Table of Content

10 October 2013, Volume 34 Issue 10

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Cover and Content of Chemical Journal of Chinese Universities Vol.34 No.10(2013)

2013, 34(10):  0-0. 

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Review

Poly(ethylene terephthalate)/Layered Double Hydroxide Nanocomposites

CAO Tian-Chi, CHEN Guang-Ming, GUO Cun-Yue

2013, 34(10):  2239-2246.  doi:10.7503/cjcu20130657

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Poly(ethylene terephthalate)/layered double hydroxide(PET/LDH) nanocomposites are novel polymer based nanocomposites with enhanced properties and wide application fields. Compared with neat PET, PET/LDH nanocomposites exhibit greatly enhanced mechanical properties, thermal stability, flame retardancy and UV-shielding ability. This review reports the recent research progress in PET/LDH nano-composites. First, the composition and structure, preparation and properties of LDHs were briefly introduced. Then, the recent progress of the preparation, structure characterization, crystallization behavior, thermal stability, flame retardancy and UV-shielding properties of the PET/LDH nanocomposites were reviewed. Finally, the prospect of the nanocomposites was briefly described.



Academic Contention

Fundamental Flaw of Marcus Theory

ZHU Xiao-Qing, YANG Jin-Dong

2013, 34(10):  2247-2253.  doi:10.7503/cjcu20130183

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Marcus theory is a theory originally developed by Rudolph A. Marcus in 1956 based on Libby's idea about electron transfer mechanism according to the two-sphere model with the help of the continuous medium theory and the electrostatic mechanics to describe the kinetics of the outer-sphere electron transfer reactions in solution, which states that the activation free energies of the outer-sphere electron transfer reactions have the quadratic relationship with the corresponding reaction free energy changes. Having been developed by Marcus and many other chemists for more than 50 years, Marcus theory has received extensive application in various fields. Meanwhile, the research object of Marcus theory has been extended from the outer-sphere electron transfer reactions to the inner-sphere electron transfer reactions, even more to the nucleus transfer reactions. Because the reaction coordinates of the transition state of the electron transfer reactions in Marcus inverted region go beyond the region between the initial state and the final state of the reactions in the same reaction coordinate system, which evidently does not obey the natural change logic, we have never accepted Marcus theory as a scientific theory, even though some experimental observations were reported by Miller and Closs as well as many other chemists to support Marcus inverted region. In order to dig out the origin of Marcus theory error, in this study we examined the following questions about the classical Marcus theory:(1) What are the prerequisites(or assumptions) of Marcus theory? (2) How do Marcus free energy parabolas for the reactant system and for the product system form? (3) What factors determine the feature of Marcus free energy parabolas? (4) How does the classical Marcus equation form? (5) What is the criterion of Marcus inverted region? After the examinations, the following conclusions can be made:(1) Marcus theory directly conflicts with the law of conservation of energy and has the error in principle; (2) Marcus inverted region is impossible; (3) the experimental observations for Marcus inverted region reported in the literatures are all spurious.



Article: Inorganic Chemistry

Preparation and Electromagnetic Properties of CoFe₂O₄ and Its Composites with Expanded Graphite

XU Feng, XIANG Chen, LI Liang-Chao, MAO Meng-Yi, ZHOU Yan, DING Yan, LI Juan-Bi

2013, 34(10):  2254-2261.  doi:10.7503/cjcu20130358

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CoFe₂O₄(CF) and the composites of CoFe₂O₄/expanded graphite(CF/EG) were prepared by ultrasound-co-precipitation method. The structures, morphologies, thermal stabilities, electrical and magnetic properties of the samples were characterized by modern measurement technology. The results indicated that the magnetic property of CF was influenced by precipitator type, sintering temperature, etc. CF/EG composites had excellent electrical conductivity and absorbing properties. The sample with 2.0 mm coating thickness, made by CF/EG composite with m(EG)/m(CF) of 0.8 and paraffin, showed a minimum reflection loss of-16.08 dB at 13.53 GHz and an available bandwidth of 6.6 GHz in the range of 10—18.0 GHz. The absorbing properties of the composites originated mainly from the conductance loss and dielectric loss of EG, the magnetic loss of CF, the interface relaxation effect and synergistic effect between the two components.



Contrast Study of the Oxygenation of Co(Ⅱ) Complexes with Different Bi-/Poly-dentate Ligands

WEN Hong-Mei, ZHANG Xu, LI Hui, YUE Fan, WANG Ji-De

2013, 34(10):  2262-2269.  doi:10.7503/cjcu20130354

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In this paper, the influences of the reversible oxygenation performances of Co(Ⅱ) complexes with different ligands have been investigated in aqueous solution at room temperature. Four types of bi-/polydentate ligands, such as α-amino acids(N/O type), α-amino alcohols(N/O type), polyamine(N/N type) and multi-carboxylic acids(O/O type), have been selected to conduct a comparative research, and the oxygenation performances have been determined via UV-Vis spectrophotometry and oxygen electrode. The results showed that the cobalt(Ⅱ) complexes of O/O type polydentate ligands had no oxygenation properties; the complexes of N/N type bidentate ligands were proved to have strong capability to uptake oxygen, while the oxygenation process was irreversible. Great differences of oxygenation performance between α-amino acids Co(Ⅱ) complexes and α-amino alcohols Co(Ⅱ) complexes have been found:α-amino acids Co(Ⅱ) complexes exhibited reversible oxygenation performance, however, the Co(Ⅱ) complexes of α-amino alcohols with one hydroxy group displayed no oxygenation, but the complexes of α-amino alcohols with two hydroxy groups could absorb oxygen weakly while the process was irreversible. Meanwhile the mechanism of reversible oxygenation performance of Co(Ⅱ) complexes that containing —OH and —COOH groups in N/O type bidentate ligand were analyzed and studied. It can be estimated that the group of α-amino acid is the basic coordination structure unit of the Co(Ⅱ) complexes which have the reversible oxygenation performance.



Self-orientation of Multiferroics BiFeO₃ Film Prepared by Chemical Solution Deposition Method

CHEN Rui, HUANG Ke-Ke, WU Xiao-Feng, SI Wen-Zhe, FENG Shou-Hua

2013, 34(10):  2270-2273.  doi:10.7503/cjcu20130311

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BiFeO₃(BFO) film was grown on ITO/glass substrate by chemical solution deposition method. Structure, surface morphology, valence, magnetic property and ferroelectricity of the BFO film were investigated by X-ray diffractometer, scanning electron microscope, X-ray photoelectron spectroscopy, magnetic property measurement system and ferroelectric tester. The results showed that the film growed along [101] crystal orientation and had a plat and smooth surface. The films presented ferromagnetic behavior, the magnetization easy axis is along [101]. The saturation polarization was about 51.3 μC/cm².



Preparations and Dehydriding Properties of AlH₃

LIU Hai-Zhen, WANG Xin-Hua, LIU Yong-An, YAN Mi

2013, 34(10):  2274-2278.  doi:10.7503/cjcu20130227

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AlH₃ is a promising hydrogen storage material due to its high hydrogen capacity(10%, mass fraction) and relatively low dehydriding temperature(100—200℃). However, the complicate synthesis procedure restricts the fundamental investigation and practical application of AlH₃. In this paper, with LiAlH₄, LiBH₄ and AlCl₃ as the raw materials, pure α-AlH₃ and γ-AlH₃ were prepared and their dehydriding properties were studied. The experimental results show that the hydrogen desorption capacity of the prepared AlH₃ reaches 8.3%—8.5%(mass fraction), and the dehydriding temperature ranges from 120℃ to 160℃. The peak dehydriding temperature of γ-AlH₃ is 8.2℃ lower than that of α-AlH₃. The activation energies of dehydriding reaction of α-AlH₃ and γ-AlH₃ are 94.6 kJ/mol and 86.3 kJ/mol, respectively. During heating procedure, α-AlH₃ directly decomposes and releases hydrogen, while γ-AlH₃ transforms to α-AlH₃ before decomposition.



Analytical Chemistry

Detection of Micro-metastatic Lymph Node in Thyroid Cancer by Fourier Transform Infrared Spectroscopy

LIU Ya-Qi, SANG Chang-Ye, XU Yi-Zhuang, XU Zhi, ZHOU Xiao-Si, LING Xiao-Feng

2013, 34(10):  2279-2283.  doi:10.7503/cjcu20130528

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Sixteen non-and micro-metastatic freshly removed lymph nodes were measured by Fourier transform infrared spectrometor(FTIR) equipped with attenuated total reflectance(ATR) probe. For each spectrum, 38 variables of 13 bands including peak positions, relative intensities and full width at half maximum(FWHM) were compared between the two groups. The results indicated that the FTIR spectra of micro-metastatic lymph nodes were significantly different from non-metastatic in the bands related to protein, lipid, carbohydrate and nucleic acid. The relative intensity ratios of I₃₂₈₀/I₁₄₆₀, I₁₆₄₀/I₁₄₆₀ that related to protein increased significantly; the FWHM of F₁₆₄₀ increased, on the contrary, F₁₅₄₆ decreased significantly. The relative intensity ratios of I₁₄₀₀/I₁₄₆₀ that related to lipid increased significantly. The relative intensity ratio of I₁₁₆₅/I₁₄₆₀ that related to carbohydrate decreased significantly. The relative intensity ratio of I₁₂₄₀/I₁₄₆₀ that related to nucleic acid increased significantly. FTIR spectroscopy could be a potential powerful approach formicro-metastatic lymph nodes detection during the operation of thyroid cancer.



End-point Detection of the Alcohol Adding Process in Alcohol Precipitation of Lonicerae Japonicae Based on Design Space and Process Analytical Technology

XU Bing, LUO Gan, LIN Zhao-Zhou, AI Lu, SHI Xin-Yuan, QIAO Yan-Jiang

2013, 34(10):  2284-2289.  doi:10.7503/cjcu20130523

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Under the guidance of the FDA's process analytical technology(PAT) initiative and the ICH's quality by design(QbD) principles, a new approach was applied for the end-point detection of the pharmaceutical process of Chinese medicine preparations. Generally, three steps were included in the proposed approach:(1) perform the NIR analysis for the batch process under normal operating conditions(NOCs), and collect the NIR spectra of different batches; (2) determine the desired end-points(DEPs) for every NOCs batch using the PCA based moving window relative standard deviation(PCA-MBRSD) method. Then, the QbD design space was defined, depending on these DEPs; (3) within the area specified by the design space, the multivariate statistical process control(MSPC) strategy was introduced, and the Hotelling T² and SPE control chart were established to monitor and detect the end-point of the manufacturing process. The above methods were tested on the end-point detection of the alcohol adding process of alcohol precipitation of Lonicerae Japonicae water extract. The results demonstrated that the sensitivity and accuracy of the proposed approach were satisfactory.



Molecularly Imprinted Electrochemical Sensor for 2, 4-Dichlorophenol Based on Composite Film of o-Aminothiophenol and Au Nanoparticles

ZHANG Jin, WANG Chao-Ying, LI Xiao-Ping, NIU Yan-Hui

2013, 34(10):  2296-2302.  doi:10.7503/cjcu20130483

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A novel molecularly imprinted electrochemical sensor for 2,4-dichlorophenol(2,4-DCP) detection was fabricated on the surface of gold electrode by self-assembly of o-aminothiophenol(oATP) and electropolymerization of oATP/Au nanoparticles in the presence of template molecule. The modification procedure was characterized via cyclic voltammetry and electrochemical impedance spectroscopy. In the presence of K₃Fe(CN)₆ as redox probe, the peak current of K₃Fe(CN)₆ decreased linearly with the increasing concentration of 2,4-DCP from 5.0×10^-8 to 1.2×10^-4 mol/L(R²=0.9964) with a detect limit of 1.5×10^-8 mol/L(S/N=3). Three chlorophenols possesing analogous structures, including 2,6-DCP, 2,4,6-trichlorophenol(2,4,6-TCP) and pentachlorophenol(PCP) were chosen to examine the specific recognition ability of the imprinted sensor. The results showed that MIP electrode had the highest current response toward 2,4-DCP. In addition, the feasibility of its practical applications has been demonstrated in the analysis of four water samples with the recoveries ranged from 95.2% to 109.3%.



Selective Detection of Pb²⁺ Using Poly(methylacrylic acid) Monolayer-protected Gold Nanoparticles

LI Jun-Bo, HAN Chen, ZHANG Shi-Jie, GUO Jin-Wu, ZHOU Hui-Yun

2013, 34(10):  2303-2307.  doi:10.7503/cjcu20130456

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In this work, the selective colorimetric detection of Pb²⁺ was studied using poly(methylacrylic acid) monolayer-protected gold nanoparticles(PMAA-@-GNPs). The GNPs with uniform size and distribution were firstly synthesized by the citrate reduction method. Then PMAA-@-GNPs were prepared by the strong binding of the GNPs and the thiol ends groups of the PMAA. The monolayer structure was proved by the dynamic light scattering, UV-visible spectra and transmission electron microscopy. In the presence of Pb²⁺, the color of the solution changed from wine red to purple and could be measured by visual inspection. TEM results demonstrated that the induced aggregation of GNPs by Pb²⁺ crosslinking carboxyl groups. The selectivity of Pb²⁺ detection has also been investigated by comparing the color changes of solutions with other metal ions, including Hg²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Na⁺, Ni²⁺, Fe³⁺, Cd²⁺, K⁺ and Fe²⁺. After treated by EDTA, the aggregated PMMA-@-GNPs could be renewable and recycled detecting Pb²⁺.



Organic Chemistry

Synthesis and Photodynamic Antitumor Activity of New Metalloporphyrin-Ara-C Compounds

HE Jie, LIU Wen-Hong, HE Li-Min, CHEN Li-Yuan

2013, 34(10):  2308-2312.  doi:10.7503/cjcu20130124

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Photodynamic therapy(PDT) is a promising modality with minimally invasive approach to the clinical treatment of oncology generally based on photosensitizers, as they can utilize the administration and selective accumulation in cancer tissues to cause tissue injury and cell death by exposure to suitable visible light. Porphyrins can be used as efficient photosensitizers with their unique characteristic π-system and coordinating metals. To develop new porphyrin photosensitizers of PDT, porphyrin-Ara-C compound was designed and synthesized, then four metalloporphyrin-Ara-C compounds were synthesized through metal insertion reaction. Their structures were characterized by ¹H NMR, IR, UV-Vis and MS. The photodynamic antitumor activity experimental results showed that the killing rate of PDT with 25μmol/L ZnAHP reacted for 30 min to MCF-7 cell could reach (45.86±8.20)%.



Synthesis of Natural Products Combretastatin A-1 and Combretastatin B-1

LÜ Ze-Liang, HUANG Tong-Kun, NI Qing-Chun, XIAO Chun-Fen, ZOU Yong

2013, 34(10):  2313-2318.  doi:10.7503/cjcu20130155

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A new synthetic protocol based on Perkin reaction for access to the antivascular and antitumor natural products combretastatin A-1(CA1) and combretastatin B-1(CB1) was developed. Starting from 2,3,4-trihydroxybenzaldehyde(1), 2,3-dihydroxy-4-methoxybenzaldehyde(2) could be readily obtained via monomethylation, subsequent protection reaction was performed to afford the catechol protected intermediate 2,3-diisopropyloxy-4-methoxybenzylaldehyde(3). Perkin condensation between compound 3 and 3,4,5-trimethoxyphenylacetic acid(4) gave E-2-(3,4,5-trimethoxyphenyl)-3-(2',3'-diisopropyloxy-4'-methoxybenzyl)acrylic acid(E-5) which underwent a decarboxylation reaction to afford Z-2',3'-diiso-propyloxy-3,4,4',5-tetramethoxystilbene(6), and CA1 could then be obtained by deprotection reaction. In addition, E-2-(3,4,5-trimethoxyphenyl)-3-(2',3'-dihydroxy-4'-methoxybenzyl)acrylic acid(7) could be obtained by deprotection reaction, followed by a decarboxylation-isomerization reaction to afford E-combretastatin A-1(E-CA1). Finally, CB1 could be obtained via catalytic hydrogenation.



Synthesis of Hybrid Supports ZPS-IPPA and Application for Heterogeneous Olefin Epoxidation

ZOU Xiao-Chuan, SHI Kai-Yun, CHEN Shao-Cheng, FU Xiang-Kai

2013, 34(10):  2319-2326.  doi:10.7503/cjcu20130012

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In this work, a different kind of linker group modified ZPS-IPPA-supported chiral Mn^Ⅲ(salen) were prepared and evaluated in the asymmetric epoxidation of unfunctionalized olefins with m-CPBA as an oxidant. The results demonstrated that the conversions and e.e. values increased in the presence of axial additive via diamine linkers for the immobilized Mn^Ⅲ(salen) but sharply improved in the absence of axial additive via alkoxyl linkers or diphenoxyl. In addition, the heterogeneous catalyst could be reused at least five times without significant loss of activity and enantioselectivity. Furthermore, the conversion and enantioselectivity could maintain the same level when the template reaction was simultaneously magnified, which has a preliminary prospect in the application for industrial.



Structure Characterization and Antitumor Activity of Polysaccharide WPP2 from Pleurotus Eryngii

ZHANG Hua-Peng, ZHANG Jing, NAN Zheng, SUN Run-Guang, ZHANG Peng, LIU A-Juan, LIANG Tao

2013, 34(10):  2327-2333.  doi:10.7503/cjcu20130081

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Polysaccharides are an important class of active components from Pleurotus eryngii with potential biological activities. Scince structure and functions are intimately related, an in-depth study of Pleurotus eryngii polysaccharides would be of interest. In this work, crude polysaccharides were extracted from Pleurotus eryngii by hot water and were further fractionated to give a new polysaccharide fraction termed WPP2. WPP2 was subjected to structural identification by means of UV, HPLC, GC, IR, GC-MS, NMR, ESEM and AFM. In addition, the antioxidant and antitumor activities of WPP2 were evaluated in vitro. The results revealed that WPP2 is rich in Glc with an average molecular weight of about 4.499×10⁵. The main chain of WPP2 was made up of→1,3)-β-D-Glcp,→1,6)-β-D-Galp, and→1,3)-β-D-Manp with two side chains.→1,6)-β-D-Glcp,→1,6)-β-D-Galp and terminal residue→1)-β-D-Glcp were linked to form side chains bearing→1,2,3)-β-D-Manp and→1,2,6)-β-D-Manp residues as branched points. Congo red reaction indicated that WPP2 has the triple-helical structure in aqueous solution. The multi-branched structure of WPP2 was detected at the nanometer scale by ESEM and AFM; the bioactivity analysis in vitro indicated that WPP2 possessed certain antioxidant activity and antitumor effect. The results suggested that the novel polysaccharide WPP2 could potentially be used as a new natural medicine, but the relation of structure and functions need further study.



Effects of Signal Peptide on the Secretory Expression of Multifunctional Amylase OPMA and Its Catalytic Activity

LI Yan-Fei, ZHANG Jin-Xiang, GU Yan-Qin, HAO Qian, CAO Hao, ZHANG Ying-Jiu

2013, 34(10):  2334-2339.  doi:10.7503/cjcu20130337

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The recombinant expression vectors pMA5-OPMA-SN and pMA5-OPMA-SG were constructed by fusing the gene encoding the signal peptide(S) of amyE from Bacillus subtilis 168 with the gene encoding the multifunctional amylases OPMA-N or OPMA-G, and the high-level secretory expression of OPMA-N and OPMA-G were achieved by Bacillus subtilis 168. SDS-PAGE analysis showed that the introduction of the signal peptide was indeed possible to improve the secretion of heterologous protein, and the secretory yields of OPMA-SN or OPMA-SG(53% or 67%) were obviously higher than those of OPMA-N or OPMA-G(45% or 58%), but the signal peptide could not be effectively removed after secretion. The activity analysis demonstrated that the levels of OPMA-SN and OPMA-N activities(5.17 and 4.57 U/mg) were consistent with their secretory yields, but it was not the case for OPMA-SG(4.50 U/mg) and OPMA-G(4.65 U/mg), there was a negative correlation between the activity levels and secretory yields of for OPMA-SG and OPMA-G. The spatial conformation of OPMA-SN and OPMA-SG molecules proved that the presence of the signal peptide at the N terminus of OPMA-N or OPMA-G could not affect the conformation of the catalytic centre in OPMA-N, but affected that in OPMA-SG and resulted in the decrease of OPMA-SG's catalytic activity. These findings could provide important guidance on signal peptide application for secretory expression of heterologous proteins in Bacillus subtilis, and for the structure and function of the target protein.



Physical Chemistry

Molecular Interaction and Morphology of DOPC/DPPC Monolayer

HAO Chang-Chun, ZHANG Lei, SUN Run-Guang, ZHANG Jing, HE Guang-Xiao, YANG Jing

2013, 34(10):  2340-2346.  doi:10.7503/cjcu20130481

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Lipid membrane is widely used in simulation of the dynamic properties and structure characteristics of the biomembranes. We prepared the 1,2-dioleoy-sn-glycero-3-phosphocholine(DOPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC)(1:1, molar ratio), DOPC/DPPC/Chol(2:2:1, molar ratio) monolayers via LB technique at different surface pressures. The interaction between molecules by the thermodynamic analysis method and the morphology were observed by fluorescence microscopy and atomic force microscopy(AFM). Thermodynamic analysis results show that the interaction between DOPC and DPPC is repulsive; it can induce phase separation in monolayers. Both DOPC and DPPC interact with cholesterol by attractive interaction. When the surface pressure is >18 mN/m, the force between DPPC and cholesterol is stronger than DOPC. There is obvious phase separation in the monolayers observation by fluorescence microscopy. The DPPC-enriched micro domains take on "flower-shaped" structure, and the size became larger and larger with increasing surface pressure. Add cholesterol to DOPC/DPPC system, the monolayer changes from gel-fluid phase to fluid-disordered and fluid-ordered phase coexistence structure. The DPPC-enriched domains shape from the "flower-shaped" into a "circular". Observations by AFM verified the results of fluorescence experiments. It can be concluded that the cholesterol has a significant impact on the arrangements of DOPC/DPPC monolayers, and pressure, state of solution are also important for forming the lipid membranes.



Grain Size Effect of MgH₂ on Dehydrogenation Kinetics of 2LiBH₄+MgH₂ System

KOU Hua-Qin, SANG Ge, CHEN Li-Xin, XIAO Xue-Zhang, DENG Shuai-Shuai, HUANG Zhi-Yong

2013, 34(10):  2347-2352.  doi:10.7503/cjcu20130449

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Grain size effect of MgH₂ on dehydrogenation kinetics of the 2LiBH₄+MgH₂ system was investigated. Experimental results show that the grain size of MgH₂ is significantly reduced to 100—200 nm after pre-ball milling for 96 h. It was found that these two step dehydrogenation temperature of 2LiBH₄+MgH₂ system was lowered by 58 and 24℃ respectively through pre-ball milling MgH₂. Meanwhile, the desorption rate was improved obviously as the grain size of MgH₂ decreased. X-Ray diffraction(XRD) analysis indicates that the formation of MgB₂ in dehydrided products is promoted by decreasing the grain size of MgH₂, resulting in an improved reversibility.



Theoretical Studies on Reaction Mechanism of Hydrodesulfurization of Thiophene Catalyzed by Au(111) Plane

NI Zhe-Ming, SHI Wei, XIA Ming-Yu, XUE Ji-Long

2013, 34(10):  2353-2362.  doi:10.7503/cjcu20130385

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The adsorption of thiophene molecule at Au(111) and its mechanism of hydrodesulfurization were elucidated by desity functional theory(DFT) method. All the pertinent species of different mechanisms have been gathered to obtain their preferred adsorption sites. The activation energy and reaction energy of each steps in different mechanisms also have been calculated. The results show that the adsorption at the Top site is most stable when the thiophene plane tilt to the Au(111) surface with S atom. The direct hydrodesulfurization mechanism has a low energy of activation and high temperature is helpful for the hydrodesulfurization reaction, but it is difficult to control the products. The mechanism of indirect hydrodesulfurization is best fit for the hydroisomerization process. The reaction heat of hydrodesulfurization is negative, so reducing the temperature is helpful for the reaction. During the process, the bond length of C—S in thiophene increases gradually when the bond energy of C—S decreases. All of these changes are helpful to the cleavage of C—S. The most feasible reaction pathway is (1) C₄H₄S+H₂α,α-C₄H₆S, (2) α,α-C₄H₆S+H₂C₄H₈S, (3) C₄H₈S+H₂C₄H₁₀+S. Among different steps, the removal of S is the rate-determining step.



Theoretical Study on Electronic Structure and Optical Activity of Chiral Polyoxometalates Modified by Amino Acids

CHI Jia-Shu, SANG Yuan-Mei, YAN Li-Kai, SU Zhong-Min

2013, 34(10):  2370-2376.  doi:10.7503/cjcu20130351

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The geometrical strucutres, electronic structures, UV-visible(UV-Vis) absorption and electronic circular dichroism(ECD) spectra of chiral polyoxometalates(POMs) [Se^ⅣMo₆O₂₁(L-alanine)₃]^2-, [Sb^ⅢMo₆O₂₁(L-alanine)₃]^3- and [Bi^ⅢMo₆O₂₁(L-alanine)₃]^3- modified by L-O₂CCHCH₃NH₃(L-alanine) have been explored via the density functional theory(DFT) method. The effect of heteroatoms on optical activities of studied compounds has been determined. The result indicates that the geometrical structures, UV-Vis spectra absorption intensity and peak shape are affected by heteroatoms. The rotational absorption direction and strength of the ECD spectra significantly change from Se^Ⅳ, Sb^Ⅲ to Bi^Ⅲ. The UV-Vis and ECD spectra in the low-energy range are mainly ascribed to the charge-transfer(CT) transitions from the p orbitals of O atoms to the d orbitals of Mo atoms in the POMs, and the both spectra in the high-energy range are mainly from the heteroatoms in the POMs and the p orbitals of the O atoms connecting with heteroatoms to the d orbitals of Mo atoms. These conclusions are significant for understanding the electronic structures and chiral spectroscopy properties of this kind of amino acids modifying POMs.



Preparation of Colloidal Pt/Ni Bimetallic Nanosols and Their Catalytic Activities for Hydrogen Generation from Hydrolysis Reaction of Sodium Borohydride

KONG De-Cheng, GU Ya-Jun, XIANG Sheng, WANG Peng, CHENG Jun, ZHANG Hai-Jun, ZHANG Shao-Wei

2013, 34(10):  2377-2382.  doi:10.7503/cjcu20130266

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The hydrolytic dehydrogenation of sodium borohydride is a promising integrated technology as a way of hydrogen storage and hydrogen production. This paper reports a facile route for synthesizing the PVP stabilized Pt/Ni bimetallic nanosol by a chemical co-reduction process. The morphology, size, structure and composition of the resultant Pt/Ni bimetallic nanosol were characterized by transmission electron microscopy(TEM) and ultraviolet-visible(UV-Vis) spectrum. The effects of PVP dosage, reducing agent dosage, and metal composition in the hydrolysis of NaBH₄ were studied. The results indicate that the prepared Pt/Ni bimetallic nanosol have an average size of about 2.0 nm. The catalytic activities of the Pt/Ni bimetallic nanosol are superior to monometallic Pt or monometallic Ni, among which especially the Pt₂₀Ni₈₀ bimetallic nanosol shows the highest catalytic activity with a hydrogen generation rate of 16640 mol_H2·mol_Pt^-1·h^-1 at 303 K and an activation energy of 48 kJ/mol. In addition, the prepared Pt/Ni bimetallic nanosol has a good catalytic stability, and even keeps a higher catalytic activity after five runs test.



In-situ Raman Spectra and X-ray Diffraction Study on Pressure-induced Phase Transition in Columbite ZnNb₂O₆

ZHOU Jing, LI Liang, HUANG Feng-Xian, SHEN Hong-Zhi, YANG Hang, ZHOU Qiang, WANG Wen-Quan, XU Da-Peng

2013, 34(10):  2383-2388.  doi:10.7503/cjcu20130138

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In-situ high pressure studies of ZnNb₂O₆ have been performed using Raman spectroscopy and synchrotron X-ray diffraction in a diamond anvil cell up to 29 GPa. Raman experiments show that most Raman peaks decrease in intensity and shift toward high wavenumbers with increasing pressure. Three turn points in the slope of frequency-pressure curve of Raman modes turn up at the pressure around 10, 16 and 20 GPa. Angle dispersive X-ray diffraction results display that some old peaks disappear and some new peaks appear above 10.6 GPa. Both Raman and X-ray diffraction data provide evidence of a reversible phase transition which begins from about 10 GPa and complets at 16 GPa, and then a disorder state is formed above 20 GPa.



Synthesis and Capacitive Properties of C/MWCNTs Composites

FU Yu, SUN Li, TIAN Chun-Gui, LIN Hai-Bo

2013, 34(10):  2389-2394.  doi:10.7503/cjcu20130105

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Carbon/multi-wall carbon nanotubes(C/MWCNTs) composites were synthesized by combination of cyclodextrin wrapping and heat treatment techniques. The application of composites as electrode material for supercapacitors was also demonstrated. The morphology and structure of the composites were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and Raman spectra. The capacitive behavior of the composites was investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The experimental results show that the as-prepared composite exhibits better electrochemical performances than corresponding C and MWCNTs samples. The specific capacitance can reach to 145 F/g, and has no obvious decrease after 3000 cycles at 1 A/g. The results indicate that the effective combination of MWCNTs with other materials is useful for designing the advanced electrode material for supercapacitors.



Structure and Electrochemical Properties of xLi[Li_1/3Mn_2/3] O₂-(1-x)LiNi_5/12Mn_5/12Co_2/12O₂(0≤x≤0.8)

LIU Wei-Wei, KANEKO Shingo, FANG Guo-Qing, SUN Hong-Dan, XIA Bing-Bo, ZHENG Jun-Wei, LI De-Cheng

2013, 34(10):  2395-2400.  doi:10.7503/cjcu20130102

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Li-rich layered cathode materials xLi[Li_1/3Mn_2/3]O₂-(1-x)LiNi_5/12Mn_5/12Co_2/12O₂(0≤x≤0.8)were prepared via spray-dry method. X-ray diffraction(XRD), high resolution transmission electron microscopy(HRTEM), X-ray photoelectron spectroscopy(XPS), electrochemical impedance spectroscopy(EIS) and charge-discharge tests were carried out to investigate the influence of the amount of Li₂MnO₃ component on the structure and electrochemical properties of the materials. It is found that the micro-structure changes with the increase of Li₂MnO₃ content in composition. In the case x≤0.2, the crystal structure of material is similar to parent material LiNi_5/12Mn_5/12Co_2/12O₂. When x≥0.4, the materials show Li₂MnO₃-like structure. And the two structures co-exist in sample of x=0.3. HRTEM observations reveal that the arrangement of transition mental ions in the internal structure transfer from long-range order to long-range disorder and short-range order. As the x value increases from 0.1 to 0.8, the discharge capacity of material increases gradually when x≤0.6, and decreases gradually when x>0.6. It is reasonable considering the increase of charge transfer resistence detected by EIS. As a result, when x=0.6, the material exhibts the highest discharge capacity, which is about 260 mA·h/g at room tempreature and 304 mA·h/g at high tempreature(50℃). The EIS research shows that the micro-structural transformation from order to disorder increases the charge transfer resistance of material, thus yield poor electrochemical performances.



Synthesis of Sb₂S₃ Nanowires and Their Application in Hybrid Solar Cells

ZHANG Hui, WU Fan, HAN Chang-Bao, SHEN Wei, CUI Qi, QIU Ze-Liang, LIU Chang-Wen, GAO Feng, WANG Ming-Tai

2013, 34(10):  2401-2407.  doi:10.7503/cjcu20130093

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High quality Sb₂S₃ nanowires, which were 60—70 nm in diameter and 4—6 μm in length, were synthesized via a facile solvothermal approach by using L-cysteine(C₃H₇NO₂S) as a capping agent, and applied to hybrid solar cells after blending with poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene)(MEH-PPV). The as-synthesized nanowires were characterized by XRD, SEM, TEM, UV-Vis absorption and PL spectra; the solar cells were investigated by current-voltage(J-V) measurements and incident photon-to-current conversion efficiency(IPCE) spectroscopy. The highly pure Sb₂S₃ nanowires have a bandgap of 1.57 eV and grow along [001] direction. In comparison with the solar cells without Sb₂S₃ nanowires, the MEH-PPV/Sb₂S₃ devices exhibit a much higher J_sc depending on the Sb₂S₃ concentration and a certain wide spectral response characteristics due to complementary absorption of Sb₂S₃ nanowires. With addition of the Sb₂S₃ nanowires into the polymer phase, the MEH-PPV/Sb₂S₃ interfaces are created for dissociation of the excitons generated in the polymer and the direct channels are formed for electron transport; on the other hand, the defects on the nanowire surface cause the serious charge recombination that is unfavorable for the photocurrent generation. At the Sb₂S₃/MEH-PPV mass ratio of 5:1, the device with a power conversion efficiency of 0.393% is achieved under AM 1.5 illumination(100 mW/cm²).



Influence of Electrolytes on the Photocathodic Protection Effect of TiO₂ Nanotube Films for Stainless Steel

ZHANG Juan, ZHU Yan-Feng, GUO Ya, XU Lu, QI Hai-Qing, ZHOU Jian-Zhang, DU Rong-Gui, LIN Chang-Jian

2013, 34(10):  2408-2414.  doi:10.7503/cjcu20130080

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The effect of the concentration and the variety of electrolytes(NaNO₃, NaCl, Na₂SO₄, Na₂S, NaOH) in a photoelectrolytic cell on photoelectrochemical properties of a TiO₂ nanotube film prepared by an anodic oxidation method was studied by photoelectrochemical measurements. The results show that the trend of different electrolytes for capturing photogenerated holes is Na₂S>NaOH>Na₂SO₄>NaCl>NaNO₃. Due to the synergistic effect of Na₂S and NaOH in a solution, when the concentrations of Na₂S and NaOH were both 0.5 mol/L, the photogenerated electron-hole pairs could be more effectively separated. The potential of 403 stainless steel in a 0.5 mol/L NaCl solution coupled with the TiO₂ film electrode in a 0.5 mol/L Na₂S+0.5 mol/L NaOH solution decreased by 650 mV under white-light irradiation, indicating the film could provide a good photocathodic protection effect on the steel by the assistance of the electrolyte solution. After the light was cut off, the 403 stainless steel also could be protected to a certain extent by the TiO₂ film.



Polymer Chemistry

Synthesis and Characterization of SiC Ceramic Precursor with High Boron Content

ZHU Yi-Hua, WANG Hao, SHAO Chang-Wei

2013, 34(10):  2415-2420.  doi:10.7503/cjcu20130520

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Polyboroncarbosilane(PBCS) was synthesized via hydroboration BH₃·SMe₂ and dimethyldivinylsilane(DVS) as starting materials. SiC ceramics with high boron content were obtained by pyrolysis of PBCS in N₂. The structures and properties of the polymers were investigated via FTIR, NMR, TGA; and their pyrolytic products were investigated via elemental analysis, X-ray diffraction and SEM. The results indicate that B—C, Si—C, C—H bonds exist in the structure of PBCS; and ceramic yields for the precursor in N₂ are up to 50%. The ceramics exist in amorphous state with the B content of 6.46% after pyrolyzed at 1100℃, and crystallize distinctly to form a multiple phases of B₂O₃, C and β-SiC at 1300℃. The results show a glazed surface and a dense structure when treated below 1500℃.



Preparation of Gold Nanorods@C Hollow Capsules and Applications in Catalysis

YAO Tong-Jie, CUI Tie-Yu, FANG Xue, CUI Fang, WU Jie

2013, 34(10):  2421-2426.  doi:10.7503/cjcu20130505

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Hollow capsules with gold nanorods(GNRs) embedding in the carbon shell were prepared by polypyrrole(PPy) as carbon precursor. The carboxylic-capped polystyrene(PS) nanoparticles were firstly synthesized, then the hexadecyl trimethyl ammonium bromide-stabilized GNRs were self-assembled onto their surface through the electrostatic interaction, and formed PS@GNRs composites. Next, PPy was coated on the surface of PS@GNRs composites; meanwhile, GNRs were embedded in the PPy shell. After calcination in nitrogen atmosphere, the PPy shell was carbonized to the carbon shell and the PS nanoparticles decomposed at the same time. During heat-treatment process, GNRs preserved rod-like morphology without aggregations due to the protection of carbon shell. Upon varying the concentration of pyrrole monomer, both PPy and carbon shell thicknesses could be readily turned. The GNRs@C hollow capsules showed excellent catalytic performance in the reduction of methylene blue with sodium borohydride as reducing agent.



Synthesis and Properties of Polyimides Containing Benzimidazole Group

ZHOU Yu, WANG Da-Ming, ZHAO Xiao-Gang, ZHOU Hong-Wei, CHEN Chun-Hai, DANG Guo-Dong

2013, 34(10):  2427-2430.  doi:10.7503/cjcu20130414

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A diamine monomer containing benzimidazole unit 2-(4-aminophenyl)-4-aminobenzimidazole was polymerized with commercially available dianhydrides to obtain polyimide films. The results of thermal and mechanical properties characterization show that these polyimide films possess considerable thermal resistance and good mechanical properties. Meanwhile, the relative position of the amino group in the diamine monomer imparts bent and distorted conformation of the polyimides, leading to good thermal plasticity and large value of coefficient of thermal expansion.



Preparation and Property of Inherent Flame Retardant Polystyrene/Clay Nanocomposites

SHAN Xue-Ying, TAI Qi-Long, HU Yuan, SONG Lei, LU Siu-Ming

2013, 34(10):  2431-2436.  doi:10.7503/cjcu20130396

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Inherent flame retardant styrenic copolymer/organic modified montmorillonite(OMMT) nanocomposites[P(St-co-AEPPA)/OMMT] were prepared by in situ bulk copolymerization. Ordinary polystyrene/organic modified montmorillonite nanocomposites(PS/OMMT) were prepared as comparative experiments. Effect of phosphorus-nitrogen containing monomer(AEPPA) and OMMT on styrenic copolymer was studied. The structure and morphology of nanocomposites were characterized by X-ray diffraction(XRD) and transmission electron microscopy(TEM), and the dispersion mechanism of OMMT in matrix was discussed. Differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and microscale combustion calorimeter(MCC) were used to research the thermal properties and flammability of composites. The results showed that the incorporation of AEPPA monomer and OMMT could significantly improve the thermal stability and flame retardancy of matrix.



Preparation and Characterization of Novel Poly(2, 6-dimethyl-1, 4-phenylene oxide) Anion-exchange Membranes for Alkaline Fuel Cells

HAN Ke-Fei, YANG Qi-Tao, YU Shu-Ping, YU Jing-Hua, ZHU Hong, WANG Zhong-Ming

2013, 34(10):  2437-2444.  doi:10.7503/cjcu20130371

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Alkaline anion exchange membrane(AEM) is one of the key materials for anion exchange membrane fuel cells(AEMFC). In this work, starting from poly(2,6-dimethyl-1,4-phenylene oxide)(PPO), the brominated PPO(BrPPO) was synthesized and characterized by FTIR and ¹H NMR spectra. Then an alkaline imidazolium-type resin(PPO-Im) was fabricated via functionalization of BPPO with N-methylimidazole, and the corresponding blending membranes with polyvinylalcohol(PVA) in different content percentages were prepared and characterized by FTIR and ¹H NMR spectra. The SEM images show the prepared membranes are smooth and homogenous. The ion exchange capacity, water uptake, swelling ratio of all prepared membranes were also measured. The ion exchange capacity ranges from 0.47 mmol/g to 1.52 mmol/g. The water uptake is in the range of 50.4%—151.2%. The swelling ratio is in the range of 79.2%—164.2% after being immersed in water at 60℃. The M4 membrane exhibits the highest hydroxide conductivity(49.1 mS/cm at 90℃) by AC-impedance spectroscopy. The tensile strength result shows elongation at break increased to 128%. The thermal gravimetric analyses indicate that the membranes have high thermal stability, which the initial decomposition temperature of imidazolium cation is 170℃, higher than that of quaternary ammonium(120℃). After being immersed in 2 mol/L NaOH for 192 h, the membrane conductivity still keeps their original 81%. All these properties indicate that PPO-Im/PVA membrane is promising for potential applications in alkaline membrane fuel cells.



Melt Processing of PVA with Magnesium Chloride and Polyethylene Glycol as the Complex Plasticizer

JIANG Xian-cai, SONG Jie, JIANG Ting, DAI Hua, ZHANG Xi

2013, 34(10):  2451-2456.  doi:10.7503/cjcu20130109

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Poly(vinyl alcohol)(PVA) samples were prepared through the melt processing by employing magnesium chloride and polyethylene glycol(PEG) as the complex plasticizer. The interaction between the complex plasticizer and PVA was investigated by Fourier transform infrared spectroscopy(FTIR). The influences of the complex plasticizer on the crystalline and thermal properties were studied by X-ray diffraction(XRD), differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA), respectively. The results show that the plasticizer can effectively destroy the hydrogen bonding between PVA molecules. The crystallinity of PVA decreased rapidly with the addition of the complex plasticizer. Thermal measurements show that the melting point(T_m) of PVA decreases, the thermal stability improves and thus the thermal processing of PVA are achieved. The obtained PVA film shows good mechanical property, with the tensile strength of 31 MPa and the elongation at break of 466%.