Hexagonal boron nitride (h-BN), a layered material similar to graphite, is a promising dielectric. Monolayer h-BN, so-called "white graphene", has been isolated from bulk BN and could be useful as a complementary two-dimensional dielectric substrate for graphene electronics. Here we report the large area synthesis of h-BN films consisting of two to five atomic layers, using chemical vapor deposition. These atomic films show a large optical energy band gap of 5.5 eV and are highly transparent over a broad wavelength range. The mechanical properties of the h-BN films, measured by nanoindentation, show 2D elastic modulus in the range of 200-500 N/m, which is corroborated by corresponding theoretical calculations.

The chemical inertness of the defect-free basal plane confers environmental stability to MoS single layers, but it also limits their chemical versatility and catalytic activity. The stability of pristine MoS basal plane against oxidation under ambient conditions is a widely accepted assumption however, here we report single-atom-level structural investigations that reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS single layers during ambient exposure. The use of scanning tunnelling microscopy reveals a slow oxygen-substitution reaction, during which individual sulfur atoms are replaced one by one by oxygen, giving rise to solid-solution-type 2D MoSO crystals. Oxygen substitution sites present all over the basal plane act as single-atom reaction centres, substantially increasing the catalytic activity of the entire MoS basal plane for the electrochemical H evolution reaction.

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. Narrowing of the optical bandgap in h-BN nanosheets (from ≈5.5 eV down to 2.1 eV) and the appearance of paramagnetism and photoluminescence (of both Stokes and anti-Stokes types) in them after oxygen doping and functionalization are discussed. These results are highly valuable for further advances in semiconducting nanoscale electronics, optoelectronics, and spintronics.

We consider a new C 2 H nanostructure based on bilayer graphene transformed under the covalent bond of hydrogen atoms adsorbed on its external surface, as well as compounds of carbon atoms located opposite each other in neighboring layers. They constitute a "film" of the 111 diamond with a thickness of less than 1 nm, which is called diamane. The energy characteristics and electron spectra of diamane, graphene, and diamond are calculated using the density functional theory and are compared with each other. The effective Young's moduli and destruction thresholds of diamane and graphene membranes are determined by the molecular dynamics method. It is shown that C 2 H diamane is more stable than CH graphane, its dielectric "gap" is narrower than the band gap of bulk diamond (by 0.8 eV) and graphane (by 0.3 eV), and is harder and more brittle than the latter.

We explore how a few-layer graphene can undergo phase transformation into thin diamond film under reduced or no pressure, if the process is facilitated by hydrogenation of the surfaces. Such a "chemically induced phase transition" is inherently nanoscale phenomenon, when the surface conditions directly affect thermodynamics, and the transition pressure depends greatly on film thickness. For the first time we obtain, by ab initio computations of the Gibbs free energy, a phase diagram (P, T, h) of quasi-two-dimensional carbon-diamond film versus multilayered graphene. It describes accurately the role of film thickness h and shows the feasibility of creating novel quasi-two-dimensional materials. Further, the role of finite diameter of graphene flakes and possible formation of the diamond films with the (110) surface are described as well.

Construction of cellular architectures has been expected to enhance materials' mechanical tolerance and to stimulate and broaden their efficient utilizations in many potential fields. However, hitherto, there have been rather scarce developments in boron nitride (BN)-type cellular architectures because of well-known difficulties in the syntheses of BN-based structures. Herein, cellular-network multifunctional foams made of interconnective nanotubular hexagonal BN (h-BN) architectures are developed using carbothermal reduction-assisted in situ chemical vapor deposition conversion from N-doped tubular graphitic cellular foams. These ultralight, chemically inert, thermally stable, and robust-integrity (supporting about 25,000 times of their own weight) three-dimensional-BN foams exhibit a 98.5% porosity, remarkable shape recovery (even after cycling compressions with 90% deformations), excellent resistance to water intrusion, thermal diffusion stability, and high strength and stiffness. They remarkably reduce the coefficient of thermal expansion and dielectric constant of polymeric poly(methyl methacrylate) composites, greatly contribute to their thermal conductivity improvement, and effectively limit polymeric composite softening at elevated temperatures. The foams also demonstrate high-capacity adsorption-separation and removal ability for a wide range of oils and organic chemicals in oil/water systems and reliable recovery under their cycling usage as organic adsorbers. These created multifunctional foams should be valuable in many high-end practical applications.

The discovery of two-dimensional materials became possible due to the mechanical cleavage technique. Despite its simplicity, the as-cleaved materials demonstrated surprising macrocontinuity, 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. Our technique demonstrates layer number selective cleavage, from a monolayer to double layer and up to 23 atomic layers. In situ observations combined with molecular dynamics simulations reveal unique layer-dependent bending behaviours, from spontaneous rippling (o5 atomic layers) to homogeneous curving (B 10 layers) and finally to kinking (20 or more layers), depending on the competition of strain energy and interfacial energy.

1The atomic structure and physical properties of few-layered 111 oriented diamond nanocrystals (diamanes), covered by hydrogen atoms from both sides are studied using electronic band structure calculations. It was shown that energy stability linear increases upon increasing of the thickness of proposed structures. All 2D carbon films display direct dielectric band gaps with nonlinear quantum confinement response upon the thickness. Elastic properties of diamanes reveal complex dependence upon increasing of the number of 111 layers. All theoretical results were compared with available experimental data.