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Molecular Engineering of Metal Alkoxides for Solution Phase Synthesis of High‐Tech Metal Oxide Nanomaterials

Molecular Engineering of Metal Alkoxides for Solution Phase Synthesis of High‐Tech Metal Oxide Nanomaterials

Solution to the problem : Over the last decade, there has been considerable progress in the ‘bottom‐up’ synthesis of functional inorganic nanomaterials with precision at atomic and molecular level. This Minireview illustrates some recent advances on metal alkoxide precursor design and chemical modifications to improve their performance in solution phase and to access high‐performance metal oxides nanomaterials.

Abstract

The ‘bottom‐up’ synthesis of inorganic nanomaterials with precision at the atomic/molecular level offers many opportunities for the design and improvement of the nanomaterials for various applications. Molecular engineering during soft chemical processing for the synthesis of functional nanomaterials enables the desired chemical and physical properties of the precursors, such as solubility or volatility, clean decomposition, control of stoichiometry for multimetallic species to name a few, and leads to easy control of uniform particle size distribution, stoichiometry…. This Minireview illustrates some important aspects of the molecular engineering in light of some recent developments from the molecular synthesis of nanomaterials involving non‐silicon metal alkoxide systems for high‐tech applications.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Shashank Mishra, Stéphane Daniele
doi.org/10.1002/chem.202000534

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Unique β‐Turn Peptoid Structures and Their Application as Asymmetric Catalysts

Unique β‐Turn Peptoid Structures and Their Application as Asymmetric Catalysts

Unique examples of pyrrolidine‐based β‐turn‐like peptoids are described and characterized both in the solid state and in solution. Furthermore, their highly efficient and enantioselective catalytic activity for the production of γ‐nitro aldehydes by asymmetric Michael reaction in water was demonstrated.

Abstract

Peptoids, N‐substituted glycine oligomers, represent an important class of peptidomimetics that can fold into three‐dimensional structures in solution. Most of the folded peptoid structures, however, resemble helices, and this can limit their applications, specifically in asymmetric catalysis. In this work, for the first time, unique examples of pyrrolidine‐based β‐turn‐like peptoids are described and characterized, both in the solid state, by single‐crystal X‐ray analysis, and in solution, by circular dichroism spectroscopy. Furthermore, their highly efficient and enantioselective catalytic activity for the production of γ‐nitro aldehydes by asymmetric Michael reaction in water was demonstrated. The structural properties and DFT‐D3 calculations of the new β‐turn‐like peptoids, as well as catalytic and spectroscopic studies on designed pyrrolidine‐based helical peptoids, suggest that the β‐turn structure plays a key role in the stereoselectivity of the catalytic reaction.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Chandra Mohan Darapaneni, Pritam Ghosh, Totan Ghosh, Galia Maayan
doi.org/10.1002/chem.202000595

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Enantiomerically Pure Tetravalent Neptunium Amidinates: Synthesis and Characterization

Enantiomerically Pure Tetravalent Neptunium Amidinates: Synthesis and Characterization

Enantiomerically pure tetravalent neptunium amidinate complexes possessing unprecedented neptunium–halide bonds have been prepared by salt metathesis and subsequent (pseudo)halide exchange reactions. Structural characterization in solid state (SC‐XRD) and in solution (NMR) showed the preservation of the chirality‐at‐metal throughout the series of heteroleptic fluoro, chloro, bromo, and azido complexes. More information can be found in the Communication by J. März et al. (DOI: doi.org/10.1002/chem.20200186510.1002/chem.202001865).

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Sebastian Fichter, Sebastian Kaufmann, Peter Kaden, Tobias S. Brunner, Thorsten Stumpf, Peter W. Roesky, Juliane März
doi.org/10.1002/chem.202003032

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Long‐Lived Photocharges in Supramolecular Polymers of Low‐Band‐Gap Chromophores

Long‐Lived Photocharges in Supramolecular Polymers of Low‐Band‐Gap Chromophores

1D matters ! Low‐band‐gap chromophores that self‐assemble into one‐dimensional helical nanowires show light‐induced formation of polarons with unusual lifetimes exceeding hours. The accumulation of these charge carriers at concentrations close to that of the metal–insulator transition is reflected by profound macroscopic charge‐transport properties and photoconductivity in these confined organic semiconductor systems.

Abstract

Photoinduced charge separation in supramolecular aggregates of π‐conjugated molecules is a fundamental photophysical process and a key criterion for the development of advanced organic electronics materials. Herein, the self‐assembly of low‐band‐gap chromophores into helical one‐dimensional aggregates, due to intermolecular hydrogen bonding, is reported. Chromophores confined in these supramolecular polymers show strong excitonic coupling interactions and give rise to charge‐separated states with unusually long lifetimes of several hours and charge densities of up to 5 mol % after illumination with white light. Two‐contact devices exhibit increased photoconductivity and can even show Ohmic behavior. These findings demonstrate that the confinement of organic semiconductors into one‐dimensional aggregates results in a considerable stabilization of charge carriers for a variety of π‐conjugated systems, which may have implications for the design of future organic electronic materials.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Regina J. Hafner, Daniel Görl, Andrzej Sienkiewicz, Sandor Balog, Holger Frauenrath
doi.org/10.1002/chem.201904561

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Silyl Anion Initiated Hydroboration of Aldehydes and Ketones

Silyl Anion Initiated Hydroboration of Aldehydes and Ketones

Hydroboration catalysts based on environmentally benign and earth abundant main group compounds offer high potential as an alternative to transition‐metal catalysts. Silicon is abundant and has no inherent toxicity, but has found limited use in hydroboration catalysis. In this work, it is shown that a silyl anion is an effective initiator for the hydroboration of carbonyl compounds requiring low catalyst loadings and mild conditions and with good functional group tolerance.

Abstract

Hydroboration is an emerging method for mild and selective reduction of carbonyl compounds. Typically, transition‐metal or reactive main‐group hydride catalysts are used in conjunction with a mild reductant such as pinacolborane. The reactivity of the main‐group catalysts is a consequence of the nucleophilicity of their hydride ligands. Silicon hydrides are significantly less reactive and are therefore not efficient hydroboration catalysts. Here, a readily prepared silyl anion is reported to be an effective initiator for the reduction of aldehydes and ketones requiring mild conditions, low catalyst loadings and with a good substrate scope. The silyl anion it is shown to activate HBpin to generate a reactive borohydride in situ which reacts with aldehydes and ketones to afford the hydroboration product.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Martin W. Stanford, Alessandro Bismuto, Michael J. Cowley
doi.org/10.1002/chem.202000897

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Hexayne Amphiphiles and Bolaamphiphiles

Hexayne Amphiphiles and Bolaamphiphiles

Surfactants worth the sacrifice : Amphiphilic and bolaamphiphilic functional hexaynes were synthesized using the Egliton–Galbraith reaction and a sacrificial monomer. The novel carbon‐rich surfactants form aggregates in water, monolayers on surfaces, and stabilize the liquid–liquid interface.

Abstract

Oligoynes with two or more conjugated carbon–carbon triple bonds are useful precursors for carbon‐rich nanomaterials. However, their range of applications has so far been severely limited by the challenging syntheses, particularly in the case of oligoynes with functional groups. Here, we report a universal synthetic approach towards both symmetric and unsymmetric, functionalized hexaynes through the use of a modified Eglinton–Galbraith coupling and a sacrificial building block. We demonstrate the versatility of this approach by preparing hexaynes functionalized with phosphonic acid, carboxylic acid, ammonium, or thiol head groups, which serve as neutral, cationogenic, or anionogenic interfacially active groups. We show that these hexaynes are carbon‐rich amphiphiles or bolaamphiphiles that self‐assemble at liquid–liquid interfaces, on solid surfaces, as well as in aqueous media.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Enzo Bomal, Vincent Croué, Reuben Yeo, Rosario Scopelliti, Holger Frauenrath
doi.org/10.1002/chem.201904890

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Solar‐Assisted eBiorefinery: Photoelectrochemical Pairing of Oxyfunctionalization and Hydrogenation Reactions

Solar‐Assisted eBiorefinery: Photoelectrochemical Pairing of Oxyfunctionalization and Hydrogenation Reactions

A biocatalytic photoelectrochemical platform for solar‐assisted dual biotransformations is constructed by wiring a Mo‐doped BiVO4 photocathode and a hierarchical porous ITO electrode. The deliberate integration of enzymatic redox processes into the photoelectrochemical cell simultaneously facilitates peroxygenase‐ and ene‐reductase‐mediated enantioselective synthesis of high‐value chemicals using solar‐powered electrons and water.

Abstract

Inspired by natural photosynthesis, biocatalytic photoelectrochemical (PEC) platforms are gaining prominence for the conversion of solar energy into useful chemicals by combining redox biocatalysis and photoelectrocatalysis. Herein, we report a dual biocatalytic PEC platform consisting of a molybdenum (Mo)‐doped BiVO4 (Mo:BiVO4) photoanode and an inverse opal ITO (IO‐ITO) cathode that gives rise to the coupling of peroxygenase and ene‐reductase‐mediated catalysis, respectively. In the PEC cell, the photoexcited electrons generated from the Mo:BiVO4 are transferred to the IO‐ITO and regenerate reduced flavin mononucleotides to drive ene‐reductase‐catalyzed trans‐hydrogenation of ketoisophrone to (R )‐levodione. Meanwhile, the photoactivated Mo:BiVO4 evolves H2O2 in situ via a two‐electron water‐oxidation process with the aid of an applied bias, which simultaneously supplies peroxygenases to drive selective hydroxylation of ethylbenzene into enantiopure (R )‐1‐phenyl‐1‐hydroxyethane. Thus, the deliberate integration of PEC systems with redox biocatalytic reactions can simultaneously produce valuable chemicals on both electrodes using solar‐powered electrons and water.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Da Som Choi, Jinhyun Kim, Frank Hollmann, Chan Beum Park
doi.org/10.1002/anie.202006893

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Covalent Assembly of MoS2 Nanosheets with SnS Nanodots as Linkages for Lithium/Sodium‐Ion Batteries

Covalent Assembly of MoS2 Nanosheets with SnS Nanodots as Linkages for Lithium/Sodium‐Ion Batteries

Nanosheets meet nanodots : A novel covalent assembly strategy is proposed for MoS2 nanosheets to realize unique MoS2/SnS hollow super‐assemblies by using SnS nanodots as covalent linkages. The strategy enables effective across‐interlayer electron transfer, facilitated ion diffusion kinetics, and high mechanical stability for high‐performance electrochemical lithium/sodium storage.

Abstract

Weak van der Waals interactions between interlayers of two‐dimensional layered materials result in disabled across‐interlayer electron transfer and poor layered structural stability, seriously deteriorating their performance in energy applications. Herein, we propose a novel covalent assembly strategy for MoS2 nanosheets to realize unique MoS2/SnS hollow superassemblies (HSs) by using SnS nanodots as covalent linkages. The covalent assembly based on all‐inorganic and carbon‐free concept enables effective across‐interlayer electron transfer, facilitated ion diffusion kinetics, and outstanding mechanical stability, which are evidenced by experimental characterization, DFT calculations, and mechanical simulations. Consequently, the MoS2/SnS HSs exhibit superb rate performance and long cycling stability in lithium‐ion batteries, representing the best comprehensive performance in carbon‐free MoS2‐based anodes to date. Moreover, the MoS2/SnS HSs also show excellent sodium storage performance in sodium‐ion batteries.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jiajia Ru, Ting He, Binjie Chen, Yutong Feng, Lianhai Zu, Zhijun Wang, Qiaobao Zhang, Tianzi Hao, Ruijin Meng, Renchao Che, Chi Zhang, Jinhu Yang
doi.org/10.1002/anie.202005840

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d–d Dative Bonding Between Iron and the Alkaline‐Earth Metals Calcium, Strontium, and Barium

d–d Dative Bonding Between Iron and the Alkaline‐Earth Metals Calcium, Strontium, and Barium

To d or not to d : Ferrocene complexes of Ca, Sr, and Ba show clear evidence for Fe⋅⋅⋅metal bonding while no such interaction is present in the Mg complex. Analysis with the QTAIM and EDA‐NOCV methods points to Fe→Ae bonds that involve vacant d‐orbitals of alkaline‐earth metals.

Abstract

Double deprotonation of the diamine 1,1′‐(t BuCH2NH)‐ferrocene (1 ‐H2) by alkaline‐earth (Ae) or EuII metal reagents gave the complexes 1 ‐Ae (Ae=Mg, Ca, Sr, Ba) and 1 ‐Eu. 1 ‐Mg crystallized as a monomer while the heavier complexes crystallized as dimers. The Fe⋅⋅⋅Mg distance in 1 ‐Mg is too long for a bonding interaction, but short Fe⋅⋅⋅Ae distances in 1 ‐Ca, 1 ‐Sr, and 1 ‐Ba clearly support intramolecular Fe⋅⋅⋅Ae bonding. Further evidence for interactions is provided by a tilting of the Cp rings and the related 1H NMR chemical‐shift difference between the Cp α and β protons. While electrochemical studies are complicated by complex decomposition, UV/Vis spectral features of the complexes support Fe→Ae dative bonding. A comprehensive bonding analysis of all 1 ‐Ae complexes shows that the heavier species 1 ‐Ca, 1 ‐Sr, and 1 ‐Ba possess genuine Fe→Ae bonds which involve vacant d‐orbitals of the alkaline‐earth atoms and partially filled d‐orbitals on Fe. In 1 ‐Mg, a weak Fe→Mg donation into vacant p‐orbitals of the Mg atom is observed.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Philipp Stegner, Christian Färber, Jan Oetzel, Ulrich Siemeling, Michael Wiesinger, Jens Langer, Sudip Pan, Nicole Holzmann, Gernot Frenking, Uta Albold, Biprajit Sarkar, Sjoerd Harder
doi.org/10.1002/anie.202005774

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Partially Pyrolyzed Binary Metal–Organic Framework Nanosheets for Efficient Electrochemical Hydrogen Peroxide Synthesis

Partially Pyrolyzed Binary Metal–Organic Framework Nanosheets for Efficient Electrochemical Hydrogen Peroxide Synthesis

A new class of partially pyrolyzed NiFe metal–organic framework nanosheets (MOF NSs) was created for the electrochemical synthesis of H2O2 by two‐electron oxygen reduction reaction (ORR) for the first time. The optimized MOF NSs‐300 exhibits the highest activity for ORR with near‐zero overpotential and excellent H2O2 selectivity (ca. 99 %) in 0.1 m KOH, outperforming most electrocatalysts reported to date.

Abstract

Herein, we developed a partially controlled pyrolysis strategy to create evenly distributed NiO nanoparticles within NiFe‐MOF nanosheets (MOF NSs) for electrochemical synthesis of H2O2 by a two‐electron oxygen reduction reaction (ORR). The elemental Ni can be partially transformed to NiO and uniformly distributed on the surface of the MOF NSs, which is crucial for the formation of the particular structure. The optimized MOF NSs‐300 exhibits the highest activity for ORR with near‐zero overpotential and excellent H2O2 selectivity (ca. 99 %) in 0.1 m KOH solution. A high‐yield H2O2 production rate of 6.5 mol gcat−1 h−1 has also been achieved by MOF NSs‐300 in 0.1 m KOH and at 0.6 V (vs. RHE). In contrast to completely pyrolyzed products, the enhanced catalytic activities of partially pyrolyzed MOF NSs‐300 originates mainly from the retained MOF structure and the newly generated NiO nanoparticles, forming the coordinatively unsaturated Ni atoms and tuning the performance towards electrochemical H2O2 synthesis.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Mengjun Wang, Nan Zhang, Yonggang Feng, Zhiwei Hu, Qi Shao, Xiaoqing Huang
doi.org/10.1002/anie.202006422

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Reversibly Switching the Charge State and Adsorption Location of A Single Potassium Atom on Ultrathin CuO Films

Reversibly Switching the Charge State and Adsorption Location of A Single Potassium Atom on Ultrathin CuO Films

The switch : Combined XPS, STM, and local work function measurements verify that the charge states and locations of potassium species on monolayered CuO films can be reversibly switched by polarity‐reversed STM bias voltage pulses.

Abstract

Potassium (K) cations are spontaneously formed upon thermal deposition of low‐coverage K onto an ultrathin CuO monolayer grown on Cu(110) and they were explored by low‐temperature scanning tunneling microscopy (STM) and X‐ray photoemission spectroscopy. The formed K cations are highly immobile and thermally stable. The local work function around an individual K cation decreases by 1.5±0.3 eV, and a charging zone underneath it is established within about 1.0 nm. The cationic and neutral states of the K atom are switchable upon application of an STM bias voltage pulse, which is simultaneously accompanied by an adsorption site relocation.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zhantao Peng, Bin Di, Wentao Li, Dan Liu, Xiaojie Wen, Hao Zhu, Huanjun Song, Yajie Zhang, Cen Yin, Xiong Zhou, Kai Wu
doi.org/10.1002/anie.202005370

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The Rb7Bi3−3xSb3xCl16 Family: A Fully Inorganic Solid Solution with Room‐Temperature Luminescent Members

The Rb7Bi3−3xSb3xCl16 Family: A Fully Inorganic Solid Solution with Room‐Temperature Luminescent Members

The Rb7Sb3Cl16 phase , comprised of isolated octahedra and edge‐shared dimers, demonstrates photoluminescence centered at 560 nm with a quantum yield of 3.8 % at 296 K (99.4 % at 77 K) and a specific temperature sensitivity above 0.06 K−1 at 300 K. Utilizing DFT and chemical substitution with Bi3+ in the Rb7Bi3−3x Sb3x Cl16 (x ≤1) family, the [Sb2Cl10]4− dimer is presented as a design principle for Sb‐based luminescent materials.

Abstract

Low‐dimensional ns2‐metal halide compounds have received immense attention for applications in solid‐state lighting, optical thermometry and thermography, and scintillation. However, these are based primarily on the combination of organic cations with toxic Pb2+ or unstable Sn2+, and a stable inorganic luminescent material has yet to be found. Here, the zero‐dimensional Rb7Sb3Cl16 phase, comprised of isolated [SbCl6]3− octahedra and edge‐sharing [Sb2Cl10]4− dimers, shows room‐temperature photoluminescence (RT PL) centered at 560 nm with a quantum yield of 3.8±0.2 % at 296 K (99.4 % at 77 K). The temperature‐dependent PL lifetime rivals that of previous low‐dimensional materials with a specific temperature sensitivity above 0.06 K−1 at RT, making it an excellent thermometric material. Utilizing both DFT and chemical substitution with Bi3+ in the Rb7Bi3−3x Sb3x Cl16 (x ≤1) family, we present the edge‐shared [Sb2Cl10]4− dimer as a design principle for Sb‐based luminescent materials.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Bogdan M. Benin, Kyle M. McCall, Michael Wörle, Viktoriia Morad, Marcel Aebli, Sergii Yakunin, Yevhen Shynkarenko, Maksym V. Kovalenko
doi.org/10.1002/anie.202003822

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Exploration of the Fluoride Reactivity of Aryltrifluoroborate on Selective Cleavage of Diphenylmethylsilyl Groups

Exploration of the Fluoride Reactivity of Aryltrifluoroborate on Selective Cleavage of Diphenylmethylsilyl Groups

The unique fluoride reactivity of phenyltrifluoroborate in the desilylation of diphenylmethylsilyl groups is controlled by substituents on the benzene ring. The fluorine on trifluoroborate interacts with silicon and activates the Si–O bond to enable selective desilylation of the diphenylmethylsilyl group. Selective desilylation of a primary silyl ether in the presence of a secondary silyl ether by the trifluoroborate was also successful.

The first known report on the fluoride catalytic reactivity of potassium aryltrifluoroborate is described. The fluoride reactivity of phenyltrifluoroborate was controlled by substituents on the trifluoroborate‐attached benzene, such as the methoxy group at the para‐position and the methyl group at the ortho‐position. In addition, the selective aryltrifluoroborate‐catalyzed cleavage of the diphenylmethylsilyl group was achieved.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Katsumasa Fujiki, Katsunori Tanaka
onlinelibrary.wiley.com/doi/abs/10.1002/ejoc.202000707

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Synthesis of Two Epimers of Pseudopaline

Synthesis of Two Epimers of Pseudopaline

Pseudopaline is an opine metal chelator recently identified in Pseudomonas aeruginosa. This metallophore plays an important role in bacterial development during infections, providing a route for the acquirement of essential micronutrients (Zn2+ and Mn2+) in metal scarce environments. Herein, a straightforward synthetic approach for the synthesis of two epimers of pseudopaline and the attribution of their absolute configurations is presented.

Opines are a known group of compounds characterized by an elevated polarity. Recently, two new members of this class, staphylopine and pseudopaline, have been identified in Staphylococcus aureus and Pseudomonas aeruginosa , respectively. These molecules are metal chelators that contribute to the growth of bacteria in particularly metal‐poor environment. Different evidences suggest that these molecules might have an important role in the development of pulmonary infections in humans. Considering the impact of P. aeruginosa infections in cystic fibrosis patients (prevalence up to 70 %), pseudopaline has risen interest as potential source of new therapeutic intervention. We present herein a straightforward synthetic approach for the synthesis of the two epimers of pseudopaline. Starting from a chiral building block, we attribute the absolute configuration to the two obtained diasteroisomers.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Gregorio Cullia, Roberto Fanelli, Romé Voulhoux, Pascal Arnoux, Florine Cavelier
onlinelibrary.wiley.com/doi/abs/10.1002/ejoc.202000278

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TMSOTf-Promoted Intermolecular Cascade Reaction of Aromatic Diazo Ketones with Olefins: Selective Synthesis of 3-Arylethylideneoxindoles

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The Journal of Organic Chemistry

The Journal of Organic Chemistry: Latest Articles (ACS Publications)
Authors: Madhu Babu Tatina†, Wang Xinzhu†, Mardi Santoso‡, Ziad Moussa§, and Zaher M. A. Judeh*†
feedproxy.google.com/~r/acs/joceah/~3/fUXqn5JV9GQ/acs.joc.0c01076

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Photoresponsive Dithienylethene-Containing Tris(8-hydroxyquinolinato)aluminum(III) Complexes with Photocontrollable Electron-Transporting Properties for Solution-Processable Optical and Organic Resistive Memory Devices

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Cheok-Lam Wong, Maggie Ng, Eugene Yau-Hin Hong, Yi-Chun Wong, Mei-Yee Chan, and Vivian Wing-Wah Yam*
feedproxy.google.com/~r/acs/jacsat/~3/MvJdgZB9ZNA/jacs.0c03057

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Dynamic Evolution of Solid–Liquid Electrochemical Interfaces over Single-Atom Active Sites

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Hui Su†, Wanlin Zhou†, Hui Zhang†, Wu Zhou‡, Xu Zhao†, Yuanli Li†, Meihuan Liu†, Weiren Cheng*†, and Qinghua Liu*†
feedproxy.google.com/~r/acs/jacsat/~3/UWoi-2UwRGs/jacs.0c04231

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