Hydrated‐Metal‐Halide‐Based Deep‐Eutectic‐Solvent‐Mediated NiFe Layered Double Hydroxide: An Excellent Electrocatalyst for Urea Electrolysis and Water Splitting

The liquid structures of deep eutectic solvents (DESs) based on hydrated metal halides and their application as electrolytes have been widely studied. However, little attention has been paid to the direct use of this type of DES in the preparation of micro‐/nanomaterials. Herein, an FeCl₃ ? 6 H₂O/urea DES was used in the one‐step synthesis of NiFe‐LDH_D with a nanoflower morphology. In alkaline media, this catalyst promoted excellent electrocatalytic activity for the oxidation of urea at potential of 1.32 V (vs. RHE) and for the oxygen‐evolution reaction at a potential of 1.39 V to achieve a current density of 10 mA cm^?2. These results were superior to the results with NiFe‐LDH/NF that was obtained from an aqueous solution of FeCl₃, as well as most of the previously reported transition‐metal catalysts. Furthermore, NiFe‐LDH_D/NF could be readily implemented as both a cathode and an anode for the electrolysis of urea and water splitting. The use of hydrated‐metal‐halide‐based DESs for the preparation of LDH catalysts through a dipping‐redox strategy should both enrich the research of DESs and offer guidance for the rational surface engineering of catalysts for the electrolysis of urea and overall water splitting with high performance.     

Metal-ligand-coordinated vesicles and vesicle-assisted preparation of calcium oxalate

A Ca(2+) -ligand-coordinated vesicle phase was prepared from a mixture of tetradecyldimethylamine oxide (C14DMAO) and calcium tetradecylamidomethyl sulfate [(CH3(CH2)13NHCOCH2OSO3)2Ca] in aqueous solution. At the appropriate mixing ratios, Ca(2+) -ligand coordination results in the formation of molecular bilayers because Ca(2+) can firmly bind to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca by complexation which reduces the area of head group. In this system, no counterions in aqueous solution exist because of the Ca(2+) -ligand coordination, and the bilayer membranes are not shielded by salts, i.e., a salt-free but charged molecular bilayer. The structures of the birefringent solutions of (CH3(CH2)13NHCOCH2OSO3)2Ca and C14DMAO mixtures were determined by transmission electron microscopy (TEM) images and rheological measurements, demonstrating that the birefringent sample solutions consist of vesicles. The Ca(2+) -ligand complex vesicle phase was used as a microreactor to prepare calcium oxalate (CaC2O4) crystals. Dimethyl oxalate, as a precursor, can hydrolyze to oxalic acid and methanol. Oxalic acid should precipitate Ca(2+) ions binding to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca to produce CaC2O4 crystals (Ca(2+) + H2C2O4 --> CaC2O4 (downward arrow) + 2H+). The obtained particles were CaC2O4 monohydrate, which were dominated by (020) faces. CaC2O4 precipitates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) analysis. After removal of CaC2O4 precipitates, a new cationic and anionic (catanionic) vesicle phase was constructed through electrostatic interaction between cationic C14DMAOH+ (C14DMAO + H+ --> C14DMAOH+) and anionic CH3(CH12)13 NHCOCH2OSO3-.     

In situ hydrothermal synthesis of nanolamellate CaTiO3 with controllable structures and wettability

Nanolamellate structures of CaTiO3 were fabricated by using an in situ hydrothermal synthesis method on titanium for the first time. The number of nanolamellas and the morphology completely or mainly depend on the reaction time and NaOH concentrations, and the wettability of the resulting CaTiO3 surfaces can be successively turned from superhydrophilic to superhydrophobic after modification with a thin layer of hydrophobic silicone, mainly depending on the surface morphology. The proposed formation mechanism of the nanolamellate CaTiO3 structures has also been discussed.     

Fe(CO)5多光子解离和电离动力学

Multiphoton dissociation-ionization dynamics of Fe(CO)_5 were studied mass spectrometrically with a molecular beam and XeCl excimer laser. The results show that Fe(CO)_n~+ (n= 1,2,… ,5) and Fe_2(CO)_4~+ ions are formed mainly via ion-molecule reaction between Fe~+ and Fe(CO)_5 and dissociation following. A “ladder” model of Fe(CO)_5 photodissociation is presented in the paper.     

Bilayer swelling of nonionic surfactant and sodium dodecylsulfate mixed system by refractive-index matching

Bilayer swelling behavior of nonionic and anionic surfactant mixed aqueous solution induced by adding glycerin was studied. The phenomenon were performed on a system, polyethylene glycol ether of tridecyl alcohol with the average number of ethylene oxide of 5 (CH₃(CH₂)₁₂(OCH₂CH₂)₅OH; abbreviation IT5) and SDS mixed aqueous solution, with white cream of the upper phase and micelles (L₁) of the lower phase. White cream containing densely packed multilamellar vesicles was revealed by freeze-fracture transmission electron microscopy and polarized microscope observations. Phase transition from white cream/L₁, two-phase, to clear unique vesicle phase can be induced by adding glycerin to replace water. The addition of glycerin lowers the turbidity of the dispersion and swells the interlamellar distance between bilayers, which could be explained by refractive-index matching between solvent and bilayers.     

Mg-induced vesicles of tetradecyldimethylamine oxide and magnesium dodecyl sulfate

A Mg²⁺-induced vesicle phase was prepared from a mixture of tetradecyldimethylamine oxide (C₁₄DMAO) and magnesium dodecyl sulfate [Mg(DS)₂] in aqueous solution. Study of the phase behavior shows that at the appropriate mixing ratios, Mg²⁺–ligand coordination between C₁₄DMAO and Mg(DS)₂ results in the formation of molecular bilayers, in which Mg²⁺ can firmly bind to the head groups of the two surfactants. The area of the head group can be reduced because of the complexation. In this case, no counterions exist in aqueous solution because of the fixation of Mg²⁺ ions to the bilayer membranes. Therefore, the charges of the bilayer membranes are not shielded by salts. The birefringent solutions of Mg(DS)₂ and C₁₄DMAO mixtures consist of vesicles which were determined by transmission electron microscopy (TEM) images and rheological measurements. Magnesium oxide (MgO) nanoplates were obtained via the decomposition of Mg(OH)₂ which were synthesized in Mg²⁺-induced vesicle phase which was used as the microreactor under the existence of ammonia hydroxide. The morphologies and structures of the obtained MgO nanoplates have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the crystal growth is along the (1 1 1) direction which can be affected by the presence of a vesicle phase having a fixation of Mg²⁺ ions to the bilayer membranes.     

从钒化合物生物效应的多样性看其作用机制*

本文对近年来关于钒化合物不同生物效应机制的研究进展进行了总结,着重于其类胰岛素和抗癌效应的信号转导机制以及两者之间的相关性。同时,基于钒化合物对磷酸转移反应的干预以及对细胞氧化还原状态的调节,讨论了钒化合物多样化的生物效应是否具有一个共同作用机制的可能性,并提出了未来钒化合物研究方向和所面临的挑战。     

Phase behavior, rheological property, and transmutation of vesicles in fluorocarbon and hydrocarbon surfactant mixtures

We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by (19)F NMR as well as (31)P NMR measurements. Upon replacement of NFDA by DEHPA, the signal from the (19)F atoms adjacent to the hydrophilic headgroup disappears and that from the (19)F atoms on the main chain becomes sharper. This could be interpreted as an increase of microfluidity in the mixed vesicle bilayers at higher content of DEHPA, whose alkyl chains are expected to have a lower chain melting point. Our results provide basic knowledge on vesicle formation and their structural evolution in salt-free catanionic surfactant systems containing mixed ion pairs, which may contribute to a deeper understanding of the rules governing the formation and properties of surfactant self-assembly.     

A conjecture of Segre on diophantine approximation

In 1945,B. Segre proved the following classical theorem: Every irrational ξ has an infinity of rational approximationsp/q such that (0) $$\frac{{ - 1}}{{q^2 \sqrt {1 + 4\tau } }}< \frac{p}{q} - \xi< \frac{\tau }{{q^2 \sqrt {1 + 4\tau } }},$$ where τ is any given non-negative real number. Segre conjectured that when τ≠0 and τ^?1 is not an integer, inequalities (0) can be improved by replacing \(\sqrt {1 + 4\tau } \) and \(\sqrt {1 + 4\tau } /\tau \) with larger numbers. In this paper we prove that these two numbers can be replaced with the larger numbers \(\sqrt {1 + 4\tau } + 0.2\tau ^2 \{ \tau ^{ - 1} \} (1 - \{ \tau ^{ - 1} \} )\) and \(\sqrt {1 + 4\tau } /\tau + 0.2\tau ^2 \{ \tau ^{ - 1} \} (1 - \{ \tau ^{ - 1} \} )\) respectively, where {τ^?1} is the fractional part of τ^?1.     

Development of Tough Thermoplastic Elastomers by Leveraging Rigid–Flexible Supramolecular Segment Interplays

Supramolecular interactions facilitate the development of tough multifunctional thermoplastic elastomers. However, the fundamental principles that govern supramolecular toughening are barely understood, and the rational design to achieve the desired high toughness remains daunting. Herein, we report a simple and robust method for toughening thermoplastic elastomers by rationally tailoring hard–soft phase separation structures containing rigid and flexible supramolecular segments. The introduced functional segments with distinct structural rigidities provide mismatched supramolecular interactions to efficiently tune the energy dissipation and bear an external load. The optimal supramolecular elastomer containing aromatic amide and acylsemicarbazide moieties demonstrates a record toughness (1.2 GJ m⁻³), extraordinary crack tolerance (fracture energy 282.5 kJ m⁻²), an ultrahigh true stress at break (2.3 GPa), good elasticity, healing ability, recyclability, and impact resistance. The toughening mechanism is validated by testing various elastomers, confirming the potential for designing and developing super-tough supramolecular materials with promising applications in aerospace and electronics.