Regular Layered Structure Research Articles

Highly Regular Layered Structure via Dual-Spatially-Confined Alignment of Nanosheets Enables High-Performance Nanocomposites.

Assembling ultrathin nanosheets into layered structure represents one promising way to fabricate high-performance nanocomposites. However, how to minimize the internal defects of the layered assemblies to fully exploit the intrinsic mechanical superiority of nanosheets remains challenging. Here, a dual-scale spatially confined strategy for the co-assembly of ultrathin nanosheets with different aspect ratios into a near-perfect layered structure is developed. Large-aspect-ratio (LAR) nanosheets are aligned due to the microscale confined space of a flat microfluidic channel, small-aspect-ratio (SAR) nanosheets are aligned due to the nanoscale confined space between adjacent LAR nanosheets. During this co-assembly process, SAR nanosheets can flatten LAR nanosheets, thus reducing wrinkles and pores of the assemblies. Benefiting from the precise alignment (orientation degree of 90.74%) of different-sized nanosheets, efficient stress transfer between nanosheets and interlayer matrix is achieved, resulting in layered nanocomposites with multiscale mechanical enhancement and superior fatigue durability (100000 bending cycles). The proposed co-assembly strategy can be used to orderly integrate high-quality nanosheets with different sizes or diverse functions toward high-performance or multifunctional nanocomposites.

Lignin‐Based Multilamellar Aggregates for Removing Ofloxacin Antibiotic: A Dissipative Particle Dynamics Simulation Study

AbstractLignin, a renewable aromatic polymer, has great potential as a synthetic building block for functional materials. The effects of quaternary ammonic methylation of alkali lignin (AL) on the morphologies and ofloxacin antibiotic (OA) removal application from water are investigated by using the dissipative particle dynamics (DPD) simulation method. Untreated AL can form spherical aggregates, but the phenylpropane units of untreated AL and loaded broad‐spectrum OA molecules are randomly distributed in aggregates. However, if quaternary ammonic groups are grafted onto all orthopositions of the phenolic hydroxyl groups (100‐QAMAL), then multilamellar spherical aggregates are obtained and OA molecules are entrapped in the aggregates. To prepare multilamellar spherical aggregates with an ordered and regular layered structure, <15 v% of 100‐QAMAL and low molecular weights of AL (≈4700–9400 Da) are suggested to be used. Lignin‐based multilamellar spherical aggregates can be adopted as potential functional carriers for removing pollutant OA from water.

Improved Tribological Performance of MOF@MXene/PI under High Temperature.

High-temperature-resistant and self-lubricating polymer composites with long life and high reliability are increasingly indispensable in the aerospace field. Herein, ZIF-67 grown on the MXene lamella was successfully prepared, and ZIF-67@MXene/PI composites with a regular layered structure were obtained by a hot-pressing three-dimensional network aerogel. It was revealed that incorporating ZIF-67@MXene into PI dramatically reduced the friction and abrasion with elevated temperatures. Largely, aerogel walls always paralleled the sliding direction by compressing, providing a significant antifriction effect. More notably, the presence of a vigorous tribofilm composed of a PI matrix and a diamond-type lattice MOF-modified MXene provided rolling and sliding interface friction under high temperatures, simultaneously. In addition, the uniform tribofilm with a thickness of about 200 nm can effectively avoid the direct contact of the friction pair during the sliding process. Hence, the combination of the constructed multiscale nanocomposites and nanostructured tribofilm with outstanding tribological performance endow the material potentially useful in reducing energy consumption, thus addressing the energy wastage problem caused by friction.

Order-disorder transition during shear thickening in bidisperse dense suspensions

Shear thickening of multimodal suspensions has proven difficult to understand because the rheology depends largely on the microscopic details of stress-induced frictional contacts at different particle size distributions (PSDs). Our discrete particle simulations below a critical volume fraction ϕc over a broad range of shear rates and PSDs elucidate the basic mechanism of order–disorder transition. Around the theoretical optimal PSD (relative content of small particles ζ1= 0.26), particles order into a layered structure in the Newtonian regime. At the onset of shear thickening, this layered structure transforms to a disordered one, accompanied by an abrupt viscosity jump. Minor increase in large-large particle contacts after the order–disorder transition causes apparent increase in radial force along the compressional axis. Bidisperse suspensions with less regular but stable layered structure at ζ1= 0.50 show good fluidity in the shear thickening regime. This work shows that in inertial flows where particle collisions dominate, order–disorder transition could play an essential role in shear thickening for bidisperse suspensions.

Ultrafast transformation of natural graphite into self-supporting graphene as superior anode materials for lithium-ion batteries

Graphite possesses remarkable potential as an anode material for lithium-ion batteries, thanks to its superb electrical conductivity and eco-friendliness. Nevertheless, challenging issues persist, such as its low maximum theoretical lithium storage capacity and constraints associated with the regular layered structure, which impede its practical application and advancement. In this regard, we proposed a novel approach to enhance the energy storage performance of lithium-ion batteries, involving the modification of natural graphite through irradiation with a high-current pulsed electron beam (HCPEB). Microscopic observations revealed that during the in-situ transformation of graphite particles into self-supporting graphene nanosheets, the high temperature generated by HCPEB irradiation led to the formation of structural defects, including Stone Wales and double vacancy defects. Consequently, the modified natural graphite electrode (particle size 12 μm) exhibited a reversible capacity of 420.4 mAh/g at 0.2C and maintained 94.5% of its reversible capacity after 500 cycles. In comparison to unmodified graphite (particle size 12 μm), the SEI film displayed enhanced stability, significantly improving cycling performance. These findings demonstrated that the defective graphene nanosheet structure enhances lithium storage activity sites, enlarges layer spacing, and enhances lithium storage performance. This study presents an efficient and environmentally friendly method for producing superior anode materials for lithium-ion batteries.

A system that delivers an antioxidant to mitochondria for the treatment of drug-induced liver injury

Mitochondria, a major source of reactive oxygen species (ROS), are intimately involved in the response to oxidative stress in the body. The production of excessive ROS affects the balance between oxidative responses and antioxidant defense mechanisms thus perturbing mitochondrial function eventually leading to tissue injury. Therefore, antioxidant therapies that target mitochondria can be used to treat such diseases and improve general health. This study reports on an attempt to establish a system for delivering an antioxidant molecule coenzyme Q10 (CoQ10) to mitochondria and the validation of its therapeutic efficacy in a model of acetaminophen (APAP) liver injury caused by oxidative stress in mitochondria. A CoQ10-MITO-Porter, a mitochondrial targeting lipid nanoparticle (LNP) containing encapsulated CoQ10, was prepared using a microfluidic device. It was essential to include polyethylene glycol (PEG) in the lipid composition of this LNP to ensure stability of the CoQ10, since it is relatively insoluble in water. Based on transmission electron microscope (TEM) observations and small angle X-ray scattering (SAXS) measurements, the CoQ10-MITO-Porter was estimated to be a 50 nm spherical particle without a regular layer structure. The use of the CoQ10-MITO-Porter improved liver function and reduced tissue injury, suggesting that it exerted a therapeutic effect on APAP liver injury.

Antimicrobial and mechanical properties of silver ion-exchanged transparent lithium-mica glass-ceramics

This study investigates silver ion-exchange of the transparent lithium-mica glass-ceramic in a molten mixture of AgNO3 and Ag2SO4 to realize the glass-ceramic antibacterial activity and improved mechanical properties. The ion-exchanged glass-ceramic was heated at 700 °C. Li+ ions in the interlayers of mica near surface of the glass-ceramic were exchanged for Ag+ ions in the molten salt. Ag+ ions intruded deeper inside from surface as the soaking time of the ion-exchange increased, disturbing the layer structure of the mica. Heating also diffused Ag+ ions deeper inside the glass-ceramic, reducing the concentration of Ag+ ions near the surface and realizing a uniform distribution of Ag+ ions to create a regular layer structure of mica. Both the ion-exchanger and the heated ion-exchanger showed antibacterial activity against Escherichia coli. However, their activities decreased in repeated antimicrobial tests. Because ion-exchange generated compressive stress near the surface, the Vickers hardness and fracture toughness increased, whereas heating lowered the heightened hardness. Although ion-exchange and subsequent heat treatment improved the machinability of the glass-ceramic, ion-exchange alone did not.

Enhanced remediation of cadmium-polluted soil and water using facilely prepared MnO2-coated rice husk biomass

Metal oxide-modified biochar can effectively remediate or adsorb heavy metals in polluted soil and wastewater. However, the interaction between cellulose and hemicellulose on the surface of biochar/biomass and metal oxides is unclear, and the loading stability, adsorption capacity and mechanism of metal oxides remain to be explored. In this work, weakly crystalline birnessite (δ-MnO2) rice husk biomass composites (MBC) were prepared via hydrothermal impregnation and then used to immobilize heavy metals in cadmium-polluted soil and wastewater. The surface of MBC was covered by sheet-like manganese oxides with a regular layered stacking structure. The adsorption of Cd(II) by MBC could be mainly attributed to monolayer chemisorption, which could achieve a maximum adsorption capacity of 115.04 mg g−1. The addition of 1.0 % MBC reduced the effective Cd concentration in CaCl2 extractant in the soil from 0.24 mg kg−1 to 0.09 mg kg−1, and the highest decreasing rate reached 62.5 %. Additionally, MBC could also reduce the concentration of H2O-leachable Cd from 22.44 μg kg−1 to 9.50 μg kg−1. MBC facilitated the transformation of exchangeable Cd (EX-Cd) to iron-manganese bound Cd (OX-Cd) mainly comprising crystalline Mn oxide and Fe oxide. In addition, the mechanisms for MBC immobilization of Cd in polluted-soil and aqueous systems may include complexation-dominated and ion exchange-assisted processes, which contribute to a better understanding of the chemical structures and characteristics of metal oxides used to directly modify biomass. Overall, the findings indicate the possibility of applying MBC for soil and water remediation.

Nickel-cobalt selenide nanosheets anchored on graphene for high performance all-solid-state asymmetric supercapacitors

• The NiCoSe/G-10 sample has a regular flower-like layered structure and is effectively combined with graphene oxide. • The NiCoSe/G-10 sample has high specific surface area, excellent specific capacitance, and good electrochemical stability. • Asymmetric supercapacitors have good electrochemical stability. Transition metal selenides in electrode material exploration for supercapacitors have drawn extensive interest because of their excellent conductivity and outstanding activity. Herein, nickel–cobalt selenide nanosheets anchored on graphene oxide (NiCoSe/G) were synthesized by water bath and selenization process. Graphene provides a continuous conductive network, on the one hand, the electrical conductivity of the material is effectively enhanced, and on the other hand, the volume and structure changes during the electrochemical reaction are well relieved. Benefiting from excellent electroconductivity and unique two-dimensional (2D) nanosheet structure, the optimized electrode (NiCoSe/G-10) exhibits a high specific capacity of 421.3 C/g (1 A/g) and an excellent cycling performance (after 5000 cycles) of 84.6 % capacity retention. Furthermore, the assembled NPC//NiCoSe/G-10 asymmetric supercapacitor achieves an excellent energy density of 40.4 Wh kg −1 at 533.3 W kg −1 and good capacity retention rate of 80.2 % after 5000 cycles. This paper provides a new strategy for the preparation of nickel–cobalt-based bimetallic selenides for supercapacitors with excellent characteristic.

A novel Ni–La-Nd-Y flim on Ni foam to enhance hydrogen evolution reaction in alkaline media

The exploration of non-precious metal catalysts has always been a hot topic. Here, a new type of Ni–La-Nd-Y film was electrodeposited on nickel foam (NF). The Ni–La-Nd-Y film shows outstanding HER activity and stability under alkaline conditions. La2NiO4 makes the electrode surface present a regular layered structure, which greatly increases the number of electrochemically active sites. Ni–La-Nd-Y only needs 46 mV overpotential driving current density of 10 mA cm−2 in 1MKOH solution, which is very close to the HER performance of metal Pt. By doping rare earth elements and taking advantage of the shrinkage characteristics of lanthanides, this work took advantage of the shrinkage characteristics of the lanthanide series and found new ideas for improving catalysts through the combination of different rare earth elements.

Graphitic carbon nitride-derived high lithium storage capacity graphite material with regular layer structure and the structural evolution mechanism

A novel graphite anode (Ni-g-C3N4) is synthesized by using graphitic carbon nitride as the precursor and nickel (Ni) as the catalyst, which dramatically decreases the reaction temperature to 850 °C. The critical role of Ni in denitrifying g-C3N4 to produce high-quality graphite is identified, with the results showing that the nitrogen content decreases from 62.1% to 1.2% and thus leading to greatly enhanced electrical conductivity as well as excellent rate capability, cycle performance and structure integrity. The Ni-g-C3N4 exhibits typical low voltage plateau characteristic of graphite anode and the transformation of graphite intercalation compounds are investigated in the in-situ XRD analysis during the discharge/charge process. The capacity retention is as high as 99.3% after 600 cycles at 0.5 A⋅g−1, demonstrating excellent structural stability. Moreover, the evolution from g-C3N4 to graphite Ni-g-C3N4 is investigated via TG-MS and high-temperature in-situ XRD, which clearly reveals that the catalytic graphitization processes mainly consist of the dissolution, re-precipitation and carbide conversion, along with the formation of intermediate Ni3C and the release of nitrogen gas. In general, this work not only proposes a novel method to synthesize high performance graphite anode from g-C3N4 for lithium ion batteries, but also unravels the catalytic graphitization mechanism.

Advanced cathode for dual-ion batteries: Waste-to-wealth reuse of spent graphite from lithium-ion batteries

The amount of spent lithium-ion batteries (LIBs) is constantly increasing as their popularity grows. It is important to develop a recycling method that cannot only convert large amounts of waste anode graphite into high value-added products but is also simple and environmentally friendly. In this work, spent graphite from an anode was transformed into a cathode for dual-ion batteries (DIBs) through a two-step treatment. This method enables the crystal structure and morphology of spent graphite to recover from the adverse effects of long cycling and be restored to a regular layered structure with appropriate layer spacing for anion intercalation. In addition, pyrolysis of the solid electrolyte interphase into an amorphous carbon layer prevents the electrode from degrading and improves its cycling performance. The recycled negative graphite has a high reversible capacity of 87 mAh g−1 at 200 ​mA ​g−1, and its rate performance when used as a cathode in DIBs is comparable to that of commercial graphite. This simple recycling idea turns spent anode graphite into a cathode material with attractive potential and superior electrochemical performance, genuinely achieving sustainable energy use. It also provides a new method for recovering exhausted batteries.

Effect of adding graphene oxide on the structure and properties of needle coke

Using medium and low temperature coal tar pitch as raw material, the refined raw material is obtained by solvent extraction with a mixed solvent of n-heptane and toluene, and then different amounts of graphene oxide(GO) are added to the refined raw material for thermal polymerization and calcination to obtain needle coke. The composition of the raw materials was analyzed by element analysis, infrared spectroscopy (FT-IR), NMR, XPS and other detection methods, and the scanning electron microscope (SEM), X-ray diffractometer (XRD), polarizing microscope, electrochemical analysis and other methods were used to analyze the structure and electrochemical properties of different needle coke. The experimental results show that the mixed solvent of n-heptane and toluene can refine the raw materials, which can effectively enrich aromatics, optimize the composition of the raw materials, and effectively remove the heteroatoms in the raw materials. In particular, the removal effect of O and S atoms is particularly significant, and the removal rates are 25.21 % and 82.50 %, respectively. Adding 0.01 wt% of GO to the refined raw materials can obtain needle coke products with a regular layered structure and relatively good electrochemical performance.

Создание расчетных сеток для задач обращения с РАО

The article describes an approach to mesh generation allowing to address radioactive waste management tasks. The approach is based on representing an object as a set of simple geometric shapes (primitives). The characteristics of the mesh (type, size, number of elements) are controlled at a primitive level. The program allows to combine primitives using boolean operations to describe complex objects (for example, intrusions in host rock and their intersections with excavations). To describe nested objects (for example, a radioactive waste container in a borehole or a borehole in a host rock), the program implements a hierarchy of primitives. This approach can be used to generate meshes of objects with regular geometry and/or layered structures. The program is written in Python language. The mesh is created by editing the input files in JSON format.

(UO2)(C10H8N2O2)2][HPW12O40]: The First Case of a Uranyl Coordination Network Containing a Keggin‐Type Polyoxometalate

A uranyl compound [(UO2)(C10H8N2O2)2][HPW12O40] has been hydrothermally synthesized (150 °C for 72 h) in the presence of typical Keggin‐phosphotungstic acid. This compound exhibits a regular layered structure which is composed of [UO2]2+ and bridging ligand 4,4'‐bipyridine‐N‐dioxide (4,4'‐BPDO). The nanosized cavities are occupied by Keggin‐anions [HPW12O40]2– through covalent bonds and hydrogen bonds, in order to hold the charge equilibrium and enhance the stability of the structure. The adsorption properties of this compound have been primarily investigated. The results indicate that the incorporation of Keggin‐anions plays an important role in the fast capture of cationic dye MB+. Compound 1 is the first case of uranyl coordination network decorated by POMs, which evidently provides a feasible strategy for controlling the structural connectivity and functionality of uranyl organic framework.

Zn–Al Layered Double Hydroxide Film Functionalized by a Luminescent Octahedral Molybdenum Cluster: Ultraviolet–Visible Photoconductivity Response

A novel UV-Vis photodetector consisting of an octahedral molybdenum cluster-functionalized Zn2Al layered double hydroxide (LDH) has been successfully synthesized by co-precipitation and delamination methods under ambient conditions. The electrophoretic deposition process has been used as a low-cost, fast, and effective method to fabricate thin and transparent nanocomposite films containing a dense and regular layered structure. The study provided evidence that the presence of the Mo6 cluster units between the LDH does not affect the ionic conduction mechanism of the LDH, which linearly depends on the relative humidity and temperature. Moreover, the photocurrent response is remarkably extended to the visible domain. The reproducibility and stabilization of the photocurrent response caused by the Mo6 cluster-functionalized LDH have been verified upon light excitation at 540 nm. Additionally, it was demonstrated that the films show advantageously strong adherence properties for application requirements.

Formation of Regular Layered Structures upon Solid-State Phase Transitions with Varying the Concentration

The auto-oscillation dynamics of the interface and the parameters of a periodic layered impurity microstructure that forms as a result of a solid-state phase transition with varying the concentration that takes place when applying a mobile temperature gradient is calculated in terms of a one-dimensional capillary–wave model.

In-Situ Energy Dispersive X-ray Reflectivity Applied to Polyoxometalate Films: An Approach to Morphology and Interface Stability Issues in Organic Photovoltaics

Organic solar cells, characterized by a symmetrical regular layered structure, are very promising systems for developing green, low cost, and flexible solar energy conversion devices. Despite the efficiencies being appealing (over 17%), the technological transfer is still limited by the low durability. Several processes, in bulk and at interface, are responsible. The quick downgrading of the performance is due to a combination of physical and chemical degradations. These phenomena induce instability and a drop of performance in working conditions. Close monitoring of these processes is mandatory to understand the degradation pathways upon device operation. Here, an unconventional approach based on Energy Dispersive X-ray Reflectivity (ED-XRR) performed in-situ is used to address the role of Wells–Dawson polyoxometalate (K6-P2W18O62, hereafter K6-P2W18) as hole transporting layer in organic photovoltaics. The results demonstrate that K6-P2W18 thin films, showing ideal bulk and interface properties and superior optical/morphological stability upon prolonged illumination, are attractive candidates for the interface of durable OPV devices.

An Easy and Ecological Method of Obtaining Hydrated and Non-Crystalline WO3-x for Application in Supercapacitors.

In this work, we report the synthesis of hydrated and non-crystalline WO3 flakes (WO3−x) via an environmentally friendly and facile water-based strategy. This method is described, in the literature, as exfoliation, however, based on the results obtained, we cannot say unequivocally that we have obtained an exfoliated material. Nevertheless, the proposed modification procedure clearly affects the morphology of WO3 and leads to loss of crystallinity of the material. TEM techniques confirmed that the process leads to the formation of WO3 flakes of a few nanometers in thickness. X-ray diffractograms affirmed the poor crystallinity of the flakes, while spectroscopic methods showed that the materials after exfoliation were abundant with the surface groups. The thin film of hydrated and non-crystalline WO3 exhibits a seven times higher specific capacitance (Cs) in an aqueous electrolyte than bulk WO3 and shows an outstanding long-term cycling stability with a capacitance retention of 92% after 1000 chronopotentiometric cycles in the three-electrode system. In the two-electrode system, hydrated WO3−x shows a Cs of 122 F g−1 at a current density of 0.5 A g−1. The developed supercapacitor shows an energy density of 60 Whkg−1 and power density of 803 Wkg−1 with a decrease of 16% in Csp after 10,000 cycles. On the other hand, WO3−x is characterized by inferior properties as an anode material in lithium-ion batteries compared to bulk WO3. Lithium ions intercalate into a WO3 crystal framework and occupy trigonal cavity sites during the electrochemical polarization. If there is no regular layer structure, as in the case of the hydrated and non-crystalline WO3, the insertion of lithium ions between WO3 layers is not possible. Thus, in the case of a non-aqueous electrolyte, the specific capacity of the hydrated and non-crystalline WO3 electrode material is much lower in comparison with the specific capacity of the bulk WO3-based anode material.

Topochemical synthesis of two-dimensional molybdenum carbide (Mo2C) via Na2CO3-Assited carbothermal reduction of 2H–MoS2

Due to its promising applications on catalysis, electronics and electrochemical energy storage, 2D Mo2C has emerged as an important member in the 2D family. Herein, an efficient and high-yield method was proposed for the preparation of ultra-thin 2D Mo2C via Na2CO3-assited carbothermal reduction of 2H–MoS2. It was found that 2H–MoS2 can be completely carbonized to Mo2C at a MoS2:Na2CO3:C molar ratio of 2:4.2:11 at 850 °C for 2 h. Meanwhile, the prepared Mo2C were intercalated by the co-product Na2S. After leaching treatment with deionized water, the intercalated Na2S was removed and high crystalline 2D Mo2C were successfully prepared. Furthermore, the addition of Na2CO3 as a desulfurizer can greatly promote the carburization and exfoliation rates of 2H–MoS2. As can be seen from the FE-SEM images, the prepared Mo2C has a pretty regular layered structure with the layer thickness of 5–15 nm.