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991.
目的运用火焰原子吸收光谱法测定中药草珊瑚叶中的Fe、Zn、Mg、Ca、Cu 5种金属元素的含量。方法用浓HNO3-HCl O4消解样品,采用标准曲线法测定其5种金属元素含量。结果所测的样品中含有丰富的人体必需微量元素。方法回收率在99.35%-103.30%之间,样品相对偏差小于5%。结论该法简单、准确,结果令人满意。 相似文献
992.
Dr. Mégane Muschi Anusha Lalitha Dr. Saad Sene Dr. Damien Aureau Dr. Mathieu Fregnaux Dr. Imène Esteve Dr. Lucie Rivier Dr. Naseem Ramsahye Dr. Sabine Devautour-Vinot Dr. Clémence Sicard Prof. Nicolas Menguy Dr. Christian Serre Prof. Guillaume Maurin Prof. Nathalie Steunou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10439-10444
An innovative strategy is proposed to synthesize single-crystal nanowires (NWs) of the Al3+ dicarboxylate MIL-69(Al) MOF by using graphene oxide nanoscrolls as structure-directing agents. MIL-69(Al) NWs with an average diameter of 70±20 nm and lengths up to 2 μm were found to preferentially grow along the [001] crystallographic direction. Advanced characterization methods (electron diffraction, TEM, STEM-HAADF, SEM, XPS) and molecular modeling revealed the mechanism of formation of MIL-69(Al) NWs involving size-confinement and templating effects. The formation of MIL-69(Al) seeds and the self-scroll of GO sheets followed by the anisotropic growth of MIL-69(Al) crystals are mediated by specific GO sheets/MOF interactions. This study delivers an unprecedented approach to control the design of 1D MOF nanostructures and superstructures. 相似文献
993.
Peilin Deng Fan Yang Zhitong Wang Shenghua Chen Yinzheng Zhou Shahid Zaman Prof. Dr. Bao Yu Xia 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10899-10905
Carbon dioxide (CO2) conversion is promising in alleviating the excessive CO2 level and simultaneously producing valuables. This work reports the preparation of carbon nanorods encapsulated bismuth oxides for the efficient CO2 electroconversion toward formate production. This resultant catalyst exhibits a small onset potential of −0.28 V vs. RHE and partial current density of over 200 mA cm−2 with a stable and high Faradaic efficiency of 93 % for formate generation in a flow cell configuration. Electrochemical results demonstrate the synergistic effect in the Bi2O3@C promotes the rapid and selective CO2 reduction in which the Bi2O3 is beneficial for improving the reaction kinetics and formate selectivity, while the carbon matrix would be helpful for enhancing the activity and current density of formate production. This work provides effective bismuth-based MOF derivatives for efficient formate production and offers insights in promoting practical CO2 conversion technology. 相似文献
994.
Jialuo Li Shuai Yuan Jun-Sheng Qin Jiandong Pang Peng Zhang Yingmu Zhang Yanyan Huang Hannah F. Drake Wenshe R. Liu Prof. Dr. Hong-Cai Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9405-9409
The controlled synthesis of multicomponent metal–organic frameworks (MOFs) allows for the precise placement of multiple cooperative functional groups within a framework, leading to emergent synergistic effects. Herein, we demonstrate that turn-on fluorescence sensors can be assembled by combining a fluorophore and a recognition moiety within a complex cavity of a multicomponent MOF. An anthracene-based fluorescent linker and a hemicyanine-containing CN−-responsive linker were sequentially installed into the lattice of PCN-700. The selective binding of CN− to hemicyanine inhibited the energy transfer between the two moieties, resulting in a fluorescence turn-on effect. Taking advantage of the high tunability of the MOF platform, the ratio between anthracene and the hemicyanine moiety could be fine-tuned in order to maximize the sensitivity of the overall framework. The optimized MOF-sensor had a CN−-detection limit of 0.05 μm , which is much lower than traditional CN− fluorescent sensors (about 0.2 μm ). 相似文献
995.
Dr. Chun-Chao Hou Dr. Lianli Zou Dr. Liming Sun Dr. Kexin Zhang Dr. Zheng Liu Prof. Yinwei Li Dr. Caixia Li Prof. Ruqiang Zou Prof. Jihong Yu Prof. Qiang Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(19):7454-7459
Single-atom catalysts have drawn great attention, especially in electrocatalysis. However, most of previous works focus on the enhanced catalytic properties via improving metal loading. Engineering morphologies of catalysts to facilitate mass transport through catalyst layers, thus increasing the utilization of each active site, is regarded as an appealing way for enhanced performance. Herein, we design an overhang-eave structure decorated with isolated single-atom iron sites via a silica-mediated MOF-templated approach for oxygen reduction reaction (ORR) catalysis. This catalyst demonstrates superior ORR performance in both alkaline and acidic electrolytes, comparable to the state-of-the-art Pt/C catalyst and superior to most precious-metal-free catalysts reported to date. This activity originates from its edge-rich structure, having more three-phase boundaries with enhanced mass transport of reactants to accessible single-atom iron sites (increasing the utilization of active sites), which verifies the practicability of such a synthetic approach. 相似文献
996.
Huijun Yang Zhi Chang Dr. Yu Qiao Han Deng Xiaowei Mu Prof. Ping He Prof. Haoshen Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9463-9467
Rechargeable aqueous zinc batteries (RAZB) have been re-evaluated because of the superiority in addressing safety and cost concerns. Nonetheless, the limited lifespan arising from dendritic electrodeposition of metallic Zn hinders their further development. Herein, a metal–organic framework (MOF) was constructed as front surface layer to maintain a super-saturated electrolyte layer on the Zn anode. Raman spectroscopy indicated that the highly coordinated ion complexes migrating through the MOF channels were different from the solvation structure in bulk electrolyte. Benefiting from the unique super-saturated front surface, symmetric Zn cells survived up to 3000 hours at 0.5 mA cm−2, near 55-times that of bare Zn anodes. Moreover, aqueous MnO2–Zn batteries delivered a reversible capacity of 180.3 mAh g−1 and maintained a high capacity retention of 88.9 % after 600 cycles with MnO2 mass loading up to 4.2 mg cm−2. 相似文献
997.
Dr. Lu Jin Fangyuan Cheng Hao Li Prof. Dr. Kui Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8976-8980
Porous tantalum nitride (Ta3N5) single crystals, combining structural coherence and porous microstructure, would substantially improve the photoelectrochemical performance. The structural coherence would reduce the recombination of charge carriers and maintain excellent transport properties while the porous microstructure would not only reduce photon scattering but also facilitate surface reactions. Here, we grow bulk-porous Ta3N5 single crystals on a two-centimeter scale with (002), (023), and (041) facets, respectively, and show significantly enhanced photoelectrochemical performance. We show the preferential facet growth of porous crystals in a lattice reconstruction strategy in relation to lattice match and lattice channel. We present the facet engineering to enhance light absorption, exciton lifetime and transport properties. The porous Ta3N5 single crystal boosts photoelectrochemical oxidation of alcohols with the (002) facet showing the highest performance of >99 % alcohol conversion and >99 % aldehyde/ketone selectivity. 相似文献
998.
Houfu Lv Dr. Tianfu Liu Dr. Xiaomin Zhang Dr. Yuefeng Song Hiroaki Matsumoto Prof. Dr. Na Ta Chaobin Zeng Prof. Dr. Guoxiong Wang Prof. Dr. Xinhe Bao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16102-16107
In situ exsolution of metal nanoparticles in perovskite under reducing atmosphere is employed to generate a highly active metal–oxide interface for CO2 electrolysis in a solid oxide electrolysis cell. Atomic-scale insight is provided into the exsolution of CoFe alloy nanoparticles in La0.4Sr0.6Co0.2Fe0.7Mo0.1O3−δ (LSCFM) by in situ scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy and DFT calculations. The doped Mo atoms occupy B sites of LSCFM, which increases the segregation energy of Co and Fe ions at B sites and improves the structural stability of LSCFM under a reducing atmosphere. In situ STEM measurements visualized sequential exsolution of Co and Fe ions, formation of CoFe alloy nanoparticles, and reversible exsolution and dissolution of CoFe alloy nanoparticles in LSCFM. The metal–oxide interface improves CO2 adsorption and activation, showing a higher CO2 electrolysis performance than the LSCFM counterparts. 相似文献
999.
Chen Zhao Dr. Gui-Liang Xu Dr. Tianshou Zhao Dr. Khalil Amine 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17787-17793
Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li-S) batteries. However, the sluggish S redox kinetics, especially under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li-S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm−2) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm−2) with a low electrolyte/sulfur ratio (10 μL mg−1). This research further demonstrates a durable Li-Se/S pouch cell with high specific capacity, validating the potential practical applications. 相似文献
1000.
Dr. Pengfei Cheng Lu Feng Prof. Dr. Yuefeng Liu Dr. Daoyuan Zheng Youbao Sang Wenyuan Zhao Dr. Yang Yang Dr. Songqiu Yang Prof. Dr. Donghui Wei Prof. Dr. Guoxiong Wang Prof. Dr. Keli Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21598-21602
All-inorganic zero-dimensional (0D) metal halides have recently received increasing attention due to their excellent photoluminescence (PL) performance and high stability. Herein, we present the successful doping of copper(I) into 0D Cs2ZnBr4. The incorporating of Cu+ cations enables the originally weakly luminescent Cs2ZnBr4 to exhibit an efficient blue emission centered at around 465 nm, with a high photoluminescence quantum yield (PLQY) of 65.3 %. Detailed spectral characterizations, including ultrafast transient absorption (TA) techniques, were carried out to investigate the effect of Cu+ dopants and the origin of blue emission in Cs2ZnBr4:Cu. To further study the role of the A-site cation and halogen, A2ZnCl4:Cu (A=Cs, Rb) were also synthesized and found to generate intense sky-blue emission (PLQY≈73.1 %). This work represents an effective strategy for the development of environmentally friendly, low-cost and high-efficiency blue-emitting 0D all-inorganic metal halides. 相似文献