Table of Content

10 March 2020, Volume 41 Issue 3

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Contents

Cover and Content of Chemical Journal of Chinese Universities Vol.41 No.3(2020)

2020, 41(3):  0-0. 

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Molecular-fence Catalysts for Low-temperature Oxidation of Methane to Methanol

SHEN Wenjie

2020, 41(3):  375-376.  doi:10.7503/cjcu20200056

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Selective oxidation of methane to methanol often suffers from the low reaction efficiency. Based on the concept of molecular fence effect, Xiao and co-workers reported a heterogeneous catalyst system for strengthening methane oxidation by the in-situ generated hydrogen peroxide at mild temperatures. They achieved a 17.3% conversion of methane and 92% selectivity toward methanol, giving a methanol productivity of 91.6 millimoles per gram of AuPd per hour. This work has been published online in Science in Jan.10, 2020.



Review

Recent Progress in Functional Nanomaterials Based on Self-assembly Technology ^†

WANG Jun, WANG Tie

2020, 41(3):  377-387.  doi:10.7503/cjcu20190643

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The rapid development of nanoscale self-assembly technology has broadened the application of nanomaterials. The self-assembly provides an effective and promising way to form new nanomaterials. This review introduces the value of nanoscale self-assembly technology and emerging synthesis methods in recent years. It focuses on the types of interactions driving nanoscopic self-assembly, including van der Waals forces, electrostatic forces, magnetic forces, hydrogen bonding, entropy effects, and other interactions(solvophobic interactions, DNA complementary base paring rules, etc.). In addition, the application fields as well as the existing opportunities and challenges of nanoscale self-assembly in developing novel materials are discussed.



Negative Thermal Expansion in Prussian Blue Analogues ^†

GAO Qilong, LIANG Erjun, XING Xianran, CHEN Jun

2020, 41(3):  388-400.  doi:10.7503/cjcu20190631

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Negative thermal expansion(NTE) is a promising topic for solid state chemistry, physics, and materials science. Due to the unique lattice structure characteristics, many Prussian blue analogues(PBAs) compounds have been found to exhibit NTE in the last two decades. This review is introduced for the NTE compounds progress in the PBAs. From the studies on local structure and lattice structure, the NTE mechanism is reviewed to reveal the important transverse vibrational contribution of N and C atoms. Based on this NTE mechanism, thermal expansion can be designed by inserting guest ions or molecules to reduce the contribution of transverse vibration. Finally, the perspective of PBAs is discussed for the design of new NTE PBAs compounds and the potential applications in future.



Research Processes in Fabricating Micro-patterned Quantum Dot Films by Solution Processes ^†

ZHANG Min, LIU Huan

2020, 41(3):  401-410.  doi:10.7503/cjcu20190671

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Quantum dot light emitting diode devices(QLEDs) have attracted widespread attention due to their good color rendering, high color purity, andstable performance. It can be used to manufacture display devices with ultra-thin structures or flexible structures. As the crucial light-emitting layer, high-quality quantum dot(QD) film is very important for realizing the high-performance of QLED device. This article reviews the research progress of solution-based QD films in recent years, where both the advantages and the perspectives are discussed. Furthermore, we also introduced the recently developed fiber-assisted controllable liquid transfer strategy and its application in preparing untrasmooth QD films. The review may offer guidance in preparing high quality QD film using solution processes.



Letter

Detection of Cocaine Based on the System of AIEgen, Aptamer and Exonuclease Ⅰ ^†

DU Xianchao, HAO Hongxia, QIN Anjun, TANG Benzhong

2020, 41(3):  411-416.  doi:10.7503/cjcu20190681

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A new system for detection of cocaine was designed based on an AIEgen of TPE-TTA, anticocaine aptamer and exonuclease Ⅰ(Exo Ⅰ) . The Exo Ⅰ can specifically cleave the phosphodiester bonds of nucleotides in nucleic acids either from the ends or interior of single stranded DNA(ssDNA). Meanwhile, the cocaine can combine with anticocaine aptamer and switch its configuration to Y-shaped double stranded DNAs(dsDNA) that prevent the aptamer degradation in the presence of Exo Ⅰ. When cationic 4,4',4″,4″'-{[ethene-1,1,2,2-tetrayltetrakis(benzene-4,1-diyl)]tetrakis(oxy)}-tetrakis(N,N,N-triethylbutan-1-aminium) bromide(TPE-TTA) was added to the Tris-HCl solution, it can combine with aptamer and the fluore-scence was turned on. The experiment conditions, including the amount of Exo Ⅰ, incubation time of the Exo Ⅰ with anticocaine aptamer, incubation temperature and time of anticocaine aptamer with cocaine were systematically investigated and the optimal conditions were obtained. With different concentrations of cocaine, the experimental results showed that the fluorescence intensity was progressively enhanced. The limit of detection(LOD) of 0.66 μmol/L was deduced. Moreover, the developed method also was used to determine cocaine in real urine samples, and the LOD can reach as low as 1.0 μmol/L. This work provides a new method for cocaine detection, which is promising for practical application.



Articles

Synthesis of Pillared-layer Metal-organic Frameworks from Anthracene Luminescent Linkers and Their Piezochromic Properties ^†

QI Yi, LI Qiaowei

2020, 41(3):  417-424.  doi:10.7503/cjcu20190653

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Employing anthracene luminescent linker 9,10-bis[(E)-2-(pyridin-4-yl)vinyl]anthracene(BP4VA) and two kind of carboxylic acid linkers with different lengths, two metal-organic framework(MOF) structures, FDM-26 with pillared-layer network and FDM-27 with dia topology, were synthesized. Moreover, the piezochromic property of BP4VA-based pillared-layer structure FDM-22 was investigated. Applying external pressure to the single crystals of FDM-22, which feature intrinsic coordination defects due to the metal-linker coordination bond breakage during activation, the framework integrity remains. However, their luminescence spectra show red shift up to 60 nm. It is concluded that the piezochromic response is due to the accumulation of more coordination defects after the pressure is applied.



Synthesis, Luminescence and Cell Imaging Properties of Amino Acid Capped YVO₄∶Eu Nanoparticles ^†

LIANG Longqi, CHEN Cailing, YU Ying, LI Yuxin, LI Chunguang, SHI Zhan

2020, 41(3):  425-430.  doi:10.7503/cjcu20190612

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Amino acid capped YVO₄∶Eu nanoparticles were synthesized via a facile and green microwave-assisted hydrothermal method with water as solvent and amino acid as template agent. The as-prepared nano-particles have good crystallinity, high water-dispersibility and small size(<50 nm). Meanwhile, the effects of adding amounts of amino acids on the structure and morphology of synthetic nanoparticles were also studied in detail. This synthetic method is equally suitable for the synthesis of other rare earth vanadates. The YVO4∶Eu nanoparticles exhibit excellent luminescent property under UV light excitation. It was compounded with a flexible polymer for simple 3D image display. YVO₄∶Eu nanoparticles can also be used as fluorescent probes to label mouse colon cancer cells(CT26 cells).



Triglycerides as Potential Biomarkers for Pesticides Pollution in Aquatic Environment Using UPLC-QTOF-MS ^†

HE Yu, XIA Qian, WANG Wenli, LUO Fang, CHEN Jinfeng, GUO Yating, WANG Jian, LIN Zhenyu, CHEN Guonan

2020, 41(3):  431-438.  doi:10.7503/cjcu20190615

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Pesticides exert a long-term negative influence on the aquatic organism and even the aquatic environment. It is necessary to find some potential biomarkers to give insight into the pesticides pollution and provide a rapid, sensitive, early-warning method. In this study, ultra-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry(UPLC-QTOF-MS) was applied to analyze the effect of pesticides on the metabolomics in liver and brain of Crucian carp. Three pesticides, namely trichlorfon, β-cypermethrin and imidacloprid were investigated, respectively. Data was collected by masslynx software in MS ^E mode, analyzed by UNIFI software for automatic detection and data filtering, compared to the online metabolome database. The metabolic difference of liver was more significant than that of the brain. The triglycerides(TGs) species were identified as the different metabolites. Among these three pesticides, imidacloprid had the most significant influence on the metabolism of TGs. The low concentration of acute exposure induced the accumulation of TGs in the liver, and the relationship between the content and the exposure concentration was in line with the growth trend of Michaelis-Menten equation. The results showed that TGs can sensitively reflect the low concentration exposure of imidacloprid pesticides(≤ 20 ng/mL) in a short period of time(≤ 2 h), which can be used as a potential biomarker to investigate the toxicity of imidacloprid to aquatic organisms, and help to establish a new method for estimation the pesticides contamination in aquatic environment.



A-site Cation Effects on Hot Carrier Relaxation in Perovskites by Nonadiabatic Molecular Dynamics Simulations ^†

HE Jinlu, LONG Run, FANG Weihai

2020, 41(3):  439-446.  doi:10.7503/cjcu20190701

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In recent years, perovskites have become a research hotspot in the field of solar cells due to their excellent optical and electrical properties. A large number of experiments reported that hot carries relaxation times follow the trend CsPbBr₃>MAPbBr₃(MA=CH₃NH₃)>FAPbBr₃[FA=HC(NH₂)₂]. However, the underlying mechanism of the A-site cation(Cs ⁺, MA ⁺, FA ⁺) effects on the relaxation time remains unclear, the hot electrons and holes relaxation of the three perovskiteswere investigated using time-domain density functional theory combined with nonadiabatic molecular dynamics. The obtained time scales agreed well with experiment. This is because A-site cation affects electronic-vibrational coupling with the inorganic Pb—Br framework via electrostatic interaction and hydrogen bond, leading to the strength of nonadiabatic coupling decreasing from FAPbBr₃ to MAPbBr₃, to CsPbBr₃. As a result, the hot carrier relaxation times decreases as the same trend. The study suggests that rational choice of A-site cations provides an excellent strategy to the optimize the performance of perovskite solar cells.



Synthesis and Electrochemical Performance of FeS₂ Microspheres as an Anode for Li-ion Batteries ^†

RONG Hua, WANG Chungang, ZHOU Ming

2020, 41(3):  447-455.  doi:10.7503/cjcu20190545

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FeS₂ nanosheets assembled FeS₂ microspheres were synthesized using ferric chloride(Ⅱ) and sodium thiosulfate as raw materials via one-pot hydrothermal method. We speculate the FeS₂ growth mechanism by regulating the molar ratio of iron source to sulfur source and hydrothermal time. Meanwhile, we combine with XRD and SEM characterization results and filter optimal conditions to improve the electrochemical performance. At the current density of 500 mA/g, first discharge/charge capacity can reach 905 mA·h·g ^-1 and 800 mA·h·g ^-1, respectively, and the coulombic efficiency is 88.4%. Even at high current density of 2000 mA/g, the FeS₂ exhibit excellent cycling behavior with a stable capacity of 350 mA·h·g ^-1 after 500 cycles.



Preparation of Novel Hydrophilic Conjugated Polymers and Their Applicationin Photocatalytic Hydrogen Evolution ^†

LUO Wei, LIANG Youcai, HU Zhicheng, TANG Haoran, LIU Xiaocheng, XING Yetong, HUANG Fei

2020, 41(3):  456-464.  doi:10.7503/cjcu20190647

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The application of organic conjugated polymers in photocatalytic hydrogen production has received increasing attention. However, most conjugated polymer photocatalysts showed unsatisfied photocatalytic hydrogen evolution, and the structure-performance relationship of conjugated polymers-based photocatalysts needs further exploration. In this study, we designed two conjugated polymers[poly({4, 8-bis[(2, 5, 8, 11, 14, 17, 20-heptaoxadocosan-22-yl)oxy]benzo[1, 2-b∶4, 5-b']dithiophene}-alt-[2, 5-di(thiazol-2-yl)pyrazine])(P7O-2N-2N) and poly({4, 8-bis[(2, 5, 8, 11, 14, 17, 20-heptaoxadocosan-22-yl)oxy]benzo[1, 2-b∶4, 5-b']dithiophene}-alt-[3, 6-di(thiophen-2-yl)-1, 2, 4, 5-tetrazine])(P7O-4N)] with hydrophilic side chains and nitrogen-contained heterocycles in backbones. The chemicals tructures and their influence on the absorption spectrum, energy level, free energy of hydrogen adsorption and photocatalytic performance of the material were systematically studied. The results showed that the conjugated polymer P7O-4N having a 3, 6-bis(thien-2-yl)-1, 2, 4, 5-tetrazine structure showed stronger inter-chain aggregation, lower hydrogen bonding free energy, and better photocatalytic hydrogen production performance than polymer P7O-2N-2N with 2, 5-bis(thiazole-2-yl)-pyrazide structure.



Articles:Inorganix Chemistry

Controllable Preparation of Polydopamine Modified Gold Nanoflowers and Its Application in Photothermal Therapy ^†

WU Fengren,LIU Yongjia,LU Xuemin,ZHU Bangshang

2020, 41(3):  465-472.  doi:10.7503/cjcu20190488

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Gold nanoflowers(AuNFs) were prepared through template-free method. The size and morphology of AuNFs were modulated by reaction temperature and the amount of reducing agent ascorbic acid. Furthermore, polydopamine(PDA) modification was adopt to improve the near-infrared(NIR) absorbance and biocompatibility of AuNFs. The size, morphology and optical properties of AuNFs and PDA modified AuNFs were characterized by transmission electron microscopy(TEM), dynamic light scattering(DLS) & Zeta potential analyzer and UV-Vis spectroscopy. The modification of PDA was characterized by Fourier transform infrared(FTIR) spectroscopy. The X-ray diffraction(XRD) analysis indicated that the crystal structure of AuNFs had no changes after PDA modification. The cytotoxicity of samples in vitro was evaluated by MTT assay. The results demonstrated that the lower temperature(0 ℃) is the proper reaction temperature to obtain the multi-branched structures of AuNFs. Meanwhile, increasing the concentration of reducing agent ascorbic acid would obtain the smaller AuNFs. The size of AuNFs ranged from 60—100 nm, and the wavelength of UV-Vis absorption peak was 575—650 nm. After PDA modification, the significantly red-shifted(over 80 nm) of UV-Vis absorption was found, and the absorption range in the near infrared region was significantly improved. The thickness of PDA layer outside AuNFs was about 8—14 nm through PDA concentration changes. Under 808 nm laser irradiation, the solution with PDA-AuNFs were rapidly heated to 57 ℃. In addition, the cell viability in vitro demonstrated that the PDA-AuNFs had lower cytotoxicity. After photothermal treatment with PDA-AuNFs, the cell survival of HeLa cells was about 10%. Therefore, the PDA-AuNFs had potential applications as photothermal reagents for tumor therapy.



Interaction Mechanism of Anions in Hydrothermal Crystallization of Desulfurization Gypsum Whiskers ^†

WANG Xiao,JIN Biao,WANG Yubin,XU Zhuoyue,ZHANG Lu,ZHANG Xiaoting,YANG Liushuan

2020, 41(3):  473-480.  doi:10.7503/cjcu20190486

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Desulfurization gypsum whiskers were prepared by hydrothermal method using purified flue gas desulfurization(FGD) gypsum as raw materials, CuCl₂, CuSO₄ or Cu(NO₃)₂ as additive. The crystal samples were characterized by FTIR, XPS, XRD, etc. to discuss the mechanism of Cu ²⁺ under different anions and these anions in crystal crystallization. The results show that the solubility characteristics of FGD gypsum and the crystal morphology of whiskers are affected by the anions under the effect of Cu ²⁺. The effect of anions is stronger than that of Cu ²⁺, and the adsorption state of Cu ²⁺ on whisker surfaces is affected by anions. The N {\mathrm{O}}_3^{-} promotes the dissolution of FGD gypsum, the Cl ^- takes the second place, and the S {\mathrm{O}}_4^{2-} hinders the dissolution of FGD gypsum. The whiskers with uniform diameter and large aspect ratio are prepared under the effect of Cl ^-, the whisker samples with high content of granular products can be prepared under the effect of S {\mathrm{O}}_4^{2-} , and the whisker samples are coarsened under the effect of N {\mathrm{O}}_3^{-} . The degree of chemical adsorption of Cu ²⁺ is different under the effect of different anions, which leads to the right drift and narrowing of the antisymmetric stretching vibration absorption peak of S {\mathrm{O}}_4^{2-} on the surface of the sample, and the differences of the decrease extent of electron binding energy of oxygen elements on whisker surface and the intensity of Cu—O binding energy. The intensity of Cu—O binding energy is the highest under the effect of N {\mathrm{O}}_3^{-} , the second under the effect of S {\mathrm{O}}_4^{2-} , and the weakest under the effect of Cl ^-.



Organic Chemistry

Synthesis and Antitumor Activities of α-2,7,11-Cembratriene-4,6-diol Derivatives ^†

BAI Bing,WANG Long,XU Gaigai,YANG Pengfei,ZHANG Gaihong,MAO Duobin

2020, 41(3):  481-489.  doi:10.7503/cjcu20190446

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Twenty eight α-2,7,11-cembratriene-4,6-diol derivatives were prepared by the modification at C6 position via introduction of acyl and ether groups. Their structures were confirmed by nuclear magnetic resonance spectroscopy(NMR) and high resolution mass spectrometry(HRMS). The synthesized compounds were screened for their in vitro biological activity. The results of 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfopheny)-2H-tetrazolium(MTS) assay indicated that some of them showed the same anticancer activity as cisplatin(DDP) did. Among them, α-2,7,11-cembratriene-4-ol-6-phenylacetate(1i) showed cytotoxicity against MCF-7 with an IC₅₀ value of 15.45 μmol/L, and α-2,7,11-cembratriene-4-ol-6-(2-F)phenylacetate(1t) showed cytotoxicity against SMMC-7721 with an IC₅₀ value of 11.44 μmol/L, respectively. Structure-activity relationship revealed that the phenylacetate substituents at C6 position played an important role in inhibition activity.



Synthesis, Structure and Recognition Properties of Macrocyclic Crown Ethers with Oxadiazole ^†

TIAN Xia,YANG Fuqun,YUAN Wei,ZHAO Lei,YAO Lei,ZHEN Xiaoli,HAN Jianrong,LIU Shouxin

2020, 41(3):  490-497.  doi:10.7503/cjcu20190317

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A series of macrocyclic crown ethers containing oxadiazole groups were synthesized and their single crystals were obtained. Their structures were characterized by nuclear magnetic resonance(NMR), high resolution electrospray ionization mass spectroscopy(HRESI-MS) and X-ray single crystal diffraction. The single crystal X-ray diffraction revealed that 2,3,11,12-dibenzo-4,7,10,16-tetraoxa-14,15-diazabicyclo[11.2.1]-hexadecane-13,15-diene(2) belonged to orthorhombic crystal system with space group Pna2₁, 2,3,14,15-dibenzo-4,7,10,13,19- pentaoxa-17,18-diazabicyclo[14.2.1]-nonadecane-16,18-diene(3) belongs to monoclinic crystal system with space group C2/c and 2,3,17,18-dibenzo-4,7,10,13,16,22-hexaoxa-20,21-diazabicyclo[17.2.1]-docosadecane-19,21-diene(4) belonged to orthorhombic crystal system with space group Pbca. Three crown ethers were all connected to form a three-dimensional supramolecular structure by C—H…O or C—H…N hydrogen bond intramolecular and π-π stacking. The bonding behaviors of 2,5-bis[2-(2-methoxyethoxy)phenyl]-1,3,4-oxadiazole(1) and crown ethers 2—4 with different sizes to metal ions Li ⁺, Na ⁺, K ⁺, Rb ⁺, Mg ²⁺ and Ca ²⁺ was determined by fluorescence spectroscopy. The results showed that open-chain crown ether 1 and macrocyclic crown ether 4 exhibited fluorescence quenching behavior and good bon-ding ability and selectivity on alkaline earth metal Ca ²⁺. While crown ether 2 showed good bonding ability to Na ⁺ and K ⁺and poor Na ⁺/K ⁺ selectivity.



Physical Chemistry

W Element Doped CeO₂ as Heterogeneous Electro-Fenton Catalyst for Efficient Treatment of Oily Wastewater ^†

LIU Yigang,ZHAO Peng,HAN Yugui,SONG Xin,HAN Zhipeng,XIE Liangbo,LI Zhuang,JIA Xiaoqing,LI Yi

2020, 41(3):  498-504.  doi:10.7503/cjcu20190598

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W element-doped CeO₂ was designed as heterogeneous Electro-Fenton(EF) catalyst to purify oily wastewater, and the effect of efficient purification of oily wastewater was realized. In addition, W-CeO₂-0.4 composite was characterized by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that W element doped CeO₂ with irregular flake morphology has better redox ability and Fenton-like catalytic effect compared with pure CeO₂. As heterogeneous EF catalyst, the treatment effect of oily wastewater is better than that of electro-adsorption and physical adsorption obviously. In the further parameter optimization experiment, it was found that the purification capacity of oily wastewater reached 99.8%, TOC removal rate reached about 90%, COD removal rate reached 76% in 90 min when the voltage was 4 V, pH=3 and W-CeO₂-0.4 was used as catalyst.



Co-sensitization in the Visible Light/H₂O₂ System ^†

YANG Jin,CAO Yan,ZHANG Naidong

2020, 41(3):  505-511.  doi:10.7503/cjcu20190588

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The causes of co-sensitization in the visible light/H₂O₂ system was analyzed. Through the analysis of the UV-Vis spectra of the phenol red, methyl orange, azure I and the mixed solution which consisted of all the three solutions mentioned above, it was seen that the mixed solution broadened the response range in the visible light region so that the utilization rate of visible light was increased. The yields of photoinduced electron(hydrated electron), singlet oxygen and superoxide anion radical generated under visible light in these matters mentioned above were tested by 1, 10-phenanthroline method, 1, 5-diphenylcarbazide method and ammonium molybdophosphate spectrophotometry. The result showed that the yields of superoxide anion radical in the mixed solution was significantly higher than that of the single chromophoric dissolved organic matters, more-over, the yields of photoinduced electron and singlet oxygen were not much different in each solution. Hence the increase of superoxide anion radical production is the main reason for the co-sensitization. In addition, experimental results confirmed that photoinduced electron could not catalyze hydrogen peroxide to generate hydroxyl radical.



Combustion Reaction Mechanism Construction by Two-parameter Rate Constant Method ^†

LI Xiangyuan,YAO Xiaoxia,SHENTU Jiangtao,SUN Xiaohui,LI Juanqin,LIU Mingxia,XU Shimin

2020, 41(3):  512-520.  doi:10.7503/cjcu20190567

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The Arrhenius equation with two parameters, activation energy(E) and pre-exponential factor(A), was proposed to describe the temperature dependence of reaction rate constant in developing combustion mechanisms. As a test, the UCSD core mechanism has been re-parameterized using the two-parameter Arrhenius equation and applied to the kinetic simulation of some small molecule systems, without changing the numbers of species and elemental reactions. The results showed that although the overall mechanism optimization is not performed, the results are basically comparable with the three-parameter mechanism. The advantage of the two-parameterization is the physics of the activation energy in Arrhenius equation, and in this way one can carry out the comparison and migration of the rate constants between different mechanisms. Furthermore, the number of the variable in the global optimization of mechanism aimed at such as ignition delay time of a fuel, can be reduced considerably.



One-step Synergistic Hydrophobic Modification of Melamine Sponge and Its Application ^†

LIU Shuaizhuo,ZHANG Qian,LIU Ning,XIAO Wenyan,FAN Leiyi,ZHOU Ying

2020, 41(3):  521-529.  doi:10.7503/cjcu20190557

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The amphiphilic melamine sponge(MS) was synergistically modified in one step by nitric acid(HNO₃). Thus, the HNO₃ modified melamine sponge(HMMS) with superhydrophobicity was prepared. The structure, morphology and composition of the prepared HMMS were analyzed by Fourier transform infra-red spectroscopy(FTIR), thermogravimetry(TG) and scanning electron microscopy(SEM). And its surface wettability, mechanical properties, adsorption properties, recycling performance and oil-water separation perfor-mance were studied. The results show that the HMMS has superhydrophobicity, excellent mechanical properties, recycling ability and selective adsorption capacity, and exhibits high separation efficiency up to 6×10 ⁶ L?m ^-3?h ^-1. Particularly, HMMS can remain stable in physicochemical properties in demanding environments. Therefore, the novel oil-water separation material have high practical application value.



Preparation of SnO₂/GDE Cathodes and Their Electrocatalytic Reduction of CO₂ to Produce Formic Acid ^†

ZHUO Mengning,LI Fei,JIANG Hao,CHEN Qianwen,LI Peng,WANG Lizhang

2020, 41(3):  530-537.  doi:10.7503/cjcu20190516

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The SnO₂ gas diffusion electrodes(SnO₂/GDE) were prepared by low temperature hydrothermal synthesis. Their physicochemical properties and catalytic performance for reduction of CO₂ to produce formic acid were studied. The results of scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy showed that the catalysts prepared at 60, 75 and 100 ℃ were all nano-SnO₂ powder with good dispersibility, and the particle sizes were 7.9, 11.8 and 12.9 nm, respectively. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy results showed that the electrodes had excellent electrocatalytic activity, and their electrochemically active surface area was 150, 470, 240 cm ², respectively, the resistance after fitting was 8.5, 3.9, and 6.6 Ω·cm ², respectively. With electrical charge of 500 C passed at applied potential of -1.8 V(vs. SCE),, the electrodes showed higher electrocatalytic performance for reduction of CO₂ to produce formic acid. For the best electrode that prepared at 75 ℃, the current density of formic acid production was 22.8 mA/cm ², and the Faraday efficiency of formic acid production was as high as 93.5%; after 20 h of electrolysis of this electrode, the current density of formic acid production could be maintained at 12.8 mA/cm ², and the Faraday efficiency of formic acid production was stable at about 65%, indicating that the preparation of SnO₂ catalysts by low-temperature hydrothermal synthesis has great competitiveness.



Excellent Ultraviolet Photocatalytic Efficiency of Mg ²⁺ Doped ZnO and Analysis on Its Synergetic Effect ^†

ZHAO Peng,ZHANG Jinteng,LIN Yanhong

2020, 41(3):  538-547.  doi:10.7503/cjcu20190467

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A series of Mg-doped ZnO samples were synthesized via a facile chemical precipitation method. Mg ²⁺ was effectively doped into the lattice of ZnO and MgO particles formed on the surface of ZnO when the Mg doping content exceeded 5%. Under the combined action of Mg ²⁺ and MgO insulators, the degradation rate of RhB over 10%Mg-ZnO photocatalyst was 81.3% in 5 min under ultraviolet light and the degradation rate constant was 0.3271 min ^-1, which was 3.42 times that of pure ZnO(0.0957 min ^-1). The transient photovoltage(TPV) and the contact potential difference(ΔCPD) measurements directly demonstrated that the incorporation of Mg ²⁺ decreased the work function of ZnO and increased the number of electrons in the conduction band, thus the separation efficiency of photogenerated electrons and holes can be improved. The surface photocurrent(SPC) and the Cr(Ⅵ) reduction experiments showed that the formation of MgO insulating particles inhibited the “reverse” transmission of photogenerated electrons in ZnO, which prolonged the recombination time of electrons and holes, thus indirectly improved the utilization of photogenerated holes. This work provides a new idea for the design of highly efficient photocatalytic materials.



Polymer Chemistry

Analysis of Composition and Antigenic Atomic Oxygen Performance of Silica-reinforced Silicone Rubber ^†

WANG Kai,FAN Xiang,CHEN Mengjiong

2020, 41(3):  548-555.  doi:10.7503/cjcu20190517

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In order to clarify the chemical composition and the effect of filler addition on the physical properties of the space silicone rubber, the filler compound method was used to prepare the silicone rubber polymer material. The chemical composition test, atomic oxygen exposure test, and mechanical property test were used to study its structural composition and physical properties. The particle size of the silica filler was mainly distributed between 8 and 16 μm by the micro-particle size test. After Fourier transform infrared spectrophotometry(FTIR), nuclear magnetic resonance( ¹H NMR and ²⁹Si NMR) and gel permeation chromatography(GPC) tests, it was found that the silicone rubber contained various groups, such as Si—Me, Si—Ph and Si—O—Si and its molecular weight dispersion coefficient was 1.56. It was further deduced that the reaction type of the base rubber and the cross-linking agent was dehydroxyamine type. Atomic oxygen exposure tests and mechanical tests confirmed that silane-modified silicone rubber polymer material exhibited better antigenic oxygen performance, 54% higher storage modulus after dynamic mechanical tests, and better mechanical response performance. The results show that the surface modification treatment can enhance the interaction between the filler and the silicone rubber, and improve the antigenic oxygen performance and comprehensive mechanical properties of the filler composite silicone rubber polymer material.



Preparation of Armor Structure Polystyrene@Magnesium Hydroxide Composite Microspheres by Pickering Suspension Polymerization with Nano-magnesium Hydroxide as Pickering Stabilizer ^†

ZHU Pei,WANG Feng,CHEN Zheming,LI Gen,GAO Chong,LIU Peng,DING Yanfen,ZHANG Shimin,CHEN Juan,YANG Mingshu

2020, 41(3):  556-564.  doi:10.7503/cjcu20190462

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The unique properties of organic-inorganic composite microspheres with armor structure have aroused great interest. Armor structure organic-inorganic composite microspheres were prepared by Pickering suspension polymerization using styrene as monomer, azobisisobutyronitrile(AIBN) as initiator, magnesium hydroxide nanosheets as Pickering stabilizer. The composite microspheres were characterized by scanning election microscopy(SEM), transmission electron microscopy(TEM), energy dispersive spectroscopy(EDS), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), thermal gravimetric analysis(TGA) and micro-scale combustion calorimetry(MCC). The morphology and structure of the composite microspheres were confirmed. Magnesium hydroxide was tightly coated on the surface of the polystyrene microspheres to form the armor structure composite microspheres with magnesium hydroxide as the outer layer and polystyrene as the inner sphere. When magnesium hydroxide content was 2%, the average particle size of the microspheres was 25 μm, much lower than that of pure PS microspheres, 760 μm. It was also proved that the composite microspheres with armor structure could reduce the heat release rate and inhibit the cracking of polymers. And the acid etching of microspheres could remove completely the outer layer of magnesium hydroxide. This Pickering suspension polymerization is simple to operate, low cost, and the prepared armor composite microspheres have small particle size, narrow distribution and high sphericity. Moreover, the armor structure endows the material with a certain degree of flame retardant performance.



Structure and Properties of NBR/TBIR Composites with High Abrasion Resistance and Low Heat Built-up ^†

WU Yingfei,LI Hongyu,CAI Lei,HE Aihua

2020, 41(3):  565-571.  doi:10.7503/cjcu20190459

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The novel trans-1,4-poly(butadiene-co-isoprene) copolymer rubber(TBIR) was used to modify the acrylonitrile-butadiene rubber(NBR) for conveyor wheel with high abrasion resistant and low heat built-up. The crosslink density, physical and mechanical properties and filler dispersion of the NBR/TBIR vulcanizes filled with silica were discussed. The results show that the vulcanization rate and crosslink density of NBR/TBIR compounds increase with the increase in TBIR component when compared to the NBR compound. The NBR/TBIR(90/10, mass ratio) vulcanize shows 15% higher wear resistance, 5% lower heat built-up, 22% reduced dynamic compression set and better filler dispersion, while the other properties like aging resistance and solvent resistance kept almost unchanged. The NBR/TBIR(80/20, mass ratio) vulcanizate shows lower heat built-up, lower compression set and high filler dispersions when compared with NBR/BR(80/20) vulcanizate.



Research on Self-healing Polypolyurethane Elastomer Based on Multiple Reversible Action ^†

SHENG Yeming,CHENG Bo,LU Xun

2020, 41(3):  572-581.  doi:10.7503/cjcu20190454

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Self-healing materials received widely concerns because of its ability for prolonging the service life of materials and fulfilling the need for sustainable development in recent years. To solve the problem that self-healing materials can’t do both well in self-healing property and mechanical property, we prepared a self-healing polyurethane elastomer with high strength, high toughness and high repair efficiency in this paper, on the basis of the designability of polyurethanes, we introduced disulfide bond to the polyurethane main chainis and used boric acid ester bond constructed using boric acid as a reversible cross-linking point to form the cross-linked network structure. The materials was characterized by infrared spectroscopy, dynamic mechanical analysis, mechanical test, electron microscope and self-healing test. The results show that the self-healing polyurethane has the characteristics of hard and tough, which the strength of the original sample has 23.3 MPa, the elongation at break can reach 11.77%, and can self-heal at a mild conditions. After repairing at 60 ℃ for 24 h, the original strength of the sample can be restored to 99%, and the self-healing process can be repeated many times. In addition, the material has the characteristics of multi-channel self-healing, which can be repaired by means of thermal self-healing or water-assisted thermal self-healing, and the latter is faster.



Preparation and Properties of High Thermal Conductivity Hexagonal Boron Nitride/Aramid Fibrid Composite Film ^†

XIE Fan,WANG Yafang,ZHUO Longhai,QIN Panliang,NING Doudou,WANG Danni,LU Zhaoqing

2020, 41(3):  582-590.  doi:10.7503/cjcu20190408

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To expand the application of aramid fibrid(AF) in the field of insulated and thermal conductive electronic devices, dopamine(DA) was used to modify the hexagonal boron nitride(h-BN) initially, which could oxidize self-polymerization under weak alkaline conditions and form the strong adhesive polydopamine(PDA). Then, the modified h-BN(h-BN@PDA) was used as the heat conductive filler to fill the AF matrix. Subsequently, h-BN@PDA/AF composite films were prepared by vacuum assisted filtration, and the microstructure, surface functional group, thermal conductivity, insulation properties and mechanical properties were also analyzed. The results showed that PDA was coated on the surface of h-BN, and plenty of active groups were introduced on the surface to form hydrogen bond with AF fiber. It was beneficial to increase the interfacial bonding and improve conductivity and insulation properties of composite films. When the h-BN@PDA mass fraction was 70%, thermal conductivity of h-BN@PDA/AF composite films could reach 1.36 W/(m·K), which increased by 697.65% compared to pure AF films. Additionally, the volume resistivity and tensile modulus of h-BN@PDA/AF composite films were 5.96×10 ¹⁴ Ω·m and 287.19 MPa, respectively.