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71.
Dr. Xuecheng Chen Dr. Krzysztof Kierzek Karolina Wenelska Krzystof Cendrowski Jiang Gong Dr. Xin Wen Prof. Tao Tang Prof. Paul K. Chu Prof. Ewa Mijowska 《化学:亚洲杂志》2013,8(11):2627-2633
Core–shell‐structured mesoporous silica spheres were prepared by using n‐octadecyltrimethoxysilane (C18TMS) as the surfactant. Hollow mesoporous carbon spheres with controllable diameters were fabricated from core–shell‐structured mesoporous silica sphere templates by chemical vapor deposition (CVD). By controlling the thickness of the silica shell, hollow carbon spheres (HCSs) with different diameters can be obtained. The use of ethylene as the carbon precursor in the CVD process produces the materials in a single step without the need to remove the surfactant. The mechanism of formation and the role played by the surfactant, C18TMS, are investigated. The materials have large potential in double‐layer supercapacitors, and their electrochemical properties were determined. HCSs with thicker mesoporous shells possess a larger surface area, which in turn increases their electrochemical capacitance. The samples prepared at a lower temperature also exhibit increased capacitance as a result of the Brunauer–Emmett–Teller (BET) area and larger pore size. 相似文献
72.
73.
The catalytic oxidative domino degradation of phenols was investigated. Hydrogen peroxide (30% aq.) was used as an oxidant and 2,2′-dinitro-4,4′-ditrifluoromethyldiphenyl diselenide 4e as a catalyst. The products were muconic acid 5, and muconolactones muconolactones—5-carboxymethylfuran-2(5H)-ones 7 and 9. Phenols with alkyl groups at 2 or 4 positions of the benzene ring were converted regioselectively to corresponding muconolactones substituted at alkenylene ring carbon atoms. The reaction mechanism is proposed. 相似文献
74.
The stereoselective synthesis of two epimeric penta-hydroxylated indolizidines was accomplished from 2,3:5,6-di-O-isopropylidene-α-d-mannofuranose and N-(2-methylpent-4-en-2-yl)hydroxylamine. The transformation of these substrates into the corresponding 7-oxa-1-azabicyclo[2.2.1]heptane by the intramolecular 1,3-dipolar cycloaddition was the key step of the synthesis. The adduct was transformed into the tricyclic ammonium salt by intramolecular N-alkylation. The tricyclic ammonium salt was converted to the target compounds by: (route 1) the catalytic hydrogenation; or (route 2) the reaction with sodium azide, followed by the enantioselective reduction of the resulting indolizidinone. 相似文献
75.
Ewa Gniazdowska Przemysław Koźmiński Leon Fuks 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1171-1177
Two types of technetium-99m complexes: (i) with the Hynic ligand linked to Substance P(1–11) and (ii) of the type ‘4 + 1’ consisting of tetradentate tripodal chelator tris(2-mercaptoethyl)-amine and monodentate isocyanide ligand previously coupled with Substance P(1–11), have been prepared on the n.c.a. scale. The obtained conjugates exhibit different lipophilicity and high stability in neutral aqueous solutions, even in the presence of excess concentration of histidine/cysteine competitive standard ligands. The conjugate (99mTc(NS3)(CN))2–SP containing two technetium-99m species in the molecule may be expected to be an extremely good diagnostic radiopharmaceutical. 相似文献
76.
Abstract Liquid crystalline properties of 1 - (4′ - alkoxyphenylamino) - 3 - (4′ - hexyloxyphenyl)-prop-1-en-3-ones, from methoxy to heptadecyloxy, have been examined by optical, DSC, and X-ray methods. The phase diagram for the series exhibits a rich polymorphism of tilted smectic phases, for example, five mesophases were found for the hexyloxy derivative. A characteristic feature of the phase diagram is a gap in the crystal G phase area. For the heptyloxy homologue, a direct crystal H-smectic F phase transition was found; in the case of shorter as well as longer terminal substituents, the phase sequence crystal H–crystal G–smectic F is observed. Calorimetric and X-ray studies revealed the existence of a tricritical point on the crystal G–smectic F transition line. 相似文献
77.
Guan-Yeow Yeap Tze-Nee Chan Wan-Sinn Yam Damian Pociecha Ewa Gorecka 《Liquid crystals》2013,40(9):1041-1047
A new series of non-symmetric chiral isoflavone-based liquid crystalline dimers, α-(2-methylbutyl-4′-(4″-phenyloxy)benzoate)-ω-(3-(4′-decyloxyphenyl)-4H-1-benzopyran-4-one-7-oxy)alkanes, with 3–12 carbon atoms in the alkyloxy spacer, have been synthesised. A pronounced odd–even effect for the phase transition temperatures upon varying the spacer length was observed. The short dimers exhibited monolayer smectic A (SmA) and smectic C (SmC*) phases while for longer homologues a chiral nematic (N*) phase was found. The temperature range of the nematic phase was broadened with elongation of the alkyl spacer. Stabilisation of the nematic phase resulted from competition between the monolayer and intercalated smectic structures. The SmA–SmC* phase transition was second order for all studied compounds with a cross over to the de Vries type behaviour for the shortest homologue. 相似文献
78.
Some symmetrical dimeric compounds containing biphenyl, biphenylcarboxylic acid or benzoiloxyphenyl moieties and polymethylene spacers were synthesised. The mesogenic properties of the synthesised compounds were investigated by optical microscopy, calorimetric and X-ray methods. It was shown that the location and direction of the ester bonds has a crucial significance in mesophase formation. 相似文献
79.
Tomasz Kowalkowski Hlanganani Tutu Leonard Mihaly Cozmuta Miroslav Sprynskyy Ewa M. Cukrowska Bogusław Buszewski 《International journal of environmental analytical chemistry》2013,93(10):797-811
The objectives of this study were to evaluate the mobility of heavy metals (HMs) in two types of soils (acidic forest soil and neutral agricultural soil) by leaching with calcium chloride solution in column experiments. The screening properties of neutral agricultural soil towards pollution by heavy metals (Ni, Cu, Zn and Cd) are approximately 10 times higher than those of acid forest soil. The neutral agricultural soil, polluted artificially by one pore volume (PV) of an HMs solution of concentration 200 mg L?1, can screen the leaching of these metals over several hundreds of years. The higher apparent desorption rate and per cent desorption of HMs (especially Cd) in acid forest soil indicated a higher potential of intensive migration of the metals across the profile and indicated potential risk of Cd pollution for this type of soil. The latest approach of artificial neural networks to describe transport of HMs in soil has been also evaluated. Using a simple three-layer perceptron topology with three hidden neurons, the experimental data could be simulated. The results suggested that the pH of soil is a major factor controlling the retention of the heavy metals in the soils. 相似文献
80.
The synthesis of novel mono- and di(substituted)-1,2,4-triazine derivatives containing thiophene and furan rings are described. Heteroaromatic rings were provided using palladium-catalyzed cross-coupling reaction between 3-alkylsulfanyl-5-acyl-1,2,4-triazines or 5-cyano-3-alkylsulfanyl-1,2,4-triazines and heteroaromatic tin compounds. New compounds bearing masked acyl groups were also obtained. These reactions were optimized to determine the scope and limitations of this methodology and were used for preparation of oligothiophenes bearing terminal heterocyclic ring. 相似文献