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10 January 2019, Volume 40 Issue 1

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Cover and Content of Chemical Journal of Chinese Universities Vol.40 No.1(2019)

2019, 40(1):  0-0. 

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Inorganic Chemistry

Extraction of Trivalent Americium and Europiumfrom Nitric Acid Solution with Di(2-ethylhexyl)dithiophosphinic Acid^†

ZHANG Lirong,WANG Zhipeng,LIU Ying,XU Chao,CHEN Jing,DING Songdong

2019, 40(1):  1-10.  doi:10.7503/cjcu20180133

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The extraction of Am³⁺ and Eu³⁺ from HNO₃ solution with di(2-ethylhexyl)dithiophosphinic acid(D2EHDTPA) were investigated using n-dodecane as diluent. Influences of acidity, ligand concentration, N{\mathrm{O}}_3^{-} concentration and saponification on the extraction of Am³⁺ and Eu³⁺ were evaluated. The distribution ratio values of both Am³⁺ and Eu³⁺ increased with increasing pH values from 2.5 to 4.5, and also with increasing the ligand concentration from 0.10 mol/L to 0.50 mol/L. The maximum value of separation factor(SF_Am/Eu) can reach 4000 at pH=3.65. Slope analyses indicated the main formation of 3:1 and 2:1 complexes of D2EHDTPA with Am³⁺ and Eu³⁺, respectively. The nitrate ion did not take part in the extraction reaction of D2EHDTPA with Am³⁺ or Eu³⁺. The extractability of D2EHDTPA was significantly enhanced through the saponification with NaOH solution. SF_Am/Eu values could be improved to the magnitude of 10⁴, and the extraction capacity was approximately 60% of the theoretical value. Furthermore, the complexation behaviors of D2EHDTPA with Eu³⁺ were also investigated by electrospray ionization mass spectrometry(ESI-MS), Fourier transform infrared(FTIR) and isothermal titration calorimetry(ITC). The composition and stability constants(lgβ) of the complex of D2EHDTPA with Eu³⁺, as well as the thermodynamic parameters(ΔH, ΔS and ΔG) were obtained.



Preparation and Electrical Contact Properties of Palladium-doped Multi-walled Carbon Nanotubes^†

SUN Mengmeng,CHANG Chunrui,ZHANG Zhiming,AN Libao

2019, 40(1):  11-17.  doi:10.7503/cjcu20180506

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Multi-walled carbon nanotubes(MWCNTs) were oxidized by mixed acid, and immersed into the electroless deposition solution of palladium. After ultrasonicating, resting, and stirring respectively for 5 or 10 min, palladium-doped MWCNTs were prepared, and their morphology and structure were characte-rized. The results showed that the nanoparticles were uniformly distributed onto the MWCNTs with uniform and moderate particle size and doping amount after 5 min of stirring. At the same time, the composition of the doped nanoparticles was detected as zero-valent palladium and the doping type was p-type. In the electrical contact performance test, the contact resistance between the palladium-doped CNTs and the gold electrode was significantly improved, and the average value of the resistance decreased by nearly 71.09%.



Effect of Temperature on Morphology and Supercapacitor Performance of Carbon Nano-spheres^†

LIU Hao,ZHAO Dingxuan,GONG Guodong,ZHANG Zhuxin,JIA Tuo,CHEN Hanzhe

2019, 40(1):  18-23.  doi:10.7503/cjcu20180474

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Abstract Sodium was used as reductant to break the C—Cl bond and C—H bond in the solvent, trichloroethane(C₂H₃Cl₃) and dichloroethane(C₂H₄Cl₂), under solvothermal condition(100—150 ℃) to prepare carbon nano-spheres(CNSs). The X-ray diffraction pattern shows that the sample has a graphite-like structure. The diffraction signal of the sample is wide and weak, indicating that the sample has a poor crystallinity and an amorphous structure. The Raman spectra shows that the sample has a relative high degree of disorder. The results of SEM and TEM show that the CNSs have better monodispersion at higher reaction temperatures. The particle size of the CNSs increases with increasing temperature, and the results of electron diffraction in the selected area indicate that the CNSs are internally amorphous graphite structure. The results of the lithium-ion battery test using the CNSs as the negative electrode material show that the specific capacity after 50 cycles is 941 mA·h/g, and the Coulomb efficiency is close to 100%, the discharge capacity retention rate is 103.7%, indicating that the CNSs have good cycle stability. The performance of CNSs prepared at different temperatures as supercapacitor material was tested. The CNSs prepared under 120 ℃ show higher specific capacitance and lower internal resistance. The specific capacitance is up to 130 F/g. The attenuation of specific capacitance is less than 14% after 1000 cycles, which shows higher stability.



Preparation and Adsorption Performance for U(Ⅵ) of ZnO@ZIF-8 Core@Shell Microspheres^†

WANG Fuxiang,CHEN Ziyu,YANG Weiting,LIU Lijuan,REN Guojian,LIU Yanfeng,PAN Qinhe

2019, 40(1):  24-29.  doi:10.7503/cjcu20180469

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ZnO@ZIF-8 core@shell microspheres were synthesized by a hydrothermal method and applied for the efficient adsorption of U(Ⅵ) from aqueous solution. The size of synthesized ZnO@ZIF-8 core@shell microspheres was in the range of 1—7 μm. The batch experimental results revealed that the sorption of U(Ⅵ) on ZnO@ZIF-8 was strongly dependent on pH, and the maximum sorption capacity of U(Ⅵ) on ZnO@ZIF-8 was 145.32 mg/g at pH=4.0. The adsorption mechanism could be mainly attributed to the coordination and the hydrogen bonding between ZIF-8 framework and U{\mathrm{O}}_2^{2+} ions. Considering that the content of ZIF-8 in the composite microspheres was only 12.6%, the unit adsorption capacity of U(Ⅵ) is up to 1137 mg/g.



Synthesis, Characterization and DNA, BSA Interactions of Mononuclear Ruthenium Complexes with Modified 1,10-Phenanthrolines Ligands^†

ZHAO Yachen,LI Ji,ZHANG Peipei,LIU Shuxian,WEI Daina,SU Zhi,QIAN Yong,WANG Feili,Peter John Sadler,LIU Hongke

2019, 40(1):  30-40.  doi:10.7503/cjcu20180370

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Three novel arene-ruthenium complexes(1—3) were synthesized from 2-(4-pyridinyl)imidazo[4,5-f]-1,10-phenanthroline(L₁) and [(η⁶-cymene)Ru(μ-Cl)Cl]₂. A polypyridine-ruthenium complex(4) was synthesized from RuCl₃ and 2-(4-(1H-imidazol-1-yl)phenyl)-1H-imidazo[4,5-f]-1,10-phenanthroline(L₂). All the complexes were characterized by ¹H NMR, elemental analysis and ESI-MS. UV-Vis, circular dichroism and fluorescence techniques were used to study the interactions between complexes 1—4 and calf thymus DNA(CT-DNA) or BSA, respectively. Viscosity measurements were carried out to clarify further the interaction mode of complexes 1—4 with DNA. In addition, the interactions of complex 4 with pBR322 DNA were studied by gel electrophoresis, and the pH-related fluorescence spectra of complex 4 were recorded in various pH solutions. The results show that these complexes could interact with DNA via intercalation and disturbing the secondary structure of DNA. The static quenching for complexes 1—4 were observed when these complexes were titrated with BSA protein. Only one binding site was observed between these complexes and BSA and the binding constants were calculated. Under the UV light(365 nm), complex 4 could generate ¹O₂ and cleave pBR322-DNA efficiently and its fluorescencewere enhanced more than 56% when the solution pH was changed from 11.37 to 1.74.



Analytical Chemistry

Squaramide Fluorescence Probe for Chiral Recognition of α-Amino Acids^†

BAI Lei,HUO Shuhui,CHEN Jing,LU Xiaoquan

2019, 40(1):  41-46.  doi:10.7503/cjcu20180641

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Four novel squaramide fluorescence probes were synthesised using natural amino acids as chiral sources, which featuers concise synthetic route, simple work-up and purification without column chromatography. The chiral recognition effects of these squaramide probes for phenylalanine, valine and proline were tested using fluorescence spectrum, which indicated that probe 5 could effectively discriminate two enantiomers of phenylalanine. The fluorescence intensity of probe 5 was remarkably enhanced after adding L-phenylalanine; on the contrary, it was observably reduced when D-phenylalanine was added, and the fluorescence intensity ratio of two enantiomers(I_L/I_D) was up to 2.4.



Comparative Study of Absorption and Fluorescence Spectra of Glycitein and Glycitin^†

LI Wenhong,WANG Danyang,CAO Jinjin,WEI Yongju

2019, 40(1):  47-54.  doi:10.7503/cjcu20180421

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The absorption and fluorescence spectra of glycitein and glycitin in aqueous solutions with different pH values were investigated in detail, and the reasons why the two presented different spectral characteristics were explained in the viewpoint of molecular structure. The molecular form of glycitein is essentially no fluorescence. Under weak alkaline condition, the 7-OH proton ionization causes a redshift of the absorbance peak at 320 nm to 348 nm. The proton ionization constant is measured to be pK_a1=7.08±0.04, by a pH-photometric method. The univalent-anion form of glycitein exhibit a fairly strong fluorescence with maximum excitation and emission wavelengths(λ_ex/λ_em) of 334 nm/464 nm, and the fluorescence quantum yield is measured to be 0.049. In alkaline solutions, the ionization of 4'-OH proton of glycitein causes a redshift of the absorbance peak at 254 nm to 260 nm, the ionization constant is pK_a2=9.96±0.01. The molecular form of glycitin has almost no fluorescence. Under alkaline conditions, the ionization of 4'-OH proton causes a redshift of the absorbance peak at 256 nm to 280 nm, with pK_a=9.81±0.03. The anion form of glycitin has almost no fluorescence, but the cleavage reaction of γ-pyrone ketone ring occurs under hot and alkaline conditions and produces a fairly strong fluorescence, with λ_ex/λ_em of 288 nm/388 nm, and the fluorescence quantum yield of the cleavage reaction product is 0.056. Although the relationship between glycitin and glycitein is as that of glycoside and aglycone, but glycitin cannot be converted to glycitein by means of hydrolysis of glycoside under hot alkaline conditions. The fluorescence enhancement mechanisms of these two are essentially different.



Turn-off Fluorescence of Gold Nanoclusters for Sensing of Ferric Ion^†

LIU Qianrong,CAI Huiwu,GUAN Ming,QIAO Juan,QI Li

2019, 40(1):  55-61.  doi:10.7503/cjcu20180369

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D-Tryptophan-stabilized gold nanoclusters(D-Trp@AuNCs) were prepared by a simple one-pot synthesis protocol and displayed a specific response to Fe³⁺. The resultant AuNCs exhibited a strong blue fluorescence with the maximum emission at 440 nm wavelength. Due to the aggregation-induced fluorescence quenching mechanism, appearance of Fe³⁺ led dramatic fluorescent intensity decrease of AuNCs rather than other cations. Detection limit of the proposed assay for Fe³⁺ was 33.1 nmol/L, with a good linear range of 0.3—500.0 μmol/L(R²=0.9997). D-Trp@AuNCs were further applied in monitoring Fe³⁺ in real water samples, providing a new way for fabrication of AuNCs based fluorescent probes and showing great potential in environmental analysis.



Molecularly Imprinted Hollow Spheres for the Solid Phase Extraction of Protein^†

MENG Zihui,WANG Yifei,XIE Tengsheng,CHEN Wei,QIU Lili,XUE Min

2019, 40(1):  62-68.  doi:10.7503/cjcu20180327

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Molecularly imprinted polymer was widely used as the stuffing of solid phase extraction(SPE) due to its high selectivity. Hb isolation from complex matrix was established based on molecularly imprinted solid phase extraction(MISPE). Mono-dispersed molecularly imprinted hollow spheres(MIHS) of hemoglobin(Hb) were synthesized using silica nanospheres as the sacrificial matrix. It is proved that the MIHS with good monodispersion and uniform particle size by TEM scanning was suitable for SPE enrichment matrix. Therefore, the extraction of Hb, bovine serum albumin(BSA) and cytochrome C(Cyt C) by MIHSs was investigated by SPE combined with liquid chromatographic method. The recovery of Hb was higher than 80% in phosphate buffer solution(pH=7) while it was lower than 50% for RNase A and Cyt C. Meanwhile, the degree of precision(RSD) was lower than 5%. Compared to the surface imprinted silica(SIS), the MIHS had good recognition and fast adsorption-desorption dynamics for Hb. Moreover, this method was also confirmed in real sample, and the adsorption of Hb was 82% in the spiked bovine serum.



Organic Chemistry

Mass Spectrometric Analysis of N-Glycans of Glycoprotein Separated by SDS-PAGE Gel from Ginkgo Seed^†

LI Cheng,WANG Chengjian,JIN Wanjun,HAN Jianli,YANG Meifang,GAO Xi,HUANG Linjuan,WANG Zhongfu

2019, 40(1):  69-75.  doi:10.7503/cjcu20180456

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The glycoproteins in Ginkgo seeds were separated and isolated by sodium dodecyl sulfate polyacry-lamide gel electrophoresis(SDS-PAGE). The N-glycans released from glycoproteins were qualitatively and quantitatively analyzed by electrospray ionization mass spectrometry(ESI-MS) and on-line liquid chromatography-mass spectrometry(LC-UV-MS/MS²). As a result, eleven glycoproteins containing oligomannose type glycans(4.88%) and complex type glycans(95.12%) were obtained. And most of the N-glycans were modified by the core α-1, 3- and β-1, 2-xylose in the 21000, 36000 and 50000 glycoproteins, which accounted for 68.23%, 64.37% and 75.09%, respectively. This study can highlight the understanding of protein glycosylation in Ginkgo and provide foundation in the research of Ginkgo biloba seed allergens.



Effects of Cucurbit[8]uril on the Solubility, Stability and Antioxidation of Cyanidin^†

JIANG Jing,HUANG Yali,ZHANG Qilong,XU Hong,SUN Xiaohong

2019, 40(1):  76-82.  doi:10.7503/cjcu20180448

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The inclusion of cucurbit[8]uril(Q[8]) with cyanidin(Cy) was investigated and charactrized by means of nuclear magnetic resonance spectrometer, infrared spectroscopy and UV-visible spectrophotometer absorption spectroscopy. The results showed that Q[8] and Cy could form a 1:1 host-guest complex in acid aqueous medium and the host-guest binding constant was determined to be 1.51×10⁶. Phase solubility study results suggested that Q[8] could increase the solubility of saturated Cy solution up to 12.21 times, and the results of time-dependent UV-Vis absorption spectra indicated that the stability of Q[8]/Cy solution was 2.58 times higher than that of Cy solution in the same experimental conditions. The results of anti-oxidation experiments showed that both Q[8]/Cy inclusion compound and Cy showed good antioxidant activity.



Structure Prediction and Screening of Oligonucleotide Aptamers Target Cε3-Cε4 Protein^†

LIU Zhongcheng, LIU Shifang, ZHANG Su, YANG Yanlei, LI Fei, ZHANG Nan, YUAN Xin, ZHANG Yanfen

2019, 40(1):  83-89.  doi:10.7503/cjcu20180428

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The prediction and selection of binding sites between aptamers and targets are the key steps in SELEX process, however, the conventional screening process is complicated. As a new convenient screening method, the virtual screening based on computer has widely used in aptamers screening. The nucleic acid-protein dock(NPDock) program was used to predict and screen the binding site of Cε3-Cε4 protein and its aptamer A1 based on their molecular docking, and the key site of binding to Cε3-Cε4 protein was screened. According to the amino acid residues and bases in the binding interface between the protein and the DNA complexes by virtual docking, the results showed that the amino acid in the binding interface is most capable of enriching the base G, followed by the ability of enriching the base T and the base C. An efficient optimization method was established based on NPDock docking, which would provide an experimental reference for related researches.



Detection of Egg White Lysozyme Oligomers Based on Fluorescence Lifetime of ThT^†

LI Cheng,SONG Jixue,LIU Tingting,LI Yan,LIU Bingnan,WANG Liang,XIAO Shan,LI Lin,GENG Xuhui,WANG Jihui

2019, 40(1):  90-95.  doi:10.7503/cjcu20180397

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Thioflavin T(ThT) fluorescence lifetime was used to detect aggregates states by time-resolved fluorescence. The protein aggregation was made by the egg white lysozyme in vitro. The characteristics of the oligomer and fibril were determined by means of transmission electron microscopy, ThT steady-state fluorescence and the growth kinetic curve of aggregation. The time-correlated single-photon counting technique was used to measure the fluorescence lifetime of ThT incubation with the aggregations. It calculated the fluorescence lifetime by fitting to the double exponential equation. The results of circular dichroism speculated that the structure of different aggregates was different and affected the fluorescence lifetime of ThT. It demonstrated that ThT fluorescence lifetime can distinguish protein monomers, oligomers and fibrils, and monitor the formation of protein oligomers. The results provide a basis for the monitoring of oligomer substances in the proess of sub-sequent pathological protein aggregation.



Physical Chemistry

Experimental and Theoretical Studies of Action Mechanism of an Octadecylamine-based Molecular Assembly on Mild Steel^†

MA Yucong,FAN Baomin,HAO Hua,LÜ Jinyu,FENG Yunhao,YANG Biao

2019, 40(1):  96-107.  doi:10.7503/cjcu20180589

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A supramolecular complex CDDA was prepared based on β-cyclodextrin(β-CyD) and octadecylamine(ODA). Four possible configurations of CDDA might coexist in the supramolecular system based on molecular dynamics simulation(MD). The corrosion inhibition effect and mechanism of CDDA for Q235 steel in the condensate water was evaluated via dynamic weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy(EIS), coupling with scanning electron microscopy(SEM), atomic force microscopy, contact angles, X-ray photoelectron spectroscopy(XPS) and attenuated total reflection infrared spectroscopy(ATR-FTIR). The inhibition efficiency for mild steel in the condensate water could reach 94.1% with 1 mmol/L CDDA at 35 ℃. The corrosion mechanism of mild steel in the condensate water was not altered in the presence of CDDA; however, both the anodic and cathodic processes were inhibited along with the elevated polarization resistance. CDDA could be treated as a mixed-type inhibitor with predominantly anodic dominant. The results of XPS and ATR-FTIR indicated that ODA could be released from CDDA at on the metal/solution interface and form a protective monolayer film. The adsorption process could be well fitted by the Langmuir adsorption isotherm. Molecular dynamics simulations provided the visual evidence of the assembly mechanism of CDDA on the mild steel surface. The release of ODA from CDDA and assembly mechanism on the steel/solution interface were verified by MD and quantum chemical calculations based on density functional theory.



NMR Spectroscopic Study on Binary Sodium Silicate Glass Based on the Fine Structure^†

WU Zhidong,YOU Jinglin,WANG Jian,WANG Min,HE Yingxia,YANG Yejin

2019, 40(1):  108-114.  doi:10.7503/cjcu20180558

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A series of fine structure denotations(Q_i^{\mathit{jklm}}) was applied to analysis NMR spectra of binary sodium silicate glasse, and a variety of clusters was simulated by quantum chemistry ab initio. The results shows that the ²⁹Si chemical shift of the fine structure with the same Q_i is linearly related to the bridging oxygen bond angle. The chemical shifts of the experimental Q_i^{\mathit{jklm}} structure does not fluctuate with the glass’ composition, and the Gaussian peak of the Q_i^{\mathit{jklm}} structure is narrower. It is indicated that the fine structure characterization is a representation of the basic characteristic structure of the binary sodium silicate glass. It is found that there is a certain gap between theoretical values and experimental values. The results shows that there are multiple configurations of Q_i^{\mathit{jklm}} structures coexisting in the glass, and the interaction between neighboring structures was characterized by NMR. However, the Q_i^{\mathit{jklm}} structural characterization can describe the configuration of various silicate-oxygen tetrahedron more precisely.



Theoretical Study on Adsorption of α,β-Unsaturated Aldehydes on Ni-Pt(111) Surface^†

LUO Wei,FANG Lei,MENG Yue,XUE Jilong,CHEN Tao,XIA Shengjie,NI Zheming

2019, 40(1):  115-122.  doi:10.7503/cjcu20180551

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The adsorption configurations of crotonaldehyde and cinnamaldehyde molecules on Pt-Ni-Pt(111) surface and their electronic properties were studied with density functional theory(DFT). The adsorption configurations and adsorption energy values illustrate that synergistic adsorption of crotonaldehyde and cinnamaldehyde molecules on Pt-Ni-Pt(111) surface with C=O and C=C bonds are most stable under the coverage of 1/25 ML. Moreover, the adsorption energy values of cinnamaldehyde on Pt-Ni-Pt(111) surface are much larger than that of crotonaldehyde. By analyzing Mulliken atomic charge population and the deformation density, it is found that the cinnamaldehyde molecule transfers more electrons to the Pt-Ni-Pt(111) surface and interact more strongly. The result of partial density of states(PDOS) indicates that the main reason for the adsorption is due to the interaction of the p orbital electrons of the unsaturated aldehyde molecules with the d orbital electrons of metal surface. And, due to the presence of the phenyl group, the cinnamaldehyde molecule is parallel to the surface of the Pt-Ni-Pt(111) and adsorbed more strongly.



Synthesis and Photocatalytic Activity of Z-Scheme Photocatalyst Sb₂WO₆/g-C₃N₄ ^†

ZHANG Jing,DONG Yuming,LIU Xiang,LI Hexing

2019, 40(1):  123-129.  doi:10.7503/cjcu20180498

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Sb₂WO₆ modified g-C₃N₄(Sb₂WO₆/g-C₃N₄) composites were synthesized by hydrothermal reaction. The properties of the Sb₂WO₆/g-C₃N₄ composites were analyzed by X-ray diffraction(XRD), scanning electron microscopy(SEM), UV-Vis diffuse reflectance spectroscopy(UV-Vis DRS) and photoluminescence(PL) spectroscopy. The results indicated that the Sb₂WO₆ grew on the surface of g-C₃N₄, forming closely contacted interfaces between the Sb₂WO₆ and g-C₃N₄ components. The photocatalytic performance of Sb₂WO₆/g-C₃N₄ composites was evaluated through the photodegradation of Rhodamine B(RhB). The results showed that 99.3% of RhB was degraded by Sb₂WO₆/g-C₃N₄ composites with 10%(mass fraction) of Sb₂WO₆ in 60 min under simulated sunlight, which was much higher than that of pure g-C₃N₄ and Sb₂WO₆. This highly enhanced photocatalytic activity of the Sb₂WO₆/g-C₃N₄ composites can be mainly attributed to strong interfacial interaction promoting the photo-generated electron-hole separation and migration. The results of radical scavenger experiments showed that ·{{\mathrm{O}}_2}^{-} and h⁺ were the dominant reactive species in the photocatalytic reaction. Besides, the Sb₂WO₆/g-C₃N₄ composites showed excellent stability over several reaction cycles. Finally, a possible Z-scheme photocatalytic mechanism was proposed based on the experimental results.



Corrosion Inhibition of Q235 Steel by Octyl Dimethyl Benzyl Quaternary Ammonium Salt Ionic Liquid^†

ZHANG Guanghua,DONG Qiuchen,ZHANG Wanbin,WANG Shuang

2019, 40(1):  130-137.  doi:10.7503/cjcu20180453

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The self-made octyl dimethyl benzyl quaternary ammonium ionic liquid(ODBA) was synthesized and its corrosion inhibitory property for Q235 steel in 1 mol/L HCl solution was studied by means of mass loss measurement, polarization curve, electrochemical impedance spectroscopy(EIS), and scanning electron microscopy(SEM) and its adsorption behavior on carbon steel surface was analyzed. The mass loss results show that the inhibition efficiencies increased with the increase of ODBA concentration. When the mass concentration was 0.2 g/L and the temperature was 30 ℃, the inhibition efficiency could reach 95.53%. ODBA is a mixed type inhibitor and preferentially inhibit the anodic reaction. The results of electrochemical test were consistent with that of mass loss test. Thermodynamic and activation energy parameters were discussed. Adsorption of ODBA was found to follow the Langmuir’s adsorption isotherm. It belongs to the mixed adsorption based on chemical adsorption. Adsorption of ODBA on steel surfaces is spontaneous and exothermic, accompanied by an increase in entropy. Thermogravimetric analysis(TGA) shows that ODBA has good thermostability.



Exploration of Increasing the Non-specificity Substrates Activity for the Phosphotriesterase-like Lactonase Using Molecular Dynamics Simulations^†

ZHU Jingxuan,YU Zhengfei,LIU Ye,ZHAN Dongling,HAN Jiarui,TIAN Xiaopian,HAN Weiwei

2019, 40(1):  138-146.  doi:10.7503/cjcu20180445

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The structural changes of phosphotriesterase-like lactonase induced by paraoxon and undecanoic-γ-lactone binding to WT SsoPox and W263F/W263T mutant were compared using molecular dynamics simulation and steered molecular dynamics simulation combined with molecular mechanics-generalized Born/surface area(MM-GB/SA) and structural interaction fingerprints(SIFt) methods. The reasons that the important residue Trp263(located in Loop 8) in SsoPox could determine the enzymatic promiscuity were listed as follow, (1) the displacements in two mutant complex could lead to a widening of the active site entrance, which allowed for tighter fitting of the substrate into the enzyme’s active site; (2) the salt bridge between Asp256 and Arg223 in the two mutant complexes occurred with a higher probability compared to two WT SsoPox complexes, which could offer a potential pathway for proton relay after catalysis. The results of comparing conformational stabilities and binding free energies between WT SsoPox and W263F/W263T mutant indicated that the complex of SsoPox and lactone was more stable and had lower binding free energy during the simulation, which was beneficial to the recognition of the substrate and nucleophilic attack of the hydroxide on the electrophilic center of the substrate. Therefore, the stable interaction of substrate with enzyme may be a reason for the natural lactonase activity of SsoPox.



Polymer Chemistry

Synthesis and Properties of Electrochromic/Electrofluorochromic Bifunctional Polymer^†

ZHOU Mingjuan, YAN Ying, CHAO Danming

2019, 40(1):  147-152.  doi:10.7503/cjcu20180415

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A novel polyamic acid bearing oligoaniline pendant was synthesized via copolymerization, followed by post-polymerization of fluorene through the amidation reaction with the assistance of DCC/DMAP. The resultant polymer was characterized in detail through ¹H NMR, FTIR and GPC. As expected, this electroactive polymer exhibits good electrochromic performance with high optical contrast value, rapid switching rate and satisfied coloration efficiency. Moreover, a novel electrofluorochromic feature is easily achieved through the introduction of fluorescent fluorene groups into the polymeric architecture. This dual electrochromic and electrofluorochromic polymer shows great potential in various intelligent applications, such as sensors, displays, and wearable devices.



Preparation and Sensing Properties of Covalent-linked Europium Complex Monodisperse Polystyrene Microspheres^†

ZHANG Chunyan,LUO Jianxin,LI Wenjun,OU Lijuan,YU Guipeng,PAN Chunyue

2019, 40(1):  153-159.  doi:10.7503/cjcu20180383

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Covalent-linked Eu-complex monodisperse polystyrene microspheres were prepared by a simple environment-friendly one-step soap-free emulsion polymerization. Styrene(St), Eu-complex monomer[Eu(AA)₃Phen] and methacrylic acid(MAA) were separately selected as matric monomer, fluorescent monomer, and water-soluble monomer. Meanwhile, Eu-complex monomer was also acted as cross-linked monomer. The chemical composition and morphology of the copolymer microspheres were characterized by ¹³C CP/MAS NMR, Fourier transform infrared spectrophotometer(FTIR), X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), transmission electron microscope(TEM), particle size analysis and zeta potential analysis. With the increase of Eu-complex content, the stability of the emulsion decreased, and the particle size and its distribution of the polystyrene microspheres increased; meanwhile, the thermal stability of the polystyrene microspheres was also decreased. Through regulating Eu-complex monomer content(0.25%—2.5%, mass fraction), the polystyrene microspheres feature a stable spherical morphology with a narrow size distribution. Excited by ultraviolet light, the polystyrene microspheres can emit the characteristic red light of europium ion. The luminescence of the polystyrene microspheres originates mainly from the sensitization of ligands to europium ions, that is, the energy transfer from ligands to europium ions. Due to the strong binding ability of Fe³⁺ to N and O atoms, the coordination structure of Eu-complex has changed after adding iron ions. As a result, the luminescence of the polystyrene microspheres can be quenched by Fe³⁺, and the common anions and other metal ions have little interference. The quenching efficiency are linearly related to the concentration of Fe³⁺ ranged from 0 to 300 μmol/L. With the increase of the content of the europium complex monomer, the fluorescence intensity of the polystyrene microspheres is enhanced, and the fluorescence detection K_SV of Fe³⁺ is increased, while limit of determent(LOD) is decreased. Regulating the content of the europium complex, the monodisperse copolymer fluorescent microspheres exhibit excellent thermal stability, strong red light emission, and high selectivity for Fe³⁺ fluorescence detection, which have high application value in biological detection and environmental protection.



Kinetic Study of the Interaction Between Lactose-containing Assembly and Protein Through Dynamic Light Scattering Technique^†

ZHANG Pan,SUN Pengfei,LIN Mingchang,GAO Zhenfei,CHEN Guosong

2019, 40(1):  160-165.  doi:10.7503/cjcu20180367

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Non-covalently connected micelles(NCCM) strategy was employed to obtain glyco-micelles covered by sugars in a convenient way. The impact factors for the recognition between carbohydrate and protein in solution were studied using dynamic light scattering(DLS) in real time. The results indicate that the agglutination ability of different lectins is of significant distinction, as measured by the formation rate of aggregates. For glyco-micelles covered by 100% lactose, the binding rates to different lectins can be recorded as SBA?LecA≈Galectin 3> ECA≈Galectin 1, which suggests that not only number of binding sites but also how they are displayed have great influence on the kinetics of the multivalent interaction. Meanwhile, Human Galectin 3, a protein of important biological function with rather mysterious binding behavior, was studied further as an application of the method.



Polydopamine-coated Gold Nanorods for Rat Submandibular Gland Radiography^†

SONG Ziqi,GONG Baijuan,WANG Lu,FENG Jing,WANG Bo,YAN Hongjing,LI Zhimin,SUN Hongchen

2019, 40(1):  166-172.  doi:10.7503/cjcu20180362

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We demonstrate the application of polydopamine-coated gold nanorods in the CT imaging of rat submandibular gland. Biocompatible polydopamine was coated on the surface of gold nanorods to lower the toxicity. CT value rises with the increase of the concentration of polydopamine-coated gold nanorods in vitro, which indicates the high sensitivity to X-ray. The polydopamine-coated gold nanorods are further applied to rat submandibular gland in vivo and radiographs are obtained. H&E staining of heart, liver, spleen, lungand kidney show no obvious inflammation for the rats.



Preparation of Modified Chitosan Antibacterial Nanospheres^†

YIN Maoli,WANG Yingfeng,REN Xuehong

2019, 40(1):  173-179.  doi:10.7503/cjcu20180351

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A novel antibacterial nanospheres was prepared by modification of chitosan with N-halamine, and characterized by nuclear magnetic resonance(NMR) and ultraviolet spectrum(UV). The effect of concentration and volume ratio of CS-HDH, polysodium tripolyphosphate(TPP) and the volume ratio of the two polymers on the formation and particle size of nanoparticles were discussed. The antibacterial properties were also measured. The results show that the nanospheres has a stable shape and uniform distribution of particle size. Excellent antibacterial properties can be obtained, and 10⁷ cfu(colong-forming units) of S. aureus and E. coli can be killed within 30 min.



Using Group Contribution Method and Molecular Dynamics to Predict the Glass Transition Temperature of Poly(p-phenylene isophthalamide)^†

WU Hongmei,LI Huiting,LI Yongcheng,WANG Hongqing,WANG Meng

2019, 40(1):  180-186.  doi:10.7503/cjcu20180344

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Aramid fibers mainly include wholly aromatic polyamide and heterocyclic aromatic polyamide, while the wholly aromatic polyamides(aramids) are considered to be high-performance organic materials due to their outstanding thermal and mechanical properties. Their high-performances arise from their aromatic structure and amide linkages. The better known commercial aramids, poly(p-phenylene terephthalamide)(PPTA) and poly(m-phenylene isophthalamide)(MPDI), are used in advanced technologies and have been transformed into high-strength and flame-retardant fibers and coatings, with applications in the aerospace and armament industry. Poly(p-phenylene isophthalamide)(PPIA), a new aromatic polyamide, has not yet been commercialized and there are few reports about its comprehensive performance until nowadays. In this paper, Group Contribution(GC) method and molecular dynamics(MD) simulation were used to simulate the glass transition temperatures(T_g) of MPDI and PPTA. Then analysis and comparisons of the glass transition temperatures by GC method and MD simulation with their experimental values are presented. The results show that the glass transition temperature measured by GC method and MD simulation is very close to the experimental value, and that the change of the density, specific volume, radius of gyration and energy along with temperature can cha-racterize the glass transition temperature. Then these two methods were exploited to simulate the T_g of PPIA. The change of the density, specific volume, radius of gyration and energy interactions along with temperature were analyzed in the MD simulation. The results show that the free volume theory can explain the glass transition phenomenon of PPIA, and the change of the non-bond energy interactions with temperature is the essential reason. These results indicates that PPIA has the potential to become another high performance polyamide with its T_g lying between those of both MPDI and PPTA. It is of great significance to emphasize on the synthesis of PPIA with sufficiently high molecular weight. In general, the group contribution method and molecular dynamics simulation can predict the T_g of aromatic polyamide sucessfully, and they can contribute to a deeper understanding on the glass transition phenomenon of aromatic polyamides and the molecular motion behind.



Thermal Stability of Polyimide Resins Containing Siloxane Structure and Their High Temperature Structural Evolution

LIU Yi, XU Xiaozhou, MO Song, ZHAI Lei, HE Minhui, FAN Lin

2019, 40(1):  187-194.  doi:10.7503/cjcu20180342

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A series of phenylethynyl-terminated imide oligomers(PEPA-PIS) based on siloxane-containing aromatic diamine, i.e., bis(p-aminophenoxy)dimethyl silane(APDS), was synthesized. The effect of siloxane content on the thermal stability of cured polyimides resins was investigated. The influence of temperature on the evolution of siloxane structure was confirmed by the non-reactive phthalic-terminated model imide oligomers(PA-PIS). The thermal stability of polyimide resins after post-curing at elevated temperature and the correlation with the microstructure and surface morphology were discussed. The results indicated that the oxidative crosslinking reaction of siloxane was occurred at elevated temperature, and even resulting in the formation of inorganic silica on the resin surface. The significant enhancement in thermal stability of polyimide containing siloxane structure is attributed to their organic/inorganic hybrid characteristics.



Simulation on the Dynamic Process of Formation of Particle Cluster by Generalized Exponential Model^†

MA Lan,RONG Jingjing,ZHU Youliang,HUANG Yineng,SUN Zhaoyan

2019, 40(1):  195-200.  doi:10.7503/cjcu20180323

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The generalized exponential model was used to describe the interaction between soft colloidal particles. The dynamic process of structure formation and transformation was investigated by molecular dynamics simulations. The characteristics of the structural transformation and the influence of thermodynamicpath on the final formed structure of cluster crystal were studied for two thermodynamic paths, isothermal compression and equidensity cooling, respectively. Compared with Monte Carlo simulation results, the structure transitionin molecular dynamics simulation has obvious hysteresis on changing density, which is due to a high free energy barrier between fcc2 and fcc3 structures. In addition, the phase structure under the same temperature and pressure is not exactly same through different thermodynamic paths.It is concluded that the dynamic formation process has a great influence on phase structure.