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71.
Azmi Mohamed Argo Khoirul Anas Suriani Abu Bakar Azira Abd. Aziz Masanobu Sagisaka Paul Brown Julian Eastoe Azlan Kamari Norhayati Hashim Illyas Md Isa 《Colloid and polymer science》2014,292(11):3013-3023
The performance of single-, double- and triple-chain anionic sulphosuccinate surfactants for dispersing multiwall carbon nanotubes (MWNCTs) in natural rubber latex (NR-latex) was studied using a range of techniques, including field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Raman spectroscopy. The conductivities of the nanocomposites were also investigated using four-point probe measurements. Here, MWCNTs were efficiently dispersed in NR-latex with the aid of hyperbranched tri-chain sulphosuccinate anionic surfactants, specifically sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulphonate (TC14). This paper highlights that TC14 performs much better than that of the commercially available surfactant sodium dodecyl sulphate (SDS), demonstrating how careful consideration of surfactant architecture leads to improved dispersibility of MWCNTs in NR-latex. The results should be of significant interest for improving nanowiring applications suitable for aerospace-based technology. 相似文献
72.
Oliver Mahony Sheng Yue Claudia Turdean-Ionescu John V. Hanna Mark E. Smith Peter D. Lee Julian R. Jones 《Journal of Sol-Gel Science and Technology》2014,69(2):288-298
Owing to their diverse range of highly tailorable material properties, inorganic/organic hybrids have the potential to meet the needs of biodegradable porous scaffolds across a range of tissue engineering applications. One such hybrid platform, the silica–gelatin sol–gel system, was examined and developed in this study. These hybrid scaffolds exhibit covalently linked interpenetrating networks of organic and inorganic components, which allows for independent control over their mechanical and degradation properties. A combination of the sol–gel foaming process and freeze drying was used to create an interconnected pore network. The synthesis and processing of the scaffolds has many variables that affect their structure and properties. The focus of this study was to develop a matrix tool that shows the inter-relationship between process variables by correlating the key hybrid material properties with the synthesis parameters that govern them. This was achieved by investigating the effect of the organic (gelatin) molecular weight and collating previously reported data. Control of molecular weight of the polymer is as an avenue that allows the modification of hybrid material properties without changing the surface chemistry of the material, which is a factor that governs the cell and tissue interaction with the scaffold. This presents a significant step forward in understanding the complete potential of the silica–gelatin hybrid system as a medical device. 相似文献
73.
Sergey Miltsov Julian Alonso-Chamarro Mar Puyol 《Journal of heterocyclic chemistry》2020,57(8):3193-3201
New symmetrical and unsymmetrical near-infrared absorbing ketocyanine-type dyes are synthesized and their optical characterization is done. The relationships between their structure and optical properties are discussed. The synthesized ketocyanine dyes show a positive solvatochromism and are poorly fluorescent. A new procedure for the preparation of N,N,N′,N′-tetramethylvinamidinium perchlorate, which was a very useful reagent for the synthesis of various heterocyclic compounds as well as for the preparation of cyanine dyes is developed. 相似文献
74.
Ömer Taspinar Tobias Wilczek Julian Erver Dr. Martin Breugst Dr. Jörg-Martin Neudörfl Prof. Dr. Hans-Günther Schmalz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4256-4260
We report the first chemical synthesis of eurysterol A, a cytotoxic and antifungal marine steroidal sulfate with a unique C8−C19 oxy-bridged cholestane skeleton. After C19 hydroxylation of cholesteryl acetate, used as an inexpensive commercial starting material, the challenging oxidative functionalization of ring B was achieved by two different routes to set up a 5α-hydroxy-7-en-6-one moiety. As a key step, an intramolecular oxa-Michael addition was exploited to close the oxy-bridge (8β,19-epoxy unit). DFT calculations show this reversible transformation being exergonic by about −30 kJ mol−1. Along the optimized (scalable) synthetic sequence, the target natural product was obtained in only 11 steps in 5 % overall yield. In addition, an access to (isomeric) 7β,19-epoxy steroids with a previously unknown pentacyclic ring system was discovered. 相似文献
75.
Florian Ritter Dr. Lukas John Dr. Tobias Schindler Julian P. Schroers Simon Teeuwen Dr. Michael E. Tauchert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(59):13436-13444
The dative Pd→B interaction in a series of RDPBR’ Pd0 and PdII complexes (RDPBR’=(o-PR2C6H4)2BR’, diphosphinoborane) was analyzed using XRD, 11B NMR spectroscopy and NBO/NLMO calculations. The borane acceptor discriminates between the oxidation state PdII and Pd0, stabilizing the latter. Reaction of lithium amides with [(RDPBR’)PdII(4-NO2C6H4)I] chemoselectively yields the C−N coupling product. DFT modelling indicates no significant impact of PdII→B coordination on the inner-sphere reductive elimination rate. 相似文献
76.
Alexander V. Fejzagić Sebastian Myllek Fabian Hogenkamp Julian Greb Prof. Dr. Jörg Pietruszka Dr. Thomas Classen 《ChemistryOpen》2020,9(9):959-966
Screening for an interesting biocatalyst and its subsequent kinetic characterization depends on a reliable activity assay. In this work, a fluorometric assay based on the halogenation of 4-methyl-7-diethylamino-coumarin was established to monitor haloperoxidase-activity. Since haloperoxidases utilize hydrogen peroxide and halide ions to halogenate a broad range of substrates by releasing hypohalous acids, a direct quantification of haloperoxidase-activity remains difficult. With the system presented here, 3-bromo-4-methyl-7-diethylaminocoumarin is preferentially formed and monitored by fluorescence measurements. As starting material and product share similar spectroscopical properties, a two-dimensional calibration ap-proach was utilized to allow for quantification of each compound within a single measurement. To validate the system, the two-dimensional Michaelis-Menten kinetics of a vanadium-dependent chloroperoxidase from Curvularia inaequalis were recorded, yielding the first overall kinetic parameters for this enzyme. With limits of detection and quantification in the low μm range, this assay may provide a reliable alternative system for the quantification of haloperoxidase-activity. 相似文献
77.
Zechao Yang Lukas Fromm Tim Sander Julian Gebhardt Tobias A. Schaub Andreas Grling Milan Kivala Sabine Maier 《Angewandte Chemie (International ed. in English)》2020,59(24):9549-9555
Demonstrated here is a supramolecular approach to fabricate highly ordered monolayered hydrogen‐ and halogen‐bonded graphyne‐like two‐dimensional (2D) materials from triethynyltriazine derivatives on Au(111) and Ag(111). The 2D networks are stabilized by N???H?C(sp) bonds and N???Br?C(sp) bonds to the triazine core. The structural properties and the binding energies of the supramolecular graphynes have been investigated by scanning tunneling microscopy in combination with density‐functional theory calculations. It is revealed that the N???Br?C(sp) bonds lead to significantly stronger bonded networks compared to the hydrogen‐bonded networks. A systematic analysis of the binding energies of triethynyltriazine and triethynylbenzene derivatives further demonstrates that the X3‐synthon, which is commonly observed for bromobenzene derivatives, is weaker than the X6‐synthon for our bromotriethynyl derivatives. 相似文献
78.
Zhenping Wang Qirong Yao Christof Neumann Felix Brrnert Julian Renner Ute Kaiser Andrey Turchanin Harold J. W. Zandvliet Siegfried Eigler 《Angewandte Chemie (International ed. in English)》2020,59(32):13657-13662
The thermal decomposition of graphene oxide (GO) is a complex process at the atomic level and not fully understood. Here, a subclass of GO, oxo‐functionalized graphene (oxo‐G), was used to study its thermal disproportionation. We present the impact of annealing on the electronic properties of a monolayer oxo‐G flake and correlated the chemical composition and topography corrugation by two‐probe transport measurements, XPS, TEM, FTIR and STM. Surprisingly, we found that oxo‐G, processed at 300 °C, displays C?C sp3‐patches and possibly C?O?C bonds, next to graphene domains and holes. It is striking that those C?O?C/C?C sp3‐separated sp2‐patches a few nanometers in diameter possess semiconducting properties with a band gap of about 0.4 eV. We propose that sp3‐patches confine conjugated sp2‐C atoms, which leads to the local semiconductor properties. Accordingly, graphene with sp3‐C in double layer areas is a potential class of semiconductors and a potential target for future chemical modifications. 相似文献
79.
Meccanica - This study concerns the response of a spherical drop, attached to a sinusoidally vibrating wall. Given that the drop is spherical, the model is more realistic than that of a 2D drop... 相似文献
80.
The cooperativity of conformational transitions in strained linear polymer chain was investigated by the method of Brownian dynamics. Deformation of a chain consisting of N=32 and 64 bonds was created by strong external field of dipole type. Correlations are discussed in terms of hazard-plot analysis. 相似文献