Latest ArticlesTo prevent polysulfides from dissolution into electrolyte, we propose a novel and simple approach to nitrogen-doped carbon foams which contain hierarchically porous structure and are decorated with zinc nanodots through one-pot carbonization and activation process. These carbon foams, which serve as hosts for sulfur in lithium battery, can provide a conducting network and shorter diffusion length for Li-ions. Specially, the zinc nanodots derived from the carbothermal reaction of ZnCl2 at high temperature can interact with sulfur/polysulfides by strong chemisorption. In addition, the zinc nanodots can also facilitate the conversion reaction between Li2Sx (2 < x < 8) and Li2S/Li2S2. Therefore, Zn@NCFs/S cathode presents high sulfur utility and large capacity.
More and more attentions have been focused on design and synthesis of novel metal-organic framework/graphene oxide (MOF/GO) composites with unique performance. Zirconium-porphyrin MOF (PCN-222) is in-situ synthesis with the existence of GO with −COOH group to artfully fabricate a PCN-222/GO composite. This composite can be employed as functional material to modify the working electrode. Thanks to excellent electrical conductivity of GO, abundant mesoporous channels and numerous Zr(Ⅳ) metal sites of PCN-222, this composite can immobilize a large amount of aptamer through strong π-π stacking interaction and high affinity between phosphate group of aptamer and Zr(Ⅳ) site of PCN-222 simultaneously. Hence, an ultra-sensitive electrochemical aptasensor based on PCN-222/GO composite can quantificationally detect trace chloramphenicol with limit of detection of 7.04 pg/mL (21.79 pmol/L) from 0.01 ng/mL to 50 ng/mL by electrochemical impedance spectroscopy even in real samples. Meanwhile, this fabricated aptasensor reveals good repeatability, outstanding selectivity and preferable long-term storage. This research provides a useful approach to construct MOF/GO composites for fabricating electrochemical aptasensors in the electrochemical detection field.
Supramolecular assemblies constructed through the encapsulation of conductive polymers (CPs) by macrocyclic molecules have attracted increasing interest in the fields of supramolecular chemistry and electrochemistry. In this work, an effective strategy was reported to improve the stability and conductivity of CPs by electrochemically constructing different supramolecular assemblies composed of macrocycles and CPs. Typically, we uploaded zinc-based MOF (ZIF-8) onto carbon nanotube film (CNTF) and further electrically deposited macrocycles and CPs to gain the flexible conductive electrodes. Herein, five different supramolecular macrocycles, including α-cyclodextrin (α-CD), sulfato-β-cyclodextrin (SCD), sulfonatocalix[4]arene (SC[4]), cucurbit[6]uril (CB[6]) and cucurbit[7]uril (CB[7]) were utilized and the electrochemical performances of the assembly electrodes increased in an order of α-CD < SCD < SC[4] < CB[6] < CB[7], significantly improving the areal capacitance up to 1533 mF/cm2. This strategy may provide a new way for the application of macrocyclic supramolecules in electrochemical systems.
The silicon-based materials are promising candidates for lithium-ion batteries owing to their high energy density. However, achieving long lifespan under realistic conditions remains a challenge because of the volume expansion and low conductivity. In this work, the highly elastic cobweb-like composite materials consisted by SiO and nanofibers are designed and fabricated for high-efficient lithium storage by ball-milling & ; electrostatic spinning method. The reconstructed heterostructure and highly elastic nanofibers can simultaneously increase the conductivity and inhibit the "expansion effect" of silicon-based materials. The constructed electrode of n-SiO/CNF delivers an initial capacity of 1700 mAh/g, and maintains the capacities over 1000 mAh/g after 100 cycles at the current density of 500 mA/g. Meanwhile, this electrode can give an initial coulombic efficiency over 85% and maintains at 98% in the following charge/discharge processes. Furthermore, it exhibits efficient long-term electrochemical performance, maintaining the capacity at about 1000 mAh/g at a high current density of 1000 mA/g after 1000 cycles. This work could provide a promising strategy for enhancing the performance of silicon-based composite materials for practical application in lithium-ion batteries.
We report herein a palladium-catalyzed diarylative dearomatization of indole by employing thioester and arylboronic acid as the aryl electrophiles. The reaction involved a decarbonylation/migratory insertion/terminal Suzuki coupling procedure. Substrates bearing various functional groups are well tolerated in the reaction, affording the diarylated indoline skeletons in moderate to good yields.
We report the fabrication of highly ordered Nb2O5 nanochannel film (Nb2O5-NCF) onto niobium foil by an anodization method. After thermal treatment, the obtained Nb2O5-NCF with rich oxygen vacancies exhibits electrochemical N2 reduction reaction (NRR) activity with an NH3 yield rate of 2.52×10−10 mol cm-2 s-1 and a faradaic efficiency of 9.81% at −0.4 V (vs. RHE) in 0.1 mol/L Na2SO4 electrolyte (pH 3.2). During electrocatalytic NRR, the Nb2O5-NCF takes place electrochromism (EC), along with a crystalline phase transformation from pseudo hexagonal phase to hexagonal phase owing to H+ insertion. This results in the reduced NRR activity due to the decrease of oxygen vacancies of hexagonal phase Nb2O5, which can be readily regenerated by low-temperature thermal treatment or applying an anodic potential, showing superior recycling reproducibility.
Density functional theory calculations have been performed to investigate the dipeptide phosphine-catalyzed hydroamination of enones with pyridazinones. The computations reveal that a number of the NH···O hydrogen-bonding interactions with the pyridazinone moiety and the C-H···O hydrogen-bonding interactions with the enone moiety are present in the enantioselectivity-determining Michael addition transition states. The experimentally-observed catalyst-controlled enantiodivergence is mainly attributed to the significant impact of the substituent of the amide moiety of the dipeptide phosphine on the relative strength of the NH···O hydrogen-bonding interactions, which was found to affect the Si face attack transition state, enabling the enantioselectivity switch upon change of chiral dipeptide phosphine catalyst.
A novel carbon-rich g-C3N4 nanosheets with large surface area was prepared by facile thermal polymerization method using urea and 1, 3, 5-cyclohexanetriol. Plenty of carbon-rich functional groups were introduced into the surface layers of g-C3N4, which constructed the built-in electric field (BIEF) and resulted in improved charge separation; therefore, the carbon-rich g-C3N4 displayed superior photocatalytic activity for amoxicillin degradation under solar light. The contaminant degradation mechanism was proposed based on radical quenching experiments, intermediates analysis and density functional theory (DFT) calculation. Moreover, the reusing experiments showed the high stability of the material, and the amoxicillin degradation under various water matrix parameters indicated its high applicability on pollutants treatment, all of which demonstrated its high engineering application potentials.
Metal nanocrystals have been recognized as the main catalytic materials in many fields, but insufficient activity and stability, as well as high prices, have limited their large-scale potential applications. As one of the extremely promising alternatives toward metal in boosting their catalytic performance, nonmetallic atoms-doped metal nanocrystals have recently received extensive attention because of their high efficiency, chemical and structural durability, abundant reserve, and low cost. In this review, we highlight the most recent progress in this field and provide insights into their catalytic applications. The metal-nonmetal nanocrystals prepared by doping metal nanocrystals with nonmetallic atoms are introduced and classified based on the types of nonmetallic atoms, including metal hydrides, borides, carbides, nitrides, oxides, phosphides, and chalcogenides. Besides, their applications in catalysis, especially in electrocatalysis and organic catalysis, have been summarized and discussed. Finally, the conclusions and perspectives are given for the catalysis-driven rational design of metal-nonmetal nanocrystals in this minireview.
The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment. In this study, amorphous molybdenum sulfide composites (EDTA-MoSx (x=2, 3)) were fabricated via a facile hydrothermal method mediated by EDTA, which was applied to heavy metal ions (Cu2+, Cd2+, Pb2+, Zn2+ and Ni2+) removal from aqueous solutions. A case study for Cu2+ ions showed that the adsorption capacity of EDTA-MoSx (x=2, 3) was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L. Adsorption mechanisms of different sulfide groups and －COOH of EDTA-MoSx (x=2, 3) were verified systematically via a series of experiments, characterizations, and density functional theory (DFT) calculations. Both bridging S22− and －COOH covalently bonded with Cu2+ ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx (x=2, 3). This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.
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