 99.97%. The mechanism of Pb²⁺ removal was studied in detail, noting that some metal ions were completely incorporated into hydroxyapatitie to produce Pb-HA. It reveals that the metal ions capture by HA is mainly controlled by sample surface adsorption and co-precipitation, which are directly controlled by sample morphology.