The latest review of the material frontier (Week 1 of November 2017)

Abstract 1. ProgressionPolymerScience review: Progress in electrospun polymer nanofiber membranes for water treatment: manufacturing, modification and application The research on the formation of nanofibers in electrospinning in Figure 1 has been multiplied to increase

1. Progress in Polymer Science: Progress in electrospun polymer nanofiber membranes for water treatment: manufacturing, modification and application

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Figure 1 Schematic diagram of nanofiber formation in electrospinning

Membrane technology research has grown exponentially to treat wastewater, recover contaminated water, and provide more fresh water. Electrospun nanofiber membranes (ENMs) exhibit great potential for use in membrane processes due to their unique properties, such as high porosity up to 90% and large specific surface area. Compared to other nanofiber preparation technologies, electrospinning technology can develop the unique structure of nanofiber scaffolds by designing special components, and by combining multifunctional materials, nanofibers can be easily functionalized. Recently, Prof. Wang Rong (communication author) of Nanyang Technological University summarized the latest developments in the manufacture and modification of electrospun polymer membranes, especially highlighting their progress, challenges and future improvement directions in water treatment applications. . Firstly, the paper briefly introduces the complex process of electrospinning, expounds the intrinsic properties of polymer solution, operating parameters and ambient conditions on the formation of nanofibers and nanofiber membranes, and summarizes the various designs of electrospinning equipment. Subsequent review of methods for preparing multifunctional composite ENMs, including modification of nanofibers, loading target molecules onto the surface of nanofibers, and performing selective layers on the surface of the ENM. The author then provided a comprehensive discussion of past achievements and current challenges in using composite ENM in water treatment.

2. Progress in Polymer Science: Molecular self-assembly of one-dimensional polymer nanostructures in nanopores of anodized aluminum templates

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Figure 2 Schematic diagram of PMMA being confined to a two-dimensional cylinder of radius R

One-dimensional (1D) polymer nanostructures have received attention due to their unique properties and many potential applications in fields such as sensors, transistors, separation, storage and photovoltaic cells. Recently, Professor Atsushi Takahara (Corresponding author) of Kyushu University reviewed the research activities of one-dimensional polymer nanostructures prepared from anodized aluminum (AAO) templates. The method for preparing polymer nanostructures using AAO templates is described in detail, including polymer melt infiltration, polymer solution infiltration and chemical synthesis. Based on the molecular structure of the polymer, seven polymers were studied and demonstrated, amorphous homopolymer, amorphous-amorphous block copolymer, amorphous/amorphous polymer blend, semi-crystalline homopolymer, half Crystalline/amorphous polymer blends, semi-crystalline-amorphous block copolymers and semi-crystalline-semi-crystalline block copolymers in nanopores.

3. Nature Reviews Materials Overview: Widely tunable semiconductor alloy nanomaterial bandgap engineering

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Figure 3 Band gap and lattice constant of typical semiconductors and their alloys

In the past decade, great progress has been made in the development of nanoscale semiconductor materials with various band gaps by alloying different individual semiconductors. These materials include traditional II-VI and III-V semiconductors and their alloys, inorganic and hybrid perovskites, and emerging 2D materials. Recently, Yang Peidong and Dou Letian of the University of California at Berkeley and Professor Ning Cunzheng (co-author of Tsinghua University) and others introduced an important common feature of these materials. Their nanoscale dimensions lead to the overall structure of different compositions. Or a large tolerance of the lattice mismatch between the substrate and the target material, which in turn enables control of any alloy composition. Therefore, the band gap of these alloys can be widely adjusted without the presence of unavoidable harmful defects in the bulk material. These defects have limited tolerance to lattice mismatch. Such nanomaterials can have profound effects on photonic applications, including tunable lasers, solid state lighting, artificial photosynthesis, and new solar cells.

4. Chemical Society Reviews Overview: Structure, properties and applications of two-dimensional boron materials

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Figure 4 Conceptual geometric precursors for various boron structures

Boron is one of the most versatile elements between the metal and the non-metal in the periodic table, and can form at least sixteen large polymorphs composed of connected boron polyhedra. In the low dimension, boron chemistry is more intriguing because boron clusters with several to tens of atoms facilitate the formation of planar or cage structures, similar to carbon in conformation and electronic structure. Due to the similarity between boron and carbon, the question of whether or not there is stable two-dimensional (2D) boron is proposed, from which other boron nanostructures can be constructed. Recently, Professor Boris I. Yakobson (corresponding author) of Rice University and others reviewed the current progress in the theory and experimentation of the boron atomic layer. First, a decade of effort was made to understand the size-dependent structure of boron clusters, and then how to theoretically extrapolate boron clusters into two-dimensional forms, from independent states to substrates, and exploring the actual route effect. Although two-dimensional boron has been revealed to have unusual mechanical, electrical, and chemical properties, its potential is still greatly hindered in practical applications due to the lack of route from substrate transfer and controlled synthesis of mass samples.

5. Chemical Society Reviews Overview: Bio-derived nanostructured carbon and its composite materials as anode materials for lithium-ion batteries

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Fig. 5 Schematic diagram of biomass-derived carbon and its composite in LIB as anode

Growing energy demand has stimulated research activities for lithium-ion batteries (LIB). As a biomass of abundant renewable energy on the planet, it plays an active role in the development of sustainable biomass-derived carbon and its high-performance composite materials. Unlike other materials (such as silicon, tin, metal oxides, etc.), biomass-derived carbon and its composite materials are increasingly used in LIB due to their low cost, green and environmentally friendly synthesis, and are readily available. Sustainability and the ability to improve battery performance, including capacity, cycle performance and stability/durability. Recently, Long Wenyu, Yan-Jie Wang of Liaoning University of Petroleum and Chemical Technology and Professor David Wilkinson of the University of British Columbia (co-author) and others focused on the role of biomass-derived carbon and its composites in the LIB anode. It serves as a strategic guide for building a close link between renewable materials and electrochemical energy storage devices. In addition, this review provides important insights and comparisons of biomass-derived carbon and its composite LIB anodes, as well as important insights into other challenges and future directions in the field.

6. Chemical Society Reviews Overview: Engineering of inorganic nanoparticles as a magnetic resonance imaging contrast agent

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Figure 6. Factors affecting MRI: nanoscale size, surface and shape effects of CAs

Magnetic resonance imaging (MRI) is a very valuable non-invasive imaging tool due to its fine soft tissue contrast, high spatial resolution, low ionizing radiation, and extensive clinical applicability. Contrast agents (CA) can be used to further increase the sensitivity of MRI to obtain informative images. Recently, extensive research efforts have focused on the design and synthesis of high performance inorganic nanoparticle CAs to improve the quality and specificity of MRI. Recently, Shi Jianlin, Dalong Ni of the Shanghai Institute of Ceramics of the Chinese Academy of Sciences, Bu Wenbo of East China Normal University, Professor Cai Weibo of the University of Wisconsin (co-author) and others elaborated on the basic laws of CAs on MRI, including the selection of metal ions. The effect of electron motion on water relaxation and its mechanism of action. Various design principles are discussed in detail, including dimensional control, surface modification (eg, organic ligands, silica shells, and inorganic nanolayers) and shape adjustment to affect the relaxation of water molecules. A comprehensive understanding of how these factors work can guide the high relaxation engineering of future inorganic nanoparticles. Finally, the paper summarizes the currently available high-performance CA methods and mechanisms, and discusses the challenges and future development of nanoparticle CA in MRI clinical transformation.

7. Chemical Reviews Overview: Electrochemical Cationic Reaction Intermediates

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Figure 7 Schematic diagram of electrochemical cell method of reaction intermediate

Electrochemistry is a powerful method for producing reactive intermediates such as organic cations. In general, there are two ways to use a reaction intermediate to carry out a chemical reaction: (1) in the presence of a reaction partner; (2) in the absence of a reaction partner, accumulating as a "pool" in solution, followed by The reaction component is added to the reaction. The former method is more popular because the active intermediate is usually a transient transient species; but the latter method is more flexible and diverse. Recently, Prof. Jun-ichi Yoshida (Corresponding author) of Kyoto University and others highlighted the latter method and provided a reaction using modern electrochemical technology and its subsequent addition of a nucleophilic reaction component. A brief overview of the methods of generating and accumulating "pools" is provided.

8. Overview of the Accounts of Chemical Research: Applying X-ray diffraction and electron crystallography to solve complex structural problems

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Figure 8 characterization of complex structures

All crystalline materials in nature, whether inorganic, organic, biological, macroscopic or microscopic, have their own chemical and physical properties that are strongly dependent on their atomic structure. Therefore, structural determination is very important in the fields of chemistry, physics, and materials science. Among them, the most widely used is the use of X-ray crystallography (single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD)) to determine the structure of a crystalline material. Although SCXRD and PXRD are successful in many cases, many reasons limit their application. Another most valuable technical structural measure is Electronic Crystallography (EC). Especially for crystals that are too small, they cannot be studied by SCXRD, or if PXRD is too complicated, electrons can be used as probes, and individual ECs can also be used for structural determination. Since electrons interact with matter more strongly than X-rays, electron diffraction (ED) patterns and high-resolution transmission electron microscope (HRTEM) images can be obtained from nanocrystals. However, collecting a complete set of ED patterns or recording good HRTEM images requires considerable expertise in electron microscopy and crystallographic operations. Strong interactions between electrons and materials can also cause kinetic effects and beam damage. These difficulties make the structure of the ED mode and the HRTEM image determined not directly. Recently, two three-dimensional (3D) electron diffraction techniques, automatic electron diffraction tomography (ADT) and rotational electron diffraction (RED), have been developed which perform data acquisition in an automated manner. Although the kinetic effects of the newly developed 3D electron diffraction technique (ADT, RED) are significantly reduced, for some structures, the initial model obtained due to beam damage remains problematic. The above X-ray diffraction and EC methods are powerful techniques, but have their own limitations. In many complex cases, a single technique is not sufficient to solve the crystal structure, and different technologies that provide additional structural information must support each other for complete structural determination. Recently, Professor Sun Junliang (communication author) of Peking University summarized the advantages and disadvantages of X-ray diffraction (PXRD and SCXRD) and EC (HRTEM and ED) in structural determination, including X-ray diffraction and EC to solve complex structures. Application issues such as peak overlap, impurities, pseudo-symmetry and pairing, disordered frames, locating objects, aperiodic structures, etc. In addition, the article also provides a brief introduction to some of the latest developments in structural determination.

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