Cancer is the second leading cause of death in the world, and the incidence rate of cancer remains high every year. Although existing treatments have made significant progress in the past decade, due to the non-specific cytotoxicity, poor biocompatibility and low bioavailability of existing anti-tumor drugs, the therapeutic effect of chemotherapy and other methods is poor. Exosomes are membrane vesicles secreted by various kinds of cells with phospholipid bilayer structure and nano particle size (30~100 nm). Exosomes are the media of information exchange and material transportation between cells, carrying proteins, lipids, nucleic acids and other substances of host cells. With the in-depth study of exosomes, their application is more and more widespread. In the process of intercellular communication, exosomes can regulate the biological response of target cells, which may promote or inhibit disease. They have good biocompatibility, high stability and excellent targetability. Exosomes serving as potentially effective drug delivery systems in cancer treatment have attracted increasing attention. In order to enhance the therapeutic effect of exosomes and reduce the toxicity of drugs to normal cells, it is necessary to improve the targetability of exosomes. Researchers try to customize exosomes with different targeting categories and abilities by modifying exosomes in various ways, which endows exosomes with broad prospects in the field of targeted therapy of tumors. This review highlights the design strategy of exosomes as drug carriers to target tumors, and tries to provide new insights of exosomes-based nanocarriers in various tumor treatment. Besides, this review mainly introduces the biogenesis of exosomes, the physiological function of exosomes and their separation methods. Particular attention is paid to the design strategy of engineered exosomes targeting tumors, including using exosomes from different sources, different surface modification methods and different stimuli-responsive exosomes. Finally, we summarize and discuss the progress of exosomes as drug carriers to solid tumors, and the deficiencies of exosomes in clinical application.

Luminescent liquid crystalline polymers (LLCPs), combining the ordering, stability, mechanical properties of the liquid crystalline polymer with the luminescent properties of chromophores, show broad applications. In order to obtain high-efficiency LLCPs, various LLCPs with different structures have been successfully designed and synthesized, including main-chain, side-chain, mesogen-jacketed LLCPs and LLCP network, etc. Meanwhile, interaction of the molecular structure, liquid crystalline phase structure and optical physical properties, has also been carefully investigated. In this paper, the latest progress of LLCPs is summarized, including the molecular design and synthesis, structure and properties, and their applications. At last, a brief outlook on the future development in this field is presented.

Hygroscopicity is one of the aerosol’s most important physicochemical properties, which affects the lifetime and atmospheric behavior of aerosols. It plays a vital role in the environment, climate change, and human health. The hygroscopicity parameters and thermodynamic models are introduced. The effects of aerosol diameter, chemical composition, and multi-component aerosol on hygroscopicity are analyzed in the following section. The relevant observations in the urban, rural area, forest, polar region, and ocean are summarized. Hygroscopicity growth factor (g(RH)), scattering enhancement factors (f(RH)) and hygroscopicity parameter κ are common hygroscopicity parameters which can represent aerosol hygroscopicity. The Zdanovski-Stokes-Robinson (ZSR) mixing rule and many thermodynamic models can predict the aerosol hygroscopicity with different chemical compositions, which are some important tools to study the multi-component aerosol and phase equilibrium. Aerosol diameter, chemical composition and mixed state affect hygroscopicity, for example g(RH), and changes in deliquescence relative humidity or efflorescence relative humidity. Because of different emission sources and environmental conditions, the aerosol particle size distribution, chemical composition and mixed state are different in the urban area, rural area, forest, polar region and ocean, and then aerosol hygroscopicity are different. Hygroscopicity affects aerosol water content and phase state directly, and atmospheric chemical processes, aging process and lifetime of aerosol will be changed. Environmental visibility, radiation effects, and aerosol deposition sites and toxicity in the human body also are influenced by aerosol hygroscopicity. Overall, a comprehensive review of hygroscopicity parameters, theoretical models, laboratory studies, field experiments, and environmental impacts provides a reference for future research.

Fluorescent probes have become a powerful tool for the study of complex biological systems due to their high sensitivity and selectivity. Compared with single-photon fluorescence probe, two-photon fluorescence probe (TPFP) plays an irreplaceable role in biosensor due to its larger penetration depth, lower interference of tissue autofluorescence and better spatial selectivity. In this review, starting from the design strategies of TPFP, we systematically and comprehensively introduce the application of TPFP in the determination of metal ions, celluar microenvironment, reactive species (including reactive oxygen species ROS, reactive nitrogen RNS, reactive sulfur RSS), enzymes, organelles (mitochondria, lysosomes) and so on. After that, we look forward to the key opportunities and challenges in the development and application of organic TPFP.

As the prerequisite of life evolution, survival and reproduction, autonomous locomotion is the most basic function of organisms. In recent years, many artificial systems have been developed to simulate the motion behavior and to study the locomotion mechanism of living organisms. Among many kinds of artificial bionics systems, self-oscillating gels have attracted much attention due to its performance of internal drive to generate kinetic energy, directionality, untethered ability and environmental self-adaptation. In this review, the origin of chemo-mechanical energy conversion and the bionic locomotion modes of self-oscillating gels observed until now are introduced and summarized. On the basis of this, the opportunities, challenges and future directions of this field are prospected.

Due to the addressability, programmability and excellent biocompatibility, DNA has been applied not merely in constructing static elegant nanostructures with different shapes and sizes, but also in designing dynamic nanodevices. Moreover, to further expand the application of DNA, functional groups or molecules can be conjugated with DNA through chemical modification. DNA could combine with hydrophobic organic molecules to be a new amphiphilic building block and then self-assemble into nanomaterials. So far, DNA has been covalent with polymers, dendrimers, peptides or proteins, and the assembly behavior and potential application of these hybrids have been widely investigated. Of particular note, recent state-of-the-art research has turned our attention to the amphiphilic DNA organic hybrids, including small molecule modified DNA (lipid-DNA, fluorescent molecule-DNA, etc.). This review focuses mainly on the development of their self-assembly behavior and their potential application in biomedicine. The potential challenges regarding the amphiphilic DNA organic hybrids are also briefly discussed, aiming to advance their practical applications in nanoscience and biomedicine.

Over 100 million people around the world are at the risk of the drinking arsenic-contaminated water. It is urgent to solve this severe security issue of drinking water caused by arsenic which is highly toxic and difficult to dispose of. Nanoscale zero-valent iron (nZVI) is one of the most extensively applied nanomaterials due to its efficient removal of pollutants such as, heavy metals, nitrates, phosphates, perchlorates, halides, polycyclic aromatic hydrocarbons and phenols. nZVI-based remediation has grown into a prominent sub-field of environmental nanotechnology, with nearly 60 in-situ remediation projects, pilot and full-scale wastewater treatment projects conducted worldwide. Its unique core-shell structure and surface properties enable nZVI to remove arsenic efficiently through adsorption, co-precipitation and reduction process. Herein, the latest progress of nZVI and various nZVI-based materials for arsenic contaminated water remediation is reviewed. The removal behavior and its influence by initial solution pH, contact time, dosage of nZVI, arsenic initial concentration, coexisting ions and organic matters are presented, with special emphasis on the removal mechanism. The iron oxide/hydroxide on the surface of nZVI rapidly adsorbs the arsenic in the solution and transforms to arsenic-iron co-precipitation. If the As solution is deoxygenated, reduction of As(Ⅲ) and As(Ⅴ) to As(0) occur during the adsorbed arsenic diffuse into the iron oxide. In addition, the research progress of four kinds of nZVI-based materials for arsenic removal are summarized, including nZVI supported with porous materials, rare metals loaded nZVI, nZVI surface modified with stabilizer and green synthesis nZVI. Finally, possible improvement of remediating arsenic contaminated water with nZVI and nZVI-based materials are also proposed.

The abundance of sodium salt in the earth’s crust is 1000 times higher than that of lithium. At the same time, low-cost aluminum foil can be used as the anode of sodium ion battery instead of copper foil, and the low-temperature characteristics are more excellent, which has a good application prospect in energy storage and standby energy storage scenarios. Therefore, sodium ion battery is considered one of the ideal choices for the next generation of large-scale energy storage technology. However, compared with lithium ion, the large ion radius and mass of sodium ion greatly limit its reversible deintercalation in electrode materials, resulting in relatively low working voltage and energy density of the battery. In the sodium ion battery materials system, the research of cathode materials needs great progress. In this paper, the existing typical cathode materials for sodium ion batteries are reviewed, including layered metal oxides, polyanions and Prussian blue compounds. The effect of doping on the performance of cathode materials for sodium ion batteries is analyzed. The cycling reversibility, reversible capacity and diffusion kinetics of sodium ions can be improved by element doping, which can change the properties of the crystal lattice to a certain extent, and enhance the stability, electronic conductivity and intercalation kinetics of sodium ions. In this paper, the achievements of doping application in the existing materials are summarized, and the future research direction and development prospect of cathode materials are put forward.

Arsenic and antimony pollution is widespread around the world. Compared with the conventional iron oxide, Fe(Ⅲ) minerals formed by microbial oxidation have a stronger adsorption capacity for aqueous As/Sb. There are wide application prospects of these minerals because of the advantages of high removal efficiency, practicability and environmental friendliness. However, the microbial reduction of the Fe(Ⅲ) minerals may lead to the release of adsorbed As/Sb. This paper reviewed the process of effect of microbial participated iron redox process on As/Sb removal. The microbial cycle of “synthesis, dissolution and transformation” of iron minerals and the mechanism of immobilization, dissolution and transformation of aqueous As/Sb associated with this cycle are concluded. The mineralogy of Fe(Ⅲ) minerals synthesized by microorganisms is illustrated. The thermal dynamics and coordination mechanism of the binding of Fe(Ⅲ) minerals with As/Sb are explained. The factors affecting As/Sb removal by microbial synthesized Fe(Ⅲ) minerals are summarized. Based on the existing problems in this field, the outlook of As/Sb removal by microbial iron redox has prospected.

The outbreak of the COVID-19 has increased the demand for point-of-care testing (POCT), and as the most indispensable tools for human beings at present, smartphones have great application potential in POCT. Smartphone-based POCT has the following unique advantages: (1) easy to operate and without the need for professional training; (2) shorter wait times and quicker test results; (3) low fabrication cost and convenient to use in limited-resource areas. Therefore, smartphone-based POCT is rapidly emerging as a potential alternative to traditional laboratory testing. Herein, we perform a comprehensive review of recent progress and applications of smartphone-based sensors in POCT for the past three years, which uses the tested objects (body fluids, volatile organic compounds, vital signs) by POCT as the basis for classification, and combines with the current mainstream sensing strategies, including colorimetric, fluorescent, electrochemical technology, piezoelectric, pyroelectric, ultrasonic and photoelectric sensor, etc. We evaluate the performance and development potential of these sensors, in addition, the emerging technologies used in POCT are introduced, such as nanotechnology, flexible electronic devices, microfluidic technology, biodegradable technology, self-powered technology, multi-channel detection and so on. Finally, current problems are summarized and the future development of the smartphone-based POCT is discussed.

Electrochemiluminescence (ECL) combines the characteristics of electrochemistry and chemiluminescence. Because of its high sensitivity, wide linear range and low background interference, electrochemiluminescence has attracted the attention of many researchers in analytical science. Although the traditional luminescent materials of ECL have high luminous efficiency, they still have some disadvantages, such as high price, lower sample load, etc. g-C₃N₄ is a kind of metal-free semiconductor nanomaterial, which is based on triazine ring or heptazine ring as the basic structural unit. g-C₃N₄ is a two-dimensional graphite-like layered structure bonded by vander Waals forces between layers and C—N covalent bonds within layers. Since g-C₃N₄ was first discovered to have ECL performance in 2012, it had been widely used in the development and fabrication of ECL sensors, due to its advantages, such as stable property, unique band structure, good biocompatibility, better environmental performance, easy to function, inexpensive ingredients and simple preparation process. The research progresses of g-C₃N₄ in ECL sensor construction in recent years were reviewed, according to the mechanism of ECL luminescence, the effect of sensor, the signal type of sensor,and the different types of detection objects. And the challenges and prospects of g-C₃N₄ in ECL development were described as well.

With the rapid development of electric vehicles and portable electronic products, the demand for high-energy-density battery systems is becoming more and more urgent. However, the energy density of traditional lithium-ion battery cathode materials is approaching the theoretical limit, thus it is urgent to develop the next-generation battery system with higher energy density. Sulfur cathodes possess lots of advantages, such as high energy density, natural abundance, and low cost, achieving extensive research attention. For the conventional dissolution-deposition mechanism, sulfur cathodes suffer from “shuttle effect”, resulting in irreversible loss of active material, low coulomb efficiency, and poor cycle life. To alleviate the “shuttle effect”, a series of strategies are usually adopted, for instance, physical confinement, chemical adsorption, and reaction accelerators, but none of them can fundamentally solve these problems. Recently, the quasi-solid-state conversion reaction of sulfur cathodes has attracted wide attention. This review discusses these approaches for constructing quasi-solid-state conversion reaction of sulfur cathodes, including the designs of microporous carbon structure, the formation of a solid electrolyte interface (SEI) on the sulfur surface, and electrolyte engineering. The research significance is highlighted and electrochemical behaviors of the quasi-solid-state conversion reaction of sulfur cathodes are summarized. Enhancing the reactivity of sulfur cathode is an effective strategy to alleviate the intrinsic sluggish kinetics of sulfur cathodes. These strategies for quasi-solid-state conversion mechanism of sulfur cathodes are beneficial to cyclability, enabling the practical development of high-performance Li-S batteries.

As a kind of green renewable energy, solar energy has attracted wide attention, and impurity removal is a necessary purification process to obtain solar grade silicon from metallurgical grade silicon, which is very important for the preparation of silicon-based solar cells. The new technology for preparing solar grade polysilicon by the metallurgical method has become the focus of research and development because of its advantages such as low energy consumption, low cost and less pollution. However, the effective removal of boron is one of the most severe challenges we face. In this paper, the thermodynamic and kinetic properties of boron (solubility, diffusivity, diffusion coefficient, mass transfer coefficients and activity coefficient) and the research topics of boron removal in recent years (gas blowing, slag treatment, plasma treatment, acid leaching and solvent refining) are reviewed. It is found that solvent refining is a promising method to obtain high purity silicon. The enrichment rate of silicon and the removal rate of boron can reach more than 90%. Additives can strengthen the formation and precipitation of borides to improve the boron removal process, and the subsequent almost can be completely eliminated, which will not cause pollution to the refined silicon, which will be more effective in boron removal and increase the practicability of the process. At the end of the paper, several deboration processes are compared and analyzed, and the application prospect of metallurgical process is forecasted.

Environmental pollution and energy shortage caused by the rapid development of the economy have become two major problems in modern society. Accordingly, much research is currently focused on the exploitation of new alternative energy sources. Among various energy sources, solar energy is considered to be ideal and renewable energy. Under sunlight irradiation, photocatalysis, as a novel “green technology”, can directly convert organic pollutants into innoxious substances to solve both energy crisis and environmental pollution. However, the key to the success of this process is dependent on the rational design and fabrication of efficient photocatalysts. The NiFe₂O₄ possessing fast magnetism response and good photochemistry stability, is coupled with other semiconductor photocatalysts having a suited band gap in order to obtain greatly effective photocatalytic systems and achieve the magnetic separation, exhibiting wide application foreground. This paper mainly reviews the latest research progress on the synthesis and photocatalytic application of NiFe₂O₄-based composites, which may open a new avenue and idea for preparing highly active and magnetically separable composite photocatalysts. Finally, the future development of NiFe₂O₄-based photocatalytic materials is also prospected.

As a novel and unique large-scale instrument, the synchrotron radiation facilities have been progressively applied to the research of atmospheric science. This article introduces the theoretical principles, key technologies, and recent major research results of key synchrotron radiation-based experimental methods. The main synchrotron radiation technologies include the atmospheric pressure X-ray photoelectron spectroscopy (APXPS), the near edge X-ray absorption fine structure (NEXAFS) and the scanning transmission X-ray microscopy (STXM). A key component (environmental cell) commonly used in all three technologies is explained in detail. This article classifies the collected research according to experimental types, i.e., APXPS experiments, liquid jet experiments and STXM experiments. The main topics include: (1) ice surface, (2) salt surface, (3) acidic solution, (4) organic solution, (5) halite solution, (6) ozonolysis, (7) soot, (8) ice nuclei, (9) hygroscopicity and (10) reaction mechanism. The development of synchrotron radiation facilities has provided strong support for the research of aerosol science and atmospheric heterogeneous chemistry, giving atmospheric scientists the ability to explore unknown fields and latitudes. It is foreseeable that more and more important atmospheric processes and mechanisms will be revealed by technologies based on synchrotron radiation, which will also reflect the great potential and value of synchrotron radiation devices in the field of atmospheric and environmental science.

Fuel cell is a kind of renewable new energy technology, which can directly convert the chemical energy of fuel into electric energy through the chemical reaction at the interface of electrode and electrolyte. Because energy conversion efficiency is high, no noise and pollution.Proton exchange membrane fuel cell (PEMFC) is one of the most widely used fuel cells, but PEMFC still has some problems to be solved, such as high cost, low power density and poor catalyst stability. Therefore, to achieve the large-scale application of proton exchange membrane fuel cell, research and development of high activity and high stability catalyst is the top priority. In order to meet the requirements of high activity and high stability of fuel cell catalysts, this paper reviews the research progress and performance improvement methods of catalysts for fuel cells. The methods to improve the stability of fuel cell were discussed from the perspectives of active components and carrier. The performance of catalyst was improved by reducing the diameter of active component particles, preparing platinum particles with specific orientation surface, alloying platinum with transition metals and the modification of carrier also had a significant impact on the stability of catalyst. Finally, the future development direction of fuel cell catalysts and the main problems in practical application are proposed.

Electrochemical CO₂ reduction to value added chemical feedstocks and fuels driven by renewable electricity gives a promising and appealing approach to address the global challenges in energy and sustainability and eventually close the anthropogenic carbon cycle. The most crucial step for this conversion is to develop robust electrocatalysts promoting adsorption of CO₂ molecule and subsequent activation with low energy barriers. Due to the different overpotentials and electron transfer amount needed for various reduction products, there is huge gap of producing price among a variety of products. Based on recent research, formic acid (or formate) is one of the most economically viable and useful reduction product in a couple of chemical processes. In this paper, starting with fundamental understanding of reaction mechanism, we review the main progress of p-block post-transition metal (e.g., Sn, Bi, and In) based electrocatalysts for electrochemical CO₂ reduction to produce formic acid. In addition, strategies to facilitate the catalytic performance of CO₂ to formic acid) conversion including reduction conversion of metal oxides, morphology control, doping and alloying to modulate the electronic structure are also be briefly reviewed. Finally, we summarize the existing challenges and present perspectives for the future development of this exciting field.

Carbonaceous materials with superior catalytic activity, which could avoid drawbacks of heavy metal ion leaching for metal-based catalysts, are widely used in advanced oxidation processes (AOPs). Biochar, a carbon-rich material produced by pyrolysis of biomass under oxygen limited condition, is low-cost, widely available, and environmentally friendly. Biochar has been utilized to activate peroxides such as hydrogen peroxide, peroxymonosulfate and peroxydisulfate for the degradation of pollutants in water. In this paper, precursors and preparation methods of biochar as well as their influence on catalytic activity of biochar are discussed. The activation mechanisms of peroxides by biochar and the effects of water matrices on the degradation of pollutants are summarized. The progress in the modification of biochar is reviewed. The reusability of biochar is elucidated and the regeneration methods of biochar are provided. In the end, the problems and the prospects of the biochar-based AOPs are put forward.