Table of Content

24 December 2001, Volume 17 Issue 4

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Articles

Hydrothermal Synthesis and Structure of [{Mo₈V₄O₃₆(VO₄)(VO)₂}_n]^7n- Bi-capped α-Keggin Fragments Linked to a Chain

LUAN Guo-you, HAN Zheng-bo, WANG En-bo, LU Ying, LI Yang-guang, HU Chang-wen, HU Ning-hai, JIA Heng-qing

2001, 17(4):  347-351. 

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The title compound, (H₂en)₃H₃O {Mo₈V₄O₃₆ (VO₄) (VO)₂}·4H₂O, was hydrothermally synthesized and structurally characterized by means of IR, ESR spectrum and single crystal X-ray diffraction.It crystallized in a monoclinic system with space group P2₁/c, a= 1.980 4(4)nm, b＝2.063 4(4) nm, c=1.192 0(2) nm, β=94.76(3)°and deep black colour.The compound contains V-centered bi-capped a-Keggin fragments {Mo₈V₇O₄₂} that are linked together by edge-shared units V^ⅣO₅ via V-O-V bonds, forming a chain.

Studies on Insoluble Species of Gd(Ⅲ) in Human Blood Plasma by Computer Simulation

WANG Yue, LU Xing, ZHANG Hai-yuan, YANG Kui-yue, NIU Chun-ji, NI Jia-zuan

2001, 17(4):  352-355. 

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The insoluble species of Gd (Ⅲ) in human blood plasma were investigated by computer simulation.The distribution of the Gd (Ⅲ) species was obtained.It was found that most of the Gd (Ⅲ) ions were bound to phosphate to form precipitate GdPO₄ at the concentration of 1.000 ×10^-7 mol/L and when the concentration of the Gd (Ⅲ) increased to 3.750 × 10^-4 mol/L, in excess of the concentration of phosphate, the Gd (Ⅲ) ions were bound to carbonate to form another kind of precipitate, Gd₂(CO₃)₃.

Synthesis, Structure Characterization and Biological Activity of a Novel Amino Acid Salt (Hala)₈(H₃O)₁₀[Pmo₁₂O₄₀]₆·22H₂O

HAN Zheng-bo, WANG En-bo, LUAN Guo-you, HU Chang-wen, CHANG Ya-ping, LI Juan, HU Ning-hai, JIA Heng-qing

2001, 17(4):  356-361. 

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A novel compound was synthesized and characterized by means of elemental analysis, IR and UV spectra, TG, CV and single crystal X-ray diffraction.The compound crystallized in an orthorhombic space group C222 with a=1.622 4(3) nm, b＝3.498 4(7) nm, c=1.301 5(3)nm, V=7.387(3) nm³, Z=6, R_{1=0.037 3, wR2=0.114 0.The Ala(Ala=alanine) molecules were protonated at the amino nitrogen N (1) and the C (2) of Ala group with the terminal oxygen atom O(15), O(14), O(26) and O(27) of the polyoxometalates participating in the hydrogen bond network.The anti-tumor activity of the title compound was estimated against Hela and Pc-3m cancer cells.}

Studies on the Electrochemical Behavior of Bleomycin at a Co/GC Ion Implantation Modified Electrode and Its Application

HU Jing-bo, LI Qi-long

2001, 17(4):  362-367. 

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In a 0.10 mol/L Hac-NaAc buffer solution(pH= 4.59), a sensitive reduction peak of bleomycin was observed by linear sweep voltammetry at a Co/GC ion implantation modified electrode.The peak potential was -0.73 V(vs.SCE).The peak current was proportional to the concentration of bleomycin over the range of 5.0 × 10^-8-1.0 × 10^-6 and 1.0 × 10^-6-1.0 × 10^-5mol/L with a detection limit of 2.0 × 10^-8 mol/L.The electrochemical behavior of the reduction peak of bleomycin at the Co/GC modified electrode was studied by linear sweep and cyclic voltammetry and applied to the determination of bleomycin in urine.This method is simple,rapid and reliable.The reduction process is quasi-reversible.The experiments of AES and XPS showed that Co was surely implanted into the surface of GCE and the depth distribution of Co was ingood agreement with Gooses normal distribution; the implanted Co at GCE improved the electrocatalytic activity.

Studies on the Basic Conformation of Lysozyme by Electrospray Ionization-Mass Spectrometry (ESI- MS)

GU Sheng, SHEN Jin-can, ZHUANG Zhi-xia, WANG Xiao-ru

2001, 17(4):  368-373. 

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In the present work, 2-mercaptoethanol and dithiothreitol were used to hydrogenise the internal disulfide bond in lysozyme.The experimental results indicate that the charge distribution of the proteins are different in the reaction process.From the calculated molecular weight, the reduction process of the disulfide bond in the molecules can be described, and the number of the disulfide bonds in the molecule can also be determined.

Luminescence Quenching Behavior of Oxygen Sensing ORMOSIL Films Based on Ruthenium Complex

JIANG Ya-qi, LI Zhen, ZHONG Zhen-ming, CHEN Xi, WANG Xiao-ru, WONG Kwok-yin

2001, 17(4):  374-379. 

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An organically modified silicate (ORMOSIL) based optical sensor response to gaseous O₂ or O₂ dissolved in water is presented.The oxygen sensing film mechanism is based on the principle of fluorescence quenching of tris(4,7-diphenyl-1,10-phenanthroline) ruthenium (Ⅱ)([Ru(dpp)₃]²⁺), which has been entrapped in a porous ORMOSIL film.In order to establish optimum film-processing parameters, comprehensive investigations, including the effects of the polarity and the hydrophobicity of the sensing film on oxygen quenching response and response time, were carried out.The film hydrophobicity increased as a function of dimethyldimethoxysilane (DiMe-DMOS) content, which is correlated with enhanced oxygen sensor performance.The sensor developed in the present work exhibits the advantages of fast response time and good reversibility.The detection limits are 0.50% and 0.3μg/Ml for O₂ in the gaseous and the aqueous phases, respectively.

Electronic Noses Using Quantitative Artificial Neural Networ

WEN Li-jing, BIAN Li-ping, LU Yu, ZHANG Mei-zhuo, YU Li-ping, YANG Peng-yuan

2001, 17(4):  380-386. 

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The present paper covers a new type of electronic nose(e-nose) with a four-sensor array,which has been applied to detecting gases quantitatively in the presence of interference.This e-nose has adapted fundamental aspects of relative error(RE) in changing quantitative analysis into the artificial neural network (ANN)..Thus, both the quantitative and the qualitative requirements for ANN in implementing e-nose can be satisfied.In addition, the e-nose uses only 4 sensors in the sensor array, and can be designed for different usages simply by changing one or two sensor(s).Various gases were tested by this kind of e-nose, including alcohol vapor, CO, liquefied-petrol-gas and CO₂.Satisfactory quantitative results were obtained and no qualitative mistake in prediction was observed for the samples being mixed with interference gases.

Time-resolved ESI-MS Investigation on Reduction and Alkylation in Unfolding Process of Lysozyme

SONG Hao-wei, XU Chong-feng, FU Yun-lin, YANG Peng-yuan, WANG Hong-hai

2001, 17(4):  387-393. 

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The kinetic procedure of the unfolding of lysozyme induced by the reduction of disulfide was monitored by the time-resolved ESI-MS with a sheath liquid assistant electrospray interface.It was found that the reduction process for the eight disulfides had a less difference in the reaction time after denatured treatment.In addition, the alkylation of the reduced free thiols was much slower than the reduction procedure.An artifact peak produced by the CID fragmentation in the mass spectra was identified and the possible mechanism of the Hofmann elimination reaction was proposed.

A Study of the Electrochemistry of Two Biacridine Derivatives and Their Application

XU Xue-qin, ZHUANG Hui-sheng, CHEN Guo-nan

2001, 17(4):  394-399. 

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The electrochemical behavior of two new synthesized biacridine derivatives, 3,3'-disulfonyl9,9'-biacridine dinitrate ( DSBADN) and 10,10'-dimethyl-3,3'-disulfonyl-9,9'-biacridine (DMDSBA) was investigated by means of cyclic voltammetry and linear sweep polarography.In a HC1 solution, the reduction peak current was proportional to the concentrations of DSBADN and DMDSBA.The electrochemical study demonstrated that the reduction peak currents of DSBADN and DMDSBA exhibited adsorptive and diffusion-controlled characteristics, and the electrode reaction was totally irreversible.Tryptophan(Trp) and Histidine(His) could inhibit the reduction peak currents of DSBADN and DMDSBA respectively, the extent of the inhibition was proportional to the concentrations of Trp and His.Based on this principle, a new electrochemical system has been developed for determination of Trp and His.

A Novel Sample Introduction Technique for the Simultaneous Determination of As, Se, Ge and Hg in Chinese Medicinal Material

CHEN Bin, ZHUANG Zhi-xia, WANG Xiao-ru, Frank S. C. Lee

2001, 17(4):  400-406. 

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A novel technique of Moveable Reduction Bed Hydride Generator(MRBHG) was applied to the hydride generation or cold vapor generation of As, Se, Ge, and Hg existing in Traditional Chinese Medicinal Material(TCM).The simultaneous determination of the multi-elements was performed with ICP-MS.A solid reduction system involving the use of potassium tetraborohydride and tartaric acid was applied to generating metal hydride or cold vapor efficiently.The factors affecting the metal cold vapor generation were studied.The main advantage of the technique is that only a 4 μL volume of sample was required for the cold vapor generation.The absolute detection limits of all the elements studied are in 10^-12 g level.

Synthesis of 5-Substituted-3-[(2'R,4'R)-4'-Hydroxy-2'-hydroxymethyl tetrahydrofuran-4'-yl]-1,2,4-oxadiazoles and Their Epimers

WU Wei-dong, MA Ling-tai, ZHANG Li-he

2001, 17(4):  407-414. 

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The syntheses of 5-substituted-3-[(2' R' 4' R)-4v -hydroxy-2'-hydroxymethyltetrahydrofuran-4'-yl]-1, 2,4-oxadiazoles and their epimers were accomplished with the aid of the construction of 1, 2, 4-oxadiazoles by condensation of O-acylated cyanohydrins with hydroxylamine via intramolecular transacylation and subsequent cyclization.

A Practical Synthesis of 3-Oximido-substituted-1,5-diazacycloheptane Dihydrochloride

HAN Jie, ZHI Yong-gang, ZHANG Liang-fu, ZHANG Rui, YAN Yaw Kai

2001, 17(4):  415-419. 

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From 3-hydroxyl-1, 5-diazacycloheptane dihydrobromide, we have synthesized a series of new compounds, 3-oximido-substituted-1,5-diazacycloheptane dihydrochloride, in high yields.The experimental operations are convenient and mild.

Stabilization of Cu/ZnO Based Catalysts by Nickel Additive in Methanol Decomposition

Xl Jing-yu, WANG Zhi-fei, LU Gong-xuan

2001, 17(4):  420-425. 

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A series of Cu/Zn based catalysts with and without Ni, prepared by the co-precipitation method, has been studied for methanol decomposition.CO and H₂ are the major products.The Cu/Zn catalysts show a low initial activity and a poor stability.The formation of the CuZn alloys was observed in the deactivated Cu/Zn catalysts which were used for methanol decomposition at 250 ℃.When small amounts of Ni were added in the catalyst, the Cu/Zn/Ni(molar ratio 5/4/x) catalysts showed a high activity at a low temperature.The activity and the stability of the catalyst depend on the nickel content.The activity of the Cu/Zn/Ni catalysts was maintained at a relatively stable value of 78% conversion of methanol with 95% selectivity of H₂, 93%selectivity of CO, and a more than 70% yield of hydrogen was obtained at 250 ℃ when x≥1.The stability of the Cu/Zn/Ni(molar ratio 5/4/x) catalysts showed the maximum(ca 88%)when x＝1.The stabilization effect of nickel on the Cu/Zn based catalysts may lead to the increasing of the dispersion of active Cu species and the prevention of CuZn alloys formation.

Preparation and Properties of Zirconium Hydride on the Surface of MCM-41 Mesoporous Molecular Sieves

WANG Xu-xu, FU Xian-zhi, LEFEBVRE Frédéric, BASSET Jean-Marie

2001, 17(4):  426-431. 

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Zirconium monohydride bonded to the framework oxygen of MCM-41 surface was prepared by the reaction of tetraneopentyl zirconium with MCM-41 surface hydroxyl groups, followed by the hydrogenolysis of the resulted product.The surface hydride was characterized by using infrared spectroscopy, solid-state NMR, elemental analysis, gas-phase chromatography and chemical probing reaction.It was shown that this surface species is stable below 150 ℃ and can catalytically crack alkanes into methane and ethane at 100 ℃.

A Thermodynamic Model for Square-well Chain Fluid: Theory and Monte Carlo Simulation

ZHANG Bing-jian, LU Ying-hong, HU Wen-xuan, JIN Zhi-jun

2001, 17(4):  432-438. 

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A thermodynamic model for the freely jointed square-well chain fluids was developed based on the thermodynamic perturbation theory of Barker-Henderson, Zhang and Wertheim.In this derivation Zhang's expressions for square-well monomers improved from Barker-Henderson compressibility approximation were adopted as the reference fluid, and Wertheim's polymerization method was used to obtain the free energy term due to the bond connectivity.An analytic expression for the Helmholtz free energy of the square-well chain fluids was obtained.The expression without adjustable parameters leads to the thermodynamic consistent predictions of the compressibility factors, residual internal energy and constant-volume heat capacity for dimer,4-mer, 8-mer and 16-mer square-well fluids.The results are in good agreement with the Monte Carlo simulation.To obtain the MC data of residual internal energy and the constant-volume heat capacity needed, NVT MC simulations were performed for these square-well chain fluids.

Effects of the Specific Area and the Thermal Stability of a Polymer on the Catalytic Activities of Polymer Immobilized Co-Pd Catalysts by SAMI

WU Shi-hua, WEI Wei, ZHU Chang-ying, HUANG wei-ping, ZHANG Shou-min, ZHENG Xiu-cheng, ZHANG Shu-hong, ZHAO Wei-jun

2001, 17(4):  439-444. 

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Co-Pd bimetallic catalysts immobilized with four kinds of resins with different specific areas were prepared by means of the solvated metal atom impregnation (SMAI) method.The results of the XRD and the magnetic measurement showed that as the specific area of the resin increased,the particle sizes of Co and Pd on the catalysts with the same metal content decreased, so the catalytic activity of the catalysts for the hydrogenation of diacetone alcohol as well as the reduction of oxygen on the fuel cell electrode increased.Below 140 ℃, the conversion of diacetone alcohol increased as the reaction temperature increased, and above 140 ℃, the conversion decreased because of the rupture of the resin.

Propylene Polymerization Catalyzed by Bis (R3-indenyl) Zirconium Dichloride/Aluminoxane--Synthesis of Metallocenes and Influence of Sol vent Polarity on Poi ymerization

YASIN Tariq, FAN Zhi-qiang, ZHU Yin-bang, FENG Lin-xian

2001, 17(4):  445-451. 

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Three unbridged metallocenes, bis(2,4,7-Mea-indenyl)zirconium dichloride (1), bis (2-Me4,7-Etz-indenyl) zirconium dichloride (2) and bis (2,4,6-Me3-indenyl) zirconium dichloride (3)were synthesized.The effect of solvent polarity on propylene polymerization catalyzed by the metallocenes in the presence of methylaluminoxane(MAO) and triisobutylaluminum(TIBA) was investigated in the toluene/CH₂Cl₂ mixed solvent.Changing the solvent polarity was found to influence the catalytic activity, polymer molecular weight and stereospecificity of the catalysts.The changes in the position of the substituents on the ligand caused the different responses of the catalyst to the changes in solvent polarity.The isotactic stereosequence of polypropylene was found to increase with the increase in the polarity of the reaction medium.

Polymorphic Behavior of Syndiotactic Polypropylene Induced by Heat Treatment

DOU Hong-jing, HE Su-qin, ZHUCheng-shen, WANG Liu-yang

2001, 17(4):  452-456. 

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The polymorphic behavior of syndiotactic polypropylene (s-PP) crystallized from the melt under different conditions was investigated by means of WAXD and DSC.The isothermal melt crystallization of s-PP proceeded in form I at t_c≥110 ℃ and in form Ⅱ at t_c<110 ℃.S-PP crystallized nonisothermally from the melt was the mixture of forms Ⅰ and Ⅱ.With increasing the cooling rate(a), the content of form I increased, and the content of form Ⅱ decreased.On heating, at 10 K/min, of quenched s-PP, it crystallized in form Ⅱ at t<70 ℃, continuing heating resulted in form Ⅱ→form I transition, which was an endothermal process.

Water Dissociation Phenomena on a Bipolar Membrane——Current-voltage Curve in Relation with Ionic Transport and Limiting Current Density

XU Tong-wen, YANG Wei-hua

2001, 17(4):  457-464. 

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The water dissociation mechanism on a bipolar membrane under the electrical field was investigated and characterized in terms of ionic transport and limiting current density.It is considered that the depletion layer exists at the junction of a bipolar membrane, which is coincided with the viewpoint of the most literatures, but we also consider that the thickness and conductivity of this layer is not only related with the increase of the applied voltage but also with the limiting current density.Below the limiting current density, the thickness of the depletion layer keeps a constant and the conductivity decreases with the increase of the applied voltage;while above the limiting current density, the depletion thickness will increase with the increase of the applied voltage and the conductivity keeps a very low constant.Based on the data reported in the literatures and independent determinations, the limiting current density was calculated and the experimental curves Ⅰ- Ⅴ in the two directions were compared with the theoretical calculations.It is demonstrated that above the limiting current density, the experimental results,either in the L-H direction or in the H-L direction, are consistent with the theoretical calculations; below the limiting current density, a slight deviation exists between the experimental and the theoretical results, and between the experimental results in the two directions.The change in Donnan potential due to the asymmetry of the mono-layers and the changes of ionic composition in the two directions is possibly responsible for this deviation.

Letters

Preparation and Photocatalytic Application of the Microporous Decatungstate, Na₄W₁₀O₃₂/SiO

GUO Yi-hang, HU Chang-wen, WANG Xin-long, WANG En-bo, FENG Shou-hua, YUE Bin

2001, 17(4):  465-468. 

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Research Notes

Two New Flavone Glucosides from Serratula strangulata

DAI Jing-qiu, ZHU Qi-xiu, YANG Li, LI Yu

2001, 17(4):  469-472. 

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Laser Double Ablation Reactions of Chromium(Iron) and Sulfur Clusters

LIU Peng, ZHANG Xia, GAO Zhen, ZHU Qi-he

2001, 17(4):  473-476. 

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