Ionogels of a Sugar Surfactant in Ionic Liquids

Green and environmentally friendly ionogels formed by a sugar surfactant were prepared in two kinds of imidazolium‐based ionic liquids. The phase transition from ribbon structures to lamellar structures induced by temperature and the transition mechanism were investigated in detail by means of freeze‐fracture TEM and field‐emission SEM observations, as well as small‐angle X‐ray scattering measurements. The rheological properties and tribological properties of two kinds of ionogels were systematically investigated. The difference in the lubricating properties and antiwear capability can be explained well by the mechanical and viscoelastic properties, as well as the different microstructures of samples destroyed by shear forces. This work provides a better understanding of the relationship between the structures, rheological properties, and tribological properties of ionogels.     

Photochemical reactions of electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine via photoinduced electron-transfer

Photoinduced electron transfer reactions of several electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine (TMB) in acetonitrile solution have been studied by using laser flash photolysis technique and steady-state fluorescence quenching method. Laser pulse excitation of TMB yields ³TMB* after rapid intersystem crossing from ¹TMB*. The triplet which located at 480 nm is found to undergo fast quenching with the electron acceptors fumaronitrile (FN), dimethyl fumarate (DMF), diethyl fumarate (DEF), cinnamonitrile (CN), -acetoxyacrylonitrile (AAN), crotononitrile (CrN) and 3-methoxyacrylonitrile (MAN). Substituents binding to olefin molecule own different electron-donating/withdrawing powers, which determine the electron-deficient property (π-cloud density) of olefin molecule as well as control the electron transfer rate constant directly. The detection of ion radical intermediates in the photolysis reactions confirms the proposed electron transfer mechanism, as expected from thermodynamics. The quenching rate constants of triplet TMB by these olefins have been determined at 510 nm to avoid the disturbance of formed TMB cation radical around 475 nm. All the values approach or reach to the diffusion-controlled limit. In addition, fluorescence quenching rate constants have been also obtained by calculating with Stern–Volmer equation. A correlation between experimental electron transfer rate constants and free energy changes has been explained by Marcus theory of adiabatic outer-sphere electron transfer. Disharmonic k_q values for CN and CrN in endergonic region may be the disturbance of exciplexs formation.     

Synthesis of a lignin-based surfactant through amination,sulfonation, and acylation

A simple and effective chemical method based on Mannich reaction, sulfonation, and acylation was adopted to anchor the hydrophilic sulfonic groups and lipophilic long carbon chains onto alkaline lignin. The obtained products were characterized by Fourier transform infrared spectroscopy (FTIR) and elemental analysis, and the surface activity was evaluated by interfacial tension, which was determined by a maximum bubble pressure method. The results demonstrated that the ASAL showed high surface activity in comparison to lignosulfonate and the interfacial tension reached 5.0 (10^?3?N?·?m^?1) when the mass fraction of ASAL was 5%, in agreement with the properties of good surfactants.**     

Effect of the support on cobalt carbide catalysts for sustainable production of olefins from syngas

Co₂C-based catalysts with SiO₂, γ-Al₂O₃, and carbon nanotubes (CNTs) as support materials were prepared and evaluated for the Fischer-Tropsch to olefin (FTO) reaction. The combination of catalytic performance and structure characterization indicates that the cobalt-support interaction has a great influence on the Co₂C morphology and catalytic performance. The CNT support facilitates the formation of a CoMn composite oxide during calcination, and Co₂C nanoprisms were observed in the spent catalysts, resulting in a product distribution that greatly deviates from the classical Anderson-Schulz-Flory (ASF) distribution, where only 2.4 C% methane was generated. The Co₃O₄ phase for SiO₂- and γ-Al₂O₃-supported catalysts was observed in the calcined sample. After reduction, CoO, MnO, and low-valence CoMn composite oxide were generated in the γ-Al₂O₃-supported sample, and both Co₂C nanospheres and nanoprisms were identified in the corresponding spent catalyst. However, only separated phases of CoO and MnO were found in the reduced sample supported by SiO₂, and Co₂C nanospheres were detected in the spent catalyst without the evidence of any Co₂C nanoprisms. The Co₂C nanospheres led to a relatively high methane selectivity of 5.8 C% and 12.0 C% of the γ-Al₂O₃- and SiO₂-supported catalysts, respectively. These results suggest that a relatively weak cobalt-support interaction is necessary for the formation of the CoMn composite oxide during calcination, which benefits the formation of Co₂C nanoprisms with promising catalytic performance for the sustainable production of olefins via syngas.     

Selective Capture of Toxic Selenite Anions by Bismuth‐based Metal–Organic Frameworks

Chemically durable and effective absorbent materials for selenite (SeO₃^2?) remain highly desirable for contamination remediation. Now a bismuth‐based metal–organic framework (Bi‐MOF, CAU‐17) was used as adsorbent to capture SeO₃^2? anions from aqueous solution with ultrahigh adsorption capacity of 255.3 mg g^?1 and fast kinetics. Furthermore, the adsorbent showed excellent selectivity for SeO₃^2? and was able to work steadily in a broad pH range of 4–11. Density functional theory (DFT) calculation, XANES modeling, and EXAFS fitting suggested that SeO₃^2? anions were immobilized by forming Bi?O?Se bonds (T‐3 structural model) though splitting the O?Bi?O bond in the crystal structure, leading to a structural transformation of CAU‐17 in the solid state.     

Decoupling Hydrogen and Oxygen Production in Acidic Water Electrolysis Using a Polytriphenylamine‐Based Battery Electrode

Hydrogen production through water splitting is considered a promising approach for solar energy harvesting. However, the variable and intermittent nature of solar energy and the co‐production of H₂ and O₂ significantly reduce the flexibility of this approach, increasing the costs of its use in practical applications. Herein, using the reversible n‐type doping/de‐doping reaction of the solid‐state polytriphenylamine‐based battery electrode, we decouple the H₂ and O₂ production in acid water electrolysis. In this architecture, the H₂ and O₂ production occur at different times, which eliminates the issue of gas mixing and adapts to the variable and intermittent nature of solar energy, facilitating the conversion of solar energy to hydrogen (STH). Furthermore, for the first time, we demonstrate a membrane‐free solar water splitting through commercial photovoltaics and the decoupled acid water electrolysis, which potentially paves the way for a new approach for solar water splitting.     

Central Doping of a Foreign Atom into the Silver Cluster for Catalytic Conversion of CO2 toward C−C Bond Formation

Clusters with an exact number of atoms are of particular interest in catalysis. Their catalytic behaviors can be potentially altered with the addition or removal of a single atom. Now the effects of doping with a single foreign atom (Au, Pd, and Pt) into the core of an Ag cluster with 25 atoms on the catalytic properties are explored, where the foreign atom is protected by 24 Ag atoms (Au@Ag₂₄, Pd@Ag₂₄, and Pt@Ag₂₄). The central doping of a single atom into the Ag₂₅ cluster has a substantial influence on the catalytic performance in the carboxylation reaction of CO₂ with terminal alkyne through C?C bond formation to produce propiolic acid. These studies reveal that the catalytic properties of the cluster catalysts can be dramatically changed with the subtle alteration by a single atom away from the active sites.     

Solid-phase extraction of aflatoxins using a nanosorbent consisting of a magnetized nanoporous carbon core coated with a molecularly imprinted polymer

A core consisting of nanoporous carbon (MNPC) and magnetized with Co₃O₄ was coated with a molecularly imprinted polymer (MIP) by atom transfer radical precipitation polymerization. Ethyl 3-coumarincarboxylate was used as a pseudo-template to give a MIP that has a fairly specific recognition capability for aflatoxins. Batch rebinding studies were carried out to determine the specific adsorption equilibrium and specific recognition. Extraction is achieved in a single step by mixing and vortexing the sample extract with the Co-MNPC@MIP. The loaded nanosorbent was then magnetically separated and eluted with acetonitrile/water (6/4, v/v). The aflatoxins were then quantified by HPLC. Under optimal conditions, the detection limits for aflatoxins typically are 0.05–0.07 ng mL^?1, recoveries from spiked corn are found to be 75.1 to 99.4%, and relative standard deviations range from 1.7 to 5.1 (n =?6).

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Graphical abstract Poly(methacrylic acid) was imprinted with the pseudo-template ethyl 3-coumarincarboxylate by atom transfer radical precipitation polymerization on the surface of cobalt-derived magnetic nanoporous carbon (Co-MNPC). This nanosorbent was used for the magnetic solid phase extraction of aflatoxins, followed by HPLC analysis.

     

Determination of DNA based on fluorescence quenching of terbium doped carbon dots

This work describes the preparation of carbon dots doped with terbium(III) (Tb-CDs) via a hydrothermal method, starting from terbium ion and ethylenediamine. The size, composition and spectral properties of the Tb-CDs were characterized by transmission electron microscopy, infrared spectra, and fluorescence spectra. The results show that doping of the CDs with Tb(III) reduces the particle size and results in more uniform particles, while fluorescence (at excitation/emission peaks of 380/475 nm) is strongly enhanced. The interaction between Tb-CDs and ct-DNA results in fluorescence quenching of Tb-CDs. The findings were exploited to design a quenchometric method for the determination of ct-DNA. The signal drops linearly in the 80 ng·mL^?1 to 50 μg·mL^?1 ct-DNA concentration range, and the detection limit is 53 ng·mL^?1. The method was applied to the determination of ct-DNA in spiked samples and gave satisfactory results. The possible fluorescence quenching mechanism (which is mainly static) was investigated using the Stern–Volmer equation and thermodynamic equations.

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Graphical abstract A kind of carbon dots doped with terbium(III) (Tb-CDs) were prepared via a hydrothermal method, using terbium ion and ethylenediamine as precursor. Doping with Tb(III) reduced the particle size of CDs and results in uniform particle size and stronger fluorescence. The interaction between the Tb-CDs and dsDNA results in quenching of the fluorescence of Tb-CDs and can be applied to determination of dsDNA.

     

Selective and facile synthesis of α,β-unsaturated nitriles and amides with N-hydroxyphthalimide as the nitrogen source

The direct conversion of α,β-unsaturated aldehydes to corresponding nitriles promoted by Pd(OAc)₂ and phthalic acid which was hydrolyzed from N-hydroxyphthalimide (NHPI) has been disclosed. Additionally, it was found that when water was used as the solvent, α,β-unsaturated amides was obtained as the main products in good to excellent yields. It was first reported that NHPI was utilized as the nitrogen source to synthesize α,β-unsaturated nitriles and amides from aldehydes. Control experiment demonstrated that aldehydes undergo a process of oximation and dehydration to form nitriles and amides.