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10 November 2022, Volume 43 Issue 11

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Content

Cover and Content of Chemical Journal of Chinese Universities Vol.43 No.11(2022)

2022, 43(11):  1-8. 

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Review

Assembly of Perovskite Arrays and Multifunctional Detector Applications

YUAN Meng, ZHAO Yingjie, WU Yuchen, JIANG Lei

2022, 43(11):  20220448.  doi:10.7503/cjcu20220448

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Perovskite materials have a wide application prospect in the field of photoelectric detection due to their excellent photoelectric performance. The integrated development of perovskite photodetectors requires integration processing technology， which will exploit the application of perovskite in multifunctional detector applications. In recent years， many researchers have devoted themselves to this aspect of research and achieved a series of important achievements. This review summarizes perovskite materials arrays and preparation of multifunctional detectors， and introduces the structure of the perovskite materials classification， integration method， the photodetector array basic device type， and performance indicators. Finally， we discuss the perovskite one-dimensional array of the high- performance photodetector and its related application research progress of multifunctional detector. Meanwhile， we present insight toward the promising future directions in this research filed.



Doping Regulation in Transition Metal Phosphides for Hydrogen Evolution Catalysts

WANG Zumin, MENG Cheng, YU Ranbo

2022, 43(11):  20220544.  doi:10.7503/cjcu20220544

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Due to their excellent catalytic properties， transition metal phosphides have become the most promising and inexpensive electrocatalytic materials to replace noble metals in electrocatalytic water splitting for hydrogen production. Element doping is an efficient way to greatly improve their activity and stability. This review revisits recent research on regulating the properties of transition metal phosphides through doping modifications. The types of elements（metal doping， non-metal doping， co-doping）， the number of elements（single element doping， multi-element doping， high entropy doping）， and the doping position are discussed in detail. And how these factors tune the electronic structure of transition metal phosphides are studied. Through the combination of experimental results and theoretical calculation， the effects of doped elements on hydrogen adsorption intensity， water adsorption and dissociation， charge transfer and transmission were analyzed. Moreover， the structure-activity relationship between doped structure， electronic structure， and hydrogen evolution reaction（HER） catalytic performance was obtained. Finally， we put forward the remaining challenges and future research directions of related research.



Article: Inorganic Chemistry

Synthesis and Optical Properties of RbPb₂Cl₅

ZHANG Zhinan, CHENG Haiming, TENG Shiyong, ZHANG Ying

2022, 43(11):  20220418.  doi:10.7503/cjcu20220418

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Lead-based perovskites have been extensively studied due to their excellent optoelectronic properties. Compared to the typical CsPbX₃ material， the study of RbPb₂X₅ perovskites material is relatively backward. In this paper， the effect of different ball milling times on the formation of RbPb₂Cl₅ crystals was investigated by controlling the molar ratio of reaction precursors using a mechanical grinding method. The X-ray diffraction result showed that the pure phase RbPb₂Cl₅ crystal powder could be prepared after 1 h of grinding， and its structure was attributed to the monoclinic crystal system with ［Pb-Cl₇］ decahedra connected by edge-sharing phases， and the P2₁/C space point group. The RbPb₂Cl₅ crystals show significant absorption in the UV region with a band edge absorption value of 3.82 eV. Under photoexcitation conditions， the crystals display excitation wavelength dependent dual wavelength fluorescence of yellow-green light at 540 nm and orange light at 635 nm. The study of the variable temperature spectra， time-resolved spectra and the linear dependence of the intensity of the emission peaks on the energy density suggests that the luminescence mechanism should be attributed to the fact that the material has two different self-trapped excitonic states， resulting in a dual-channel emission dependent on the excitation wavelength.



Properties of Transition Metal-biimidazole-Dawson-type Tungstophosphate Hybrid Compounds as Supports for Enzyme Immobilization

ZHU Haotian, JIN Meixiu, TANG Wensi, SU Fang, LI Yangguang

2022, 43(11):  20220328.  doi:10.7503/cjcu20220328

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Five Dawson-type polyoxometalate（POM）-based organic-inorganic hybrids， namely， ［Ni（H₂biim）₃］₄·［Ni（H₂biim）₂（P₂W₁₈O₆₂）₂］·2H₂O（1）， ［Co^III（H₂biim）₃］₂［P₂W₁₈O₆₂］·8H₂O（2）， ［Cu（H₂biim）₂］₃［P₂W₁₈O₆₂］·4H₂O（3）， ［Co^Ⅱ（H₂biim）₃］₂H₂［P₂W₁₈O₆₂］·9H₂O（4） and ［Ni（H₂biim）₃］₃［P₂W₁₈O₆₂］·2H₂O（5）， were constructed from transition metal-biimidazole（TM-H₂biim） coordination cations and tungstophosphate polyoxoainons through hydrothermal and direct precipitation methods， and characterized by single crystal X-ray diffraction analysis， infrared（IR） spectroscopy and thermogravimetry-differential thermal analysis（TG-DTA）. Compounds 1—5 were used as the supports for immobilizing horseradish peroxidase（HRP）， exhibiting high load capacities. In addition， the reusabi?lity， storage stability and the performance for detecting hydrogen peroxide（H₂O₂） of the obtained immobilized enzymes HRP/1—HRP/5 were also evaluated by circular dichroism（CD） spectroscopy and laser scanning confocal microscopy（LSCM）. The experimental results show that the immobilization of HRP on POMs can be realized by the simple physical adsorption method. There is a strong interaction between POM and HRP， and the HRP immobilization by POM not only improves the tolerance of HRP to the operation and storage environment， but also expands the application of POMs in the field of enzyme immobilization.



Analytical Chemistry

Fabrication of Bionic Leaf Model and Its Application in Agarose Microfluidic Chip

WANG Fangyuan, ZHANG Fenxian, LI Yi, GAO Jianhua, NIU Yanbing, SHEN Shaofei

2022, 43(11):  20220445.  doi:10.7503/cjcu20220445

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The vein sequence of leaf is similar with human vascular network in terms of structure and function， highlighting a manner to create human vessel-like structure in vitro. However， several technical（irreproducible vein pattern of different leaves） and logistic（limited availability across seasons） issues prevent the use of fresh leaves as template. Herein， a practical and effective method for biomimetically replicating the leaf structure was developed and this bionic leaf model was applied to constructing a low-cost and simple-to-operate agarose microfluidic chip. Moreover， the number and size of the pulse sequences（channels） of the primary veins， secondary veins and tertiary veins in the agarose chip were measured， where maximum and minimum widths of pulse sequence are 1038.02 μm and 36.32 μm， respectively. Lastly， the fabricated channels of different widths provided stable and reliable gradients for studying bacterial chemotaxis. Taken together， our methodology is of great significance for drug screening and microbial research.



Chiral Metal-organic Cage MOC-PA as a Chiral Stationary Phase for Capillary Electrophoresis

QIN Gaizhao, TANG Minghua, LAI Yalin, YUAN Liming

2022, 43(11):  20220417.  doi:10.7503/cjcu20220417

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A chiral metal-organic cage， ［Cu₁₂（L_PA）₁₂（H₂O）₁₂］（PA=L-phenylalanine， MOC-PA）， was used as a novel stationary phase for capillary electrophoresis separation. The material was characterized by X-ray powder diffractometer， infrared spectroscopy， thermogravimetric analysis and scanning electron microscope. The results showed that the chiral metal-organic cage has good thermal stability and spatial structure. The capillary chromatographic column prepared from this material has a good chiral recognition ability， which can resolve 1，2-diphenylethylene glycol， zopiclone， 4-methyldiphenyl methanol and anisin， as well as nitrophenol. By exploring the optimal conditions for 1，2-diphenylethylene glycol， zopiclone， 4-methyldiphenylcarbinol and anisoin， the effects of voltage， buffer solution concentration and pH on the resolution of chiral samples in capillary electrophoresis were obtained. And the reprodu?cibility study of the capillary column with zopiclone shows that the capillary electrophoresis column prepared from this material has specific stability and reproducibility. Therefore， the metal organic cage is a good chiral stationary phase in capillary electrophoresis， and has certain chiral separation ability and outstanding development prospect in chromatographic separation.



Dual Signal Detection of HPV16 DNA by CRISPR/Cas12a Biosensing System Based on Upconversion Luminescent Resonance Energy Transfer

ZHANG Liling, LIU Liu, ZHENG Mingqiu, FANG Wenkai, LIU Da, TANG Hongwu

2022, 43(11):  20220412.  doi:10.7503/cjcu20220412

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Traditional upconversion nanomaterials with pure core structure have some disadvantages such as low sensitivity due to surface quenching effect or low efficiency of luminescence resonance energy transfer（LRET）， the sensitivity of target detection has some limitations. Herein， NaYF₄∶Yb³⁺，Er³⁺（C-UCNPs） core luminescence and NaYF₄@NaYF₄∶Yb³⁺，Er³⁺@NaYF₄（CSS-UCNPs） inner shell layer luminescence energy-limited upconversion nanomaterials were synthesized by a multi-step high-temperature co-precipitation， mediated by a shell layer epitaxial growth method. Meanwhile， the crystalline shape， morphology， surface ligands， elemental composition， and luminescence resonance energy transfer efficiency of the as-prepared materials were characterized and the results demonstrate that the materials processes the advantages of low surface quenching effect and high luminescence resonance transfer efficiency. Subsequently， the nanomaterials were combined with clustered regularly interspaced short palindromic repeats（CRISPR）-CRISPR-associated protein(CRISPR/Cas) 12a-gold nanoparticle system to achieve colorimetric qualitative and upconversion luminescence quantitative analysis of human papillomavirus DNA （HPV16 DNA） with a detection limit of 69.8 pmol/L， and the dual-signal assay effectively improved the accuracy of the detection results. In addition， the method is not only specific， but also recognizes single-base mismatched HPV16 DNA， which greatly improves the fault tolerance of DNA fragments



Organic Chemistry

Catalytic Activity and Reaction Mechanism of FLPs for the Reduction of Enamine

WEN Zhiguo, QIAO Zaiyin, TIAN Chong, MAXIM Borzov, NIE Wanli

2022, 43(11):  20220555.  doi:10.7503/cjcu20220555

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Over the decade after the pioneering work of frustrated Lewis pair（FLP） chemistry， this research area has achieved tremendous success as novel transition-metal-free system in organic synthesis， enzymatic models， and material sciences. The popularly accepted mechanism of FLP reactivity involves the polarization and heterolytic cleavages of a substrate molecular. Whiles there are also few work showing differing reaction mechanisms for special kinds of Frustrated radical pairs（FRPs）， which suggests a homolytic cleavage via one-electron processes. This work studied the Si—H bond activation by B（C₆F₅）₃ and enamines. In the presence of B（C₆F₅）₃ enamines did not undergo the expected hydrosilyation with silanes. The dominated hydrogenation products could not match the classic heterolytic cleavages mechanism by B（C₆F₅）₃ activating R₃Si—H and transferring of R₃Si⁺ to a nucleophile. The isotopic experiment results supported a mechanism that proceeds via the highly reactive radical anion［B（C₆F₅）₃］^- as the reported FRP behaviors. Understanding the reaction mechanisms is not only crucial to progress in fundamental chemical research but also for further broadens the potential reactivity of FLP systems.



Methyl-modified Carbazole/Diphenyl Sulfone-based AIE-TADF Blue Emitter and Its OLEDs

WU Zexin, ZHU Yuanjie, WANG Hongzhong, WANG Junan, HE Ying

2022, 43(11):  20220371.  doi:10.7503/cjcu20220371

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A pure organic carbazole/diphenyl sulfone derivative with D-A-D structure， 9，9'-［sulfonylbis（3，1-phenylene）］bis（1，3，6，8-tetramethyl-9H-carbazole）（TMe-mSOCz）， was constructed using tetramethyl carbazole as electron donor（D） and diphenyl sulfone as electron acceptor（A）. The photophysical properties of the synthesized materials showed that TMe-mSOCz exhibited obvious aggregation-induced emission（AIE） and thermally activated delayed fluorescence（TADF）， with delayed lifetime and delayed fluorescence accounting for 2.26 μs and 47.7%， respectively， and good thermal and electrochemical stabilities. The organic light emitting diodes（OLEDs） fabricated based on TMe-mSOCz as the non-doped light-emitting layer exhibits a turn-on voltage（V_on） of 3.5 V， the maximum external quantum efficiency of 5.63%， and the International Commission on Illumination（CIE） coordinates of （0.18， 0.26）. At 1000 cd/m² brightness， the non-doped OLED device possesses a very low（7.1%） efficiency roll-off， good color stability， and a narrow full width at half maxima（FWHM） of 72 nm. The research results showed that the introduction of methyl modification between the receptors of traditional TADF molecules was beneficial to the development of D-A-D type TADF molecules with AIE characteristics and higher efficiency， which supplied a new route to OLED emitter fabrication based on AIE-TADF molecules.



Physical Chemistry

Fabrication of Boehmite Fiber-reinforced Silica Aerogels and Their Performances

ZHANG Jie, YIN Bo, LIU Weixin, LIU Xingping, LIAN Wenxian, TANG Shaokun

2022, 43(11):  20220483.  doi:10.7503/cjcu20220483

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Boehmite fibers were prepared using aluminum chloride hexahydrate as aluminum source by a hydrothermal method. Silica composite aerogels doped with boehmite fibers were then fabricated using methyltrimethoxysilane and tetraethoxysilane as silicon co-precursors after the sol-gel process and ambient pressure drying. The effect of the boehmite fiber content on the composite aerogel was studied. When the content（mass fraction） of boehmite fibers to silicon sol is 1%， the aerogel obtains the optimal mechanical properties， which can withstand 17.1% compressive strain， the maximum compressive strength is 1.12 MPa and the compressive modulus is as high as 2.57 MPa. The composite aerogels show low thermal conductivity of 0.0670 W·m^?1·K^?1 at 150 ℃. Moreover， it is found that the boehmite fiber can inhibit the sintering and phase transformation of silica particles at elevated temperature and thus enhance the high temperature resistance of silica aerogels. Accordingly， the silica-boehmite fiber composite aerogel can still maintain good thermal insulation performance and high mechanical strength at a high temperature of 1100 ℃.



Zinc-based Activated Fe/Co/N Doped Biomass Carbon Electrocatalysts with High Oxygen Reduction Activity

HE Yujing, LI Jiale, WANG Dongyang, WANG Fuling, XIAO Zuoxu, CHEN Yanli

2022, 43(11):  20220475.  doi:10.7503/cjcu20220475

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To promote the wide application of clean energy fuel cells， there is an urgent need to develop transition metal-based high-efficiency oxygen reduction（ORR） catalytic materials with low cost and a wide source of raw materials to replace the precious metal platinum-based catalytic materials currently in use. In this paper， non-noble metal ions such as iron and cobalt metal ions were used as the main active sites of catalytic materials， and the carbon source of sodium alginate， a marine biomass material with a three-dimensional pore structure， rich in carboxyl， hydroxyl groups， and easy to form in aqueous gel networks， was preanchored in situ by metal-carboxyl/ hydroxyl chelating key， freeze-drying get aerogel. Then， through high-temperature carbonization， a highly active and stable Co/Zn/Fe/N@bio-C-2 oxygen reduction catalyst material with active sites evenly distributed in the carbon skeleton with multistage pore structure was obtained. The catalyst consists of two different iron-based active materials（Fe₂O₃ and Fe） and two different cobalt-based active materials（CoO and Co）. At the same time， zinc nitrate was used as an activator to improve the pore structure of the catalytic materials. The total area of the carbon materials increased from 149.3 m²/g to 325.3 m²/g. A series of comparative tests revealed that the synergistic effect of the Fe/Co dual active site and a suitable specific surface area resulted in the best ORR catalytic activity of Co/Zn/Fe/N@bio-C-2. The initial potential and half-wave potential reached 0.99 and 0.87 V in 0.1 mol/L KOH， respectively. This performance has reached the excellent level reported at present. This study provides a new strategy for the preparation of high-performance ORR catalyst materials by dispersing active sites and increasing the porosity of catalytic materials.



Effects of Surface Hydrothermal Carbon Layer on the Photocatalytic Activity of Magnetic NiFe₂O₄ Octahedron

GUO Biao, ZHAO Chencan, LIU Xinxin, YU Zhou, ZHOU Lijing, YUAN Hongming, ZHAO Zhen

2022, 43(11):  20220472.  doi:10.7503/cjcu20220472

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A series of magnetic carbon-coated NiFe₂O₄ core-shell octahedron（NiFe₂O₄@C） was synthesized by hydrothermal carbonization of glucose. The thickness of carbon layer on the NiFe₂O₄ surface could be precisely tuned by controlling the content of glucose. The composition， structure， morphology and optical properties of NiFe₂O₄@C composites were characterized by X-ray diffraction（XRD）， Raman spectroscopy（Roman）， X-ray photoelectron spectroscopy（XPS）， scanning electron microscopy（SEM）， transmission electron microscopy（TEM） and UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）. The photocatalytic performance for the MB-degradation of various NiFe₂O₄@C were explored. It is found that the photocatalytic activity strongly depended on the thickness of carbon layer on the surface of NiFe₂O₄. The NiFe₂O₄@C-3 with 5.5 nm carbon layer is endowed with the best photocatalytic performance for the MB photodegradation. Fluorescence spectroscopy（PL）， transient photocurrent and electrochemical impedance spectroscopy（EIS） results show that the improvement of photocatalytic performance can be attributed to the formation of the heterojunction between the NiFe₂O₄ core and carbon shell， which effectively promotes the transmission and separation of photo-generated carriers. In addition， NiFe₂O₄@C possesses relatively high stability and retrievability， indicating that NiFe₂O₄@C has great potential for applications in sewage treatment.



Preparation of Bifunctional Metal-organic Framework Materials and Application in Catalytic Olefins Epoxidation

DONG Yanhong, LU Xinhuan, YANG Lu, SUN Fanqi, DUAN Jingui, GUO Haotian, ZHANG Qinjun, ZHOU Dan, XIA Qinghua

2022, 43(11):  20220458.  doi:10.7503/cjcu20220458

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Metal organic framework materials（MOFs） are coordination polymers formed by coordination. Recent studies have found that MOFs are the kind of heterogeneous catalysts with excellent catalytic performance due to their stable active sites in many reactions. In this paper， the ZnCo-MOF bimetallic catalyst material were prepared by the synthetic method of rotational hydrothermal crystallization using ZnO as the zinc source. X-ray diffraction（XRD）， Fourier transform infrared spectrum（FTIR）， scanning electron microscopy（SEM） and X-ray photoelectron spectro-scopy（XPS） were used to represent the morphology， structure and composition of the catalyst. The prepared catalyst can obtain epoxide with high conversion and high selectivity without adding any initiator or co-reducing agent in the air epoxidation reaction of catalyzed diolefin by microwave heating. The ZnCo-MOF catalyst synthesized by rotational hydrothermal method（110 r/min） has the best activity in the catalytic epoxidation of α-pinene and α-methylstyrene， which can obtain 86.3% and 99.8%（molar fraction） conversion， respectively， and the selectivity of the correspon-ding epoxides reach 93.8% and 94.3%.

Theoretical Exploration of Noncovalent Interactions Between Sc₃C₂@C₈₀ and ［12］Cycloparaphenylene Nanoring

LIU Yang, LI Wangchang, ZHANG Zhuxia, WANG Fang, YANG Wenjing, GUO Zhen, CUI Peng

2022, 43(11):  20220457.  doi:10.7503/cjcu20220457

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The encapsulations of fullerenes by carbon-nanorings are of great interest because of their unique molecular structure and special properties. The host-guest interaction between them can induce the orientation of metal ions and change the molecular electronic structure. However， due to experimental di?culties， there are many opportunities for the computational efforts to deeply research the intrinsic features of π-π noncovalent interactions of the fullerene?cycloparaphenylene（CPP） carbon-nanoring host-guest systems. Herein， the molecular carbon nanoring of ［12］cycloparaphenylene was used to hoop the C₈₀-based metallofullerene Sc₃C₂@C₈₀. The structures and properties of the host-guest complex were systematically characterized by density functional theory（DFT） calculations. It was found that ［12］CPP is deformed because of the asymmetrical attraction of ［12］CPP to Sc₃C₂@C₈₀. The centroids of Sc₃C₂@C₈₀ and ［12］CPP no longer coincide. The results also showed that the influence of rotation of Sc₃C₂@C₈₀ in ［12］CPP on the overall energy of the configuration is only 13.51 kJ/mol. Moreover， charge population analysis shows that 0.03 electrons are transferred from ［12］CPP to Sc₃C₂@C₈₀ during the formation of Sc₃C₂@C₈₀?［12］CPP. Weak interactions between host-guest systems can be further partitioned with the help of energy decomposition analysis（EDA）. EDA analysis shows that dispersion is dominant. These results provide theoretical support for the study of host-guest systems based on metallofullerenes.



Molecular Dynamics Simulation of the Physicochemical Properties of Trifluoromethanesulfonyl Fluoride Dielectrics

ZHANG Mi, TIAN Yafeng, GAO Keli, HOU Hua, WANG Baoshan

2022, 43(11):  20220424.  doi:10.7503/cjcu20220424

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Physicochemical properties of trifluoromethanesulonyl fluoride（CF₃SO₂F） dielectric medium， which is a promising eco-friendly insulation gas to replace SF₆ for the high-voltage electric applications， were calculated using molecular dynamics simulations. An optimized mPCFF force field was proposed and validated on the basis of the theoretically predicted molecular structures， internal rotation， dipole moments， and vibrational frequencies， which were in good agreement with the experimental and quantum chemical data. The physical properties of CF₃SO₂F in the phase envelope including vapor pressures， densities， heat capacities， enthalpies of vaporization， critical properties， together with the key transportation parameters including self-diffuse coefficients， dielectric constants， shear viscosities， and thermal conductivities， were examined systematically for the first time in the temperature range 243—323 K. In addition， the gas mixtures of CF₃SO₂F with N₂ or CO₂ buffer gas were investigated to compare with the electrical performance of SF₆ and C4/CO₂. A few critical suggestions on the use of CF₃SO₂F were proposed in terms of mixing ratio， liquefaction temperature， self-diffuse， and thermal conductivity for the purpose of realistic electrical applications.



Effects of Cu， Ni and Co Hetroatoms on Constructions and Electrocatalytic Properties of Fe-based Carbon Nanotubes

DING Qin, ZHANG Zixuan, XU Peicheng, LI Xiaoyu, DUAN Limei, WANG Yin, LIU Jinghai

2022, 43(11):  20220421.  doi:10.7503/cjcu20220421

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With the development of human society， the problems of energy crisis and environmental pollution increase obviously. In order to face these problems， developing a series of new energy storage devices is significance. Zn-air batteries（ZABs） is one of high specific volume density and low cost storage devices， which has been studied extensively. In this study， three double metal-based carbon nanotubes（CuFe@NCNTs， NiFe@NCNTs and CoFe@NCNTs） were obtained by adding Cu， Ni and Co as heteroatoms during the preparation of Fe-based carbon nanotubes and were used as the oxygen electrodes for ZABs. Then， scanning electron microscope（SEM）， N₂ adsorption-desorption isotherms were used to characterize the microstructures of samples. X-ray diffraction（XRD）， X-ray photo-electron spectroscopy（XPS） and Raman spectrum analysis were tested to confirm their chemical composition. The results show that carbon nanotubes could be synthesized successfully with all of three metal couples. However， the different metals doping nanotubes show the great difference on their morphologies and compositions. Cu elements doping shows the least influence on the structure of nanotubes. Besides， the chemical compositions and graphitization rations of carbon nanotubes were obviously changed after doped by all three heteroatoms. Simultaneously， three double metal carbon nanotubes exhibit bifunctional electrocatalytic performances both in oxygen reduction reaction（ORR） and oxygen evolution reaction（OER）. CuFe@NCNTs shows the greatest performances for ORR［onset potential is 0.92 V（vs. RHE） and half-wave potential is 0.81 V（vs. RHE）］ in three samples. NiFe@NCNTs shows the superior activities for OER（only a potential of 1.58 V is needed to reach a current density of 10 mA/cm²）， which is even better than that of IrO₂. Among the three assembled ZABs， CuFe@NCNTs based ZABs demonstrate a peak power density of 53 mW/cm²， both of NiFe@NCNTs based ZABs and CoFe@NCNTs based ZABs show excellent discharge rate capabilities. All of three cells show great cycles lifetime longer than 150 h， outperform Pt/C-IrO₂ one.



Constructing a Water-blocking Interlayer Containing Sulfonated Carbon Tubes to Reduce Concentration Polarization in Direct Methanol Fuel Cells

LIU Jie, LI Jinsheng, BAI Jingsen, JIN Zhao, GE Junjie, LIU Changpeng, XING Wei

2022, 43(11):  20220420.  doi:10.7503/cjcu20220420

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The sulfonated multi-wall carbon nanotubes（SO₃-MCNT） were prepared by introducing the benzenesulfonic acid functional group from 4-aminobenzenesulfonic acid into the oxidized multi-walled carbon nanotubes by a direct grafting method. The prepared sulfonated multi-walled carbon nanotubes were used as fillers and Nafion ionomer as binder to construct a new membrane layer upon one side of a commercial N212 proton exchange membrane using ultrasonic spraying， and then a composite membrane（SO₃-MCNT?N212） was obtained. The com?posite membrane was used to prepare fuel cell membrane electrode assembly（MEA） for direct methanol fuel cell（DMFC） testing. Compared with the MEA samples using ordinary N212 membrane， the performance of this MEA has been significantly improved. Further analysis showed that the introduction of the sulfonated multi-walled carbon nanotube membrane layer is able to reduce the transmembrane water migration from the anode to the cathode， alleviate the cathode flooding， thereby reducing the concentration polarization and improving the performance of the MEA.



Modified Quasichemical Model for Manifold Short-range Orders in Binary Solutions： Unity of Opposites for the Ordered Pairs

WANG Kun, ZOU Xingli, CAO Zhanmin, LI Chonghe, LU Xionggang

2022, 43(11):  20220391.  doi:10.7503/cjcu20220391

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Within the framework of the quasichemical model， assuming all ordered pairs of atoms to be distingui-shable， a modified quasichemical model for twofold short-range orders（SROs） was firstly constructed， and then several theoretical limits that the model can reach were discussed. These discussions were summarized and enhanced to establish the theory of unity of opposites for ordered pairs. Based on this theory， the modified quasichemical model for twofold SROs were further generalized， which leads to the successful development of the modified quasichemical model for manifold SROs. The model can efficiently describe the thermodynamic behavior of binary melts containing manifold short-range ordering configurations. The Bi-K melt with at least two observed SROs were selected to test the rationality and reliability of the model. The results show that， apart from the coordination numbers， only four model parameters are needed to reasonably reproduce all the thermochemical data of the binary melt.



Influence Mechanism of Filling Transition Metal Oxide Catalyst with Different Components on Nitrogen Fixation in Dielectric Barrier Discharge

LIU Kun, YIN Yuan, GENG Wenqiang, XIA Haotian, LI Hua

2022, 43(11):  20220278.  doi:10.7503/cjcu20220278

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In order to promote the synergistic catalytic nitrogen fixation effect of dielectric barrier discharge（DBD）， the single， binary and ternary supported catalysts with different Mn/Co/W elements were prepared in this paper， and the catalysts were placed in the DBD air gap for plasma co-catalytic nitrogen fixation reaction. The catalysts were characterized by XRD， SEM and EDS. The concentration of total nitrogen in liquid phase was determined by ultraviolet spectrophotometry and the experimental results showed that the concentration of total nitrogen in the experimental group filled with catalyst was significantly increased compared with that in the untreated group. Fourier transform infrared spectroscopy（FTIR） was used to detect the gas-phase products of DBD with or without catalyst filling. It was proved that catalyst filling could promote the formation of NO₂ and N₂O₅ in space. DBD gas-phase chain reactions and the principle of catalysis revealed that the total nitrogen concentration was increased because the catalyst provided a mass of oxygen vacancies in the plasma coordination process， making NO _x fully oxidized. Multiple compound catalysts can further promote the nitrogen fixation effect through the transformation of metal element valence state and energy transfer on the basis of single type. The highest total nitrogen concentration of the ternary compound catalyst Mn₃WCo/γ-Al₂O₃ experimental group was obtained at the voltage of 22 kV， which was 119.13 mg/L. Compared with the maximum value of unfilled catalyst group， it increased by 71.61%.



Polymer Chemistry

Monte Carlo Simulation on Self-healing Behaviour of Hydrogen-bonded Hydrogel

GAO Huiling, CAO Zhenzhen, GU Fang, WANG Haijun

2022, 43(11):  20220482.  doi:10.7503/cjcu20220482

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We present a lattice gas model for the cross sections of a hydrogen bonded（HB） self-healing hydrogel， and then the Monte Carlo method is employed to simulate its self-healing behavior. The peak of the specific heat in the self-healing process is obviously observed， by which the critical association fraction of hydrogen bonds is obtained to determine whether the self-healing can take place. Furthermore， the influences of the HB strength， cooperation effect， and the separation between the cross sections on the self-healing process are investigated. Consequently， the self-healing of the HB hydrogel is identified as the first-order thermodynamic phase transition， as expected. The HB strength plays the key role not only in thermodynamics but also in dynamics of self-healing process.



Low Critical Dissolution Temperature Behavior of β⁃Cyclodextrin and Its Application in the Preparation of β⁃Cyclodextrin Sheet Crystal with Ordered Nano⁃channel

TAN Lejian, ZHONG Xuanshu, WANG Jin, LIU Zongjian, ZHANG Aiying, YE Lin, FENG Zengguo

2022, 43(11):  20220405.  doi:10.7503/cjcu20220405

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In this paper， β-cyclodextrin（β-CD） was dissolved in N，N-dimethylformamide solution（DMF）， and a large number of white crystals were precipitated after the solution was heated to 140 ℃. It was found that the precipitated crystals were β-CD sheet crystals by scanning electron microscopy（SEM） as well as infrared Spectroscopy（IR） and Nuclear magnetic resonance（NMR）. Thermogravimetric analysis（TGA） and differential scanning calorimetry（DSC） analysis showed that the sheet crystals had the same physical and chemical properties as β-CD raw materials. The X-rays diffraction（XRD） results showed that β-CD sheet had different crystalline structure from β-CD raw materials. The XRD patterns of β-CD crystal with open-chanel crystalline structure were simulated by Diamond software， which is consistent with that of β-CD sheet， indicating that β-CD sheet has ordered open-channel crystalline structure. Brunauer-Emmett-Tellern（BET） measurement and phenolphthalein adsorption experiment further confirmed that β-CD sheet had larger specific surface area and better adsorption performance than β-CD raw materials.



Preparation and Properties of High Heat-resistant Polyimide Films for Flexible OLED

JIAO Long, DAI Xuemin, MU Jianxin, DU Zhijun, WANG Hanfu, DONG Zhixin, QIU Xuepeng

2022, 43(11):  20220390.  doi:10.7503/cjcu20220390

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The glass transition temperature（T_g） of greater than 450 ℃ and the coefficient of thermal expansion （CTE） between 0 and 5×10^-6 K^-1 are required for the application of polyimide（PI） films as flexible organic light- emitting display（OLED） substrates. In order to improve the thermal properties of PI films， a series of novel PI films was prepared by the copolymerization of homemade 2，7-diaminoxanthone（2，7-DAX） with pyromellitic acid dianhydride（PMDA） and 2-（4-aminophenyl）-5-aminobenzoxazole（BOA）. The aggregation structure， heat resistance， dimensional stability and mechanical properties of the films were investigated. The results show that the rigidity and linearity of PI molecular chain are improved by the structure of xanthone and benzoxazole， and the molecular chain is closely packed and oriented in the plane. The synthesized PI film has excellent comprehensive properties， with T_g>408 ℃， CTE between -5.0×10^-6 and 8.1×10^-6 K^-1， tensile strength>140 MPa， tensile modulus>4.2 GPa， the elongation at break between 7.1% and 20%， and the thermogravimetric decomposition temperature（T_5%） between 601 and 624 ℃. Among them， PI-50 and PI-60 films have ultra-high T_g（>450 ℃） and ultra-low CTE（2.1×10^-6 K^-1 and 1.6×10^-6 K^-1）， respectively. The PI films prepared have potential application prospects as flexible OLED substrate materials.



Synthesis and Properties of Polypeptoid Hydrogels Containing Sulfonium Groups

YAN Shuting, YAO Yuan, TAO Xinfeng, LIN Shaoliang

2022, 43(11):  20220381.  doi:10.7503/cjcu20220381

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Triblock copolypeptoid poly（N-allylglycine）-b-polysarcosine-b-poly（N-allylglycine）（PASA） was prepared by primary amine-initiated controlled ring-opening polymerization of sarcosine N-thiocarboxyanhydride （Sar-NTA） and N-allylglycine N-thiocarboxyanhydride（NAG-NTA）. Followed by cross-linking via thiol-ene click reaction between the allyl groups on the PASA side chains and thiols groups on 3，6-dioxa-1，8-octanedithiol， polypeptoid hydrogels（HG） with different molar fraction of sarcosine（Sar）， HG-Sar49% and HG-Sar64%， were obtained. A large amount of thioether groups were formed through the thiol-ene click reaction， which could further react with epoxide compounds to generate sulfonium groups on the network of PASA hydrogels. Thus， sulfonium- containing polypeptoid hydrogels（S⁺HG） with intrinsic antibacterial properties were successfully prepared. S⁺HG showed fast and excellent water absorption ability， which reached the water absorption balance within 1 min and had a saturation swelling rate up to 2024%. S⁺HG was composed of regular continuous sponge-like structures， and could withstand certain external stresses such as shearing， friction and extrusion. S⁺HG exhibited strong broad-spectrum antibacterial ability， and the antibacterial rates against gram-negative Escherichia coli（E. coli） and gram-positive Staphylococcus aureus（S. aureus） were over 99.99%.



Preparation and Properties of Bifunctional Polydimethysiloxane/Copper Nanowire Composite Films

ZHANG Tao, SHAO Liang, ZHANG Menghui, MA Zhonglei, LI Xiaoqiang, MA Jianzhong

2022, 43(11):  20220359.  doi:10.7503/cjcu20220359

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A polydimethylsiloxane/copper nanowires（PDMS/CuNWs） composite film was prepared by an environmental-friendly glucose templating method and an improved wet chemical reduction method. PDMS/CuNWs composite adopts a “sandwich-like structure” design. It effectively solves the problem that copper is easily oxidized in the air， which leads to a significant drop in electrical conductivity. At the same time， a bifunctional lightweight and flexible composite film with excellent electromagnetic shielding and photothermal conversion properties is obtained. The performance retention rate of the composite film with an CuNWs area density of 1.6 g/cm² can reach up to 99.07% after 1000 repeated bending times； the total electromagnetic shielding efficiency of the composite film with an area density of 2.4 g/cm² in the X-band reaches 30.1 dB， and the shielding efficiency reaches 99.9%； meanwhile， under the irradiation of near-infrared light of 2 W/cm²， the surface temperature of the composite film is as high as 211.2 ℃ after heating for only 15 s. PDMS/CuNWs composite has a very fast photothermal response and conversion efficiency.



Gas Separation Performance of Polyimide Homogeneous MembranesContaining tert-Butyl Groups

WANG Shoubai, WU Xiuming, SHU Chen, ZHONG Min, HUANG Wei, YAN Deyue

2022, 43(11):  20220357.  doi:10.7503/cjcu20220357

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A series of soluble aromatic polyimides containing tert-butyl groups were synthesized by the one-pot high-temperature polycondensation. The corresponding homogeneous membranes were prepared by the solution casting method and then their gas separation performances were measured. The effects of dianhydride chemical structures and temperature on the gas separation performance of these polyimide membranes were investigated in detail. For five kinds of gases（including H₂， N₂， O₂， CO₂ and CH₄）， all of them exhibited good gas permeability with the high gas permselectivity， especially the polyimide membranes containing 4，4'-（hexafluoroisopropylidene）diphthalic anhydride（6FDA） or pyromellitic dianhydride（PMDA）. Except for CO₂， the gas permeability coefficients increased with increasing the temperature for these two kinds of polyimide membranes， while the diffusion coefficients and solubility coefficients of the five gases were increased with increasing the temperature.



Thermal Degradation Mechanism of Bio-based Polybutylactam Plasticized by Ionic Liquids

CHANG Sihui, CHEN Tao, ZHAO Liming, QIU Yongjun

2022, 43(11):  20220353.  doi:10.7503/cjcu20220353

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Polybutyllactam（PBL） has attracted increasing attention in recent years since it can be degraded in various natural environments including water. However， due to the melting point is close to the thermal decomposition temperature， it cannot be melting processed and the application is limited. Therefore， reducing melting point and improving thermal stability of PBL becomes an urgent problem. Herein， two imidazolium-based ionic liquids（ILs）， hydrophobic 1-butyl-3-methyl-imidazolium hexafluorophosphate（［BMIM］PF₆） and hydrophilic 1-butyl-3-methyl-imidazolium tetrafluoroborate（［BMIM］BF₄）， were applied to plasticize PBL， and their effects on the crystallization and thermal properties of PBL were investigated. It was found that both ILs weakened the intermolecular hydrogen bonds of PBL， inhibited the growth of PBL crystals at the （200） crystal plane and reduced the crystallinity of PBL. When the addition mass fraction of ILs was 5%， the melting temperature of PBL was decreased by 7—8 ℃. Compared with pure PBL film， the thermal stability of ［BMIM］BF₄ plasticized PBL film decreased slightly， while that of ［BMIM］PF₆ plasticized PBL film improved. The results of thermal kinetic analysis of ［BMIM］PF₆ plasticized PBL film showed that the activation energy（E） of thermal decomposition is 46.68 kJ/mol， and the reaction order（n） is 1. The most probable mechanism function model of thermal degradation follows the Mampel power law（first order）. It indicates that when PBL is thermally stimulated， it irregularly nucleates at the interface between polymer and decomposition products. The reaction core is of reactivity and the reaction gradually expands until the end.



Preparation of PTFE/PAA/Nafion Composite Membrane by Aqueous Polymerization of Acrylic Acid and Its Properties

JIA Hongjun, ZHANG Jiatao, MA Zhuoli, WANG Heng, YANG Xinyu, YANG Jiazhi

2022, 43(11):  20220350.  doi:10.7503/cjcu20220350

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Low cost proton membrane can be prepared by using cheap polytetrafluoroethylene as substrate and a small amount of Nafion film and polytetrafluoroethylene（PTFE） film. But hydrophobic PTFE film and hydrophilic Nafion do not combine well. In this paper， the surface of hydrophobic PTFE material was designed. Firstly， the hydrophobic PTFE film surface was modified with acrylic acid， and then sprayed with hydrophilic Nafion film to complete the preparation of low-cost PTFE/PAA/Nafion film. The results showed that the water contact angle of PTFE material before modification was 150°， and that of composite film after modification was 55.6°. The mechanical strength and size stability（fracture strength of 25.2 MPa， swelling rate of 11.9% at 80 ℃） of the composite film were better than those of Nafion117 film， while the amount of Nafion was reduced by 60%. The composite membrane has high proton conductivity（up to 131.9 mS/cm at 80 ℃）， which is close to that of Nafion117 film， and the maximum power density can reach 404.2 mW/cm².



In⁃situ Liquid Exfoliation of Montmorillonite Nanosheets in Poly（lactic acid） to Resist Oxygen Permeation

XU Huan, KE Lyu, TANG Mengke, SHANG Han, XU Wenxuan, ZHANG Zilin, FU Yanan, HAN Guangdong, CUI Jinsheng, YANG Haoran, GAO Jiefeng, ZHANG Shenghui, HE Xinjian

2022, 43(11):  20220316.  doi:10.7503/cjcu20220316

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As one of the most representative bioplastics， poly（lactic acid）（PLA） has been identified as an ecofriendly candidate for packaging medicine and food， holding distinct advantages of high strength and good biocompatibility. The application prospects， however， are largely dwarfed by the poor ductility and low resistance to gas permeation. In this work， the high-shear liquid exfoliation method was proposed to effectively transform the montmorillonite（MMT） to few-layer MMT nanosheets（MNSs）， which thereby enabled in situ incorporation into the PLA matrix. Using a facile blade coating method， the fully biodegradable PLA nanocomposite films were prepared， with the MNS content ranging from 2% to 5% and 10%. The MNSs were found to be well exfoliated with a planar distance up to 3.11 nm， as accompanied by good alignment and strong interfacial adhesion within the composite films. These structural features conferred remarkable improvements in the mechanical properties and gas barrier performance for the composite films. This effort is of important significance for effective exfoliation of two-dimensional（2D） nanosheets， as well as fabrication of strong and high-barrier biodegradable nanocomposites.



Fabrication and Properties of Epoxy Vitrimer Based on Multiply Dynamic Covalent Bonds

YANG Weiming, XI Aoqian, YANG Bin, ZENG Yanning

2022, 43(11):  20220308.  doi:10.7503/cjcu20220308

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Traditional epoxy networks were wildly applied in composites， adhesives， coatings， electronic packaging and insulating materials， due to their excellent properties and stable network structure. However， once epoxy networks are formed， they cannot be reprocessed. When epoxy networks are damaged during the serving time， they cannot be self-healed. Epoxy vitrimers networks with dynamic reversible covalent bonds can reorganized their network typology under external stimuli， contributing to network reprocessing and self-healing. Currently， most epoxy vitrimers show a high temperature for reprocessing and self-healing， consuming high energy. Herein， the epoxy vitrimers with tri-dynamic covalent bonds（boronic ester bond， disulfide bond and ester bond） were fabricated by epoxy-thiol “click” reaction and epoxy-carboxylic acid reaction. The structures of the prepared epoxy vitrimers were characterized by Fourier transform Infrared spectrometer（FTIR） and Raman spectroscopy， and hydrogen bonds were found in the prepared epoxy vitrimers contributing to improvement of crosslink density. Meanwhile， the thermal stability， thermo-mechanical properties and mechanical properties of the prepared epoxy vitrimers were investigated by thermogravimetry（TG）， dynamic mechanical analysis（DMA） and tensile testing. Furthermore， self-healing， welding， shape memory and reprocessing capabilities of the prepared epoxy vitrimers were researched. The results display that at 80 ℃ the scratches on the prepared epoxy vitrimers can be fully recovered and the welding recovery of tensile strength of the prepared epoxy vitrimers is >80%， indicating excellent functionality.