Acta Chimica Sinica-Forthcoming Articles

Electrochemical detection of xanthine and study for the inhibition of uric acid based on chitosan/nitrogen doped reduced graphene oxide modified electrode

Song Guangjie, Wu Tiaodi, Liu Fuxin, Zhang Binyan, Liu Xiuhui — 2019-11-07 00:00:00.0

Nitrogen doped reduced graphene oxide (N-RGO) was successfully prepared by carbon thermal reduction method, which annealed graphene oxide (GO) and cyanamide at 900℃. The 0.2% acetic acid solution with chitosan (CS) was used as the dispersant of N-RGO to improve the dispersivity, electronic mass transfer rate, and biocompatibility of N-RGO. The morphology, structure and electrochemical properties of N-RGO and CS/N-RGO were investigated by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), and cyclic voltammetry (CV). FT-IR spectrum indicated graphene oxide (GO) was reduced and N-RGO was successfully prepared. The electrochemical experiments demonstrated that CS/N-RGO possesses large electrochemical effective area, strong adsorptive ability and fast electronic mass transfer rate. Then a novel electrochemical sensor for detection of xanthine was fabricated based on CS/N-RGO modified glassy carbon electrode (CS/N-RGO/GCE). It exhibited good electrochemical response toward the oxidation of xanthine with a linear range covering 2.99×10^-8~1.07×10^-4 M, and the corresponding detection limit (LOD) of 9.96×10^-9 M (S/N=3). In addition, the electrochemical behaviors of xanthine on CS/N-RGO/GCE was explored using cyclic voltammetry (CV), which included the pH effect on the oxidation of xanthine and the effect of scan rate on the peak current and peak potential of xanthine. Usually, uric acid in the body is generated by xanthine under the catalysis of xanthine oxidase (XOR), and high concentration of uric acid can cause gout. The inhibition for the formation of uric acid is the most direct method for the treatment of gout. Hence, the inhibition for the formation of uric acid by febuxoatat and allopurinol was researched by electrochemical method, manifesting febuxoatat and allopurinol can inhibit the activity of xanthine oxidase, which did not make xanthine generating uric acid. Thus, this work is very meaningful in the field of the diagnosis and treatment of gout.

Cyclic Lanthanide-based Molecular Clusters: Assembly and Single Molecule Magnet Behavior

Haiquan Tian, Li-Min Zheng — 2019-11-06 00:00:00.0

Lanthanide-based single molecular magnets have received tremendous attentions in recent years owing to the strong magnetic anisotropies of the lanthanide ions arising from the strong spin-orbital couplings. Cyclic metal clusters, also called molecular wheels or metallacrown ether, are a subclass of metal clusters. From the magnetic point of view, cyclic transition metal clusters can be devided into three types, e.g. ferromagnetically coupled cyclic clusters which favor single molecule magnet behavior, and antiferromagnetically coupled even-or odd-numbered cyclic clusters with S=0 or S=1/2 ground state. The magnetic properties of lanthanide-based cyclic clusters are more complicated because the magnetic interactions between the lanthanide ions are extremely weak. The overall magnetic behavior is largely dominated by the single ion anisotropy and the dipole-dipole interactions between the metal ions. When the anisotropy axes of the lanthanide ions in the cyclic clusters are arranged in a toroidal manner, single-molecule toroics could be achieved. Therefore, the design and synthesis of cyclic lanthanide-based clusters can provide not only new materials with architectural beauty and single molecule magnet behavior, but also single-molecule toroics with vortex distribution of the magnetic dipoles of lanthanide ions, which would have potential applications in information storage, quantum computing, spintronic devices and multiferroic materials. Noting that lanthanide-based single-molecule toroics has been described detailly in several reviews, this article will summarize the current status of the cyclic lanthanide clusters with the focus on the design and assembly strategies, the structural characteristics and magnetic studies. Most work have been concentrated on the Ln₃, Ln₄ and Ln₆ cyclic clusters, including those containing oxygen centers. Examples of even-numbered cyclic clusters Ln_x (x ≥ 8) are much less, and those of odd-numbered cyclic clusters Ln_x (x ≥ 5) are rare. As the cyclic clusters are frequently distorted to different extent, many of them exhibit single molecule magnet behavior, and only few of them show toroic magnetization. It remains future challenges to design and synthesize new lanthanide-based cyclic clusters with regular and flat geometries and toroically arranged magnetic moments, and to achieve the multifunctions in the same molecular composite.

New Polymerizations Based on Green Monomer of Carbon Dioxide

Bo Song, Anjun Qin, Ben Zhong Tang — 2019-10-31 00:00:00.0

Carbon dioxide (CO₂) is an abundant, inexpensive, non-toxic and renewable C1 resource, and it is also a kind of green monomer. The polymerizations based on CO₂ have been one of the hot research topics. The copolymerization of CO₂ and epoxide monomers was widely studied in the past few years and has been industrialized. Some new polymerizations based on CO₂ have also been reported recently. There are two ways to produce polymeric materials from CO₂. One is converting CO₂ into monomers for further ring opening or step growth polymerizations, such as lactone, cyclic carbonates, furan-2,5-dicarboxylic acid. Another is directly using CO₂ as a monomer for the copolymerization with other monomers to generate polymers. They are both significant for developing new polymerizations based on CO₂ and expanding CO₂-based polymeric materials. This review summarizes the advances in converting CO₂ into polymeric materials during the past few years, and discusses the perspective in this area.

Two Polymorphs of Triphenylamine-substituted Benzo[d]imidazole:Mechanoluminescence with Different Colors and Mechanofluorochromism with Emission Shifts in Opposite Direction

Liu Xiaojing, Jia Yanrong, Jiang Hao, Gao Guanlei, Xia Min — 2019-10-22 00:00:00.0

Mechanofluorochromism (MFC) and mechanoluminescence (ML) are two types of significant solid-state optical phenomena which are closely dependent on conformations, packing modes and intermolecular interactions. Herein, through a three-step route involving aromatic nucleophilic substitution, reduction and oxidative cyclization in DMSO under air, a benzo[d]imidazole with triphenylamine and 4-cyanophenyl respectively located at C₁-and N₁-position is obtained in good yields. Two polymorphs of this fluorophore TBIM_B and TBIM_G correspondingly exhibit intense deep-blue (435 nm) and green fluorescence (505 nm). Under force stimuli, both polymorphs turn into amorphous phase with cyan fluorescence (457 nm). By fuming in solvent vapor or annealing treatment, only the ground TBIM_B sample can be completely restored into the original crystalline structure, the ground TBIM_G sample is just transformed into TBIM_B crystal. It is assumed that the enhanced energy barrier induced by the denser packing in TBIM_G crystal makes the conversion from in amorphous phase to crystalline one kinetically infeasible. The crystallography reveals that triphenylamine moiety in TBIM_G crystal is less restrained by intermolecular interactions than that in TBIM_B crystal, which results in the long-wavelength TICT emission in the former crystal and the short-wavelength LE emission in the latter one. In exposure to force stimuli, TBIM_B and TBIM_G crystals respectively give out the blue (432 nm) and green (500 nm) flash. It is revealed by crystallography that both polymorphs hold centrosymmetric space groups. DFT calculations based on the molecular couples with strong intermolecular interactions demonstrate that the close-to-zero net dipole moments occurs on these couples. Hence, neither piezoelectric effect nor excitation of molecules on cracked surfaces by discharges between molecular couples should account for the ML behaviors of these two polymorphs. Due to the readily force-induced cleavage of the two crystals by particular chain-shaped packing, the endogenous friction discharge caused by relative movements between cleavage planes would excite molecules on these planes, and this mechanism is assumed to be mainly responsible for the ML activity of the two crystals.

Self-Assembly of Cyclic Dipeptides and Their Fluorescent Properties

Yang Jingge, Li Yang, Wang Xiaoai, Wang Dong, Sun Yawei, Wang Jiqian, Xu Hai — 2019-10-21 00:00:00.0

Cyclic dipeptide (CDP) is a kind of the smallest cyclic peptide with two amino acids cyclization through amide bonds. The two amide bonds with four hydrogen bonding sites give CDPs a high self-assembly propensity, mainly driven by the hydrogen bonding interactions. In this paper, we have designed four CDPs, c-SF, c-SY, c-SH, and c-DF, and studied their self-assembly performance in aqueous solution with circular dichroism spectroscopy (CD) and atomic force microscopy (AFM), including the effects of pH and zinc ion coordination on self-assembly. The fluorescence properties of CDP self-assemblies have also been studied. CD results showed that c-SF, c-SY and c-DF adopted a β-sheet conformation, while c-SH was random coil secondary structure at the concentration of 2.0 mM and pH 5.0. AFM results showed that c-SF, c-SY and c-DF could form nanofibers with different diameters ranged from 1.0 to 3.0nm. In addition, c-SY self-assembled hierarchically over time. Not only the nanofiber diameter gradually increased, but also the nanofibers entangled into 3D networks. Although c-SH did not self-assemble at the concentration of 3.0 mM and pH 7.0, it could form monolayers with the induction of zinc ion at pH 9.0. The self-assemblies of each CDP had different multiple fluorescent emission peaks with excitation of different wavelengths. Especially, c-SF emitted green fluorescent light under UV light of 365 nm. The fluorescent emission intensity of CDPs was much stronger than their corresponding linear dipeptides. It was assumed that the diketopiperazine structure contributed to the fluorescence enhancement. Moreover, the fluorescent emission intensity of CDP self-assemblies was much higher than that of their free molecules, which meant that the ordered aggregation made a significant contribution to the fluorescent properties. Both the coordination of zinc ions with the imidazole groups on histidine and the oxidation of phenolic hydroxyl groups in tyrosine could enhance the fluorescent emission intensity of CDPs. It was assumed that CDP molecules stacked one by one to form nanofibers during self-assembly. The diketopiperazine ring of CDPs and its self-assembly endowed CDPs with special fluorescent properties.

A new method for enriching baicalin in Scutellaria baicalensis Georgi by metal organic framework material ZIF-8

Guo Wenjuan, Yu Jie, Dai Zhao, Hou Weizhao — 2019-10-21 00:00:00.0

This paper aims to explore a new method for the efficient enrichment of baicalin in Scutellaria baicalensis Georgi by using MOFs materials, and to open up new applications for MOFs in the adsorption direction. The Zeolitic Imidazolate Framework-8(ZIF-8) was synthesized by solvothermal method and characterized by structure to ensure its accurate synthesis. Baicalin was extracted from Scutellaria baicalinsis Georgi by ethanol extraction and acid precipitation method. The ZIF-8 was used to carry out the static adsorption experiment on the crude extract of Radix Scutellariae. After the adsorption equilibrium was reached, the mixture was centrifuged, and the residual concentration of baicalin was detected by High Performance Liquid Chromatography method(HPLC). The recovered saturated adsorbed ZIF-8 material was washed with water and dried, and the PBS solution of pH 6.8 was used as a desorption solution, and the desorption was performed by shaking. The content of baicalin in the desorbed solution was determined by HPLC to calculate the desorption rate and achieve the purpose of adsorbent recovery. In the adsorbing process, the effects of adsorbent dosage, pH and adsorbate concentration of the crude extract of Radix Scutellariae were also optimized, and the response surface test (RSM) was performed using Design Expert software to obtain optimal adsorption conditions. Under these conditions, the adsorption rate of ZIF-8 to baicalin in Radix Scutellariae was as high as 98.22%, and the adsorption effect was not significant on other components in Radix Scutellariae. The desorption rate of ZIF-8 adsorbed baicalin in pH 6.8 solution was 62.46%, and the purity of baicalin increased from 21.55% before adsorption to 64.27% after desorption, and ZIF-8 had good stability before and after adsorption, and the recovery rate reached 83.50%. Therefore, ZIF-8 has potential application value in the adsorption and purification of baicalin. The adsorption law and mechanism of ZIF-8 on baicalin were studied:The adsorption of baicalin on ZIF-8 accorded with the quasi-second-order kinetic equation, and the equilibrium adsorption data accorded with the Langmuir adsorption isotherm model.

Recent Progress of Photocatalysis Based on Metal Halide Perovskites

Li Xin, Zhang Taiyang, Wang Tian, Zhao Yixin — 2019-10-21 00:00:00.0

Solar-driven photocatalytic pollutant degradation and the synthesis of chemical fuels or other high value-added products via photocatalysis have drawn plenty of attentions in green chemistry and renewable energy research. In recent years, metal-halide perovskites with superior photoelectric properties are successfully utilized into high-efficiency photocatalytic reactions in addition to conventional metal oxide semiconductor materials. In this paper, we reviewed the recent advances of metal-halide perovskite based photocatalyst, especially lead-halide perovskites in photocatalytic hydrogen production, photocatalytic degradation and CO₂ reduction. The reaction mechanisms and key challenges for metal halide perovskites photocatalyst are discussed and we prospect the further development of highly efficient and stable metal halide perovskite photocatalysis in the future.

Zn/Ni Bimetallic Relay Catalysis: One Pot Intramolecular Cycloisomerization/Intermolecular Amidoalkylation Reaction toward Oxazole Derivatives

2019-10-16 00:00:00.0

Oxazole derivatives are widely found in natural products and pharmaceuticals with impressive biological properties, tremendous efffforts have been devoted to the development of new methodologies and strategies to construct the oxazole rings, However, most of these reactions require harsh reaction conditions, limiting the wide application of these classical oxazole synthetic methods in organic synthesis. N-acyliminium ions represent important electron defificient carbocations intermediates in organic synthesis because they provide various biologically important natural and unnatural products via C-C and C-heteoatom bondforming methodologies using an inter-or intramolecular path.of amides or lactams usually generates N-acyliminium ions, which act as more electron-defificient carbocations toward nucleophiles. In this paper, a novel tandem metal relay catalytic system of Zn/Ni has been successfully developed. By using this unprecedented Zn(OTf)₂/Ni(ClO₄)₂·6H₂O bimetallic relay catalytic system, a variety of oxazole derivatives were obtained from easily available N-(propargyl)-arylamides and various γ-hydroxy lactams through intramolecular cycloisomerization/intermolecular amidoalkylation under mild conditions. The first step of the one-pot procedure is that Zn(OTf)₂ acts as a π acid to activate the triple bond of N-(propargyl)-arylamides, and a subsequent intramolecular 5-exo-dig cyclization forms the oxazoline intermediate. Separately, Ni(ClO₄)₂·6H₂O acts as Lewis acid to activate and facilitate the departure of 3-hydroxyl group to form the electrophilic acyliminium ions, which then in an intermolecular reaction is transformed to the oxazole derivatives in good to excellent yield. Control experiments in the optimization section disclose the fact that Zn(OTf)₂ and Ni(ClO₄)₂·6H₂O are both indispensable for this intramolecular cycloisomerization/intermolecular amidoalkylation Reaction. Generally, the synthetic reactions run under air atmosphere by heating all the substrates and reagents in one-pot at 100 oC. The N-(propargyl)-arylamide containing different types of electron-donating substituents, different electron-rich aromatic rings and different electron-withdrawing substituents can be reacted with 3-hydroxy-2-benzyl-isoindolin-1-one to give the corresponding oxazole derivatives. In contrast, the propargyl amide containing an electron withdrawing group has a lower yield than the one using other propargyl amide, because the activity of the oxazoline intermediate obtained by the propargyl amide containing an electron withdrawing group is lower. 3-hydroxy-2-phenylisoindoline-1-one, 3-hydroxy-2-phenylmethylisoindoline-1-one and 3-hydroxy-2-phenylethyl isoindolin-1-one have also been found applicable to this reaction. The present method benefits from the distinctive features of simple reaction conditions, high atom economy and broad substrate tolerance. It is of great significance for the synthesis of oxazole derivatives and the formation of acyliminium ions.

Glycan Analysis in Cellular Secretion

Xiong Yingying, Chen Yunlong, Ju Huangxian — 2019-10-09 00:00:00.0

Glycans are important components of mammalian cells, which exists extensively in eukaryocytes. Glycans are mainly consisted of monosaccharides, oligosaccharides and polysaccharides. They are connected to proteins or lipids through glycosylation, which constitute glycoconjugates. Glycosylation is one of the most important post-modifications of proteins, which mediate a wide variety of biological processes, including cell growth and differentiation, cell-cell communication, immune response, pathogen interaction, and intracellular signaling events. Because of the complex marshalling sequences, diversiform connection types and multiple branch structures, glycans are endowed with various structures. The diversity of glycan structure brings glycoconjugates with abundant information of cellular function. Among all the factors, human diseases act as an important ingredient which can induce unnatural glycosylation process. Glycoconjugates have been chosen as an efficient biomarker in the area of disease surveillance and targeted drug therapy. Thus, analysis of secreted glycans is of great importance for monitoring the states of cells or diseases in clinical diagnosis and treatment. Based on recent research of extracellular glycans, this review introduces the types of glycans in cellular secretion and their biological functions or significances, summarizes the identification or detection techniques of the secreted glycans, including lectin identifications, chemical covalent identifications and glycan metabolic marker techniques. Detection technologies of cell secretory glycan have been emphatically introduced in this review, which mainly contain spectrophotometry techniques, chromatography techniques, mass-spectrography techniques, fluorescence methods, electrochemical processes, enzyme linked immunosorbent assay techniques and western blot methods. After summarizing the progresses in this field during the past few decades, we outlook the future development of the analysis of cell secretory glycans. As far as we concern, in situ identification and quantitative detection will be the most challenging but meaningful topic of this field. We hope this review can be provided as a useful guidance for the investigating of glycosylation or glycan-related biological processes.

Visualization of The Electrolyte Migration under Electrode Conditioning by ToF-SIMS

Hai-Lun Xia, Xin Hua, Yi-Tao Long — 2019-10-09 00:00:00.0

The essence of electrochemical reaction was the electron transfer process on the electrode while the premise for electrochemical reaction happening was the migration and diffusion of electro-active species. Interpreting the monitoring process of electrode towards the electro-active species during the electrochemical reaction would really do favor to the further understanding of the electrochemical evolution process at the electrode-electrolyte interface. In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was adopted for the in-situ monitoring of the electrode-electrolyte interface during the electrochemical reaction with the cooperation of a microfluidic electrochemical cell which was constructed for the liquid sample analysis under the high vacuum environment. With the application of the primary ion beam on the silicon nitride membrane of the microfluidic cell, a micro-hole with the diameter of 2 μm would be fabricated for the direct monitoring of the electrode-electrolyte interface. The migration of KCl aqueous solution on the electrode-electrolyte interface under the monitoring of gold electrode was investigated by ToF-SIMS here. The direct observation of K⁺(H₂O)_n and H⁺(H₂O)_n in the electrolyte provided information of the electrode-electrolyte interface at molecular level. Besides, the chemical distributions of K⁺ and H⁺(H₂O)_n under different potential were also studied to verify the feasibility of ToF-SIMS in visualizing electrochemical evolution process on the electrode-electrolyte interface. The chemical distributions of K⁺ and H⁺(H₂O)_n obtained by ToF-SIMS showed that K⁺ would enrich to the gold electrode when the negative potential was applied but diffuse to the bulk solution when positive potential was applied. For H⁺(H₂O)_n, they would be repulsed away from the electrode when the positive potential was applied and enrich to the surface of electrode when the negative potential was applied. The potential-dependent behaviors of K⁺ and H⁺(H₂O)_n indicated that visualization of the migration process of electrolyte on the electrode-electrolyte interface was realized, which may help the further study of the evolution at electrode-electrolyte interface during the electrochemical reaction, providing new insight into the revealment of the mechanism of electrochemical reaction.

Recent Advances on Surface Modification of Li- and Mn-Rich Cathode Materials

Li Zhao, Wang Zhong, Ban Liqin, Wang Jiantao, Lu Shigang — 2019-10-09 00:00:00.0

With the rapid development of electric car and energy storage power station, there is an increasing demand for lithium ion batteries of high energy density. Li- and Mn-rich (LMR) cathode materials with large specific capacity (>250 mAh·g^-1) are supposed to accomplish lithium ion batteries with high energy density (>350 Wh·kg^-1). The high capacity performance of LMR cathode materials are resulted from the lattice oxygen redox reaction induced by the electrochemical activation of the Li₂MnO₃ phase. However, the activation of the Li₂MnO₃ phase and oxygen redox reaction lead to lattice oxygen release and structure transformation, which cause some serious problems such as low initial columbic efficiency, poor rate capability, voltage and capacity degradation after subsequent cycles. The oxygen release and structure transformation always start from the surface, indicating that the surface stability is significant to LMR cathode materials. In this paper, surface modifications such as surface coating, surface doping and surface chemical treatment are reviewed and the mechanism of three surface modification methods for LMR cathode materials are discussed in further. Surface coating is one of the most widely surface modification methods, which can suppress the electrode/electrolyte side reaction and reduce the transition metal dissolution. The effect of surface coating is always determined by the characteristic of coating layer materials including non-active coating layer, electrochemical active coating layer, Li⁺ conductive coating layer and electronic conductive coating layer. Surface doping has shown to be an effective method in suppressing oxygen loss and structural transformation. Surface chemical treatment has resulted in reducing irreversible capacity loss by activating Li₂MnO₃ phase. On this basis, surface integrated strategies combined several surface modified methods are introduced and discussed in recent years. The surface intergrated strategies not only enhance the structural stability and suppress electrode/electrolyte surface-interface reaction, but also have an effective role on mitigating structure transformation and lattice oxygen release. Finally, we wish that our review would provide research directions for surface modified strategies of LMR cathode materials in future.

Preparation of Eu-doped ZnO/MIL-53 (Fe) Photocatalyst and its Catalytic Performance for Selective Oxidation of Alcohols

Meng Shuangyan, Wang Mingming, Lv Bolin, Xue Qunji, Yang Zhiwang — 2019-09-26 00:00:00.0

The novel 3 dimension (3D) nanocomposite photocatalyst Eu-ZnO/MIL-53(Fe) was successfully prepared with in situ synthesis. The synthesis was that the rare earth element Eu was doped into semiconductor ZnO and then Eu-ZnO was combined with MIL-53(Fe). The structure, morphology, optical and electrical properties of the nanocomposites had been thoroughly characterized by X-ray diffraction (XRD), Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption isotherms (S_BET), photoluminescence spectra (PL) and electrochemical impedance (EIS) spectra and the like. The FT-IR and XRD results showed that the photocatalysts were successfully prepared and SEM results showed that morphology of the MIL-53(Fe) were all well remained after the preparing process. The photocatalytic experiment data, UV-vis DRS spectra and PL spectra and the like results showed that the introduction of rare earth elements Eu could greatly improve the photocatalytic efficiency of MIL-53 (Fe), and promote the effective separation of photogenerated electron-hole, which further improved the catalytic activity, the results of electrochemical impedance spectra further supported the conclusion. By exploring the photocatalytic activity of Eu-ZnO/MIL-53(Fe) under visible light conditions, the photocatalyst had showed excellent photocatalytic activity. Some derivatives of benzalcohol were more affected by electronic effects, the conversion of the derivative having an electron-withdrawing group was relatively high, and the conversion of the derivative having an electron-donating group was low. The possible mechanism of the photocatalytic reaction was explored via the active species capture experiment and Mott-schottky (M-S) curve test. The results showed that the photocatalytic selective oxidation of alcohols achieved with photogenerated holes (h⁺) and hydroxyl radicals (·OH). The photo stability and thermal stability of the photocatalyst was investigated by cyclic experiments and the structure characterization of the photocatalyst before and after the photoreaction showed that the photocatalyst had outstanding light stability and thermal stability.

Study on the Migration and Transformation Mechanism of Graphene Oxide in Aqueous Solutions

Lei Shi, Hongwei Pang, Xiangxue Wang, Pan Zhang, Shujun Yu — 2019-09-24 00:00:00.0

Graphene oxide (GO) is widely used in energy chemical, environmental restoration, nanomaterials, liquid phase catalysis, etc. due to its excellent physical and chemical properties. At the same time, GO is inevitably discharged into nature during the application process, and the toxicity released into the environment may lead to instability of the biological system. Therefore, this paper systematically studied several common cations (Na⁺, K⁺, Ca²⁺, Mg²⁺), anions (PO₄^3-, SO₄^2-, CO₃^2-, HCO₃^-, Cl^-) and clay minerals (montmorillonite, kaolin, bentonite, nano-alumina) on GO coagulation at different concentrations. And FTIR is used to characterize the clay minerals before and after the precipitation of GO. The experimental results show that the cations have strong GO coagulation ability, and the coagulation ability of different valence cations has a large difference. After analysis, the electrical properties of GO in aqueous solution are negative, the cation acts as a counter ion, and the coagulation behavior conforms to the Schulze-Hardy rule. The main reason for the difference in coagulation ability between isovalent cations is electronegativity and ionic hydration. The anion acts to increase the stability of GO, and the coagulation ability of the cation is more effective than the stabilization ability of the anion. The ability of sodium salts with the same valence anion to segregate GO also differs, mainly because the hydrolysis of HCO₃^- and CO₃^2- causes a decrease in the negative charges, resulting in a decrease in the ability to stabilize GO. The clay minerals contain hydroxyl and metal-oxygen bonds that interact with GO. According to the maximum removal rate, the clay minerals have the coagulation ability: nano-alumina > kaolin > bentonite > montmorillonite. The main influencing factors are the electrical properties of clay minerals in aqueous solution. This paper is helpful to understand the coagulation behavior of GO in different water environments, and it is of great significance for the future application of graphene engineering in pollution control.

Review of theoretical and applied research of graphene in anti-corrosion film and organic anti-corrosion coatings

2019-09-24 00:00:00.0

This paper summarized and collated domestic and foreign literatures on graphene anticorrosion films and organic anticorrosion coatings, and formed hierarchical and organized knowledge structures. The preparation, optimization and improvement of graphene anticorrosion film were reviewed. The corrosion acceleration problems and solutions in the application were discussed. According to the role of graphene in organic anti-corrosion coatings, the improvement of shielding, bonding and self-repairing effect of graphene-based composite materials on organic anti-corrosion coatings are reviewed from the perspective of applied and theoretical research. And the improvement of graphene-based materials on electrochemical protection performance of cathodic-protective organic anticorrosion coatings are discussed.

Research Progress on Rare Earth Nanocrystals for In Vivo Imaging and Sensing in Near Infrared Region

Lin Xiong, Yong Fan, Fan Zhang — 2019-09-18 00:00:00.0

In vivo imaging and sensing play a critical role in modern biological and medical research. Compared with other techniques such as computed tomography (CT), positron emission tomography (PET) and nuclear magnetic resonance (NMR), fluorescence imaging and analysis are featured by fast feedback, high sensitivity, and high spatiotemporal resolution. Especially, the application of near infrared (NIR) light as both excitation and emission signals provides increased tissue penetration and improved imaging quality and sensitivity due to reduced light scattering and auto-fluorescence. Among various materials investigated for in vivo imaging and bio-sensing, lanthanide-based nanocrystals display rich excitation/emission wavelengths in the NIR range, good photo and chemical stability, large Stokes shifts. In recent years, the research on lanthanide-based nanocrystals for in vivo imaging and sensing has seen rapid progress. Through nanoscale material design and synthesis, it is possible to fine tune the optical properties of lanthanide-based nanocrystals. By properly choosing different lanthanide ions as activators and sensitizers, multiple excitation/emission wavelengths can be obtained; The careful design of core-shell structure of nanocrystals enables improved fluorescence efficiency and tailorable fluorescence life time through controlled energy transfer. On the other side, the surface of lanthanide-based nanocrystals can be modified though coating、absorption or ligand exchange to enhance the biocompatibility, targeting capability, and bio-responsiveness. Taking advantage of this high flexibility and versatility, there are great opportunities for these lanthanide-based nanocrystals in various in vivo imaging and sensing applications. This review first outlines the general technique requirements for in vivo imaging and sensing. Then, the composition, synthesis and basic properties of lanthanide-based nanocrystals are briefly introduced. Subsequently, the routes for tailoring the optical and biochemical properties of lanthanide-based nanocrystals are discussed in detail, with an emphasis on the material designs and surface modifications for in vivo imaging and analysis. It is expected that this work will inspire new ideas for accelerating the clinic translation of rare earth nanocrystals-based imaging and sensing techniques.

Construction and Application of DNA-two-dimensional layered nanomaterials sensing platform

Jingyuan Chi, Jing Li, Shaokang Ren, Shao Su, Lianhui Wang — 2019-09-18 00:00:00.0

Combining the specific recognition ability of DNA molecules with the superior physical and chemical properties of two-dimensional (2D) layered materials, a DNA-2D layered nanomaterial sensing platform was constructed. More and more researchers are devoted to develop this sensing platform, which has become one of the important research directions in the field of chemical/biological sensors. In view of the rapid development of the 2D layered materials, this paper firstly introduces the construction principle of the DNA-2D layered material sensing platform. Then we mainly review the application of the sensing platform in the analysis of chemical and biological molecules, including metal ions, mycotoxins, ATP, amino acid, antibiotics, nucleic acids, proteins and cancer cells. Finally, the future of this sensing platform is prospected.

Research Progress in Functional Metal-Organic Frameworks for Tumor Therapy

Zeng Jin-Yue, Wang Xiao-Shuang, Zhang Xian-Zheng, Zhuo Ren-Xi — 2019-09-09 00:00:00.0

Malignant tumor is considered to be one of the most threatening diseases to human health because it is easy to metastasis and relapse, hard to cure with high mortality. Construction of anti-tumor drug delivery systems would effectively improve the therapeutic efficiency of traditional tumor therapy agents. However, the complicated tumor micro-environment as well as the individual diversity of tumor would lead to low efficiency or treatment failure. The conventional tumor treatments, such as chemotherapy, radiotherapy and surgery, have been unable to satisfy the demand for tumor therapy owing to the severe side effect and low therapeutic efficiency. In recent years, researchers have designed a lot of multifunctional nano-drug carriers for efficient tumor therapy with reduced side effects. Metal-organic frameworks (MOFs), a class of ordered porous crystal materials, have received significant research attention for their applications in gas adsorption and separation, catalysis, drug delivery, immobilized bio-macromolecules and tumor therapy. Due to tunable inorganic building blocks and organic linkers, MOFs can not only integrate drugs or photosensitizers into periodic arrays, but also possess large pore sizes and high surface areas for drug encapsulation. Currently, the biomedical research of MOFs mainly includes the preparation of multifunctional biocompatible nanomaterials through controllable synthesis and reasonable surface modification. MOFs based nanomaterials with desired physiological functions have been widely used for targeting tumor imaging and therapy by utilizing their unique physical and chemical properties. This review is aimed to summarize recent progress on the bio-functionalization of MOFs, including new design strategies and application in tumor therapy. Particularly, the construction of MOF-based nanoplatforms for tumor therapy on the basis of biomedical polymer modified MOFs was also described in detail. The development trends of MOFs for biomedical application are also prospected. We expect that our effort will offer a preliminary understanding to design MOF-based drug delivery systems and acquire the therapeutic strategies of MOF-based nano-medicine for future clinical biomedical applications.

Preparation and Catalytic Performance of Supported Catalysts Derived from Layered Double Hydroxides

Yu Jun, Yang Yusen, Wei Min — 2019-09-05 00:00:00.0

Supported catalysts have been widely used in a large variety of industrial processes, including ammonia synthesis, energy conversion and fine chemical synthesize. Layered double hydroxides (LDHs) are a class of two-dimensional functional anionic materials. By virtue of the unique structural characteristics (e.g., tunability of host layers, high dispersion of metal cations and structure topological transformation), LDHs have shown potential applications in heterogeneous catalysis as precursors or supports. In this review, we highlight high-performance monometallic or bimetallic supported catalysts by using LDHs as supports/precursors, or by utilizing mixed metal oxides (MMO) as supports via topotactic transformation from LDHs. Their recent progresses in electrocatalysis, oxidative dehydrogenation, selective hydrogenation and syngas conversion reaction are reviewed. In the final section, future opportunities and challenges in the preparation of LDHs-based catalysts are discussed, and some strategies to resolve these critical problems are further proposed.

Flexible Electronic Skin with Multisensory Integration

Zhao Shuai, Zhu Rong — 2019-09-05 00:00:00.0

Flexible electronic skins (E-skins) with human-like multiple sensing capabilities of perceiving various stimuli, have attracted more and more attentions for their wide applications in wearable electronics, health monitoring, humanoid robotics, and smart prosthesis. However, to meet the rigorous requirements for these complicated applications, challenges still exist in multifunctional integration, high performance, simple structure, low-cost fabrication, and easy signal processing. This review focuses on the significant sensing capabilities that are necessarily required in E-skins, including perceiving stimuli of pressure, temperature, humidity, flow, and materials. Various mechanisms are utilized in multiple kinds of sensors in current study, such as piezoresistivity, thermoelectricity, electrical impedance, convective heat transfer, etc. Multisensory integration is the basic characteristics of E-skins that various stimuli are perceived simultaneously. There are mainly three mechanisms applied in multisensory integration, that is, direct-integration method, functional-materials based method, and uniform sensing method. The advantages and disadvantages of each method are analyzed. Finally, the challenges and future development on multisensory integration of E-skins are summarized.

Recent Advances in Enzymatic Catalysis for Preparation of High Value-Added Chemicals from Carbon Dioxide

Liang Shan, Zong Minhua, Lou Wenyong — 2019-08-23 00:00:00.0

With the rapid development of modern industry, coal, petroleum, natural gas and other fossil fuels have been excessively consumed, along with an increasing large quantities of greenhouse gases (e.g. carbon dioxide, CO₂) are produced. It is urgent to develop sustainable green energy and abate the detriment of carbon dioxide on global environment. CO₂ is a cheap carbon source that can be converted into high value-added chemicals by chemical, photochemical, electrochemical or enzymatic methods to realize the recycling of CO₂. It is a win-win strategy to solve the energy and environmental crisis caused by global carbon emissions. Inspired by natural CO₂ metabolic process, enzymatic transformation provides an alternative strategy for efficient recycling of CO₂. Compared with traditional chemical, photochemical or electrochemical methods, the enzymatic route holds advantages of green, high efficiency, mild and excellent selectivity, which is expected to bring new revolutionary opportunities for efficient utilization of CO₂. Thus, in this present review, we firstly introduce the brief background about enzymatic conversion for CO₂ capture, sequestration and utilization. Next, we depict six major routes of the CO₂ metabolic process in cells, which are taken as the inspiration source for the construction of enzymatic systems in vitro. Subsequently, recent advances in enzymatic conversion of CO₂ that catalyzed by various single enzymes and multi-enzyme cascade systems are systematically reviewed. Some emerging approaches for construction of immobilized single-or multi-enzyme systems, directed evolution and artificial modification of enzymes, and cofactor regulation during the enzymatic processes are also discussed. Finally, the defects and shortcomings of enzymatic approaches are summarized, and the future perspectives are finally put forward. Based on this present review, we aim to provide theoretical reference and practical basis for more efficient enzymatic utilization of CO₂ to produce high value-added chemicals.

Controlled assembly of chiral structure of diphenylalanine peptide

Li Qi, Jia Yi, Li Junbai — 2019-08-16 00:00:00.0

Chirality is ubiquitous in nature and it plays an important role in both biological and material sciences. Inspired by nature, scientists have prepared various chiral structures or hybrid materials by self-assembly of polypeptides, amino acids, carbohydrates and their derivatives. These studies provide a good model for understanding of supramolecular chirality and mimicking the self-assembly of organisms. In the past decade, diphenylalanine (FF) and its derivatives have attracted great attentions and have been substantially studied. FF is derived from the core recognition motif of the Alzheimer's disease β-amyloid polypeptide, and it could readily self-assemble into nanotubes, nanowires, nanovesicles, nanofibers and microtubes. Moreover, the polymorphisms of FF-based assemblies can be easily manipulated by controlling the experimental conditions such as concentrations, solvents, pH and temperatures. However, there is few report on the chiral structures obtained from the self-assembly of FF and its derivatives. In this paper, we selected cationic diphenylalanine peptide (CDP) as the assembly units and have obtained CDP nanofibers and helical fibers in ethanol solution by controlling the aging time. Scanning electron microscope (SEM) and atomic force microscope (AFM) were used to characterize the morphologies of CDP assemblies. The mechanism for the formation of CDP nanofibers and helical fibers in ethanol solution was studied by infrared spectroscopy and circular dichroism spectroscopy. It was found that CDP was first assembled into nanofibers. With the increase of aging time, CDP nanofibers twisted and finally assembled into helical fibers similar to the ropes. Spectral data analysis showed that the transformation of nanofibers into helical fibers was mainly due to the strong electrostatic repulsion between positive charges in adjacent peptide molecules and the β-sheet secondary structure controlled by hydrogen bonding between peptide segments. This work realizes the regulation of supramolecular assembly structure by simply controlling the ripening time, and provides a simple and feasible method for the controlled preparation of supramolecular chiral assembly.

Recent Advances in the Structural Studies on Cytosine Deaminase APOBEC3 Family Members and Their Nucleic Acid Complexes

2019-08-15 00:00:00.0

Apolipoprotein B mRNA catalytically edited protein APOBEC3 (A3) is a family of proteins in the intracellular retrotransposon defense system, including seven members APOBEC3A (A3A), APOBEC3B (A3B), APOBEC3C (A3C), APOBEC3DE (A3DE), APOBEC3F (A3F), APOBEC3G (A3G) and APOBEC3H (A3H) encoded in a tandem array on human chromosome 22. They deaminate cytosine in single-stranded DNA and RNA substrates, which play a variety of roles in human health and disease. Among them, A3DE, A3F, A3G and A3H restrict replication of human immunodeficiency virus-1 (HIV-1) in strains lacking the virus infectivity factor protein (Vif) by deaminating cytidine in virus cDNA. Subsequent replication of the virus cDNA generates the hallmark G-to-A hyper-mutations, causing proviral inactivation. HIV-1 develops countermeasures to antagonize this intrinsic host defense response. Its Vif protein facilitates polyubiquitination of A3 members by recruiting an E3 ubiquitin ligase complex, which results in the proteasomal degradation of A3 proteins. To better understand the deamination mechanism of A3 proteins, we here reviewed the research progress on the structures of free A3 family members and their complexes with single-stranded DNA or double-stranded RNA. It includes the structures of the apo- forms of N- and/or C-termini domains of A3A, A3B, A3C, A3F, A3G and A3H, or the chimeric forms of their functional domains, and their complexes with nucleic acids, which demonstrate the basis of how A3 proteins to identify target base cytosine in hot motifs 5'-TC or 5'-CC in DNA, and then to conduct catalytic deamination. We simply described how the key residues of A3 members are involved in DNA or RNA interactions, the common properties of their structures, and their interactions with DNA or RNA. We partially discussed the interactions between A3 proteins and Vif, therefore, this review might be helpful to rationally design anti-virus drugs to disrupt these interactions. We finally suggested the new research directions about how to make full-length A3 proteins containing N-terminal CD1 and C-terminal CD2 domains, and how to study the interactions between these full-length A3 proteins and nucleic acids through cryo-EM and other techniques.

2018-09-15 00:00:00.0

Mechanistic Investigation of Light-induced Asymmetric Hydrogenation of TMSBO by Anoxygenic Photosynthetic Bacteria

Hu Rui, Zhang Chengping, Pei Zhisheng — 2013-04-10 00:00:00.0

Enantiomerically pure organosilicon compounds 3-butyn-2-ol not only play an important part in asymmetric synthesis and functional materials, but also many of them are bioactive and can be applied as silicon-containing drugs, such as (S)-3-butyn-2-ol or its derivative (S)-4-(trimethylsilyl)-3-butyn-2-ol {(S)-TMSBL} is a crucial intermediate for the synthesis of 5-lipoxygenase inhibitors. The anoxygenic phototrophic bacteria capable of reducing TMSBO to the (S)-TMSBL with high yield and ee were screened, using absolute configuration, stereoselectivity, and yield as benchmarks. 51 anoxygenic phototrophic bacteria strains were tested. We, for the first time, describe the efficient synthesis of enantiopure (S)-TMSBL, which is a crucial intermediate for the synthesis of 5-lipoxygenase inhibitors through the light-controlled asymmetric hydrogenation of TMSBO by photosynthetic bacteria Thiocapsa roseopersicina SJH001, which is a newly isolated photosynthetic bacteria strain that has the capacity to capture light energy and to generate NADPH through photosynthetic electron-transfer reactions. No oxygen or other metabolic intermediates were used, which make it easy to keep higher activities of redoxase and to separate reduced product, the reducing power of NADPH generated through photosynthesis also can be used in the reduction of exogenous substrates. A novel NADPH dependent carbonyl reductase was separated from Thiocapsa roseopersicina SJH001. The enzyme gave a single band on SDS-PAGE, which was purified through ammonium sulfate, Q-sepharose anion exchange column, gel filtration chromatography on a Superdex 200 column from cell-free extract. The molecular mass of the enzyme was about 44.5 kDa, relative enzyme activity was 449.8 U/mg, which is comparable to the previously reported carbonyl reductases from other sources. These results suggested that pH, light intensity, heat-treat biocatalysis with different temperature, substrate concentration has great influence on the enzyme activity and configuration of carbonyl reductase ((S)-carbonyl reductase and (R)-carbonyl reductase) from Thiocapsa roseopersicina SJH001. We propose a probable mechanism for light-induced asymmetric hydrogenation of TMSBO to produce (S)-TMSBL by anoxygenic photosynthetic bacteria.

Studies on the Complexation of di-Amide Based Macrocycles with Pyridine N-oxides

2012-06-28 00:00:00.0

A new cationic host molecule was synthesized by reaction of the di-amide based macrocycle with methyl iodide and the structure was confirmed by NMR, ESI-MS spectra. The complexation behavior of the di-amide based macrocycles with pyridine N-oxide guests was investigated by means of ESI-MS and ¹H NMR. The results showed that the cationic host can not only bind the pyridine N-oxide hosts to form 1∶ 1 pseudorotaxane-like complexes but also have much stronger binding ability than the corresponding neutral hosts.

Synthesis of Novel Chiral Stationary Phase Based on Atom Transfer Radical Polymerization and Click Chemistry

Wang Huaisong, Peng Jiangtao, Wei Jiping, Jiang An — 2012-06-28 00:00:00.0

A novel chiral stationary phase was synthesized via the combination of atom transfer radical polymerization (ATRP) and click chemistry. In the synthesis, the silane coupling agent 3-(2-bromoisobutyryl)- propyl triethoxysilane (BPE) was chosen as the ATRP initiator and immobized on the porous silica gel. The polymer chains of poly(2-methyl-3-butyn-2-ol methacrylate) (pMBMA) were grafted on the silica substrates by surface-initiated ATRP. This “grafting-from” technique was used to synthesize polymers with controllable molecular weight and narrow molecular weight distributions. For immobilizing the chiral selector, azide-modified β-cyclodextrin (β-CD) was synthesized and bounded on the pMBMA by click chemistry, which can avoid the side-reactions in the preparation. The materials with different pMBMA chain density and length on the silica gel surface were prepared. Several pharmaceuticals were used to evaluate the enantioseparation ability of the materials under reversed-phase high performance liquid chromatography. The results demonstrate that ATRP can well design the polymer structure, and click chemistry can provide an effective route in the β-CD immobilization for chiral discrimination. It was found that the retention and separation factors of chiral compounds could be improved by adjusting the pMBMA chain density and length on the surface of silica gel.

Alkali (Alkali Earth) Metal Ions with 2-(3'-Hydroxy-2'-pyridyl)benzoxazole Cation-π Complexes and Its Intramolecular Proton Transfer Process: A Theoretical Investigation

Yi Pinggui, Liu Zhengjun, Wang Zhaoxu, Hou Bo, Yu Xianyong, Li Xiaofang — 2012-04-23 00:00:00.0

The structures of 2-(3'-hydroxy-2'-pyridyl)benzoxazole (HPyBO) with alkali (or alkaline earth) metal ions (Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺ and Ca²⁺) were fully optimized at the 6-311++G(d,p) level by using B3LYP density functional theory and the binding energies were calculated at the same level. The result shows that the cation-π interaction between alkali (or alkaline earth) metal ions and HPyBO complexes are very strong, some of the interactions are even comparable to chemical bonding. The relative energies show that cation-π interaction can change the energy barrier of intramolecular proton transfer. When considering the solvent effect of water, the relative energies of isomers and the energy barrier of intramolecular proton transfer are changed to some extent. In addition, the properties at the BCPs (bond critical points) of intramolecular hydrogen bond in the complexes are also discussed.

Structure, Antibacterial Activities and DNA Cleavage of a Copper(II) Complex with 2-(2'-Pyridyl)benzimidazole and L-Alaninate

Lu Yanmei, Ou Zhibin, Hu Wei, Le Xueyi — 2012-01-20 00:00:00.0

A new copper(II) complex: [Cu(HPB)(L-Ala)(ClO₄)(H₂O)]₂·H₂O [HPB ＝ 2-(2'-pyridyl) benzimidazole, L-Ala＝L-alaninate], was synthesized and characterized by elemental analysis, IR, UV-Vis, molar conductivity, ES-MS and single crystal X-ray diffraction. The crystal belongs to the monoclinic space group P2₁, with the crystal cell parameters: a＝1.1900(2) nm, b＝0.80500(16) nm, c＝1.9700(4) nm, β＝ 94.78(3)°, Z＝2, D_c＝1.672 g·cm^-3, F(000)＝968, residual factors R₁＝0.0427, wR₂＝0.1106 [I>2σ(I)], S ＝0.999. The central Cu(II) ions for the complex show a distorted and elongated octahedral geometry in which two nitrogens of HPB and the carboxylate oxygen atom O and the amino nitrogen atom N of L-Ala bind at the molecular plane, a water molecule and one oxygen atom of perchlorate are coordinated at the axial site. The complex was tested for its ability to inhibit the growth of two gram-positive (B. subtilis, S. aureus) and two gram-negative (E. coil, Salmonella) bacteria by doubling dilutions method, and DNA interaction of the complex has been studied. The result showed that the MICs of the complex against the bacteria are in the range of 50～80 μg·mL^-1, and can cleave pBR 322 DNA in the presence of vitamin C with hydroxyl radicals as the active species.

Synthesis, Characterization and Fungicidal Activity of Piperidinothienopyrimidinones

2011-12-05 00:00:00.0

Ten new piperidinothienopyrimidinone derivatives were synthesized from the reaction of carbodiimide intermediate with primary, secondary amines and alcohols catalyzed by sodium alkoxide. The structure of the compound were confirmed by elemental analysis, 1H NMR, MS and single crystal X-ray determination. The fungicidal activities of all the compounds were researched the results showed that some compounds showed good fungicidal activity. Among them, compound 7b exhibited fungicidal activity against Botrytis cinereapers, Rhizoctonia solani, and Gibberella zeae with inhibitive rates of 76.19%, 68.83% and 56.52%.

The Study of Homology Modeling and High-throughout Screening with Computer of a New Inhibitor of Panax β-AS

2011-11-25 00:00:00.0

The Preparation of TiO2 Photocatalyst Dual-modified by Transition Metal Doping and Carbon Nanotube (CNT) Grafting

2011-11-25 00:00:00.0

A new method for the preparation of TiO2 dual-modified by transition metal doping and carbon nanotube (CNT) grafting was proposed. Fe-NiO/TiO2 was prepared by sol-gel method. Then CNTs were grafted on Fe-NiO/TiO2 by fluidized bed chemical vapor deposition (FBCVD) method. The dual-modified CNT/Fe-Ni/TiO2 composite photocatalyst has been characterized by X-ray diffraction (XRD), Raman spectra, FESEM, TEM, UV–vis absorption spectra and photoluminescence spectra. The photocatalytic activities of prepared samples were investigated by the photodegradation of methylene blue (MB). The results show that CNT grafted on TiO2 had good graphite structure，and small part of TiO2 was transformed from anatase to rutile during FBCVD process. Double modification of transition metals and CNT can effectively overcome intrinsic defects of TiO2 in small specific surface area and low quantum efficiency. And the photocatalytic activity has been improved significantly.

Synthesis of Tunable Absorption Peak of Chitosan-Stabilized Gold Nanoplate and the Growth Mechanisms

2011-11-25 00:00:00.0

By chitosan as a stabilizer and reducing agent, the tunable surface plasmon resonance (SPR) absorption peak of gold nanoplate has been successfully fabricated by water bath heating of solution containing HAuCl4, chitosan and gold nanoseeds. The SEM images indicate that the gold nanoplates were mainly composed of triangular and truncated triangular shape. The edge is about 170nm. X-ray diffraction analyses indicate that the gold nameplates were pure single crystals with {111} planes as their basal planes. The growth mechanisms on synthesis of chitosan-stabilized gold nano-plate were discussed. Under optimum conditions the SPR absorption peak of gold nanoplate in-plane dipolar is 920 nm. The experiment results showed that the near-infrared SPR absorption peak and the absorption intensity can be effective controlled by controlling the amounts of CTS and gold seeds, water bath temperature and bath time.

Highly Dispersed Pt Nanoparticles Supported on Mesoporous Carbon and its Electrocatalytic Performance for Ethylene Glycol Oxidation

2011-11-25 00:00:00.0

Mesoporous carbon (MC) with high mesopore content and narrow pore size distribution was prepared using colloidal silica as hard template and Pluronic F127 triblock copolymer as soft template, respectively. Then highly dispersed Pt catalyst supported on MC was achieved by ethylene glycol (EG) reduction method. Electrooxidation behavior of EG on the Pt/MC catalyst electrode in sulfuric solution was investigated using cyclic voltammogram (CV), chronoamperometry, linear sweeping voltammogram (LSV) and electrochemical impedance spectra (EIS) analysis. The experimental results indicate that the electrocatalytic performance of the Pt/MC catalyst for EG oxidation is much higher than that of Pt/XC72R catalyst. EIS analysis further reveals that the electrooxidation reaction of EG on the Pt/MC catalyst electrode has a lower charge-transfer resistance. The higher electrocatalytic activity of the Pt/MC catalyst may be due to the promotion of the MC support with large pore size and uniform mesoporous structure on electron transfer and mass transfer.

UPLC-TOFMS based chemical profiling approach to evaluate chemical composition of augmentation toxicity in combination of radix aconiti and pinellia praeparata

2011-11-24 00:00:00.0

Abstract: In the present study, an ultra performance liquid chromatography coupled with time-of-fight mass spectrometry (UPLC-Q-TOFMS) based chemical profiling approach was used to evaluate chemical constitution between co-decoction and mixed decoction of radix aconiti and pinellia praeparata. Two different kinds of decoctions, namely radix aconiti and pinellia praeparata co-decoction: water extract of mixed two herbs, and radix aconiti and pinellia praeparata mixed decoction: mixed water extract of each individual herbs, were prepared. Batches of these two kinds of decoction samples were subjected to UPLC-Q-TOFMS analysis, the datasets of tR-m/z pairs, ion intensities and sample codes were processed with supervised partial least squared discriminant analysis (OPLS–DA) to holistically compare the difference between these two kinds of decoction samples. The results of positive ion mode showed significant difference between two kinds of decoction samples, the content of hypaconitine, mesaconitine, aconitine, deoxyaconitine, 10-OH-mesaconitine, 10-OH-aconitine increased, while the content of dehydrated benzoylmesaconine, cammaconine, talatizamine, acetyltalatizamine, carmichaeline, pengshenine A, benzoylmesaconine, dehydrated benzoylhypaconine increased in samples of co-decoction of radix aconiti and pinellia praeparata. The content of diester-diterpenoid alkaloids increased, while the content of monoester-diterpenoid alkaloids decreased, which may be basis of chemical composition in combination of radix aconiti and pinellia praeparata.

Preparation and pH-Sensitive Drug Delivery Study of mPEG-poly(Imidazole Propyl-Asparagine)-poly(L-Alanine)

2011-11-25 00:00:00.0

Stimuli-sensitive drug delivery systems have attracted considerable interest in recent years for biomaterials scientists. It is well known that the pH value drops from physiologically 7.4 to that lower than 6.5 in tumor tissues, and such difference can be used as a trigger for drug releasing. Poly(amino acid)s (PAAs) have been studied for decades in the fields of drug delivery system due to their biocompatibility, biodegradability, precise secondary conformation and structural versatility. In this study, a novel biodegradable ABC type triblock copolymer mPEG-poly(benzyl L-aspartate)-P(L-Alanine) (mPEG-PBLA-PLAla)was synthesized by N-carboxyl anhydride ring-opening polymerization. Imidazole groups (pKa~ 6.0) were tethered to the side chains of poly(L-Asparagine) segments by aminolysis. An antitumor agent, doxorubicin (DOX), was successfully loaded into the nanocarrier via combined actions of hydrophobic and ?-? interaction. The drug release profiles displayed a pH-dependent behavior. DOX release rate increased significantly as the solution pH dropped from the physiological pH (7.4) to acidic (5.5). This is most likely due to protonation and a change in hydrophilicity of the imidazole groups in the poly(L-Asparagine). This new approach may serve as a promising platform to formulate magnetic targeted drug delivery systems.

Dendronized Carbohydrate Liquid Crystals II——Liquid Crystallinity Study

2011-11-24 00:00:00.0

Liquid crystallinity of dendronized carbohydrate liquid crystals, which contain carbohydrate core and mesogen branches DOBOB (3, 4, 5-tris (p-dodecyloxybenzyloxy) benzoic acid), was studied by DSC, thermal polarized optical microscopy, XRD and CD/UV spectrum. The number of branches affects the liquid crystallinity significantly. Dendrimer that contains four branches has the highest liquid crystal structure order, and the clearing point is also higher than the other two dendrimers which contain five branches. Otherwise, supramolecular chirality is also expressed in the mesophase formed by these dendronized carbohydrates, which may provide inspiration in searching for chiral mesophase of carbohydrate liquid crystals.

Dendronized Carbohydrate Liquid Crystals I——Molecular Design and Synthesis

2011-11-24 00:00:00.0

Traditional carbohydrate liquid crystals are composed of sugar moiety substituted by n-alkyl chains. There are still quite limited categories in this liquid crystal library. In this study, dendronized carbohydrate liquid crystals were synthesized by divergent-convergent method. Three carbohydrates—2-acetylglucosamine, glucosamine and glucose—were chose as core units, and wedge shape dendron DOBOB acid (3, 4, 5-tris (p-dodecyloxybenzyloxy) benzoic acid) as branches. DOBOB acid was synthesized by convergent method, then a series of halogenated carbohydrate derivatives were synthesized, and finally these two building blocks were jointed by condensation reaction to obtain the target products.

Theoretical studies on cation -π interactions 2: Density -funtional theory investigation on the configurations of and interactions in ammonium cation -bibenzene complexes

1999-08-15 00:00:00.0

Density - functional theory (DFT) B3lLYP/6 - 31G^* approach has been employed to calculate the possible configurations ammonium - bibenzene (C~6H~6…NH~4^+…C~6H~6) complex. The calculation results indicate that the most stable structure of the complex is the configuration where the ammonium cation located between two benzenes with two hydrogen atoms pointing to each benzene ring.The calculated IR spectrum shows that the geometry is reasonable.The bond length, total atomic charges,the coefficiet of the molecularorbital, frontier orbital energys, and Mullicken bonding population of the complex indicate that the binding between the ammonium and two benzenes involved the s-π interaction between hydrogens of ammonium and the carbon atoms of benzenes near to the hydrogens of ammonium, with electron transfer occured from the two benzne rings to ammonium, forminmg a charge transfer complex.The calculated results also imply that,similar to that of the ammonium caton-benzene transfer complex, the interaction characteristic of the ammonium cation-bibenzene complex is a typical hydrogen bond.The calculated thermodynamic parameters demonstrate this feature.The nomal mode analysis of the predicted vibrational frequency shows that the characteristic vibration mode of the complex is located at about 230cm^-^1, correspondeding to the back and forth vibration of the ammonium cation paralleled to the bezene rings.

Potential Energy Functions for the Electronic States X¹Σ^＋, A¹P and B¹Σ^＋ of Molecule BF

2013-12-31 00:00:00.0

The energies, equilibrium geometries and harmonic frequencies of the ground state X¹Σ^＋, the first degenerate state A¹P and the second state B¹Σ^＋of molecule BF have been calculated using the method Group Sum of Operators of SAC/SAC-CI with the basis sets D95＋＋, 6-311＋＋g, 6-311＋＋g** and D95(d). Comparing the four basis sets abovementioned, the conclusion was gained that the basis set 6-311＋＋g** was the most suitable for the energy calculation of molecule BF. The whole potential curves for these three electronic states were further scanned adopting SAC/6-311＋＋g** method for the ground state and SAC-CI/6-311＋＋g** method for the excited states, then a least square was fitted to Murrell-Sorbie function, and last the spectroscopy constants were calculated, which are in better agreement with the experimental data. It was believed that Murrell-Sorbie function form and SAC/SAC-CI method were suitable for not only the ground state, but also the low-lying excited states.

Acta Chimica Sinica-Forthcoming Articles

Electrochemical detection of xanthine and study for the inhibition of uric acid based on chitosan/nitrogen doped reduced graphene oxide modified electrode

Cyclic Lanthanide-based Molecular Clusters: Assembly and Single Molecule Magnet Behavior

New Polymerizations Based on Green Monomer of Carbon Dioxide

Two Polymorphs of Triphenylamine-substituted Benzo[d]imidazole:Mechanoluminescence with Different Colors and Mechanofluorochromism with Emission Shifts in Opposite Direction

Self-Assembly of Cyclic Dipeptides and Their Fluorescent Properties

A new method for enriching baicalin in Scutellaria baicalensis Georgi by metal organic framework material ZIF-8

Recent Progress of Photocatalysis Based on Metal Halide Perovskites

Zn/Ni Bimetallic Relay Catalysis: One Pot Intramolecular Cycloisomerization/Intermolecular Amidoalkylation Reaction toward Oxazole Derivatives

Glycan Analysis in Cellular Secretion

Visualization of The Electrolyte Migration under Electrode Conditioning by ToF-SIMS

Recent Advances on Surface Modification of Li- and Mn-Rich Cathode Materials

Preparation of Eu-doped ZnO/MIL-53 (Fe) Photocatalyst and its Catalytic Performance for Selective Oxidation of Alcohols

Study on the Migration and Transformation Mechanism of Graphene Oxide in Aqueous Solutions

Review of theoretical and applied research of graphene in anti-corrosion film and organic anti-corrosion coatings

Research Progress on Rare Earth Nanocrystals for In Vivo Imaging and Sensing in Near Infrared Region

Construction and Application of DNA-two-dimensional layered nanomaterials sensing platform

Research Progress in Functional Metal-Organic Frameworks for Tumor Therapy

Preparation and Catalytic Performance of Supported Catalysts Derived from Layered Double Hydroxides

Flexible Electronic Skin with Multisensory Integration

Recent Advances in Enzymatic Catalysis for Preparation of High Value-Added Chemicals from Carbon Dioxide

Controlled assembly of chiral structure of diphenylalanine peptide

Recent Advances in the Structural Studies on Cytosine Deaminase APOBEC3 Family Members and Their Nucleic Acid Complexes

Mechanistic Investigation of Light-induced Asymmetric Hydrogenation of TMSBO by Anoxygenic Photosynthetic Bacteria

Studies on the Complexation of di-Amide Based Macrocycles with Pyridine N-oxides

Synthesis of Novel Chiral Stationary Phase Based on Atom Transfer Radical Polymerization and Click Chemistry

Alkali (Alkali Earth) Metal Ions with 2-(3'-Hydroxy-2'-pyridyl)benzoxazole Cation-π Complexes and Its Intramolecular Proton Transfer Process: A Theoretical Investigation

Structure, Antibacterial Activities and DNA Cleavage of a Copper(II) Complex with 2-(2'-Pyridyl)benzimidazole and L-Alaninate

Synthesis, Characterization and Fungicidal Activity of Piperidinothienopyrimidinones

The Study of Homology Modeling and High-throughout Screening with Computer of a New Inhibitor of Panax β-AS

The Preparation of TiO2 Photocatalyst Dual-modified by Transition Metal Doping and Carbon Nanotube (CNT) Grafting

Synthesis of Tunable Absorption Peak of Chitosan-Stabilized Gold Nanoplate and the Growth Mechanisms

Highly Dispersed Pt Nanoparticles Supported on Mesoporous Carbon and its Electrocatalytic Performance for Ethylene Glycol Oxidation

UPLC-TOFMS based chemical profiling approach to evaluate chemical composition of augmentation toxicity in combination of radix aconiti and pinellia praeparata

Preparation and pH-Sensitive Drug Delivery Study of mPEG-poly(Imidazole Propyl-Asparagine)-poly(L-Alanine)

Dendronized Carbohydrate Liquid Crystals II——Liquid Crystallinity Study

Dendronized Carbohydrate Liquid Crystals I——Molecular Design and Synthesis

Theoretical studies on cation -π interactions 2: Density -funtional theory investigation on the configurations of and interactions in ammonium cation -bibenzene complexes

Potential Energy Functions for the Electronic States X1Σ＋, A1P and B1Σ＋ of Molecule BF

Potential Energy Functions for the Electronic States X¹Σ^＋, A¹P and B¹Σ^＋ of Molecule BF