Table of Content

15 July 1996, Volume 12 Issue 3

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Content

Investigation of Synthesis and Ionic Conductivity of Na₅Ysi₄O₁₂

CUI De-Bang, PANG Guang-sheng, FENG Shou-hua, XU Ru-ran

1996, 12(3):  219-226. 

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Single-phase Na₅YSi₄O₁₂(NYS) was prepared by both conventional solid state reaction and sol-gel process. The formation of NYS was monitored by means of X-ray diffraction (XRD) and scanning electron microscope(SEM) techniques. The thermal stability of major impurity phases corresponding to different polymerization states of silicon was discussed. The conditions for preparing single-phase NYS ceramic with a high ionic conductivity were given.

New Routes to the Synthesis of Mesoporous Materials and Their Properties

SUN Yan, LIN Wen-yong, HUO Qi-aheng, PANG Wen-qin, YUE Yong

1996, 12(3):  227-234. 

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The factors that influence the hydrothermal synthesis of MCM-41 were investigated, and it was found that compared with those from high H₂O/SiO₂ systems(designated MCM-41-A), the products from low H₂O/SiO₂ systems(designated MCM-41-B) exhibited a less-defined X-ray powder diffraction (XRD) pattern with a broader main reflection peak at a lower 2θ diffraction angle. MCM-41-B possesses a smaller surface area but a larger pore size than MCM-41-A. New routes including direct thermal treatment, room-temperature crystallization and microwave heating were developed for the formation of MCM-41, and the properties of the products prepared from these new routes were compared with those of the MCM-41 hydrothermally synthesized. The pore sizes of MCM-41 materials are uniformly distributed with an effective pore diameter that falls into the range of 2-4 nm, where as the products from wet-gel thermal treatment possess two kinds of mesopores:the well-defined smaller pores distributed at 3 nm and the larger one within 8-20 nm. The MAS NMR spectroscopy revealed that after calcination to remove the organic template in Al-containing MCM-41, a small part of the tetrahedrally-coordinated framework aluminum atoms became octahedrally-coordinated and a considerable amount of Si-OH species were generated.

Photochemical and Thermal Reactions of Quinones with p-Chlorothiophenol in Solid State and in Solution

WANG Yong-mei, DU Da-ming, CHEN Xiao-min, MENG Ii-hen, ZHANG Hui-ping

1996, 12(3):  235-239. 

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The solid stare reaction (at room temperature) and photochemical reaction of p-benzoquinone, 1, 4-naphthoquinone, anthraquinone wth p-chlorothiophenol were investigated. Six new products were obtained, and the structures of these compounds were identified by means of IR, MS. ¹H NMR and elemental analysis.

Trace Element Analysis in Compound Semiconductor Material by Resonant Laser Ablation/Ionization Mass Spectrometry

Peng Wei-xian, Dens, R., Ledingham, K. W. D., Singhal, R. P.

1996, 12(3):  240-244. 

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The trace element Zn in the Zn-doped multi-layer ш - V group compound semiconductor was detected by means of Resonant Laser Ablation/lomzation(RLA). A detection limit of 2. 5 X 10¹⁷ atoms/cm³ (about 5 ppm) has been estimated. The mass spectra and the optical resonant ionization spectrum around 214 nm are given in this paper.

Fabrication of Thionin-Toluene Diisocyanate Modified Electrode and Its Electrocatalytic Oxidation to NADH

YU Ai-min, HAN Ji-lin, YANG Ke-sheng, ZHANG Hai-lin, CHEN Hong-yuan

1996, 12(3):  245-252. 

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The chemically modified electrode constructed by chemically cross-linking of redox mediator thionin with toluene diisocyanate(TDI) directly at the surface of a spectrographic graphite electrode shows a significant electrocatalytic activity to the oxidation of reduced nicotinamide adenine dinucleotide(NADH) with oxidation overpotential reduced by 310mV.In the potential range from-0.1 to 0.3V,the adsorbed thionin -TDI behaves as a one electron and one proton reversible redox process. The modified electrode achieves a steady-state current of NADH within 20s and the detection limit is about 1.5μm.

A High Selective Chemiluminescence Reacton of Guanine and Its Analytical Application

CI Yun-xiang, LI Jia, ZHEN Yuan-gang, LI Yuan-zong

1996, 12(3):  253-257. 

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A high selective quantitative method for the determination of guanine was established based on a well-known copper-phenanthroline complex mediated oxidation of DNA.The affecting factors for the reaction were studied in a HAc-NaAc buffer solution at 37℃. The optimized conditions for the quantitative determination of guanine are: pH5.2; [Cu²⁺]=80μmol/L; [ascorbic acid]=0.4μmol/L; [phen]=7μmol/L and 1.1%H₂O₂.Guanine could be determined in the range of 1.0-10.0μmol/L.The recoveries of guanine in synthetic sample were within 90%-110% with up to 6 times' excess of other bases.This method is simple,fast and selective.It may be used as a routine method for the determination of guanine without the perseparation of other nucleic acid bases.

Studies on Nucleosides(Ⅵ)-Stereoselective Synthesis of Triazoline-thione NuCleosides

CHEN Hong-ming, ZHANG Jian, MAO Jian-min, CAI Meng-shen

1996, 12(3):  258-263. 

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A series of heterocyclic compounds of triazole thione substituted by tetrazole(I)were prepared using nicotinic acid as starting material through several steps.They reacted with 1-O-trifluoroacety1-2,3,5-O-tri-benxoyl-β-D-ribofuranose(Ⅱ) inanhydrous CH₂Cl₂ at room temperature in the presence of BF₃·Et₂O to give nine new nucleosides, named as 3-[5-(3-pyridyl)-tetrazol-2-yl-methylene]-4-aryl,2,4-triazole-5-(4H)-thione-2, 3, 5-O-tribenwyl-β-D-ribo-furanoside(Ⅲ)(Ar=C₆H₅,o-MeC₆H₄,m-MeC₆H₄,p-MeC₆H₄,o-MeC₆H₄,p-MeC₆H₄,p-EtOC₆H₃,3,4-Me₂C₆H₄,a-C₁₀H₇).The structures and compositions were characterized by means of elemental analysis and spectroscopic methods.

Theoretical Studies on the Coordinate Exchange Reaction of the Dihydrogen Between Formic Acid and Water

YANG Guang-hui, XIN Chun-mei, ZHAO Cheng-da

1996, 12(3):  264-269. 

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The intermolecular hydrogen bond and coordinate exchange reaction of the dihydrogen between formic acid and water were studied by means of ab initio MO method at 6-31G basis set. The transition state of the reaction and the changes of some physical quantities of the reaction systems in the path of the intrinsic reaction coordinate(IRC) were obtained.. The results show that the exchange reaction of the dihydrogen between formic acid and water is coordinate and almost simultaneous.The frequency factor and activation energy of the reaction were also estimated.

In situ Electronic Spectroscopic Techniques far Interfacical Electrochemistry

LUO Jin, LIN Zhong-hua, WU Ling-ling, HUANG Yin, TIAN Zhao-wu

1996, 12(3):  270-279. 

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The present paper cover a measurement system combining reflection spectroscopy photocurrent spectroscopy and photocapacitance spectroscopy, and a measurement system for time resloved reflection and transmission spectroscopy in the ultraviolet-visible spectral region built in suit to characterize electrochemistrical processes. A differential or subtractive spectral method with recpect to an electrode potential change has been adopted in both systems in order to obtain a high S/N ratio.

An XPS Study of Perovskite Oxides RECr0₃

Kang Zhi-jian, LI Li-ping, WEI Quan

1996, 12(3):  280-284. 

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Perovskite Oxides RECr0₃ (RE=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb) were prepared by the means of solid state reaction.The measurments of XRD and XPS showed that the replacement by rare earth element lowers the binding energy(BE) of rare earth ions, compared with their sesquioxides. In the Perovskite Oxides, the BE of Cr2p_3/2 increases with the decrease of ionic radius of the RE ion.The reason for the changes of BE are discussed.

Mechanism of Methane Partial Oxidation over SiO₂-Supported Nickel Catalyst

WANG Hai-you, AU Chaktong, WAN Hui-lin

1996, 12(3):  285-290. 

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The partial oxidation reaction of mathane over reduced 10wt%Ni/SiO₂ catalyst was studied at 600, 650, 700℃ by means of pulse and bond-order conservation Morse-potential (BOC-MP) methods. In the oxidation reaction of surface carbon deposited on the catalyst, it was observed that the product selectivity was subject to the reaction temperature and the selectivity of CO was increased with rasing temperature of CH₄/O₂, the same trend between CO selectivity and reaction temperature was also observed, implying that the partial oxidation of methane to syngas follows the pyrolysis mechanism under the reaction conditions. The BOC-MP calculation on the elementary reaction steps over Ni(111) surface indicates that the direct dissociation of CH₄ without the involvement of surface oxygen is more likely to occur and the formation of CO from CH(s) occurs more readily than from C(s).

TPSR Studies of the Activation of Methane on Supported Noble Metal Catalysts

YAN Zi-feng, SONG Lin-hua, XUE Jin-zhen, SHEN Shi-kong

1996, 12(3):  291-295. 

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Methane decomposition on silica-supported noble metal catalysts was deeply investigated by means of the temperature programmed surface reaction (TPSR).The results obtained show that methane can be effectively decomposed into different surface carbons, which show different reactivities and features to form higherhydrocarbons.

A Light Active Barbituric Acid Derivative as A Fluorescence Probe of Molecular Self-assembly

YANG Wen-sheng, CHAI Xiang-dong, LU Ran, CAO Yun-wei, JIANG Yue-shun, TANG Xin-yi, LI Tie-jin, WANG Wei-wei, FU Lian-she, ZHANG Hong-jie

1996, 12(3):  296-299. 

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A light active barbituric acid derivative,5-(4-N, N-didodecylaminobenzylidene)-2,4,6-(1H,3H)-pyrimidinetrione(B), was found to be used as a fluorescence probe of molecular recognition directed self-assembly with its complementary compound, 4-amino-2,6-didodecylamino-1,3,5-triazine(M).

Studies on Composites of Nanoparticles and Some Polymers

BIAN Feng-lan, DU Hui, ZHANG Chang-mei, LIU Xi-sheng, SHEN Jia-cong, YAN Xi-jie

1996, 12(3):  300-303. 

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The metal oxide nanoparticle of Cr₂O₃ was made into a composite with the polymers, which is of novel functions. Surfactants solubilized agents were used to increase compatibility between the two phases. The. application of the new products is described.

Anticancer Drugs (VI)——Synthesis and Activity of Spin Labeled Derivatives of 4-Amino-4-deoxy-4′-demethylepipodophyllotoxin

TIAN Xuan, YANG Ming-gui, JI Zhu-sheng and CHEN Yao-zu, HE Xiao-qing, LEI Xiao-hong, HAN Rui

1996, 12(3):  304-308. 

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Some derivatives of podophyllotoxin(1), such as etoposide(12), possess antitumor activity and have been extensively used clinically^[1]. Because etoposide has a less solubility in water and higher toxicity, many chemists have an interest in further studies on the modification of the C-4 substituent of 1 for its better antitumor activity. Lee Kuo-hsing, Wang Zhe-qing et al. have synthesized a series of derivatives of CA (substituted anilino)-4-deoxypodophllotoxin. The pharmaceutical tests have shown that a number of 4β-(arylamino )-4'-demethylepi-podophyllotoxin are as potent as or more potent than etoposide(12) in inhibiting the human DNA topoisomerase Ⅱ.

Studies on the Interaction of Poly(I:C) with Heterocyclic Compounds Containing Iodine

HUA Er-bing, YANG Pin, YANG Bin-sheng, ZONG Jian-chao

1996, 12(3):  309-312. 

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The iodine heterocvclic compound with trivalent-iodine as the cation has a specially remarkable antitumor activityii^[1]. Although 3, 6-bis (dimethylamino)-dibenzopyriodonium formate([I⁺]) inhibits DNA biosynthesis of cancer cells in vitro, the way of [I⁺] depressing DNA synthesis has not been studied. It is significant to investigate the mechanism of the interaction of [I⁺] with nucleic acids.