Functionalization of Metal–Organic Frameworks through the Postsynthetic Transformation of Olefin Side Groups

For the first time, the adaptability of the C?C double bond as a versatile precursor for the postsynthetic modification (PSM) of microporous materials was extensively investigated and evaluated. Therefore, an olefin‐tagged 4,4′‐bipyridine linker was synthesized and successfully introduced as pillar linker within a 9,10‐triptycenedicarboxylate (TDC) zinc paddle‐wheel metal–organic framework (MOF) through microwave‐assisted synthesis. Different reactions, predominately used in organic chemistry, were tested, leading to the development of new postsynthetic reactions for the functionalization of solid materials. The postsynthetic oxidation of the olefin side groups applying osmium tetroxide (OsO₄) as a catalyst led to the formation of a microporous material with free vicinal diol functionalities. The epoxidation with dimethyldioxirane (DMDO) enabled the synthesis of epoxy‐functionalized MOFs. In addition to that, reaction procedures for a postsynthetic hydroboration with borane dimethyl sulfide as well as a photoinduced thiol–ene click reaction with ethyl mercaptan were developed. For all of these PSMs, yields of more than 90 % were obtained, entirely maintaining the crystallinity of the MOFs. Since the direct introduction of the corresponding groups by means of pre‐synthetic approaches is hardly possible, these new PSMs are useful tools for the functionalization of porous solids towards applications such as selective adsorption, separation, and catalysis.     

Exploiting Aggregation To Achieve Phase Separation in Macrocyclization

The aggregation properties of poly(ethylene glycol) (PEG) can be exploited in organic synthesis to control dilution effects. Through the use of solvent mixtures containing PEG₄₀₀/MeOH, macrocyclization by Glaser–Hay coupling can be conducted at high concentrations. The origin of the selectivity has been studied by using surface tension measurements, UV spectroscopy, and chemical tagging and demonstrates the dependence of the yield and selectivity on the aggregation of PEG₄₀₀ and its ability to preferentially solubilize organic substrates, resulting in a phase separation from the catalyst system.     

Influence of surface properties on the interfacial adhesion in carbon fiber/epoxy composites

A polyacrylonitrile‐based carbon fiber was electrochemically oxidized in an aqueous ammonium bicarbonate solution with current density of up to 2.76 A/m² at room temperature. X‐ray photoelectron spectroscopy revealed that the oxygen content increased with increasing current density before approaching saturation. The increase can be divided into two regions, the rapid increase region (0–1.78 A/m²) and a plateau region (1.78–2.76 A/m²). The surface chemistry analysis showed that the interlaminar shear strength (ILSS) value of the carbon fiber/epoxy composite could be improved by 24.7%. The carbon structure was examined using Raman spectroscopy in terms of order/disorder in the graphite structure and the results indicated that the relative percentage of graphite carbon in the form of sp² hybridization increased above a current density of 1.39 A/m². The increasing non‐polar graphite carbon on the carbon fiber surface decreased the surface energy. As a result, both the surface free energy () and its polar component () decreased when current density increased above 1.78 A/m². The ILSS value had no direct relationship with the nature and surface density of the oxygen‐containing functional groups nor with the carbon structure. It is the surface free energy (), especially the polar component (), which played a critical role in affecting the interfacial adhesion of carbon fiber/epoxy composites. The ILSS value changed with increasing current density and could be divided into three distinct regions, as chemical interaction region (I), anchor force region (II) and matrix damage region (III). Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of glutathione in single HepG2 cells by capillary electrophoresis with reduced graphene oxide modified microelectrode

Determination of intracellular bioactive species will afford beneficial information related to cell metabolism, signal transduction, cell function, and disease treatment. In this study, the electrochemically reduced graphene oxide modified carbon fiber microdisk electrode (ER‐GOME) was used as a detector of CZE‐electrochemical detection and developed to detect glutathione (GSH). The electrocatalytic activity of the modified microelectrode was characterized by cyclic voltammetry. Under optimized experimental conditions, the concentration linear range of GSH was from 1 to 60 μM. When the S/N ratio was 3, the concentration detection limit was 1 μM. Compared with the unmodified carbon fiber microdisk electrode, the sensitivity was enhanced more than five times. With the use of this method, the average contents of GSH in single HepG2 cells were found to be 7.13 ± 1.11 fmol (n = 10). Compared with gold/mercury amalgam microelectrode, which was usually used in determining GSH, the electrochemically reduced graphene oxide modified carbon fiber microdisk electrode was friendly to environment for free mercury. Furthermore, there were several merits of the novel electrochemical detector coupled with CE, such as comparative repeatability, easy fabrication, and high sensitivity, hold great potential for the single‐cell assay.     

Design,synthesis and anti-influenza virus activities of terminal modified antisense oligonucleotides

Four novel terminal modified antisense oligonucleotides (ODNs) were designed, synthesized and tested for their anti-influenza virus activity. Initial biological studies indicated that lipophilic and rimantadin emodificated Flutide exhibited more potent anti-H1N1 activity than Flutide. Among them, lipophilic modificated ODN (Flutide-I) showed the most antiviral activity. The EC₅₀ value of Flutide-I for inhibiting H1N1 induced cytopathic effect (CPE) and H1N1 RNA were respectively (0.26 ± 0.16) μM and (0.11 ± 0.03) μM. The cytotoxicity of these compounds has also been assessed. No significant cytotoxicities were found for any of these compounds with the concentrations up to 20 μM.     

Enhanced in vitro anticancer activity of quercetin mediated by functionalized CdTe QDs

We report in this study the effects of red-emitting CdTe QDs capped with cysteamine(Cys-CdTe) on the in vitro anticancer activity of the well-known flavenoid quercetin(Qu). Various techniques, including the methylthiazolyldiphenyl-tetrazolium bromide assay, the real-time cell electronic sensing system, the optical and fluorescence imaging, and electrochemical methods have been utilized to study the potential interactions of Cys-CdTe QDs with Qu. The observations demonstrate that the safe-dosage Cys-CdTe QDs can greatly improve the drug uptake and enhance the inhibition efficiency of Qu towards the proliferation of cancer cells such as HepG2 cells. This study implies that Cys-CdTe QDs may be used for cancer therapy and that they exert a synergic anticancer effect when bound to drug molecules.     

CO Oxidation Catalytic Effects of Intrinsic Surface Defects in Rhombohedral LaMnO3

There is an ongoing effort to replace rare and expensive noble-element catalysts with more abundant and less expensive transition metal oxides. With this goal in mind, the intrinsic defects of a rhombohedral perovskite-like structure of LaMnO₃ and their implications on CO catalytic properties were studied. Surface thermodynamic stability as a function of pressure (P) and temperature (T) were calculated to find the most stable surface under reaction conditions (P=0.2 atm, T=323 K to 673 K). Crystallographic planes (100), (111), (110), and (211) were evaluated and it was found that (110) with MnO₂ termination was the most stable under reaction conditions. Adsorption energies of O₂ and CO on (110) as well as the effect of intrinsic defects such as Mn and O vacancies were also calculated. It was found that O vacancies favor the interaction of CO on the surface, whereas Mn vacancies can favor the formation of carbonate species.     

Operando XAFS on Hydrated Calcium Vanadium Bronze Cathode for Aqueous Zn-ion Storage

Multivalent ion storage and aqueous electrochemical systems continue to build interest for energy application. The Zn-ion system with 2 electron transfer and an ideal metal anode is a strong candidate but is still at the early stage of development. Using both in situ near-edge (XANES) and X-ray absorption fine structure spectroscopy, EXAFS, a nanostructured cathode material, Ca_xV₂O₅-H₂O (CVO), was probed at the V-K absorption edge. This operando study reveals the local electronic and geometric structure changes for CVO during galvanostatic cycling as the active material in an aqueous Zn-ion cell. The XANES data provides a fine resolution to track the evolution of the vanadium oxidative state and near-neighbor coordination sphere showing subtle shifts and delocalized charge. The Zn-ion influence on the V-K absorption edge is visualized using a difference technique called Δμ. Coupled with theoretical calculations and modelling, the extended region extracted local bonding information further confirms excellent electronic and structural reversibility of this vanadium oxide bronze in an aqueous Zn-ion electrochemical cell.     

Prediction of thermodynamic and surface properties of Pb−Hg liquid alloys at different temperatures

The thermodynamic properties, such as free energy of mixing, heat of mixing, activity and structural properties, such as concentration fluctuation in long wavelength limit, short-range order parameter of Pb–Hg liquid alloy at 600 K have been calculated using theoretical modelling. It has then been correlated with modified Butler model to compute the surface tension of the alloys at different temperatures. The Pb–Hg system at 600 K is found to be ordering at higher concentration of Pb.