Diffusion coefficients of solids in supercritical carbon dioxide: Modelling of near critical behaviour

Most of the models proposed in literature for binary diffusion coefficients of solids in supercritical fluids are restricted to infinite dilution; this can be explained by the fact that most of experimental data are performed in the dilute range. However some industrial processes, such as supercritical fluid separation, operate at finite concentration for complex mixtures. In this case, the concentration dependence of diffusion coefficients must be considered, especially near the upper critical endpoint (UCEP) where a strong decrease of diffusion coefficients was experimentally observed. In order to represent this slowing down, a modified version of the Darken equation was proposed in literature for naphthalene in supercritical carbon dioxide. In this paper, the conditions of application of such a modelling are investigated. In particular, we focus on the order of magnitude of the solubility of the solid and on the vicinity of the critical endpoint. Various equations proposed in literature for the modelling of the infinite dilution diffusion coefficients of the solutes are also compared. Ten binary mixtures of solids with supercritical carbon dioxide were considered for this purpose.     

Activity volcano plots for the oxygen reduction reaction using FeN4 complexes: From reported experimental data to the electrochemical meaning

Electrochemistry and electrochemical experiments are powerful tools for obtaining information about the thermodynamics and kinetics of electrochemical reactions. In electrocatalysis, these two parameters are often framed together to improve the understanding of the interactions of a catalyst and a reactant. Generally, “volcano-type” correlations are composed to compare similar catalysts. In this type of correlation, kinetic versus thermodynamic parameters are juxtapose to identify the most active catalyst positioned at the top of the volcano trend. In this work, we delve into the obtaining of this type of correlations to clarify the significance and utility. In particular, the study of the oxygen reduction reaction (ORR) has been selected due to its importance in energy conversion devices such as fuel cells and metal-air batteries.     

Recent advances of Rh-based intermetallic nanomaterials for catalytic applications

Rhodium (Rh) has received widespread attention in fundamental catalytic research and numerous industrial catalytic applications. Compared to homogeneous catalysts, Rh-based nanomaterials as heterogeneous catalysts are much easier to separate and collect after usage, making them more suitable for commercial use. To this purpose, there has been a constant demand in constructing stable and highly active Rh-based nanomaterials. In contrast to Rh-based solid solutions with a random distribution of metallic atoms in the lattice, Rh-based intermetallic compounds (IMCs) with a fixed stoichiometric ratio and an ordered atomic arrangement can ensure the homogenous distribution of active sites and structural stability in the catalytic process. In this review, we concentrate on the fabrication of Rh-based IMCs for catalytic applications. Various synthetic methods and protocols for the controlled preparation of Rh-based IMC are illustrated. Meanwhile, the catalytic applications and corresponding catalytic mechanisms are discussed. In addition, personal perspectives about the remaining challenges and prospects in this field are provided. We believe this review will be useful in directing the development of Rh-based IMC catalysts for heterogeneous catalysis.     

Photoelectrochemical and Photovoltaic Characteristics of Amorphous‐Silicon‐Based Tandem Cells as Photocathodes for Water Splitting

In this study amorphous silicon tandem solar cells are successfully utilized as photoelectrodes in a photoelectrochemical cell for water electrolysis. The tandem cells are modified with various amounts of platinum and are combined with a ruthenium oxide counter electrode. In a two‐electrode arrangement this system is capable of splitting water without external bias with a short‐circuit current of 4.50 mA cm^?2. On the assumption that no faradaic losses occur, a solar‐to‐hydrogen efficiency of 5.54 % is achieved. In order to identify the relevant loss processes, additional three‐electrode measurements were performed for each involved half‐cell.     

Isoselenocyanates: a powerful tool for the synthesis of selenium-containing heterocycles

Selenium-containing heterocyclic compounds have been well recognized, not only because of their remarkable reactivities and chemical properties, but also because of their diverse pharmaceutical applications. In this context, isoselenocyanates have been emerged as a powerful tool for the synthesis of selenium-containing heterocycles, since they are easy to prepare and store and are safe to handle. In this review the recent advances in the development of synthesis methods for selenium-containing heterocycles from isoselenocyanates are presented and discussed.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-hydroxy-imidamide-functionalized graphene: an efficient metal-free electrocatalyst for oxygen reduction

Metal-free electrocatalysts for oxygen reduction reaction (ORR) are key to the development of efficient, durable, and low-cost alternatives to noble-metal-based electrocatalysts in fuel cell cathodes. In recent years, many efforts are directed to the metal-free catalyst based on heteroatom-doped graphene. In this work, we demonstrate that the graphene surface can be converted into the catalyst for the oxygen reduction by chemical functionalization. In this context, we first synthesized malononitrile-functionalized graphene oxide. Amidoximation of nitrile group and reduction in graphene oxide were then carried out by hydroxylamine in one step. The electrochemical behavior of functionalized graphene-modified electrode for the reduction in oxygen was studied. The results showed that the electrocatalyst fabricated by this method exhibited striking catalytic activities in alkaline solution. In alkaline solution, this catalyst showed a competitive activity to the commercial Pt catalyst via four-electron transfer pathway with better ORR selectivity and stability. In addition, this metal-free electrocatalyst exhibited tolerance to methanol crossover effect. Based on its outstanding performance, this functionalized graphene electrocatalyst showed the promising prospect of a metal-free catalyst for fuel cell with much lower cost than currently used Pt/C catalyst.     

Design of organophosphorus materials for organic electronics and bio-applications

π-Extended molecules are key components for the development of materials science. In fact, polyaromatic structures are fundamental for the scientific and technological progress of fields such as organic electronics and bio-applications. Beneficial properties of π-extended structures are absorption in the visible region, often luminescence, high electron mobilities and stability. Common approaches to adjust the properties of polyaromatic structures to functional setups involve changes in shape and size at the molecular level. Recently, incorporating hetero-elements emerged as successful approach. In this regard, organophosphorus conjugated molecules are new materials holding great promise for potential applications. In this review, we comprehensively discuss the design/development of polyaromatic phosphorus materials and their applicability. We establish structure/property/applicability relationships to provide key guidelines for the engineering of newer, future applications. This article thus provides a source of information for the further development of this rapidly evolving field of research.     

Micro-structured analytical instrumentation for the analysis of liquids

Micro-structured analytical instruments are designed for manipulating and transporting fluids and biological entities. In the near future they will form the key element for so-called micro Total Analysis Systems. Conventionally, these elements are made from glass or silicon by wet-etching. In comparison to these materials, a much wider range of micro-structuring technologies is available for plastic materials. Polymers have the additional advantage of being readily replicable with low-cost methods such as injection molding or hot embossing. Functioning microchips for different purposes were produced this way. An advantage of micro-structured analytical instruments is the handling of ultra-small volumes. In some cases this can result in inappropriate detection limits. Two concepts to overcome this problem are demonstrated: an on-column conductivity detector and the coupling of microchips with mass spectrometry. To achieve a higher sample load capacity compared to miniaturized separation devices for capillary electrophoresis, isotachophoresis is applied. Isotachophoresis is used as a separation technique in itself and as a sample pre-concentration technique in combination with capillary electrophoresis.     

Symplectic Methods for the Numerical Solution of the Radial Shrödinger Equation

In this paper new symplectic-schemes for the numerical solution of the radial Shrödinger equation are proposed. In particular, symplectic integrators for Hamiltonian systems have been developed. Based on this approach, second- and third-order methods are proposed. These methods are more accurate than the existing ones. We compare these methods not only with the existing symplectic methods, but also with a classical Runge–Kutta–Nyström method.     

Microfabrication and microsensors

In order to fabricate microsensors, a micromachining, microfabrication technique based on LSI technologies has been used. In this paper, useful micromachining techniques are described. Examples of integrated microsensors, such as a pressure sensor including a readout circuit and a multisensor cell for blood gas analysis, are introduced. Microflow control devices, such as a microvalve and a micropump for integrated chemical analysis systems, are also described.     

Measurement of low vapour pressures according to the Knudsen effusion method

The exact measurement of low vapour pressures during recent years has become increasingly important, particularly for environmental problems caused by organic chemicals. Not only for this but for many other fields information about the phase transition solid - gas and liquid - gas is of great scientific interest. In this work a brief survey of the determination of vapour pressures with thermo-analytical methods is made. In particular the thermo-gravimetric vapour pressure measurements by means of a Knudsen cell and a newly developed vapour pressure balance for exact measurement of very low vapour pressures are described. Applications for organic materials (fungicides, benzoic acid, oils) are discussed.     

分子筛限域单原子金属催化剂的研究进展

分子筛由于具有规则的微孔孔道结构、 较大的表面积、 优异的(水)热稳定性, 被认为是限域合成超小尺寸金属物种的理想载体. 近年来, 分子筛限域单原子金属催化剂由于超高的金属分散度、 接近100%的金属利用率以及独特的电子结构, 被广泛地应用于重要的催化反应和气体吸附分离过程. 本文系统地总结了近年来分子筛限域不同类型单原子金属催化剂的合成策略, 以及其在多相催化和气体分离等领域的研究进展. 最后, 提出了分子筛限域单原子金属催化剂在合成与表征方面存在的挑战和未来的发展方向.     

Strategies for ensuring that regenerative cardiomyocytes function properly and in cooperation with the host myocardium

In developed countries, in which people have nutrient-rich diets, convenient environments, and access to numerous medications, the disease paradigm has changed. Nowadays, heart failure is one of the major causes of death. In spite of this, the therapeutic efficacies of medications are generally unsatisfactory. Although whole heart transplantation is ideal for younger patients with heart failure, many patients are deemed to be unsuitable for this type of surgery due to complications and/or age. The need for therapeutic alternatives to heart transplantation is great. Regenerative therapy is a strong option. For this purpose, several cell sources have been investigated, including intrinsic adult stem or progenitor cells and extrinsic pluripotent stem cells. Most intrinsic stem cells seem to contribute to a regenerative environment via paracrine factors and/or angiogenesis, whereas extrinsic pluripotent stem cells are unlimited sources of cardiomyocytes. In this review, we summarize the various strategies for using regenerative cardiomyocytes including our recent progressions: non-genetic approaches for the purification of cardiomyocytes and efficient transplantation. We expect that use of intrinsic and extrinsic stem cells in combination will enhance therapeutic effectiveness.     

Double layer interaction between two plates with polyelectrolyte brushes

When polyelectrolyte chains are grafted to colloidal particles, the electric field between particles is affected by the charges of the chains. In some previous theoretical attempts, the charge density of the polyelectrolyte chains per unit length was considered constant, and its effect was accounted for by introducing an additional constant charge density into the unidimensional Poisson-Boltzmann equation, which was evaluated assuming that it is uniformly distributed in the polyelectrolyte volume of the brush. In this paper, a more detailed model is employed for the calculation of the electrical potential between two plates on which polyelectrolyte brushes are present. In this model, the polyelectrolyte chain is viewed as a rigid cylinder, on the surface of which charges are generated through the dissociation of ionizable sites and adsorption of the cations of the electrolyte. To each of the chains an atmosphere is attached which for simplicity is assumed cylindrical. In the brush region, the electrical potential is described by a two-dimensional Poisson-Boltzmann equation, while in the region free of polyelectrolyte chains by a unidimensional Poisson-Boltzmann equation. Such a model is physically suitable when the charges of the chains are sufficiently large for the repulsion they generate to ensure that the chains are fully extended. Such cases are quite frequent, because relatively low charges lead to an almost complete extension of the chains. In this paper, both the plate surface and the surface of the cylinders are considered charged. The effects of electrolyte concentration, pH, brush thickness and chain coverage density on the repulsion between plates are examined.     

Two‐Photon Fluorescent Probes for Metal Ions

Two‐photon microscopy (TPM) has become an indispensible tool in biology and medicine owing to the capability of imaging the intact tissue for a long period of time. To make it a versatile tool in biology, a variety of two‐photon probes for specific applications are needed. In this context, many research groups are developing two‐photon probes for various applications. In this Focus Review, we summarize recent results on model studies and selected examples of two‐photon probes that can detect intracellular free metal ions in live cells and tissues to provide a guideline for the design of useful two‐photon probes for various in vivo imaging applications.     

The polarographic determination of indium in zinc-base alloys : The determination of indium in mazak alloys

In this paper, the development of a co-precipitation method for the separation of indium from zinc alloys is described and a method for the determination of indium down to 0.5 p.p.m. in mazak alloys is presented. Results obtained in trials of this method are given and the final conclusions regarding this and previously developed methods are included.     

Polyaniline/Au Electrodes for Direct Methanol Fuel Cells

In this paper we demonstrate the use of polyaniline/gold modified electrodes that are to be used as the anode for direct methanol fuel cells (DMFC). The objective of this work was to enhance the performance and viability of DMFCs by developing a more efficient catalyst for the oxidation of methanol. Polyaniline films with angstrom scale atomic gold clusters were used as an electroactive catalyst. These gold clusters are significantly different than what is traditionally used as they are composed of only a handful of atoms (1–10 atoms) and have unique physical and chemical properties. The PANI/Au modified electrodes are a new and promising catalyst for direct methanol fuel cells and can replace existing commercial catalysts. In this study, we illustrate how atomic clusters of gold incorporated in the conducting polymer polyaniline enhanced the oxidation signal of methanol exhibited by cyclic voltammetry.     

合成气直接转化制取芳烃研究进展（英文）

芳烃类化合物是石化行业重要的基础原料.非石油基碳资源经合成气直接转化制取芳烃具有重要的应用前景,但该过程仍存在着芳烃收率低以及催化剂稳定性差等难题.近年来相关工作取得重要进展,研究人员尝试通过高效催化剂的设计和操作条件的优化以获得更好的催化反应性能.本综述首先对该过程进行了热力学分析,并根据催化剂体系对相关研究成果进行分类总结,主要包括改性FT催化剂和复合催化剂.然后,对各类催化剂体系的反应性能特点和机理进行了深入探讨.改性FT催化剂常采用添加助剂或引入分子筛载体的方法调变反应中间体在传统FT催化剂上的反应路径,以促进芳烃的生成.但是,该过程倾向于生成链烃而致使芳烃选择性受到限制,而且容易形成积炭,催化剂稳定性差.复合催化剂可分为氧化物-分子筛和FT-分子筛催化剂,合成气首先在氧化物或者FT催化剂上生成某些亚稳态中间物种,随后扩散至分子筛孔道内经芳构化转化为芳烃.对于氧化物-分子筛复合催化剂,CO在氧化物上活化并生成醇类(主要是甲醇),随后在分子筛上进行C-C偶联、环化、芳构,生成芳烃.在该串联反应中,由于中间产物的不断转化,不仅使CO加氢反应的平衡右移,提升转化率,而且增加了芳烃的收率与反应的稳定性.另外,该过程CH4产物的选择性极低.对于FT-分子筛复合催化剂,合成气首先在高温FT催化剂上生成低碳烃类,然后转移至分子筛孔道内进行芳构化,该方法可以获得较高的CO转化率但芳烃选择性仍比较低.文章还详细描述了针对不同过程的反应器设计,包括单反应器和双反应器.在单反应器中可装填改性FT催化剂或物理混合的复合催化剂.对于复合催化剂,存在两种活性组分的优化反应条件不一致以及混合方式影响反应活性和产物分布等问题.因此,探索更佳的反应工艺条件对于实现合成气直接转化制芳烃的工业应用具有重要意义.双反应器则是将复合催化剂的两种功能组分分开装填,使分步过程分别在各自最佳反应条件下进行,从而避免了不匹配的问题.最后,该综述展望了合成气直接转化制芳烃过程存在的挑战和应用前景,为更好地设计催化剂、构建反应路径和优化工艺条件提供指导.