Recent advance in electromagnetic shielding of MXenes

As a new type of two-dimensional material,MXene's unique layered structure,outstanding electrical conductivity,low density,tunable surface chemistry,and solution processability make it receive extensive attention in various fields,especially for the lightweight shielding mate rials since the report on electromagnetic interference(EMI) shielding of 2D Ti_3 C_2 T_x in 2016.In this review,the progress on the MXe nes material including their synthetic strategies,prope rties and EMI application is highlighted.First,the recent advance on the different synthesis methods and properties of MXene is summarized.According to their intrinsic characteristics,the application of MXene in EMI fields is then discussed.Finally,the challenges and perspective on the future development of MXene in low-cost preparation and practical application are proposed.     

Cation-intercalated engineering and X-ray absorption spectroscopic characterizations of two dimensional MXenes

The geometrically multiplied development of 2D MXenes has already promoted the prosperity of various fields of scientific researches especially but not limited in energy storage and conversion.Notably,cation intercalation can improve the interlayer spacing of MXenes resulting in tunable physical and chemical properties.Moreover,the synchrotron radiation X-ray characterizations have also shown high potential on exploring the property and structu re of cation intercalated MXe nes.This review is mainly focused on the recent achievements of cation intercalated MXenes through different methods on energy storage systems.Synchrotron-based X-ray absorption spectroscopic characterizations are emphasized to probe the local coordination and electronic structure in intercalated MXenes.The outlook of cation intercalation on MXenes and their applications are also discus sed.     

Diffusion in the presence of periodically spaced permeable membranes

The diffusion of molecules in biological tissues and some other microheterogeneous systems is affected by the presence of permeable barriers. This leads to the slowdown of diffusion at long times as compared to barrier-free diffusion. At short times the effect of barriers is weak. In consequence, the diffusion coefficient D(t) decreases as a function of time. We derive an exact solution for the Laplace transform of D(t) for diffusion in a space separated into layers by equally spaced, parallel identical planes of arbitrary permeability. Additionally, we give an approximation to D(t) which is reasonably accurate over the whole range of the partition permeability from zero (the case of isolated layers) to infinity (the case of no barriers).     

The principle of parametric fractionation (separation) of substances in biological systems and technology

The parametric fractionation (separation) of substances is based on simultaneous exposure of a heterogeneous system with the phases (solid and liquid or liquid and gaseous) including components subject to be separated to the influence of two periodic fields of different nature. One field, “parameter” (for instance, temperature, pH) causes periodical redistribution of the components between phases, and the other field (for instance, mechanical forces, surface tension, electric field) effects synchronous shift of the components of one phase with respect to the other. As a result a counter flow of components to be separated formed against the gradient of their chemical or electrochemical potentials. This method underlain by the general principle of synchronous detection by no means is connected with definite mixtures or sorbents, it operates spontaneously in the inanimate and animate natural systems and can be applied to quite unexpected technologies.     

Simultaneous determination of monoamine transmitters, precursors and metabolites in a single mouse brain

A simple and sensitive procedure for simultaneous determination of monoamine transmitters and related substances including precursors and metabolites has been developed for a single mouse brain. The proposed procedure involves (1) primary butanol extraction, (2) separation of the substances into either acid or alkaline aqueous layers according to their physicochemical properties, and (3) determination by means of high-performance liquid chromatography with electrochemical detection. Three transmitters (noradrenaline, dopamine and 5-hydroxytryptamine) and their precursors (tyrosine, 3,4-dihydroxyphenylalanine and tryptophan) and major metabolites (normethanephrine, 3-methoxy-4-hydroxyphenylethylene glycol, 3-methoxytyramine, 3,4-dihydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenylacetic acid and 5-hydroxyindoleacetic acid) were selectively separated and sensitively detected in mouse whole brain sample. Although 3-methoxy-4-hydroxymandelic acid was also separated from other substances by authentic chromatography, the substance was not detected in mouse brain. Changes in levels of these substances were examined for drugs whose effects had been previously confirmed. These changes reflected putative effects of the drugs and confirmed that the procedure is effective for neurochemical research into the transmitter system.     

二维材料范德华间隙的利用

Since their discovery, two-dimensional (2D) materials have attracted significant research attention owing to their excellent and controllable physical and chemical properties. These materials have emerged rapidly as important material system owing to their unique properties such as electricity, optics, quantum properties, and catalytic properties. 2D materials are mostly bonded by strong ionic or covalent bonds within the layers, and the layers are stacked together by van der Waals forces, thereby making it possible to peel off 2D materials with few or single layers. The weak interaction between the layers of 2D materials also enables the use of van der Waals gaps for regulating the electronic structure of the system and further optimizing the material properties. The introduction of guest atoms can significantly change the interlayer spacing of the original material and coupling strength between the layers. Also, interaction between the guest and host atom also has the potential to change the electronic structure of the original material, thereby affecting the material properties. For example, the electron structure of a host can be modified by interlayer guest atoms, and characteristics such as carrier concentration, optical transmittance, conductivity, and band gap can be tuned. Organic cations intercalated between the layers of 2D materials can produce stable superlattices, which have great potential for developing new electronic and optoelectronic devices. This method enables the modulation of the electrical, magnetic, and optical properties of the original materials, thereby establishing a family of 2D materials with widely adjustable electrical and optical properties. It is also possible to introduce some new properties to the 2D materials, such as magnetic properties and catalytic properties, by the intercalation of guest atoms. Interlayer storage, represented by lithium-ion batteries, is also an important application of 2D van der Waals gap utilization in energy storage, which has also attracted significant research attention. Herein, we review the studies conducted in recent years from the following aspects: (1) changing the layer spacing to change the interlayer coupling; (2) introducing the interaction between guest and host atoms to change the physico-chemical properties of raw materials; (3) introducing the guest substances to obtain new properties; and (4) interlayer energy storage. We systematically describe various interlayer optimization methods of 2D van der Waals gaps and their effects on the physical and chemical properties of synthetic materials, and suggest the direction of further development and utilization of 2D van der Waals gaps.     

Problems of adhesion strength in epoxy-allylic polymer-polymer systems

The main aspects of the problems associated with adhesion and adhesion strength, as well as the factors causing formation of boundary layers (BLs), are discussed. The results of studying the effect of various factors (the ratio between EA polymer components, the chemical structure of curing agents, and curing modes) on the formation of BLs and adhesion strength of adhesive substances are reported by the example of epoxy-allylic (EA) polymer-polymer systems are reported.     

Detection of Organic Colorants in Historical Painting Layers Using UV Laser Ablation Surface‐Enhanced Raman Microspectroscopy

Surface‐enhanced Raman spectroscopy (SERS) has been increasingly used in the study of works of art to identify organic pigments and dyes in paintings, which (depending on the material) are difficult or not possible to detect by other current methods. The application of SERS to the study of paintings has been limited, however, by the lack of a sampling approach with sufficient sensitivity and spatial resolution. We show that ultraviolet laser ablation (LA) sampling coupled with SERS detection can be successfully used to study paint layers. LA‐SERS permitted the isolation of signals from colorants in individual thin paint layers in sample cross‐sections, avoiding contamination from adjacent layers. These results expand the range of analytical applications of SERS demonstrating how the technique can be used to sensitively detect minor organic components in complex matrices. While this is fundamental for the study of cultural heritage, it is also relevant in other fields such as forensic analysis, food science, and pharmacology.     

Electronic structure of intercalation compounds of molybdenum disulfide MMoS2 (M = Cu, Ag) studied by X-ray emission and X-ray photoelectron spectroscopies

Electronic structures of intercalation compounds of molybdenum disulfide in which the MoS2 layers alternate with layers formed by the metal atoms (Cu, Ag) were studied by X-ray emission and photoelectron spectroscopies. The character of participation of these or other valence states of atoms in the construction of occupied and unoccupied energy bands of the substances studied was considered on the basis of the X-ray spectra of various series.     

Analytical solution for restricted diffusion in circular and spherical layers under inhomogeneous magnetic fields

We propose an analytical solution for restricted diffusion of spin-bearing particles in circular and spherical layers in inhomogeneous magnetic fields. More precisely, we derive exact and explicit formulas for the matrix representing an applied magnetic field in the Laplacian eigenbasis and governing the magnetization evolution. For thin layers, a significant difference between two geometrical length scales (thickness and overall size) allows for accurate perturbative calculations. In these two-scale geometries, apparent diffusion coefficient (ADC) as a function of diffusion time exhibits a new region with a reduced but constant value. The emergence of this intermediate diffusion regime, which is analogous to the tortuosity regime in porous media, is explained in terms of the underlying Laplace operator eigenvalues. In general, regions with constant ADCs would be reminiscent of multiscale geometries, and their observation can potentially be used in experiments to detect the length scales by varying diffusion time.     

Near neighbor approximation in nuclear magnetic resonance

A new way to deal with the excitation by multiple effective RF fields with interference is presented using the coherent averaging theory. It significantly simplifies the calculation of the effect of RF interference that occurs in the excitations by periodic pulses and phase-incremented pulses (PIPs). This approach shows that each neighboring RF field contributes to an excitation profile an offset shift, which is termed the Bloch-Siegert offset shift (BSOS). The BSOS depends not only on the strengths of both RF fields that interfere with each other but also on their relative phase between the two RF fields. Consequently, it can be positive, negative, and zero. In addition, the BSOS is also inversely proportional to the frequency separation of the two RF fields. Therefore, only a few near neighbors need to be taken into account in most cases, resulting in a near neighbor approximation (NNA). The BSOS for two multiband excitation profiles, one by a periodic pulse and the other by a PIP, are calculated using the NNA. The results are in good agreement with the computer simulated ones.     

SOME PRESUPPOSITIONS IN THE METAPHYSICS OF CHEMICAL REACTIONS

The project of chemistry to classify substances and develop techniques for their transformation into other substances rests on assumptions about the means by which compounds are constituted and reconstituted. Robert Boyle not only proposed empirical tests for a metaphysics of material corpuscules, but also a principle for designing experimental procedures in line with that metaphysics. Later chemists added activity concepts to the repertoire. The logic of activity explanations in modern times involves hierarchies of activity concepts, transitions between levels through non-dispositional groundings. Such hierarchies terminate in powerful particulars, such as elementary charged particles. Do these have a fundamental place in the most recent accounts of molecular architecture, stabilities and transformations? However, a close study of the contemporary chemistry of substances transforming reactions discloses a hybrid metaphysics, making use of both the Boylean corpuscles and Faradayan fields. This is illustrated by an analysis of the metaphysics inherent in John Polanyi’s use of “chemoluminescence” to follow the formation of products in chemical reactions. A brief sketch of a resolution of the tension between the two metaphysical schemes is drawn from Niels Bohr’s radical metaphysics extended from the quantum realm proper to chemistry (and perhaps beyond).     

Zur Verbrennung flüssiger Substanzen nach Schöniger

Zusammenfassung Am Beispiel der Halogenbestimmung im Halbmikromaßstab wird gezeigt, daß sich das Schöniger-Verfahren durch eine einfache Modifikation auch auf flüssige Substanzen anwenden läßt. Nur bei sehr hohem Halogengehalt versagt die Methode.

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Summary By means of the halogen determination on the semi-micro scale, it is shown that the Schöniger procedure can be used also on liquid substances if a simple modification is employed. The method fails only when the halogen content is very high.

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Résumé Des exemples de semi microdosages des halogènes par la technique de Schöniger montrent qu'une simple modification permet de l'appliquer également à des substances volatiles. Elle n'est mise en échec que pour les substances à très haute teneur en halogènes.

     

水/醇溶共轭聚合物界面材料及其在光电器件中的应用

相对于传统的无机半导体器件,以有机半导体(特别是聚合物半导体)材料为基础的有机光电器件,可采用与传统印刷技术(例如喷墨打印、卷对卷印刷等)相结合的溶液加工方式制备低成本、大面积、柔性光电器件,因而成为广泛关注的焦点,并得到了快速发展.实现溶液加工的高效有机光电器件的一个关键问题是界面问题——如何避免溶液加工时有机层间的互溶以及如何实现可印刷稳定金属电极的高效电子注入等.水/醇溶性共轭聚合物的迅速发展为解决溶液加工多层有机光电器件所面临的界面问题提供了有效手段.研究发现,水/醇溶共轭聚合物不但可以有效避免溶液加工多层器件中的界面互溶,而且还可与高功函数的稳定金属发生界面偶极相互作用而增强其电子注入,从而解决了高功函数稳定金属电子注入的难题,为实现全溶液加工的高效印刷有机光电器件提供了可行的方案.本文介绍了近年来本课题组在水/醇溶共轭聚合物阴极界面材料及器件应用方面的研究进展,并对水/醇溶共轭聚合物阴极界面材料在聚合物发光二极管和聚合物太阳电池中的工作机理进行了探讨.     

Adsorbentien als Ionenaustausch- und Trennmedien Al2O3 und SiO2 in der chromatographischen Tensidanalytik

Summary In addition to their properties of being able to separate organic substance groups, Al₂O₃ and SiO₂ have obviously the ability to bring about an ion exchange. Both of them can be used on thin layers as well as on adsorption columns. Al₂O₃ provides the anion exchange under the conditions described, while SiO₂ brings about the cation exchange. LAS and cation-active surfactants of type DSDMAC, which are nearly always to be found in municipal wastes and sewage sludge, and which often occur in flowing waters, can be very well separated from one another and from accompanying and hazardous substances with the aid of these adsorbents. Even detergents and other technical mixtures which contain surfactants can be decomposed into separate components (substance groups) and analyzed. It can be assumed that Al₂O₃ and SiO₂ can also bring about the ion exchange for other ionogenic substances.     

钛基氧化物阳极中间层的研究进展

钛基氧化物阳极是国内外电化学领域应用广泛的优良阳极材料. 为提高电极导电性、延长电极使用寿命、增强钛基体和金属氧化物活性层之间稳定性,可以在钛基体和金属氧化物活性层之间添加氧化物等中间过渡层. 本文评述了钛基氧化物阳极中间层的研究进展,指出了钛基氧化物电极存在的问题,展望了中间层氧化物电极的发展趋势.     

Adsorption–Catalytic Test Methods

In the development of a new hybrid adsorption–catalytic method it was shown that the selective adsorption isolation of components can be combined with their catalytic determination directly on the adsorbent. To provide theoretical grounds and find fields of the application of the new method, the effect of the support matrix on the rate of catalytic (enzymatic and indicator) reactions was studied. The changes in the performance characteristics of procedures for determining inorganic and organic substances directly on the adsorbent with respect to those of procedures for determining in solutions were analyzed. It was proved that the development of catalytic test procedures with the visual detection of the analytical signal is expedient.     

Activation analysis and radiochemistry,comments to their interrelations

It is the aim of this paper, to demonstrate the manyfold interrelation between radiochemistry and activation analysis. One of the main problems of both fields is the behaviour of submicro concentrations of elements and of their compounds in solids, in solution and in the gas phase. The radiochemists were the first, who have accumulated much experience, investigating the properties of the natural radionuclides. HEVESY has, somewhat later, by his proposal of activation analysis, pointed out a special and powerful way for the determination of submicro amouts of substances. In the further development till to the present day, both fields have stimulated each other. Their exponents are specialists in understanding and handling submicro concentrations, i.e. in a section of science and technology, growing up to an outstanding importance.     

Recent process of plasma effect in organic solar cells

Due to the compromise between exciton diffusion length and light absorption, the active layer thickness of organic solar cells(OSCs) is limited. As we all know, embedding metal nanostructures into OSCs can improve the performance of OSCs by triggering surface plasma resonance, scattering, and other effect without increasing the physical thickness of light trapping layer. Besides, the plasma response and other roles will distinguish when metal nanostructures are embedded into different position of OSCs, which are equally important to the performance of OSCs. In this paper, the enhancement mechanisms of various metal nanostructures in different layers of OSCs are summarized from the electricity and optics aspects.This review also further highlights the progress of plasma effect and their working mechanism in OSCs,and it is expected to provide more perspective of plasma effect for performance enhancement of OSCs.     

REVIEW: metal complexes as urease inhibitors

Urease plays a significant role in the pathogenesis of several diseases and also has practical implications in other fields, such as agriculture or chemical analysis. Among the multitude of chemical species known to inhibit urease, metal complexes stand out as a special category due to their specific mechanism of action, distinct from purely organic substances. Their inhibitory activity seems to depend on the type of metal and its oxidation state as well as on the coordination environment of the central atom. Furthermore, the study of the interaction between metal ions and their complexes with urease renders valuable insights into detailed catalytic mechanisms of this enzyme. This brief survey attempts to provide an overview of the published research on urease inhibition by metal complexes.