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10 January 2017, Volume 38 Issue 1

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Cover and Content of Chemical Journal of Chinese Universities Vol.38 No.1(2017)

2017, 38(1):  0-0. 

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Review

Advance in Ultrasensitive Detection of MicroRNA^†

WANG Ziyue, LIU Meng, ZHANG Chunyang

2017, 38(1):  1-11.  doi:10.7503/cjcu20160587

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MicroRNA(miRNA) is a class of endogenous noncoding RNA molecule with the length of about 22 nucleotides. MicroRNA may regulate more than 50% of human protein-coding genes, and plays important roles in regulating cell differentiation and other biological processes. The abnormal expression of miRNA is closely related to the occurrence of many diseases including cancers. Therefore, miRNA may function as a potential biomarker for molecular diagnostics. The sensitive detection of miRNA is essential to the early clinical diagnosis and the development of anticancer drugs. Because of the short size, low abundance in total RNA samples and the homologous similarities in miRNA family, the ultrasensitive detection of miRNA remains a great challenge. Recently, many new methods have been developed to improve the detection sensitivity. This review focuses on the advance in miRNA detection methods including colorimetric assay, fluorescent assay, chemiluminescent assay, surface enhanced Raman scattering, single molecules detection and electrochemical detection. In addition, we give a new insight into future development of miRNA assay.



Articles: Inorganic Chemistry

Synthesis, Structures and Properties of Homochiral Coordination Polymers Assembled from Semirigid Lactic Acid Derivatives^†

XU Zhongxuan, ZHAO Guanglian, LUO Le, LONG Zhenmin

2017, 38(1):  12-19.  doi:10.7503/cjcu20160647

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Under the solvothermal reaction condition, two pairs of homochiral coordination polymers, namely [Cd₂((R)-CBA)₂(DPEE)(H₂O)₂]_n(1-D), [Cd₂((S)-CBA)₂(DPEE)(H₂O)₂]_n(1-L), [Cd((R)-CBA)(1,4-DIB)]·H₂O(2-D) and [Cd((S)-CBA)(1,4-DIB)]. H₂O(2-L)[DPEE=(E)-1,2-di(pyridin-4-yl)ethene; 1,4-DIB=1,4-di(1H-imidazol-1-yl)benzene; (R)-H₂CBA=(R)-4-(1-carboxyethoxy)benzoic acid; (S)-H₂CBA=(S)-4-(1-carboxyethoxy)benzoic acid], have been prepared from synthetic lactic acid derivative ligands[(R)-H₂CBA and(S)-H₂CBA], auxiliary ligands and Cd²⁺ ions. Among these complexes, 1-D and 1-L have ladder-like Cd-CBA^2- chains, which are further linked by DPEE ligands to form a 2D framework. Complexes 2-D and 2-L feature three-dimensional supramolecular structure with hydrogen bonds, containing three kinds of homochiral helical chains. Moreover, the thermal stabilities, solid-state circular dichroism(CD) and photoluminescent properties of the complexes were also investigated.



Cutting Process and Mechanism of Graphene Oxide Sheets in Water by Ultrasonic^†

ZENG Zehua, LI Shichun, LIU Yu, XU Jinjiang, ZHOU Yuanlin

2017, 38(1):  20-27.  doi:10.7503/cjcu20160557

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Graphene oxide(GO) sheets were cut into smaller pieces in water by ultrasonic. The effects of treatment time on the GO sheets’ size and GO surface groups were investigated. Moreover, the mechanism of cutting process was discussed. The results indicate that the diameter of GO sheets decreases from 2000 nm to 200 nm with increasing treatment time. The species of GO surface groups do not change after ultrasonic treatment. However, with increasing treatment time, the content of epoxy groups decreases, the content of carboxylate groups changes little, the content of ketone groups firstly decreases and then increases, the content of hydroxyl groups firstly increases and then decreases, and the content of ether oxygen groups increases. The ultrasonic cavitation leads to the break of carbon-carbon bonds, epoxy groups and ketone groups, which fractures the GO sheets. After that, the hydroxyl radical and hydrogen radicals formed from water react with carbon radicals of GO to form new carbon-carbon bonds and ether oxide or hydroxyl groups. The hydroxyl groups convert into ketone groups under long time ultrasonic treatment. The cutting process of GO by ultrasonic can be proceeded under mild conditions without other chemicals, which is a promising technology for cutting two-dimensional materials.



Analytical Chemistry

Effects of Hydroxypropyl-β-cyclodextrin(HPCD) on the Interaction of 1-Hydroxypyrene with Bovine Serum Albumin^†

ZHANG Jing, CHEN Linfeng, ZHU Yaxian, ZHANG Yong

2017, 38(1):  28-34.  doi:10.7503/cjcu20160514

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Fluorescence spectra, circular dichroism spectra and UV visible absorption spectra were employed to investigate the feasibility of regulating the interaction of 1-hydroxypyrene(1-OHPyr) with bovine serum albumin(BSA) using hydroxypropyl-β-cyclodextrin(HPCD) under simulated physiological conditions, and the related mechanism was preliminary discussed. The results showed that HPCD can inhibit the interaction of 1-OHPyr with BSA, and the binding constant of 1-OHPyr-BSA was decreased to 1.45×10⁵ L/mol at 291 K. HPCD can also restore the helix of BSA and inhibit the polarity changes of the local microenvironment of tryptophan(TRP) residues in BSA. HPCD can increase the fluorescence lifetimes of 1-OHPyr and BSA in 1-OHPyr-BSA system, meanwhile increase the binding distance of 1-OHPyr with BSA. The inclusion behavior of HPCD with 1-OHPyr was primarily the main reason why HPCD affected the binding of 1-OHPyr with BSA.



Organic Chemistry

Synthesis and Antibacterial Activities of Myricetin Derivatives ontaining Acidamide Moiety^†

XIAO Wei, RUAN Xianghui, LI Qin, ZHANG Juping, ZHONG Xinmin, XIE Yan, WANG Xiaobin, HUANG Minguo, XUE Wei

2017, 38(1):  35-40.  doi:10.7503/cjcu20160654

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Twelve novel myricetin derivatives containing acidamide moiety were designed and synthesized from myricetin. All the compounds were characterized by ¹H NMR, ¹³C NMR and HRMS. The preliminary bioassay results indicated that all of the title compounds exhibited a certain antibacterial activities in vitro against X. oryzae, X. citri and R. solanacearum. Moreover, These title compounds 3a, 3e, 3f, 3h and 3k displayed good antibacterial activities against the above three plant pathogenic bacteria. Especially, compound 3e displayed 100% inhibition rates against X. oryzae and R. solanacearum at 200 μg/mL, respectively, which is more than the control bismerthiazol(72.85% and 75.86%, repectively).



3D-QSAR and Interaction Mechanism of Flavonoids s P-glycoprotein Inhibitors^†

LIU Benguo, LIU Jiangwei, LI Jiaqi, GENG Sheng, MO Haizhen, LIANG Guizhao

2017, 38(1):  41-46.  doi:10.7503/cjcu20160643

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A 3D-QSAR model of 30 flavonoids as P-glycoprotein inhibitors was constructed using Topomer CoMFA. Nine flavonoids were used to validate the external predictive power of the obtained model. The multiple correlation coefficients of fitting, cross validation and external validation were 0.971, 0.728 and 0.816, respectively. The molecular docking modes of chrysin and its prenylated derivatives were established by the Surflex-dock method. The results showed the lipophilicity of flavonoids could be improved by the prenyl modification, which resulted to the stronger interaction with the hydrophobic pocket of P-glycoprotein.



Synthesis and Anti-tumor Activity of Tubulysins Analogues^†

BAI Xinfa, MA Xuan, XIE Xiaoxia, SHAO Mingsha, GUO Ningning, YAN Ning, YAO Lei

2017, 38(1):  47-55.  doi:10.7503/cjcu20160550

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Tubulysins family is a kind of natural compound with potent antitumor activity. To simplify the synthesis route and find new antitumor compounds is becoming a hotspot of research in recent years. Starting from 3-nitrobenzoic acid, after 7 steps transformations, 12 new tubulysin analogues were synthesized via the conformation restrain and bioisostere principle. These structures are featuring 3-substituted analine moieties. All these compounds are new compounds, and their structures were confirmed by ¹H nuclear magnetic resonance(NMR), ¹³C NMR, and high resolution mass spectrometer(HRMS). The antitumor activities were tested by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyetl trazolium bromide(MTT) method in vitro using MDA-MB-231 and MCF7 cells, and compound Ⅱb exhibited moderate antitumor activity(7.6 and 11.8 μmol/L).



Physical Chemistry

Theoretical Studies on Noncovalent Interactions Between Charged Histidine Side Chain and DNA Base^†

LI Lei, LI Shushi, WANG Changsheng

2017, 38(1):  56-62.  doi:10.7503/cjcu20160699

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The gas phase optimal structures of eighteen hydrogen-bonded complexes, composed of a charged histidine side chain and one of DNA bases, were obtained at the MP2/6-31+G(d,p) level, and the corresponding optimal structures in water solvent were obtained at the MP2/6-31+G(d,p) level with the Polarizable Continuum model(PCM). Twelve π-π⁺ stacking and T-shaped complexes composed of a charged histidine side chain and a DNA base were taken from the Wetmore’s work. The gas phase binding energies were evaluated at the CP-corrected MP2/aug-cc-pVTZ and M06-2X-D3/aug-cc-pVDZ level. The binding energies in water solvent were evaluated at the MP2/aug-cc-pVTZ and M06-2X-D3/aug-cc-pVDZ level with the PCM model. Calculation results show that the CP-corrected M06-2X-D3/aug-cc-pVDZ method produces accurate binding energies for these noncovalent complexes. Based on the obtained binding energies, it can be deduced that, in gas phase, the ionic hydrogen bonding is much stronger than the π-π⁺ stacking and T-shaped interaction of a charged histidine with a same base molecule; histidine hydrogen bonds much stronger with either cytosine or guanine than with adenine or thymine; and the π-π⁺ T-shaped interaction of the histidine with guanine or cytosine is stronger than the ionic hydrogen bonding of the histidine with adenine or thymine. In water solvent, the ionic hydrogen bonding between a charged histidine and a same base molecule is still stronger than the π-π⁺ stacking and T-shaped interaction between a charged histidine and a same base molecule; histidine still hydrogen bonds stronger with either cytosine or guanine than with adenine or thymine; but the π-π⁺ T-shaped interaction of the histidine and cytosine is weaker than the ionic hydrogen bonding of the histidine and adenine or thymine; it can be indicated that the charged histidine side chain will mainly interact with DNA bases through ionic hydrogen bond to form hydrogen-bonded complexes in water solvent.



Molecular Dynamics Simulations of EDTA-modified Graphene Oxide for Pb(Ⅱ) and Na(Ⅰ) Removal^†

LIU Shasha, ZHANG Heng, WANG Hua, YUAN Shiling, HOU Shifeng

2017, 38(1):  63-71.  doi:10.7503/cjcu20160658

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The chelating groups N-(trimethoxysilylpropyl) ethylenediamine triacetic acid(EDTA-silane) were linked to graphene oxide(GO) surfaces through a silanization reaction, and this modified GO(GO-EDTA) was used to remove the heavy metal in the solution. By using molecular dynamics simulation at the molecular level, the absorption distribution, dynamic properties of Pb²⁺ on the GO-EDTA surface were investigated, the different absorption behaviors of Pb²⁺ and Na⁺ between GO and GO-EDTA systems were compared. At the same time, the interaction between GO-EDTA and Ca²⁺ was simulated, which was comparable to the adsorption behavior of Pb²⁺. The simulation result shows that: (1) the adsorption sites of Pb²⁺ and Na⁺ are the carboxyl groups in the GO-EDTA system, rather than the hydroxyl groups on graphene oxide surface; (2) the absorption conformations of Pb²⁺ and Na⁺ to carboxyl groups are different. For Pb²⁺ ions, they form the 2:1 type with carboxyl group, i.e. one Pb²⁺ ion combines with two carboxyl groups; while for Na⁺ ions, it is the 1:1 type, i.e. one Na⁺ ion combines with one carboxyl group; (3) comparison with Ca²⁺ and Na⁺ ion, the energy barrier of forming COO^--Pb²⁺ ion pair conformation is lowest while the energy barrier to break this conformation is higher. This result indicates that the Pb²⁺ ions are adsorbed well on GO and GO-EDTA films.



Alkylation Desulfurization of FCC Gasoline over Brönsted-Lewis Organic-inorganic Heteropoly Acid Catalyst^†

YU Fengli, WANG Qingyu, LI Guixiao, YUAN Bing, XIE Congxia, YU Shitao

2017, 38(1):  72-76.  doi:10.7503/cjcu20160533

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A series of Brönsted-Lewis organic-inorganic heteropoly acids was synthesized and used for catalyzing alkylation desulfurization of model fluid catalytic cracking(FCC) gasoline. Among these prepared Brönsted-Lewis organic-inorganic heteropoly acids, Sm_0.33[MIM-PS]HPW₁₂O₄₀ has the highest acid strength and exhibits the best catalytic activity for the alkylation of three thiophenic sulfides including thiophene(T), 2-methyl thiophene(2-MT) and 3-methyl thiophene(3-MT) in model FCC gasolines. The effects of the dosage of the catalyst, reaction temperature and reaction time on the conversions of three thiophenic sulfides catalyzed by Sm_0.33[MIM-PS]HPW₁₂O₄₀ were investigated. The selected optimal conditions as follows: the mass ratio of the catalyst to model FCC gasoline 1:50, reaction temperature 125 ℃ and reaction time 1 h. Under the optimal conditions, T, 2-MT and 3-MT all can be nearly completely transformed. The recyclability of the catalyst Sm_0.33[ MIM-PS]HPW₁₂O₄₀ was investigated. The results show the catalyst exhibits very excellent recyclability. Under the above selected reaction conditions, the catalytic activity of Sm_0.33[MIM-PS]HPW₁₂O₄₀ for the alkylation of three thiophenic sulfides nearly remains unchanged during 12 recycles.



Effects of Silane-modified Nano ZrO₂ on the Corrosion Resistance of Epoxy Coating on the Surface of Mg-Li Alloy^†

SONG Dalei, LIU Siqi, LI Feng, WANG Yanli, ZHANG Tao, YAN Yongde, ZHANG Meng, WANG Jun

2017, 38(1):  77-84.  doi:10.7503/cjcu20160512

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The epoxy coatings containing ZrO₂ nanoparticles modified with bis-[3-(triethoxysilyl)propyl]tetrasulfide(KH-69 silane) were prepared by coating method on the surface of Mg-Li alloy. The effect of concentration of KH-69 silane-modified ZrO₂ nanoparticles on the corrosion resistance of epoxy coatings was evaluated. The addition of KH-69 silane-modified ZrO₂ nanoparticles can considerably improve the corrosion resistance of the epoxy coating on the surface of Mg-Li alloys. Among them, the epoxy coating containing 1.0% KH-69 silane-modified ZrO₂ nanoparticles exhibits the highest corrosion resistance. After 528 h of immersion in 3.5% NaCl solution, its low frequency impendence valve is about 1.6×10⁹ Ω·cm², which exhibits an increase of about five order of magnitude as compared with the blank epoxy coating.



pH-Responsive Pickering Emulsions Stabilized by Silica Nanoparticles in Combination with N-Dodecyl-β-aminopropionate^†

LIU Kaihong, LIN Qi, CUI Zhenggang, PEI Xiaomei, JIANG Jianzhong

2017, 38(1):  85-93.  doi:10.7503/cjcu20160477

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pH-responsive Pickering oil-in-water emulsion with n-decane as oil phase was prepared using negatively charged silica nanoparticles in combination with trace amount of amphoteric surfactant, N-dodecyl-β-aminopropionate(DAP), as stabilizer. The emulsion is stable at pH≤4.0 but unstable at pH≥6.0 at am-bient temperature, and therefore can be cycled between stable and unstable for many times. In acidic aqueous media the amphoteric surfactant molecules of amino acid type are turned to cationic form and can then adsorb at negatively charged silica nanoparticle surface with head-on configuration via electrostatic interaction, ren-dering particles surface activity by in situ hydrophobization. However in neutral and alkali aqueous media the amphoteric surfactant molecules are turned back to amphoteric or anionic forms which mostly desorb from particles surface, triggering de-hydrophobization of the particles and coalescence of the oil droplets in emulsion. The relative mechanisms are revealed by measurements of adsorption, Zeta potential, as well as contact angles.



Preparation of BiPO₄/BiVO₄ Composites with High Visible-light Photocatalytic Activity^†

LIU Qiongjun, LIN Bizhou, LI Peipei, GAO Bifen, CHEN Yilin

2017, 38(1):  94-100.  doi:10.7503/cjcu20160476

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BiPO₄/BiVO₄ composites were prepared by combining hydrothermal and solvothermal synthetic methods. Field emission scanning electron microscopy(FESEM) and transmission electron microscopy(TEM) revealed that the as-prepared BiVO₄ exhibited a truncated bipyramid morphology with high {010}, {110} exposed facets, and that the as-obtained BiPO₄ nanoparticles were grown on the surface of BiVO₄, leading to the formation of the BiPO₄/BiVO₄ heterojunction. The transient photocurrent-time behaviors indicated that the formed heterojunction made the transfer and separation of the photo-generated carriers more efficient. The as-synthesized BiPO₄/BiVO₄ composites exhibited high photocatalytic activities in the degradation of rhodamine B under visible-light irradiation. It was found that the sample prepared with a BiPO₄/BiVO₄ molar ratio of 3:10 in the reactants showed the best performance.



A New Formic Acid/Iron Ion Fuel Cell^†

ZOU Tao, YI Qingfeng, ZHANG Yuanyuan, DENG Zhongliang, LEI Ming, ZHOU Xiulin

2017, 38(1):  101-107.  doi:10.7503/cjcu20160457

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A new formic acid/iron ion(Ⅲ) fuel cell was constructed with formic acid as the fuel and Fe³⁺ as oxidant. Multi-walled carbon nanotubes(MWCNTs) and β-cyclodextrin(β-CD) modified MWCNT(β-CD-MWCNT)-supported palladium-based catalysts, PdSn/MWCNT, Pd/β-CD-MWCNT and PdSn/β-CD-MWCNT, were synthesized and used to electro-catalyze formic acid oxidation. Cyclic voltammograms(CVs) and chronoamperograms(CAs) were applied to investigate the electroactivity of the catalysts for formic acid oxidation in alkaline media. The results showed that addition of suitable amount of tin to palladium and modification of MWCNT with β-CD can promote electrocatalytic activity of Pd/MWCNT catalyst for formic acid oxidation. The formic acid/iron ion(Ⅲ) fuel cell with the prepared Pd-based catalysts as anode and carbon powder as cathode presents the open circuit voltage of 0.98—1.20 V. The fuel cell with PdSn/β-CD-MWCNT as anode exhibits the maximum current density of 50 mA/cm² and the maximum power density of 12.6 mW/cm², showing a much better cell performance than the fuel cell with Pd/C as the anode.



Effect of S\begin{array}{c}{O}_4^{2-}\end{array} Doping on Electrochemical Properties of the Nasicon Li₃Fe₂(PO₄)₃ Cathode^†

ZHANG Bo, HE Jun, HUA Zhengshen, WANG Xin, PENG Huifen

2017, 38(1):  108-114.  doi:10.7503/cjcu20160452

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Effect of S\begin{array}{c}{O}_4^{2-}\end{array} doping on electrochemical properties of the Li₃Fe₂(PO₄)₃ cathode materials was studied. Phase constitutents and electrochemical properties of the Li_3-xFe₂(PO₄)_3-x(SO₄)_x(x=00.90) materials were characterized by XRD, charge-discharge technology, cyclic voltammetry and electrochemical impedance spectrum. The results proved that the added S\begin{array}{c}{O}_4^{2-}\end{array} anions mainly dissolved in the Li₃Fe₂(PO₄)₃ compound, concomitant with the secondary phase, Fe₂O₃. Introduction of the S\begin{array}{c}{O}_4^{2-}\end{array} anions resulted in a parabolic variation of discharging capacity for the Li₃Fe₂(PO₄)₃ compound, and that the sample with the S\begin{array}{c}{O}_4^{2-}\end{array} content(x) of 0.60 exhibited the best performance. Its initial discharging capacity was about 111.59 mA·h/g at a rate of 0.5C, and this value was 18. 4% higher than that without any S\begin{array}{c}{O}_4^{2-}\end{array}. After 60 charge-discharge cycles, its capacity retention was around 96% at a rate of 0.5C. Moreover, 97% of the initial capacity was obtained for this material by gradually increasing discharging rates from 0.5C to 5C, and then decreasing back to 0.5C, together with 10 charging-discharging cycles at each rate. Above-mentioned improvement in electrochemical properties for the S\begin{array}{c}{O}_4^{2-}\end{array} substituted samples should result from their enhanced redox ability, decreased internal resistance and polarization, and increased Li⁺ diffusion coefficients of the batteries.



Chemical Looping Conversion of Methane over CeO₂-based and Co₃O₄-based Co₃O₄-CeO₂ Oxygen Carriers:Controlling of Product Selectivity^†

ZENG Liangpeng, HUANG Fan, ZHU Xing, ZHENG Min, LI Kongzhai

2017, 38(1):  115-125.  doi:10.7503/cjcu20160411

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Two series of Co₃O₄/CeO₂(x)[x is the molar ratio of cobalt and cerium atoms, n(Co)/n(Ce)=5:5―9:1] and Ce_1-yCo_yO_2-δ(y=0.1—0.4) composite oxides were prepared by the hydrothermal method. The physicochemical properties of these oxides were characterized by means of X-ray powder diffraction(XRD), BET(Brunauer-Emmett-Teller) surface area, temperature-programmed reduction(TPR) and Raman spectrum technologies. The prepared materials were used as an oxygen carrier for chemical looping conversion of methane in a fixed-bed reactor. The results showed that both the Co₃O₄/CeO₂(x) and Ce_1-yCo_yO_2-δ oxygen carriers exhibited higher reactivity for methane conversion than single cerium oxide and cobalt oxide. However, the selectivity of CO₂ and CO in the CH₄ reaction over the two types of samples are significantly different. Owing to a larger surface area and the formation of Ce-Co-O solid solution, the oxygen storage capacity of Ce_1-yCo_yO_2-δ oxygen carrier was improved significantly. Moreover, the reaction of Ce_1-yCo_yO_2-δ with methane mainly generated CO and H₂ due to good matching between the lattice oxygen mobility and the methane activation rate. On the other hand, the strong interaction between CeO₂ and Co₃O₄ also strongly enhanced the oxygen storage capacity and activity of Co₃O₄/CeO₂(x) oxygen carriers. But they mainly concerted the methane to CO₂ and H₂O owning to the relatively high concentration of active oxygen. In conclusion, the Co₃O₄/CeO₂(x) composite oxides can be used as oxygen carriers for chemical looping combustion of methane, while the Ce_1-yCo_yO_2-δ oxidesare more suitable for the chemical looping partial oxidation of methane to produce syngas. The sequential cyclic reaction experiments indicated that both the two types of oxygen carriers showed high stability during the successive redox testing.



Preparation and Characterization of HZSM-5/SAPO-11 Composite Molecular Sieves and Their Catalytic Properties in Isobutane Aromatization^†

ZHANG Ruizhen, WEN Shaobo, XING Pu, ZHAO Xin, WANG Zhixiang, HAN Peide, ZHAO Liangfu

2017, 38(1):  126-132.  doi:10.7503/cjcu20160369

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HZSM-5/SAPO-11 composite molecular sieves with different silicon contents were synthesized hydrothermally via in situ overgrowth of SAPO-11 on ZSM-5 pretreated by polydiallyldimethylammonium chloride(PDDA), and were characterized by means of XRD, SEM, TEM, FTIR and NH₃-TPD. The catalytic activity, stability and BTEX(benzene, toluene, ethylbenzene and xylenes) selectivity of HZSM-5/SAPO-11 in isobutane aromatization were also investigated. All the results were compared with those of ZSM-5, SAPO-11, and the mechanical mixtures of ZSM-5 and SAPO-11 and showed that the ZSM-5/SAPO-11 composites were composed of ZSM-5 covered by about 20 nm SAPO-11 round crystals, that modulation of ZSM-5/SAPO-11 acidity by altering Si content could effectively enhance the synergetic aromatization effect between strong and weak acids and restrain the cracking of iso-butane and the generation of C9⁺, thus the liquid yield and stability of aromatization were superior to HZSM-5 and mechanical mixtures when the Si content reaches 0.6 significantly.



Polymer Chemistry

Correlation of Transesterification Between Poly(lactic acid) and Poly(propylene carbonate) on Catalysts^†

ZHANG Min, ZHANG Shuyang, LIU Zhengying, YANG Wei, YANG Mingbo

2017, 38(1):  133-140.  doi:10.7503/cjcu20160619

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Stannous octoate[Sn(Oct)₂] and tetrabutyl titanate(TBT) were selected as transesterification catalysts to investigate the transesterification of poly(lactic acid)(PLA)/ poly(propylene carbonate)(PPC) blends. From the gel permeation chromatography(GPC) and ¹H nuclear magnetic resonance(¹H NMR) results of pure PLA, PPC under the catalysis of Sn(Oct)₂ or TBT, it was found that PLA mainly had chain scission under Sn(Oct)₂ catalyzing while intramolecular transesterification under TBT catalyzing. PPC mainly showed chain scission, mostly in high molecular weight molecule chains, under two kinds of catalysts, and the catalysis activity of TBT was more effective than that of Sn(Oct)₂. Considering the transesterification of PLA/PPC catalyzed by Sn(Oct)₂, TBT or composite catalyst[Sn(Oct)₂/TBT], respectively, a certain extent of transesterification under any catalyst would be realized, accompanied by chain scission. PLA/PPC with Sn(Oct)₂ or Sn(Oct)₂/TBT was given priority to chain scission rather than transesterification, but TBT could promote the transesterification mainly. Due to the chain scission of neat PPC under any single catalyst mostly happened in high molecular weight molecules chain, a lower transesterification degree could be obtained when the mass ratio of PLA/PPC was 1:1, which would be a good guidance to further improve the degree of transesterification between PLA and PPC.



Ordered Self-assembly of Gemini Molecules in Mesoporous Silica Channels Constructing Normal Micelles to Assist the Migration of OH-†

WANG Yifu, DONG Jinxin, WANG Jilin, WANG Lulu, FENG Ruijiang

2017, 38(1):  141-149.  doi:10.7503/cjcu20160596

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Using assembly properties of Gemini surfactants[maleic alkylene group diethyl bis(octyl dimethyl chloro/bromide), abbreviated as G_8-2-8], the normal wormlike micelles, on which were full of quaternary ammonium groups, were orderly assembled in the mesoporous silica channels by the induction of sodium salicylate(NaSal). The above mentioned normal wormlike micelles and the Si hydroxyl groups, which were in the inner wall of the porous silicon, function together as annular water chambers to construct the orderly and efficient transmission channels of OH^-. The study of the G_8-2-8/NaSal micelle systems’ rheological properties suggested that the G_8-2-8/NaSal micelle network systems have been formed. Under the same experimental conditions, the formation process of G_8-2-8/NaSal micelle network systems was introduced into polysulfone system to prepare the high alkaline-resistant anion exchange membranes, which with orderly, efficient OH^- transmission channels. The characterization results indicated that ion conductivities, water uptake and ion exchange capacity showed a rising trend with the increasing mass fraction of G_8-2-8, especially under the condition which the ion exchange capacity and water uptake were not highlevel, but the migration efficiency of OH^- had improved significantly. The 400 h high temperature alkaline-resistant test indicated that the largest decline of ion conducti-vity was only round about 1.5%, and no obvious changes on morphology, which showed excellent alkaline resistance stability.



Influence of Atmosphere and Force During Thermal Imidization on the Structure and Properties of BPDA-PDA Polyimide Fibers^†

YANG Wenke, LIU Fangfang, ZHANG Ensong, QIU Xuepeng, JI Xiangling

2017, 38(1):  150-158.  doi:10.7503/cjcu20160580

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The process of thermal imidization of polyamideacid(PAA) fibers affects the properties of the obtained polyimide(PI) fibersdirectly. Herein, the influence of atmosphere and force during thermal imidization on the structure and properties of PI fiber derived from 3,3',4,4'-biphenyltetra-carboxylic dianhydride(BPDA) and p-phenylenediamine(PDA) was studied. As PI fibers isothermally treated for 5 min, though there is no apparent difference on the morphology of their surface at different atmospheres, the highest tensile strength and initial modulus of fibers treated under nitrogen can reach about 1.25 and 65.0 GPa which are better than those treated in the air, indicating an effective protection of nitrogen atmosphere on the fiber. As longer treatment time of 40 min was applied, the protection of nitrogen atmosphere on the fiber surface was visible in the scanning electron microscopy(SEM) images. However, for the mechanical properties, the effect of atmosphere was only remarkably when fibers treated at 450 ℃. As PAA fibers treated at temperatures lower than 450 ℃, the long-time treatment became the main factor to influence the mechanical properties. And as PAA fibers treated higher than 450 ℃, the mechanical properties were lowered since the degradation of fibers in both atmospheres. As force is applied during the thermal imidization, the expansion of fibers during imidization can be enhanced. With increasing the applied force from 0.0025 N to 0.32 N, the length of the obtained PI fibers increases from 5.0% to 15.5% and the diameter decreases from 16.0 μm to about 12.8 μm. Moreover, it is found that all of the d-spacing of the (004) crystals faces, the crystal size along the fiber axis, the absolute value of coefficient of thermal expansion(CTE) and temperature of glass transition(T_g) of the fibers increase with the applied force. The tensile strength of fibers seems insensitive to the applied force and remains at about 0.90 GPa. The elongation decreases slightly from 2.50% to 2.30% and the initial modulus increases from 53.0 GPa to 65.0 GPa as the applied force increases.



Polyamidoximation of Hollow Mesoporous Silica and Its Application in Adsorption of Cr(Ⅵ)^†

LI Miaomiao, GONG Yumei, GUO Jing, YU Yue, ZHANG Sen, ZHAO Miao

2017, 38(1):  159-164.  doi:10.7503/cjcu20160398

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Polyamidoximation of hollow mesoporous silica(HMS/PAO) was prepared by tranforming the cyano groups in polyacrylonitrile grafted from hollow mesoporous silica(HMS) through polymerization of acrylonitrile initiated by ceric ammonium nitrate. The hollow mesoporous silica was prepared by a facile one-pot sol-gel method. The microstructure and characteristic of the HMS and HMS/PAO were examined by Fourier transform Infrared spectra(FTIR), X-ray diffraction, scanning electron microscope(SEM), N₂ adsorption desorption isotherm. The results showed that the diameter of the HMS was about 400 nm, and the size of the mesoporous was ca. 11.0 nm. The size of the mesoporous was ca. 4.6 nm and more uniform and smaller. As potassium dichromate solution(K₂Cr₂O₇) was used as a target solution for detecting adsorption capacity of the prepared HMS/PAO, the adsorption chromium kinetics was consistent with the pseudo-second-order kinetics model by analyzing the adsorption amount as a function of the sorbent dispersed duration in solution at pH=2.0. The adsorption capacity of HMS/PAO for chromium was as much as 0.46 mmol/g. Therefore, it is an adsorbent with high efficiency.



Synthesis and Characterization of Poly(E,K) and Poly(E,R)^†

WANG Huijie, YU Haiyang, ZHANG Dawei, TANG Zhaohui, CAO Qi

2017, 38(1):  165-172.  doi:10.7503/cjcu20160190

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A series of random copolymers Poly(E,K) and Poly(E,R) was synthesized by the ring-opening polymerization of amino acid-N-carboxyanhydride(amino acid-NCA), along with changing the feed ratio of glutamin acid-N-carboxyanhydride(BLG-NCA) and lysine(benzyloxycarbonyl)-N-carboxyanhydride[Lys(Z)-NCA] as well as BLG-NCA and ornithine(benzyloxycarbonyl)-N-carboxyanhydride[Orn(Z)-NCA] and by the subsequent deprotection and guanidination. These random copolymers were confirmed by nuclear magnetic resonance(¹H NMR and ¹³C NMR), and the molar ratios of different amino acids in the copolymers were close to the feed ratios of corresponding NCA in the ring-opening polymerization. Dynamic light scattering(DLS) test showed that the random copolymers assemble to uniform micelles with less than 200 nm diameter at pH of 7.4. The zeta potential of the random copolymers could change with the pH of solution, suggesting that the copolymers are pH-sensitive.