A highly efficient kinetic resolution of racemic amino alcohols has been achieved for the first time with a chiral tin catalyst. A chiral organotin compound with 3,4,5‐trifluorophenyl groups at the ...3,3′‐positions of the binaphthyl framework enabled this transformation with excellent yield and high enantioselectivity. The process tolerates aryl‐ and alkyl‐substituted amino alcohols and a variety of other substrates, affording the corresponding products in high enantioselectivity and with s factors up to >500.
A valuable structural motif in many biologically active compounds, the vicinal amino alcohol unit can be obtained in optically active form by kinetic resolution of the racemate. A chiral organotin complex catalyzes this reaction, which is thought to proceed via a stannylene N,O‐aminal intermediate.
We report a robust synthesis of Ag@Au core–shell nanocubes by directly depositing Au atoms on the surfaces of Ag nanocubes as conformal, ultrathin shells. Our success relies on the introduction of a ...strong reducing agent to compete with and thereby block the galvanic replacement between Ag and HAuCl4. An ultrathin Au shell of 0.6 nm thick was able to protect the Ag in the core in an oxidative environment. Significantly, the core–shell nanocubes exhibited surface plasmonic properties essentially identical to those of the original Ag nanocubes, while the SERS activity showed a 5.4-fold further enhancement owing to an improvement in chemical enhancement. The combination of excellent SERS activity and chemical stability may enable a variety of new applications.
Sodium–air batteries (SABs) have attracted wide attention in the chemistry society owing to their high energy density, abundant precursor sources, inexpensive materials and reduced manufacture costs, ...and environmental benignity. This review summarizes the research and progress of the rechargeable SABs based on nonaqueous and aqueous electrolytes. The effects of gas atmosphere, environmental pressure, catalysts, and architectures of the electrodes on the distribution and morphology of discharge products in SABs are also included. The complex and rich sodium electrochemistry of air electrodes is presented, and many electrochemical reaction mechanisms based on the structure design of air electrodes with various catalysts and electrolytes are also summarized. They involve the reversible formation/decomposition reactions of NaO2, Na2O2, Na2CO3, NaHCO3, Na2C2O4, and NaOH. It is a great challenge to seek for highly efficient electrocatalysts, and more stable and less volatile electrolytes to improve the cyclability of nonaqueous SABs. Internal resistance of the cell could be efficiently improved by developing solid electrolytes with high ion conductivity and optimizing the structures of the cells for the high power density of aqueous SABs. How to effectively control the growth and decomposition of discharged products at three‐phase boundary reaction zones by the integration of highly stable electrolytes and optimization of air electrodes is the next challenge urgently needing to be addressed; only then can we realize practical high performance nonaqueous SABs for daily use.
The reaction mechanism of nonaqueous SABs: The morphology and composition of discharge products are closely related to electrolytes, catalysts, and gas atmosphere (O2, CO2, H2O) for sodium–air batteries (SABs). The sodium electrochemical reaction mechanisms with air in nonaqueous SABs involve the reversible formation/decomposition reactions of cubic NaO2, nanosheet or nanofilm Na2O2, Na2CO3, NaHCO3, and Na2C2O4 and NaOH.
ABSTRACT
Magnetostratigraphy of sedimentary rock deposited in the Chaka basin (north‐eastern Tibetan Plateau) indicates a late Miocene onset of basin formation and subsequent development of the ...adjacent Qinghai Nan Shan. Sedimentation in the basin initiated at ∼11 Ma. In the lower part of the basin fill, a coarsening‐upward sequence starting at ∼9 Ma, as well as rapid sedimentation rates, and northward paleocurrents, are consistent with continued growth of the Ela Shan to the south. In the upper section, several lines of evidence suggest that thrust faulting and topographic development of the Qinghai Nan Shan began at ∼6.1 Ma. Paleocurrent indicators, preserved in the basin in the proximal footwall of the Qinghai Nan Shan, show a change from northward to southward flow between 6.5 and 3.8 Ma. At the same location, sediment derived from the Qinghai Nan Shan appears at 6.1 Ma. Finally, the initiation of progressively shallowing dips observed in deformed basin strata and a change to pebbly, fluvial deposits at 6.1 Ma provide a minimum age for the onset of slip on the thrust fault that dips north‐east beneath the Qinghai Nan Shan. We interpret a decrease in sediment accumulation rates since ∼6 Ma to indicate a reduction in Chaka basin accommodation space due to active faulting and folding along the Qinghai Nan Shan and incorporation of the basin into the wedge‐top depozone. Declination anomalies indicate the beginning of counter‐clockwise rotation since 6.1 Ma, which we associate with local deformation, not regional block rotation. The emergence of the Qinghai Nan Shan near the end of the Miocene Epoch partitioned the once contiguous Chaka‐Gonghe and Qinghai basin complex. In a regional framework, our study adds to a growing body of evidence that points to widespread initiation and/or reactivation of fault networks during the late Miocene across the north‐eastern Tibetan Plateau.
Recent studies of the northeastern part of the Tibetan Plateau have called attention to two emerging views of how the Tibetan Plateau has grown. First, deformation in northern Tibet began essentially ...at the time of collision with India, not 10–20 Myr later as might be expected if the locus of activity migrated northward as India penetrated the rest of Eurasia. Thus, the north‐south dimensions of the Tibetan Plateau were set mainly by differences in lithospheric strength, with strong lithosphere beneath India and the Tarim and Qaidam basins steadily encroaching on one another as the region between them, the present‐day Tibetan Plateau, deformed, and its north‐south dimension became narrower. Second, abundant evidence calls for acceleration of deformation, including the formation of new faults, in northeastern Tibet since ~15 Ma and a less precisely dated change in orientation of crustal shortening since ~20 Ma. This reorientation of crustal shortening and roughly concurrent outward growth of high terrain, which swings from NNE‐SSW in northern Tibet to more NE‐SW and even ENE‐WSW in the easternmost part of northeastern Tibet, are likely to be, in part, a consequence of crustal thickening within the high Tibetan Plateau reaching a limit, and the locus of continued shortening then migrating to the northeastern and eastern flanks. These changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation.
Key Points
The north‐south limits of Tibet were set by lateral variations in strength
Roughly 15 million years ago, deformation of NE Tibet accelerated
Since 20–15 million years ago, the orientation of shortening rotated eastward
The intercalation compounds with various electrochemically active or inactive elements in the layered structure have been the subject of increasing interest due to their high capacities, good ...reversibility, simple structures, and ease of synthesis. However, their reversible intercalation/deintercalation redox chemistries in previous compounds involve a single cationic redox reaction or a cumulative cationic and anionic redox reaction. Here we report an anionic redox chemistry and structural stabilization of layered sodium chromium sulfide. It was discovered that the sulfur in sodium chromium sulfide is electrochemically active, undergoing oxidation/reduction rather than chromium. Significantly, sodium ions can successfully move out and into without changing its lattice parameter c, which is explained in terms of the occurrence of chromium/sodium vacancy antisite during desodiation and sodiation processes. Our present work not only enriches the electrochemistry of layered intercalation compounds, but also extends the scope of investigation on high-capacity electrodes.The rational design of intercalation electrodes is largely confined to the optimization of redox chemistry of transition metals and oxygen. Here, the authors report the single anionic redox process in NaCrS
where it is sulfur rather than chromium that works as the electrochemical active species.
A highly efficient and selective heterogeneous photocatalytic system for nitro reduction to amino organics was established using CdS, Ni2P and Na2S/Na2SO3 as a photosensitizer, a cocatalyst and a ...sacrificial electron donor in aqueous solution, respectively. Two competing pathways for photocatalytic H2 production and nitro reduction were found. Also, the reduction of nitroarenes to aniline was confirmed to proceed through both the direct and condensation routes.
Drought is a major threat to plant growth and crop productivity. Calcium-dependent protein kinases (CDPKs, CPKs) are believed to play important roles in plant responses to drought stress. Here, we ...report that Arabidopsis thaliana CPK8 functions in abscisic acid (ABA)- and Ca2+-mediated plant responses to drought stress. The cpk8 mutant was more sensitive to drought stress than wild-type plants, while the transgenic plants overexpressing CPK8 showed enhanced tolerance to drought stress compared with wild-type plants. ABA-, H2O2-, and Ca2+-induced stomatal closing were impaired in cpk8 mutants. Arabidopsis CATALASE3 (CAT3) was identified as a CPK8-interacting protein, confirmed by yeast two-hybrid, coimmunoprecipitation, and bimolecular fluorescence complementation assays. CPK8 can phosphorylate CAT3 at Ser-261 and regulate its activity. Both cpk8 and cat3 plants showed lower catalase activity and higher accumulation of H2O2 compared with wild-type plants. The cat3 mutant displayed a similar drought stress-sensitive phenotype as cpk8 mutant. Moreover, ABA and Ca2+ inhibition of inward K+ currents were diminished in guard cells of cpk8 and cat3 mutants. Together, these results demonstrated that CPK8 functions in ABA-mediated stomatal regulation in responses to drought stress through regulation of CAT3 activity.
The Bohai and Yellow seas are marginal seas of the western North Pacific, characterized by coastal eutrophication and populated coastlines. In this work, six survey datasets collected between 2011 ...and 2018 were used to investigate the excess of dissolved inorganic nitrogen (DIN) related to soluble reactive phosphorus (SRP), referred to as N*, in the Bohai and Yellow seas. High N* of more than 5 μmol kg−1 occurred mostly in the Changjiang and Yellow River plumes and/or near the Jiangsu coast. Away from these river plumes and the Jiangsu coast, however, N* usually ranged from −2.5 to 1.0 μmol kg−1. Combining our field data and previously published data, we found that N* in the Bohai and Yellow seas increased in the 1990s and 2000s, likely caused by the combined effect of atmospheric nitrogen deposition increase and the Kuroshio N* rise. In the 2010s, however, the coastal N* increases stopped. Based on a N*-budgeting approach, marine N (either from in situ decomposition of marine organic matters or from the open seas via current inputs) and non-marine N (either from riverine inputs or from local atmospheric nitrogen deposition) were distinguished. Marine N accounted for 51% ± 38% of DIN in the Bohai Sea and 67% ± 37% of DIN in the Yellow Sea. Although this is a regional study, we suggest that accumulation of atmospheric nitrogen along oceanic circulation pathways dominates the decadal evolution of coastal eutrophication. These findings and new insights may improve management of eutrophication in these two important marginal seas, and will also improve our understanding of nutrient dynamics in other marine systems.
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•Marine N accounts for 51% of the Bohai Sea DIN and 67% of the Yellow Sea DIN.•Oceanic transport of atmospherically deposited N enhances coastal eutrophication.•Increases in excess nitrogen in the Bohai and Yellow seas stopped in the 2010s.
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