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321.
The layered double hydroxides (LDHs) of Li and Al can be synthesized from the four polymorphs of Al(OH)3, namely gibbsite, bayerite, nordstrandite, and doyleite. The crystal structure of this class of compounds depends on the type of the precursor used due to their topotactic reaction mechanism. While the LDHs derived from gibbsite and bayerite yield different crystal structures, the incorporation of Li into nordstrandite was expected to yield new LDH structures different from those derived from gibbsite and bayerite. The structure of nordstrandite derived LDHs were however identical to that derived from the bayerite counterpart. The absence of symmetry in the interlayer of nordstrandite (C1) makes it unsuitable to accommodate the intercalating anions with different molecular symmetries. To make the interlayer gallery suitable for the anions, the metal hydroxide layers of the nordstrandite translate, transforming nordstrandite to bayerite. The bayerite with site symmetries Oh and C2 stabilizes the anions in the interlayer by hydrogen bonding. The transformation of nordstrandite to bayerite, when soaked in lithium salt solution is, therefore, a manifestation of the intercalating anions. 相似文献
322.
水滑石(LDHs)是一种阴离子黏土材料,由于其主体层板厚度的可调性,使其在光/电催化、电池、超级电容器、传感器以及生物医药等领域都具有广泛应用。降低层厚至单层可使材料的物理化学性质发生根本改变,从而优化催化性能。近期研究表明,利用自上而下,自下而上的方法,可以实现单层LDHs类材料的合成,但是受限于产量(g级)以及成本设备等问题,目前规模化制备高质量单层LDHs类材料还没有工业案例。成核晶化隔离法是目前唯一规模化合成纳米LDHs的工业化方法,具有成本低,产量可吨级放大等优点。本综述从合成方法、表征手段、应用三个角度讨论了单层及超薄LDHs的精准调控,详细论述了近期关于单层及超薄LDHs合成突破以及LDHs的规模化生产进展,并对其性能进行了总结,为后续设计高性能单层LDHs提供思路。 相似文献
323.
Grégoire C. Gschwend Astrid Olaya Pekka Peljo Hubert H. Girault 《Current Opinion in Electrochemistry》2020
Charge transfer phenomena at the interface between two immiscible electrolyte solutions (ITIES) are electrochemical reactions taking place in soft media. Owing to their liquid nature, the ITIES shows a large panel of electrochemical reactions including electron transfer reactions, ion transfer reactions, coupled electron–ion transfer reactions or biomimetic redox reactions. Nevertheless, the mechanisms by which these reactions proceed are yet to be fully understood. The goal of this short review is to summarise the work accomplished over the past decades towards the elucidation of the structure and reactivity at the ITIES, highlighting the main questions still to be answered. 相似文献
324.
Shuli Tang Heyong Cheng Xin Yan 《Angewandte Chemie (International ed. in English)》2020,59(1):209-214
Reported here is the first on‐demand electrochemical epoxidation incorporated into the standard nano‐electrospray ionization mass spectrometry (nanoESI‐MS) workflow for double‐bond identification. The capability lies in a novel tunable electro‐epoxidation of double bonds, where onset of the reaction can be controlled by simply tuning the spray voltage. On‐demand formation of mono‐/multiple epoxides is achieved at different voltages. The electro‐epoxidized products are then fragmented by tandem MS to generate diagnostic ions, indicating the double bond position(s). The process is completed within seconds, holding great potential for high‐throughput analysis. The rapid switch‐on/off electro‐epoxidation of a single sample, the low sample consumption, the demonstrated applicability to complex lipids containing multiple double bonds, and the advantage of not requiring extra apparatus make this method attractive for use in lipid‐related biological studies. 相似文献
325.
《Journal of Saudi Chemical Society》2020,24(10):715-732
The mechanistic aspects of improved aqueous removal of methyl orange (MO) dyes using high performance novel magnetic MgAlNi barium-ferrite (MgAlNi-BaFe) ternary double layer hydroxide (LDH) nanocomposites is reported in this study. Detailed surface characterization coupled with kinetic, equilibrium, thermodynamics and regeneration studies were undertaken under different operational conditions of temperature (298–318 K), initial concentration (20–100 mg/L), pH (2–6). The kinetic results show that MO sorption was mainly, associated with pseudo-second order and intra-particular diffusion process. The MO adsorption onto the MgAlNi-BaFe nanocomposites suggests a multi-layered sorption process that is endothermic and spontaneous in nature. The MO adsorption mechanism insight taken in cognizance of FTIR, XRD, pKa, zeta potential, the adsorbates surface functional groups and the adsorbate-adsorbent surface charges interactions suggest involvement of hydrogen bonding and n-π interactions, predominantly via physisorption process (ΔG° = −7.406 to −5.69 kJ/mol). The excellent adsorptive performance of the MgAlNi-BaFe adsorbents for removal of MO from water compared with other magnetic LDH nanocomposites was further elucidated via the MgAlNi-BaFe nanomaterials high rates of regeneration and superior performances for three successive desorption-adsorption cycles. This study demonstrates the high potentials of employing MgAlNi-BaFe nanomaterials for removal of dyes from water and wastewater. 相似文献
326.
Zheng Deng Chang‐Jong Kang Mark Croft Wenmin Li Xi Shen Jianfa Zhao Richeng Yu Changqing Jin Gabriel Kotliar Sizhan Liu Trevor A. Tyson Ryan Tappero Martha Greenblatt 《Angewandte Chemie (International ed. in English)》2020,59(21):8240-8246
Given the consensus that pressure improves cation ordering in most of known materials, a discovery of pressure‐induced disordering could require recognition of an order–disorder transition in solid‐state physics/chemistry and geophysics. Double perovskites Y2CoIrO6 and Y2CoRuO6 polymorphs synthesized at 0, 6, and 15 GPa show B‐site ordering, partial ordering, and disordering, respectively, accompanied by lattice compression and crystal structure alteration from monoclinic to orthorhombic symmetry. Correspondingly, the long‐range ferrimagnetic ordering in the B‐site ordered samples are gradually overwhelmed by B‐site disorder. Theoretical calculations suggest that unusual unit‐cell compressions under external pressures unexpectedly stabilize the disordered phases of Y2CoIrO6 and Y2CoRuO6. 相似文献
327.
Principles of Surface Potential Estimation in Mixed Electrolyte Solutions:Taking into Account Dielectric Saturation
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The dielectric properties between in-particle/water interface and bulk solution are significantly different, which are ignored in the theories of surface potential estimation. The analytical expressions of surface potential considering the dielectric saturation were derived in mixed electrolytes based on the nonlinear Poisson-Boltzmann equation. The surface potentials calculated from the approximate analytical and exact numerical solutions agreed with each other for a wide range of surface charge densities and ion concentrations. The effects of dielectric saturation became important for surface charge densities larger than 0.30 C/m\begin{document}$ ^2 $\end{document} . The analytical models of surface potential in different mixed electrolytes were valid based on original Poisson-Boltzmann equation for surface charge densities smaller than 0.30 C/m\begin{document}$ ^2 $\end{document} . The analytical model of surface potential considering the dielectric saturation for low surface charge density can return to the result of classical Poisson-Boltzmann theory. The obtained surface potential in this study can correctly predict the adsorption selectivity between monovalent and bivalent counterions. 相似文献
328.
329.
Vladimír Vrkoslav Barbora Rumlov Timotej Strme Josef Cva
ka 《Journal of separation science》2020,43(13):2579-2588
A new capillary high‐performance liquid chromatography method with atmospheric pressure chemical ionization mass spectrometry was developed for the analysis of fatty acid methyl esters and long‐chain alcohols. The chromatographic separation was achieved using a Zorbax SB‐C18 HPLC column (0.3 × 150 mm, 3.5 μm) with a mobile phase composed of acetonitrile and formic acid and delivered isocratically at a flow rate of 10 μL/min. The column temperature was programmed simply, using a common column oven. Good reproducibility of the temperature profile and retention times were achieved. The temperature programming during the isocratic high‐performance liquid chromatography run had a similar effect as a solvent gradient; it reduced retention times of later eluting analytes and improved their detection limits. Two atmospheric pressure chemical ionization sources of the mass spectrometry detector were compared: an enclosed conventional ion source and an in‐house made ion source with a glass microchip nebulizer. The enclosed source provided better detectability of saturated fatty acid methyl esters and made it possible to determine the double bond positions using acetonitrile‐related adducts, while the open chip‐based source provided better analytical figures of merit for unsaturated fatty acid methyl esters. Temperature‐programmed capillary high‐performance liquid chromatography is a promising method for analyzing neutral lipids in lipidomics and other applications. 相似文献
330.