With expanding demand for high-performance batteries, Li-air batteries have been in spotlight due to the ultra-high theoretical energy density. Although some breakthroughs have been accomplished recently, their commercial level applications are still constrained by intense problems and challenges. Among them, sluggish reaction kinetics is assented as one of the serious issues responsible for unsatisfactory battery performance. Thus, an immense measure of exploration on cathode catalysts has been performed lately to improve the battery performance and facilitate the development. In this work, primary advancement and accomplishments on cathode catalysts for non-aqueous Li-air batteries have been summarized and comparatively discussed, and the future directions and developments have likewise been proposed.

Benefiting from its high oxygen reduction activity comparable with platinum catalyst, the transition metal and nitrogen co-doped carbon catalyst(M-N/C) has become one of the most important non-noble metal catalysts, and it is recognized as the most promising non-noble metal catalyst, as substitute of precious platinum catalyst, in proton exchange membrane fuel cells in the future. Metal organic frameworks(MOFs), a new class of crystalline porous materials with regular porous structure, high porosity, controllable morphology and size, and tunable ligands, have been regarded as perfect precursors for preparing various high-performance doped carbon catalysts. The catalysts derived from MOF often show superior structure and performance compared with those derived from conventional precursors, making them more prospective for applying in the fuel cells. Actually, it has become one of the most attractive topics to prepare M-N/C catalysts with MOFs as precursors in recent years. In this paper, we systematically introduce the research works on MOFs derived M-N/C catalysts at home and abroad in recent years, including the preparation technologies of MOF derived M-N/C catalysts, the strategies of improving the structure and performance of MOF derived carbon catalysts, as well as the research progress on the characterization technologies of such catalysts. Finally, we indicate the problems and challenges existed in MOF derived M-N/C catalysts, propose possible strategies/measures to solve the problems. The development and application of this type of new catalysts are also prospected.

As one of the most important and well-known chiral catalysts, 1,1'-binapthyl-2,2'-bisdiphenylphosphine metal complexes(BINAP-M) have been widely concerned in industry and basic theoretical research in the past few decades. Although BINAP-M as a homogeneous chiral catalyst has the characteristics of high activity and good selectivity, it also has the limitations of high price, high application cost and difficult to recycle, especially the catalyst residues in synthesis products such as pharmaceutical products, which limits its large-scale application in industry. Therefore, it has become an important research topic to search for BINAP-M catalysts which can not only keep high catalytic activity, but also be easy to recover and recycle. In this paper, the research progress of recyclable BINAP-M catalysts in recent years is summarized. The research results of adsorption-supported and covalently-supported BINAP-M catalysts in the field of recyclability are mainly introduced. The advantages and disadvantages of different types of recyclable BINAP-M catalysts are analyzed and discussed. On this basis, a covalently-supported BINAP-M catalyst with “flexible bridge chain” structure is also introduced, and its application prospect in “quasi-homogeneous” catalytic reaction is analyzed, which provides a new research idea for the design and preparation of supported catalyst.

Aqueous aerosols coated by surface-active organics, such as sea spray aerosol(SSA), commonly possess inverse micelle structure with an aqueous core coated by a hydrophobic organic monolayer. The surface organization and chemical composition of organic films of SSAs have important influence on their physical, chemical and optical properties. Langmuir monolayers are monomolecular layers formed by the diffusion of long-chain surface-active organics with low volatility, such as fatty acids, fatty alcohols and phospholipids at the air-water interface. With Langmuir trough, the changes in surface pressure(π) along with decreasing molecular area(A) of single and mixed component monolayers at the air-water interface can be obtained. In addition, π-A isotherms provide information about the interfacial behavior of corresponding monolayers above an aqueous surface. Understanding the interfacial properties of monolayers will enable the prediction of the fate and behaviors of surfactants in the real-world SSA. This paper reviews the commonly used interfacial characterization techniques of atmospheric aerosols, established models for SSA based on Langmuir monolayer, and the implications of organic films on atmospheric behavior of SSA. Although the physical properties and morphological changes of SSA-related monolayers have been studied in depth, little attention has been paid to the interfacial changes induced by environmental factors such as reactive gases, irradiation and bioactive substances. These knowledge gaps shed light on future laboratory simulation and model research of SSA.

With excellent photoelectric properties, lead halide perovskite nanocrystals(NCs) show great potential in solar cells, photoelectric detection, biological imaging and other fields. However, the poor stability of lead halide perovskite NCs restricts practical applications. Within a few years, many strategies have been developed to solve the problems of poor stability of perovskite NCs, such as ion doping, surface passivation and surface cladding. Noteworthily, it is an effective strategy developed recently that enhance the stability of perovskite by embedding perovskite NCs into polymer and preparing perovskite-polymer composites. Specially, the dense polymer matrix endows the lead halide perovskite NCs with excellent water stability. This review summarizes the preparation of perovskite-polymer composites and their applications in the fields of light-emitting devices and biomedicine. At the same time, the preparation methods of perovskite-polymer composites are discussed in details, which can be classified into three types: blending, in-situ polymerization and in-situ perovskite growth/precipitation method. These methods will be a guide to overcome the limitation of perovskite NCs and impel the development of their practical application. In addition, the existing problems for encapsulating perovskite NCs into polymer matrix are highlighted, while some suggestions for further improving the performance of perovskite-polymer composites are discussed. Finally, the future development of perovskite-polymer composites is prospected.

Zero-valent aluminum(ZVAl) possesses physical properties of good ductility and light weight, and has chemical properties of more negative redox potential. In the preparation process of new lightweight and high-strength composite materials, ZVAl has been taken preferentially as an ideal metal matrix. On the other hand, ZVAl, an excellent electronic donor, has been used for rapid hydrogen evolution and efficient removal of pollutants in the field of hydrogen production and environment remediation. Mechanical ball milling, is a novel material processing method which is simply operated and easy engineering. Furthermore, it can overcome the drawbacks of ununiform mixing and poor interface combination in the traditional preparation methods of aluminum-based metal materials. Moreover, it can destroy the dense oxide film on the surface of ZVAl, and break through the bottleneck that limits the electronic release of ZVAl. By ball milling ZVAl and grinding aids to control the grinding strength, the uniform dispersion and good interface bonding of the composites can be achieved,and a small amount of intermetallic compounds and chemically active substances are generated. As a result, the composites with excellent material properties can be obtained.Besides, the quantity of hydrogen production and the efficiency of pollutants removal could be increased through the function of the “cutter”, the mechanical chemical reaction such as displacement, carbonization or dechlorination, the change of microstructure during mechanical ball milling, and the pitting effect, the primary battery effect, the reduction of side reactions in the aqueous medium and other action mechanisms. Above all, this paper summarizes the principle of using mechanical ball milling to enhance the mechanical properties of ZVAl-based composite materials. In addition, the surface modification of ZVAl by mechanical ball milling and the mechanism of its application in hydrogen production and pollutant removal are systematically summarized. Afterward, the influence of ball milling parameters and water chemical conditions on the system are discussed. Finally, prospects of the research areas meriting for further investigation are pointed out. Supposing to promote the further development of mechanically modified ZVAl in the field of environment remediation through in-depth understanding of related fields of different disciplines.

Peptides with unique features such as small molecular weight, ease synthesis, good biocompatibility, high stability and versatile sequences, have received increasing interest as recognition elements for biosensors. Electrochemical analysis has wide applications because of its high sensitivity, good accuracy, simple equipment, wide detection range and easy to use. The peptide-based electrochemical biosensors can be used in many fields including environment monitoring, biomedicine and food detection. In this review, we introduce the peptide-based electrochemical biosensors for detection heavy metal ions, small-molecules, proteins, pathogenic bacteria and viruses. The strategies for peptide modification and immobilization are summarized. We also describe the properties and sensing mechanisms of peptide-based electrochemical biosensors. Sensing strategies especially those based on target-binding induced combination, digestion and phosphorylation of peptides have been discussed. Lastly, the current problems and prospect of the research on peptide-based electrochemical biosensor are discussed and prospected.

Exposure to toxic elements or organic contaminants associated with atmospheric particulate matters(APM) via inhalation may result in potential health risks to human. Up to day, various inhalation bioaccessibility procedures(IBAcP) have been advocated to investigate the bioaccessible concentrations of these contaminants in APM for the easy and fast risk-based assessment. In this review, the inhalation bioaccessibility of the toxic elements and organic contaminants in APM and the current IBAcP for the hazards assessment are reviewed and evaluated. In addition, the defects and challenges existed in current IBAcP are disclosed and the possible solutions are proposed.

Particle focusing in microfluidic device is a rapidly growing research field due to its wide applications in biology, chemistry, engineering, and medicine. Precise and high-throughput focusing can be a pivotal pretreatment step for counting, detection and separation application. Generally, focusing technologies can be divided into active, passive and sheath-assisted methods. The active and sheath-assisted methods rely on external energy field or sheath flow, which can accurately control the position of particles in microchannel, but require integrating other complex functional elements. Passive focusing uses fluid inertia, viscoelasticity, and other characteristics to control the equilibrium position of particles in the microchannel,and it has been proven to be a powerful tool due to the simplicity, label-free, biocompatible, contact-free, low-cost, and high throughout nature. A large amount of experimental and numerical work has been carried out on the passive focusing technology from the aspects of chip structure, microfluidic characteristics, and particle characteristics. In this review, the fundamental hydrodynamic forces and the basic principles related to the focusing mechanism were firstly briefly introduced and discussed. Then the state of the art of detailed passive focusing methods was presented. At last, the focusing methods were summarized and future development in this field was predicted.

Antifreeze proteins enable organisms to survive in subzero environments. Owing to this unique property, antifreeze proteins have great potential application in a variety of fields. Antifreeze proteins have been extensively studied, but the antifreeze mechanism is still fragmentary, due to the limitation of experimental means. Molecular dynamics, as a method to simulate the interaction between molecules at the atomic level, has been widely used in the study of the mechanism of antifreeze proteins in recent years. In this paper, the functional and structural characteristics of antifreeze proteins, and the research progress of antifreeze mechanisms are described and reviewed from the perspective of structure. Furthermore, the structural characteristics of 29 wild-type antifreeze proteins with known crystal structure, and the hydrophobicity of the residues distributed on the protein surface and at the ice-binding site are analyzed. Both the affinity of the interaction between hydrophilic residues and water and the specificity of the interaction between hydrophobic residues and ice-like water are found either on the surface or at the ice-binding site of antifreeze proteins. The relationship between the secondary structure, the hydrophobicity of the residues at ice-binding site and the antifreeze activity is discussed. Finally, the mechanisms of antifreeze proteins and the factors affecting the antifreeze activity are discussed from the perspective of structure, and the progress in the design and application of bioinspired antifreeze materials with low toxicity and cost is briefly summarized.

In recent years, synchronously mediating the reactivity and electron selectivity(ES) of zerovalent iron(ZVI) toward target contaminant has been of great interest but challenging to researchers. Sulfidation can suppress the side reaction of ZVI with water under anaerobic conditions and thus improve the ES toward target contaminants. As such, this review systematically summarizes the physicochemical characteristics of sulfidated ZVI(S-ZVI) as function of the sulfidation approaches, reagents and extents. Then, this work analyzes the interactions of contaminants removal by S-ZVI. Typically, the sulfidation can tune the electrical conductivity and/or hydrophobicity of ZVI, thereby enhancing the reactivity and ES toward target contaminants under aerobic or anaerobic conditions, which is strongly dependent on S/Fe molar ratio but without regard to the approaches and reagents of sulfidation. Finally, the application potentials of S-ZVI for groundwater remediation and wastewater treatment are also outlooked.

Due to the unique biological functionality resulting from the nano scale, nanocarriers can deliver various kinds of anti-tumor drugs in vivo through specific design, showing an important application prospect. Since the advent of tumor immunotherapy, a brand-new anti-tumor method, the combination of various nanocarriers and tumor immunotherapy has gradually become one of the important means to improve the effect of tumor immunotherapy. Among them, as a new kind of biomimetic drug carrier platform, the nanocarrier modified by cell membrane can make the nanocarrier achieve the camouflage modification of natural cell membrane. Meanwhile, such a decoration is able to transfer the specific functions and biological characteristics of cell membrane to the nanocarrier, so that it is equipped with stronger ability of anti-immune clearance, long blood circulation and tumor targeting, and thus reduces the immunogenicity and cytotoxicity of nano delivery system. Therefore, the membrane modified nanocarriers can play a greater role in biomedical applications, especially in tumor immunotherapy. In this article, combined with the mechanism of immunotherapy, the preparation methods, anti-tumor mechanism and application research in tumor immunotherapy of nanocarrier systems modified by numerous kinds of cell membrane in recent years are reviewed, and on this basis, the related exploration in the future is prospected.

The complex of poly(3,4-ethylenedioxythiophene)∶poly(4-styrenesulfonate)(PEDOT∶PSS) is a water-soluble conducting polymer system with many advantages such as easy processability, high transmittance and flexibility. Its application, however, is only limited as flexible electrode material in some electronic devices. To solve this, introducing inorganic nanomaterials into PEDOT∶PSS complex to realize multifunctional materials is a relatively effective method to further expand its application. In this review, four most commonly used strategies to prepare PEDOT∶PSS/inorganic nanocomposites, including in-situ method, blending method, self-assembly method and intercalation method are summarized at first. Following this, each of the methods is detailed with their mechanism and experimental features, and the structural design of the nanocomposites as well as the structure-property relationships that affected by introduced inorganic nanofillers are also elucidated. Then the latest research progress of applications in sensors, solar cells, supercapacitors, thermoelectric generators of PEDOT∶PSS/inorganic nanocomposites are reviewed. Finally, the existing challenges in PEDOT∶PSS/inorganic nanocomposites studies are pointed out, and the future perspectives are provided for the research direction and potential progress and trends of these materials.

5-Hydroxymethylfurfural(5-HMF) is regarded as the most developing and potential platform in recent years. The hydrolysis of cellulose to glucose and then to5-HMFis the key steps in the use of biomass resources to produce green platform compounds. Understanding the catalytic conversion process from glucose to5-HMFis of great significance for improving the potential utilization of biomass resource. Solvent systems and outfield coordination used for the preparation of5-HMFfrom glucose was introduced in this work, focusing on the mechanism of the conversion from glucose to5-HMFincluding the isomerization of glucose to fructose and the dehydration of fructose to 5-HMF. Single-phase solvents, ionic liquids, biphasic solvents and deep eutectic solvent was used in5-HMFproduction. The biphasic solvents system composed of ionic liquid and organic solvent is the most effective reaction solvent system, which can quickly transfer the5-HMFto the organic phase, reduce side reactions and increase the yield of 5-HMF. Outfield coordination of ultrasound vibration, microwave radiation and pressure field accelerate mass transfer and heat transfer, greatly shorten the reaction time and improve the reaction efficiency through the synergistic reaction with the reaction solvent. The improvement of5-HMFyield and the stability of intermediates require further research.

Porous liquids(PLs), an emerging class of liquid materials with permanent porosity and good fluidity, have shown great potential in gas capture and separation. As a result, PLs used as gas capture materials have become a new research hot spot. In the present paper, the concept of PLs is firstly introduced in a nutshell. Then, the composition characteristics and the necessary conditions for constructing PLs are analyzed. Next, the synthesis progress of these three types of PLs are reviewed in detail, and their gas capture and separation performance are analyzed, especially after 2015. Lastly, the existing challenges of porous liquids and their outlooks of synthetic methods and applications in gas capture are outlined and presented.

Deoxyribonucleic acid(DNA) is an important biological molecule with many unique properties such as information transmission, molecular recognition, editability, etc. DNA hydrogels have the advantages of both DNA molecules and the hydrogel materials, and can introduce other nanomaterials to obtain multifunctional hybrid hydrogels. Compared with traditional hydrogels, DNA hydrogels have good specific recognition ability and the properties that can be designed on demand, so they are widely used in the field of biosensing. This article reviews the synthesis, response mechanism and application of DNA hydrogels in the field of sensing. According to different synthesis methods, DNA hydrogels can be divided into linear DNA strand interwinded hydrogel, dendritic DNA self-assembly hydrogel, and hybrid DNA hydrogel. According to the different sensing mechanism, DNA hydrogels can be divided into encapsulation type DNA hydrogels and non-encapsulation type DNA hydrogels. The encapsulation method is divided into: enzyme embedding release, antigen-antibody embedding release, and nanomaterial embedding release. This article summarizes the application and research of DNA hydrogels in the detection of heavy metal ions, nucleic acid detection, glucose detection, protein and metabolic small molecule detection, and cell detection in recent years, and finally prospects its future development.

In recent years, gene interference technology based on small interfering RNA(siRNA) has shown great potential in reversing multidrug resistance of chemotherapy by regulating various proteins related to multidrug resistance of tumor at the gene level. In view of this, the researchers have done a lot of work in the area of RNA interference and chemotherapy drugs. But the free siRNA is not easy to be absorbed by cells without carrier, and it will be degraded by endogenous ribonuclease in plasma and tissues. Therefore, it is necessary to load siRNA on the carrier in order to effectively apply it to tumor treatment. In view of the safety, high efficiency and targeting of nanocarriers, a large number of nanocomposite systems have been developed which can simultaneously load siRNA and chemotherapy drugs. In this paper, the application of nanomaterials in co-loading siRNA and reversing multidrug resistance of chemotherapy drugs are reviewed. In addition, in order to have a better understanding of the related work, some targets which are often used in the study to reverse multidrug resistance are also briefly described.