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Nano Research 2015年第2期8卷 502-511页

作者： Yexin Zhang Chunlin Chen Lixia Peng Zhongsen Ma Yajie Zhang Hengheng Xia Aili Yang Lei Wang Dang Sheng Su Jian Zhang Ningbo Institute of Materials Technology & Engineering Chinese Academy of Sciences Ningbo 315201 China Science and Technology on Surface Physics and Chemistry Laboratory Mianyang 621907 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Ozone treatment is a common way to functionalize commercial multi-walled carbon nanotubes （CNTs） with various oxygen functionalities like carboxyl, phenol and lactone groups, in order to enhance their textural properties and chemical activity. In order to detail the effect of each functional group, we correlated the activity with the surface density of each group, and found that the carboxyl groups play a pivotal role in two important catalytic reactions, namely the electrochemical oxygen reduction reaction （ORR） and agar conversion to 5-hydroxymethylfurfural （HMF）. During the processes, the hydrophilic surface provides a strong affinity for reaction substrates while the improved porosity allows the efficient diffusion of reactants and products. Furthermore, the activity of functionalized CNTs for agar conversion remained almost unchanged during nine cycles of reaction. This work highlights a strategy for improving the activity of CNTs for electrochemical ORR and agar conversion reactions, as well a promising application of carboxyl-rich CNTs as a solid acid catalyst to produce high-purity HMF--an important chemical intermediate.

关键词： carbon nanotubes functionalization carboxyl group oxygen reduction reaction biomass conversion

Highly Hydrolysis-Resistant Polyimide Fibers Prepared by Thermal Crosslinking with Inherent carboxyl groups

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Chinese Journal of Polymer Science 2024年第2期42卷 247-255,I0010页

作者： Can-Can Zhang Jun-Long Yang Ya-Jiang Huang Guang-Xian Li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials Engineering of ChinaSichuan UniversityChengdu610065China

Easy hydrolysis in alkaline environments limits the use of polyimide fibers in environmental protection. The hydrolysis resistance levels of polyimide fibers can be improved by crosslinking of the macromolecular chains. In this work, crosslinked polyimide fibers(CPI fibers) were produced by intrinsic carboxyl decarboxylation for the first time. The thermal stability of the polyimide fibers containing the intrinsic carboxyl groups(PIC fibers) was studied, and the temperature of the decarboxylation-crosslinking reaction was determined to be 450 ℃. The PIC fibers were hotdrawn to initiate thermal crosslinking of the carboxyl groups and molecular chain orientation at high temperature. The CPI fibers had high tensile strengths(0.72-1.46 GPa) and compressive strengths(401-604 MPa). The oriented macromolecules and chemically crosslinked structure improved the tightness of the molecular chains and endowed the CPI fibers with excellent hydrolytic resistance. The CPI-50 fiber did not dissolve in a 0.5 wt% NaOH solution during heating at 90 ℃ for 10 h, and the tensile strength retention reached 87% when treated in 0.5 wt% NaOH solutions at 90 ℃ for 1 h, providing a guarantee for its application in alkaline corrosive environments.

关键词： Polyimide carboxyl group Crosslinking Hydrolysis-resistance

Effect of Exogenous carboxyl and Hydroxyl groups on Pyrolysis Reaction of High Molecular Weight Poly(L-Lactide)under the Catalysis of Tin

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Chinese Journal of Polymer Science 2021年第8期39卷 966-974,I0005页

作者： Li-Dong Feng Xin-Chao Bian Gao Li Xue-Si Chen Key Laboratory of Polymer Ecomaterials Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Jilin Biomedical Polymers Engineering Laboratory Changchun 130022China

The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was estimated by the Kissinger-Akahira-Sunose *** kinetic models were also explored by the Malek method,and the random degradation behavior was determined by comparing the plots of ln{-ln[1-(1-w)05]}versus 1/7for experimental data from TGA with model *** pyrolysis reaction rate of PLLA was affected slightly by exogenous hydroxyl and carboxyl groups at lower levels of Sn with 65-70 mg·kg^(-1)but increased appreciably in the presence of extraneous Sn^(2+),-COOH/Sn^(2+),or-OH/Sn^(2+).The Ea values for the pyrolysis reactions of the PLLAs that provided lactide were different under the catalysis of Sn2+in different chemical environments because Sn^(2+) can form the new Sn-carboxylate and Sn-alkoxide with exogenous carboxyl and hydroxyl groups,which were different in steric hindrance for the formation of activated complex between Sn^(2+) and *** the catalysis of Sn^(2+),a lactide molecule can be directly eliminated selectively at a random position of PLLA molecular chains,and the molecular chain of PLLA cannot change two PLLA fragments at the elimination site of ***,it was regenerated into a new PLLA molecule with the molecular weight reduced by 144 g·mol^(-1).

关键词： Poly(L-lactide) Pyrolysis mechanism carboxyl group Hydroxyl group Tin

Insights into the effect of substrate adsorption behavior over hemelike Fe_(1)/AC single-atom catalyst

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Nano Research 2022年第7期15卷 5970-5976页

作者： Jianglin Duan Yanan Zhou Yujing Ren Dan Feng Jinlong Shang Huibin Ge Jie Gao Jinlong Yang Yong Qin Interdisciplinary Research Center of Biology&Catalysis School of Life SciencesNorthwestern Polytechnical UniversityXi’an 710072China Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026China Analytical&Testing Center Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Coal Conversion Institute of Coal ChemistryChinese Academy of SciencesTaiyuan 030001China

Unraveling the substrate adsorption structure–performance relationship is pivotal for heterogeneous carbon supported metal single-atom catalysts(M_(1)/C SACs).However,due to the complexity of the functional groups on carbon material surface,it is still a great ***,inspired by structure of enzymes,we used activated carbon(AC),which has adjustable surface oxygen functional groups(OFGs),supported atomically dispersed Fe-N_(4) sites as heme-like *** based on a combination of scanning transmission electron microscopy(STEM),X-ray photoelectron spectroscopy(XPS),X-ray absorption spectroscopy(XAS),Mössbauer spectroscopy,Fourier transform infrared(FT-IR)characterizations,kinetics experiments and density functional theory(DFT)calculations,we revealed the effect of substrate adsorption behavior on AC support surface,that is,with the increase of carboxyl group in OFGs,the adsorbed 3,3',5,5'-tetramethylbenzidine(TMB)molecular increased,and consequently the substrate enriched on AC *** carboxyl group as well as Fe-N_(4) active sites synergistically realized high-efficiency peroxidase-like activity,just like the *** work suggests that simultaneously constructing metal single-atom active sites and specific functional groups on carbon support surface may open an avenue for engineering metal-support synergistic catalysis in M_(1)/C SACs,which can further improve catalytic performance.

关键词： single-atom catalysts heme-like carboxyl group substrate adsorption behavior peroxidase-like activity

Continuous Surface Metallization of Polyimide Fibers for Textile‑Substrate Electromagnetic Shielding Applications

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Advanced Fiber Materials 2023年第6期5卷 1892-1904页

作者： Shixu Zhou Jie Dong Xiuting Li Xin Zhao Qinghua Zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua University201620 ShanghaiPeople’s Republic of China

Despite tremendous effort,continuous fabrication of high-performance conductive polymer fibers for electromagnetic interference(EMI)shielding applications remains a daunting technical *** the current study,we report an efficient strategy for continuous surface metallization of polyimide fibers used in textile-substrate electromagnetic shielding *** fibers with pendent carboxyl groups(PIC)were first fabricated,and a conductive nickel layer was continuously coated on the PIC surface by electroless metal deposition(ELD).The carboxyl groups introduced onto the fiber surface acted as binding sites for the Ni^(2+)ions,and the complexation reactions greatly increased the Ni^(2+)adsorption capacity and efficiency of the PIC fibers during the ELD process and ensured continuous *** judicious control of the plating time,a series of nickel-layer-coated PIC fibers(Ni-PIC)were constructed with Ni loadings ranging from 20 to 230 wt%.The resultant Ni-PIC fiber containing 65 wt%Ni exhibited conductivity of 223 S cm^(−1),and the corresponding fabric exhibited an EMI shielding effectiveness(EMI SE)of 44 dB in the *** corresponding EMI SE was further improved to 83 dB after the fiber was treated at 300℃ for 1 h because of the crystallization of the Ni *** prepared Ni-PIC fibers and fabrics were also used in pressure sensors and electrothermal conversion,which demonstrated outstanding adaptabilities to various temperatures and mechanical ***,this work provides an efficient route for developing high-performance conductive polyimide fibers for EMI shielding applications,especially for use in military and aerospace equipment and in other harsh environments.

关键词： Polyimide carboxyl group Nickel layer Electroless metal deposition EMI shielding

Chemical Modification of Amino Acid Residues in Human Plasminogen

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Chemical Research in Chinese Universities 2003年第3期19卷 317-319页

作者： LIANGFang SUNHong ZHAOCheng-guang CUITing HONGShui-sheng CHENJia LIULan-ying CollegeofLifeScience JilinUniversityChangchun130023P.R.China ChangchunInstituteofBiologicalProducts Changchun130062P.R.China

The chemical modification of human plasminogen(HPg) was studied with 1-ethyl-3-(3- dimethyl aminopropyl) carbodiimide(EDC), N -acetylimidazole(NAI), 1,2-cyclohexanedione(CHD), chloramine T(Ch-T) and N -bromosuccinimide(NBS) as modifying reagents at its carboxyl group, tyrosine, arginine, methionine and tryptophan residues, respectively. The results indicate that tyrosine and arginine residues are not essential for HPg activity, while carboxyl groups, methionine and tryptophan residues are important for the activity of HPg. The Keech and Farrant′s kinetic analysis reveals that one tryptophan residue, one methionine residue and two carboxyl groups are essential for HPg activity.

关键词： Human plasminogen(HPg) Chemical modification carboxyl group Methionine Tryptophan

羧基和咪唑基团在柚柠檬苦素类化合物糖基转移酶催化反应中的作用(英文)

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催化学报 2010年第12期31卷 1445-1451页

作者： M.R.KARIM F.HASHINAGA Department of Biochemical Science and Technology Faculty of AgricultureKagoshima University

Limonoid bitterness is a serious problem in the citrus industry worldwide. Limonoid glucosyltransferase is an enzyme that catalyzes the conversion of bitter limonoid into non-bitter limonoid glucoside while retaining the health benefit of limonoids in the juice. The immobilization of this enzyme in a column can solve the juice bitterness problem. More information about the catalytic residues of the enzyme is needed in this immobilization process. Glutamate/aspartate,histidine,lysine,tryptophan,serine,and cysteine residues were chemi-cally modified to investigate their roles in the catalytic function of limonoid glucosyltransferase. Inactivation of the enzyme following modi-fication of carboxyl and imidazole moieties was a consequence of a loss in substrate binding and catalysis in the glucosyltransfer reaction. The modification of a single histidine residue completely destroyed the ability of limonoid glucosyltransferase to transfer the D-glucopyranosyl unit. Tryptophan seemed to have some role in maintaining the active conformation of the catalytic site. Lysine also seemed to have some direct or indirect role in this catalysis but the modification of serine and cysteine did not have any effect on catalysis. Therefore,we conclude that the carboxyl and imidazole groups containing amino acids are responsible for the catalytic action of the enzyme.

关键词： chemical modification catalytic residue carboxyl group imidazole group uridine diphosphate glucosyltransferase pummelo albedo

Computational simulations integrating inhibition kinetics of tyrosinase by oxalic acid

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Computational simulations integrating inhibition kinetics of...