N₂ fixation, a process that transforms N₂ into biologically usable forms, is mainly accomplished by biological and industrial processes, respectively. Biological N₂ fixation is carried out by nitrogenase at ambient conditions. Coupled to the hydrolysis of ATP and accompanied by the formation of H₂, N₂ is reduced to NH₃. Industrial N₂ fixation is accomplished by Haber-Bosch process, in which N₂ is reduced to NH₃ efficiently in the presence of iron catalyst and promoter. The process invented more than a century ago is carried out at high temperature and high pressure(400~500 ℃, above 100 atm), which consumes lots of energy, in addition to the large amount of energy consumed in methanol steam reforming to produce hydrogen. Nowadays, people are looking for the next-generation industrial catalyst by taking inspiration from N₂ fixation mechanism of nitrogenase. Light-driven(photocatalytic) N₂ fixation is very promising especially considering that energy for N₂ fixation is ultimately from photosynthesis. In this paper, the recent progress in the field of bioinspired photocatalytic N₂ fixation in addition to some research on electrocatalytic N₂ fixation are summarized. Last, our perspectives of this field are provided. Although currently there is still no good substitution for catalyst system used in conventional Haber-Bosch process, a review of research progress and experience will provide beneficial implications for future design of efficient catalysts.
Contents
1 Introduction
2 Biological N₂ fixation and nitrogenase
2.1 Biological N₂ fixation
2.2 N₂ fixing mechanism and inspiration of nitrogenase
2.3 Transition metal complex for catalytic N₂ fixation
3 Photocatalytic N₂ fixation
3.1 Mechanism of photocatalytic N₂ fixation
3.2 Synthetic N₂ fixing photocatalysts
3.3 Biological hybrids and nitrogenase simulated photocatalysts
3.4 Overview of electrocatalytic N₂ fixation
4 Conclusion and outlook

In recent years, one-dimensional (1D) polymer-inorganic nanocomposites have attracted considerable attention due to their unique structures, excellent properties and tremendous application prospects. Since the composite of the inorganic phase and polymer phase in the nanoscale could remarkably promote the intrinsic properties and the functions, the corresponding materials exhibit outstanding performances in electron transmission, optical properties, mechanical properties and so on. Many of them possess application potentials in the fields of electronic devices, energy storage devices, photochemical sensors, catalysts and other fields. By enumerating several different 1D polymer-inorganic composite nanostructures, three commonly used strategies, including template synthesis method, electrospinning method and 1D assembly method are summarized herein. The principles and the characteristics of various preparation methods are introduced. Finally, the outlook for future development is prospected.
Contents
1 Introduction
2 Preparation of 1D polymer-inorganic composite nanomaterials by template synthesis
2.1 Hard templates
2.2 Soft templates
2.3 1D inorganic templates
3 Preparation of 1D polymer-inorganic composite nanomaterials by electrospinning
4 Preparation of 1D polymer-inorganic composite nanomaterials by 1D assembly method
5 Conclusion

Carbon quantum dots acting as a new class of “zero-dimensional” carbon nanomaterials have attracted much attention. Hydrothermal carbonization method has been by far one of the most widely used synthesis methods. Many kinds of raw materials can be selected for preparing carbon quantum dots via hydrothermal carbonization method. The preparation process of hydrothermal carbonization is simple. It is able to obtain the carbon quantum dots with abundant oxygen-containing functional groups on the surface and showing excellent water solubility via hydrothermal carbonization. Furthermore, surface functional modification of carbon quantum dots can be carried out during the preparation process. The carbon cores of hydrothermal carbon quantum dots are graphite or amorphous structures. The structures and properties of hydrothermal carbon quantum dots are influenced mainly by raw material types and preparation conditions (including hydrothermal carbonization temperature, time and chemical additives). The products have found good applications in the fields of photocatalysis technology, analysis and detection, the vivo imaging and cellular labeling, light-emitting diodes (LED), drug delivery and so on. In this review, the preparation, properties, formation mechanism (including dehydration, polymerization, carbonization and passivation progress of raw materials) and luminescence mechanism (including surface defect state effect and quantum size effect) of hydrothermal carbon quantum dots are summerized. Simultaneously, the applications of hydrothermal carbon quantum dots are reviewed. The problems remaining to be solved are summarized and the future developments are prospected.
Contents
1 Introduction
2 Preparation of hydrothermal carbon quantum dots
2.1 Influence of feedstocks
2.2 Influence of preparation conditions
3 Properties of hydrothermal carbon quantum dots
3.1 Surface chemical structure
3.2 Crystal structure
3.3 Optical property
4 Formation mechanism of hydrothermal carbon quantum dots
5 Luminescence mechanism of hydrothermal carbon quantum dots
5.1 Surface defect state effect
5.2 Quantum size effect
6 Applications of hydrothermal carbon quantum dots
6.1 Photocatalysis
6.2 Detection probes
6.3 Bioimaging
6.4 Drug delivery
6.5 Light-emitting diodes
6.6 Other applications
7 Conclusion

Schiff-base covalent organic frameworks (Schiff-base COFs) are a class of crystalline porous polymers with strong covalent bonds via Schiff-base condensation reaction. The COFs materials possess the advantages of low density, large surface area, tunable pore size and structure, facilely tailored functionality, versatile covalent-combination of building units, diverse synthetic methods, easy of introducing specific molecular recognition sites, excellent physical and chemical stability, and so on. These advantages provide the COFs materials with superior potentials in diverse applications, such as gas storage/adsorption, sensing, catalysis, optoelectronic material, and as enrichment media of sample pretreatment.Currently, Schiff-base COFs have become a research hotspot in the field of materials science.This review mainly describes the state-of-the-art development in the synthesis, preparation and application of Schiff-base COFs materials. In the end, the current statuses of COFs are summarized, and the future trends and application potentials of the COFs materials are also prospected.
Contents
1 Introduction
2 Types of COFs synthesized
2.1 Imine linkage
2.2 Hydrazone linkage
2.3 Azine linkage
2.4 Polyimide linkage
3 Synthetic methods of COFs
3.1 Solvothermal synthesis
3.2 Microwave synthesis
3.3 Mechanochemical grindig synthesis
3.4 Room-temperature synthesis
3.5 Surface synthesis
4 Applications of COFs
4.1 Gas storage/adsorption
4.2 Catalysis
4.3 Sensing
4.4 Optoelectronic material
4.5 Sample pretreatment media
4.6 Chromatographic stationary phases
4.7 Biological medicine
5 Conclusion

Serine octamer as a unique “magic-number” cluster in the gas phase, has been extensively studied by experimentalists and theorists since its discovery in mass spectrometry in 2001. It is characterized by a pronounced preference of homochirality. Interestingly, the chirality of serine octamer can transfer to other molecules through enantioselective substitution reactions. Thus it is suggested that it might be related to the origin of our homochiral world. In this review, all the results and progresses in the formation, structure and chiral signature of serine octamer and substituted serine octamer over the past years are summarized. Different methods, including mass spectrometry with different ionization sources, gas phase H/D exchange, ion mobility, infrared photodissociation spectroscopy, and theoretical calculations are applied for the cluster ions. Different characteristics of the magic cluster are discovered gradually, helping us to have a deep insight into its structure and role in chiral recognition and transmission. However, due to the complexity of the system, it is still a big challenge to understand its true structure, the reason of its performance in homochirality and its role in the origin of biomolecular homochirality.
Contents
1 Introduction
2 Generation of serine octamer
2.1 Electrospray
2.2 Other spray-based ionization method
2.3 Evaporation and sublimation
2.4 Other method
2.5 Mechanism
3 Structural studies
3.1 MS/MS
3.2 Gas-phase H/D exchange
3.3 Ion mobility
3.4 IRPD spectroscopy
3.5 Theoretical calculation
4 Substituted serine octamers
4.1 Substituted by other amino acids
4.2 Substituted by sugars
4.3 Other relative clusters
5 Chiral characteristic
5.1 Enantiometic enrichment and chiral transmission
5.2 Chiral differentiation
5.3 Discussion
6 Conclusion

The increasing greenhouse gas CO₂ emission poses a potential threat to global climate. Electrochemical reduction of CO₂ (CO₂RR) to useful chemical products, an artificial way of carbon recycling, opens up new possibilities of utilization of CO₂ and represents one promising solution that significantly improve the environment and promotes sustainable development. However, it remains a challenge to convert CO₂ to valued products with high efficiency and selectivity while suppressing the H₂ evolution(HER) side reaction. Copper attracts considerable attention currently because it displays interesting electrocatalytic performances for the reduction of CO₂. Progress related to the electrocatalytic reduction of CO₂ in the past few years, and their advantages and disadvantages are reviewed, and thermodynamics and kinetics research of CO₂RR is described,with a focus on the progress in CO₂RR on copper-based electrodes, which includes Cu electrode, Cu metal-organic frameworks electrode and Cu-based electrodes modified by oxidation, alloying, nanocrystalization and surface modification, even if the CO₂ electrocatalytic reduction reaction mechanism remains uncertain. Finally, challenges and future research opportunities for tuning the selective conversion of CO₂ on copper-based catalysts with high efficiency are also discussed.
Contents
1 Introduction
2 Research on the mechanism of electrocatalytic reduction of CO₂
2.1 Thermodynamics and kinetics of electrochemical reduction of CO₂
2.2 Research on the reaction mechanism of electrochemical reduction of CO₂
3 Electrochemical reduction of CO₂ on copper-based electrocatalysts
3.1 Copper electrode
3.2 Copper metal-organic framework electrode
3.3 Modified copper electrode
4 Conclusion

Ternary nickel cobalt manganese cathode materials are one of the most important cathode materials of lithium ion batteries. Ni-Co-Mn ternary materials have much higher power density than LiFePO₄ and lower cost than LiCoO₂, so it is becoming the dominant cathode material for power battery. However, there are still some shortcomings of Ni-Co-Mn ternary materials, such as poor stability and rate performance. In recent years, great efforts have been made to improve the materials through exploring new synthesis method and modifying the materials via doping and coating techniques, and some progress has been achieved. In this paper, the latest progress on the synthesis, doping and coating of Ni-Co-Mn ternary materials are introduced. Furthermore, a perspective for the development tendency of Ni-Co-Mn ternary materials is also made.
Contents
1 Introduction
2 Research progress of preparation
2.1 Solid state method
2.2 Coprecipitation method
2.3 Sol-gel method
2.4 Template method
2.5 Hydrothermal method
3 Research progress of coating and doping
3.1 Coating
3.2 Doping
4 Conclusion

Polybrominated diphenyl ethers(PBDEs) are a group of persistent organic pollutants which have attracted a lot of concern because of their unreasonable use and disposal. Efforts have been paid to developing techniques to rapidly degrade PBDEs, among which the application of zero-valent iron(ZVI) has been found effective because of the reducibility and the ability of activating advanced oxidation processes(AOPs). In this paper, the research on degradation of PBDEs by ZVI are summarized, and the mechanism, kinetics, influencing factors and degradation pathways are reviewed. Although ZVI can be effectively used as direct electron donors for debromination of highly-brominated DEs, the resultant lower brominated DEs are more toxic and generally need further treatment. On the other hand, recent studies indicate ZVI could be used as indirect electron donors by inducing heterogeneous Fenton systems or persulfate(PS) systems to produce reactive oxygen species (ROS), which could degrade lower brominated DEs through ring opening. Therefore, the integration of ZVI and Fenton systems or persulfate systems by constituting two-stage reduction/subsequent oxidation treatment may be a solution for complete ring-opening degradation of highly-brominated DEs. Besides, further research on PBDEs degradation based on ZVI technology is discussed.
Contents
1 Introduction
2 Mechanism of PBDEs reductive debromination by ZVI
2.1 Mechanism of PBDEs reduction by ZVI
2.2 Mechanism of PBDEs reduction by bimetallic systems
2.3 Products and pathways of PBDEs debromination in ZVI reaction system
3 PBDEs reductive debromination by modified-ZVI
3.1 nZVI
3.2 Surface stabilized-nZVI
4 Kinetics of PBDEs reductive debromination
5 Influencing factors of PBDEs reductive debromination
5.1 pH
5.2 Organic matters
5.3 Metal cation
6 Reduction and advanced oxidation of PBDEs based on ZVI
7 Conclusion

One of the major advantages of organic electronics is the solution processability that enables the fabrications of devices by various printing methods. Screen printing which is known as one of the most well-developed printing methods, has been widely applied in the fabrication of electronic devices. This review mainly introduce the composition of screen printing, the tuning factors that could alter the screen printing’s precision and the applications of screen printing in flexible electronic devices, including field-effect transistors, solar cells, and organic light emitting diodes. Finally, the difficulties and challenges of screen printing in printed flexible electronic devices are summurized.
Contents
1 Introduction
2 Screen Printing
3 Applications
3.1 Field effect transistors
3.2 Solar cells
3.3 Organic light emitting diodes
3.4 Other electronic devices
4 Conclusion

Thermoelectric materials are one kind of functional materials, which can realize the direct conversion between electrical energy and thermal energy, and have wide applications in the fields of thermoelectric power generation and refrigeration. Graphene is a two-dimensional carbon material of a single atomic layer with special crystal structure and excellent physical and chemical properties. Many research demonstrate that the excellent electrical performance, large surface and various boundary structures of graphene can optimize the electrical and thermal performance of materials, making graphene of great application potentials in the field of thermoelectrics. In this paper, based on the characteristics of thermoelectric materials and graphene, the relationship of structure and performance of graphene when graphene itself is researched as thermoelectric material is reviewed. The effect of graphene on the microstructure and performances of conventional inorganic thermoelectric materials and conducting polymer thermoelectric materials when graphene is used to form nanocomposites with these thermoelectric materials are also summarized. In addition, the exiting problems and further outlook of the applications of graphene in the field of thermoelectric are discussed.
Contents
1 Introduction
2 Structure and property of graphene
3 Thermoelectric performance of graphene itself
4 Application of graphene in other thermoelectrics as composite
4.1 Nanocomposites of graphene and conventional inorganic thermoelectrics
4.2 Nanocomposites of graphene and conductive polymer thermoelectrics
5 Conclusion

Nanocellulose is drawing extensive concern and attention from the academic and industrial circles due to its unique structure and exceptional properties, and it is the research hotspot in the field of new material and cellulose science. Nanocellulose isolated from lignocellulosic biomass can be divided into two main categories: cellulose nanocrystal (CNC) and cellulose nanofibril (CNF). The preparation methods of CNC and CNF are detailedly summarized in this review, with the focus on some new methods developed in recent years, such as the integrated preparation of CNC and CNF via recoverable organic acid hydrolysis, tuneable preparation of lignin-coated CNC and CNF via AVAP method, high efficiency preparation of CNC and CNF via deep eutectic solvents pretreatment combined with mechanical shearing, as well as the controllable isolation of hydrophilic or hydrophobic CNF by mechanical disintegration in polar microenvironment. Meanwhile, the advantages and shortcomings of the preparation methods are discussed, and the industrialization status of nanocellulose production is introduced as well. Finally, it’s believed that the development of green, effective and sustainable preparation methods will be the main trend for manufacturing nanocellulose.
Contents
1 Introduction
2 Preparation of CNC
2.1 Oxidative degradation
2.2 Ionic liquid treatment
2.3 Solid acid hydrolysis
2.4 Organic acid hydrolysis
2.5 Subcritical water hydrolysis
2.6 AVAP method
3 Preparation of CNF
3.1 Mechanical methods
3.2 Pretreatment methods
4 Industrialization status of nanocellulose
5 Conclusion