Table of Content

10 August 2019, Volume 40 Issue 8

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Cover and Content of Chemical Journal of Chinese Universities Vol.40 No.8(2019)

2019, 40(8):  0-0. 

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Articles: Inorganic Chemistry

Microwave-assisted Hydrothermal Synthesis of Carbon Dots Based on Tyrosine and Their Application in Ion Detection and Bioimaging

HUANG He, LI Chunguang, SHI Zhan, FENG Shouhua

2019, 40(8):  1579-1585.  doi:10.7503/cjcu20190076

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Cabon dots(CDs) were synthesized utilizing tyrosine as carbon source, ethanediamine as passivant through a green microwave-assisted hydrothermal way. The size of CDs can be adjusted by the dose of ethanediamine. The as-prepared CDs have uniform size and good dispersibility, showing blue or green fluorescence. The as-prepared CDs can change their fluorescence(from blue to yellow) by changing the excitation light and the emission light can be kept without large decay. The as-synthesized CDs have good selectivity on the detection of Fe³⁺ with a limit of detection(LOD) of 0.82 nmol/L, and a detection limit of 2.98 nmol/L. The as-synthesized CDs also have great biocompatibility and low biotoxicity, and can be utilized as a probe to label AD293 cells, marking the cytoplasm of the cells.



Mesoporous-structure Enhanced Photothermal Effect of Fe₃O₄ Superparticles@mesoporous Silica

WANG Xiaohui, WANG Kexin, LIU Junping, HONG Xia

2019, 40(8):  1586-1592.  doi:10.7503/cjcu20180832

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Fe₃O₄ superparticles@mesoporous SiO₂(Fe₃O₄SPs@mSiO₂) were synthesized by the wet chemical method. The nanocomposites exhibited superparamagnetic property. They can rapidly accumulate near a commercial permanent magnet and redisperse in the aqueous solution with gently shaking. The absorption of Fe₃O₄SPs@mSiO₂ in the near-infrared region was increased due to the coating of SiO₂. And thus, their photothermal effect was improved. The construction of mesoporous structure facilitated to raise the utilization of near-infrared light, resulting in a further improvement of the photothermal performance of the nanocomposites. Moreover, the thicker the shell of the mesoporous SiO₂ was, the superior the photothermal effect of the nanocomposites became. The vitro cell experiments confirmed that Fe₃O₄SPs@mSiO₂ can effectively kill the cancer cells under the near infrared light irradiation.



Analytical Chemistry

Luminescent Nanoswitch Based on Carbon Dots for Sensitive Detection of Cu(Ⅱ) Ions and Pyrophosphates

ZHOU Sihui, LI Qiong, ZHANG Ting, PANG Daiwen, TANG Hongwu

2019, 40(8):  1593-1599.  doi:10.7503/cjcu20190243

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Carbon dots(CDs) with brightly red fluorescence were prepared via a facile one-step synthesis way by hydroxyl and amino groups to react at high temperature. The as-obtained CDs can overcome the excitation-dependence luminescence behavior for normal routes and the quantum yield is up to 41%. Based on the fluorescent materials, a luminescent nanoswitch through fluorescence on and off in response to specific external stimuli was designed. Fluorescence quenching of CDs by Cu²⁺ is ascribed to the complexation reaction. When pyrophosphate(PPi) is introduced into the system, Cu²⁺ leaves CDs' surface because PPi binds to CDs much stronger than Cu²⁺, resulting in the fluorescence recovery. Following the proposed way, a signal off-on nanoswich sensing system for the detection of Cu²⁺ and PPi with high selectivity and sensitivity was constructed, and the detection limits for Cu²⁺ and PPi are 2.14 μmol/L and 1.85 μmol/L, respectively. This method has been applied in real samples, and this strategy broadens the sensing application of fluorescent CDs, providing the possibility to determine these targets in living systems.



Wavelength Drift Correction Method Based on Energy Redistribution

YU Bingwen, JIN Wei, JIN Qinhan, LIU Xu, LI Xiaodong

2019, 40(8):  1600-1605.  doi:10.7503/cjcu20190144

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In the field of atomic spectral analysis, wavelength stability has a great influence on the results of qualitative and quantitative analysis. In order to solve the problem of wavelength drift, an algorithm for implementing wavelength drift correction based on energy redistribution principle was proposed. The energy density distribution was estimated with a modified parabolic interpolation method, the optimal offset was determined by making use of the similarity of the spectra as the indicator, and then the spectral intensity was recalculated according to the optimal offset and energy density distribution, finally sub-pixel level wavelength drift correction was achieved. The proposed algorithm was verified with spectral data obtained from fiber optic spectrometer and sequential scanning spectrometer. As a result, the background noise of Eu is reduced to about 48% and the signal stability of Mo is improved from 20% to 5%. This algorithm is very suitable for the spectra with structured features, and it will help to improve the accuracy of atomic spectral analysis without peak-searching algorithm.



Mechanism of Electrochemical Capture of CO₂ via Redox Cycle of 2-Amino-3-chloro-1,4-naphthoquinone in BMIMBF₄

QIAO Xuejiao, LI Dan, CHENG Longjiu, JIN Baokang

2019, 40(8):  1606-1613.  doi:10.7503/cjcu20190096

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The mechanism of electrochemical capture of CO₂ via redox cycle of 2-amino-3-chloro-1,4-naphthoquinone(ACNQ) in 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF₄) was investigated by cyclic voltammetry(CV) and in-situ Fourier transform infrared(FTIR) spectroelectrochemistry techniques. In the absence of CO₂, ACNQ undergoes a reversible two-step one-electron process in BMIMBF₄. The dianion(ACNQ^2-) formed during electrochemical reduction can be used as nucleophiles to attack the eletrophilic carbon center of CO₂ and form a stable CO₂ adduct when CO₂ is introduced. Furthermore, the stoichiometry of CO₂ electrochemical capture was evaluated. The result indicates that 1 mol of ACNQ^2- can capture 1 mol of CO₂. Also, the possible structures of CO₂ adducts in the reaction were calculated by the B3LYP method at the 6-311++G^** level.



Chemical Transformation of Raw and Fermented Ziziphi Spinosae Semen Analyzed by UPLC-Q-Orbitrap MS/MS

DU Chenhui, LI Ze, CUI Xiaofang, ZHANG Min, PEI Xiangping, ZHAN Haixian, YAN Yan

2019, 40(8):  1614-1620.  doi:10.7503/cjcu20190055

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To elucidate the fermentation-induced chemical transformation mechanisms of secondary metabolites, the chemical difference between raw and fermented Ziziphi Spinosae Semen(SZR) using Poria cocos (Schw.) Wolf was revealed by integrating UPLC-Q-Orbitrap MS/MS techniques-based untargeted metabolomics. 24 chemical components were characterized in fermented Ziziphi Spinosae Semen(FSZR). The 7 differential marker compounds between SZR and FSZR were rapidly discovered by untargeted chemomics-based mining approach using OPLS-DA. Meanwhile, the relative contents of 24 chemical components were analyzed by t-Test, which was used to make metabolic pathway analysis, showing that deacetylate and deglycosylation were the major metabolic reaction under fermentation by Poria cocos. The result shows that the proposed strategy meets the technical demands for the overall chemical characterization of fermented herbal medicines, and therefore may be considered a promising approach for delving into the scientific basis in traditional fermentation of herbal medicines.



Simultaneous Detection of Mercury, Lead and Strontium Ions Based on Conformational Conversion Sensor ^†

ZHOU Yuting, TANG Yujiao, SHAO Shuang, DAI Shiyan, CHENG Guifang, HE Pingang, FANG Yuzhi

2019, 40(8):  1621-1627.  doi:10.7503/cjcu20180868

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A high-sensitive and specific electrochemical biosensor was designed for simultaneous detection of mercury ion(Hg ²⁺), lead ion(Pb ²⁺) and strontium ion(Sr ²⁺) by oligonucleotide conformational transformation. The biosensor was based on porous anodic alumina(PAA) modified with two oligonucleotide aptamers which could capture Hg ²⁺, Pb ²⁺ and Sr ²⁺, respectively. The aptamers can block [Fe(CN)₆] ^3-/4- ion conduction in the nanochannels of PAA. In the presence of Hg ²⁺, Pb ²⁺ and Sr ²⁺, the aptamers could bend and wrap around those metal ions to make the nanochannel unobstructed, and then, the redox current of [Fe(CN)₆] ^3-/4- could be increased. When the biosensor eluted with β-mercaptoethanol(βME), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid(DOTA) and kryptofix 222(KP) successively, the aptamers stretched and released Hg ²⁺, Pb ²⁺ and Sr ²⁺ in sequence, leading to the re-blockage of nanochannel with the decrease of the redox current. The calibration curves of Hg ²⁺, Pb ²⁺ and Sr ²⁺ were obtained in the range of 0.05—2.50 nmol/L, and the detection limits were 0.013, 0.017 and 0.022 nmol/L, respectively. Furthermore, the biosensor is easily constructed, stable and reusable. It is hopeful to apply in the daily monitoring of harmful metal ions in drinking water or environmental water.



Organic Chemistry

Application of Two Chiral BINOL Polymers in Asymmetric Epoxidation Reaction ^†

LIU Feng, LI Qinfang, OUYANG Kunbing, YANG Nianfa

2019, 40(8):  1628-1636.  doi:10.7503/cjcu20190141

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Two chiral polymers based on binaphthol(BINOL) were synthesized. The polymer can be used as a chiral inducer to coordinate with ZnEt₂ to form a recoverable self-supporting catalyst, which could be used in the asymmetric catalytic reaction of α,β-unsaturated ketones. The target products of high yield and good enantioselectivity(e.e. value up to 99%) can be obtained under mild conditions. The catalytic activity was not reduced significantly after 4 or 5 cycles of recovery of the recovered polymers.



Selenium-catalyzed Carbonylation to 1,3,4-Thiadiazol-2-ylcarbamates

ZHANG Xiaopeng, NIU Xueli, GAO Hemei, FAN Xuesen, ZHANG Guisheng

2019, 40(8):  1637-1642.  doi:10.7503/cjcu20190069

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1,3,4-Thiadiazol-2-ylcarbamates are an important class of heterocyclic compounds with remarkable medical and agromedical applications due to their pharmacological and biological activities such as antimicrobial, antibacterial, and analgesic effects as well as protein kinase CK2 and acetohydroxy acid synthase inhibition effects. In order to develop an economical, eco-friendly and convenient approach to these target compounds, herein, a facile one-pot selenium-catalyzed carbonylation protocol was studied. The optimal reaction conditions were obtained through investigating the effects of main factors on the carbonylation reaction such as reaction temperature, ethanol dosage, pressure and kind of bases. With cheap and readily available nonmetal selenium as the catalyst, carbon monoxide instead of virulent phosgene as the carbonylation reagent, oxygen as the oxidant, the selenium-catalyzed oxidative carbonylation reaction of 1,3,4-thiadiazol-2-amine proceeded smoothly with a series of alcohols especially with those less hindered ones under the optimized conditions in one-pot manner, affording the corresponding products 1,3,4-thiadiazol-2-ylcarbamates in moderate to good yields. Thus, a new economical, eco-friendly and convenient approach to 1,3,4-thiadiazol-2-ylcarbamates featured with simple and readily available catalyst and raw materials, low cost, high atomic economy, one-pot and phosgene-free manners, and no emission of corrosive wastes has been developed. The probable reaction mechanism was also proposed at the end of this paper.



Structural Characterization of Peptide Calcium Chelate VGLPNSR-Ca and Its Calcium Absorption Ability in Caco-2 Cell Monolayer

LIU Bingtong, ZHUANG Yongliang

2019, 40(8):  1643-1648.  doi:10.7503/cjcu20190064

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The peptide calcium chelate VGLPNSR-Ca was prepared from Val-Gly-Leu-Pro-Asn-Ser-Arg(VGLPNSR) and calcium chloride. The structure of VGLPNSR-Ca was analyzed by means of UV spectroscopy, X-ray diffraction(XRD), scanning electron microscopy(SEM), Fourier tranform infrared spectroscopy(FTIR) and mass spectrometry. The calcium absorbing ability of VGLPNSR-Ca in the intestine was studied by Caco-2 cell monolayer model in vitro. According to the results of UV, XRD and SEM, VGLPNSR-Ca was formed as a stable compound. FTIR analysis indicated that the chelation sites of VGLPNSR-Ca were mainly the nitrogen atom of the amino group and the oxygen atom of the carboxyl group. Combined with LC-MS/MS, the chelation reaction of VGLPNSR with calcium ions was mainly involved in the nitrogen terminal of Val, the carbon terminal of Arg and the amino acid Asn. Based on the above results and analyses, the molecular structure of VGLPNSR-Ca was predicted. In addition, the calcium absorption rate of VGLPNSR-Ca in Caco-2 cell monolayer was 31.97%, twice as high as calcium absorption of calcium chloride, proving that VGLPNSR-Ca can effectively improve the bioavailability of calcium.



Physical Chemistry

Theoretical Studies of the Potential Energy Surface and Rovibrational Spectra for Kr-C₂H₂

BAI Xu, HAN Chaoying, ZHU Hua

2019, 40(8):  1649-1654.  doi:10.7503/cjcu20190254

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A new four-dimensional(4D) potential energy surface(PES) for the Kr-C₂H₂ complex including the Q₁ and Q₃ normal modes for the ν₁ symmetric stretching vibration and ν₃ antisymmetric stretching vibration of C₂H₂ was studied. The PES was calculated at the coupled-cluster singles and doubles with noniterative inclusion of connected triples[CCSD(T)] -F12 level with augmented correlation-consistent polarized-valence quadruplet-zeta(aug-cc-pVTZ) basis set plus the midpoint bond function(3s3p2d1f1g). Two averaged vibrational potential energy surfaces of C₂H₂ at both the vibrational ground and (ν₁,ν₃)=(1,1) excited states were generated from the integration of the four-dimensional potential over the Q₁ and Q₃ coordinates. The averaged potential energy surfaces have two equivalent T-shaped global minima, two equivalent local linear minima as well as three saddle points between the minima. The global minima are located at R=0.41 nm and θ=65.6°/114.4° with a well depth of 151.88 cm^-1. The radial discrete variable representation(DVR)/angular finite basis representation(FBR) method and Lanczos algorithm were employed to calculate the rovibrational energy levels and bound states. The calculated vibrational band origin for the Kr-C₂H₂ complex is red shifted by -1.48 cm^-1, which is closed to the observed value of -1.38 cm^-1. The infrared spectra agree well with the experiment data. The good agreement with the experiment values verifies the high quality of ab initio PESs.



Syntheses of MIL-53 MOFs Materials and Their Catalytic Properties in Strecker Reactions

WANG Pengcheng, SHAN Liang, FAN Yong, WANG Li, XU Jianing, WU Shujie

2019, 40(8):  1655-1661.  doi:10.7503/cjcu20190201

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Four metal organic frameworks(MOFs), NH₂-MIL-53(Sc), NH₂-MIL-53(Al), MIL-53(Sc) and NO₂-MIL-53(Sc), were synthesized via changing the metal center and functional group of ligand, hereafter, their catalytic performance in the formation of α-aminonitrile(donated Strecker reaction) was investigated. Noteworthy, it is shown that the reusable NH₂-MIL-53(Sc) shows very good catalytic performance for Strecker reaction. Hereafter, comparing the catalytic experiments between NH₂-MIL-53(Sc) and NH₂-MIL-53(Al), the influence of metal ion radius and unsaturated coordination metal sites on Strecker reaction were analyzed. Furthermore, in comparison with the catalytic effects between NH₂-MIL-53(Sc) and MIL-53(Sc), the results demonstrated that the amino group can be served as the Lewis base sites, which can promote Strecker reaction through Lewis acid and Lewis base bifunctional synergistic mechanism. In addition, comparing the catalytic performances between NO₂-MIL-53(Sc) and MIL-53(Sc), it is confirmed that the NO₂ group on the catalyst structure has an important influence on the Strecker reaction. Finally, in comparison with the catalytic effects among NH₂-MIL-53(Sc), scandium nitrate and 2-aminoterephthalic acid(ATA) ligand, it is concluded that the nanoscale pore structure of NH₂-MIL-53(Sc) is the key factor to improve the selectivity of product in Strecker reaction.



Preparation and Catalytic Activity of Graphene Supported Pt/Co Nanoparticles for Hydrogen Generation from KBH₄

LI Xiaoli, HUANG Liang, DUAN Hongjuan, ZHANG Li, ZHANG Haijun

2019, 40(8):  1662-1669.  doi:10.7503/cjcu20190165

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Graphene supported Pt/Co bimetallic nanoparticles(GBNPS) were prepared using a chemical co-reduction method. The obtained GBNPS were characterized by transmission electron microscope(TEM), high-resolution transmission electron microscopy(HRTEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). The effects of metal compositions on the hydrolysis reaction of the alkaline KBH₄ solution were studied. The results indicated that the average particle size of GBNPS was from 3.2 nm to 3.9 nm. Pt₂₀Co₈₀ GBNPS displayed the highest catalytic activity, showing a high hydrogen release rate of 35973.35 mol_H2·h^-1·mol^-1_Pt at 35℃. Pt₂₀Co₈₀ GBNPS showed the corresponding apparent activation energy of 36 kJ/mol for the hydrolysis of an alkaline KBH₄.



K Promoted Nanosheets-like Hydrotalcite-derived CoAlO Metal Oxides for Catalytic Soot Combustion

REN Wei, TIAN Ye, XING Lingli, YANG Yuexi, DING Tong, LI Xingang

2019, 40(8):  1670-1678.  doi:10.7503/cjcu20190161

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We synthesize the K supported nanosheets-like hydrotalcite-derived CoAlO metal oxide by a facile hydrothermal method, which exhibits the superior catalytic performance for soot combustion. The H₂-TPR results show that the interaction between K and Co leads to the improved redox ability of 5K/CoAlO. The Co_2p XPS results show that the Co²⁺/Co³⁺ ratios get increased after loading K on the CoAlO support. It demonstrates that the K loading promotes the transition of cobalt species from Co³⁺ to Co²⁺, which leads to the generation of oxygen vacancies. The O_1s XPS results show that the O_ads/(O_ads + O_lat) ratio increases after K loading. The soot-TPR results indicate that the interaction between K and Co contributes to the adsorption of gaseous O₂ remarkably. During kinetic experiments, 5K/CoAlO exhibits the high reaction rate per unit mass of catalyst, active oxygen(O^*) amount per unit mass of catalyst and TOF, which demonstrates that the interaction between K and Co improves the intrinsic activities of 5K/CoAlO. In addition, owing to the nanosheets-like morphology of 5K/CoAlO, the soot particulates could be highly dispersed on the nanosheets-like layers of 5K/CoAlO and get more access to active components, which is favorable to soot combustion. In summary, the improved amount of active oxygen species and the increased soot-catalyst contact efficiency guarantee the high soot combustion activity of our K supported CoAlO catalysts. Our work provides a novel approach to designing a highly efficient Co-based hydrotalcite-derived oxides catalyst for catalytic soot combustion.



Ground Structure and Excited State Proton Transfer Reaction of 2-Aminobenzothiazole

WEI Xin, DENG Yaoliang, ZHENG Xuming, ZHAO Yanying

2019, 40(8):  1679-1685.  doi:10.7503/cjcu20190112

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The ground state structure of 2-aminobenzothiazole(ABT) dimer was studied in solid and different solvents by Fourier transform infrared spectroscopy(FTIR), Raman spectra combined with density functional theory(DFT). Raman spectrum difference between dimer and solvent molecule in different proton solvents was explained by the hydrogen bonding interaction. Electron spectroscopic experiments further revealed the photophysical and photochemical reactions of dimers. Ultraviolet absorption and fluorescence emission spectra showed that the solvent and pH value may control the decay of higher excited states and excited state proton transfer process. Time-dependent density functional theory(TD-DFT) calculations explained the phenomenon of double fluorescence and explored initially the mechanism of double proton transfer in the excited state.



Preparation of Ni-Al₂O₃ Catalysts Derived from Hydrotalcite and Its Catalytic Performance for Hydrogenation of Levulinic Acid

ZHANG Yin, GUO Jianjian, WANG Jie, LI Haitao, ZHAO Yongxiang

2019, 40(8):  1686-1696.  doi:10.7503/cjcu20190068

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A series of Ni-Al₂O₃ catalysts with different Ni/Al molar ratios was prepared using NiAl-NO₃-LDH as precursors and characterized by means of N₂-physical adsorption, ICP-OES, TG/DTG, XRD, XPS, H₂-TPR/TPD and NH₃-TPD techniques. The catalytic performance of these catalysts for liquid phase hydrogenation of levulinic acid was valuated. The results demonstrated that with the increasing of Ni/Al molar ratio, isolated γ-AlOOH species evolved dissociative Ni(OH)₂ which existed in the hydrotalcite-like laminate structure, the interaction between metal-support in catalyst become weaker, the dispersion of Ni species decreased, surface acidic sites increased first and then decreased. When Ni/Al molar ratio is 3, the catalyst had the most abundant acidic and hydrogenation sites and exhibited the high performance for the hydrogenation of levulinic acid to γ-valerolactone. 92.7% yield of γ-valerolactone was obtained under the condition of 160℃, 4 MPa H₂ pressure.



Effect of Amphiphilic Quaternary Ammonium Salt Additive on Performance and Stability of Perovskite Solar Cells

JIANG Yefang, DONG Ru, CAI Xuediao, FENG Jiangshan, LIU Zhike, LIU Shengzhong

2019, 40(8):  1697-1705.  doi:10.7503/cjcu20190024

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Amphiphilic hexadecyl trimethyl ammonium bromide(CTMAB) as additive was introduced into a CH₃NH₃PbI₃ pervoskite precursor to adjust the morphology and crystallinity of perovskite layers during the film formation process. SEM and AFM images showed that the perovskite films with CTMAB present more uniform and better coverage compared with perovskite film without CTMAB. As a result, perovskite films with CTMAB exhibit favorable morphology and improved crystallinity and power conversion efficiency(PCE). The perfor-mance of CH₃NH₃PbI₃ based on perovskite solar cell with optimized CTMAB content achieved a summit PCE of 18.03% with photovoltage(V_oc) of 1.055 V, short circuit current density(J_sc) of 22.37 mA/cm², and fill factor(FF) of 76.37% under standard AM 1.5 solar light of 100 mW/cm² intensites. More importantly, the perovskite device with CTMAB into perovskite layer showed good stability under humidity environment during 40 d.



Two-step Preparation of Trazodone and Its Corrosion Inhibition Mechanism for Carbon Steel

MA Yucong, FAN Baomin, WANG Manman, YANG Biao, HAO Hua, SUN Hui, ZHANG Huijuan

2019, 40(8):  1706-1716.  doi:10.7503/cjcu20190017

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Trazodone(TZD) was prepared via a two-step method taking 3-chloroaniline, 2,2'-[(3-chloropropyl)azanediyl] diethanol and 1,2,4-triazolo[4,3-a] pyridin-3(2H)-one as raw materials. The corrosion inhibition effect of TZD for 20# mild steel in 0.5 mol/L hydrochloric acid solution was evaluated through mass loss method, potentiodynamic polarization and electrochemical impedance spectroscopy. The inhibition mechanism was also revealed by virtue of scanning electron microscopy(SEM), atomic force microscopy(ATM), attenuated total reflection infrared spectroscopy and adsorption activation parameters. The results indicated that the corrosion inhibition efficiency increased with increase of TZD concentration and decreased with increase of temperature, which could reach 95.8% at a dosage of 6 mmol/L under 298 K. TZD could spontaneously adsorb on the steel surface with the exothermic property, which obeyed Langmuir adsorption isotherm. The adsorption of TZD on the steel surface could depress the cathodic and anodic reactions accompanied with an enhancement of interfacial polarization resistance. TZD was inclined to parallelly adsorb on the steel surface based on theoretical calculations.



Effect of Mo on the Skeleton Structure and Hydrogen Evolution Performance of Ni-Mo Alloys Electrode Prepared by De-alloying

ZHOU Qi, LI Zhiyang, WANG Fan

2019, 40(8):  1717-1725.  doi:10.7503/cjcu20180492

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Nanoporous Ni-Mo alloys with different Mo contents were prepared by rapid solidification and dealloying. The phase, morphology and pore size distribution of porous electrode materials were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and N₂ adsorption-desorption analysis. The electrocatalytic hydrogen evolution of porous electrode was tested by linear sweep voltammetry, Tafel slope, alternate current impedance and cyclic voltammetry. The results show that the hydrogen evolution overpotential of the prepared porous electrode material decreases first and then increases with the increase of Mo content at a current density of 50 mA/cm². The hydrogen evolution activity of Ni_2.5Mo_2.5 alloy is the highest, and the hydrogen evolution process on it is controlled by Volmer-Heyrovsky step. The apparent exchange current density of Ni_2.5Mo_2.5 alloy electrode is 0.29 mA/cm². After 1000 cycles of cyclic voltammetry, the polarization curve remains basically the same, and over potential increased only by 3.67% under a current density of 50 mA/cm², showing excellent hydrogen evolution stability.



Polymer Chemistry

Preparation and Properties of Polypyrrole Modified Layered Clay/poly(ε-caprolactone) Antibacterial Nanocomposites

MAO Long, LIU Yuejun, FAN Shuhong

2019, 40(8):  1726-1732.  doi:10.7503/cjcu20190120

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Polypyrrole-coated layered double hydroxides(LDHs@PPy) was prepared by the chemical oxidation polymerization of pyrrole(Py) on the surface of LDHs induced by Fe³⁺. And LDHs@PPy/poly(ε-caprolactone)(PCL) nanocomposites were prepared by blending LDHs@PPy and pure PCL via solution casting method to obtain homogeneous films. The results showed that LDHs@PPy was prepared with an antibacterial rate of 99.7%(for Escherichia coli and Staphylococcus aureus). It had a good interface compatibility with the PCL matrix and played a role of heterogeneous nucleation in the PCL matrix. When the mass fraction of LDHs@PPy was only 1%, the tensile strength and elongation at break of nanocomposites increased by 35% and 23%, respectively. And the oxygen permeability also decreased by 56%. It was worth mentioning that the antibacterial rate of the nanocomposites was over 99.99%(for Escherichia coli and Staphylococcus aureus), which showed good antibacterial activity. The work promotes the application of layered clay/biopolymer nanocomposites in the field of active packaging.



Structure and Properties of Sidewall Compounds for Aircraft Tyre Modified by TBIR

ZHANG Yuefa, SHAO Huafeng, WANG Riguo, HE Aihua

2019, 40(8):  1733-1739.  doi:10.7503/cjcu20190113

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Trans-1,4-poly(butadiene-co-isoprene) copolymer rubber(TBIR) was used to modify nature rubber(NR)/butadiene rubber(BR) blends for sidewall compounds in aircraft tyre, and the crystalline behavior, mechanical properties and vulcanization characteristics of the NR/BR/TBIR compounds, physical and mechanical properties, dynamic mechanical properties and filler dispersion of the NR/BR/TBIR vulcanizates were studied in details. The results indicate that the incorporation of crystalline TBIR endows the NR/BR/TBIR compounds higher green strength and Young's modulus. Blending TBIR with NR/BR, the optimum curing time(t_c90) and the crosslinking density of the compounds increased. The NR/BR/TBIR[m(NR)/m(BR)/m(TBIR)=80/10/10, 80/0/20] vulcanizates with TBIR incorporation showed 7% higher of 300% modulus, 35%-50% higher of flexural fatigue resistance and reduced rolling resistance compared with NR/BR vulcanizate. NR/BR/TBIR(80/10/10) vulcanizate presented better comprehensive properties with improved thermo-oxidative ageing resistance. With the extension of curing time, modulus at 100% of NR/BR/TBIR(80/10/10) vulcanizate was above 18% higher than NR/BR(80/20) vulcanizate. Flexural fatigue resistance of NR/BR vulcanizate was reduced by 60%, while only 50% of NR/BR/TBIR(80/10/10) vulcanizate. The NR/BR/TBIR vulcanizate showed reduced rolling resistance(8%-14% lower) and unchanged wet skid resistance. The filler dispersion improved with reduced filler aggregate size. NR/BR/TBIR(80/10/10) vulcanizate had good resistance to the longer curing time.



New Thermal Features of Ethylene-based Polyolefins with Different Chain Architectures as Investigated by Step Scan Differential Scanning Calorimetry Method

SONG Li, LIN Jiaxiang, HUANG Dinghai

2019, 40(8):  1740-1747.  doi:10.7503/cjcu20190109

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Several selected commercial polyethylene-based polyolefins with different chain architectures were studied by step scan differential scanning calorimetry(DSC) method. It is found that the temperature dependence of heat capacity is the same for all the polyolefins with different chain architectures in equilibrium liquid state; the heat capacity in stable crystalline state at very low temperature is also very close regardless the variation of chain architectures. While in melting temperature range the heat capacity is very sensitive to the chain architectures, which is ascribed as the branching chains in the crystalline structures of polyethylene far below the main melting peak temperature range of polyolefins. In the step scan DSC of time-heat flow curves, low density polyethylene(LDPE) showed unique melting-recrystallizing behavior, possibly due to the relief of restrained segments between crosslinking points during melting process.



Morphology and Size Regulation of Polyaniline Induced by PS-b-P2VP as Template and Its Electrochemical Characters

WANG Lin, ZHANG Yanhui, Arzugul Muslim, LAN Haidie

2019, 40(8):  1748-1756.  doi:10.7503/cjcu20190105

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pH-responsive amphiphilic block copolymer polystyrene-b-poly(2-vinylpyridine)(PS₁₀₁-b-P2VP₇₀) was synthesized by reversible addition-fragmentation chain transfer radical polymerization(RAFT). The micellar solution of block copolymer was used as a template to prepare polyaniline(PANI) micro-nano particles. The controllable adjustment of particle morphology and size of PANI realized by pH regulation of the PS₁₀₁-b-P2VP₇₀ micellar solution, the relationship between particle size and the electrochemical performance of PANI were investigated. The molecular weight distribution and structure of PS₁₀₁-b-P2VP₇₀ were determined by size exclusive chromatography(SEC) and nuclear magnetic resonance spectroscopy(¹H NMR). Fourier infrared spectroscopy(FTIR), transmission electron microscopy(TEM), cyclic voltammetry(CV), chronopotentiometry, and electrochemical impedance spectroscopy(EIS) were used to test the structure, morphology and electrochemical properties of PANI. The results showed that the morphology andsize of PANI was well controlled, and its size decreases with increasing pH value at pH ≤ 4. At pH=5, the significant increase in the hydrophobicity of the P2VP segment in the templating agent resulted in the deposition of the micelle particles into larger-sized aggregates, and the average particle size of the PANI particles induced by the PS₁₀₁-b-P2VP₇₀ micelles was also significantly increased. When pH=4, the average particle size of PANI particles in solution tested by particle size measurement is 141 nm, which is "string-like" and has the best dispersion. PANI has fast charge and discharge capability and good pseudo-capacitance characteristics, and the electrochemical performance of each sample increases as the particle size decreases. At pH=4, the electrochemical activity of the sample is the best, the peak area of CV curve is the largest, and the discharge specific capacity is the highest. When the current density is 1 A/g, the specific discharge capacity can reach 1411.88 F/g and this sample has the smallest impedance value.



Surface Elemental Compositions and in Vitro Bioactivities of the PEEK Materials with Various Sulfonation and Alkali Treatments

CHENG Qinwen, YUAN Bo, ZHU Xiangdong, ZHANG Kai, ZHANG Xingdong

2019, 40(8):  1757-1765.  doi:10.7503/cjcu20190089

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A novel method combining sulfonation with alkali treatment for the surface chemical modification of polyetheretherketone(PEEK) was proposed and developed to endow PEEK with significantly enhanced bioactivity. The modified PEEK samples were subjected to the in vitro evaluation on the formation of bone-like apatite. The results showed that the sulfonation treatment improved the hydrophilicity of PEEK by introducing -SO₃H into the surface, and the sulfonation degree and surface morphology of the PEEK samples were influenced by the H₂SO₄ concentration and reactive time. PEEK-S(85%H₂SO₄, 30 min) presented better modification effect than other PEKK-S samples. The NaOH treatment for PEEK-S(85%H₂SO₄, 30 min) introduced Na into the surface and further increased its hydrophilicity, as was also affected by the reactive time. The in vitro bioactivity evaluation via simulated body fluid(SBF) immersion confirmed that the sulfonated PEEK samples treated with NaOH solution, i. e. PEEK-Na had rapid speed to form bone-like apatite on the surface. Only 3 d of soaking in SBF, PEEK-Na(24 h) was fully covered by a layer of bone-like apatite, showing good bioactivity. The current modification method is simple and thus promising for practical applications to improve the bioactivity of PEEK materials.



Preparation and Functions of Self-healing Light-shielding Paints for Cable Cover

LIN Musong, PENG Lei, ZHANG Sheng, LI Li, FU Qiang, HOU Junbo

2019, 40(8):  1766-1774.  doi:10.7503/cjcu20190066

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Self-healing light-shielding paints can not only reduce the photo-aging on the cable cover by ultro-violet, but also recover the micro-damage and hallrcuts on the surface of cable cover, improve the life of cable. In this paper, using nano particle of TiO₂ decorated by β-cyclodextrin(β-CD) as light-shielding agents, we developed a new light-shielding paint, the self-healing function of which was realized by inclusion interaction between β-CD and adamantane. This paint can stick on the PVC sample tightly and demonstrate a good hydrophobicity and low hydroscopicity. It has an excellent light-shielding ability on ultraviolet(>90%). Moreover, this paints had a good self-healing ability, the crack made by knife can recover at least three times and its tensile property can recover beyond 80%.



Preparation of Multi-scale Superhydrophobic Cotton/Polydopamine/Silica Composite for Selective Oil Absorption

LIU Yun, LI Ting, WANG Yang, DONG Weifu

2019, 40(8):  1775-1783.  doi:10.7503/cjcu20190021

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Owing to the chemical properties of polydopamine(PDA) and the hierarchical nanostructured of raspberry-like nanoparticles, the raspberry-like nanoparticles(PDA-SiO₂) were fixed onto the polydopamine coated cotton fibers to fabricate a super-hydrophobic cotton fibers with a micro-and nanostructure surface.Scanning electron microscope(SEM) results demonstrated that raspberry-like nanoparticles(PDA-SiO₂) were stably fixed on the cotton fibers surface. By introducing the incorporation fluorinated alkyl silane to the cotton fibers via a facile chemical reaction process, the cotton fibers surface possessed super-hydrophobicity with the water contact angle of 158.2° and super-oleophilicity with the oil contact angle of 0°. The as-prepared cotton fibers can be applied as effective materials for the separation of water and oil mixture with separation efficiency as high as 99.4%. In particular, the as-prepared cotton fibers showed excellent oil/water absorption selectivity with a high oil absorption capacity of 34 g/g. Moreover, the absorbed oils can be recovered by simple mechanical squeezing, and the porous cotton fibers maintained a high oil-absorption capacity upon multiple squeezing absorption cycles, displaying excellent recyclability. Therefore, this reported cotton fibers has the advantages of high separation efficiency, high absorption capacity, and outstanding durability, exhibiting the strong potential for industrial production.



Fabrication and Microwave Absorption Mechanism of PCIP/CoFe₂O₄/PANI Composites

LI Ze, WANG Jianjiang, GAO Haitao, ZHAO Fang

2019, 40(8):  1784-1792.  doi:10.7503/cjcu20190012

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Porous carbonyl iron powder(PCIP) was obtained by pitting etching technique. CoFe₂O₄ and polyaniline(PANI) were loaded on the surface of porous carbonyl iron by coprecipitation and in-situ polymerization to obtain PCIP/CoFe₂O₄/PANI composites with electromagnetic absorption properties. The morphology, composition and microwave absorption properties of the composites were studied by scanning electron microscopy(SEM), X-ray diffraction(XRD), Fourier transform infrared(FTIR), thermogravimetric analyzer(TGA) and vector network analyzer(VNA). The results showed that CoFe₂O₄/PANI agglomerated on the surface of PCIP, which significantly improved the electrical loss ability of the composites, and promoted the interference cancellation of 1/4 wavelength of low frequency electromagnetic wave. When the content of aniline was 0.5 mL, the reflection loss of the composites reaches -22.9 dB at 5.7 GHz, and the absorbing property was greatly improved in low frequency. The internal reasons for the improvement of low frequency absorbing properties of composites were analyzed by using the electromagnetic wave interface reflection model and the 1/4 wavelength interference cancellation theory.