Using detrended cross-correlation analysis (DCCA), we investigate the long-term influence of some factors, specifically precipitation, average temperature and PM10 concentrations on the evolution of ...Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) concentrations in Hong Kong. The 15 years regular monitoring data from two general urban sites, Central/Western District and Tsuen Wan, are analyzed. The results show that the relationships between ambient dioxins and precipitation (or PM10) display long-term cross-correlation at the time scale ranging from one month to one year; while, no cross-correlation with each other have observed in longer temporal scaling regimes (greater than one year). Meantime, differentiated from the previous study, we found that precipitation has the greatest influence on ambient PCDD/PCDFs at the long-term time scaling (about one year) in Hong Kong. And no significant relationships are found between ambient dioxins and average temperature at long-term time scale. These results correspond to atmospheric circulation and regional transport hypothesis and are explained in detail. The long-term cross-correlation property is discussed further, considering the strong influence of the Asian monsoon system.
•Uses detrended cross-correlation analysis to investigate relationships between ambient dioxins and the influential factors.•Crossover locations correspond to atmospheric circulation and regional transport hypothesis.•It shows strong long-term cross-correlation between precipitation and dioxins.•No significant relationships are found between ambient dioxins and average temperature at long-term time scale.
New S in town: Sulfonyl hydrazides smoothly undergo sulfenylation with indoles in the presence of 10 mol % I2 to give structurally diverse indole thioethers in moderate to excellent yields with ...extremely high regioselectivity. This study paves the way for the use of sulfonyl hydrazides as unique sulfur electrophiles in chemical synthesis.
By employing Monte Carlo simulation with the metropolis algorithm, the magnetic properties of hexagonal decorated nanoparticle with a mixed-spin (3/2, 1) configuration under an applied magnetic field ...were analyzed. The influence of exchange couplings and anisotropies on the magnetic and thermodynamic properties of the system were studied. We obtained the various characteristic curves of the magnetization, susceptibility, internal energy, specific heat, and hysteresis loops. The multiple-loop hysteresis behaviors were discovered under certain conditions. Furthermore, we also plotted the variation curve of magnetization with the external magnetic field under the effect of different parameters and found that the magnetization plateaus are based on the exchange couplings, anisotropies, and spin state.
A range of 2,4-dialkylidenetropinone-derived quaternary ammonium salts smoothly reacted with thiols in the presence of tributylamine, delivering structurally diverse thiolated 2,7-disubstituted ...tropones in moderate to excellent yields with high site selectivity. The reaction employs readily available feedstocks and reagents, is free of transition metals, tolerates various functional groups, and can be easily scaled up.
Zinc metal is considered a promising anode material for aqueous zinc ion batteries. However, it suffers from dendrite growth, corrosion, and low coulombic efficiency (CE) during plating/stripping. ...Herein, a concentrated hybrid (4 m Zn(CF3SO3)2 + 2 m LiClO4) aqueous electrolyte (CHAE) to overcome the challenges facing the Zn anode is reported. The developed electrolyte achieves dendrite‐free Zn plating/stripping and obtains an excellent CE of ≈100%, surpassing the previously reported values. The combination of synchrotron‐based in operando transmission X‐ray microscopy, X‐ray diffraction, and ex situ X‐ray photoelectron spectroscopy analyses indicate that the denser, anion‐derived passivation layer formed using the CHAE facilitates homogeneous current distribution and better prevents freshly deposited Zn from directly contacting the electrolyte than the looser, solvent‐derived layers formed from a dilute hybrid aqueous electrolyte (DHAE). The beneficial effects of the CHAE on the compact, dense, and stable salt‐anion‐derived passivation layer can be attributed to its unique solvation structure, which suppresses the water‐related side reactions and widens the electrochemical potential window. In the hybrid Zn||LiFePO4 configuration, the CHAE‐based cell delivered a stable performance of CE >99% and capacity retention >90% after 285 cycles. In contrast, the DHAE‐based cell exhibits capacity retention of <65% after 170 cycles.
A concentrated hybrid aqueous electrolyte (CHAE) (4 m Zn(CF3SO3)2 + 2 m LiClO4) is developed to address the dendrite formation and low coulombic efficiency upon Zn deposition/stripping. The Zn growth behavior and the formation mechanism of dense anion‐derived passivation layer are unveiled by synchrotron‐based in operando imaging and spectroscopy techniques. The CHAE shows excellent cell performance in Zn||LiFePO4 dual‐ion battery.
Anode‐free lithium‐metal batteries employ in situ lithium‐plated current collectors as negative electrodes to afford optimal mass and volumetric energy densities. The main challenges to such ...batteries include their poor cycling stability and the safety issues of the flammable organic electrolytes. Here, a high‐voltage 4.7 V anode‐free lithium‐metal battery is reported, which uses a Cu foil coated with a layer (≈950 nm) of silicon–polyacrylonitrile (Si‐PAN, 25.5 µg cm−2) as the negative electrode, a high‐voltage cobalt‐free LiNi0.5Mn1.5O4 (LNMO) as the positive electrode and a safe, nonflammable ionic liquid electrolyte composed of 4.5 m lithium bis(fluorosulfonyl)imide (LiFSI) salt in N‐methyl‐N‐propyl pyrrolidiniumbis(fluorosulfonyl)imide (Py13FSI) with 1 wt% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as additive. The Si‐PAN coating is found to seed the growth of lithium during charging, and reversibly expand/shrink during lithium plating/stripping over battery cycling. The wide‐voltage‐window electrolyte containing a high concentration of FSI− and TFSI− facilitates the formation of stable solid‐electrolyte interphase, affording a 4.7 V anode‐free Cu@Si‐PAN/LiNi0.5Mn1.5O4 battery with a reversible specific capacity of ≈120 mAh g−1 and high cycling stability (80% capacity retention after 120 cycles). These results represent the first anode‐free Li battery with a high 4.7 V discharge voltage and high safety.
4.7 V Cu@Si‐PAN/LiNi0.5Mn1.5O4 anode‐free Li batteries with a reversible specific capacity of ≈120 mAh g−1 and high capacity retention of 80% after 120 cycles are reported. With the nonflammable F‐rich ionic liquid electrolyte and the seeding Si‐PAN layer (950 nm), an enhanced safety and high‐voltage anode‐free Li battery without dendritic Li growth is demonstrated.
Chinese medicine (CM) is usually prescribed as CM formula to treat disease. The lack of effective research approach makes it difficult to elucidate the molecular mechanisms of CM formula owing to its ...complicated chemical compounds. Network pharmacology is increasingly applied in CM formula research in recent years, which is identified suitable for the study of CM formula. In this review, we summarized the methodology of network pharmacology, including network construction, network analysis and network verification. The aim of constructing a network is to achieve the interaction between the bioactive compounds and targets and the interaction between various targets, and then find out and validate the key nodes via network analysis and network verification. Besides, we reviewed the application in CM formula research, mainly including targets discovery, bioactive compounds screening, toxicity evaluation, mechanism research and quality control research. Finally, we proposed prospective in the future and limitations of network pharmacology, expecting to provide new strategy and thinking on study for CM formula.
A one-pot protocol has been developed for sequential benzyne activation and nucleophilic substitution of enantioenriched tertiary benzylic amines. In the presence of 2-(trimethylsilyl)phenyl ...triflate and CsF, a range of enantioenriched tertiary benzylic amines were substituted by various nucleophiles, delivering structurally diverse benzylic compounds in moderate to excellent yields with excellent retention of enantiopurity. Importantly, this operationally simple protocol permitted formation of various chiral C–S, C–Se, C–C, and C–N bonds with excellent enantiopurity under metal-free conditions.
Display omitted
•Convenient sulfonylation of various organic compounds with sulfonyl hydrazides.•Formation of CS, SN, SF, SCl, SBr, SS, and SSe bonds.•Construction of carbocycles, heterocycles, and ...stereogenic centers.
While sulfonyl hydrazides are widely utilized in organic synthesis, it is only in recent years that they have emerged as powerful sulfonyl sources. The hydrazinyl group can be readily removed from sulfonyl hydrazides under thermal, basic, oxidative, radical, and/or transition metal-catalyzed conditions, and subsequently, the remaining sulfonyl groups are able to form carbon-sulfur, sulfur-nitrogen, sulfur-halogen, sulfur-sulfur, and sulfur-selenium bonds with a wide variety of organic compounds, providing alternative approaches to the preparation of sulfones, sulfonamides, sulfonyl halides, thiosulfonates, and selenosulfonates. Moreover, some of the carbon-sulfur bond-forming reactions have been successfully applied to the construction of carbocycles, heterocycles, and stereogenic centers.
The NH2 group serves as an effective leaving group in the palladium‐catalyzed regioselective and stereospecific title reaction (see scheme). The reaction works well with aryl‐ and alkenylboronic ...acids and aryl‐, alkenyl‐, allyl‐, and benzylboronates, and complete transfer of chirality has been achieved when using α‐chiral primary allylic amines as the allylic electrophiles.
