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    24 March 2001, Volume 22 Issue 3
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    Articles
    Annealed Crystallization of Ni-B and Ni-Ce-B Ultrafine Amorphous Alloys Studied by EXAFS
    WANG Xiao-Guang, YAN Wen-Sheng, ZHONG Wen-Jie, ZHANG Xin-Yi, WEI Shi-Qiang
    2001, 22(3):  349-354. 
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    EXAFS technique was used to quantitatively determine the local structure evolutions of Ni-B and Ni-Ce-Bultrafine amorphous alloys prepared by chemical reduction during the annealed process. The results show that the average bond length Rj, coordination number N, thermal disorder factor σTand static disorder factor σSare 0.275 nm, 11.9, 0.0069 nm, 0.034 nm; 0.215 nm, 2.7, 0.0055 nm, 0.0038 nm, and 0.276 nm, 12.4, 0.0067 nm, 0.035 nm; 0.214 nm, 2.9, 0.0058 nm, 0.0042 nm for the Ni-Ni and Ni-Bfirst neighbor shells of Ni-Band Ni-Ce-Bultrafine amorphous alloys, respectively. It is indicated that the σSof Ni-Ni shell is rather larger, about four or five times as large as that of σT, and one order larger than that of σSof Ni-Bshell. Ni-Bsample is crystallized after being annealed at 300 ℃, and its RNi—Ni as well as σSare 0.254 nm and 0.011 nm, respectively. However, the crystallization temperature of Ni-Ce-Bsample increases about 100 ℃ due to the addition of 0.3% Ce element. The local structure around Ni atom for the Ni-Bsample annealed at 500 ℃ is fully similar to that of Ni foil. For the Ni-Ce-Bsamples annealed at 500 ℃, the σSof Ni-Ni shell is 0.0073 nm and the N of Ni-Bshell is 1.2. It implies that the Ni lattice produced from the crystallization of Ni-Ce-Bamorphous alloys is significantly distorted and the interaction between Ni and Batoms is strongly increased by the effect of Ce element.
    Co-deposited Synthesis of Nanosize Pb3Nb2O8 Powder
    ZHAO Hui, XIE Hong, FENG Shou-Hua
    2001, 22(3):  355-357. 
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    Nanosize Pb3Nb2O8 powder has been obtained at 90 ℃ from Nb2O5-PbO-KOH-H2Osystem. The influence of starting materials and their molar ratios, pHvalue of the solution and the synthesis temperature were systematically investigated. Soluble niobate and lead acetate have been chosen for the synthesis of Pb3Nb2O8. Pure phase product could be obtained when the molar ratio of Pb to Nb is close to 1, and concentration of KOHto 1—3 mol/L. PbOappears as the main phase when KOHconcentration is greater than 3mol/L.
    Energy Transfer from Ce3+ to Eu2+ and Electron Transfer from Ce3+ to Eu3+ in BaY2F8:Ce, Eu Systems
    ZHANG Xian-Ming, SU Hai-Quan, YE Ze-Ren, JIA Zhi-Hong, ZANG Chun-Yu, SHI Chun-Shan
    2001, 22(3):  358-361. 
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    Phorsphors of BaY2F8:Ce 3+, BaY2F8: Eu 2+ and BaY2F8:Ce, Eu were prepared by higher temperature solid reaction and their excitation, emission and diffuse reflection spectra were made. We firstly found that the competition of energy transfer from Ce 3+ to Eu 2+ and electron transfer from Ce 3+ to Eu 3+ existed in CeF3 and EuF3-co-doped BaY2F8 systems. The f-f transition emission of Eu 2+ was increased with increasing x in systems BaY2F8:0.03Ce, x Eu. Ce 4+ ions coexist with Ce 3+ ions and substitute Y 3+ for Ce 4+ in the systems BaY2F8:Eu, Ce.
    Synthesis and Crystal Structure of a Novel Amino-acid-containing Polyoxometalate: K6[Cu(Ala)2(H2O)2]2[Cu4(H2O)2(AsW9O34 )2]·16H2O
    WANG Yong-Hui, HU Chang-Wen, WANG En-Bo, Hu-Ning-Hai, Jia-Heng-Qing, Xing-Yan
    2001, 22(3):  362-364. 
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    The novel amino-acid-containing polyoxometalate K6[Cu(Ala)2(H2O)2]2[Cu4(H2O)2·(AsW9O34 )2]·16H2Owas synthesized from the reaction of K10 [Cu4(H2O)2(AsW9O34 )2]·20H2Owith β--alanine. Its structure has been determined by single crystal X-ray diffraction. It crystallizes in the triclinic space group P1, with a=1.1963(2) nm, b=1.5365(3) nm, c=1.5914(3) nm, α=93.97(3)°, β-=110.88(3)°, γ=101.07(3)°, V=2.6518(9) nm3 and Z=1. Least squares refinement of the structure leads to Rand Rw factors of 0.0673 and 0.1628, respectively. An unusual structural feature of the compound is that the polyanion [Cu4(H2O)2(AsW9O34 )2]10- is linked with the amino acid complex of Cu 2+ by a μ-oxygen atom.
    The Interaction Between Siliceous FAU Zeolites and Adsorptive Methylamine
    LONG Ying-Cai, YANG Hu, SUN Yao-Jun, PING Zheng-Hua
    2001, 22(3):  365-367. 
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    The interaction between the adsorbed methylamine(MA) and siliceous FAUzeolite with a perfect framework is investigated with XRD, 29Si and 13C MAS NMRand FTIR. As methylamine is loaded into the zeolite, the crystal structure of the zeolite changes. One peak splits to four peaks for the 29Si MAS NMRspectrum, and the IRvibration of framework with a high resolution become simpler. The fact indicates that there is a strong interaction between adsorbed methylamine and Si—Oframework of FAUzeolite, leading to high A Tvalue of affinity index for methylamine on the zeolite. The order structure of MA/FAUassociate is discussed as well.
    The Valence and Transport Property Studies for the Solid Solution Ce1-x EuxO2-δ Synthesized by High-temperature and High-pressure
    CHE Yu-Lu, LI Li-Ping, LI Guang-She, LU Zhe, LIN Xiao-Min, XIANG Jun, SU Wen-Hui
    2001, 22(3):  368-370. 
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    The solid solutions Ce1-x Eux O2-δ ( x=0.10—0.50) were synthesized by high-temperature and high-pressure. The XRD measurement showed that the solid solution was crystallized in cubic fluorite-type structure and the lattice parameter increased with the content of Eu increasing up to x=0.4. The solution limit was ca. 0.4 under the condition of 3.6 GPa, 840—1020 ℃. The XPS data showed that the Eu ions are Eu 3+ and trace of Ce 4+ ions were reduced to Ce 3+ ions during synthesis of high temperature and high pressure. The ionic conduction for Ce0.8 Eu0.2 O2-δ was measured by impedance spectroscopy and it was found that the activation energy was 1.07 eVand the conductivity was 3.43×10-5 S·cm-1 at 550 ℃.
    Synthesis of Molecularly Imprinted Microspheres Polymer with 4-Aminopyridine as Template and the Study of Their Binding Characteristics
    GUO Hong-Sheng, JIA Yu-Mei, CAO Xian-Feng, HE Xi-Wen
    2001, 22(3):  371-375. 
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    The molecularly imprinted microspheres using 4-aminopyridine as template were prepared with precipitation polymerization. The batch way was used to investigate the selectively binding ability of the microspheres for 4-aminopyridine. The effects of different amount of solvent and initiator on the shape and the size of the particles were studied. The substrate selectivity of the polymer was investigated. The results showed that the imprinted polymer exhibited a high affinity for 4-aminopyridine among the tested compounds.
    Fabrication and Photoelectric Conversion Property of Two Bilayer Lipid Membranes Self-assembled on ITO Substrate
    GAO Hong, LUO Guo-An-FENG Jun, Tien-H. T, Ottova-A. L.
    2001, 22(3):  376-379. 
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    Two self-assembled bilayer lipid membranes (BLMand C60 contained BLM ) on indium-tin-oxide (ITO) were fabricated and their photoelectric conversion properties were studied. The investigation of the effects of applied voltage, donor and receptor on the photocurrent intensities showed that the anodic photocurrent of BLMs increased with increasing anodic potential and donor concentration; C60 doped in BLMfacilitated the photoinduced electron transfer across bilayer membranes. This novel self assembled ITO/BLMelectrode can provide a simple and mechanically stable model for the study of the photoelectric properties of biomembranes.
    Studies on the Voltammetric Behavior of Mitoxantrone and Its Application at the Ni/GC Modified Electrode
    HU Jing-Bo, LI Qi-Long
    2001, 22(3):  380-384. 
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    In a 0.1 mol/L NH3 NH4Cl buffer solution(pH9.50), a sensitive reduction peak of mitoxantrone at a Ni/GC modified electrode was obtained by linear-sweep voltammetry. The peak potential was -0.85 V( vs. SCE). The peak current was proportional to the concentration of mitoxantrone. The detection limit was 18×10-8 mol/L. Its voltammetric behavior was studied and the wave was applied to the determination of mitoxantrone in urine. The reduction process was quasi-reversible with adsorption and catalysis. AES and XPS experiments showed that Ni was surely implanted into the surface of the GCE, and the implanted Ni at the GCimproved the electrocatalytic activity.
    The Dynamic Simulation of Chromatographic Separation of Citric Acid
    PENG Qi-Jun, XU Ling, SUN Pei-Dong, YANG Li, QIAN Yong
    2001, 22(3):  385-388. 
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    This paper provides a suitable method for studying thermal swing chromatographic kinetics and estimation of model parameters, considering the change of bed porosity. As an experimental example, the separation of the citric acid is discussed. The model parameters were measured on an analytical column. With these thermodynamic parameters it was attempted to simulate the separation behaviour in larger columns using the equilibrium dispersive model, the result was very satisfactory.
    Genosensors and Strategies for the Research and Development
    PANG Dai-Wen, YAN Wei
    2001, 22(3):  389-395. 
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    Recent featured researches on optical, piezoelectric, and electrochemical biosensors for gene detection are reviewed. Some related issues, including reliability, sensitivity, applicability, and antidisturbance, etc., involved in genosensors are discussed. And the strategies for the immobilization and characterization of gene probes, molecular hybridization on the surfaces, effective transduction of hybridization signals and related detection techniques are proposed.
    A Novel Fluorescence Probe for the Determination of Hydroxyl Radicals
    YANG Xiao-Feng, GUO Xiang-Qun
    2001, 22(3):  396-398. 
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    Anovel technique for the determination of the hydroxyl radical is described in this paper. The method employed the reaction of hydroxyl radical with dimethyl sulfoxide to generate a methyl radical quantitatively, which then coupled with the nitroxide-linked naphthalene and led to a large increase in fluorescence intensity. The proposed method was demonstrated to be capable of detecting hydroxyl radicals generated in the Fenton systems. It proved to be a simple and sensitive technique for the determination of hydroxyl radicals.
    Stereo-effect of the Peptide Formation Reaction by N-(O,O-Diisopropyl) Phosphoryl Serine
    HU Jian-Jun, JU Yong, ZHAO Yu-Fen
    2001, 22(3):  399-402. 
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    The reactions between N-phosphoryl-L -or D-) serine and L-(or D-) histidine or L-(or D-) histidine methyl ester were investigated. Products of the reaction mixtures were analyzed by ion-pair reversed-phase HPLC with SDS as the ion-pairing reagent. The results showed that dipeptide serylhistidine was formed in all these reaction systems, and L-L and D-D types of serylhistidine were yielded in an amount about four times as much as that of the L-D and D-L type dipeptide.
    Generation and Application of Polyclonal Antibodies Against Low Molecular Weight Purple Acid Phosphatase
    FAN Hong-Kuan, ZHENG Yuan-Zhi, Hamilton Susan, de Jersey John
    2001, 22(3):  403-406. 
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    There exists two groups of purple acid phosphatases(PAPs). Mammalian PAPs, which are monomers with molecular weight in the range of 33000-40000. Plant PAPs, which are dimers or tetramers containing identical subunits of about 55000. Recently the gene of low molecular weight PAPs(smPAPs) was found in plant. They are significantly similar to mammalian PAPs' but quite different from plant PAPs'. In order to understand the exact function of the protein and its distribution in plant, we cloned the sweet potato smPAPgene in pGEX-2T vector and expressed the fusion protein in E. coli. The expressed fusion protein was used to generate polyclonal antibodies. The antibodies demonstrated a good reactivity towards the smPAPexpressed in baculovirus and PAPs partially purified from sweet potato juice. Therefore, the antibodies make it possible to purify and characterize the smPAP.
    Structure Elucidation and Immunoactivity Studies of Glycan of Glycoconjugate LbGp4 Isolated from the Fruit of Lycium barbarum L.
    HUANG Lin-Juan, TIAN Geng-Yuan, QI Chun-Hui, ZHANG Yong-Xiang
    2001, 22(3):  407-411. 
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    Glycan was isolated on Sephadex G-100 column after glycoconguate LbGp4 was released by β--elimination, then desalted on Sephadex G-25 and named LbGp4-OL. The linkage between the glycan and the core protein backbone was Olinkage. The molecular weight of LbGp4-OL was 180800. The result of its elemental analysis was C39.1%, H5.72%, N 0%. Component analysis showed that it was composed of Rha, Ara and Gal in a molar ratio of 0.05 : 1.33 :1. The structure of repeat unit of LbGp4-OL was deduced by methylation analysis, partial acid hydrolysis and 1H, 13C NMRspectroscopy of the original glycan and products of its partial hydrolysis. Methylation analysis of LbGp4-OLindicated that highly branching unit in LbGp4-OLwas →3,4)Gal(1→, the major non reducing end was Ara(1→. LbGp4-OL' was obtained by partial acid hydrolysis. Comparing the results of methylation analysis of LbGp4 with that of LbGp4-OL', we can deduced that the main chain of LbGp4-OLwas composed of →4)Gal(1→. 1H and 13C NMRspectra of LbGp4-OLand LbGp4-OL' indicated that Ara(1→ was α-furanose, →3)Ara(1→ and →5)Ara(1→ were β- furanose, all the Gal were β- pyranose, Rha(1→ was α-pyranose, →3)Arap(1→ was α-pyranose. Immunoactivity studies of LbGp4 and its glycan showed that LbGp4 and LbGp4-OLnot only enhanced the splenocyte proliferation in normal mouse, but also improved the reducing immune function in the senescense accelerated mouse. It demonstrated that LbGp4 and LbGp4-OLpossess a direct effect of splenocytl proliferation. In addition, the direct elevating action of LbGp4-OLon splencyte prolifexration was stronger than that of LbGp4. So it pointed out that the glycan play an important role in the immunopharmcological activity of glycoconjugate.
    Synthesis and Crystal Structure of Speleand Imidazolium Cyclophane
    YUAN Yi, JIANG Zong-Lin, GAO Ge, YAN Jia-Ming, XIE Ru-Gang, YU Kai-Bei
    2001, 22(3):  412-416. 
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    Aspeleand imidazolium cyclophane [C30 H33 N6 3+ ·Br3-·3H2O](2,21,29-trimethyl-5,16,24-triaza-8,19,27-triazonia heptacyclo [10.10.6.11,3.15,8.110,14.116,19.124,27 ]tritriazonia- 1,3(29),6,8(30),10,12,14(31),17,19(32),21,25,27(33)-dodecene tribromide trihydrate was synthesized by direct quaterisation of 1,3,5-trimethyl- 2,4,6-tri(imidazolylmethyl)benzene with m-tri(bromomethyl)benzene in high yield. Its molecular and crystal structures were characterized by 1H NMR, FAB-MS, elementary analysis, IR, UVand X-ray diffraction. The crystal is of monoclinic system, space group P21 with a=0.8634(2) nm, b=0.8170(4) nm, c=1.0884(2) nm, β=112.03(1)°, V=1.5828(6) nm3, Z=2, R=0.0336, F (000)=780. The bromides form hydrogen bonds with water molecules. The molecular structure indicates that the title compound can selectively recognize some anions or neutral molecules.
    The Synthesis and Crystal Structure of a New Macrocyclic Ligand, BDBPH
    SHANG GUAN Guo-Qiang, MartellA. E, Zhang Z. R, Reibenspies J
    2001, 22(3):  417-420. 
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    Anew dinucleating 24-membered hexaazadiphenol macrocyclic ligand, 3,6,9,17,20,23-hexaaza 29,30-dihydroxy-13,27-dimethyl tricyclo[23,3,1,111,15]triaconta-1(28),11,13,15(30),25,26-hexaene (BDBPH), was synthesized by the NaBH4 reduction of the Schiff base obtained from the [2+2] condensation between diethylenetriamine and diformyl-p-cresol. The crystal structure of the hexahydrobromide salt of BDBPH, BDBPH·6HBr·4H2O, was determined by single crystal X-ray diffractometry. It crystallized in the monoclinic system, space group P21/c , with a=1.4441(5) nm, b=1.1482(4) nm, c=1.2090(6) nm, α=90°, β=96.92°, γ=90°, V=1.9900(4) nm3 and Z=2. The macrocyclic ligand adapts a chair conformation, the crystallographic inversion center is located in the macrocyclic cavity, the six bromide ions and four water molecules are situated symmetrically outside the macrocyclic cavity. The new ligand with structural characteristics can be used for the study on the stabilities and catalytic properties of the corresponding metal complexes.
    Asymmetric Synthesis of α-Amino Acids
    HU Ai-Guo, WANG Shan-Wei, HAN Jun, WANG Ji-Tao
    2001, 22(3):  421-430. 
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    According to the synthetic methodology, the asymmetric synthesis of α-amino acids was reviewed, including asymmetric hydrogenation of α,β- didehydroamino acids, electrophilic addition of glycine equivalent in the presence of cPTC, electrophilic addition of glycine equivalent covalent bonded with chiral auxiliary, elaboration of chiral α-amino acids and chiral Strecker reaction.
    Preparation of Au/ZnO Catalyst and Its Catalytic Performance for CO Oxidation at Ambient Temperature and Moisture
    WANG Gui-Ying, LI Xue-Mei, BAI Ni, ZHANG Wen-Xiang, JIANG Da-Zhen, WU Tong-Hao
    2001, 22(3):  431-434. 
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    The catalytic performance of Au/ZnOcatalysts prepared by a coprecipitation method for COox-idation at ambient temperature and moisture was studied. It was found that the chemical composition, the activity and the stability of the catalysts were greatly changed with the variation of calcination temperature. The sample calcined at 240 ℃ showed the best stability, i.e. it can maintain COcomplete conversion for 600 h. XRD, FTIR, TEMand UV Vis results indicated that gold could be highly dispersed on the surface of ZnCO3 or ZnO, with the mean diameter of gold particle being2—5 nm. The type of support was the main influencing factors on the stability of Au/ZnOcatalysts, the stability of ZnOsupported gold catalysts was better than that of the ZnCO3 supported gold samples. The smaller of ZnOparticle and the bigger of S BET, the better of the stability of Au/ZnOcatalysts was obtained.
    Investigation on the Adsorption of Polyvalent Low-molecular-weight Dispersants on Alumina
    LIU Yang-Qiao, GAO Lian, GUO Jing-Kun
    2001, 22(3):  435-438. 
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    The adsorption of 2-phosphonobutane 1,2,4-tricarboxylic acid (PBTCA) and citric acid on alumina was determined by using the ferric 5-nitrosalicylate spectroscopic method. The saturation adsorption of PBTCAwas found to be much higher than that of citric acid. FTIRand AESresults revealed that the phosphonyl group participated in the chemisorption of PBTCAonto alumina. The higher dispersing efficiency of PBTCAthan citric acid was attributed to its high number of charges and high chelating ability at high pH.
    Mass Spectrometric Studies of Metallofullerene
    GUO Tan, XING Jun-Peng, JI Yi-Ping, LIU Zhi-Qiang, LIU Shu-Ying, FENG Ji-Kang
    2001, 22(3):  439-442. 
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    The endrohel metallofullerene, Gd@C82, Gd@C80, Gd2@C80 were synthesized by using K-Hmethod. The technique of two-step of high pressure and high temperature extraction with 1,3,5 trimethylbenzene(first step) and pyridine(second step) has been successfully utilized to extract metallofullerene of Gd@C82. The gas-phase negative ions of fullerenes Cn(n=60, 70, 78, 82, 84…) and metallofullerene (Gd@C82 ) have been studied by the ESI-MS, REC-MSand MALDI-TOF-MS. The differences among the mass spectra of ESI-MS, REC-MSand MALDI-TOF MShave been observed and explained. In contrast to the empty fullerene C82, the metallofullerene Gd@C82 should have a larger HOMO-LUMOgap. Experimental results suggest that Gd@C82 is polarized and Gd 3+ located in the off center position of C82 cage after Gd 3+ is trapped into C82 cage.
    Microwave-assisted Heterogeneous Photocatalytic Oxidation of Ethylene
    ZHENG Yi, LI Dan-Zhen, FU Xian-Zhi
    2001, 22(3):  443-445. 
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    Porous TiO2 and SO42-/TiO2 catalysts were prepared by sol-gel method and charaterized by XRD, N2 sorption analysis applying BETmethod, and microwave absorption spectrum. Photocatalytic oxidation of C2H4 in air stream was studied. The results showed that the photocatalytic activity of both SO42-/TiO2 and TiO2 catalysts was obviously increased under the reaction condition of ultraviolet combined with microwave. The conversions of ethylene over TiO2 and SO42-/TiO2 were enhanced from 20% and 41%(UV) to 27% and 62%(UV+MW), respectively. The effect of MWon SO42-/TiO2 catalyst was more notable. The improvement on photocatalytic activity was attributed to the polarization effect of the highly defected catalysts in microwave field, which increased the transition probability of photon generated electrons and decreased the electron-hole recombination on semiconductor surface.
    Purification of Carbon NanotubesOxidation Method by Using Electrochemistry
    YANG Zhan-Hong, WU Hao-Qing, LI Jing, LI Xin-Hai
    2001, 22(3):  446-449. 
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    Carbon nanotubes were purified by use of electrical chemistry oxidation method. In the view of polarization curves it was discussed that electrochemistry method could be used in the purification of carbon nanotubus. The influence of current density, sulfuric acid concentration and reaction time on the reaction was studied, the optimum experimental condition was obtained and the mechanism of purification was also discussed.
    Electrochemistry and Electrocatalysis with Myoglobin at DDAB-clay Multibilayer Composite Film Electrodes
    HU Nai-Fei, LI Zhen, MA Hong-Yan
    2001, 22(3):  450-454. 
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    Mb-DDAB-clay film electrodes were made by casting aqueous dispersions of didodecyldimethylammonium bromide(DDAB)-clay composite and the protein myoglobin(Mb) on pyrolytic graphite(PG) electrodes. Cyclic voltammetry of Mb-DDAB-clay films showed a pair of well defined and nearly reversible peaks at about -0.25 Vvs. SCEin pH5.5 buffers, being the characteristic peaks of the Mb heme Fe(Ⅲ)/Fe(Ⅱ) redox couples. In the microenvironment of DDABclay films, the electron transfer between Mb and PGwas greatly enhanced, and showed a good stability during storage. Soret absorption band positions suggested that Mb retained its native conformation in these films at medium pH. The interlayer clay spacing estimated by X-ray diffraction suggested that the incorporated Mb did not disturb the ordered multilayer structure of the films. The average formal potential of Mb heme Fe(Ⅲ)/Fe(Ⅱ) couples in DDAB-clay films shifted linearly from pH4.5 to 11 with a slope of -53 mV/pH, suggesting that one proton was coupled with each electron transfer. The dissolved oxygen and trichloroacetic acid was catalytically reduced by Mb-DDAB-clay film electrodes.
    Theoretical Study on the Mechanisms of Some Elementary Reactions Catalyzed by Modified Carbonyl Cobalt
    LEI Ming, FENG Wen-Lin, XU Zhen-Feng, XU Heng-Lian
    2001, 22(3):  455-459. 
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    All structural geometries of intermediates, transition states and product are optimized at HF/LANL2DZlevel under the effective core potential approximation. The potential energy profile for some elementary reactions of hydroformylation catalyzed by Co 2(CO)6(PH3)2, consisting of carbonyl insertion, H2 oxidative addition and aldehyde reductive elimination, are calculated. The transition states are further confirmed by having one and only one imaginary vibrational frequency. The activation energies of carbonyl insertion, H2 oxidative addition and aldehyde reductive elimination are 54.02, 134.02 and 43.44 kJ/mol, respectively.
    A Density Functional Study on the Electronic Structures and Mechanic Property of MX (M=Sc, Ti, V; X=C, N, O) Solids
    LI Jun-Qian, ZHANG Yong-Fan
    2001, 22(3):  460-464. 
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    The electronic structures and mechanic properties of MX (M=Sc, Ti, V; X=C, N, O) solids are investigated by using density functional theory(DFT). The results show that the mononitrides have the greatest bulk modulus. Under high compression, the calculations indicate that all compounds will undergo a structural phase transition from NaCl to CsCl structure, and the transition volume decreases from MC→MN→MO. The band structures and density of states of each compound are also calculated by DFTmethod, and the conductivity of this class of compounds is discussed.
    Mass Spectrometry and Quantum Chemistry Study on the Methanol Dehydration to Dimethyl Ether
    LIANG Yu, MAO Yan-Mei, ZHONG Kai, LIANG Ze-Bin
    2001, 22(3):  465-469. 
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    Mass Spectrometry and quantum chemistry ab initio method have been used to study the reactivity of the methanol dehydration. It is shown that the methanol dimer and methanol cluster are the predominant species of methanol in gaseousness. So we believe that rather the methanol dimer is the original reactant of the methanol dehydration reaction to dimethyl ether than the mono-methanol. The structure and energy of the methanol dimer and the transition state for the dehydration reaction have been studied. It is discussed that the reaction pathway and factors influenced the reactivity of methanol dehydration to dimethyl ether theoretically.
    Structure and Self-assembly Mechanism of Self-assembled Monolayers
    YANG Sheng-Rong, REN Si-Li, ZHANG Jun-Yan, ZHANG Xu-Shou
    2001, 22(3):  470-476. 
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    The technology of self-assembled monolayers (SAMs) has grown into an extremely active research field. In this paper some important results in this field, especially the structure and the self-assembly mechanism of SAMs, are reviewed. The important subject to be solved and the future directions of SAMs are also given.
    Scaling Laws for Pseudobinary Microemulsions
    AN Xue-Qin, HUANG You-Guo, SHEN Wei-Guo
    2001, 22(3):  477-478. 
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    The coexistence curves of three pseudobinary microemulsion systems, consisting of surfactant, water and n-alkane, were determined by measurements of refractive index. The critical exponent β was deduced precisely from coexistence curves, which are consistent with the 3D-Ising exponent when the temperatures approach to the critical points. The experimental results also indicate that the critical amplitude scaling laws for chain molecular solutions are valid for these microemulsion systems.
    Synthesis of 2,2'-Diaminophenyloxydisulfide and Its Polymer
    SU Yu-Zhi, GONG Ke-Cheng
    2001, 22(3):  479-481. 
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    Anovel organic disulfide, 2,2'-diaminophenyloxydisulfide(DAPD) has been prepared by the reaction of o-aminophenol with sulfur monochloride in THF. Its polymer films are formed by electropolymerization from a AN/THFsolution containing 0.1mol/L LiClO4, 0.1 mol/L HCl and 0.05 mol/L DAPDmonomer on Pt electrode under continuous cycling between -0.30 Vand 1.20 Vvs. Ag/AgCl (sat. KCl) at scanning rate 50 mV/s. The cyclic voltammetry shows that its electrochemical behavior is similar to that of polyaniline. The redox peak current of the cyclic voltammograms increase with increasing of the cyclic times. The electronic conductivity of poly (DAPD) can reach from 2.1×10-3 to 8.7×10-3 S/cm. Two main facts are considered to be necessary for obtaining electroactive poly (DAPD) in electropolymerization process. One is the existence of sufficient concentration of the supporting electrolyte to enhance the ionic conductivity of AN/THFsolution and the other is the existence of protons from the acid HCl. With an increase in acid content of the solution, the polymerization efficiency as well as the electroactivity of poly (DAPD) films show a striking enhancement and the electronic conductivity of poly (DAPD) film increases. But the concentration of HCl would be quite high to result in the decomposition of DAPDmonomer.
    Formation of Hypermetallic Molecule LiZnO+ from Laser Plasma
    FU Zheng-Wen, ZENG Xian-Kang, ZHANG Yi-Hua, QIN Qi-Zong, CHEN Hong, HUANG Rong-Bin, ZHENG Lan-Sun
    2001, 22(3):  482-484. 
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    By 355 nm laser ablating a composite target prepared from metallic lithium and ZnOin high vaccum, a new hypermetallic oxide LiZnO+ ion, which consists of two heterometal atoms and oxygen atom, was observed by using a time-of-flight mass spectrometer for the first time. The time-of-flight positive ion mass spectra at different delay time between the accelerated electric field and laser pulse are investigated. It shows that the formation of LiZnO+ depends on the delay time, and the hypervalent ion LiZnO+ is observed obviously at the delay time from 7.5 to 17.5 μs. These results suggest that the ion molecular reaction between the ablated Li+ ions and ZnOin the laser plasma should be responsible for the formation of hypermetallic LiZnO+.
    Effects of p-tert-Butylcalix[4]arene on Thermal Oxidation Stability of Polypropylene and Study of Its Kinetics
    FENG Ya-Qing, HONG Xue-Chuan, LI Xi-Feng, YAN Xi-Long, ZHOU Li-Shan, CUI Yong-Yan
    2001, 22(3):  485-488. 
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    The p-tert-butyl calix[4]arene and polypropylene blend was prepared, and effects of p-tert-butyl-calix[4]arene on the thermal oxidation stability of polypropylene blend were studied by means of thermal gravimetric analysis (TGA).Treated with Coasts-Redfern equation we found that the apparent degradation reaction order of the p-tert-butyl-calix[4]arene and polypropylene blend is 1.413 and the activation energy of degradation reaction is 154.899 kJ/mol.
    The Investigation of Flame Retardancy for Polyethylene Treated by Plasma Grafting of Methylacrylic Acid
    SHI Lai-Shun, WANG Jian-Qi
    2001, 22(3):  489-493. 
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    An attempt has been made in this study to render polymers flame retardancy by a grafting method induced by plasma. Based on polyethylene, it was found that the grafting yield was influenced by the grafting reaction conditions when polyethylene was grafted with methylacrylic acid. The flame retardancy of the grafted sample was characterized. It was found that the time to ignition of the grafted sample was extended. The limiting oxygen index and char residue were increased. This indicates that the side groups of —COOH,—COO-Na+and—COO-K+ the grafted layer can not only be charred in the thermal degradation stage, but also promote the charring of the substrate polymer.
    Synthesis and Characterization of a Series of High Sulfonated Poly(ether ether ketone)s
    LIU Sheng-Zhou, WANG Feng, CHEN Tian-Lu
    2001, 22(3):  494-497. 
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    Aseries of high sulfonated poly(ether ether ketone)s were prepared by copolymerization of sodium 5,5'-carbonylbis(2-fluorobenzenesulfonate)(2), 4,4'-difluorobenzophenone(1) and bisphenol A(3) in the presence of potassium carbonate in dimethylsulfoxide. The copolymers were characterized by IRand DSC. The influence of degree of sulfonation on the properties of copolymers, such as component, thermal stability, solubility and filming ability, was studied.
    Organic/Polymer Photoconducting Mechanism and Image Sensors
    SUN Jing-Zhi, WANG Mang, ZHOU Cheng
    2001, 22(3):  498-505. 
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    The development history of organic/polymer photoconducting image sensors was reviewed briefly; a theoretical comment of scientific researches and main breakthroughs in the field of photoconducting mechanism in the past two decades was evaluated; a series of measurements to improve photoconducting ability and photon/electron conversion efficiency were summarized; a few basic principles for molecular design of novel high performance photoconducting materials and fabrication of prototype photo conducting image sensors were suggested; and the application future of organic/polymer photoconducting image sensors was practically analyzed.
    New Heat-resistant Polybenzoxazine Synthesized by Electrochemical Method
    WAN Xiao-Bo, HE Jin-Bo, XU Ning, XUE Qi, Ishida-H.
    2001, 22(3):  506-507. 
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    Anew kind of polybenzoxazine could be synthesized by electrochemical method in acetonitrile/alkaline aqueous solution. The obtained polymer shows good heat-resistance properties.
    Effects of Annealing Above Glass Transition Temperature Tg on the Liquid-liquid Transition of Atactic Poly(methyl methacrylate)
    GU Qun, SHEN De-Yan
    2001, 22(3):  508-510. 
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    Effects of annealing temperature( Ta) and annealing time( ta) on the liquid liquid transition and transition intensity of atactic poly(methyl methacrylate) were studied by means of differential scanning calorimetry. With the increase of Ta from 393 to 443 K, Tll shifted to higher temperature with the decrease in transition intensity, on the contrary, when Ta was over 443 K, Tll declined and transition intensity increased. When Ta kept constant with the increase of ta, Tll and transition intensity varied as the results described above. Moreover, the variation extent of Tll and transition intensity increased with the increase of Ta, in other words, the time needed reaching the maximum extent of variation of the two parameters was decreased with the increase of Ta. The dependence of Tll and transition intensity on annealing conditions may be explained by the formation of local ordered structure, i.e. stereocomplex, during the annealing process by means of Van der Waals forces between isotacitic and syndiotactic segments of the same or different chains of atactic poly(methyl methacrylate).
    The Effects of Physical Ageing on Crazing of Polyphenylquinoxaline Films
    LIU Wan-Jun, SHEN Jing-Shu, WANG Zhuo, LU Feng-Cai, XU Mao
    2001, 22(3):  511-513. 
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    The effects of physical ageing on the crazing of polyphenylquinoxaline(PPQ-E) films were studied. The DSCendothermic peak at the glass transition region of the samples was interpreted in terms of the cohesional entanglement theory. The free volume cavity size and free volume intensity of the samples were characterized by positron annihilation life spectroscopy. The difference in free volume cavity size and free volume intensity between two samples reflect the strength and density of cohensional entanglement point. The critical strain for craze initiation and craze stability depended on physical ageing of the samples. The relationships between physical ageing and crazing were interpreted initially.
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