Luminescent graphene quantum dots(GQDs) display excellent physicochemical properties, which have ignited tremendous and increasing research interest of researchers from different fields. However, there are still some limitations including low quantum yield, less active sites and unsatisfactory selectivity, which impede their wide applications. As research continues, doping GQDs with heteroatoms has been considered as an effective strategy to address the above problems. In this review, we summarize the preparation methods, physicochemical properties and applications of heteroatom-doped GQDs. There are two kinds of heteroatom-doped GQDs including single-doped GQDs(B, N, S, F, Cl, et al.) and co-doped GQDs(B,N or N,P or N,S co-doping). The introduced heteroatoms changed the charge density and charge distribution of the GQDs, resulting in the enhancement of fluorescence quantum dots, more active sites and the appearances of new physicochemical properties including electrocatalytic activity and intrinsic peroxidase-like catalytic activity. We also give a perspective on the subsequent development and promising applications of heteroatom-doped GQDs.

Contents
1 Introduction
2 Preparation methods
2.1 Preparation of single-doped graphene quantum dots
2.2 Preparation of co-doped graphene quantum dots
3 Physicochemical properties of heteroatom-doped graphene quantum dots
3.1 Photoluminescence
3.2 Electrochemiluminescence
3.3 Catalytic property
4 Applications
4.1 Applications in biological field
4.2 Applications in environmental field
4.3 Applications in energy-related field
5 Conclusion and prospect

There has been a consistent drive to improve the volumetric energy content of liquid fuels to extend the flight distance, flight speed and loading capacity of aerospace vehicles. Compared with conventional jet fuels like aviation kerosene and rocket kerosene, high-density liquid hydrocarbon fuels can provide more propulsion energy and thus are specifically important to promote the performance of volume-limited aerospace vehicles. In this review, the molecular characteristics of high-density fuels and the strategy to synthesize them are first discussed. Then the important progress in synthesis of several typical fuels is summarized, including multi-cyclic and alkyl-diamondoid fuels synthesized by cycloaddition, hydrogenation and isomerization reactions, highly-strained fuels such as cyclopropanated hydrocarbons, quadricyclane and pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane synthesized via cyclopropanation and photoisomerization, high-density biofuels synthesized from cyclic biomass-derived compounds via polymerization, condensation and alkylation reactions, and nano-suspension fuels prepared by surface-modification and stabilization of nanoparticles(aluminum, boron and carbon) in liquid fuels. Specifically, the catalysts and reaction mechanism involved in these processes are highlighted for better controlling the reactions towards higher synthesis efficiency. Also the parameters of typical fuels synthesized using the above-mentioned processes are listed to show the potential for practical application. Finally, an outlook for the synthesis of high-density fuel is given.

Contents
1 Introduction
2 Molecular characteristic of high-density fuels
3 Synthesis of polycyclic hydrocarbon fuels
3.1 Oligomerization reaction
3.2 Hydrogenation reaction
3.3 Isomerization reaction
4 Synthesis of highly strained fuels
4.1 Cyclopropanated hydrocarbons
4.2 Quadricyclane
4.3 Pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane and dimer
5 Synthesis of high-density biofuels
5.1 Pinene-derived fuels
5.2 Lignocellulose-derived fuels
6 Synthesis of nano-fluid fuels
7 Conclusion

Graphene-based aerogels(GA) are three-dimensional macrostructures of graphene with interconnected networks. While inheriting the excellent chemical stability and catalytic performance of graphene, GA exhibits higher specific surface area and excellent conductivity comparing to two-dimensional structure. Because of the superior properties and unique structure, GA are widely applied in catalysis, energy storage and adsorption. This review is expanded around the catalytic reduction performance of GA. Firstly, the preparation methods of GA with different catalytic properties are reviewed, which are classified into four types as graphene aerogels, doped GA, GA composite and doped GA composite. Then the influence on catalytic performance of GA prepared with different methods is introduced in detail. The admirable electrochemical and catalytic performance of GA indicates wide application prospects in fuel cells, dye-sensitized solar cells, microbial electrolysis cells and electrochemical sensors. Finally, the catalysis applications of GA are analysed and outlooked.

Contents
1 Introduction
2 GA and its catalytic properties
3 Synthesis and modification of catalytical active GA
3.1 Preparation of pure GA
3.2 Preparation of doped GA
3.3 Preparation of GA composite
3.4 Preparation of doped GA composite
4 Applications of GA in reduction catalyst
4.1 Applications in positive electrode of fuel cells
4.2 Applications in counter electrode of dye-sensitized solar cells
4.3 Applications in cathode of microbial electrolysis cells
4.4 Applications in hydrogen peroxide electro-chemical sensors
5 Conclusion and outlook

During the bioconversion of lignocellulose, enzymatic hydrolysis of cellulose to produce glucose is a key step. However, it also has become a bottle-neck for effective bioconversion of lignocellulosic biomass to fuels or chemicals. A large amount of works have demonstrated that addition of non-ionic surfactant during enzymatic hydrolysis of pretreated lignocelluloses can effectively improve the cellulose conversion thus reducing the enzyme loading. In this paper, the effects of non-ionic surfactant on enzymatic hydrolysis of pure cellulose and pretreated lignocellulose are reviewed comprehensively. The relationships of the structural features of substrate, hydrolysis conditions and cellulase formulation with the action of surfactant are discussed. Corresponding mechanisms are analyzed in terms of the adsorption of cellulases and the synergism of the cellulase components. However, the current research progress has not clearly elucidated the mechanisms for the effects of non-ionic surfactant on cellulose hydrolysis. It is proposed that to deeply understand the mechanism, further researches should be focused on systematically investigating the relations of substrate structure, hydrolysis conditions with the actions of non-ionic surfactant to the enzymatic hydrolysis of cellulose. Microscopically, the interactive actions and forces between surfactant and substrate, surfactant and cellulase enzymes should be investigated from the atomic and molecular levels. The thermodynamic and kinetic behaviors of enzymatic hydrolysis of cellulose with addition of surfactant should also be illustrated.

Contents
1 Introduction
2 Effects of surfactant on enzymatic hydrolysis of pure cellulose and mechanism
2.1 Factors influencing the action of surfactant
2.2 Mechanism for the action of surfactant on pure cellulose hydrolysis
3 Effects of surfactant on enzymatic hydrolysis of pretreated lignocellulose
3.1 Effects of substrate structural features
3.2 Effects of hydrolysis conditions
4 Mechanisms for the action of surfactant on lignocellulose hydrolysis
4.1 Effects of surfactant on substrate structure
4.2 Effects of surfactant on enzyme stability
4.3 Effects of surfactant on the interaction between enzyme and substrate
5 Conclusion

Porous graphene, which refers to graphene containing nanopores in the two-dimensional basal plane, has aroused great interest. Porous graphene not only retains the excellent intrinsic prosperities of original graphene, but also opens up an energy gap to generate a semiconducting carbon film. The existing nanopores can improve mass transfer efficiency when compared to inactive surface of graphene, thus the porous graphene has more widespread application perspective. Here, the aspects of theoretical base, synthesis methods and applications of porous graphene are reviewed. The synthesis methods mainly include lithography, catalytic etching, chemical vapor deposition, wet etching, carbothermal reduction, solvothermal synthesis and free radical attack. Meanwhile, the application of porous graphene predominantly focuses on fields of energy storage and conversion materials(e.g., fuel cells, supercapacitors, and lithium ion batteries), field effect transistors, chemical sensors, water desalination, molecular sieves and DNA sequencing.

Contents
1 Introduction
2 Theoretical base and properties of porous graphene
3 Synthesis of porous graphene
3.1 Lithography techniques
3.2 Catalytic etching methods
3.3 Chemical vapor deposition method
3.4 Wet etching
3.5 Carbothermal reduction method
3.6 Solvothermal synthesis
3.7 Free radical attack method
3.8 Other methods
4 Applications
4.1 Fuel cell materials
4.2 Supercapacitors electrode materials
4.3 Lithium ion battery electrode materials
4.4 Field effect transistors
4.5 Chemical sensors
4.6 Water desalination
4.7 Molecular sieve
4.8 DNA sequencing
5 Existing problems
6 Conclusion and perspectives

Graphene-like transition metal chalcogenide compounds such as MoS₂, WS₂, MoSe₂, WSe₂ have attracted wide interests because of their unique layer number-dependent bandgap. In particularly, intrinsic WS₂ is a bipolar semiconductor with n-type and p-type electronic transport properties, it is expected to be widely used in electrical circuit, memory, photodetector and photovoltaic devices. Recently, chemical vapor deposition(CVD) technique, in contrast to traditional chemical or physical exfoliation options, is extensively used to prepare large-area two-dimensional transition metal chalcogenide(such as MoS₂, MoSe₂, WS₂ and WSe₂) atomic layers. Although a few review papers about other two-dimensional materials have been published, the detailed introduction for graphene-like WS₂ has been rarely reported. In this review, we summarize the research progress on chemical vapor deposition and related devices of graphene-like WS₂. First, we introduce two growth methods of preparing WS₂ thin films via chemical vapor deposition techniques: two-step growth route and one-step growth route, and then discuss the growth mechanism of the two methods and essential parameters that influence the growth of the WS₂ thin films such as sulfur content, carrier gas composition, reaction temperature and substrate materials. Then, we introduce the research progress of WS₂-based transistors, photoelectric devices and related heterostructures. Finally, we analyze and review possible problems in developing WS₂-related devices.

Contents
1 Introduction
2 Physical Properties of tungsten disulfide thin films
3 Preparation of WS₂ thin films via chemical vapor deposition technique
3.1 Classification of chemical vapor deposition technique
3.2 Mechanism of preparing WS₂ thin films
4 Application of WS₂ thin films in electrical devices
4.1 Field effect transistor
4.2 Photoelectric device
4.3 Heterostructural device
5 Conclusion and outlook

The unique properties of graphene, such as high electrical conductivity, high thermal conductivity and excellent mechanical properties, have made graphene not only a gelator to self-assemble into the graphene hydrogel with extraordinary electromechanical performance, but also a filler to blend with small molecules and macromolecules for the preparation of multifunctional graphene-based hybrid hydrogels, which fully exploits the practical applications of traditional hydrogels. Herein, recent progress in graphene-based hybrid hydrogels has been reviewed and the whole article can be divided into four sections. In the first section, a brief introduction on the development of graphene as well as the significance of the fabrication of graphene-based hydrogels is devoted. In the second section, the graphene-based hybrid hydrogels are roughly divided into three categories: graphene hydrogel, graphene/small molecules and graphene/macromolecules hybrid hydrogels according to their composition. The preparation methods of various hydrogels, as well as the mechanisms of their gelation process and the hydrogels' performance, are also presented. With the presentation of graphene/small molecules hybrid hydrogels, emphasis is given to the development of graphene-based supramolecular hydrogels, while with the presentation of graphene/macromolecules hybrid hydrogels, graphene-based intelligent hydrogels contributed a much higher proportion. In the third section, the applications of graphene-based hybrid hydrogels in supercapacitor, water purification, controlled release drug, microfluidic switch, catalyst support, etc., are introduced respectively. Finally, challenges in the development of graphene-based hydrogels are summarized briefly and future prospect is given as well.

Contents
1 Introduction
2 Categories of graphene-based hydrogels
2.1 Graphene hydrogels
2.2 Graphene/small molecules hybrid hydrogels
2.3 Graphene/macromolecules hybrid hydrogels
3 Applications of graphene-based hydrogels
3.1 Supercapacitor
3.2 Water purification
3.3 Drug-controlled release
3.4 Microfluidic switch
3.5 Catalyst support
3.6 Others
4 Conclusion

In recent years, nanomaterials have made an important impact on diverse science, engineering, and commercial sectors due to their high catalysis, low cost, and good stability. Acting as a class of 'zero-dimensional' carbon nanomaterials, carbon dots(CDs) possess unique optical properties of high photostability against photobleaching, tunable excitation and emission wavelength, as well as low cytotoxicity and good biocompatibility. Therefore, CDs have become a hot subject of carbon nanomaterial in the past decade, not only for its unique properties but also for its applications in various fields such as bioimaging, biolabeling, sensors, photocatalysis, solar cells, light-emitting element and so on. This article reviews the different synthetic methodologies(including two classes: top-down and bottom-up) to achieve good performance of CDs. At the same time, the applications of CDs are also reviewed in the article.

Contents
1 Introduction
2 Synthesis methods of carbon dots
2.1 Top-down methods
2.2 Bottom-up methods
3 Applications of carbon dots
3.1 Bioimaging and Biolabeling
3.2 Sensors
3.3 Photocatalysis
3.4 Solar cells
3.5 Light-emitting diodes
4 Conclusion

Poly(3, 4-ethylened ioxythiophene): poly(styrene sulfonicacid)(PEDOT:PSS) has been widely investigated as transparent conductive films due to its superior conductivity and transmittance. Films made from PEDOT:PSS have high optical transparency and excellent electrical conductivity; therefore they can be directly used as transparent electrodes or hole transport layers for organic photovoltaics(OPVs), organic field effect transistors(OFETs), organic light-emitting diodes(OLEDs), etc. Owing to the superior optoelectronic performance and excellent flexibility, they are promising alternative candidates for indium tin oxide(ITO) transparent electrodes. Spin coating is a ubiquitous method for film formation because of the facility and simplicity. However, wastage of raw materials and difficulty in large-area patterning severely restrict the extensive application of spin coating in film preparation. In contrast, inkjet printing is currently the most promising technology for the film forming due to its unique advantages, such as solution-processibility, material saving, low cost and compatibility with roll-to-roll technique. Furthermore, it is capable of rapidly and efficiently preparing large-area thin films with various patterns on different substrates, holding great promise in organic electronics especially for flexible electronic devices. This review summarizes recent advances in depositing PEDOT:PSS films via inkjet printing, and discusses further the prospects and challenges posed in this research field.

Contents
1 Introduction
2 Inkjet printing of PEDOT:PSS films
2.1 Inkjet printing
2.2 Inkjet-printed PEDOT:PSS films
2.3 Inkjet-printed hybrid electrodes
3 Inkjet-printed PEDOT:PSS films for optoelectronic devices
3.1 Organic field effect transistors(OFET)
3.2 Organic photovoltaics(OPV)
3.3 Organic light-emitting diodes(OLED)
3.4 Organic memory devices
4 Conclusion

In recent years, the development of codelivery systems based on combination strategies has provided an effective approach for reducing side effect and retaining drug bioactivity of anti-cancer drugs. Cancer is one of the most serious diseases endangering human health. There are some significant changes between normal tissues and cancerous tissues, and such changes have motivated researchers to design multiple intelligent hydrogel-based dual drug carriers for drug controlled release. Meanwhile, with the development of effective treatment, modulating multiple targets simultaneously can be achieved through a combination of anticancer drug and biological factor in hydrogel. The dual-drug controlled release from hydrogel is also realized. In the review, the recent advance on the intelligent hydrogel-based dual drug delivery system are summarized, which are classified referring to the mechanism of hydrogel loaded dual drugs, the release principles of drugs and the means of combination of drugs. In addition, some personal perspectives on this field are also presented.

Contents
1 Introduction
2 Intelligent hydrogel-based dual drug delivery carriers
2.1 Temperature-sensitive carriers
2.2 pH sensitive carriers
2.3 Redox sensitive carriers
3 The means of drug combination in hydrogel
3.1 Combination of two anticancer drugs
3.2 Combination of anticancer drug and growth factor
3.3 Combination of anticancer drug and gene
4 Conclusion

Enzymes play an increasingly important role in many industrial fields such as food, feed, cosmetics and pharmacy. However, enzymes are susceptible to the external environment such as pH and temperature, and the practical operational conditions for enzymes are dramatically different from their physiological conditions, so most enzymes are not sufficiently stable and they are prone to lose their activity under practical operation. This has largely limited their wider industrial application. Currently, directed evolution, glycosylation and chemical modification have been extensively used to improve the enzyme stability, activity and expand the substrate scope. Among them, directed evolution, through which mutants bearing desired properties are obtained by gene diversification manipulation and library screening in vitro, has become a popular technique for enzyme modification. In practical application, medium engineering, immobilization and multi-enzyme complexes have been widely adopted to enhance the catalytic efficiency of enzyme. Among them, multi-enzyme complexes have gained special attention recently due to its substrate channeling effect which can significantly increase the reaction rate for cascade enzymatic reactions. The recent progress of enzyme application is introduced. Then, the popular techniques including directed evolution, glycosylation and chemical modification for the improvement of enzyme properties are reviewed. At last, the techniques including medium engineering, immobilization and multi-enzyme complex for the catalytic engineering of enzyme in practical application are summarized.

Contents
1 Introduction
2 Current application of enzymes
3 Enzyme modification
3.1 Directed evolution
3.2 Glycosylation
3.3 Chemical modification
4 Catalytic engineering of enzymes
4.1 Medium engineering
4.2 Immobilization
4.3 Multi-enzyme complex
5 Conclusion

Ammonium transport proteins widely exist in various life forms including bacteria, fungi, plants, animals, etc. The transport of NH₃/NH₄⁺ through an ammonium transport protein has been widely studied. However, the issue that the ionic NH₄⁺ or the electrically neutral NH₃ species truly goes through the hydrophobic pore of an ammonium transport protein remains controversial. This review surveys the progress in studying on the transport mechanisms of NH₃/NH₄⁺ through several typical ammonium transport proteins. The main mechanisms include the single transport of NH₃ or NH₄⁺, and the cooperative transport of NH₃ and H⁺, etc.

Contents
1 Introduction
2 NH₃ transport mechanism
3 NH₄⁺ transport mechanism
4 Cooperative transport of NH₃ and H⁺
5 Other transport mechanisms
6 Conclusion

Heavy metals pollution has become an environmental and public health concern all over the world, especially in China. Activated carbon, carbon nano-tubes and graphene are used to remove heavy metal ions from aqueous solutions due to their large surface area, high adsorption capacity and environmentally benign nature. Whereas, carbon-based materials assembled on functional groups possess excellent adsorption capacity for metal ions. In this study, the modification methods of activated carbon, carbon nano-tubes, graphene and biochar are reviewed, mainly including thiol-functionalization and amino-functionalization. The applications of functional carbon-based materials for heavy metal ions removal are also summarized. The removal efficiency and influential factors of heavy metal ions removal by different functionalized carbon-based materials are discussed in detail. In addition, the outlook and suggestion of heavy metal ions removal by functionalized carbon-based materials are presented.

Contents
1 Introduction
2 Preparation of functional carbon-based materials for removal of heavy metals from aqueous solution
2.1 Functional activated carbon
2.2 Functional graphene
2.3 Functional carbon nanotubes
2.4 Functional biochar
3 The influencing factors of heavy metal removal from water by functional carbon-based materials
3.1 The properties of composite materials
3.2 Environmental conditions
4 The application of functional carbon-based materials
5 Conclusion and outlook

n-Butane selective oxidation to maleic anhydride on VPO catalyst is the only industrialized selective oxidation reaction of light alkanes. The catalytic mechanism and reaction network are introduced. The research progress of reaction kinetics at home and abroad is reviewed. Based on continuous knowledge of reaction mechanism and the integrity of the kinetics model, the development of reaction kinetics is divided into three periods for the first time, that is, the exploration period, the forming period and the further developing period. The features and the typical models of every period are introduced. The feature of the exploration period is that the model only takes reactants' adsorption behavior on the catalyst surface into account. The feature of the forming period is that the product inhibition on the reaction is taken fully into account. The feature of the further developing period is that the oxidation degree of the catalyst with time changes and conversion among different forms of oxygen is brought into the dynamic model. Finally, we point out that the research of n-butane selective oxidation reaction kinetics will focus on the research of the interaction between kinetics and transfer process in the perspective of space-time multiscale.

Contents
1 Introduction
2 Catalytic mechanism
3 Reaction network
3.1 Triangle reaction network
3.2 Reaction network involving furan route
3.3 Reaction network involving alkoxide route and furan route
4 Reaction kinetics
4.1 The exploration period
4.2 The forming period
4.3 The further developing period
5 Conclusion