Strain and Spin-Orbit Coupling Engineering in Twisted WS/Graphene Heterobilayer.

The strain in hybrid van der Waals heterostructures, made of two distinct two-dimensional van der Waals materials, offers an interesting handle on their corresponding electronic band structure. Such strain can be engineered by changing the relative crystallographic orientation between the constitutive monolayers, notably, the angular misorientation, also known as the "twist angle". By combining angle-resolved photoemission spectroscopy with density functional theory calculations, we investigate here the band structure of the WS/graphene heterobilayer for various twist angles.

A simple and accurate HFCF-UF method for the analysis of homocysteine, cysteine, cysteinyl-glycine, and glutathione in human blood.

The presence of reduced aminothiols, including homocysteine (Hcy), cysteine (Cys), cysteinyl-glycine (CG), and glutathione (GSH), is significantly increased in the pathological state. However, there have been no reports on the relationship between reduced aminothiols (Hcy, Cys, CG, and GSH) and different genders, ages, and drug combinations in human blood. The accurate quantification of these reduced thiols in biological fluids is important for monitoring some special pathological conditions of humans.

Rapid Growth of Monolayer MoSe Films for Large-Area Electronics.

The large-scale growth of semiconducting thin films on insulating substrates enables batch fabrication of atomically thin electronic and optoelectronic devices and circuits without film transfer. Here an efficient method to achieve rapid growth of large-area monolayer MoSe films based on spin coating of Mo precursor and assisted by NaCl is reported. Uniform monolayer MoSe films up to a few inches in size are obtained within a short growth time of 5 min.

Relationship Between the Free and Total Methotrexate Plasma Concentration in Children and Application to Predict the Toxicity of HD-MTX.

High-dose methotrexate (HD-MTX) can be highly effective as well as extremely toxic. Many drug molecules can bind to plasma proteins to different extents , whereas only the free drug can reach the site of action to exert a pharmacological effect and cause toxicity. However, free MTX concentrations in plasma have not been reported.

Nanoscale Friction Behavior of Transition-Metal Dichalcogenides: Role of the Chalcogenide.

Despite extensive research on the tribological properties of MoS, the frictional characteristics of other members of the transition-metal dichalcogenide (TMD) family have remained relatively unexplored. To understand the effect of the chalcogen on the tribological behavior of these materials and gain broader general insights into the factors controlling friction at the nanoscale, we compared the friction force behavior for a nanoscale single asperity sliding on MoS, MoSe, and MoTe in both bulk and monolayer forms through a combination of atomic force microscopy experiments and molecular dynamics simulations. Experiments and simulations showed that, under otherwise identical conditions, MoS has the highest friction among these materials and MoTe has the lowest.

Phase Transition in a Memristive Suspended MoS Monolayer Probed by Opto- and Electro-Mechanics.

Semiconducting monolayers of a 2D material are able to concatenate multiple interesting properties into a single component. Here, by combining opto-mechanical and electronic measurements, we demonstrate the presence of a partial 2H-1T' phase transition in a suspended 2D monolayer membrane of MoS. Electronic transport shows unexpected memristive properties in the MoS membrane, in the absence of any external dopants.

A Direct Injection Technique to Improve Biosafety to Analyze Levetiracetam Concentrations in Human Serum and Its Application in Therapeutic Drug Monitoring.

Background: With the outbreak of COVID-19, it has become very important to improve biosafety measures taken by medical staff. Fewer pretreatment steps correspond to lower chances of infection. The authors established a direct injection technique to analyze levetiracetam (LEV) concentrations in human serum and studied its application in therapeutic drug monitoring.

MoS-enabled dual-mode optoelectronic biosensor using a water soluble variant of -opioid receptor for opioid peptide detection.

Owing to their unique electrical and optical properties, two-dimensional transition metal dichalcogenides have been extensively studied for their potential applications in biosensing. However, simultaneous utilization of both optical and electrical properties has been overlooked, yet it can offer enhanced accuracy and detection versitility. Here, we demonstrate a dual-mode optoelectronic biosensor based on monolayer molybdenum disulfide (MoS) capable of producing simultaneous electrical and optical readouts of biomolecular signals.

Atomic-scale patterning in two-dimensional van der Waals superlattices.

Two-dimensional (2D) van der Waals superlattices comprised of two stacked monolayer materials have attracted significant interest as platforms for novel optoelectronic and structural behavior. Although studies are focused on superlattice fabrication, less effort has been given to the nanoscale patterning and structural modification of these systems. In this report, we demonstrate the localized layer-by-layer thinning and formation of nanopores/defects in 2D superlattices, such as stacked MoS-WS van der Waals heterostructures and chemical vapor deposited bilayer WSe, using aberration-corrected scanning transmission electron microscopy (STEM).

Controlled Growth of Large-Area Bilayer Tungsten Diselenides with Lateral P-N Junctions.

Bilayer two-dimensional (2D) van der Waals (vdW) materials are attracting increasing attention due to their predicted high quality electronic and optical properties. Here, we demonstrate dense, selective growth of WSe bilayer flakes by chemical vapor deposition with the use of a 1:10 molar mixture of sodium cholate and sodium chloride as the growth promoter to control the local diffusion of W-containing species. A large fraction of the bilayer WSe flakes showed a 0 (AB) and 60° (AA') twist between the two layers, whereas Moiré 15 and 30° twist angles were also observed.

Origin of Nanoscale Friction Contrast between Supported Graphene, MoS, and a Graphene/MoS Heterostructure.

Ultralow friction can be achieved with 2D materials, particularly graphene and MoS. The nanotribological properties of these different 2D materials have been measured in previous atomic force microscope (AFM) experiments sequentially, precluding immediate and direct comparison of their frictional behavior. Here, friction is characterized at the nanoscale using AFM experiments with the same tip sliding over graphene, MoS, and a graphene/MoS heterostructure in a single measurement, repeated hundreds of times, and also measured with a slowly varying normal force.

Highly active single-layer MoS catalysts synthesized by swift heavy ion irradiation.

Two-dimensional molybdenum-disulfide (MoS2) catalysts can achieve high catalytic activity for the hydrogen evolution reaction upon appropriate modification of their surface. The intrinsic inertness of the compound's basal planes can be overcome by either increasing the number of catalytically active edge sites or by enhancing the activity of the basal planes via a controlled creation of sulfur vacancies. Here, we report a novel method of activating the MoS2 surface using swift heavy ion irradiation.

Effect of Synthesis on Performance of MXene/Iron Oxide Anode Material for Lithium-Ion Batteries.

Two-dimensional heterostructures, such as FeO/MXene nanoparticles, can be attractive anode materials for lithium-ion batteries (LIBs) due to the synergy between high lithium-storage capacity of FeO and stable cyclability and high conductivity provided by MXene. Here, we improved the storage performance of TiCT (MXene)/FeO nanocomposite by confining FeO nanoparticles into TiCT nanosheets with different mixing ratios using a facile and scalable dry ball-milling process. Composites of TiCT -25 wt % FeO and TiCT -50 wt % FeO synthesized by ball-milling resulted in uniform distribution of FeO nanoparticles on TiCT nanosheets with minimum oxidation of MXene as compared to composites prepared by hydrothermal or wet sonication.

Size-Dependent Physical and Electrochemical Properties of Two-Dimensional MXene Flakes.

Two-dimensional (2D) particles, including transition metal carbides (MXenes), often exhibit large lateral-size polydispersity in delaminated colloidal solutions. This heterogeneity results in challenges when conducting fundamental studies, such as investigating correlations between properties and the 2D flake size. To resolve this challenge, we have developed solution-processable techniques to control and sort 2D titanium carbide (TiCT ) MXene flakes after synthesis based on sonication and density gradient centrifugation, respectively.

Thickness-independent capacitance of vertically aligned liquid-crystalline MXenes.

The scalable and sustainable manufacture of thick electrode films with high energy and power densities is critical for the large-scale storage of electrochemical energy for application in transportation and stationary electric grids. Two-dimensional nanomaterials have become the predominant choice of electrode material in the pursuit of high energy and power densities owing to their large surface-area-to-volume ratios and lack of solid-state diffusion. However, traditional electrode fabrication methods often lead to restacking of two-dimensional nanomaterials, which limits ion transport in thick films and results in systems in which the electrochemical performance is highly dependent on the thickness of the film.

Crystalline Bilayer Graphene with Preferential Stacking from Ni-Cu Gradient Alloy.

We developed a high-yield synthesis of highly crystalline bilayer graphene (BLG) with two preferential stacking modes using a Ni-Cu gradient alloy growth substrate. Previously reported approaches for BLG growth include flat growth substrates of Cu or Ni-Cu uniform alloys and "copper pocket" structures. Use of flat substrates has the advantage of being scalable, but the growth mechanism is either "surface limited" (for Cu) or carbon precipitation (for uniform Ni-Cu), which results in multicrystalline BLG grains.

Recoil Effect and Photoemission Splitting of Trions in Monolayer MoS.

The 2D geometry nature and low dielectric constant in transition-metal dichalcogenides lead to easily formed strongly bound excitons and trions. Here, we studied the photoluminescence of van der Waals heterostructures of monolayer MoS and graphene at room temperature and observed two photoluminescence peaks that are associated with trion emission. Further study of different heterostructure configurations confirms that these two peaks are intrinsic to MoS and originate from a bound state and Fermi level, respectively, of which both accept recoiled electrons from trion recombination.

Nanodiamonds suppress the growth of lithium dendrites.

Lithium metal has been regarded as the future anode material for high-energy-density rechargeable batteries due to its favorable combination of negative electrochemical potential and high theoretical capacity. However, uncontrolled lithium deposition during lithium plating/stripping results in low Coulombic efficiency and severe safety hazards. Herein, we report that nanodiamonds work as an electrolyte additive to co-deposit with lithium ions and produce dendrite-free lithium deposits.

Synthesis and Physical Properties of Phase-Engineered Transition Metal Dichalcogenide Monolayer Heterostructures.

Heterostructures of transition metal dichalcogenides (TMDs) offer the attractive prospect of combining distinct physical properties derived from different TMD structures. Here, we report direct chemical vapor deposition of in-plane monolayer heterostructures based on 1H-MoS and 1T'-MoTe. The large lattice mismatch between these materials led to intriguing phenomena at their interface.

Hollow MXene Spheres and 3D Macroporous MXene Frameworks for Na-Ion Storage.

2D transition metal carbides and nitrides, named MXenes, are attracting increasing attentions and showing competitive performance in energy storage devices including electrochemical capacitors, lithium- and sodium-ion batteries, and lithium-sulfur batteries. However, similar to other 2D materials, MXene nanosheets are inclined to stack together, limiting the device performance. In order to fully utilize MXenes' electrochemical energy storage capability, here, processing of 2D MXene flakes into hollow spheres and 3D architectures via a template method is reported.

Two-Dimensional Titanium Carbide MXene As a Cathode Material for Hybrid Magnesium/Lithium-Ion Batteries.

As an alternative to pure lithium-ion, Li, systems, a hybrid magnesium, Mg, and Li battery can potentially combine the high capacity, high voltage, and fast Li intercalation of Li-ion battery cathodes and the high capacity, low cost, and dendrite-free Mg metal anodes. Herein, we report on the use of two-dimensional titanium carbide, TiCT (MXene), as a cathode in hybrid Mg/Li batteries, coupled with a Mg metal anode. Free-standing and flexible TiCT/carbon nanotube composite "paper" delivered ∼100 mAh g at 0.

Pseudocapacitive Electrodes Produced by Oxidant-Free Polymerization of Pyrrole between the Layers of 2D Titanium Carbide (MXene).

Heterocyclic pyrrole molecules are in situ aligned and polymerized in the -absence of an oxidant between layers of the 2D Ti3C2Tx (MXene), resulting in high volumetric and gravimetric capacitances with capacitance retention of 92% after 25,000 cycles at a 100 mV s(-1) scan rate.

Amine-Assisted Delamination of Nb2C MXene for Li-Ion Energy Storage Devices.

2D Nb2CTx MXene flakes are produced using an amine-assisted delamination process. Upon mixing with carbon nanotubes and filtration, freestanding, flexible paper is produced. The latter exhibits high capacity and excellent stability when used as the electrode for Li-ion batteries and capacitors.

Synthesis of carbon/sulfur nanolaminates by electrochemical extraction of titanium from Ti₂SC.

Herein we electrochemically and selectively extract Ti from the MAX phase Ti2SC to form carbon/sulfur (C/S) nanolaminates at room temperature. The products are composed of multi-layers of C/S flakes, with predominantly amorphous and some graphene-like structures. Covalent bonding between C and S is observed in the nanolaminates, which render the latter promising candidates as electrode materials for Li-S batteries.

Conductive two-dimensional titanium carbide 'clay' with high volumetric capacitance.

Safe and powerful energy storage devices are becoming increasingly important. Charging times of seconds to minutes, with power densities exceeding those of batteries, can in principle be provided by electrochemical capacitors--in particular, pseudocapacitors. Recent research has focused mainly on improving the gravimetric performance of the electrodes of such systems, but for portable electronics and vehicles volume is at a premium.