Photoluminescence of Two-Dimensional MoS Nanosheets Produced by Liquid Exfoliation.

Extraordinary properties of two-dimensional materials make them attractive for applications in different fields. One of the prospective niches is optical applications, where such types of materials demonstrate extremely sensitive performance and can be used for labeling. However, the optical properties of liquid-exfoliated 2D materials need to be analyzed.

Optoelectronic and Optomechanical Properties of Few-Atomic-Layer Black Phosphorus Nanoflakes as Revealed by In Situ TEM.

The optoelectronic signatures of free-standing few-atomic-layer black phosphorus nanoflakes are analyzed by in situ transmission electron microscopy (TEM). As compared to other 2D materials, the band gap of black phosphorus (BP) is related directly to multiple thicknesses and can be tuned by nanoflake thickness and strain. The photocurrent measurements with the TEM show a stable response to infrared light illumination and change of nanoflakes band gap with deformation while pressing them between two electrodes assembled in the microscope.

Thermal and Electrical Properties of Additively Manufactured Polymer-Boron Nitride Composite.

The efficiency of electronic microchip-based devices increases with advancements in technology, while their size decreases. This miniaturization leads to significant overheating of various electronic components, such as power transistors, processors, and power diodes, leading to a reduction in their lifespan and reliability. To address this issue, researchers are exploring the use of materials that offer efficient heat dissipation.

Moiré Diamones: New Diamond-like Films of Semifunctionalized Twisted Graphene Layers.

We proposed novel carbon nanostructures based on a twisted few-layered graphene with one side passivated by hydrogen or fluorine: Moiré diamones on graphene. The presence of a dangling bond at the bottom layer of diamones leads to the appearance of spin density localization, which can be tuned by the variation of the twist angle with the following formation of Moiré diamones. The spin-polarized nature of electronic density distribution was obtained and discussed in detail on the basis of ab initio calculations.

Computational Design of Gas Sensors Based on VS Monolayer.

Novel magnetic gas sensors are characterized by extremely high efficiency and low energy consumption, therefore, a search for a two-dimensional material suitable for room temperature magnetic gas sensors is a critical task for modern materials scientists. Here, we computationally discovered a novel ultrathin two-dimensional antiferromagnet VS, which, in addition to stability and remarkable electronic properties, demonstrates a great potential to be applied in magnetic gas sensing devices. Quantum-mechanical calculations within the DFT + approach show the antiferromagnetic ground state of VS, which exhibits semiconducting electronic properties with a band gap of 0.

Semiconductor nanochannels in metallic carbon nanotubes by thermomechanical chirality alteration.

Carbon nanotubes have a helical structure wherein the chirality determines whether they are metallic or semiconducting. Using in situ transmission electron microscopy, we applied heating and mechanical strain to alter the local chirality and thereby control the electronic properties of individual single-wall carbon nanotubes. A transition trend toward a larger chiral angle region was observed and explained in terms of orientation-dependent dislocation formation energy.

Tunable Single-Atomic Charges on a Cleaved Intercalated Transition Metal Dichalcogenide.

Control of a single ionic charge state by altering the number of bound electrons has been considered as an ultimate testbed for atomic charge-induced interactions and manipulations, and such subject has been studied in artificially deposited objects on thin insulating layers. We demonstrate that an entire layer of controllable atomic charges on a periodic lattice can be obtained by cleaving metallic CoNbS, an intercalated transition metal dichalcogenide. We identified a metastable charge state of Co with a different valence and manipulated atomic charges to form a linear chain of the metastable charge state.

Novel two-dimensional boron oxynitride predicted using the USPEX evolutionary algorithm.

Oxidation is a unique process that significantly changes the structure and properties of a material. Doping of h-BN by oxygen is a hot topic in material science leading to the possibility of synthesis of novel 2D structures with customized electronic properties. It is still unclear how the atomic structure changes in the presence of external atoms during the oxidation of h-BN.

Mechanical Engineering Effect in Electronic and Optical Properties of Graphene Nanomeshes.

Here, we present an ab initio study of ways for engineering electronic and optical properties of bilayered graphene nanomeshes with various stacking types via mechanical deformations. Strong evolution of the electronic structure and absorption spectra during deformation is studied and analyzed. The obtained results are of significant importance and open up new prospects for using such nanomeshes as materials with easily controlled properties in electronic and optoelectronic nanodevices.

Induced spin polarization in graphene interactions with halogen doped MoS and MoSe monolayers by DFT calculations.

Magnetic halogen doped MoX2 (X = S and Se) monolayers influenced the electronic structure of graphene through a proximity effect. This process was observed using state-of-the-art calculations. It was found that the substitution of a single chalcogen atom with a halogen atom (F, Cl, Br, and I) results in n-type doping of MoX2.

Young's Modulus and Tensile Strength of TiC MXene Nanosheets As Revealed by TEM Probing, AFM Nanomechanical Mapping, and Theoretical Calculations.

Two-dimensional transition metal carbides, that is, MXenes and especially TiC, attract attention due to their excellent combination of properties. TiC nanosheets could be the material of choice for future flexible electronics, energy storage, and electromechanical nanodevices. There has been limited information available on the mechanical properties of TiC, which is essential for their utilization.

Exotic Two-Dimensional Structure: The First Case of Hexagonal NaCl.

NaCl is one of the simplest compounds and was thought to be well-understood, and yet, unexpected complexities related to it were uncovered at high pressure and in low-dimensional states. Here, exotic hexagonal NaCl thin films on the (110) diamond surface were crystallized in the experiment following a theoretical prediction based on evolutionary algorithm USPEX. State-of-the-art calculations and experiments showed the existence of a hexagonal NaCl thin film, which is due to the strong chemical interaction of the NaCl film with the diamond substrate.

Fluorinated graphene nanoparticles with 1-3 nm electrically active graphene quantum dots.

A new approach to creating a new and locally nanostructured graphene-based material is reported. We studied the electric and structural properties of partially fluorinated graphene (FG) films obtained from an FG-suspension and nanostructured by high-energy Xe ions. Local shock heating in ion tracks is suggested to be the main force driving the changes.

Novel Unexpected Reconstructions of (100) and (111) Surfaces of NaCl: Theoretical Prediction.

We have predicted stable reconstructions of the (100) and (111) surfaces of NaCl using the global optimization algorithm USPEX. Several new reconstructions, together with the previously reported ones, are found. For the cleaved bare (100) surface, pure Na and pure Cl are the only stable surface phases.

Crystallography-Derived Young's Modulus and Tensile Strength of AlN Nanowires as Revealed by in Situ Transmission Electron Microscopy.

Aluminum nitride (AlN) has a unique combination of properties, such as high chemical and thermal stability, nontoxicity, high melting point, large energy band gap, high thermal conductivity, and intensive light emission. This combination makes AlN nanowires (NWs) a prospective material for optoelectronic and field-emission nanodevices. However, there has been very limited information on mechanical properties of AlN NWs that is essential for their reliable utilization in modern technologies.

Mechanical, Electrical, and Crystallographic Property Dynamics of Bent and Strained Ge/Si Core-Shell Nanowires As Revealed by in situ Transmission Electron Microscopy.

Research on electromechanical properties of semiconducting nanowires, including plastic behavior of Si nanowires and superb carrier mobility of Ge and Ge/Si core-shell nanowires, has attracted increasing attention. However, to date, there have been no direct experimental studies on crystallography dynamics and its relation to electrical and mechanical properties of Ge/Si core-shell nanowires. In this Letter, we in parallel investigated the crystallography changes and electrical and mechanical behaviors of Ge/Si core-shell nanowires under their deformation in a transmission electron microscope (TEM).

Chirality transitions and transport properties of individual few-walled carbon nanotubes as revealed by in situ TEM probing.

Physical properties of carbon nanotubes (CNTs) are closely related to the atomic structure, i.e. the chirality.

Compressive properties of hollow BN nanoparticles: theoretical modeling and testing using a high-resolution transmission electron microscope.

Due to their excellent mechanical properties, nanoparticles have great potential as reinforcing phases in composite materials, friction modifiers in liquid lubricants, catalysts and drug-delivery agents. In the present study, the mechanical analysis of individual spherical hollow BN nanoparticles (BNNPs) using a combination of in situ compression tests inside a high-resolution transmission electron microscope (TEM) and theoretical modelling was conducted. It was found that BNNPs display high mechanical stiffness and a large value of elastic recovery.

Tuning of the Optical, Electronic, and Magnetic Properties of Boron Nitride Nanosheets with Oxygen Doping and Functionalization.

Engineering of the optical, electronic, and magnetic properties of hexagonal boron nitride (h-BN) nanomaterials via oxygen doping and functionalization has been envisaged in theory. However, it is still unclear as to what extent these properties can be altered using such methodology because of the lack of significant experimental progress and systematic theoretical investigations. Therefore, here, comprehensive theoretical predictions verified by solid experimental confirmations are provided, which unambiguously answer this long-standing question.

One-atom-thick 2D copper oxide clusters on graphene.

The successful isolation and remarkable properties of graphene have recently triggered investigation of two-dimensional (2D) materials from layered compounds; however, one-atom-thick 2D materials without bulk layered counterparts are scarcely reported. Here we report the structure and properties of novel 2D copper oxide studied by experimental and theoretical methods. Electron microscopy observations reveal that copper oxide can form monoatomic layers with an unusual square lattice on graphene.

Novel hybrid C/BN two-dimensional heterostructures.

Here we present an investigation of new quasi-two-dimensional heterostructures based on the alternation of bounded carbon and boron nitride layers (C/BN). We carried out a theoretical study of the atomic structure, stability and electronic properties of the proposed heterostructures. Such ultrathin quasi-two-dimensional C/BN films can be synthesized by means of chemically induced phase transition by connection of the layers of multilayered h-BN/graphene van der Waals heterostructures, which is indicated by the negative phase transition pressure in the calculated phase diagrams (P, T) of the films.

Statistically Analyzed Photoresponse of Elastically Bent CdS Nanowires Probed by Light-Compatible In Situ High-Resolution TEM.

We demonstrate that high resolution transmission electron microscopy (HRTEM) paired with light illumination of a sample and its electrical probing can be utilized for the in situ study of initiated photocurrents in free-standing nanowires. Morphology, phase and crystallographic information from numerous individual CdS nanowires is obtained simultaneously with photocurrent measurements. Our results indicate that elastically bent CdS nanowires possessing a wurtzite structure show statistically unchanged values of ON/OFF (photocurrent/dark current) ratios.

Nanostructured BN-Mg composites: features of interface bonding and mechanical properties.

Magnesium (Mg) is one of the lightest industrially used metals. However, wide applications of Mg-based components require a substantial enhancement of their mechanical characteristics. This can be achieved by introducing small particles or fibers into the metal matrix.

Hydrogen adsorption study. Formation of quantum dots on graphene nanoribbons within tight-binding approach.

Based on the tight-binding model, we investigate the formation process of quantum dots onto graphene nanoribbons (GNRs) by the sequential adsorption of hydrogen atoms onto the ribbon's surface. We define the difference between hydrogenation processes onto the surface of zigzag (ZGNR) and armchair graphene nanoribbons (AGNR) by calculating the binding energies with respect to the energy of isolated hydrogen atoms for all considered structures.

Nanomechanical cleavage of molybdenum disulphide atomic layers.

The discovery of two-dimensional materials became possible due to the mechanical cleavage technique. Despite its simplicity, the as-cleaved materials demonstrated surprising macro-continuity, high crystalline quality and extraordinary mechanical and electrical properties that triggered global research interest. Here such cleavage processes and associated mechanical behaviours are investigated by a direct in situ transmission electron microscopy probing technique, using atomically thin molybdenum disulphide layers as a model material.