Two-dimensional silicon nanomaterials for optoelectronics

Silicon nanomaterials have been of immense interest in the last few decades due to their remarkable optoelectronic responses,elemental abundance,and higher biocompatibility.Two-dimensional silicon is one of the new allotropes of silicon and has many compelling properties such as quantum-confined photoluminescence,high charge carrier mobilities,anisotropic electronic and magnetic response,and non-linear optical properties.This review summarizes the recent advances in the synthesis of two-dimensional silicon nanomaterials with a range of structures(silicene,silicane,and multilayered silicon),surface ligand engineering,and corresponding optoelectronic applications.

Recent developments in nanofiltration membranes based on nanomaterials

Nanofiltration membranes are the core elements for nanofiltration process. The chemical structures and physical properties of nanofiltration membranes determine water permeability, solute selectivity, mechanical/thermal stability, and antifouling properties, which greatly influence the separation efficiency and operation cost in nanofiltration applications. In recent years, a great progress has been made in the development of high performance nanofiltration membranes based on nanomaterials. Considering the increasing interest in this field, this paper reviews the recent studies on the nanofiltration membranes comprising various nanomaterials, including the metal and metal oxide nanoparticles, carbon-based nanomaterials, metal–organic frameworks(MOFs), water channel proteins, and organic micro/nanoparticles. Finally, a perspective is given on the further exploitation of advanced nanomaterials and novel strategy for fabricating nano-based nanofiltration membranes. Moreover,the development of precision instruments and simulation techniques is necessary for the characterization of membrane microstructure and investigation of the separation and antifouling mechanism of nanofiltration membranes prepared with nanomaterials.

Two-dimensional material separation membranes for renewable energy purification, storage, and conversion

The current energy crisis has prompted the development of new energy sources and energy storage/conversion devices. Membranes, as the key component, not only provide enormous separation potential for energy purification but also guarantee stable and high-efficiency operation for rechargeable batteries and fuel cells. Remarkably, two-dimensional(2D) material separation membranes have attracted intense attention on their excellent performance in energy field applications, owing to high mechanical/chemical stability, low mass transport resistance, strict sizeexclusion, and abundant modifiable functional groups. In this review, we concentrate on the recent progress of 2D membrane and introduce 2D membranes based on graphene oxide(GO), MXenes, 2D MOFs, 2D COFs, and 2D zeolite nanosheets, which are applied in membrane separation(H2 collection and biofuel purification) and battery separators(vanadium flow battery, Li–S battery, and fuel cell). The mass transport mechanism, selectivity mechanism, and modification methods of these 2D membranes are stated in brief, mainly focusing on interlayer dominant membranes(GO and MXenes) and pore dominant membranes(MOFs, COFs, and zeolite nanosheets). In conclusion, we highlight the challenges and outlooks of applying 2D membranes in energy fields.

Two-dimensional MXene hollow fiber membrane for divalent ions exclusion from water

Two-dimensional material membranes with fast transport channels and versatile chemical functionality are promising for molecular separation.Herein,for the first time,we reported design and engineering of two-dimensional Ti_(3)C_(2)Tx MXene(called transition metal carbides and nitrides)membranes supported on asymmetric polymeric hollow fiber substrate for water desalination.The membrane morphology,physicochemical properties and ions exclusion performance were systematically investigated.The results demonstrated that surface hydrophilicity and electrostatic repulsion and size sieving effect of interlayer channels synergistically endowed the MXene hollow fiber membrane with fast water permeation and efficient rejection of divalent ions during nanofiltration process.

Two-dimensional graphitic carbon nitride for membrane separation

Recent years,membrane separation technology has attracted significant research attention because of the efficient and environmentally friendly operation.The selection of suitable materials to improve the membrane selectivity,permeability and other properties has become a topic of vital research relevance.Two-dimensional(2D)materials,a novel family of multifunctional materials,are widely used in membrane separation due to their unique structure and properties.In this respect,as a novel 2D material,graphitic carbon nitride(g-C_(3)N_(4))have found specific attention in membrane separation.This study reviews the application of carbon nitride in gas separation membranes,pervaporation membranes,nanofiltration membranes,reverse osmosis membranes,ion exchange membranes and catalytic membranes,along with describing the separation mechanisms.

Engineer Nanoscale Defects into Selective Channels:MOF-Enhanced Li^(+) Separation by Porous Layered Double Hydroxide Membrane

Two-dimensional(2D)membrane-based ion separation technology has been increasingly explored to address the problem of lithium resource shortage,yet it remains a sound challenge to design 2D membranes of high selectivity and permeability for ion separation applications.Zeolitic imidazolate framework functionalized modified layered double hydroxide(ZIF-8@MLDH)composite membranes with high lithium-ion(Li^(+)) permeability and excellent operational stability were obtained in this work by in situ depositing functional ZIF-8 nanoparticles into the nanopores acting as framework defects in MLDH membranes.The defect-rich framework amplified the permeability of Li^(+),and the site-selective growth of ZIF-8 in the framework defects bettered its selectivity.Specifically speaking,the ZIF-8@MLDH membranes featured a high permeation rate of Li^(+) up to 1.73 mol m^(−2) h^(−1) and a desirable selectiv-ity of Li^(+)/Mg^(2+) up to 31.9.Simulations supported that the simultaneously enhanced selectivity and permeability of Li+are attributed to changes in the type of mass transfer channels and the difference in the dehydration capacity of hydrated metal cations when they pass through nanochannels of ZIF-8.This study will inspire the ongoing research of high-performance 2D membranes through the engineering of defects.

Photocatalytic applications and modification methods of two-dimensional nanomaterials:a review

Due to its unique electronic structure and special size effect,two-dimensional(2D)nanomaterials have shown great potential far beyond bulk materials in the field of photocatalysis.How to deeply explore the photocatalytic mechanism of 2D nanomaterials and design more efficient 2D semiconductor photocatalysts are research hotspots.This review provides a comprehensive introduction to typical 2D nanomaterials and discusses their current application status in the field of photocatalysis.The effects of material properties such as band structure,morphology,crystal face structure,crystal structure and surface defects on the photocatalytic process are discussed.The main modification methods are highlighted,including doping,noble metal deposition,heterojunction,thickness adjustment,defect engineering,and dye sensitization in 2D material systems.Finally,the future development of 2D nanomaterials is prospected.It is hoped that this paper can provide systematic and useful information for researchers engaged in the field of photocatalysis.

Polymer-based membranes for solvent-resistant nanofiltration:A review

Separation of organic mixture is an inevitable process in most modern industrial processes. In the quest for a more sustainable and efficient separation, solvent-resistant nanofiltration(SRNF) has emerged as a promising answer. This is because SRNF is a membrane-based process which offers the key advantages of high efficacy and low energy intensity separation. In particular, polymer-based membranes can offer compelling opportunities for SRNF with unprecedented cost-effectiveness. As a result, intensive research efforts have been devoted into developing novel polymer-based membranes with solvent-resistant capacities as well as exploring potential applications in different types of industries. In this review, we aim to give an overview of the recent progress in the development of the state-of-the-art polymer-based membranes for SRNF in the first section. Emerging nanomaterials for mixed matrix and thin film nanocomposite membranes are also covered in this section. This is followed by a discussion on the current status of membrane engineering and SRNF membrane commercialization. In the third section, we highlight recent efforts in adopting SRNF for relevant industrial applications such as food, bio-refinery, petrochemical, fine chemical and pharmaceutical industries followed by separations of enantiomers in stereochemistry, homogeneous catalysis and ionic liquids. Finally, we offer a perspective and provide deeper insights to help shape future research direction in this very important field of SRNF.

Emerging R&D on membranes and systems for water reuse and desalination

Sustainable production of clean water is a global challenge.While we firmly believe that membrane technologies are one of the most promising solutions to tackle the global water challenges,one must reduce their energy consumption and fouling propensity for broad sustainable applications.In addition,different membranes face various challenges in their specific applications during long-term operations.In this short review,we will summarize the recent progresses in emerging membrane technologies and system integration to advance and sustain water reuse and desalination with discussion on their challenges and perspectives.

Combination-based nanomaterial designs in single and double dimensions for improved electrodes in lithium ion-batteries and faradaic supercapacitors

In the past decade, researchers in the fields of energy production have concentrated on the improvement of new energy storage devices. Lithium-ion batteries(LIBs) and faradaic supercapacitors(FSs) have attracted special attention as a result of the rapid development of new electrode nanomaterials, especially hybrid nanomaterials, which can meet the increasingly higher requirements for future energy, such as the capability to deliver high-power performance and an extremely long life cycle. In these hybrid nanostructures, a series of synergistic effects and unique properties arising from the combination of individual components are a major factor leading to improved charge/discharge capability, energy density, and system lifetime. This paper describes the most recent progress in the growth of hybrid electrode materials for LIBs and FSs systems, focusing on the combination of zero-dimensional(0 D), one-dimensional(1 D), two-dimensional(2 D), and three-dimensional(3 D) nanomaterials, respectively.

Using cell membrane chromatography and HPLC-TOF/MS method for in vivo study of active components from roots of Aconitum carmichaeli

An offline two-dimensional system combining a rat cardiac mascle cell membrane chromatography time-of-flight mass spectrometry （CMC-TOF/MS） with a high performance liquid chromatography time-of-flight mass spectrometry （HPLC-TOF/MS） was established for investigating the parent components and metabolites in rat urine samples after administration of the roots of Aconitum carmichaeli. On the basis of the analysis of the first dimension, retention components of the urine sample were collected into 30 fractions （one fraction per minute）. Then offline analysis of the second dimension was carried out. 34 compounds including 24 parent alkaloids and 10 potential metabolites were identified from the dosed rat urine, and then binding affinities of different compounds on cell membranes were compared and influences of some functional groups on activity were estimated with the semi-quantification and curve fitting method. As a result, binding affinities decreased along with the process of deacylation, debenzoylation and demethylation, which may be related to the alleviation of toxicity in the procedure of herb processing or metabolism. Moreover, some minor components in rat urine （Songorine, 14-benzoylneoline, Deoxyaconitine, etc. ） exerted relatively strong affinity on cell membranes are worth exploring. The results delivered by the system suggest that the CMC can be applied to in vivo study.

High efficiency hydrogen purification through P2C3 membrane:A theoretical study

It is critical to design an effective two-dimensional membrane for hydrogen purification from the mixed gas, due to its wide range of scientific and industrial applications. In this work, we investigate the hydrogen separation performance of P2C3 membranes by density functional theory and molecular dynamics simulations. The results show that the energy barrier of the H2 molecule through the P2C3 film is only 0.18 e V, while the energy barriers of the CO, N2, CO2, and CH4 molecules are 0.77 eV, 0.87 eV, 0.52 eV, and 1.75 eV, respectively. In addition, the P2C3 film has high H2 selectivity toward other gas molecules and high H2 permeability at room temperature. Under 6% tensile strain, 82% hydrogen molecules pass through the film with a H2 permeance of 2.22 × 107 gas permeance unit(GPU), while other molecules cannot across the membrane at all. Therefore, the P2C3 membrane is an excellent material for hydrogen purification.

A review of membrane distillation enhancement via thermal management and molecular transport through nanomaterial-based membranes

Low-energy,high-efficiency desalination techniques are important because of the critical water-energy nexus.In particular,membrane distillation has great potential to harness low-grade and renewable energy sources.Composite membranes using micro-and nanomaterials have new capabilities and characteristics.This review focuses on the most recent developments and potential capabilities in membrane distillation systems from the perspective of nanomaterial enhancements,thermal management,and water transport.Self-heating nanomaterial membrane distillations using permeable composite membranes with significant photothermal or Joule-heating conversion capabilities enable macroscale thermal management and mitigate temperature polarization effects.Modifying the membrane structure and its interaction with water can accelerate water transport and evaporation,improving distillation at the microscopic level.This is expected to provide directions for the fabrication and manipulation of novel micro-and nanocomposite membranes for distillation processes at various levels,and enhance their applications.

Two-dimensional Cu-porphyrin nanosheet membranes for nanofiltration

A kind of two-dimensional(2D)metal-organic framework(MOF)material,Cu-meso-tetrakis(4-carboxyphenyl)porphine(Cu-TCPP)nanosheets with wrinkled and flat morphologies are used as building blocks to assemble membranes by vacuum filtration(VF)and electrophoretic deposition(EPD)as energy-efficient nanofiltration(NF)membranes to remove dyes from water.Since the nanosheets with wrinkled structure can provide additional water transport channels,thereby increasing the water permeance,in the premise of a high rejection(>97.0%)for the dye brilliant blue G(BBG)(1.60 nm×1.90 nm),the water permeance of the membrane assembled by the wrinkled nanosheets(~1170 nm)is about 4 times that of the membrane assembled by the flat nanosheets(~530 nm),reaching 16.39 L·m^(−2)·h^(−1)·bar^(−1).Additionally,the use of the relatively flat nanosheets and the membrane preparation method of electrophoretic deposition is more conducive to stack nanosheets orderly and reduce defects.Therefore,the water permeance of the membrane prepared by EPD(~1170 nm)with flat nanosheets is about twice that of the membrane prepared by VF(~530 nm),achieving 9.40 L·m^(−2)·h^(−1)·bar^(−1)with similar rejection(>97.0%)of dye evans blue(EB)(3.10 nm×1.20 nm).Furthermore,these membranes still exhibit good separation performance at high pressure of 0.6 MPa.Nanosheets with diverse structures and various membrane fabrication processes provide new directions for the separation performance optimization of 2D MOF materials for water purification.

Two-dimensional layered nanomaterials fortumor diagnosis and treatment

With the evolution of nanomedicine,the past decades witnessed diversified nanomaterials as marvelous antitumor tools ushering in a new era of tumor diagnosis and treatment.Among them,two-dimensional layered nano-material as an emerging class of nanomaterials has one dimension less than 100 nm,showing a high specific area and the thinnest sheet-like structure(Liu S,Pan X,Liu H.Twodimensional nanomaterials for photothermal therapy.Angew Chem Int Ed 2020;59:5890–900).The discovery of graphene drove the exploration of various new two-dimensional layered nanomaterials for tumor diagnosis and treatment including graphene-based nanomaterials,black phosphorus(BP),transition metal dichalcogenides(TMDs),layered double hydroxides(LDHs),and bismuth oxyhalides(BiOX,X=F,Cl,Br,I)(Ma H,Xue MQ.Recent advances in the photothermal applications of two-dimensional nanomaterial:photothermal therapy and beyond.J Mater Chem 2021;9:17569).On the one hand,they exhibit strong near-infrared(NIR)absorption and the capacity of optimizing corresponding properties by adjusting the crystal structure.On the other hand,they own unique strengths such as fantastic physicochemical properties(graphene-based nanomaterials),high loading capacity(BP),distinct phase-dependent optical properties(TMDs),a specific chemical response to the tumor microenvironment(LDHs),and large X-ray attenuation coefficient(BiOX).Herein,we briefly introduce three typical two-dimensional layered nanomaterials,their prospects and future research priorities in tumor diagnosis and treatment are concluded.

石墨相氮化碳在聚合物电解质膜中的研究进展

燃料电池因具有能源转换效率高、近零污染、低噪音等优点受到广泛关注。聚合物电解质膜作为燃料电池的重要组成部件之一,其性能优劣决定了电池的实际表现。为解决聚合物电解质膜在稳定性及离子传导率方面存在的不足,无机纳米材料掺杂作为常规的改性手段应用到聚合物电解质膜材料中。近年来,石墨相氮化碳(g-C_(3)N_4)因其独特的结构特征和优秀的物化性能,被广泛应用于聚合物电解质膜材料的制备和改性。本文主要综述了g-C_(3)N_4的结构和性质,总结了g-C_(3)N_4基复合膜的制备方法,重点对目前g-C_(3)N_4在聚合物电解质膜中的研究和应用情况进行了综述,展示了其在聚合物电解质膜改性方面的重要成果,并对其在该领域未来的发展做出展望。

Nano-alumina@cellulose-coated separators with the reinforcedconcrete-like structure for high-safety lithium-ion batteries

Separators play a critical role in the safety and performance of lithium-ion batteries.However,commercial polyolefin separators are limited by their poor affinity with electrolytes and low melting points.In this work,we constructed a reinforced-concrete-like structure by homogeneously dispersing nano-Al_(2)O_(3) and cellulose on the separators to improve their stability and performance.In this reinforcedconcrete-like structure,the cellulose is a reinforcing mesh,and the nano-Al_(2)O_(3) acts as concrete to support the separator.After constructing the reinforced-concrete-like structure,the separators exhibit good stability even at 200℃(thermal shrinkage of 0.3%),enhanced tensile strain(tensile stress of 133.4 MPa and tensile strains of 62%),and better electrolyte wettability(a contact angle of 6.5°).Combining these advantages,the cells with nano-Al_(2)O_(3)@cellulose-coated separators exhibit stable cycling performance and good rate performance.Therefore,the construction of the reinforced-concretelike structure is a promising technology to promote the application of lithium-ion batteries in extreme environments.

Application of different fiber structures and arrangements by electrospinning in triboelectric nanogenerators

In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs have been reported,but there is a lack of deep analysis of the designing method from microstructure,limiting the creative of new ES-based TENGs.Most TENGs use polymer materials to achieve corresponding design,which requires structural design of polymer materials.The existing polymer molding design methods include macroscopic molding methods,such as injection,compression,extrusion,calendering,etc.,combined with liquid-solid changes such as soluting and melting;it also includes micro-nano molding technology,such as melt-blown method,coagulation bath method,ES method,and nanoimprint method.In fact,ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation.At present,these characteristics have not been reviewed.Therefore,in this paper,we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method.Based on the rich microstructure research results in the field of ES,much more new types of TENGs can be designed in the future.

Ultrathin two-dimensional medium-entropy oxide as a highly efficient and stable electrocatalyst for oxygen evolution reaction

Medium-entropy oxides(MEOs)with broad compositional tunability and entropy-driven structural stability,are receiving booming attention as a promising candidate for oxygen evolution reaction(OER)electrocatalysts.Meanwhile,ultrathin two-dimensional(2D)nanostructure offers extremely large specific surface area and is therefore considered to be an ideal catalyst structure.However,it remains a grant challenge to synthesize ultrathin 2D MEOs due to distinct nucleation and growth kinetics of constituent multimetallic elements in 2D anisotropic systems.In this work,an ultrathin 2D MEO(MnFeCoNi)O was successfully synthesized by a facile and low-temperature ionic layer epitaxy method.Benefiting from multi-metal synergistic effects within ultrathin 2D nanostructure,this 2D MEO(MnFeCoNi)O revealed excellent OER electrocatalytic performance with a quite low overpotential of 117 mV at 10 mA·cm^(-2) and an impressive stability for 120 h continuous operation with only 6.9%decay.Especially,the extremely high mass activity(5584.3 A·g^(-1))was three orders of magnitude higher than benchmark RuO_(2)(3.4 A·g^(-1))at the same overpotential of 117 mV.This work opens up a new avenue for developing highly efficient and stable electrocatalysts by creating 2D nanostructured MEOs.

Integrating single Ni site and PtNi alloy on two-dimensional porous carbon nanosheet for efficient catalysis in fuel cell

The performance of catalyst depends on the intrinsic activity of active sites and the structural characteristics of the support.Here,we simultaneously integrate single nickel(Ni)sites and platinum-nickel(PtNi)alloy nanoparticles(NPs)on a two-dimensional(2D)porous carbon nanosheet,demonstrating remarkable catalytic performance in the oxygen reduction reaction(ORR).The single Ni sites can activate the oxygen molecules into key oxygen-containing intermediate that is further efficiently transferred to the adjacent PtNi alloy NPs and rapidly reduced to H2O,which establishes a relay catalysis between active sites.The porous structure on the carbon nanosheet support promotes the transfer of active intermediates between these active sites,which assists the relay catalysis by improving mass diffusion.Remarkably,the obtained catalyst demonstrates a half-wave potential of up to 0.942 V,a high mass activity of 0.54 A·mgPt^(−1),and negligible decay of activity after 30,000 cycles,which are all superior to the commercial Pt/C catalysts with comparable loading of Pt.The theoretical calculation results reveal that the obtained catalyst with defect structure of carbon support presents enhanced relay catalytic effect of PtNi alloy NPs and single Ni sites,ultimately realizing improved catalytic performance.This work provides valuable inspiration for developing low platinum loading catalyst,integrating single atoms and alloy with outstanding performance in fuel cell.