Latest ArticlesBoth sulfur and fluorine play important roles in organic synthesis, the life science, and materials science. The direct incorporation of these elements into organic scaffolds with precise control of the oxidation states of sulfur moieties is of great significance. Herein, we report the highly selective electrochemical vicinal fluorosulfenylation and fluorosulfoxidation reactions of alkenes, which were enabled by the unique ability of electrochemistry to dial in the potentials on demand. Preliminary mechanistic investigations revealed that the fluorosulfenylation reaction proceeded through a radical-polar crossover mechanism involving a key episulfonium ion intermediate. Subsequent electrochemical oxidation of fluorosulfides to fluorosulfoxides were readily achieved under a higher applied potential with the adventitious H2O in the reaction mixture.
Water-caused luminescence quenching is a well-known and intractable issue for luminescence lanthanide complexes, greatly confining their broad application as sensing and displaying devices in water system. Herein, an anionic and coordination-saturated lanthanide complex with a nanosheet-like structure has been prepared. It exhibits excellent photophysical properties both in solid state and in aqueous suspension. Noteworthily, a 13% improvement for sensitization efficiency from organic ligand to central lanthanide ion has been realized, indicating an exceptional phenomenon of water-induced luminescence improvement which is rarely reported previously. Moreover, the aqueous suspension of as-prepared luminophore could act as a chemo-sensor responding to various organic solvents in water. Both of water-induced luminescence improvement and extended sensing behavior in this work provide a new platform for developing highly performant and practical luminescent materials in the water system.
Carbon nanotube-based (CNT-based) interfacial evaporation material is one of the most potential materials for solar desalination. Here, we studied the evaporation rate of the CNT-based membranes with different hydrophilic and hydrophobic chemical modified surfaces using molecular dynamic simulations. We found that the hydrogen bonding density among water molecules at the interface is a key factor in enhancing the evaporation rate. For a hydrophilic CNT-based membrane, the strong interactions between the membrane outer surface and the water molecules can destroy the water-water hydrogen bonding interactions at the interface, resulting in the reduction of the hydrogen bonding density, leading to an enhancement effect in evaporation rate. We also found that there is an optimal thickness for evaporation membrane. These findings could provide some theoretical guidance for designing and exploring advanced CNT-based systems with more beneficial performance in water desalination.
Metal skeletons, such as Nickel Foam (NF) has attracted worldwide interests as stable host for lithium metal anode because of its high stability, large specific surface area and high conductivity. However, most metal skeletons have lithophobic surface and uneven current distribution that result in sporadic lithium nucleation and uncontrolled dendrites growth. Herein, we describe a sequential immersing strategy to generate interwoven Nickel(Ⅱ)-dimethylglyoxime (Ni-DMG) nanowires at NF to obtain composite skeleton (NDNF), which can be used as an stable host for Li metal storage. The Ni-DMG has proved effective to realize uniform lithium nucleation and dendrite-free lithium deposition. Combing with the three dimensional (3D) hierarchical porous structure, the composite host shows a significantly improved coulombic efficiency (CE) than pristine commercial nickel foam. Moreover, the corresponding Li||Li symmetrical cells can run more than 700 h with low voltage hysteresis 22 mV at 1.0 mA/cm2, and Li@NDNF||LiFePO4 full-cell exhibits a high capacity retention of 82.03% at 1.0 C during 630 cycles. These results proved the effectiveness of metal-organic complexes in governing Li metal growth and can be employed as a new strategy for dendrite-free Li metal anode and safe Li metal batteries (LMBs).
Pharmaceutical salt formation is the most preferred and effective method to enhance the physicochemical properties of APIs. The aim of the study was to design and synthesize a series of new salts to improve the solubility of Imatinib (IM). Two stable salts with malonic acid (S1) and citric acid (S5), one metastable salt with fumaric acid (S2), two unstable salts with citric acid (S3, S4) were obtained for the first time. Single crystal and powder X-ray diffraction, Fourier transform infrared, differential scanning calorimetry, and thermogravimetric analysis were used to characterize the novel salts. The solubility and stability of the solid were also evaluated, and three salts (S1, S2, S5) had a more than 20 folds of solubility and a faster dissolution rate improved as compared to the pure drug in water and pH 6.8 buffer, respectively.
The synthesis of high-value multi-carbon products through the electrochemical reduction of carbon monoxide (COER) is one of the promising avenues for carbon utilization and energy storage, in which searching for efficient electrocatalysts that exhibit moderate CO intermediate binding strength and low kinetic barrier for C-C coupling is a key issue. Herein, by means of comprehensive density functional theory (DFT) computations, we theoretically designed three synergistic coupling catalysts by co-doping transition metal (TM = Fe, Co and Ni) and boron (B) into the two-dimensional black phosphorene (BP), namely TM-B@BP for COER to C2 products. DFT computations and ab initio molecular dynamics simulations reveal the good stability and high feasibility of these proposed TM-B@BP catalysts for practical applications and future experimental synthesis. More interestingly, high-value ethylene (C2H4), ethane (C2H6) and ethanol (C2H5OH) products can be obtained on these three designed electrocatalysts with ultra-small limiting potentials (−0.20~−0.41 V) and low kinetic energy barriers of C-C coupling (0.52~0.91 eV). Meanwhile, the competitive one-carbon (C1) products and hydrogen evolution reaction can also be effectively suppressed. The promising activity and selectivity of these three designed electrocatalysts render them ideal candidates for CO electroreduction, thus providing a cost-effective opportunity to achieve a sustainable production of high value C2 chemicals and fuels.
Conventional gels manifest monotonous swelling or shrinking performance upon immersing in solvents until reaching an equilibrium state. Recently, we discovered that the "hydrophobic hydrogels" prepared from hydrophobic polymer networks demonstrated dynamic swelling performance without equilibrium states. Upon water immersion, the gels expanded tremendously at the first stage until reaching a swelling peak; subsequently, the gels shrunk at an extremely slow rate. While this phenomenon endows the material with an unusual feature, more efforts are highly demanding for the full understanding of this performance. Herein, we systematically investigate the hydrophobic hydrogels' swelling kinetics by screening the organic solvent dependence, polymer effect, and temperature impact. It is revealed that the chemical structure of gels greatly influences the swelling kinetics. The higher the networks' hydrophobicity, the slower the swelling kinetics. Meanwhile, organic solvents demonstrate a limited effect on the dynamic swelling performance. Moreover, higher temperature significantly accelerates the whole volume change process. Based on the swelling performance, we further develop hydrogel-based soft devices with time-programmable two-dimensional and three-dimensional shape-shifting performances.
We report the first disubstituted hetero-ten-vertex closo cluster [(CrGe9)Cr2(CO)13]4- with three adjacent Cr(CO)n units adopting both η5 and η1 coordination modes, which was synthesized through the reaction of "KGe1.67" with (MeCN)3Cr(CO)3 and Cr(CO)6 in ethylenediamine (en) solution. In contrast to the η1-Cr atoms forming localized two-center two-elelctron (2c-2e) Cr-Ge bonds, the hetero atom η5-Cr exhibits versatile bonding mechanisms including three 5c-2e and five 8c-2e delocalized bonds which account for Hückel aromaticity. Intricate multi-center bonding patterns delineate the multiple local σ-aromatic characters of the title cluster displaying explicit spherical aromaticity.
Herein, we presented a novel biodegradable copolymer via the chain extending reaction of poly(p-dioxanone)-co-poly(2-(2-hydroxyethoxy) benzoate) (PPDO-co-PDHB) prepolymer with hexamethylene diisocyanate (HDI) as a chain extender. The structures and molecular weight of PPDO-co-PDHB prepolymer and PPDO-co-PDHB-PU chain-extended copolymer are characterized via hydrogen nuclear magnetic resonance spectroscopy (1H NMR) and viscosity test. The relationship between the molecular structures and properties of the chain-extended copolymers is established. The PPDO-co-PDHB-PU copolymers possess a better thermal stability comparing with the PPDO homopolymer. The study of mechanical properties shows that the elongation-at-break of PPDO-co-PDHB-PU is much higher than that of PPDO. The investigation of hydrolytic degradation behaviors indicates the degradation rate of PPDO can be controlled by adjusting the PDHB compositions, and proves that chain-extended copolymers exhibit an excellent hydrolytic stability being better than that of PPDO.
Designing highly efficient non-precious based electrocatalysts for oxygen reduction reaction (ORR) is of significance for the rapid development of metal-air batteries. Herein, a hydrothermal-pyrolysis method is employed to fabricate Fe, N co-doped porous carbon materials as effective ORR electrocatalyst through adopting graphitic carbon nitride (g-C3N4) as both the self-sacrificial templates and N sources. The g-C3N4 provides a high concentration of unsaturated pyridine-type N to coordinate with iron to form Fe-N active sites. Through adjusting the Fe doping amounts, it is proved that appropriate Fe doping content is conducive to the construction of abundant defects and active sites of Fe-N. The as-prepared catalyst exhibits superior electrocatalytic ORR performance in alkaline media with half-wave potential (E1/2 = 0.82 V) and onset potential (Eonset = 0.95 V), equivalent to the commercial Pt/C catalyst. Moreover, there is almost no activity loss after 10 k continuous cyclic voltammetry cycles and methanol tolerance, indicating the excellent durability and superior methanol tolerance. Remarkably, when assembled as the cathode in a Zn-air battery, the device displays a power density of 99 mW/cm2, an open-circuit potential of 1.48 V and long-term discharge-charge cycling stability, indicating the promising potential to substitute the Pt catalyst for practical application.
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