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  Subjects -> CHEMISTRY (Total: 841 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (593 journals)
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CHEMISTRY (593 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 233)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 55)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 68)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 222)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 213)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 3)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 295)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 121)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 98)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 13)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 176)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 142)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 258)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 12)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 58)
Dalton Transactions     Full-text available via subscription   (Followers: 22)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 17)

        1 2 3 | Last

Journal Cover Acta Chimica Sinica
  [SJR: 0.417]   [H-I: 29]   [1 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0567-7351
   Published by Chinese Chemical Society Homepage  [2 journals]
  • Real-time monitoring skin cell alignment on nano-grooves using electric
           cell-substrate impedance sensing (ECIS)
    • Authors: Jin Tongyu; An Yu, Zhang Fan, He Pingang
      Abstract: Cell alignment plays a crucial role in the repair and regeneration of tissues, which is caused by the "contact guidance" of micro/nano structures. In this paper, the nano-grooves with 200 nm in width, 400 nm in period and 75 nm in depth were fabricated on gold substrate with the technique of nanoimprint to simulate the extracellular matrix (ECM). Electric cell-substrate impedance sensing (ECIS) was employed firstly to real-time monitor cell alignment of human foreskin fibroblasts (HFF) and human immortal keratinocyte cells (HaCaT) on nano-grooves, which are two important functional cell types in skin wound-healing. The cell images displayed that the nano-grooves could induce the alignment of HFF cells, in which, the cell arrangement along the direction of nano-grooves occurred prior to the cell elongation. While, the nano-grooves couldn't influence the morphology of HaCaT cells, and their adhesion and spread were delayed. In the ECIS monitoring, HFF and HaCaT cells both presented increased normalized impedance (NI) values at their respective characteristic frequencies of 977 Hz and 1465 Hz on nano-grooves and flat electrodes with the prolongation of culture time during 24 h and the increasing trends of NI values were also similar:in the first 6 h, NI values increased faster, and then, the increasing rates declined obviously. HFF cells on nano-grooves generated more intense impedance signals with a larger distinction of increasing rate than those on flat electrodes, indicating that the nano-grooves could promote the adhesion and spread of HFF cells and the directional arrangement had a larger impact on the variation of NI values than cell elongation. While, HFF cells adhered and spread in random directions, leading to the reduced difference in increasing rate of NI values. The NI values of HFF cells was further correlated with cell alignment, showing the enhanced impedance responses with the rising percentage of aligned cells. More importantly, there was a good linear correlation between NI values and the percentage of cells arranging along the direction of nano-grooves. In contrast, HaCaT cells had smaller NI values on the nano-grooves with the similar increasing rates, compared to the flat electrodes, revealing that the nano-grooves were less suitable for the adhesion and spread of HaCaT cells with almost no change of cell morphology, and the cell adhesion could cause more obvious variation of NI values than cell spread. Our research would provide a support for the development of complex cell sensors based on ECIS and its application in clinical research field.
      PubDate: 2017-09-08 00:00:00.0
       
  • Research Progress on the Super-wettability of Colloidal Photonic Crystals
    • Authors: Cui Liying; Fan Shasha, Yu Cunlong, Kuang Minxuan, Wang Jingxia
      Abstract: In recent years, the wettability of colloidal PCs has attracted much interest from researchers due to potential applications in printing, sensor, microfluidics and so on. In this paper, we present two kinds of research work related to PCs' wettability. On the one hand, the functional colloidal PCs have been fabricated from the modification of its wettability. Where, the wettability of PCs can be modified from superhydrophilic, superhydrophobic, amphiphilic, gradient wettability, controllable wettability and patterned wettability. Wettability is an important property of solid surface and can be generally controlled mainly by its surface chemical composition and surface topographic structure. Surface chemical composition determines surface free energy (i.e., hydrophilicity/hydrophobicity), while the surface topographic structure can amplify hydrophilicity or hydrophobicity, based on the Wenzel and modified Cassie equation. Thus, PCs with specific wettability have been fabricated based on their intrinsic, well-ordered surface topographic structure, and chemical composition. The superhydrophilic and superhydrophobic PCs have been achieved based on the amplification effect of the surface well-ordered topographic structure. The gradient PCs have been fabricated by changing the topographic structure. The PCs with controllable wettability can be obtained when introducing a responsive group onto PCs' surface. The underwater oil-adhesion properties of PCs have been controlled by varying the latex from spherical or cauliflower-like to single cavity. On the other hand, functional PCs are fabricated from the substrate with specific wettability. Typically, high-quality and crack free PCs are achieved from superhydrophobic substrate, pattern PCs from the hydrophilic-hydrophobic substrate, PC dome with excellent wide-angle property is fabricated from hydrophobic substrate. Otherwise, gas-liquid or liquid-liquid interface has also been included as a special substrate for the fabrication of functional PCs, such as flower-shape or cake-shaped Janus PCs. Colloidal photonic crystals (PCs), the periodic arrangement of monodispersed latex spheres, have attracted much interest from researchers due to their unique light manipulation properties. The combination of the special wettability and light manipulation properties of PCs will bring many novel properties and promising applications. Finally, the outlook and challenges for colloidal photonic crystals with special wettability are discussed. The work is of importance for the creation of novel functional materials.
      PubDate: 2017-09-06 00:00:00.0
       
  • Electrocatalytic Activity of MnO2 Supported on Reduced Graphene Oxide
           Modified Ni Foam for H2O2 Reduction
    • Authors: Song Congying; Sun Xun, Ye Ke, Zhu Kai, Cheng Kui, Yan Jun, Cao Dianxue, Wang Guiling
      Abstract: Fuel cells which use hydrogen peroxide as oxidant have been widely studied and presents good development foreground. As a liquid fuel, H2O2 possesses advantages of easily storage and transportation which make it can be widely used in underwater and pace as a power source. At present, the most widely used catalysts for H2O2 electroreduction are noble metal catalysts. Compared with noble metals, transition metal oxides possesses advantages of low cost and extensive sources. However, the catalytic activity of transition metal oxides is still much lower than noble metals. Therefore, many efforts should be made to improve the electrochemical performance of transition metal oxides. In this work, rGO is used as an additive to improve the electrochemcial performance of MnO2. An original electrode of MnO2 in-situ supported on reduced graphene oxide modified Ni foam (MnO2/rGO@Ni foam) is prepared through two-step hydrothermal methods. Primarily, the novel current collector of rGO@Ni foam is obtained with larger surface area which is beneficial to the next loading of MnO2. Secondly, MnO2 is grown on the rGO@Ni foam also by a hydrothermal treatment. Besides large surface area, the addition of rGO can provide more channels for electron transfer and then accelerate the reaction rate of H2O2 reduction. The morphology and phase composition of the as-prepared electrode are investigated by measurements of X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). It can be concluded from SEM and TEM images, both rGO and MnO2 exhibit sheet-like structure and there are many gaps existing between these sheets. Especially, the as-prepared MnO2 nanosheets builds a honeycomb structure which makes positive effects on the contact between H2O2 and catalyst. And XRD and HRTEM results show that MnO2 and rGO are successfully prepared on Ni foam. The electrochemical performance of the MnO2/rGO@Ni foam electrode toward H2O2 reduction is investigated by cyclic voltammetry and chronoamperometry in a three-electrode system in solutions of NaOH and H2O2. Results reveal that the reduction current density of H2O2 reduction on the MnO2/rGO@Ni foam electrode reaches 240 mA/cm2 in a solution of 1.0 mol/L H2O2 and 3 mol/L NaOH at -0.8 V which is much higher than that on MnO2 directly supported on Ni foam (MnO2@Ni foam). At the same time, a better stability is also achieved on the MnO2/rGO@Ni foam electrode. Generally speaking, the addition of rGO highly improves the electrocatalytic activity and stability of the as-prepared electrode indicating great application prospect in the future.
      PubDate: 2017-09-06 00:00:00.0
       
  • Nanoplasmonic Biological Sensing and Imaging
    • Authors: Su Yingying; Peng Tianhuan, Xing Feifei, Li Di, Fan Chunhai
      Abstract: The localized surface plasmon resonance of metal nanoparticles is the collective oscillation of electrons on particle surface. The localized electromagnetic interaction brings a series of novel functions and applications. Plasmonic nanomaterials have been the significant part of nanophotonics, since its' localized surface plasmon resonance (LSPR) can focus incident phonons at the nanoscale surface. The unique plasmonic property is highly sensitive to their size, shape, coupling between particles as well as local dielectric environment. These properties can be utilized for the development of new biosensing and bioimaging applications. To date, many LSPR sensing strategies have been developed with outstanding measurement capabilities, enabling detection down to the single-molecule level, including LSPR-based sensing, surface-enhanced Raman scattering, metal-enhanced fluorescence, dark-field light-scattering, metal-mediated fluorescence resonance energy transfer. Moreover, the unique optical stability of plasmonic nanoparticles enables them as ideal probes in cellular imaging. Here, recent examples on application of plasmonic nanostructures in sensing and bioimaging are summarized, and perspectives are provided as well.
      PubDate: 2017-09-06 00:00:00.0
       
  • Progress and Perspectives on High Voltage, Flame Retardant Electrolytes
           for Lithium-Ion Batteries
    • Authors: Xia Lan; Yu Linpo, Hu Di, Chen Z. George
      Abstract: The electrolyte is an indispensable constituent in lithium ion batteries, and its role conducts electricity by means of the transportation of charge carries between the pair of electrodes. Its properties directly affect the energy density, cycle life and safety of the battery. However, there are two major challenges to using carbonate-based electrolytes in recent lithium ion batteries (LIBs) to further increase the energy density of the devices without compromising the safety. One is that carbonate-based electrolytes are not sufficiently stable at the positive electrode, and the other is their relatively high flammability. Therefore, developing high voltage and flame retardant electrolytes for LIBs is highly desired. Herein, we review the recent progress and challenges in new electrolytes, focusing on high-voltage electrolytes, flame retardant electrolytes and highly concentrated electrolytes. Among the reported electrolytes, highly concentrated electrolytes are worth a special attention, showing various unusual functionalities, for example, high oxidative stability, low volatility, high reductive stability, and non-corrosive to Al. These special properties are totally different from that of the conventional 1 M LiPF6/EC-based electrolytes, which are result from solution structures. A discussion is also provided in this review on the prospects of further development of new electrolytes for LIBs.
      PubDate: 2017-09-06 00:00:00.0
       
  • A Review of Carbon-based Non-noble Catalysts for Oxygen Reduction Reaction
    • Authors: Guoyu Zhong; Hongjuan Wang, Hao Yu, Feng Peng
      Abstract: Proton exchange membrane fuel cells (PEMFCs) that directly convert chemical energy into electrical energy can be applied to portable power and fuel cell electric vehicles, due to their advantages such as environment-friendliness, high power density and high convert efficiency. However, the high loading of Pt-based catalysts on the cathode oxygen reduction reaction (ORR) hinder the commercial application of PEMFCs for the high price, resource shortage and easy poisoning of Pt. Thus, developing inexpensive, high performance and durability non-noble metal cathode catalysts will promote the large-scale commercialization of PEMFCs. As the most likely alternative to Pt, carbon-based non-noble ORR catalysts have been widely studied. In this review, firstly, the electrocatalytic mechanism for ORR is simply introduced. Secondly, the carbon-based non-noble ORR catalysts are divided into transition metal-nitrogen-carbon compounds (M-N-C) and non-metal heteroatom-doped carbon catalysts; the researches of material preparations and active sites are summarized and discussed. Thirdly, the applications of carbon-based non-noble ORR catalysts in PEMFC are reviewed. Although great progress has been achieved in this area of research and development, there are still some challenges for carbon-based non-noble ORR catalysts. Firstly, the ORR electrocatalytic mechanism isn't clear, especially carbon-based non-noble catalysts. Secondly, the ORR active sites of carbon-based non-noble catalysts remain controversial, which can be mainly divided into the transition metal coordination compounds, the doped heteroatom, the filled metal and the defect sites. Thirdly, the actual activity and stability of carbon-based non-noble catalysts are still below the PEMFC target. In summary, the future research directions on carbon-based non-noble catalysts for PEMFC applications would be proposed as follows:1) fundamentally understanding the ORR mechanisms and their relationship with catalyst active site structures and composition using both theoretical calculations and experimental approaches; 2) improving catalyst activity and stability to satisfy the practical application of PEMFC.
      PubDate: 2017-09-06 00:00:00.0
       
  • Electrochemical Assay for Acetylcholinesterase Activity Detection Based on
           Unique Electro-catalytic Activity of Cu (II)-thiol Coordination Polymer
    • Authors: Wang Qin; Nie Zhou, Hu Yufang, Yao Shouzhuo
      Abstract: Acetylcholinesterase (AChE), as a key enzyme, ubiquitously exists in the peripheral nervous system. It mainly functions terminating neurotransmission at the cholinergic synapse through the rapid hydrolysis of acetylcholine (a neurotransmitter) into choline and acetate, which is intimately related to Alzheimer's disease, inflammatory processes, and nerve-agent poisoning. In this study, we developed a novel electrochemical method for probing AChE activity and screening its potential inhibitor based on the in-situ formation of thiocholine-Cu(Ⅱ) coordination polymer (denoted as TCh-Cu(Ⅱ) CP). The detection mechanism is on the basis of the concept, that is, AChE could catalyze the hydrolysis of its substrate acetylthiocholine (ATCh) to produce a thiol-compound thiocholine (TCh). Subsequently, TCh reacted with Cu(Ⅱ) to form a positively charged TCh-Cu(Ⅱ) CP via S-Cu bond. Since the graphene (GO) is a negative compound due to its plenty of carboxyl groups, TCh-Cu(Ⅱ) CP could be absorbed onto the graphene-modified glassy carbon electrode (GO/GCE) via electrostatic interaction. What's more, the CP/GO/GCE can electro-catalyze the O-phenylenediamine (OPD), generating a high current signal. We also conducted a series of experiments to verify the formation and electro-catalysis of TCh-Cu(Ⅱ) CP and investigate the selectivity of the TCh-Cu(Ⅱ) CP-based assay for AChE. As a result, it is clearly observed that the electrochemical response gradually increases with the increasing concentrations of AChE (0.05-100 mU/mL) and a detection limit of our method is estimated to be~0.03 mU/mL (S/N=3). Furthermore, compared to the traditional methods, our electrochemical assay has more simple detection procedure with better sensitivity and selectivity and has great potential in applications in many important areas, such as neurobiology, toxicology, and pharmacology, especially for the effective treatment of Alzheimer's disease.
      PubDate: 2017-09-04 00:00:00.0
       
  • Optical Sensors Based on Optical Interference of Nanoporous Film
    • Authors: Wang Yafeng; Yang Qian, Su Bin
      Abstract: Optical sensors are devices that transform the interaction between medium and analyte to optical signal. Optical interference is a technique that has been widely applied in optical sensors, which is label-free, fast and non-invasive. Light reflected from the top and bottom surfaces of single layer film, or each interfaces of multilayer film in optical sensors leads to constructive and destructive fringes of the optical interference pattern. Nanoporous films with large surface-to-volume ratio are beneficial to improve the sensitivity and lower the limit of detection of the sensors, which is typically used in the form of single layer, double layer or multilayer (usually served as photonic crystal). In this article, we introduce and review the applications of nanoporous films of silicon, anodic aluminum oxide, titanium dioxide and metal-organic framework in optical sensors based on the optical interference. A perspective of developments in this research field is also provided.
      PubDate: 2017-09-04 00:00:00.0
       
  • Highly Sensitive Detection of Mercury Ion Based on Plasmon Coupling
    • Authors: Qian Guangsheng; Zhao Wei, Xu Jingjuan, Chen Hongyuan
      Abstract: Mercury is very harmful to the environment and human health even at low concentration. Methods for sensitive detection of mercury ion (Hg2+) have increasingly been developed over the past decade owing to the rapid development in nanotechnology. However, the limits of detection (LODs) of these methods are mostly not satisfactory enough to meet the demand of monitoring trace amounts of mercury ion. DNA thymine (T bases) can react with the mercury ion to form T-Hg2+-T structure, and this interaction has been proved to be much more stable than the interaction between thymine and its com-plementary adenine (A bases). Based on this principle, a series of ultra-sensitive DNA-based colorimetric biosensors, mostly using Au nanoparticles (AuNPs) as DNA carriers, have been designed for detection of mercury ion. In this study, we report a new strategy for highly sensitive Hg2+ detection based on Hg2+-induced AuNPs assembly. AuNPs of different sizes (s-AuNPs of 18 nm and c-AuNPs of 52 nm) were modified with oligonucleotides containing a sequence of continuous T bases. In the presence of Hg2+, s-AuNPs would be bound to c-AuNPs in the solution owing to oligonucleotide hybridization, forming a core-satellites nanostrucure. This process was accompanied by a color change of the scattering light from green to orange as observed under dark-field microscopy and a corresponding distinct scattering peak shift. The scattering spectra of the AuNPs were obtained using a spectroscopic system which was established autonomously. The scattering peak shift of color-changed spots corresponded with Hg2+ concentration. It was increased linearly with logarithm of Hg2+concentration over a wide range from 1 pmol/L to 1 nmol/L, with the correlation coefficient of 0.983 (R2=0.983), and the detection limit of Hg2+ was estimated to be 1 pmol/L. Other metal ions, such as Ag+, K+, Ca2+, Mg2+, Zn2+, Cd2+, Fe2+, Pb2+, Ni2+, Mn2+, Al3+, induced negligible scattering peak shifts for AuNPs under the same conditions, which showed that this strategy exhibited excellent selectivity towards Hg2+. Moreover, satisfactory results were obtained when the proposed approach was applied to detect Hg2+ in real samples with recoveries of 98.7%~103.1% and 105.6%~108.2% for river water and tap water, respectively.
      PubDate: 2017-09-04 00:00:00.0
       
  • Direct Asymmetric Aza-Vinylogous Mannich Reaction of Nitrones from Isatins
           and Ketimines
    • Authors: Shi Minglin; Zhan Gu, Du Wei, Chen Yingchun
      Abstract: Direct asymmetric vinylogous Mannich reaction is an efficient and powerful method for the synthesis of δ-amino-α,β-unsaturated carbonyl compounds; however, the nucleophiles are generally limited to γ-butenolides and α, α-dicyanoolefins. Therefore, it is highly desirable to design new vinylogous nucleophiles and develop the related asymmetric reactions. Recently, we disclosed a new type of nitrones derived from isatins and N-benzyl hydroxylamines, which could easily generate nitrone ylide species in the presence of a tertiary amine, and undergo asymmetric formal[3+2] cycloadditions with α,β-unsaturated aldehydes via iminium ion catalysis of a chiral secondary amine. Subsequently, we found that such nitrone ylides could isomerize to more interesting aza-dienolate-type intermediates, and engage in direct stereoselective aza-vinylogous Michael reactions with nitroalkenes under the catalysis of a bifunctional thiourea-tertiary amine, delivering chiral nitrone derivatives with extended carbon skeletons without subsequent cyclization. In this case, the same type of nitrones are employed as nucleophilic precursors under the catalysis of a cinchona alkaloid-based thiourea substance, and effectively assembled with isatins-derived ketimines to accomplish the direct asymmetric aza-vinylogous-type Mannich reactions. A series of densely functionalized nitrones with vicinal tertiary-quaternary stereogenic centers are furnished in high yields (70%~97%) with good to excellent stereoselectivity (83%~99% ee, >19:1 dr). Moreover, subsequent[3+2] dipolar cycloaddition reactions between the chiral nitrones and activated alkenes can be realized in exclusive diastereoselectivity, producing complex spirocyclic indolenine architectures incorporating a hydrogenated isoxazole ring. These nitrones, as a new type of aza-vinylogous nucleophiles, may have a wide range of applications in asymmetric synthesis in the future. A representative procedure for the asymmetric aza-vinylogous-type Mannich reaction is as follows:nitrone 1 (0.1 mmol), ketimine 2 (0.11 mmol), catalyst C5 (0.01 or 0.02 mmol) are added into an oven-dried vial equipped with a magnetic stirbar. Xylene (1.0 mL) is added and the mixture is stirred at 50℃ and monitored by TLC. After completion, the residue is purified by flash column chromatography on silica gel eluting with petroleum ether/ethyl acetate (15:1 to 5:1) to afford the product 3.
      PubDate: 2017-09-04 00:00:00.0
       
  • Peptide Supramolecular Self-Assembly:Structural Precise Regulation and
           Functionalization
    • Authors: Juan Wang; Qianli Zou, Xuehai Yan
      Abstract: Biomolecular self-assembly plays a significant role for physiological function. Inspired by this, the construction of functional structures and architectures by biomolecular self-assembly has attracted tremendous attentions. Peptides can assemble into diverse nanostructures, exhibiting important potential for biomedical and green-life technology applications. How to achieve the structural precise regulation of various nanostructures and functionalization by precise control of structures is the two key challenges in the field of peptide self-assembly. As the assembly process is a spontaneous thermodynamic and kinetic driven process, and is determined by the cooperation of various intermolecular non-covalent interactions, including hydrogen-bonding, electrostatic, π-π stacking, hydrophobic, and van der Waals interactions, the reasonable regulation of these non-covalent interactions is a critical pathway to achieve the two goals. To modulate these non-covalent interactions, one of the common used methods is to change the kinetic factors/external environment, including pH, ionic strength, and temperature, etc. These kinetic factors can effectively influence the interactions between peptides and solvents, resulting in dynamic and responsive variations in structures through multiple length scales and ultimate morphologies. However, the fatal disadvantage is the lacking of the precise regulation of assembled structures in the molecular level with consideration of both thermodynamics and kinetics. Compared with changing the external environment, the specific and precise molecular design is more favorable to achieve the structural precise regulation. The molecular structures and the component of building blocks can be rationally designed. For example, one can modulate the interactions between two or more than two building blocks by changing the physicochemical properties of each building block, enabling self-assembly and structural diversity of the final nanostructures. Furthermore, by combining peptides and other functional biomolecules (such as porphyrins), the functionalization of assembled nanostructures and architectures can be achieved more easily and flexibly. In this review, we will focus on the structural precise regulation and the functionalization of assembled peptide nanostructures. It is believed that the precise regulation of nanostructures is promising to promote the development of peptide-based materials towards green-life technology applications.
      PubDate: 2017-09-04 00:00:00.0
       
  • Experimental research of protein translocation using solid-state nanopore
    • Authors: Sha Jingjie; Xu Bing, Chen Yunfei, Yang Yanjing
      Abstract: For proteins' diverse range of structural and functional features, they are important populations of biomolecules within organisms. Common methods to detect proteins are with the help of fluorescence or enzyme. Due to the advantages like lable-free and single-molecule detection, nanopore technology provides a novel platform for proteins' characterization. In this experiment, the patch clamp amplifier is used to apply the voltage and acquire the tiny current blockage. The Si3N4 membrane drilled with a nanopore separated the buffer solution into two sides:cis and trans. When the voltage applied into the buffer solution, charged proteins would been driven through the pore from one side to the other. Then, a series of current blockages could be obtained. By analysing these data, the size and conformation of the biomolecules could be acquired. In this paper, we using solid-state nanopore detected single protein and protein-protein complexes. The nanopore was characterized firstly. Then, both the applied voltage and the pH of the electrolyte solution were regulated. Under the low voltage, the sample proteins could be regarded as a rigid spheroid, and the dwell time is decreased with the voltage increasing. It was found that, the charges carried by proteins could be improved by higher pH of buffer solution, so that the dwell time would been shortened. Furthermore, based on the high specific between the antigen and antibody which are essentially proteins, the translocation events before and after the addition of specific antigen into the solution with antibody were compared. Results showed that the relative current drop of the complex is larger than the pure antibody, implying that the antigen has been bound into the antibody. Due to the difference of excluded volume, the antibody and antigen-antibody complexes could be distinguished by the solid-state nanopore. In the future, the nanopore technology is promising to be applied into the recognition of multiply proteins and protein-protein interaction. Keywords:Bovine serum Albumin (BSA), Antigen, Antibody, Solid-state nanopore, Single-molecule detection.
      PubDate: 2017-09-04 00:00:00.0
       
  • Research progress in thermoelectric materials for sensor application
    • Authors: Gang Liu; Tie Wang
      Abstract: Sensor as one core component of modern intelligent industrial, have attracted enormous attention due to exert a significant influence on the design and function of key products. In a paper, the thermoelectric materials were reported to play a key role for the high sensitivity, response and stability to make a sensor, such as silicon, carbon, lead, tellurium, precious metal, organic and catalysis based thermoelectric materials. Because of high purity silicon, the silicon-based thermoelectric materials were extremely efficient in sensor data processing and transmission. Carbon-based thermoelectric materials as structure of the sensor, there are two important examples. One is Graphene is applied to a sensor because of the high conductivity, with the product in Graphene layer. It is benefit for sensor signal transmission, increase sensitivity.Other is carbon nanotube, which feature structure is flexible, can knit the something as we need. With the sensor miniaturization, like silk, carbon nanotubes, need at the formation of processing and weaving, it was so large-area film that more widely harness industrial potential.Lead-based thermoelectric materials mainly used in infrared sensors, because of the nature lead, which can be sensitive to infrared specially.Telluride-based thermoelectric materials, especially Bismuth Telluride and Antimony Telluride, it can form PN junction to apply in the side of flexible sensor. It used to detect a pulse and can be promote as a mature product.The precious metals-based thermoelectric materials, gold or silver, it can improve conductivity of as the dopant. It is an important direction of development that the precious metals-based integrated into the organic thermoelectric materials. It can also adjust the sensitivity of Miniaturization Sensor. Organic thermoelectric materials benefited for Miniaturization Sensor due to the good stability and variability. Moreover, Copper-bismuth alloy -based thermoelectric materials were used to make gas sensors are an attempt to greatly, which broaden the application of thermoelectric materials in the field of sensors. Generally speaking, as the Miniaturization Sensor, the inorganic thermoelectric materials had the feature of high electrical conductivity in order to enhance the sensitivity of Sensor, whereas the organic thermoelectric materials had high stability in order to maintain the stability of Sensor.
      At present, high ZT were obtained by the low dimensional thermoelectric material, whose thermoelectric performance can be effectively improved. At the same time, the development trend of Sensor is miniaturization. They have a common development direction. It is benefit to each other. The low dimensional thermoelectric materials will promote the advanced sensor development. Miniaturization Sensor aimed at the space -saving through the high integrated function. For example, thermoelectric materials with nano-structure of quantum dots, lines, as well as body shape, which adopted to be effectively arranged and assembled, can be achieved with a material that carries a variety of functions and improve the practical value of the sensor.
      PubDate: 2017-09-04 00:00:00.0
       
  • Preparation of Crack-free Inverse-opal Films by Template/Matrix
           Co-assembly
    • Authors: Luo Wenhao; Zhu Shuihong, Lin Youhui, Liu Xiang Yang
      Abstract: Recently, there has been a significant interest in utilizing well-ordered, porous inverse-opal films for applications in optical, electronic and (bio)chemical fields. However, uncontrolled defects are always formed during their preparation process, which limit their practical applications. In this work, we examine the feasibility of using template/matrix co-assembly strategies to fabricate crack-free inverse opal thin films. Polystyrene spheres (PS) are chosen as a colloidal template, and two matrix precursors[tetraethoxysilane (TEOS) precursor and regenerated silk fibroin solution] are used for the current study. Our scanning electron microscope (SEM) and optical spectrum results show that, for the TEOS-based system, the resulting silica gel due to the sol-gel transition of TEOS can effectively fill the gap between particles, but cannot affect the self-assembly of PS colloidal particles. After selective removal of the PS template, centimeter-scale crack-free and well-ordered inverse opal films can be obtained. In addition, for a constant concentration of TEOS, the film thickness and order degree of structure can be simply tuned by adjusting the concentrations of colloidal spheres. In comparison with indirect approach through template self-assembly and liquid infiltration, such a co-assembly approach can effectively minimize the associated cracking and avoid the need for ma-trix infiltration into the preassembled colloidal spheres. On the other hand, macro-molecule silk fibroin has a relatively strong interaction with PS colloidal particles, which is demonstrated by SEM and confocal images. Due to their interaction, silk fibroin molecules are preferably adsorbed on the surface of PS spheres, which can restrain the self-assembly of colloidal particles. As a result, it cannot form well-ordered silk film based on such co-assembly strategy. That is to say, the co-assembly approach is not suitable for systems that matrices have strong interactions with templates. These findings pave the way to use the template/matrix co-assembly strategy for rationally designing and developing crack-free inverse opal films and to apply such well-ordered and porous materials in a variety of fields.
      PubDate: 2017-09-04 00:00:00.0
       
  • Monolayer-gated Ion Transport in Artificial Ion Channels Based on A
           Nanoporous Gold Membrane
    • Authors: Yan Nan; Xiao Tianliang, Liu Zhaoyue
      Abstract: Biological ion channels that intelligently control the transport of ions or molecules through the cell membrane in response to external stimuli can maintain the balance between the extracellular and intracellular substances, which ensures the normal life activities of the organism. The development of artificial ion channels with analogous function to the biological counterparts is of great significance because of their possible applications as ion switches and sensors. In this paper, we describe a new type of artificial ion channels based on de-alloyed nanoporous gold membrane with three-dimensional nanochannels. The nanochannels were built by electrochemical etching of gold-silver alloy in concentrated nitric acid. The surface morphology and component of nanoporous gold membrane were characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDX). The ion transport properties of artificial ion channels were characterized with current-voltage curves which was measured by a picoammeter. Our results indicate that this nanoporous gold membrane demonstrates an ion rectification phenomenon because of the electrochemical polarization of gold under an electric field. Subsequently, a layer of hydrophobic molecules was assembled on the surface of nanoporous gold membrane by strong Au-thiol bonds after immersed in the solution of 1-dodecanethiol. The measurements of water contact angles (CAs) indicated that the modification of 1-dodecanethiol molecules converted the surface water CA of nanoporous gold membrane from 36.5° to 120.6°. This hydrophobic monolayer prevents the transport of water-soluble ions, which makes the channels exist in an "off" state. The stimulus of surfactant in the electrolyte is favorable for the wetting of channel surface by aqueous electrolyte, which makes the channels exist in an "on" state for water-soluble ions. Therefore, the monolayer-modified nanoporous gold membrane can serve as a surfactant-gated ion switch. Our work provides a new idea for the preparation of artificial ion channels, which can be applied for intelligently responsive artificial system.
      PubDate: 2017-09-04 00:00:00.0
       
  • Possible Mechanisms of Water Binding to the Oxygen-Evolving Complex during
           the S4-S0 Transition:A Theoretical Investigation
    • Authors: Guo Yu; Liu Yu, Qi Juanjuan, Li Hui, He Lanlan, Lu Linan, Liu Cui, Gong Lidong, Zhao Dongxia, Yang Zhongzhi
      Abstract: It has been acknowledged that molecular oxygen produced in photosynthesis originates from water, rather than carbon dioxide. Dioxygen releases in the S4-S0 transition immediately prior to a new water binding to the oxygen-evolving complex, but hardly any investigation has been carried out on the binding mechanism up to date. Based on the open-cubane oxo-oxyl coupling mechanism in the S4 state of photosynthetic oxygen evolution, in this study we propose three possible pathways of water binding to the oxygen-evolving complex Mn4CaO4 during the S4-S0 transition, i.e. water binding to Ca trans to O5, water binding to Ca cis to O5, and water binding to Mn4> trans to O5. Broken-symmetry density functional theory (BS-DFT) calculations have demonstrated the thermodynamic feasibility for all these possible modes, without an overwhelming inclination for a certain manner. Besides, all these styles do not bring about any difference embodied in the experimental kinetic data on substrate water exchange in the S1, S2 and S3 states, for the basically same structures of the S0 state derived from these different routes. Therefore, it is considered that the alternative mechanisms could coexist coordinately in the connecting stage between S-state cycles. Importantly, diverse forms of substrate selectivity are deduced according to different water binding ways, which exert obvious influences on the present and later S-cycles. In the long run, however, it can be seen that the two waters binding in the S4-S0 and S2-S3 periods together constitute the components of the released O2. What matters is variation of the time to become substrates for different water binding modes during the S4-S0 transition, either in the current cycle or in the following cycles. Meanwhile, it is indicated that the dangler Mn4(Ⅲ)/(IV) which possesses a five-coordinated pyramidal ligand field in both S'0/S'3 states, along with Ca(Ⅱ) on which the carrousel rearrangement of water ligands can also occur, are essential structural elements of the S-state advancement and oxygen evolution. Thus, Mn4 and Ca may be in charge of water delivery to the active sites of Mn4CaO5 from the nearby external water channels formed by crystal waters in hydrogen-bond interactions. On the whole, the geometric flexibility of the Mn cluster plays an important role in photosynthetic water oxidation. In the respects of water binding modes in the S4-S0 transition and corresponding substrate identifications for a specific S-cycle, we are looking forward to further confirmations or supplements from the experimental evidences of the targeted isotope labeling combined with mass spectrometry, infrared spectroscopy and site directed mutagenesis, etc. Our investigation may provide useful information and references for the mechanistic elucidations on photosynthetic water oxidation, especially in substrate water identifications.
      PubDate: 2017-09-04 00:00:00.0
       
  • In situ SERS Investigation of SPR-driven Catalytic Reactions on Au
           Nanoparticles Monolayer Film
    • Authors: Zhang Chenjie; Zhang Jing, Lin Jieru, Jin Qi, Xu Minmin, Yao Jianlin
      Abstract: The activity and uniformity of surface-enhanced Raman scattering (SERS) effect has been already become the critical role for fundamental research and practical application. Herein, Au nanoparticle monolayer films (Au MLF) were fabricated based on the self-assembly of nanoparticles at the air/water interface by introduction of polyvinylpyrrolidone (PVP) as additional agent. The change of assembly duration allowed the formation of Au MLFs with different density. Due to the excitation mode and intensity of localized surface plasmon resonance (LSPR) varying with the nanoparticle density, the activity and uniformity of SERS substrate could not be taken into account at the same time. For example, loose Au MLF exhibited excellent SERS and catalytic performance but poor uniformity, while compact Au MLF held excellent uniformity and reasonable SERS and catalytic performance. It demonstrated that the intensity of SERS signal was not only relevant to the activity but also to the number of "hot spots", while the conversion rate of surface plasmon resonance (SPR) induced catalysis was only associated with the activity of "hot spots". By using the compact film with relative standard deviation of SERS intensity and SPR catalytic efficiency less than 5% and 6% as the SERS substrate, the influence of the external environment on the SPR catalytic reaction was clarified. In this paper, the effect of laser power on the efficiency and reaction rate of SPR induced catalytic reaction was investigated according to the coupling reaction of para-aminothiophenol (PATP) and decarboxylation process of 4-mercaptobenzoic acid (MBA). It was found that the increase of laser power not only improved the efficiency of SPR catalytic reaction, but also accelerated the reaction rate from the perspective of reaction kinetics due to the heat effect and hot electrons generated by SPR. The results indicated that the rate of the SPR catalytic reaction was linear with the reciprocal of the square of the laser power. It provided a new approach for the determination of the kinetic parameters of the related surface processes.
      PubDate: 2017-09-04 00:00:00.0
       
  • Advances of Metal-Organic Frameworks in Adsorption and Separation
           Applications
    • Authors: Zhang He; Li Guoliang, Zhang Kegang, Liao Chunyang
      Abstract: As a new type of nano porous material, Metal-Organic Frameworks (MOFs) have been rapidly developed for decades. MOFs are synthesized via the self-assembling combination of inorganic metals and organic ligands, and they have many characteristics superior to the conventional porous materials. The ultrahigh surface area, high porosity, adjustable pore sizes, outstanding thermal and chemical stability enable MOFs to be promising materials for widespread applications. With the deepening of research in recent years, MOFs are successfully applied in diverse fields, such as catalysis, adsorption, separation, and biomedicine imaging, among others. The advances of MOFs used in adsorption and separation are reviewed in this paper, with an emphasis on storage of fuels, carbon capture, membrane separation, liquid-phase adsorption, and chromatographic separation and purification. In addition, the future research directions regarding MOFs in the adsorption and separation field are prospected also.
      PubDate: 2017-09-04 00:00:00.0
       
  • Modulation Mechanisms of Polymeric Emulsion Stability and Porous Material
           Architecture within Ultrasonic Fields
    • Authors: Zhu Xiannian; Chen Fang, Zhai Wei, Wei Bingbo
      Abstract: Ultrasonic emulsification has received great attention recently due to the great potential of tuning the emulsion droplets size compared to the traditional homogeneous mixing method. In this study, a series of polymeric emulsions were prepared by ultrasonic emulsification approaches. The relationships between ultrasonic power, emulsion destabilization mechanism and structure morphology of macroporous polymer material were studied. The water in toluene emulsion was prepared by mixing the polymer POSS-(PMMA)8 toluene solution (10 mg·mL-1) and water or Na2CO3 aqueous solution (0.1 mol·L-1) through different ultrasonic powers. The volume ratio of water/toluene was remained as 50:50. The evolution of emulsion droplets diameter distribution over time was analyzed based on optical microscopy data. The initial droplets diameter increased with the increase of ultrasonic power, and all emulsion droplets diameter distributions followed the diauxie curve. By changing the ion concentration in aqueous solution, excellent monodisperse emulsions with droplets diameter around 10 microns were acquired. It was found out that flocculation degree of emulsions prepared with Na2CO3 aqueous solution was increased with increasing of ultrasonic power. The relationship between ultrasonic power and emulsion stability was clarified by fitting the emulsion droplets diameter variation as the function of time. When ultrasonic power was below 750 W, Ostwald ripening dominated the instability mechanism of emulsion. Once the ultrasonic power achieved to 1000 W, the instability mechanism of emulsion was attributed to Ostwald ripening and coalescence at the same time. The macroporous polymer materials with adjustable pore diameter were prepared by dipping the glass fiber into salt containing emulsions. In this approach, POSS-(PMMA)8 not only acted as emulsifier during emulsion preparation, but also treated as the skeleton of porous materials. The droplet-size of emulsions was monitored by changing ultrasonic power, meanwhile the structure and morphology of porous materials could be controlled on the basis of emulsion template.
      PubDate: 2017-09-04 00:00:00.0
       
  • A Strong Segregation Theory for Ring Block Copolymers
    • Authors: Liu Ming; Yang Yingzi, Qiu Feng
      Abstract: Due to the ring structure with no free ends, the traditional strong-segregation theory for linear chains is not adequate for ring block copolymers. We developed the strong-segregation theory for ring block copolymers (SST-ring), by modifying both the entropic free energy term and the interfacial energy term. The ring block copolymer can only form two types of conformations, i.e., the loops on one side of an interface and the bridges connecting two interfaces. For the entropic energy originating from the stretching of the chain conformation under strong-segregation limit, we employ the strategy for calculating the entropic energy of looping and bridging chains connecting interfaces. Since the mixing of components is unavoidable for the ring triblock copolymers to adapt to the classical morphologies, we start from the propagating function of the self-consistent field theory, and deduce the formula of the interfacial energy between two two-component domains under the strong-segregation limit. The formula is reminiscent to the interfacial energy between two single-component domains, except that the Flory-Huggins parameter χAB between two components on each side of the interface is replaced by an effective parameter, χeff, which is a function of the composite fractions and the Flory-Huggins parameters between each components. The application of SST-ring to ring diblock copolymers is successful to describe the decreased characteristic length and the lifted order-disorder transition point, compared with the corresponding linear diblock copolymers with the same segment number N. We find that the critical χABN value of the ordered-disordered transition is 1.59 times that of the linear diblock polymers, and the characteristic lengths of the ring diblock copolymers are always 0.63 times of those of linear diblock copolymers. This agrees qualitatively with the predictions of the self-consistent theory, with slight quantitative difference originating from the strong-segregation limit assumption. For the SST-ring calculations for ring triblock copolymers in two-dimensions, corresponding to the film with the thickness much smaller than the radius of gyration of the polymer, we consider two types of micro phase structures:the classical morphologies (lamellae and cylinders) with multi-component domains, and the tiling-brick structures ([6,6,6] and[8,8,4], where the numbers denote the side numbers of the bricks) consisting of the single-component domains. SST-ring predicts that the ternary diagram consists of both types of the micro phase structures. When the Flory-Huggins parameters between any two components are equal, the phase diagram has a three-fold rotational symmetry to the center of the regular triangle, and three mirror symmetric axis crossing three vertices of the triangle, respectively. Our SST-ring theory is easy to be applied to different morphologies of ring block copolymers.
      PubDate: 2017-08-07 00:00:00.0
       
  • Electron Transport Pathways Through One-Dimensional Conjugated Carbon
           Chain Doped by Thiophene Ring
    • Authors: Yuanyuan He; Na Cheng, Jianwei Zhao
      Abstract: Represented by graphene and carbon nanotubes, one-dimensional (1D) conjugated carbon materials are potential ones to be used in molecular electronic devices. The further application of 1D conjugated carbon materials in optoelectronic devices requires that they have electron-poor/electron-rich characteristics, with the premise of high conductivity. Most of 1D conjugated carbon materials are constructed by aromatic rings as the basic units. Substitutional S atoms into benzene ring is an effective method to achieve electron doping into 1D conjugated carbon materials. Herein, to simulate the doping effect of 1D conjugated carbon materials, a series of oligbenzo[1, 2-b:4,5-b'] dithiophene (BmT) and oligothiophene (TnP) molecules were designed by substitutional doping thiophene ring into conjugated carbon skeleton. The influence of doping position and concentration on the electron transport properties were studied based on the nonequilibrium Green's function approach and density functional theory. Static electronic properties indicate that HOMO orbitals have higher delocalization on trans-configurations of BmT and TnP molecules as compared with cis-conjugations, indicating the higher conductivity of tran-BmT and tran-TnP. Dynamic transport behaviors demonstrate that the substitutional doping of thiophene rings can significantly improve the electron transport efficiency of carbon skeleton. The conductance trend of BmT and TnP molecules indicates that the electron transport efficiency through the compounds is dependent on their conjugation. The conductance of BmT and TnP molecules are not only dependent to the chain length, but also related to the energy gaps and electron transport pathways. Trans-BmT and trans-TnP are conjugated molecules with multiple pathways, however, cis-BmT and cis-TnP are conjugated molecules that can transform from a single pathway to multiple pathways, with the increase of chain length. The diversity of the electron transport behaviors of the thiophene-doped carbon skeletons is directly dominated by the electron transport pathways. Our work gives insight into the development of novel carbon-based molecular optoelectronic materials with high performance.
      PubDate: 2017-06-15 00:00:00.0
       
  • Theoretical study on the mechanism of photosynthetic oxygen evolution by
           ABEEM/MM/MD and BS-DFT
    • Authors: Guo Yu; Yao Yuan, Li Hui, He Lanlan, Zhu Zunwei, Yang Zhongzhi, Gong Lidong, Liu Cui, Zhao Dongxia
      Abstract: Charge parameters of atom-bond electronegativity equalization method (ABEEMσπ) for the oxygen-evolving complex (OEC) in the S2 state were established, which were applied to molecular dynamic (MD) simulation based on ABEEM/MM polarizable force field in order to study the mechanism of photosynthetic oxygen evolution, in combination with broken-symmetry density functional theory (BS-DFT). Charge fitting results at HF/STO-3G level (the reason why the basis set is adopted is shown in the cited literatures) show good linear correlation, proving the rationality and efficiency of the ABEEMσπ model in calculating charge distributions. It can be seen from MD simulations that bidirectional isomerizations of the Mn4CaO5 cluster accompany by the transfer of Ca-bound water molecule W3 to pentacoordinate Mn1(III)/Mn4(III). For the g=2 to g=4.1 form, W3 leaves for Mn4(III), while W3 moves to Mn1(III) for the inverse course. Both processes involve motions to the original positions of W4 to W3, W588 to W4, and local rearrangements of the water environment, which may indicate the importance of hydrogen bond network to biocatalysis. The observation of W3 coordination to the vacant site of Mn(III) as the sixth ligand proximal to O5 may imply W3 could be the fast-exchanging substrate water (Wf) in the S2 state, which makes O2 with O5 in the S4 state. Based on the inference, we investigate O-O bond formation in all the possible spin states for the two isomeric structures under the framework of oxo-oxyl radical coupling mechanism. It is demonstrated from BS-DFT calculations that O2 formation activity is significantly advantageous for the open-cubane structure than the closed-cubane form, i.e. the differences of barriers and driving forces are beyond 20 kcal/mol and 25 kcal/mol, respectively. For the open-cubane structure, the antiferromagnetic coupling of Mn1(IV)-O· stabilizes the reactants, and the spin-parallel feature between O· radical and Mn4(IV) lowers the barriers, and ferromagnetic coupling of Mn1-Mn3 ensures the release of triplet O2. For the closed-cubane structure, the antiferromagnetic coupled Mn4(IV)-O· changes to more stabilized Mn4(III)-oxo, losing the radical character of the ligand oxygen, which greatly increases the barriers. The ferromagnetic coupled Mn4(IV)-O· does not belong to the relatively stable electronic configuration of reactants, and cannot be formed by spin frustration from the stable spin states, for their large energy differences above 20 kcal/mol. Thus it cannot be accepted as the accesses of effective reaction channels. Our work expounds the exclusive role of the open-cubane OEC in oxo-oxyl coupling mechanism of O2 creation. It also reveals that the oxygen evolution reactivity is extremely dependent on the spin coupling ways of manganeses and oxygen radical, meanwhile, the structural flexibility of the OEC is essential to the S-state cycle and photosynthetic water splitting.
      PubDate: 2017-05-24 00:00:00.0
       
 
 
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