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Integration of twist-phase-matched van der Waals flakes on optical fibre ends enables efficient nonlinear optical processes, including second-harmonic generation and parametric downconversion, and the fabrication of a frequency-doubling ultrafast laser.

Understanding ice crystallization at the molecular level remains a challenge. Here, the authors use graphene-based in-situ cryo-TEM to show how vapor deposition leads to polymorphic ice formation controlled by surface energy.

Double-walled carbon nanotubes are a convenient system for studying quantum mechanical interactions in distinct but coupled nanostructures. Liu et al.characterize the coupling between radial-breathing mode oscillations of inner and outer walls of many double-walled nanotubes of different diameter and chirality.

The monolayer transition-metal dichalcogenide molybdenum disulphide has recently attracted attention owing to its distinctive electronic properties. Cao and co-workers present numerical evidence suggesting that circularly polarized light can preferentially excite a single valley in the band structure of this system.

The melting temperature of hydrogen drops at high pressures, which suggests the possible emergence of a low-temperature liquid state of metallic hydrogen. Chen et al.confirm the existence of this phase in simulations and show how the quantum motion of the protons has a critical role in its stabilization.

Ferroelectric materials are characterized by a spontaneous polarization, which in practical applications is manipulated by an electric field. This study examines how defects affect the switching with atomic resolution, by usingin situaberration-corrected transmission electron microscopy.

One-dimensional materials such as carbon nanotubes have many applications, but not all of their properties can be described in the same way as for conventional media. Here, the authors devise a method to measure the complex optical susceptibility in a 1D nanomaterial and demonstrate it for carbon nanotubes.

Resolving the internal structure of water molecules adsorbed on solid surfaces is challenging. Submolecular-resolution imaging of individual water monomers and tetramers on NaCl(001) films supported by a Au(111) substrate is now reported. The molecular orbitals of adsorbed water were directly visualized, which lead to the discrimination between the orientation of the monomers and the tetramers H-bond directionality.

A mechanical exfoliation method for producing freestanding metal oxide ultrathin flakes is reported. The flakes can be transferred and integrated with 2D materials, providing a platform to investigate the fundamental properties of ultrathin metal oxides.

Angle tunability in twisted bilayer graphene is crucial in promoting its applications of twistronics. Here an angle replication strategy is developed to obtain centimetre-scale bilayer graphene with arbitrary twist angles.

 Centimetre-sized single-crystal rhombohedral boron nitride layers are achieved through bevel-edge epitaxy, and the resulting material exhibits robust, homogeneous and switchable ferroelectricity with a high Curie temperature.

Tracking the formation of cubic ice (ice Ic) using transmission electron microscopy and low-dose imaging shows preferential nucleation of ice Ic at low-temperature interfaces and two types of stacking disorder.

Varying growth temperatures enables the tuning of the degree of disorder, which is fully described by the absence/presence of medium-range order and temperature-dependent densities of nanocrystallites, and electrical conductivity in amorphous monolayer carbon films.

Isothermal dissolution–diffusion–precipitation of carbon drives continuous epitaxial growth of single-crystal multilayer graphene.

CIM-seq offers an unsupervised deconvolution method to profile cell–cell interactions by sequencing cell multiplets of a given tissue, and was employed to analyze diverse tissues such as the intestinal epithelium, lung and spleen.

Multiwalled boron nitride nanotubes, featuring coherently stacked structures with monochirality, homo-handedness and unipolarity among the component tubes, show a large nonlinear chiroptical response.

Active species such as hydrogen and oxygen are commonly introduced into reactors to control the growth of two-dimensional materials. Now, the presence of fluorine—released by the decomposition of a metal fluoride sheet—has also been shown to modulate the growth kinetics of graphene, h-BN and WS₂.

The anomalous photovoltaic effect in polar materials offers a promising alternative to overcome the limits of conventional photovoltaics. Here, the authors report spontaneous photocurrent generation in Janus MoSSe monolayers, showing responsivities up to 3 mA/W and response times down to 50 ps.

The large-area growth of 2D transition metal dichalcogenides (TMDs) requires a precise control of metal and chalcogen precursors. Here, the authors implement a strategy using active chalcogen monomer supply to grow monolayer TMDs and their alloys, showing low defect density and improved optoelectronic properties.

Large-area single-crystal high-index copper and nickel foils with several types of facet are fabricated using mild pre-oxidation of the metal foil surface followed by annealing in a reducing atmosphere.

Water structures at the electrolyte and electrode interfaces are crucial for electrochemical reactions. Here, the authors report that alkali metal cations can modify two-dimensional water networks at charged surfaces, impacting both reaction kinetics and efficiency.

The results of simultaneous measurements of the structure and optical properties of more than 200 single-walled carbon nanotubes are reported and included in an atlas that allows the chiral index of any single-walled nanotube to be determined from a measurement of its optical resonances, and vice versa.

Single-crystal graphene can be grown on a copper foil at a rate of 60 μm s^-1 by using an adjacent oxide substrate that continuously supplies oxygen to the surface of the copper catalyst.

The first samples of pristine graphene were obtained by 'peeling off' and epitaxial growth, but chemical approaches are more suited to large-scale production. Exfoliation, reintercalation and expansion of graphite can produce high-quality single-layer graphene sheets suspended in organic solvents, and these sheets can be made into large transparent films by Langmuir–Blodgett assembly.

A high-throughput optical imaging and spectroscopy technique has now been developed that characterizes the chirality and electronic structure of individual single-walled carbon nanotubes either on their growth substrate or in functional devices.

Electrons in graphene have a pseudospin, but controlling this degree of freedom is challenging. Evidence now suggests that the moiré superlattices arising in two-dimensional heterostructures can be used to electrically manipulate pseudospins.

Two concentric carbon nanotubes don’t need to have a common finite unit cell. Absorption spectra of such incommensurate double-walled carbon nanotubes reveal strong hybridization of the electron wavefunctions — unusual for van der Waals-coupled structures. The observations can be rationalized by zone folding the electronic structure of twisted-and-stretched graphene bilayers.

Scanning probe microscopy has been extensively applied to probe interfacial water but the probes tend to disturb the structure of water easily. Here, the authors report submolecular-resolution imaging of water clusters within the nearly non-invasive region by qPlus noncontact atomic force microscopy.

The epitaxial growth of large single-crystal hexagonal boron nitride monolayers on low-symmetry copper foils is demonstrated.

A dual-coupling-guided growth mechanism enables the realization of wafer-scale single-crystal WS₂ on vicinal a-plane sapphire.

This Review examines conventional epitaxial growth of 2D van der Waals materials, focusing on in-plane single-crystal monolayer growth and out-of-plane homostructure fabrication. It covers nucleation and orientation control, quality control measures, and homogeneous multilayer and twisted homostructure growth techniques, providing systematic insights for on-demand fabrication of 2D van der Waals materials and their industrial device manufacturing.