Toward rational and modular molecular design in soft matter engineering

This essay discusses some preliminary thoughts on the development of a rational and modular approach for molecular design in soft matter engineering and proposes ideas of structural and functional synthons for advanced functional materials. It echoes the Materials Genome Initiative by practicing a tentative retro-functional analysis(RFA) scheme. The importance of hierarchical structures in transferring and amplifying molecular functions into macroscopic properties is recognized and emphasized. According to the role of molecular segments in final materials, there are two types of building blocks: structural synthon and functional synthon. Guided by a specific structure for a desired function, these synthons can be modularly combined in various ways to construct molecular scaffolds. Detailed molecular structures are then deduced, designed and synthesized precisely and modularly. While the assembled structure and property may deviate from the original design, the study may allow further refinement of the molecular design toward the target function. The strategy has been used in the development of soft fullerene materials and other giant molecules. There are a few aspects that are not yet well addressed:(1) function and structure are not fully decoupled and(2) the assembled hierarchical structures are sensitive to secondary interactions and molecular geometries across different length scales. Nevertheless, the RFA approach provides a starting point and an alternative thinking pathway by provoking creativity with considerations from both chemistry and physics. This is particularly useful for engineering soft matters with supramolecular lattice formation, as in giant molecules, where the synthons are relatively independent of each other.     

On soft-oxometalates (SOMs) and crystallization of polyoxometalates (POMs)

Under suitable conditions liquids crystallize. In this article, we establish with examples from the literature and our own works that the soft-matter state of oxometalates or soft-oxometalates (SOMs) is such a liquid. We further demonstrate that POM crystallization can be considered as a phase transition from SOMs. The review concludes with implications of such a point of view in futuristic materials design.     

Short-time dynamics of proteins in solutions studied by neutron spin echo

Dynamics of proteins in solutions include translational, rotational, and internal motions that are linked to different protein properties. Because most proteins are small with the sizes of just a few nanometers, the timescale for their short-time dynamics usually ranges from a few nanoseconds to a few hundreds of nanoseconds, during which a protein usually does not rotate too much. Protein short-time dynamics has been shown to be useful to study liquid theories, protein cluster formation, gelation transitions of concentrated protein systems, and protein internal motions. Neutron spin echo, which is able to measure protein motions with the right correlation time at the appropriate length scale, is ideally suitable to study the short-time dynamics of proteins in solutions. Here, we review recent activities of using neutron spin echo to study the protein short-time motions. Despite all progresses, there are still both theoretical and experimental challenges to exploit the full capability of neutron spin echo to study protein dynamics.     

Recent developments in assessment of bio-accessible trace metal fractions in airborne particulate matter: A review

In the last years a great deal of research has been focused on the determination of harmful trace metals such as Cd, Co, Cr, Cu, Ni or Pb in airborne particulate matter (APM). However, the commonly applied determination of total element concentrations in APM provides only an upper-end estimate of potential metal toxicity. For improved risk assessment it is important to determine bio-accessible concentrations instead of total metal contents. The present review gives an overview of analytical procedures reported for measurement of bio-accessible trace metal fractions in APM. The different approaches developed for extraction of soluble trace metals in APM are summarized. Furthermore the analytical techniques applied for accurate determination of dissolved trace metals in the presence of complex sample matrix are presented. Finally a compilation of published results for bio-accessible trace metals in APM is included.     

Birch还原及其在合成中应用进展

Birch还原是联接芳香族和脂肪族化合物的桥梁,它使许多芳香族衍生物成为合成脂肪族化合物,尤其六元脂环天然产物的起始原料,因此Birch还原是有机合成中很有用的方法。本文主要以几种最普通芳香族化合物用于脂肪族天然产物的合成例子,讨论Birch还原的合成潜力及其还原产物的合成应用,介绍了Birch还原在合成应用中的最新进展。     

Recent developments in analytical applications of quantum dots

This review discusses the application of quantum dots (QDs) to chemical and biological detection, for which they have excellent features, particularly size-dependent optical properties.We can summarize the main areas discussed in this review as follows:(1) QDs associated with enzyme-linked immunosorbent assay (ELISA), chip detection and capillary electrophoresis (CE) enhance the sensitivity and the speed of detection of residues;(2) QDs are applied with other techniques, including polymerase chain reaction (PCR), fluorescence resonance-energy transfer (FRET) analysis, fluorescence in-situ hybridization (FISH) and western blot analysis; and,(3) QDs combined with the above techniques can successfully detect DNA and protein.We also cover perspectives and challenges in analytical applications of QDs.     

Recent developments and applications of grazing incidence scattering

A review of recent developments and applications of grazing incidence scattering is presented. In particular, high energy X-rays now make possible the investigation of buried, solid–liquid and liquid–liquid interfaces with high spatial resolution and possibly time resolution. Elemental sensitivity can be provided by resonant reflectivity and fluorescence based techniques using hard and soft X-rays. The use of partial coherence at third generation synchrotron sources enables one to go beyond the statistical properties of interfacial systems and to investigate their dynamics.     

Recent developments in polymer dynamics investigations of architecturally complex systems

The tube model for linear and branched architectures is nowadays able to predict in high precision the linear viscoelastic relaxation time spectrum. For linear chains, the involved time scales fit to the commonly accessible dynamic scattering techniques. This makes it possible to microscopically investigate the correlation between structures and relaxation processes. In branched systems, however, the hierarchical nature of relaxations limits direct investigation via these microscopic methods as the dynamic processes are prolongated to much longer relaxation times that are no more accessible to usual dynamic scattering methods. A way to overcome this difficulty is offered by the use of static small angle neutron scattering. Here, the combination of annealing and quenching steps after a step deformation provides unique information of the structure at particular times along the relaxation spectrum. This, however, necessitates the availability of architecturally clean and specifically deuterium labelled model polymers due to the sensitivity of the scattering method. Therefore, we outline in this contribution first the current status on the synthesis and analysis of such compounds with relation to neutron scattering. Secondly, we present exemplary neutron scattering results from in situ stress relaxation studies inside the neutron beam on linear and H-shaped branched polymers which were molecularly designed to highlight specific relaxation processes. We discuss the relevance of the tube model parameters in linear and non-linear studies.     

Recent developments in the properties and applications of polyelectrolyte multilayers

Complexity and innovation in the application of layer-by-layer adsorbed polyelectrolyte systems continues to grow. In this review, we will recap recent findings on the application of multilayers at the biological interface, and as thin films for controlling wetting properties. We also review recent experiments on determining the mechanical properties of polyelectrolyte multilayers.     

Recent developments in and applications of resonance ionization mass spectrometry

Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the status of a routine method for sensitive and selective ultratrace determination of long-lived radioactive isotopes in environmental, biomedical and technical samples. It provides high isobaric suppression, high to ultra-high isotopic selectivity and good overall efficiency. Experimental detection limits are as low as 10⁶ atoms per sample and permit the fast and sensitive determination of ultratrace amounts of radiotoxic contaminations. Experimental arrangements for the detection of different radiotoxic isotopes, e.g. ^236–244Pu, ^89,90Sr and ⁹⁹Tc in environmental samples are described, and the application of RIMS to the ultrarare long-lived radioisotope ⁴¹Ca for cosmochemical, radiodating and medical purposes are presented. Received: 17 December 1998 / Revised: 11 February 1999/Accepted: 18 February 1999     

Recent developments in and applications of resonance ionization mass spectrometry

Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the status of a routine method for sensitive and selective ultratrace determination of long-lived radioactive isotopes in environmental, biomedical and technical samples. It provides high isobaric suppression, high to ultra-high isotopic selectivity and good overall efficiency. Experimental detection limits are as low as 10⁶ atoms per sample and permit the fast and sensitive determination of ultratrace amounts of radiotoxic contaminations. Experimental arrangements for the detection of different radiotoxic isotopes, e.g. ^236–244Pu, ^89,90Sr and ⁹⁹Tc in environmental samples are described, and the application of RIMS to the ultrarare long-lived radioisotope ⁴¹Ca for cosmochemical, radiodating and medical purposes are presented. Received: 17 December 1998 / Revised: 11 February 1999/Accepted: 18 February 1999     

Recent developments and applications of microextraction techniques in drug analysis

Sample preparation is important for isolating desired components from complex matrices and greatly influences their reliable and accurate analysis. Recent trends in sample preparation include miniaturization, automation, high-throughput performance, online coupling with analytical instruments, and low-cost operation through extremely low or no solvent consumption. Microextraction techniques, such as liquid-phase microextraction and solid-phase microextraction, have these advantages over the traditional approaches of liquid–liquid extraction and conventional solid-phase extraction. This review focuses primarily on these microextraction techniques developed over the last decade, and presents a summary of the characteristics of various approaches in drug analysis.     

Surface tension of liquid metals and alloys — Recent developments

Surface tension measurements are a central task in the study of surfaces and interfaces. For liquid metals, they are complicated by the high temperatures and the consequently high reactivity characterising these melts. In particular, oxidation of the liquid surface in combination with evaporation phenomena requires a stringent control of the experimental conditions, and an appropriate theoretical treatment. Recently, much progress has been made on both sides. In addition to improving the conventional sessile drop technique, new containerless methods have been developed for surface tension measurements. This paper reviews the experimental progress made in the last few years, and the theoretical framework required for modelling and understanding the relevant physico-chemical surface phenomena.     

Recent developments in oriented polymers for biomedical and engineering applications

A review is presented of recent research at Leeds University which has been directed at devising novel methods for the production of oriented polymer structures. First, the new hot compaction process for oriented fibre and tapes is described, together with its applications to polyethylene and polypropylene where there are a number of practical developments. Secondly, there is the use of hydrostatic extrusion to make load bearing oriented products from hydroxyapatite filled polyethylenes. The production routes include the application of high pressure annealing prior to hydrostatic extrusion and the preparation of high modulus polyethylene fibre/hydroxyapatite billets as the starting point. Finally, recent progress on die-drawing as a means to producing oriented monofilaments and biaxially oriented tubes is described, where the applications include polymer ropes, pipes for gas and water distribution and transparent cans for packaging.     

Recent developments and applications of EMMA in enzymatic and derivatization reactions

This review provides systematic coverage of examples in the field of in-capillary electrophorecially mediated microanalysis (EMMA). The recent developments and applications in the time period up to mid 2011 have been described, as well as relevant older papers. The basic principles and modes of in-capillary assays have been demonstrated. An overview is also given of the various injection, separation and detection modes implemented in combination with EMMA. The review is presented in two parts mainly dealing with (i) enzymatic and (ii) derivatization or chemical reactions. Finally, the future trends of CE in performing and monitoring reactions have been drawn.     

可见光光催化降解抗生素研究进展

随着抗生素废水在水体和陆地生态系统的肆意排放,抗生素污染已成为当今世界重要的环境问题。由于抗生素废水具有生物毒性大、含有抑菌物质等特点,传统的物理吸附法、生物处理法在处理这类难降解有毒有机废水,尤其是含残留微量抗生素的废水时效果较差。为了解决抗生素废水所引起的环境危机,人们尝试了许多方法。近年来,光催化技术作为一种适用范围广、反应速率快、氧化能力强、无污染或少污染的处理抗生素废水的方法受到人们广泛关注。半导体材料在太阳光照射下,可产生具有较强氧化作用的羟基或超氧自由基,从而起到降解抗生素分子的作用。然而,传统的光催化处理抗生素废水光催化剂主要局限于 TiO2半导体,它存在太阳光谱吸收范围窄、光生电荷复合率高等问题,严重制约其工业化应用。因此,人们一直致力于开发高效、稳定的可见光响应型光催化剂。本文根据光催化技术的基本原理,综述了目前几种基于不同策略设计开发可见光光催化降解抗生素废水的新型光催化剂的方法。
　　离子掺杂改性宽带隙半导体是开发高效可见光光催化剂的常用方法。通过过渡金属离子或非金属离子掺杂改性,可以使传统的 TiO2和SrTiO3等紫外光催化剂吸收带边发生红移,响应可见光,从而显著提高可见光下光催化剂降解抗生素的效率。然而必须注意的是,掺杂的金属离子本身会成为电子-空穴复合点位,因此,过量的掺杂金属或非金属离子可能会降低其光催化活性。考虑到单一半导体材料在光催化反应中存在的光生载流子容易复合、可见光利用率低等问题,构建异质结构复合光催化体系,通过不同半导体之间的协同作用,促进光生电荷的分离与转移,是获得高效光催化体系的重要策略之一。典型的 II型异质结光催化剂,当不同的半导体紧密接触时,由于异质结两侧能带等性质的不同会形成空间电势差,从而有利于光生载流子的分离,光催化效率提高。作为一种复合光催化体系,表面等离子体共振增强型光催化体系近年来引起了国内外学者的广泛关注。 Ag, Au和Pd金属纳米粒子在吸收光后其表面发生等离共振,随后等离子体发生衰减,把聚集的能量转移到半导体材料的导带。这个过程产生的高能电子(热电子),逃离贵金属纳米粒子而被与其接触的半导体收集,从而形成金属-半导体肖特基接触。形成的肖特基结可以显著提高光催化的光生电荷分离效率,从而提高光催化降解抗生素活性。
　　目前,与传统物化法/生化法相比,光催化技术用于处理抗生素废水具有十分明显的技术优势,在水处理方面有着很好的应用前景。针对目前光催化体系存在的光生载流子容易复合的巨大挑战,今后,构筑高效复合光催化体系(例如石墨烯基二维复合光催化剂在光生电荷分离、太阳光利用率等方面已展现出较好的综合性能)将成为高效光催化降解抗生素催化剂研发的重要方向之一。     

Recent developments in the synthesis and catalytic applications of chiral phosphetanes

Enantiomerically pure phosphetanes are easily obtained from primary phosphines and chiral, symmetrically substituted anti-1,3-diols. The synthetic approach has been applied to the preparation of both monodentate and C₂-symmetric bidentate derivatives. Applications of these ligands in rhodium- and ruthenium-promoted hydrogenations of unsaturated substrates have been reported: peculiar catalytic properties and high enantioselectivities have been noticed. To cite this article: A. Marinetti, J.-P. Genêt, C. R. Chimie 6 (2003).     

Recent developments in the field of screen-printed electrodes and their related applications

The development of analytical methods that respond to the growing need to perform rapid ‘in situ’ analyses shows disposable screen-printed electrodes (SPEs) as an alternative to the traditional electrodes. This review presents recent developments in the electrochemical application of disposable screen-printed sensors, according to the types of materials used to modify the working electrode. Therefore, unmodified SPE, film-modified SPE, enzyme-modified SPE and antigen/antibody-modified SPE are described. Applications are included where available.     

Recent developments in the application of X-ray and neutron reflectivity to soft-matter systems

Many interesting physical, chemical and biological phenomena occur at interfaces between nanometre-scale layers of soft condensed matter. These often complex systems lend themselves to be studied by X-ray reflectivity (XRR) and neutron reflectivity (NR). The application of these techniques to such systems is extremely widespread and provides unique insights into their structure and dynamics. This review presents a snapshot of recent activity in this research area and identifies trends in the application of XRR and NR to novel, unusual or highly complex sample systems. Although the majority of research using these techniques is investigating variations on ‘traditional’ systems, supported by progress in instrumentation, advance sample environment and computational tools, NR and XRR have begun to produce singular insights into areas such as atmospheric science, real biological systems (cells and bacteria), oil–water interfaces or industrial problems (rheology, packaging or durability of nanomaterials).