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101.
Singh M Ford C Agarwal V Fritz G Bose A John VT McPherson GL 《Langmuir : the ACS journal of surfaces and colloids》2004,20(23):9931-9937
Micelles of cetyltrimethylammonium bromide (CTAB), when doped with increasing levels of 4-ethylphenol, show microstructural transitions from spherical micelles to elongated wormlike micelles, disks, and subsequently to globular and then to tubular vesicles. Wormlike micelles are observed at a dopant-to-CTAB molar ratio of 1:3. At higher dopant ratios (1:1), globular vesicles are observed which transition to tubular vesicles when the dopant becomes the predominant species at a ratio of 3:1. These transitions are reflected in small-angle neutron scattering analysis and, interestingly, can be directly observed through cryo-transmission electron microscopy. The para-substituted phenol is interfacially active and modulates interfacial curvature of the micelles. The observations of microstructure modifications have relevance to the synthesis of mesoporous materials using CTAB as the template. 相似文献
102.
Shear-induced orientation of a rigid surfactant mesophase 总被引:1,自引:0,他引:1
Singh M Agarwal V De Kee D McPherson G John V Bose A 《Langmuir : the ACS journal of surfaces and colloids》2004,20(14):5693-5702
An optically clear, crystalline, gel-like mesophase is formed by the addition of water to a micellar solution consisting of a mixture of 0.85 M anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and a 0.42 M zwitterionic surfactant phosphatidylcholine (lecithin) in isooctane. At 25 degrees C and water to AOT molar ratio of 70, the system has a columnar hexagonal microstructure with randomly oriented domains. The shear-induced orientation and subsequent relaxation of this structure were investigated by rheological characterization and small-angle neutron scattering (SANS). The rheological response implies that the domains align under shear, and remain aligned for several hours after cessation of shear. Shear-SANS confirms this picture. The sheared gel mesophase retains its alignment as the temperature is increased to 57 degrees C, indicating the potential to conduct templated polymer and polymer-ceramic composite materials synthesis in aligned systems. 相似文献
103.
The Micheal addition of ethyl 2-methoxy-, 2,4-dimethoxy- and 2,5-dimethoxybenzoylacetates with benzoquinone leads to ethyl 2-(rnethoxy or dimethoxy phenyl)-5-hydroxybenzofuran 3-carboxylates. Treatment of the henzofuran derivatives with anhydrous pyridine hydrochloride at 190–195° leads to hydroxy-6H-henzofuro[3,2-c] [1]benzopyran-6-ones. 相似文献
104.
Ford C Singh M Lawson L He J John V Lu Y Papadopoulos K McPherson G Bose A 《Colloids and surfaces. B, Biointerfaces》2004,39(3):143-150
Fluorescent silica/polymer nanocomposites have been synthesized by condensing tetramethyl orthosilicate (TMOS) around fluorescent polymer strands of poly(2-naphthol). The polymer is biocatalytically synthesized via peroxidase catalyzed polymerization in micelles of the cationic surfactant, cetyltrimethylammonium bromide (CTAB). Silica condensation at the micelle-water interface results in encapsulation of the polymer. Fluorescence spectroscopy and fluorescent light microscopy provide critical evidence that the polymer luminescence properties are conferred to the composite material. The fabrication of polymer entrapped in ordered, mesoporous materials represents a viable step toward the development of functional polymer-ceramic nanocomposites. 相似文献
105.
Singh M Tan G Agarwal V Fritz G Maskos K Bose A John V McPherson G 《Langmuir : the ACS journal of surfaces and colloids》2004,20(18):7392-7398
Dry reverse micelles of AOT in isooctane spontaneously undergo a microstructural transition to an organogel upon the addition of a phenolic dopant, p-chlorophenol. This microstructural evolution has been studied through a combination of light scattering, small-angle neutron scattering (SANS), NMR, and rheology. Several equilibrium stages between the system of dry reverse micelles of AOT and a 1:1 AOT/p-chlorophenol (molar ratio) gel in isooctane have been examined. To achieve this, p-chlorophenol is added progressively to the dilute solutions of AOT in isooctane, and this concentration series is then analyzed. The dry micelles of AOT in isooctane do not undergo any detectable structural change up to a certain p-chlorophenol concentration. Upon a very small increment in the concentration of p-chlorophenol beyond this "threshold" concentration, large strandlike aggregates are observed which then evolve to the three-dimensional gel network. 相似文献
106.
107.
108.
R. Giege J. Drenth A. Ducruix A. McPherson W. Saenger 《Progress in Crystal Growth and Characterization of Materials》1995,30(4):237-281
After an historical introduction and justification of the importance of proteins (as well as other macromolecules or macromolecular assemblies of biological origin) in modern biology but also in physics, this review presents the state of the field of macromolecular crystallogenesis. The basic questions underlying the crystallization of macromolecules will be addressed and discussed in a first part. The still unsolved problems are highlighted. This section also discusses the methodological approaches that can be used. In the second part, some of the recent achievements in the field are presented. We show how physical methods have contributed to a deeper understanding of protein crystallization. Emphasis is given to the parameter microgravity, since the projects concerning crystallizations in this environment have stimulated the physico-chemical research in the field. Finally, the future perspectives are outlined. 相似文献
109.
Jianwei Zheng Fenglin Liao Simson Wu Glenn Jones Tian‐Yi Chen Joshua Fellowes Tim Sudmeier Ian J. McPherson Ian Wilkinson Shik Chi Edman Tsang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17496-17502
There is an exciting possibility to decentralize ammonia synthesis for fertilizer production or energy storage without carbon emission from H2 obtained from renewables at small units operated at lower pressure. However, no suitable catalyst has yet been developed. Ru catalysts are known to be promoted by heavier alkali dopants. Instead of using heavy alkali metals, Li is herein shown to give the highest rate through surface polarisation despite its poorest electron donating ability. This exceptional promotion rate makes Ru–Li catalysts suitable for ammonia synthesis, which outclasses industrial Fe counterparts by at least 195 fold. Akin to enzyme catalysis, it is for the first time shown that Ru–Li catalysts hydrogenate end‐on adsorbed N2 stabilized by Li+ on Ru terrace sites to ammonia in a stepwise manner, in contrast to typical N2 dissociation on stepped sites adopted by Ru–Cs counterparts, giving new insights in activating N2 by metallic catalysts. 相似文献
110.
Ian J. McPherson Tim Sudmeier Joshua P. Fellowes Ian Wilkinson Tim Hughes S. C. Edman Tsang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17594-17602
Molten LiCl and related eutectic electrolytes are known to permit direct electrochemical reduction of N2 to N3? with high efficiency. It had been proposed that this could be coupled with H2 oxidation in an electrolytic cell to produce NH3 at ambient pressure. Here, this proposal is tested in a LiCl–KCl–Li3N cell and is found not to be the case, as the previous assumption of the direct electrochemical oxidation of N3? to NH3 is grossly over‐simplified. We find that Li3N added to the molten electrolyte promotes the spontaneous and simultaneous chemical disproportionation of H2 (H oxidation state 0) into H? (H oxidation state ?1) and H+ in the form of NH2?/NH2?/NH3 (H oxidation state +1) in the absence of applied current, resulting in non‐Faradaic release of NH3. It is further observed that NH2? and NH2? possess their own redox chemistry. However, these spontaneous reactions allow us to propose an alternative, truly catalytic cycle. By adding LiH, rather than Li3N, N2 can be reduced to N3? while stoichiometric amounts of H? are oxidised to H2. The H2 can then react spontaneously with N3? to form NH3, regenerating H? and closing the catalytic cycle. Initial tests show a peak NH3 synthesis rate of 2.4×10?8 mol cm?2 s?1 at a maximum current efficiency of 4.2 %. Isotopic labelling with 15N2 confirms the resulting NH3 is from catalytic N2 reduction. 相似文献