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.

Recent advances in photodynamic therapy based on emerging two-dimensional layered nanomaterials

Photodynamic therapy(PDT)is a promising non-invasive therapy approach for various diseases including malignant tumor.The process of PDT involves three interrelated aspects,namely photosensitizer(PS),light source,and oxygen,among which PS is the decisive factor that determines its anticancer efficiency.There exist some defects in currently applied PDT,such as inadequate production of reactive oxygen species(ROS),poor penetration of exciting light,insufficient oxygen supply,and nonselective distribution of PS.With unique physicochemical and optical properties,two-dimensional nanomaterials(2DNMs)have aroused great interest in biomedical fields.2DNMs-based PDT is promising to significantly improve antitumor efficacy compared to conventional PDT.In this review,we will firstly introduce the underlying mechanism of PDT and how 2DNMs are absorbed and distribute inside tumor cells.After that,we will not only illustrate how 2DNMs-based PDT can enhance tumor-killing efficacy and minimize side-effects through conquering the above-mentioned defects of conventional PDT and the preparation process of 2DNMs,but also elaborate recent advances about 2DNMs-based PDT.Lastly,we will summarize the challenges and future prospects of 2DNMs-based PDT.

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.

Room temperature synthesis of two-dimensional multi layer magnets based on α-Co^(Ⅱ) layered hydroxides

Research on two-dimensional(2D) materials is one of the most active fields in materials science and nanotechnology. Among the members of the 2D family, layered hydroxides(LHs) represent an exceptional case of study due to their unparalleled chemical versatility which allows the modulation of their physicochemical properties at will. Nowadays, LHs based on earth-abundant metals are key materials in the areas of energy storage and conversion, hybrid materials or magnetism. α-Co hydroxides(Simonkolleite-like structures) are promising phases with tuneable electronic and magnetic properties by ligand modification. However, even in the simple case of α-Co^(Ⅱ) hydroxychlorides, the preparation of well-defined large 2D crystals is not straightforward, hindering the development of fundamental studies. Herein, we present the synthesis of 2D hexagonal crystals with outstanding sizethickness relationship(diameter > 5 μm and thickness of 20 ± 7 nm) by a simple homogeneous synthesis taking place at room temperature. In structural terms, no differences are observed between our layered materials and those obtained hydrothermally. However, dynamic susceptibility measurements alert about different arrangements of the magnetic sublattices, which have been rationalized with structural DFT calculations. This work provides an extremely easy bottom-up method to obtain high-quality 2D crystals based on α-CoIIhydroxides,paving the way for the development of fundamental studies and applications.

Transforming a Two-Dimensional Layered Insulator into a Semiconductor or a Highly Conductive Metal through Transition Metal Ion Intercalation

Atomically thin two-dimensional(2D) materials are the building bricks for next-generation electronics and optoelectronics, which demand plentiful functional properties in mechanics, transport, magnetism and photoresponse.For electronic devices, not only metals and high-performance semiconductors but also insulators and dielectric materials are highly desirable. Layered structures composed of 2D materials of different properties can be delicately designed as various useful heterojunction or homojunction devices, in which the designs on the same material(namely homojunction) are of special interest because preparation techniques can be greatly simplified and atomically seamless interfaces can be achieved. We demonstrate that the insulating pristine ZnPS_3, a ternary transition-metal phosphorus trichalcogenide, can be transformed into a highly conductive metal and an n-type semiconductor by intercalating Co and Cu atoms, respectively. The field-effect-transistor(FET) devices are prepared via an ultraviolet exposure lithography technique. The Co-ZnPS_3 device exhibits an electrical conductivity of 8 × 10^(4) S/m, which is comparable to the conductivity of graphene. The Cu-ZnPS_3 FET reveals a current ON/OFF ratio of 1-05 and a mobility of 3 × 10^(-2 )cm^(2)·V^(-1)·s^(-1). The realization of an insulator, a typical semiconductor and a metallic state in the same 2D material provides an opportunity to fabricate n-metal homojunctions and other in-plane electronic functional devices.

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.

Vertical two-dimensional non-hydrostatic pressure model with single layer

The vertical two-dimensional non-hydrostatic pressure models with multiple layers can make prediction more accurate than those obtained by the hydrostatic pres- sure assumption. However, they are time-consuming and unstable, which makes them unsuitable for wider application. In this study, an efficient model with a single layer is developed. Decomposing the pressure into the hydrostatic and dynamic components and integrating the x-momentum equation from the bottom to the free surface can yield a horizontal momentum equation, in which the terms relevant to the dynamic pressure are discretized semi-implicitly. The convective terms in the vertical momentum equation are ignored, and the rest of the equation is approximated with the Keller-box scheme. The velocities expressed as the unknown dynamic pressure are substituted into the continuity equation, resulting in a tri-diagonal linear system solved by the Thomas algorithm. The validation of solitary and sinusoidal waves indicates that the present model can provide comparable results to the models with multiple layers but at much lower computation cost.

Synergistic cerium doping and MXene coupling in layered double hydroxides as efficient electrocatalysts for oxygen evolution

Oxygen evolution reaction(OER) is a bottle-neck process in many sustainable energy conversion systems due to its sluggish kinetics.The development of cost-effective yet efficient electrocatalysts towards OER is highly desirable but still a great challenge at current stage.Herein,a new type of hybrid nanostructure,consisting of two-dimensional(2D) Cerium-doped NiFe-layered double hydroxide nanoflakes directly grown on the 2D Ti3C2Tx MXene surface(denoted as NiFeCe-LDH/MXene),is designed using a facile insitu coprecipitation method.The resultant NiFeCe-LDH/MXene hybrid presents a hierarchical nanoporous structure,high electrical conductivity and strong interfacial junction because of the synergistic effect of Ce doping and MXene coupling.As a result,the hybrid catalyst exhibits an excellent catalytic activity for OER,delivering a low onset overpotential of 197 mV and an overpotential of 260 mV at a current density of 10 mA·cm-2 in the alkaline medium,much lower than its pure LDH counterparts and IrO2 catalyst.Besides,the hybrid catalyst also displays a fast reaction kinetics and a remarkable stable durability.Further theoretic studies using density function theory(DFT) methods reveal that Ce doping could effectively narrow the bandgap of NiFe-LDH and reduce the overpotential in OER process.This work may shed light on the exploration of advanced electrocatalysts for renewable energy conversion and storage systems.

Layered double hydroxide(LDH)-based materials:A mini-review on strategies to improve the performance for photocatalytic water splitting

The high energy demand we currently face in society and the subsequent large consumption of fossil fuels cause its depletion and increase the pollution levels.The quest for the production of clean energy from renewable and sustainable sources remains open.The conversion of solar energy into hydrogen via the water-splitting process,assisted by pho tores pons ive semiconductor catalysts,is one of the most promising technologies.Significant progress has been made on water splitting in the past few years and a variety of photocatalysts active not only under ultra-violet(UV) light but especially with the visible part of the electromagnetic spectrum have been developed.Layered double hydroxides(LDH)-based materials have emerged as a promising class of nanomaterials for solar energy applications owing to their unique layered structure,compositional flexibility,tunable bandgaps,ease of synthesis and low manufacturing costs.This review covers the most recent research dedicated to LDH materials for photocatalytic water-splitting applications and encompasses a range of synthetic strategies and post-modifications used to enhance their performance.Moreover,we provide a thorough discussion of the experimental conditions crucial to obtaining improved photoactivity and highlight the impact of some specific parameters,namely,catalysts loading,cocatalysts,sacrificial agents,and irradiation sources.This review provides the necessary tools to select the election technique for adequately enhancing the photoactivity of LDH and modified LDH-based materials and concludes with a critical summary that outlines further research directions.

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.

Layered photocatalytic nanomaterials for environmental applications

The increasing pollution and human demand for a cleaner environment have made achieving the environmental sustainability a current research focus.As a “green” technology,semiconductor photocatalysis is of great significance to the environmental purification.Benefiting from the unique anisotropic crystal structure and electronic properties,layered photocatalytic nanomaterials show great potential for efficient photocatalytic environmental treatment.This review comprehensively summarizes the recent progress on layered photocatalytic nanomaterials for oxidation or reduction of pollutants in water and air along with the basic understanding of related mechanisms and developments in this field.First,the existing diversified layered photocatalysts are classified,and their different synthesis and modification strategies are discussed in detail to provide a comprehensive view of the material design that affects their photocatalytic performance.Subsequently,the extensive applications of the above-mentioned layered photocatalytic nanomaterials in environmental fields are systematically summarized,including photooxidation of water and air pollutants,and photoreduction of heavy metal pollutants,NO_(3)^(-),BrO_(3)^(-) and CO_(2).Finally,based on the current research achievements in layered photocatalysts for environmental remediation,the future development direction and challenges are proposed.

New Conditions for Intercalation of Organic Compounds into Semiconductor Nanomaterial

The intercalation of organic guests, 2-methyl pyridine （2-picoline） and 3-methyl pyridine （3-picoline） into semiconductor layered nanomaterial （MnPS3） was investigated. New conditions were applied. New phases appeared and lattice expansions were 0.36 nm for 2-picoline intercalation and 0.728 nm for 3-picoline inter- calation. The XRD （X- ray diffraction） patterns exhibit sharp hkl reflections confirming that the material is highly crystalline. The interlayer gap （0.64 nm） of the host plays a role for the arrangement of the guest in the interlayer region. The crystal structure of the MnPS3 was indexed in the monoclinic system before inter- calation. After intercalation, the crystal system was indexed in the trigonal unit cell. The lattice parameters were obtained and c-axis value was related to the （001） reflections.

Anisotropic phonon thermal transport in two-dimensional layered materials

Two-dimensional layered materials(2DLMs)have attracted growing attention in optoelectronic devices due to their intriguing anisotropic physical properties.Different members of 2DLMs exhibit unique anisotropic electrical,optical,and thermal properties,fundamentally related to their crystal structure.Among them,directional heat transfer plays a vital role in the thermal management of electronic devices.Here,we use density functional theory calculations to investigate the thermal transport properties of representative layered materials:β-InSe,γ-InSe,MoS2,and h-BN.We found that the lattice thermal conductivities ofβ-InSe,γ-InSe,MoS_(2),and h-BN display diverse anisotropic behaviors with anisotropy ratios of 10.4,9.4,64.9,and 107.7,respectively.The analysis of the phonon modes further indicates that the phonon group velocity is responsible for the anisotropy of thermal transport.Furthermore,the low lattice thermal conductivity of the layered InSe mainly comes from low phonon group velocity and atomic masses.Our findings provide a fundamental physical understanding of the anisotropic thermal transport in layered materials.We hope this study could inspire the advancement of 2DLMs thermal management applications in next-generation integrated electronic and optoelectronic devices.

Device simulation of quasi-two-dimensional perovskite/silicon tandem solar cells towards 30%-efficiency

Perovskite/silicon(Si) tandem solar cells have been recognized as the next-generation photovoltaic technology with efficiency over 30% and low cost. However, the intrinsic instability of traditional three-dimensional(3D) hybrid perovskite seriously hinders the lifetimes of tandem devices. In this work, the quasi-two-dimensional(2D)(BA)_(2)(MA)_(n-1)Pbn I_(3n+1)(n = 1, 2, 3, 4, 5)(where MA denotes methylammonium and BA represents butylammonium), with senior stability and wider bandgap, are first used as an absorber of semitransparent top perovskite solar cells(PSCs) to construct a fourterminal(4T) tandem devices with a bottom Si-heterojunction cell. The device model is established by Silvaco Atlas based on experimental parameters. Simulation results show that in the optimized tandem device, the top cell(n = 4) obtains a power conversion efficiency(PCE) of 17.39% and the Si bottom cell shows a PCE of 11.44%, thus an overall PCE of 28.83%. Furthermore, by introducing a 90-nm lithium fluoride(LiF) anti-reflection layer to reduce the surface reflection loss, the current density(J_(sc)) of the top cell is enhanced from 15.56 m A/cm^(2) to 17.09 m A/cm^(2), the corresponding PCE reaches 19.05%, and the tandem PCE increases to 30.58%. Simultaneously, in the cases of n = 3, 4, and 5, all the tandem PCEs exceed the limiting theoretical efficiency of Si cells. Therefore, the 4T quasi-2D perovskite/Si devices provide a more cost-effective tandem strategy and long-term stability solutions.

EFFECT OF SUSPENDED SOLID PARTICLES ON UNSTABILITY OF TWO-DIMENSION MIXING LAYER

By considering the effect of suspended solid particles in the ordinary equations for two-dimension inviscid incompressible mixing layer, the Rayleigh equation and the modified Rayleigh equation are obtained. And then, by solving the corresponding eigen-value equations with numerical computational method, the relation curves between perturbation frequency and spacial growth rate of the mixing layer for the varying particle loading, ratio of particle velocity to fluid velocity and Stokes number are got. Sever al important conclusions on the effect of suspended solid particles on unstability of the mixing layer are presented in the end by analyzing all the relation curves.

Electrically-Conductive Composite Nanomaterial with Multi-Walled Carbon Nanotubes

Specific conductivity of the composite nanomaterial layers with micron and submicron dimensions, consisting of carboxymethyl cellulose (CMC) and multiwalled carbon nanotubes (MWCNT) was investigated. Ultradispersed aqueous suspension was deposited on soft (aluminum foil, plates made from polyester and polyimide, cotton fabric, office paper) and solid (coverslip, silicon wafers with silicon oxide layer) substrates by silk-screen printing. Electrical resistance was measured by four-probe method and by the method of square on surface from which the conductivity and conductivity per square of surface were calculated taking into account layer’s geometric dimensions. Specific conductivity of the layers with thickness range 0.5 - 5 μm was? ~1.2×104÷4×104 S/m, and max conductivity per square was ~ 0.2 S. Investigated nanomaterial is attractive to electronic and biomedical applications.

Recent advances in two-dimensional nanomaterials for bone tissue engineering

Over the last decades,bone tissue engineering has increasingly become a research focus in the field of biomedical engineering,in which biomaterials play an important role because they can provide both biomechanical support and osteogenic microenvironment in the process of bone regeneration.Among these biomaterials,two-dimensional(2D)nanomaterials have recently attracted considerable interest owing to their fantastic physicochemical and biological properties including great biocompatibility,excellent osteogenic capability,large specific surface area,and outstanding drug loading capacity.In this review,we summarize the state-of-the-art advances in 2D nanomaterials for bone tissue engineering.Firstly,we introduce the most explored biomaterials used in bone tissue engineering and their advantages.We then highlight the advances of cutting-edge 2D nanomaterials such as graphene and its derivatives,layered double hydroxides,black phosphorus,transition metal dichalcogenides,montmorillonite,hexagonal boron nitride,graphite phase carbon nitride,and transition metal carbonitrides(MXenes)used in bone tissue engineering.Finally,the current challenges and future prospects of 2D nanomaterials for bone tissue regeneration in process of clinical translation are discussed.

Sub-nano Layers of Li, Be, and Al on the Si(100) Surface: Electronic Structure and Silicide Formation

Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(ML)thickness,were carried out.Calculations showed that band gaps of 1.02 eV,0.98 eV and 0.5 eV,respectively,appear in the densities of electronic states when the thickness of Li,Be and Al coverings is one ML.These gaps disappear with increasing thickness of the metal layers:first in the Li-Si system(for two ML),then in the Al-Si system(for three ML)and then in the Be-Si system(for four ML).This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100),Be-Si(100)and Al-Si(100)systems.

沸石咪唑骨架衍生空心纳米电极材料可控制备及其电化学性能研究

超级电容器是介于可充电电池和传统电容器之间的一种新型储能器件。它具有高功率密度、快速充放电和环境友好等优点。在众多应用于超级电容器的电极材料中,金属有机骨架材料因具有大的比表面积,可灵活调控的组成和结构,是十分理想的电极材料之一,又由于其易于合成、独特的结构和反应特性,也是制备纳米结构电极材料的理想模板之一。以沸石咪唑骨架(zeolitic lmidazolate framework,ZIF)-67为前驱体,采用二水合钼酸钠盐溶液刻蚀的方法成功制备了空心CoMo层状双金属氢氧化物(layered double hydroxides,LDH)纳米笼结构,同时还讨论了钼酸钠的用量对最终产物形貌和性能的影响。当用作超级电容器电极材料时,所制备的空心Co1Mo5 LDH在1 A/g的时候最多可提供578 F/g的比电容,当电流密度增加到10 A/g时,比电容保持在346 F/g。与活性炭组装成非对称超级电容器后,该储能器件在功率密度750 W/kg时,能量密度最大可达到21.25 W·h/kg。在5 A/g的电流密度下,经过15000次充放电循环后,仍保持了90%的初始容量。