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25 May 2010, Volume 26 Issue 3

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Content of Chemical Research in Chinese Universities Vol.26 No.3(2010)

2010, 26(3):  0. 

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Articles

Synthesis and Structure Description of a New Tetradecaborate [H₃N(CH₂)₂NH₃]₂[B₁₄O₂₀(OH)₆]

YANG Miao, ZHANG Zheng, DING Hong and LI Ji-yang*

2010, 26(3):  335-338. 

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A new tetradecaborate, [H₃N(CH₂)₂NH₃]₂[B₁₄O₂₀(OH)₆](1), was synthesized by a boric acid ‘flux’ method, and characterized by X-ray powder diffraction, ICP, IR, TGA and DTA analyses. Single-crystal X-ray diffraction analysis showed that it crystallized in the monoclinic space group P1(No.2) with a=0.85092(10) nm, b=0.88678(11) nm, c=1.00724(13) nm, α=95.099(2)°, β=96.950(2)°, γ=116.845(2)°, V=0.66425(14) nm³, Z=2, R₁=0.0625[I>2σ(I)], and wR₂=0.1172(all data). The molecule structure of compound 1 comprises the isolated polyanion clusters [B₁₄O₂₀(OH)₆]^4– and diprotonated ethylenediamine molecules. Each polyanion cluster contains an 8-ring enclosed by six B₃O₃ 3-ring units. Adjacent clusters are further connected with each other through strong hydrogen-bonding interactions of N(O)―H···O to form a three dimensional(3D) supramolecular structure with 2D pseudo channels along the [010] and [001] directions. The diprotonated ethylenediamine molecules located in the channels interact with the host through extensive hydrogen-bonds. Compound 1 presents few example containing isolated polyborate anions synthesized by a boric acid ‘flux’ method.

Synthesis of Octylmethoxycinamate-silica Core-shell Nanoparticles with Self-templating Method

ZHANG Qing, LI Rui, ZHAI Yong-ai, LIU Feng-qi and GAO Ge*

2010, 26(3):  339-343. 

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A self-templating method was employed to synthesize core-shell nanoparticles with octylmethoxycinamate(OMC), a well-known organic UV absorber, as core and nanosilica particles as shell. The characteristic of this method is that the whole process requires neither surface treatment for nanosilica particles nor additional surfactant or stabilizer, and all the reactions could be finished in one-pot, which exempts removing template and reduces reaction steps compared to the conventional process. The morphology, structure, particle size distribution, chemical composition and optical property of OMC-SiO₂ nanoparticles were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), dynamic light scattering(DLS), FTIR spectrometry and UV absorption spectrometry, respectively. Experiment results indicate that the resulting OMC-SiO₂ nanoparticles were perfectly spherical with smooth particle surfaces, and had clear core-shell structures. The particle size could be tuned by alte- ring reaction conditions. In addition, the mechanism of the self-templating method for forming core-shell nanoparticles was discussed.

Structure and Magnetic Properties of FeCo/Al₂O₃ Nanocomposites

LI Hai-bo*, XU Shi-chong, LIU Mei, FENG Ming and YIN Ji-zhe

2010, 26(3):  344-347. 

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The soft magnetic nanocomposites with equiatomic FeCo particles dispersed in Al₂O₃ matrix were synthesized via a sol-gel technique combined with H₂ reduction method. The samples were characterized by X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The FeCo nanoparticles in all the samples have the typical bcc structure. With the decreasing of Al₂O₃ content, the mean grain size of FeCo in the nanocomposites and the saturation magnetization of the samples increase, while the coercivity of samples increases firstly and then decreases due to different magnetic mechanisms.

Synthesis and Characteristics of Fe₃C Nanoparticles Embedded in Amorphous Carbon Matrix

YANG Kai-yu, XU Wei, ZHANG Yu, ZHENG Wei-tao and WANG Xin*

2010, 26(3):  348-351. 

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We proposed a new way to synthesize a nanocomposite consisted of cementite Fe₃C nanoparticles and amorphous carbon by radio frequency plasma-enhanced chemical vapor deposition. Transmission electron microscope images show the existence of nanometric dark grains(Fe₃C) embedded in a light matrix(amorphous carbon) in the samples. X-ray photoelectron spectroscopy experiment exhibit that the chemical bonding state in the films corresponded to sp³/sp² amorphous carbon, sp³ C―N(287.3 eV) and C_1s in Fe₃C(283.5 eV). With increasing deposition time, the ratio of amorphous carbon increased. The magnetic measurements show that the value of in-plane coercivity increased with increasing carbon matrix concentration(from about 6.56×10³ A/m for film without carbon structures to approximately 2.77×10⁴ and 5.81×10⁴ A/m for nanocomposite films at room temperature and 10 K, respectively). The values of saturation magnetization for the synthesized nanocomposites were lower than that of the bulk Fe₃C(140 Am²/kg).

Synthesis of Small-sized Coesite Under Lower Pressure

WANG De-jun, LIU Xiao-mei*, ZHU Cheng-jun, YAN Duan-ting, LIU Fu-lin, ...

2010, 26(3):  352-354. 

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With the help of high-energy mechanical milling and α-SiO₂ as the initial material, we investigated the synthesis of coesite at a high temperature and high pressure under the condition of adding a certain amount of hard Fe filling. The synthetic samples were measured by XRD and Raman spectroscopy. The results show that a small amount of small-sized coesite can be obtained under 2.5 GPa and 973 K.

Preparation of Spherical Silica-supported Biosorbent for Copper Ions Removal in Wastewater Based on Sol-gel Reaction and Simple Treatment with Sodium Hydroxide

ZHENG Li*, JIANG Feng-hua, DONG Ping-jun, ZHUANG Qian-fen and LI Feng*

2010, 26(3):  355-359. 

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A new and effective strategy was proposed for preparing new organic-inorganic composite biosorbent with spherical silica as supporting core and chitosan(CS)-based hybrid layer as shell based on sol-gel reaction and simple treatment with sodium hydroxide(NaOH). The coating layer was covalently bound on the supporting silica through polysaccharide incorporated sol-gel process starting from CS and inorganic precursor γ-glycidoxypropyl- trimethoxysiloxane(GPTMS). GPTMS had epoxide groups and cross-linked amine groups of CS to avoid its acidic solubilization. The composite biosorbent had coarse surface due to the wet phase-inversion by treating in NaOH solution. The prepared biosorbent could be used in treating electric plating wastewater.

Spectrofluorometry of Ions and Small Molecules Based on Conformational Changes of Specific Oligonucleotides with o-Phthalaldehyde-β-mercaptoethanol

LIAO Qie-gen, WANG Jian, LONG Yun-fei and LI Yuan-fang*

2010, 26(3):  360-365. 

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Specific oligonucleotides such as telomere DNA and aptamer often undergo conformational changes upon ligand binding. Composite reagent composed of o-phthalaldehyde and β-mercaptoethanol(OPAME) has been extensively applied to fluorescent detection of amino compounds based on the reaction of primary amino-group, herein we proposed a general spectrofluorometry for ions and small molecules due to conformational changes upon ligand binding taking K⁺ and ATP as examples. In a borate controlled buffer medium, telomere DNA could react with OPAME, giving a thio-subtituted isoindole compound with strong fluorescence emission at 455 nm when excited at 340 nm. It was found that however, the fluorescence emission was greatly reduced in the presence of K⁺ since the formation of the quadruplex structure inhibits the reaction activity of amino-groups of telomere DNA. In order to testify the general application of OPAME reagent based on the conformational change of oligonucleotides, we further proposed a sensitive method of ATP based on its highly selective interaction with ATP-aptamer. The above mentioned applications show that the spectrofluorometry with the aid of OPAME reagent is simple, label free that is expected to be potentially general for DNA conformational change-based target detection.

Resonance Light Scattering Method for Determination of Amikacin with Potassium Ferrioxalate as a Probe

HU Xiao-li*, AN Lan-xiang, LIU Shao-pu, LIU Zhong-fang and LI Cui-xia

2010, 26(3):  366-370. 

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In a weak acid medium, potassium ferrioxalate(PF) can react with some aminoglycoside(AGs) antibiotics, such as amikacin(AMK), kanamycin(KANA), tobramycin(TOB) and gentamicin(GEN), to form ion-association complexes. It results in the enhancement of resonance light scattering(RLS) in different degrees. The maximum scattering peaks are all located at 345 nm. Among them, the relative scattering intensity(ΔI_RLS) of AMK system is much higher than that of KANA, TOB or GEN. Therefore the method is more propitious to the determination of trace amounts of AMK. The optimum reaction conditions, influencing factors, and the relationship between scattering intensity and concentration of antibiotics were investigated by means of the proposed method. The enhancement of RLS signals is directly proportional to the concentration of antibiotics in a certain range of concentration. A new resonance light scattering method for the determination of AMK and other aminoglycoside antibiotics with [Fe(C₂O₄)₃]^3– as a probe is thus established based on it. The method exhibits high sensitivity and good selectivity. The detection limit(3σ) for AMK is 1.8 ng/mL. The method can be applied to the determination of AMK in clinical serum samples. The reaction mechanism and the reasons for RLS enhancement are discussed in this paper.

Electrochemical Study of Lincomycin on Au-PtNPs/nanoPAN/Chitosan Nanocomposite Membrane and Its Determination in Injections

WANG Xue-liang, YANG Tao and JIAO Kui*

2010, 26(3):  371-375. 

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The Au-Pt alloy nanoparticles(Au-PtNPs) were electrochemically deposited on the surface of polyaniline nanotube(nanoPAN) and chitosan(CS) modified glassy carbon electrode(GCE). The electrochemical behavior of lincomycin at Au-PtNPs/nanoPAN/CS modified GCE was investigated by cyclic voltammetry, linear sweep voltammetry and chronocoulometry. Cyclic voltammetric experiments show that lincomycin at the nanocomposite membrane modified electrode exhibited a pair of quasi-reversible redox peaks in pH=6.0 PBS. The membrane could accelerate the electron transfer of lincomycin on the electrode and significantly enhance the peak current. In a range of 3.0―100.0 mg/L, the reductive peak current of lincomycin at 0.42 V was linearly related to its concentration and the linear regression equation was ip,c=0.2703ρ–0.0042(ip,c: μA; ρ: mg/L; r=0.998, n=7) with a detection limit of 1.0 mg/L(S/N =3). Compared with other methods, this method exhibited many advantages such as high sensitivity, selectivity, wide linear range and low detection limit. The method was used to determine the content of lincomycin in injections commercially available with satisfactory results. Some electrochemical parameters involved in the redox reaction of lincomycin, such as parameter of kinetic nα, standard rate constant ks and the number of H+, were also calculated.

Determination of Amino Acids by Ru(bpy)₃²⁺ Cathodic Electrochemiluminescence with High Sensitivity

ZHOU Xiao-guang, YUAN Bai-qing, ZHANG Lei, LIU Yang, HAN Dong-xue and YOU Yang

2010, 26(3):  376-379. 

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The unique cathodic electrochemiluminescence(ECL) emission of Ru(bpy)₃2+(bpy=2,2′-bipyridine) was observed via Nafion film at Au electrode[Au/Nafion/Ru(bpy)₃²⁺] at about 0.20 V(vs. Ag/AgCl) and applied to the determination of several amino acids without prior derivatization with high sensitivity. The cathodic electrochemiluminescence(ECL) exhibits the detection limits and linear ranges of several amino acids comparable to or better than those of capillary electrophoresis with conventional ECL detection method(at 1.10—1.20 V vs. Ag/AgCl) based on precolumn derivatization. The results suggest that the cathodic ECL is promising for the detection of amino acids in bioanalysis.

Synthesis, Crystal Structure and Insecticidal Activities of Novel Neonicotinoid Derivatives

ZHAO Yu, WANG Gang, LI Yong-qiang, WANG Su-hua and LI Zheng-ming*

2010, 26(3):  380-383. 

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Ten new N-oxalyl derivatives of neonicotinoid compound were designed and synthesized. Their structures were confirmed by ¹H NMR spectra, elemental analysis and X-ray diffraction. The preliminary insecticidal activities of the new compounds were evaluated. The results of bioassays indicate that the title compounds exhibit moderate insecticidal activities. Surprisingly, the insecticidal activity of compound 7b against bean aphids at 200 mg/kg is 100%, which is comparable to that of the commercialized imidacloprid.

BrΦnsted Acidic Ionic Liquids: Novel Efficient, Cost-effective and Reusable Solvent-catalysts for Ritter Reaction

JIANG Feng, LIN Ying-jie*, DUAN Hai-feng*, LI Zong-han, CAO Jun-gang, ...

2010, 26(3):  384-388. 

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Several BrΦnsted acidic ionic liquids(ILs) were synthesized and used as dual solvent-catalysts for the Ritter reaction of benzonitrile with tert-butanol. In particular, IL11([NSPTEA][OTF]) showed excellent catalytic acti- vity for the Ritter reaction. In the presence of IL11, various nitriles and tertiary alcohols as well as secondary alcohols were converted smoothly to the corresponding amides in good to excellent yields. In addition, this cost-effective ionic liquid [NSPTEA][OTF] was easily separated from the reaction mixture by extraction with a small amount of water, and was recycled five times without any significant loss in activity.

Solvent- and Catalyst-free Synthesis and Antifungal Activities of α-Aminophosphonate Containing Cyclopropane Moiety

PAN Li, LIU Xing-hai, SHI Yan-xia, WANG Bao-lei, WANG Su-hua, LI Bao-ju*, ...

2010, 26(3):  389-393. 

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Nine new α-aminophosphonate derivatives containing cyclopropane moiety have been synthesized via conventional and microwave irradiation methods under solvent- and catalyst-free condition. The structures of the title compounds have been confirmed by ¹H NMR, ³¹P NMR, FTIR, EI-MS and FTICR-MS. Their antifungal activities were evaluated in vivo and some of the compounds were found to exhibit excellent antifungal activities against Corynespora cassiicola, Pseudomonas syringae pv. Lachrymans, Pseudoperonospora cubensis and Sclerotinia sclerotiorum.

Simple and Mild Syntheses of Optically Active 2-(N,N-Dialkylamino)oxazolines

JIA Xu-dong, DUAN Hai-feng*, LIN Ying-jie*, CAO Jun-gang, LIANG Da-peng, ...

2010, 26(3):  394-397. 

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Chloroamidinium salts and α-amino alcohols derived from commercially available tetraalkyl ureas and α-amino acids, respectively, can be used for the syntheses of optically active 2-(N,N-dialkylamino)oxazolines in moderate to excellent yields without any catalyst. It is a simple and mild method for the syntheses of optically active oxazolines

Discovery of Fuchsone Derivatives as Novel Nonpeptide Inhibitor of Caspase-3

ZHANG Jin-liang, LIU Sen, GAO Chao-hui, CHEN Xiao-song, GUO Yang-hong, ...

2010, 26(3):  398-401. 

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Many degenerative diseases caused by uncontrolled cell death can be intervened pharmaceutically through inhibiting caspase-3 activity that leads to cell apoptosis. Here is presented the discovery of rosolic acid and phenolphthalein methyl ester, which both belong to fuchsone derivatives, as novel and potent nonpeptide inhibitors of caspase-3. They show high inhibitory potency against caspase-3 in vitro(IC₅₀=0.28 and 0.13 μmol/L). Molecular modeling study provided further an insight into the interaction of phenolphthalein methyl ester with activated caspase-3. The structures of the present small-molecule caspase-3 inhibitors are different from the structures of known caspase-3 inhibitors, so the inhibitors were likely to provide some information for the discovery of anti-caspase-3 inhibitors.

Synthesis and Spectral Characterization of Novel Sulfhydryl-reactive Benzimidazole Fluorescent Probes

LEI Ying-jie*, OUYANG Jie*, ZHANG You-lai and DING Mei

2010, 26(3):  402-405. 

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Three sulfhydryl-reactive fluorescent probes, which contain 2-(1H-benzoimidazol-2-yl)-phenol and maleimide group, were synthesized and their structures were characterized by IR and ¹H NMR. Their photo-physical properties and the specificity to sulfhydryl group in the 2-mercapto-ethanol as well as the L-cysteine adducts were indicated by fluorescence intensity. Preliminary tests revealed that the probes could react selectively with the cysteine molecules, suggesting that these probes might be generally useful in biomedical researches.

Altered Taurine Release in Hypothalamus of Aquaporin-4 Knockout Mice

ZHANG Hong-guo, XIAO Ying-hong, YANG Long-fei, SU Wei-heng, GUAN Xin-gang, ...

2010, 26(3):  406-408. 

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Taurine is concentrated in glial cells in the hypothalamus and released in an osmo-dependent manner through volume-sensitive anion channels. Released taurine acts on glycine receptors on vasopressin neurons to control vasopressin secretion. Water channel AQP4 is abundant in astrocytes in osmosensory areas such as the supraoptic nucleus of hypothalamus. An HPLC-based method was established to quantify taurine release from isolated hypothalamus tissues in wildtype and AQP4 knockout mice. Under the basal condition, there was no difference in taurine release from AQP4^+/+ and AQP4^-/- hypothalamuses. Taurine release from AQP4^-/- hypothalamus under hypoosmotic stimulation was significantly lower than that from AQP4^+/+ mice. AQP4 expression in the glial cells of the hypothalamus may play an important role in osmoregulation of taurine release and subsequent vasopressin secretion.

Akt Gene Therapy Enhances Angiogenesis in Ischemic Hind Limb

HUO Xin, ZHANG Qiang* and LIU Ying

2010, 26(3):  409-414. 

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Both bone marrow-derived mesenchymal stem cells(MSCs) therapy and gene therapy have been applied to animal studies and clinical trials. The goal of this study was to compare the effects of three types of MSCs transplantation. In the first part of the study, MSCs were transduced with the pEGFP-C1 and transfected with the pEGFP-C1/Akt in a model of bilateral hind limb ischemia in rats. Following gene transduction, the production of Akt and VEGF protein was more in the culture media of GFP-Akt/MSCs group than that in those of the GFP/MSCs group. In the second part of the study, Sprague-Dawley rats(n=10/group) underwent surgery to create bilateral hind limb ischemia and were randomized into two groups consisting of a GFP/Akt-MSCs group(MSCs suspension, 1×10⁷ MSCs/100 μL transfected pEGFP-C1/Akt) and a GFP-MSCs group(MSCs suspension, 1×10⁷ MSCs/100 μL). These PEGFP-C1/Akt and PEGFP-C1 transfected MSCs suspensions were slowly infused into the adductor muscles of the rat’s left hind limb, while the rat’s right hind limb in the control group received an equal volume of PBS. Endpoints includes angiographic analysis, evaluation of capillary density, immunohistochemistry for von Willebrand factor (vWF), immunodetection of Akt and VEGF protein, RT-PCR of VEGF and Akt mRNA levels in vitro and in vivo. Our data indicate that the tissue perfusion can improve capillary density and the mature of vasculature in the GFP-Akt/MSCs group compared to that in the GFP-MSCs group or control group in the rat model of bilateral hind limb ischemia. Transplantation of MSCs transfected with Akt gene may become the future therapy for hind limb ischemia.

Metabolites of Marine Fungus Aspergillus sp. Collected from Soft Coral Sarcophyton tortuosum

LI Hou-jin, CAI Yong-tong, CHEN Yun-yun, LAM Chi-keung and LAN Wen-jian*

2010, 26(3):  415-419. 

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Fungus Aspergillus sp., which was isolated from soft coral Sarcophyton tortuosum, was cultured in the GPY medium containing glucose 10 g/L, peptone 5 g/L, yeast extract 2 g/L, sea water 1 L, at pH=7.5. Four compounds, 3,6-diisobutyl-2(1H)-pyrazinone(1), 3-isobutyl-6-(1-hydroxy-2-methylpropyl)-2(1H)-pyrazinone(2), 3-methoxy-4-methyl-2,4-dien-pentanoic acid(3) and penicillic acid(4) were obtained from the AcOEt extract of the culture broth. Their structures were elucidated mainly based on the NMR, HR-EI-MS and X-ray single crystal diffraction experimental data. Compound 3 is a new compound. Compound 1 was previously proposed to be the tautomer of flavacol(3,6-diisobutylpyrazin-2-ol, 5). However, the evaluation of the NMR and X-ray single crystal diffraction experimental data permitted us to propose that compound 1 existed as amide form instead of tautomers. Compound 1 is stable both in solution and crystal due to strong intermolecular hydrogen bonds. Incidentally supplying anthracenone to the GPY medium with a dose of 100 mg/L, the yield of penicillic acid(4) in the culture broth of the strain Aspergillus sp. was increased dramatically from 6 mg/L to 57 mg/L.

Expression of Human Interferon α 2b Gene in Ginseng Cells

REN Qi, WANG Chun-yi, SONG Zhi-ming, LIU Dan, YU Hai-peng and SHENG Jun*

2010, 26(3):  420-426. 

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The human interferon α 2b(hIFN-α2b) gene was cloned into binary vector pBI121 to obtain plant expression vector pBIFN. The recombinant plasmid pBIFN was transferred into Agrobacterium tumefaciens strain LBA4404. Then the hIFN-α2b gene was introduced into ginseng callus cells via Agrobacterium-mediated transformation and the ginseng cell line carrying hIFN-α2b gene was selected on G418-containing medium. The presence of target gene in transformed cells was confirmed by PCR and RT-PCR. The results indicate that hIFN-α2b gene has been integrated into the ginseng cells’ genome, with transcription products. hIFN-α2b expressed by the transgenic ginseng cells was detected by Western blot. It was shown that a specific protein band at 19000 could be observed. Cytopathic effect(CPE) inhibition assay using the WISH-VSV system shows that the mean antiviral activity of expressed hIFN-α2b was 6.0×10⁴ IU/mL.

Easy-to-use Method to Display Arabidopsis Rubisco Interacting Proteins

SUN Li-wen, LI Jian-hua, LI Shan-yu* and XI Jing-hui*

2010, 26(3):  427-430. 

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Affinity-mediated protein separation is an integral part of proteomics, the most outstanding of which is immunoproteomics. However, in the immunoprecipitate system overwhelming Ab and Ag conceal Ag interacting proteins as the research targets, which is the rate-limiting step in the progress of comparative proteomic analyses. We presented a convenient and accurate method to tackle this problem. 1 mol/L NaCl elution buffer was applied to the complex Rubisco immunoprecipitate of Arabidopsis, the weakest force involved in the system was selectively broken up, resulting in the enrichment of Rubisco interacting proteins accessible for further comparative protein gel profile. The easy-to-use method sheds light on a narrow-down strategy supplement for comparative immunoproteomics.

Kinetics and Thermodynamics of Adsorption of VB12 onto Mesoporous Carbon Coated with PMMA

GUO Zhuo*, ZHANG Wei-wei, DING Xiang-ping, LI Sha and MA Lei

2010, 26(3):  431-435. 

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Ordered mesoporous carbons CMK-3, CMK-1 coated with poly(methyl methacrylate)(PMMA)(CMK-3- PMMA and CMK-1-PMMA) and pristine mesoporous carbons CMK-3, CMK-1 were employed to adsorb vitamin B12(VB12) from water solution. Adsorption isotherm and kinetics of adsorption were investigated via batch experiments. It was found that the adsorption capacity of VB12 at 30, 40 and 50 °C can reach 688.2, 572.4 and 428.7 mg/g, respectively. The adsorption isotherm can be described by Langmuir model. The pseudo first- and second-order kinetic models were employed to fit the dynamic adsorption. It was found that the dynamic adsorption follows the pseudo second-order model. The thermodynamic equilibrium coefficients obtained at different temperatures were used to evaluate the thermodynamic constants ΔG⁰, ΔH⁰ and ΔS⁰. The negative value of Gibbs free energy, ΔG⁰ indicates that the adsorption occurred via a spontaneous process. The increase in the value of –ΔG⁰ with increasing temperature indicates that higher temperatures were favourable to the sorption process. The enthalpy values of ΔH⁰>40 kJ/mol(66.36 kJ/mol and 56.43 kJ/mol) for CMK-3-PMMA and CMK-1-PMMA confirm that chemisorption were involved in the adsorption process. This is consistent with the IR spectra and is another evidence for the formation of hydrogen bond between PMMA in the pore of CMK-3 and VB12.

Estimation of Critical Temperature of Thermal Explosion for Trinitromethyl Explosives by Non-isothermal DSC

ZHANG Hai* HU Rong-zu*, ZHAO Feng-qi, GAO Hong-xu and MA Hai-xia

2010, 26(3):  436-442. 

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Two general expressions and their six derived formulae for estimating the critical temperature(T_b) of thermal explosion for energetic materials(EMs) were derived from the Semenov’s thermal explosion theory and eight non-isothermal kinetic equations via reasonable hypothesis. We can easily obtain the values of the initial temperature(T_0i) at which DSC curve deviates from the baseline of the non-isothermal DSC curve of EMs, the onset temperature(T_ei), the exothermic decomposition reaction kinetic parameters and the values of T₀₀ and T_e0 from the equation T_{0i or ei}=T_{00 or e0}+α₁β_i+α₂β_i²+···+α_L–2β_i^L–2, i=1, 2, ···, L and then calculate the values of T_b by means of the six derived formulae. The results obtained with the six derived calculating methods for six trinitromethyl explosives: bis(2,2,2- trinitroethyl-N-nitro) ethylene diamine(BTNEDA), 2,2,2-trinitroethyl-4,4,4-trinitrobutyrate(TNETB), bis(2,2,2-   trinitroethyl) formal(BNTF), bis(2,2,2-trinitroethyl-nitramine)(BTNNA), 2,2,2-trinitroethyl-2,2,2-trinitroethyl-N-  nitroamino acetate(TNTNNA) and tetrakis [2,2,2-trinitroethyl] orthoester(TTNOE) agree well with each other.

Electrochemical Quartz Crystal Microbalance(EQCM) Characterization of Electrodeposition and Catalytic Activity of Pd-based Electrocatalysts for Ethanol Oxidation

KE Xi, DENG Lu-lu, SHEN Pei-kang* and CUI Guo-feng*

2010, 26(3):  443-448. 

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Pd was electrochemically deposited on gold-coated quartz crystals at nanogram-level. The coulombic efficiency and initial nucleation and growth mechanism of potentiostatic Pd deposition were investigated via in situ electrochemical quartz crystal microbalance(EQCM). The coulombic efficiencies are 84%, 93% and 95% for Pd deposition at 0.3, 0.2 and 0.1 V(vs. SCE), respectively. The results of chronoamperometric measurements show that the Pd deposition proceeded by an instantaneous nucleation(at 0.3 V) or progressive nucleation(at 0.2 and 0.1 V) in a three-dimensional(3D) growth mode. The catalytic activity of Pd-based electrocatalyst for ethanol oxidation was characterized in an alkaline solution. It was found that the highest mass activity for ethanol oxidation on Pd-based electrocatalyst is 1.8×10⁴ A/(g Pd) deposited at 0.3 V for 5 s.

Synthesis of Monoclinic Li_0.33MnO₂ and Its Electrochemical Properties in Different Potential Windows

CHEN Hong, WEI Ying-jin, JIANG Tao, CHEN Gang and WANG Chun-zhong*

2010, 26(3):  449-452. 

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Li_0.33MnO₂ cathode material was synthesized by solid state reaction. The material showed a small coherent domain size about 10 nm determined by X-ray diffraction and transmission electron microscopy. The electrochemical properties of the material were studied in different potential windows of 3.5―2.0 V and 4.3―2.0 V. An irreversible transformation to spinel phase was observed in the initial several cycles, which was more prominent on cycling at 4.3―2.0 V. Electrochemical impedance spectroscopy showed that the Li⁺ diffusion coefficient of the material was about 2×10^-9 cm²/s. Li_0.33MnO₂ showed a reversible discharge capacity of 140 and 200 mA·h/g in the potential windows of 3.5―2.0 V and 4.3―2.0 V, respectively. But the capacity retention at 4.3―2.0 V was poor due to the thicker spinel layer formed on the material surface.

Evolution of Gold Species in an Au/CeO₂ Catalyst and Its Impact on Activity for CO Oxidation

SUN Yong-an*, SHEN Yue-nian, JIA Mei-lin and GUO Jin-ling

2010, 26(3):  453-459. 

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An Au/ceria(0.44%, mass fraction) catalyst containing gold ions was prepared by a modified deposition precipitation method, and the evolution of gold ions in the catalyst and its influence on the catalysis of CO oxidation were investigated. It was found that the as-prepared catalyst containing gold ions with high valence could fully  oxidize CO at –10 °C initially but was deactivated gradually at low temperatures during the reaction with CO or treatment by unpurified air. The deactivation of the catalyst during CO oxidation or treatment of it by unpurified air was independent and progressive at low temperatures while the activity of the catalyst at relatively high temperatures was maintained well. During the reaction with CO or treatment by unpurified air, the XPS results indicate that gold species evolved from high valence to low valence and the diffuse reflectance UV-Vis spectra show that high valence gold was reduced to charged gold clusters, gold clusters grew to small gold crystals and small gold crystals grew to large gold particles. Accordingly, the high valence gold corresponded to the activity at low temperatures and the metallic gold was active and relatively stable at high temperatures. The turnover frequencies(TOF) of the catalysts treated by different methods at 273 K decreased with the evolution of gold species from high valence to low valence, no maximum of TOF was observed although gold particles in the catalyst attained to about 2―3 nm during the treatment. An Au/ceria catalyst with a gold load of 0.87% (mass fraction) maintained a good activity for CO oxidation within 18 h at room temperature. The catalysts were characterized via transmitted electronic microscopy(TEM), inductively coupled plasma optical emission spectrometry(ICP-OES), X-ray diffraction(XRD) and BET specific surface area and UV-Vis DRS as well.

Electronic Structure and Catalysis on (001) Polar Surface of Cubic Zirconia

SHEN Pei-jun*, DING Wei-zhong, ZHOU Yu-ding and HUANG Shao-qing

2010, 26(3):  460-464. 

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The electronic structure of (001) polar surface of cubic zirconia was studied by GGA(WC) approximation. We found the cubic lattice near (001) surface showed an intensive tendency to transfer to tetragonal lattice. The metallic state appeared on both the terminations. For O-termination, some O_2p states were vacated and hole carriers concentrated on surface oxygen-ions. For Zr-termination, some Zr_4d states became partial occupied for the loss of O_2p states. We observed the hole states were mainly localized at the corresponding ions on surface for both the terminations, while the charge states on Zr-termination were dispersed on surface.

Electronic Effect of Carbon Support on Pt Catalyst Supported on Graphite Intercalation Compound

WEI Ang, WANG Qing-jing, ZHAO Xiao-hui and ZHANG Shu-yong*

2010, 26(3):  465-471. 

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Graphite intercalation compounds(GIC) were tested as an experimental model for studying the electronic effect of carbon support on the catalytic activity and poisoning tolerance of Pt catalyst for direct methanol fuel cells. The GIC samples with different intercalation degrees were prepared by electrolyzing graphite flake in H₂SO₄ for varying the periods of time. The GIC-supported Pt catalyst was deposited electrochemically. The catalytic activity and poisoning tolerance of the GIC-supported Pt catalysts were evaluated. It was found that GIC with sulfate anion as intercalate was able to catalyze methanol electrooxidation, which could be related to the positive charges generated on the graphite layer upon intercalation. As intercalation degree increased, the catalytic activity of the GIC-supported Pt catalyst decreased while the poisoning tolerance improved. This suggests that electron donation from support to catalyst had great effect on both catalytic activity and poisoning tolerance of Pt catalyst. And intercalation can be adopted as another important way to make modification on carboneous catalyst support.

First-Principle Studies on Adsorption of Cu⁺ and Hydrated Cu⁺ Cations on Clean Si(111) Surface

CHENG Feng-ming, SHENG Yong-li, LI Meng-hua, LIU Yong-jun*, YU Zhang-yu, ...

2010, 26(3):  472-478. 

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To study the adsorption behavior of Cu⁺ in aqueous solution on semiconductor surface, the interactions of Cu⁺ and hydrated Cu⁺ cations with the clean Si(111) surface were investigated via hybrid density functional theory(B3LYP) and MΦller-Plesset second-order perturbation(MP2) method. The clean Si(111) surface was described with cluster models(Si₁₄H₁₇, Si₁₆H₂₀ and Si₂₂H₂₁) and a four-silicon layer slab under periodic boundary conditions. Calculation results indicate that the bonding nature of adsorption of Cu⁺ on Si surface can be viewed as partial covalent as well as ionic bonding. The binding energies between hydrated Cu⁺ cations and Si(111) surface are large, suggesting a strong interaction between them. The coordination number of Cu⁺(H₂O)_n on Si(111) surface was found to be 4. As the number of water molecules is larger than 5, water molecules form a hydrogen bond network. In aqueous solution, Cu⁺ cations will safely attach to the clean Si(111) surface.

Influence of Mixing Conditions on Morphologies and Properties of MMT/Epoxy Resin Composite Materials

LI Shi-wei, CUI Ji-wen, ZHAO Cheng-ji, FU Tie-zhu and NA Hui*

2010, 26(3):  479-482. 

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Montmorillonite(MMT) was directly modified with hexadecyl trimethyl ammonium bromide. The interlayer spacing of the organophilic montmorillonite(organo-MMT) corresponding to the d(001) plane peak was 2.21 nm. The influences of the content of organo-MMT and mixing conditions including mixing temperature and mixing time on the intercalation and exfoliation structures of MMT/epoxy resin composites were investigated by wide X-ray diffraction(WXRD). The X-ray patterns reveal that organo-MMT was intercalated by the epoxy resin during mixing process. Only under certain mixing conditions, could the exfoliation nanocomposites be formed. The mechanical and thermal properties of the composites were measured. The results indicate that the composites have better mechanical properties and higher T_g than those of the pristine epoxy resin.

Starch/Polycaprolactone Blends Compatibilized with Starch Modified Polyurethane

TAN Ying, WANG Pi-xin*, XU Kun, AN Hui-yong and DONG Li-song

2010, 26(3):  483-487. 

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Starch modified polyurethane(St-PCL) was synthesized via chemical modification of corn starch with hexamethylene diisocyanate terminated polycaprolactone. The obtained St-PCL with different grafting rates was used as compatibilizer of starch/polycaprolactone(St/PCL) blend. The structure of St-PCL was confirmed by FTIR, and the grafting rate could reach as high as 64%. In addition, a lower St-PCL amount can effectively improve the compatibi- lity of St/PCL blends. And the thermal, mechanical and hydrophobic properties of St/PCL blends could be tailored by the amount of St-PCL.

Quantitative ³¹P NMR Analysis of Lignocellulosic Materials in Ionic Liquids

SUN Hui*, XU Ying-kai* and XU Guo-zhi

2010, 26(3):  488-490. 

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In an effort to utilize NMR technique for the analysis of the structural components of wood and biomasses such as lignin, we made a comparative study of lignin contents of several types of lignocellulosic materials both before and after enzymatic hydrolyses. To this end, Eucalyptus Globulus, Norway spruce thermomechanical pulp(TMP) corn stover and Eucalyptus kraft pulp were ball-milled and treated with cellulase to prepare materials with high lignin contents. These materials were analyzed via ³¹P NMR in ionic liquids. The results show that the contents of various functional groups for the lignocellulosic materials after enzymatic hydrolyses are generally in agreement with those from their corresponding enzymatic mild acidolysis liginins(EMALs), indicating that ³¹P NMR analysis of lignocellulosic materials in ionic liquids is a promising method for quantitative characterization of lignocellulosic materials.

Crystallization Behavior and Mechanical Properties of Poly(vinylidene fluoride)/multi-walled Carbon Nanotube Nanocomposites

XU Yue, ZHENG Wei-tao, YU Wen-xue, HUA Li-gui, ZHANG Yu-jie and ZHAO Zhu-di*

2010, 26(3):  491-495. 

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Poly(vinylidene fluoride)(PVDF)/multi-walled carbon nanotube(MWCNT) nanocomposites were prepared by means of ultrasonic dispersion method. X-ray diffraction(XRD) results indicate that incorporating MWCNTs into PVDF caused the formation of β phase. A thermal annealing at 130 °C confirmed that the β phase was stable in the nanocomposites. Differential scanning calorimetry(DSC) results indicate that the melting temperature slightly  increased while the heat of fusion markedly decreased with increasing MWCNT content. The tensile strength and modulus of PVDF were improved by loading the MWCNTs. The scanning electron microscopy(SEM) observations showed that MWCNTs were uniformly dispersed in the PVDF matrix and an interfacial adhesion between MWCNT and PVDF was achieved, which was responsible for the enhancement in the tensile strength and modulus of PVDF.

Preparation and Characterization of Microcapsules for Self-healing Materials

LIAO Le-ping*, ZHANG Wei, ZHAO Yang and LI Wu-Jun

2010, 26(3):  496-500. 

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The urea-formaldehyde(UF) capsules filled with a healing agent, a mixture of epoxy resins(epoxy 711 and E-51) as core material, were produced by means of one step in-situ polymerization. The characteristics of these microcapsules were studied via scanning electron microscopy(SEM), particle size analysis, FTIR and DSC/TGA. The results show that the dispersed and integrated microcapsules of 5 μm in shell thickness were synthesized successfully. The capsules were produced with diameters ranging from 10 to 250 μm via controlling agitation rate. Young’s mo- dulus of the capsule was a little lower than those of the epoxy resins, but the microcapsules having such a shell thickness were robust enough to survive handling during manufacturing self-healing composites. When damage occurred in the epoxy matrix, the crack could rupture the microcapsule to make the repairing agent release.