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10 June 2017, Volume 38 Issue 6

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Cover and Content of Chemical Journal of Chinese Universities Vol.38 No.6(2017)

2017, 38(6):  0-0. 

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Special Articles of China International Conference on Electrospinning(CICE 2016)

Controllable Synthesis of Ag Decorated ZnO Nanofibers for Enhanced Photocatalysis

SUN Lianzhi, ZHAO Shengzhe, GAO Zhiling, CHENG Zhiqiang

2017, 38(6):  907-914.  doi:10.7503/cjcu20160864

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A simple and efficient procedure was developed to fabricate ZnO nanofibers by electrospinning and subsequent calcination. With the hydrothermal method, Ag nanoparticles(AgNPs) were deposited onto the surface of the ZnO nanofibers. Structure, composition and morphology of Ag/ZnO nanofibers were characterized by means of X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), energy dispersive X-ray spectroscopy(EDX), Scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results reveal that the diameters of ZnO nanofibers are between 80 and 330 nm, and the AgNPs attached to the ZnO nanofibers from the heterostructure are between 5 and 100 nm in size. The photocatalytic properties of Ag/ZnO nanofibers were verified by degradation of model compounds methyl orange, methylene blue and rhodamine B, and the Ag/ZnO samples showed efficient photocatalytic activity for the degradation of simulation pollutants.



Fabrication and Mechanical Properties of Flexible γ-Al₂O₃ Nanofibrous Membranes

LI Wei, ZHAO Xiaomin, WANG Yanfeng, LU Wenjuan, JIA Yuna, JIAO Xiuling, CHEN Dairong, ZHANG Pingping

2017, 38(6):  915-921.  doi:10.7503/cjcu20160853

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Flexible γ-Al₂O₃ nanofibrous membranes were prepared by sol-gel combined electrospinning technique using aluminum chloride and aluminum isopropoxide as raw materials, water and ethanol as the solvents. The morphology and mechanical property of the membranes were characterized and the formation process was tracked. The membranes were composed of uniform nanofibers with a mean diameter of ca.188 nm. The fibers’ surfaces were smooth and the fibers were composed of nanoparticles with a size range of 15—30 nm. The prepared membranes exhibited excellent flexibility and tensile strength(1.01 MPa).



Electrospinning Fabrication and Microwave Absorption Properties of Lithium Zinc Ferrite Micro/Nanofibers

ZHAO Fang, WANG Jianjiang, XU Baocai, LIU Jiawei, GAO Haitao

2017, 38(6):  922-928.  doi:10.7503/cjcu20160846

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Spinel-type Li_0.35Zn_0.3Fe_2.35O₄ micro/nanofibers were prepared through electrospinning and calcination technique. The crystalline phase and micromorphology of the samples calcined at various temperatures(700, 800, 900 and 1000 ℃) for 2 h in air were examined by differential scanning calorimetry(DSC)-thermalgravimetric analysis(TGA), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM). Microwave absorption properties of Li_0.35Zn_0.3Fe_2.35O₄ micro/nanofibers were determined with a vector network analyzer. The results showed that pure spinel structure formed at 700 ℃ and above. As the temperature increased, Li_0.35Zn_0.3Fe_2.35O₄ exhibited micro/nanofibrous, 3D network, bamboo-like or granular morphology. The minimum reflectivity of Li_0.35Zn_0.3Fe_2.35O₄ micro/nanofibers at 700 ℃ moved to a low frequency as the matching thickness increased. The matching thickness of Li_0.35Zn_0.3Fe_2.35O₄ micro/nanofibers was 6 mm below 8 GHz, at which the microwave absorption properties were fine. The minimum reflectivity could reach -26 dB at 5.0 GHz, and the frequency band with reflectivity less than -10 dB was 4.0—8.0 GHz.



Electrospinning Preparation and Infrared-emissivity Properties of La_0.67Ba_0.33MnO₃ Micro/nanofibers

LIU Jiawei, WANG Jianjiang, ZHAO Fang, XU Baocai

2017, 38(6):  929-934.  doi:10.7503/cjcu20160845

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Perovskite-type La_0.67Ba_0.33MnO₃ micro/nanofibers were fabricated through electrospinning technology. The fibers were characterized by means of differential scanning calorimetry-thermogravimetric analysis(DSC-TGA), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). The infrared emissivity of the fibers in the temperature range of 280—370 K was tested by IR-2 infrared-emissivity analyzer. The results show that perovskite structure is formed at 600 ℃. As the temperature increases, the morphology of samples changes from fiber to three-dimensional network structure, and eventually loses the fiber morphology. The infrared emissivity of La_0.67Ba_0.33MnO₃ fibers calcined at 600 ℃ rises from 0.564 to 0.689 with the increase of temperature, which can be explained by the theory of double-exchange. The prospect of La_0.67Ba_0.33MnO₃ fibers in variable infrared-emissivity materials is promising in the future.



Application of Packed-nanofibers Solid-phase Extraction for Determination of Rhodamine B in Dry Chilli, Fruit Drink and Red Wine

WEI Lanlan, YAN Yan, KANG Xuejue

2017, 38(6):  935-941.  doi:10.7503/cjcu20160873

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A method for the determination of Rhodamine B in dry chilli, fruit drink and red wine was developed and validated. The analyte was extracted with acetonitrile from foodstuffs. A novel electrospun polymer nanofibers packed micro-column was used for cleaning and concentrating the Rhodamine B in these foodstuffs. High performance liquid chromatography with fluorescence detection(HPLC-Flu) was used for the determination of Rhodamine B in the samples. The mobile phase was composed of 3 g/L phosphate buffer and methanol(3∶7, volume ratio), the pH was adjusted to 7.0 with orthophosphoric acid. The results showed that the standard curve was linear over the validated concentrations range of 1—100 ng/mL(ng/g), and the limit of detection(LOD) for Rhodamine B spiked samples was 0.1 ng/g in dry chilli, 0.2 ng/mL in both fruit drink and red wine. The limit of quantitation(LOQ) for Rhodamine B spiked into dry chilli was 0.6 ng/g, fruit drink 0.5 ng/mL and red wine 0.5 ng/mL, respectively. The average recoveries of Rhodamine B were 98.2%—110.3% for dry chilli, 94.6%—102.2% for fruit drink, and 90.4%—104.6% for red wine, respectively. The relative standard deviation of the method was 2.3%—9.0%. This proposed method was applied to real samples including dry chilli, fruit drink as well as red wine, and there was no Rhodamine B found in fruit drink or red wine, but Rhodamine B was found in chilli powder.

Cu Doped ZnO Electrospun Nanofibers for Ethanol Detector with Broad Linear Response^†

XU Jinbao, WANG Wei, WANG Ce

2017, 38(6):  942-946.  doi:10.7503/cjcu20160892

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Saturation phenomena of sensing signal often appear when target molecular was still at a low concentration, which threatens the gas detection. Herein, Cu doped ZnO composite nanofibers were prepared via electrospinning combined with subsequent calcination, and then were characterized by XRD, XPS, SEM, TEM, and so on. The sensors based on Cu doped ZnO composite nanofibers exhibited excellent sensing performance towards ethanol vapor, when the molar ratio of Cu to Zn was 1∶60. Activated by the Cu dopant, the composite nanofibers presented high responsivity, long-term stability, rapid response and recovery(2 s/7 s). Notably, the linear range of the sensor for detecting ethanol was 5—10⁴ μg/g, which was much wider than former reports and would be helpful for gas detecting in practical applications.



Preparation of One-dimensional CNFs Supported AgX/TiO₂(X=Br, I) Ternary Composite and Their Visible Light Photocatalytic Activity

LIANG Haiou, BAI Jie, YU Dandan, ZHANG Qingyu, LI Chunping

2017, 38(6):  947-952.  doi:10.7503/cjcu20160858

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The aim of this study was to prepare a novel visible-light-driven photocatalysts AgX/TiO₂/CNFs(X=Br, I) composites. Carbon nanofibers(CNFs) which acted as a supporter were prepared via electrospinning technology and high-temperature calcination process. AgX-TiO₂/CNFs(X=Br, I) composites were prepared by combining solvothermal with chemical reaction process. The as-prepared composites were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and fourier transform infrared spectroscopy(FTIR). The photocatalytic activity of AgX-TiO₂/CNFs(X=Br, I) were researched for decomposition of methyl orange(MO) under visible light irradiation. The excellent performance were attributed to the synergistic effects between the high adsorption capacity, good conductivity of carbon nanofibers, and the extraordinary plasma effect of AgX(X=Br, I) nanoparticles. In addition, the as-prepared composites could be easily separated from the solution phase due to the large length-diameter ratio of CNFs.



Electrochemical Performance of Flexible Electrospun Carbon-MnO_x Hybrid Nanofibrous Membranes for Supercapacitors^†

PAN Chao, GU Haiteng, ZONG Feixu, GAO Jingyi

2017, 38(6):  953-958.  doi:10.7503/cjcu20160857

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Super-hydrophilic flexible MnO_x/carbon nanofibers(MnO_x/CNFs) composites were fabricated by electrospinning technique. The nanostructures of MnO_x/CNFs were proved by XRD, SEM and TEM measurements. The results confirmed that the composites possessed higher electrochemical capacitance than each individual component as supercapacitor electrode materials. The hybrid nanofibrous electrodes with 40%(mass fraction) manganese acetate(MC-4) exhibits extremely high specific capacitance of 1112.5 F/g at a current density of 1 A/g and superior cycling stability such as high capacitance retention of 93.4% at a current density of 10 A/g over 3000 charge-discharge cycles in a 2 mol/L KOH electrolyte. The enhanced electrochemical performance of the composite electrode originates from the combined effects of the two components as follows: (1) 3D superhydrophilic MnO_x/CNFs network over a relatively larger surface area reduces the difusion resistance of the electrolyte into the electrode matrix; (2) the synergistic effect between carbon and MnO_x. Carbon layer wrapped around MnO_x particles can prevent structural damage to the MnO_x during charge/discharge processes and contribute to an increased capacitance of the composite.



Anti-icing Property of Ion Liquid/PVDF Nanofibers

ZHANG Ting, WANG Chengchen, GUO Xiaoying, ZHANG Liang

2017, 38(6):  959-965.  doi:10.7503/cjcu20160874

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An electrospinning method to prepare ionic liquid(IL) incorporated poly(vinylidene ?uoride)(PVDF) nanofibers was adopted in this paper. X-ray photoelectron spectrometry(XPS), Fourier transform infrared spectrophotometer(FTIR) and X-ray diffraction(XRD) results showed that the IL which appeared on the surface of the nanofibers was miscible with PVDF, and also led to a higher content of β-phase crystal in PVDF. The IL content in the nanofibers exerted a significant impact on the surface morphology and wettability of the composite nanofibers, and thus the freezing time, crystallization temperatures of water droplets on these surfaces as well as ice adhesion strength. The results showed that the PVDF nanofibers with 10% IL presented both the highest water repellency and the best anti-icing property.



Mesoscale Simulation of a Melt Electrospinning Jet in a Periodically Changing Electric Field

SONG Qingsong, ZHANG Jingnan, LIU Yong

2017, 38(6):  966-974.  doi:10.7503/cjcu20160878

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Significant polymer chain entanglement in melt electrospinning severely impedes efforts to produce nanoscale fibers. To reduce this entanglement and improve our understanding of the motion of molecular chains, a periodically changing electric field, in which the wave is the absolute value of a sine function, was introduced in a melt electrospinning simulation system to replace the typical stable electric field. The three-dimensional path of the jet in a small straight region in the changing electric field was simulated using a dissipative particle dynamics mesoscale simulation method. The movement of the polymer chains, effect on jet diameter, and changes in the jet falling behavior at different control frequencies of the changing electric field were studied. The results show that the periodically changing electric field could increase stretching of the polymer chains and reduce the diameter of the jet effectively compared to a stable electric field. For the changing electric field, a low control frequency accelerated the falling velocity, suitable for obtaining thin fibers.



Needleless Electrospinning Method Based on Tip Effect of Conductor

CHEN Yunjun, DAI Hongchao, WANG Wei, QIANG Wei

2017, 38(6):  975-981.  doi:10.7503/cjcu20160851

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An electrospinning method was proposed based on the principle of tip effect of conductor, in which the probe array is inserted in sequence and kept perpendicularly to the bottom of the polymer solution bath, with the tips of probes close to the fluid level. When a high voltage is applied to the solution, a peak electric field will be created in the vicinity of the probes. Due to instability of the fluid in the electric field, the jet can spontaneously form at the electric field peak on the solution surface, and then it is stretched and thinned, splitting into wires and solidifying on the receiving plate. However, there is also mutual interference of the electric field between the ordered probe arrays. Simulation and optimization is needed to obtain the best spinning electric field. The geometric model was established with COMSOL Multiphysics 5.0. The effects of the length, number, spacing and geometric arrangement of the embedded probes on the peak value of the field intensity on the surface of the solution were analyzed. It is found that the convex arc-shaped geometric arrangement can increase the peak value of the field intensity when one row of probes is embedded in the solution bath, the staggered arrangement is helpful to improve the uniformity of the electric field when two rows of probes are embedded, while the effects of parallel arrangement and diagonal arrangement on the equilibrium field intensity are not obvious.



Impact Mechanism of Needleless Electrospinning Spinneret Geometry on Electric Field Distribution Regularities

WANG Wei, QIANG Wei, DAI Hongchao

2017, 38(6):  982-989.  doi:10.7503/cjcu20160849

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In the needleless electrospinning technology, the distribution and the value of electric field at spinneret are the key factors that influence the electrospinning process and the formation of nanofibers. Different geometries of the spinneret directly affect the distribution of the external electric field. Therefore, it is of practical significance for the design and optimization of needleless electrospinning spinneret through the research on the distribution of electric field from the geometry. In this paper, governing equations had been set up to analyze movement process of steady-state jet from three aspects: mass conservation, charge conservation and momentum conservation. The finite element analysis(FEA) software COMSOL Multiphysics 5.0 is used to model three needleless electrospinning spinnerets and analyze the distribution of external electric field. It is found that during the evolution from the typical cylindrical spinneret to the stepped shaft one with the added auxiliary electrodes, the distribution of electric field is influenced by the angle of the auxiliary electrodes added on both sides, plus of the number and diameters of rotary parts. The electric field is optimized step by step through a series of designs. The research is very important to the improvement of production efficiency and nanofiber quality of the needleless electrospinning equipment.



Manipulation of Native Cellulose Eletrospinning from LiCl-DMAc System

WANG Shaojun, LUO Ting, ZHANG Xiaomin, SHU You, ZHU Jin, SU Shengpei

2017, 38(6):  990-996.  doi:10.7503/cjcu20160833

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Cellulose nanofibers have been successfully fabricated by electrospinning of cellulose/lithium chloride-dimethylacetamide(LiCl-DMAc) solutions manipulated by nonsolvents. DMAc and dimethyl formamide(DMF) are used as the nonsolvents which is added into the concentrated cellulose solution. The effects of nonsolvents on the properties of cellulose solution and the morphology of electrospun cellulose nanofibers were investigated. Addition of nonsolvents is beneficial to increase the electrospinnable concentration of cellulose solution and obtain well-distributed nanofibers. The result of manipulating by DMF is better than DMAc. The improvement in electrospinnable concentration correlates well with the addition of nonsolvents which can decrease the viscosity of cellulose solution. The morphology of electrospun cellulose nanofibers is related to the rate of jet coagulation which is affected by the stability of cellulose solution during electrospinning.



Fabrication and Pressure Sensing Analysis of ZnO/PVDF Composite Microfiber Arrays by Low-voltage Near-field Electrospinning

SI Wenyan, ZHANG Hongdi, LIU Yanjie, ZHAO Aijing, ZHANG Zhiguang, GONG Maogang, ZHANG Juncheng, LONG Yunze

2017, 38(6):  997-1001.  doi:10.7503/cjcu20160847

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Parallel arrays of ZnO/polyvinylidene fluoride(PVDF) microfibers were successfully prepared by low-voltage near-field electrospinning. The ZnO/PVDF microfiber arrays were characterized by optical microscope, scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy(EDS). The average diameter of the composite fibers was about 40 μm. The EDS analysis demonstrated that ZnO nanoparticles have been doped into the parallel microfibers. Some related piezoelectric properties and electrical properties are presented in this paper. The piezoelectric properties of the ZnO/PVDF microfiber arrays are enhanced, and the mechanism is discussed briefly. These results indicate that the low-voltage near-field electrospun ZnO/PVDF composite microfibers have potential application in piezoelectric pressure sensors and nanogenerators.



Tuneable Three-dimensional Cytocompatible Micro-environments Designed by Controlled Alignment of PVDF Electrospun Fibres

JIN Lin, XU Qinwei, HU Bin, HUANG Jingbin, ZHANG Yilei, WANG Zhenling

2017, 38(6):  1002-1010.  doi:10.7503/cjcu20160832

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Three dimensional(3D) aligned electrospun fibres have a promising potential application in biomedical areas, such as biosensors, controlled drug release and tissue engineering. However, the fabrication of these fibres with tuneable microarchitectures, porosity and overall morphology still has challenges due to electrospinning process. Thus, it is highly desired to develop novel, cost-effective and easily scalable fabrication methods for the 3D aligned electrospun fibres. Herein, we developed a facile yet effective method for the preparation of 3D poly(vinylidene fluoride)(PVDF) aligned fibres(3D AFs) via an improved electrospinning technique. The obtained 3D AFs showed controllable morphology, diameter and fiber density. Furthermore, the obtained 3D AFs showed excellent in vitro biocompatibility. Moreover, the as-prepared 3D AFs enhanced cellular activities and induced directional cell growth along the direction of nanofibre orientation, thereby providing an excellent cue for the anchorage and migration of human mesenchymal stem cells(hMSCs). More importantly, cell proliferation in the 3D AFs was found to be significantly higher than that on the nanofibre mats(NFMs). Combined with controllable morphology and structure, we anticipate that this finding greatly enhances the potential applications of these 3D AFs for therapeutically relevant 3D cell cultures, tissue engineering, diagnostics and other biomedical applications.



Electric Field Simulation and Optimization on Solid-core Needles of Electrospinning Device

LIU Jian, LIU Yanbo, BUKHARI Samman hassan, REN Qian, WEI Chunhua, JIANG Xiuming

2017, 38(6):  1011-1017.  doi:10.7503/cjcu20160852

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Electrospinning is a widely used technique for nanofiber preparation at large scale that is mainly divided into two categories, namely, multi-needle and needleless categories. However, both categories have some drawbacks. For example, the capillary channels of the former can easily get jammed, while the solvent in the polymer solution storage box of the latter is liable to volatilize. A new type of solid-core needle electrospinning method was proposed and investigated to overcome the shortcomings of the current electrospinning technology. In this method, the solid-core needles with no capillary channels were used as the emitting electrodes and placed on the axis of the solution guiding rods made of insulating materials. The solution guiding rods were in close connection with the taper holes at the bottom of the solution storage box and could be moved up and down to control the solution flow. Moreover, the reciprocating up-and-down movement of the solution guiding rods can clean up the liquid feeding channels, thereby preventing the solution from coagulating and blocking the channels. Thus, the problems existing in the current electrospinning technologies, such as the needle capillary blockage in the needle electrospinning method and the rapid solvent volatilization in the solution box in the needleless electrospinning method, can be efficiently avoided. Electric field intensity simulations of the newly established electrospinning models were also performed to find the optimum structure parameters by increasing the field intensity and reducing the end effect with the help of the finite element analysis software, COMSOL. Lastly, electrospinning experiments were conducted on the newly invented electrospinning device based on the solid-core needle and non-circular gear traverse mechanism. The results indicate that this new electrospinning method could solve the complications of polymer clogging and solvent volatilization and obtain a uniform electrospinning effect.



Preparation and Electrochemical Characterization of P(VDF-HFP)/Al₂O₃/P(VDF-HFP) Membranes for LIBs by Electrospinning and Electrospraying

ZHOU Jintao, JIAO Xiaoning, YU Bin, REN Yuanlin, KANG Weimin

2017, 38(6):  1018-1024.  doi:10.7503/cjcu20160838

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A novel sandwiched composite membrane(SCM) was prepared by depositing alumina micro-particles between two layers of electrospun poly(vinylidene fluoride-co-hexafluor-opropylene)[P(VDF-HFP)] nanofibers through electrostatic spray deposition. The morphologies, thermal shrinkage, tensile properties and electrochemical properties of the separator and battery performance for cells made with the SCM were investigated. The results show a higher uptake of electrolyte for the SCM than the pure P(VDF-HFP) membrane(PHM). SCM can easily absorb the electrolyte to form gel polymer electrolytes(GPEs). The tensile strength of the SCM membrane is about 4.00 MPa when the elongation at break is 261.57%. The ionic conductivity of SCM GPEs is 1.61×10^-3 S/cm at room temperature and GPE shows a high electrochemical stability potential of 5.4 V. With LiCoCO₂ as the cathode, the cell with SCM GPEs exhibits a high initial discharge capacity of 145 mA·h·g^-1.



Preparation of Anti-layered Polyamide-66/Polyacrylonitrile/Polyethersulfone (PA-66/PAN/PES) Sandwich Structured Membrane for Air Filtration by Electrospinning

ZHANG Yingying, KANG Lijuan, HAN Zhaolian, ZHAO Shengzhe, ZHAO Xiaodong, CAO Jinshan, CHENG Zhiqiang

2017, 38(6):  1025-1032.  doi:10.7503/cjcu20160855

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A simple and effective composite fiber filter material was prepared which was composed of polyamide-66/polyacrylonitrile/polyethersulfone(PA-66/PAN/PES) fibers with layer by layer on treated stainless steal mesh(SSM). The intermediate layer of the material was dissolved in an N,N-dimethylformaide(DMF) solvent by PAN/PES. With the increase of the amount of PES under the same spinning condition, it is advantageous for the fiber dia-meter to become small and to increase the porosity of the film by the SEM and BET test. Synchronously, the mechanical properties of the films without SSM were measured(5.857 MPa) by tensile test. The surface of the filter membrane has a relatively good hydrophobic effect with contact angle(CA) of 130.58° by making use of the hydrophobicity of PES. In the case of the thickness of the sample as equal as possible, the filtration efficiency of PAN/PES-3 for the particles sized of 0.3—5 μm reached more than 99% by measuring in the actual air environment. The filtered regenerated film was observed by mechanical vibration and air backflush. In addition, we also have explored a substrate for filtered medium by using SSM which was sprayed with water spray to anti-layered.



Analytical Chemistry

Application of Octadecyl Ionic Liquid Hybrid Solid-phase Microextraction Monolithic Column in the Detection of Polycyclic Aromatic Hydrocarbons in Coffee^†

ZHANG Na, WAN Xin, SONG Xuyan, HUANG Long, ZHENG Jingjing, XING Jun

2017, 38(6):  1033-1039.  doi:10.7503/cjcu20170068

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Ionic liquid of 1-octadecyl-3-(γ-triethoxysiliconpropyl)imidazole bromide(C₁₈IL) was synthesized and then used as a functional monomer to produce the in-tube solid microextraction monolithic column(C₁₈IL in-tube SPME) via sol-gel reaction. After that, five polycyclic aromatic hydrocarbons(PAHs), naphthalene, fluorine, phenanthrene, fluoranthene and pyrene, were employed as probe analytes to evaluate the preparation method of the column and optimize the extraction conditions. Finally, a method of C₁₈IL in-tube SPME hyphen gas chromatography was established for the determination of PAHs in water. The limits of detection(LODs, S/N=3) were between 0.007 and 0.072 μg/L, and the limits of quantification(LOQs, S/N=10) varied from 0.023 to 0.24 μg/L. The intra- and inter-day relative standard deviations(RSDs) of the PAHs were below 10% except for that of phenanthrene. The proposed method was also applied to the determination of the PAHs in a coffee sample, and the recoveries for the five PHAs(spiked in the coffee sample at three levels) ranged from 85.79% to 103.42%.



Application of Surface-enhanced Raman Spectroscopy in the Fast Screening of Phosphodiesterase Type 5 Inhibitors^†

WANG Hongmei, LI Lingling, CHEN Haibin, ZENG Yongming, CHEN Hongju, CHEN Qizhen, LIN Huizhen, TIAN Zhongqun, LIU Guokun

2017, 38(6):  1040-1045.  doi:10.7503/cjcu20160710

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ing at the absence of a fast and effective screening technique facing the prevalence of the illegal adulterant of Phosphodiesterase type 5(PDE-5) inhibitor in health products, a non-designated detection platform based on surface-enhanced Raman spectroscopy(SERS) was proposed. Integrated with a simple pretreatment process in 3—5 min, SERS measurement was carried out on those suspicious health product samples with the lowest detectable concentration at a level of 0.05 mg/kg. The advantages of short time and high sensitivity satisfy the urgent demand of the fast screening and on-site inspection of the authorities.



Organic Chemistry

Absolute Configuration Determination of Two Drimane Sesquiterpenoids from the Endophytic Fungi Talaromyces Purpureogenus of Panax notoginseng^†

ZHANG Bingyang, MA Yangyang, GUO Hua, ZHU Huajie, LI Wan

2017, 38(6):  1046-1051.  doi:10.7503/cjcu20170006

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Two drimane sesquiterpenoids(1, 2) were isolated from cultures of the fungus Talaromyces purpureogenus. The planar structures were well established by NMR and mass spectrometry, and the absolute configurations(AC) were determined by comparing experimental electronic circular dichroism(ECD) and optical rotation(OR) of compounds 1 and 2 with the calculated ECD and OR data using quantum methods. Compounds 1 and 2 were evaluated for antibacterial activities against four spices of pathogenic bacteria, and the results showed that compound 1 had weak antibacterial activities against Escherichia coli(MIC=25 μmol/L).



Efficient Oxidation of Thiols to Corresponding Disulfides Catalyzed by Hemin^†

GE Weiwei, CHEN Jing, ZONG Liang, LI Jian, SUI Shaohui, WU Weihui, ZHANG Ming, DONG Junjun

2017, 38(6):  1052-1058.  doi:10.7503/cjcu20160940

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Hemin was used as a catalyst for the oxidation of thiols to corresponding disulfides. The addition of N,N-diisopropylethylamine(DIEA) can enhance the hemin catalytic activity and decrease the hemin self-oxidative degradation during the catalytic process. The methyl thioglycolate was quickly oxidized to corresponding disulfide product(completed 90% in 20 min) in the presence of 1/4 hemin in aqueous solution(pH=8.0) and DIEA involved in the reaction as an axial ligand. The oxidation was carried out at room temperature(ca. 20 ℃) under atmosphere condition. And this catalytic system was also successfully applied in disulfide bond formation in peptide synthesis. Oxytocin and linaclotide were used as model peptide. Compared with conventional oxidation reagents, the notable feature of this catalytic system is green and efficient, which provides an alternative way to formating disulfide bond in peptide synthesis.



Design, Synthesis and Biological Evaluation of Thrombin Inhibitors with 1,2,3,4-Tetrahydrobenzo[4,5]imidazo[1,2-a]pyrazine Nucleus^†

CHEN Dongxing, SHI Jinyu, CHEN Qiufang, ZHANG Rui, GONG Guoqing, XU Yungen, ZHU Qihua

2017, 38(6):  1059-1067.  doi:10.7503/cjcu20160797

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Compound 1, a new thrombin inhibitor with 1,2,3,4-tetrahydrobenzo[4,5] imidazo[1,2-a]pyrazine nucleus, was selected as lead compound, and fourteen carbamate derivatives derivatives(2a—6a, 2b—6b, 7—10) were designed and prepared. Furthermore, a twin drug(11) was synthesized by coupling compound 1 with 2-hydroxymethyl-3,5,6-trimethylpyrazine(HTMP). The structures of all the target compounds were confirmed by ¹H NMR, ¹³C NMR and HRMS. Preliminary biological activity test results indicated that all of the tested compounds exhibit a certain degree of inhibitory effect on thrombin-induced platelet aggregation, among which compound 4b[IC₅₀=(0.11±0.08) μmol/L] show better anti-platelet aggregation activity than dabigatran etexilate[IC₅₀=(0.60±0.05) μmol/L]. The in vivo experimental results in rat venous thrombosis model demonstrated compound 4b can significantly reduce thrombosis in a dose-response manner. Compound 11, which showed weak inhibitory effect on thrombin-induced platelet aggregation, also displayed comparable inhibitory effect on rat venous thrombosis with dabigatran etexilate. The study points out that the enhanced potency of compound 11 may be the synergetic effect of HTMP and compound 1 which are generated by hydrolysis in vivo.



Physical Chemistry

Investigation on the Hydrogen Bonding Interaction Between Amino Acid Side Chains and Base Pairs Containing Oxidized Guanine^†

HAN Bingyu, LI Yue, LIU Cui

2017, 38(6):  1068-1075.  doi:10.7503/cjcu20160952

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The hydrogen bond energy, geometry, charge distribution and second order stabilization energy of complexes oxidized base pair(8-oxo-G∶C) and Amino acid side chains were investigated via quantum chemistry in gas phase and aqueous solution. The results show that the hydrogen bond strength has been weakened in aqueous solution, the charge has been obviously affected by aqueous solution, the charge variation of forming hydrogen bond sites under aqueous solution is about 10 times as much as under gas phase and the geometry has slight change. Therefore the interaction between enzyme and DNA must be studied in aqueous solution. The aqueous solution has a great influence on the hydrogen bond strength between 8-oxo-G∶C and amino acid side chains in charged complexes, which has been weakened by 69.23 kJ/mol in average. The hydrogen bond strength between 8-oxo-G∶C and amino acid side chains in uncharged complexes has only been weakened by 3.60 kJ/mol in average. The side chain with or without charge has little effect on the hydrogen bond strength between 8-oxo-G and C in complexes in aqueous solution and the hydrogen bond strengths of charged complexes and uncharged complexes have been weakened by 24.57 and 30.05 kJ/mol, respectively. The higher the second-order stabilization energy, the shorter the length of the corresponding hydrogen bonds.



Co-effect of L-Cysteine Self-assembled Monolayers and Mixed Solvents on Chiral Separation of DL-glutamic Acid^†

ZHOU Xinhui, WANG Haishui

2017, 38(6):  1076-1081.  doi:10.7503/cjcu20160866

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In general, crystallization of a racemic glutamic acid aqueous solution will yield optically inactive racemic compound crystals(DL-crystals), it makes a great challenge to chiral separation of DL-glutamic acid. We found that D-crystals and L-crystals(the conglomerates) of glutamic acid can be deposited from the mixed solvents of water and ethanol, providing an opportunity to separate the D- and L-forms of glutamic acid. Moreover, L-cysteine self-assembled monolayers(L-Cys SAMs) on the gold(111) surface showed chiral discriminating ability in the mixed solvents. SEM, XRD and Raman techniques were employed to characterize the crystals grown on the L-Cys SAMs. The relative contents of L-forms and D-forms in the conglomerates were measured by a pre-column derivatization HPLC method. The experimental results demonstrated that the conglomerates with D-glutamic acid excess were obtained on the L-Cys SAMs from a 60%(volume fraction) ethanol-water mixed solvent. And more importantly, the pure D-crystals alone can be deposited from the mixed solvents by the co-effect of L-Cys SAMs and mixed solvents and a typical “in-series enriched method”.



Water Soluble Polyoxometalate-based Photocatalytic Fuel Cell^†

WU Weibing, LI Jian, LIU Congmin, ZHANG Lei, DAI Hongqi, LIU Wei

2017, 38(6):  1082-1089.  doi:10.7503/cjcu20160796

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A novel photocatalytic fuel cell using water soluble polyoxometalates(POM) as photocatalyst and charge carrier was built. The fuel oxidation in this study is a homogeneous decomposition reaction that occurred in electrolyte solution and the cell could generate electricity in dark. Using bio-glycerols as fuels, the power density of the photocatalytic fuel cell could reach 0.24 mW/cm². The cell worked steadily for nearly 50 h with current above 0.75 mA under continuous irradiation. Theoretically, the glycerol fuel can be either partially converted to aldehydes and acids, or fully converted to CO_x, depending on the degree of the oxidization reactions. Ultimately, this novel photoactivated hybrid fuel cell could expand fuel supply and utilization.



Polymer Chemistry

Preparation and Electrochromic Properties of Nano Cellulose/Poly(3,4-ethylenedioxythiophene) Composite Films^†

ZHANG Sihang, HE Yongfeng, FU Runfang, JIANG Jie, LI Qingbi, GU Yingchun, CHEN Sheng

2017, 38(6):  1090-1098.  doi:10.7503/cjcu20160904

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Nano biomaterials based on renewable resources have been of growing interest due to the recent advances in the field of nano technological applications. Nano cellulose(NC) was extracted by swelling cotton pulp, following with the ultrasonic treatment. The composites of poly(3,4-ethylenedioxythiophene)(PEDOT) with NC inclusions at different loadings were prepared using in situ polymerization with ammonium peroxydisulfate(APS) as oxidant in nanocellulose aqueous suspension. NC and NC/PEDOT composites were characterized. The thin composite films were obtained by drop-coating the composites aqueous suspension to the surface of ITO conducting glass. The results showed that the original NC was rod-like, with average diameter of 20 nm and length range from 100 nm to 300 nm. The NC/PEDOT composites were core-shell structure with average diameter of about 30 nm and PEDOT was uniformly coated on the surface of NC. The electrochromic properties of NC/PEDOT composite films with different NC contents were studied by electrochemical test and spectrophotometery. The NC/PEDOT composite film containing 60% NC showed the highest contrast ratio of 24.4%, the shortest response time of 1 s, and the highest coloration efficiency of 51.8 cm²/C.



Preparation and Properties of Cellulose Benzoate and Preliminary Exploration About Cellulose Benzoate-g-polyoxyethylene(2) Hexadecyl Ether^†

HAN Na, WANG Xiufang, QU Tingsi, QIAN Yongqiang, LU Yahong

2017, 38(6):  1099-1106.  doi:10.7503/cjcu20160816

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Cellulose benzoate(CB) was prepared with microcrystalline cellulose(degree polymerization, DP=220) and benzoyl chloride(BC) as the raw materials. The ionic liquid 1-allyl-3-methyl imidazole chloride([Amim] Cl) and 1-ethyl-3-methyl imidazole acetate([Emim]Ac)/N,N-dimethyl acetamide were used as the solvent respectively. The effects on the degrees of substitution and solubility as well as melting property have been explored in different solvents, different reaction temperatures and different molar ratios. The results showed that the solubility and melting performance as well as the degrees of substitution(0.13—2.98) of the products were improved, with the increases of reaction temperatures(60—80 ℃) and the molar ratios of benzoyl chloride(3∶1—9∶1) in [Amim]Cl, by ¹H NMR, FTIR, DSC, TG and thermal stage microscope. The grafting degrees of substitution of benzoyl were low, and the acetyl was introduced in copolymer when [Emim]Ac/DMAc was used as the solvent. It was demonstrated the dissolution system is not suitable for the reaction of cellulose grafting benzoyl chloride. Preliminary exploration has been carried out to synthesize BC-g-polyoxyethylene(2) hexadecyl ether solid-solid phase change material(CB-g-E₂C₁₆) in the [Amim]Cl. The results showed that the phase transition temperatures and enthalpy of phase change of CB-g-E₂C₁₆ were 12.7—29.1 ℃and 12—24 J/g, respectively. The thermostability was 294 ℃. It laid a certain foundation for subsequent detailed exploration about the performances of the cellulose based phase change materials.