As an emerging class of semiconducting transition metal dichalcogenides (TMDCs), two-dimensional (2D) rhenium dichalcogenides (ReX₂, X = S or Se) have recently aroused great research interest due to their unique anisotropic structure (1T′ phase), and the related novel properties and applications. Recently, many efforts have been devoted to the controllable syntheses of high-quality monolayer or few-layer ReX₂ flakes/films by chemical vapor deposition (CVD), wherein the metallic Au foil is found to be a unique substrate, due to the relatively strong interfacial coupling between monolayer ReX₂ and Au. And the conductive nature of Au enables in situ characterizations of the as-grown ReX₂ samples, which is essential for exploring the fundamental properties and internal growth mechanisms. Hereby, this review focuses on the recent progresses on the CVD syntheses and in situ characterizations of high-quality monolayer ReX₂ flakes/films and their heterostructures with graphene on Au foils. The effects of Au foils on improving the crystal quality and inducing the growth of monolayer ReX₂ single crystals are intensively addressed. The crystallinity, domain morphology, atomic and electronic structures, as well as the growth behaviors of monolayer ReX₂ flakes/films and graphene/ReX₂ heterostructures on Au revealed by in situ characterization techniques are also highlighted. As contrasts, the growth behaviors of monolayer or few-layer ReX₂ on insulating substrates are also discussed. Besides, the potential applications of 2D ReX₂ in new-generation electronic, optoelectronic devices, and energy-related fields are also introduced. Finally, future research directions are also prospected for propelling the practical applications of 2D ReX₂ materials in more versatile fields.

The emerging two-dimensional (2D) platinum disulfide (PtS₂) has driven increasing attentions due to its high electron mobility, good air-stability, and strong interlayer interaction which leads to a widely tunable electronic structure. However, a detailed study on its covalent-like layer-dependent properties remains infant. Herein, we demonstrate the successful production of ultrathin 1T-PtS₂ ribbons with thickness centralized almost at monolayer 1L–4L and large domain size up to 210 µm on Au foils using chemical vapor deposition (CVD) technique, which enables macro- and microscopic study of its extraordinary layer-dependent features with precise control of the number of layers. Using electron energy loss spectroscopy (EELS) and optical pump-probe spectroscopy (OPPS), we reveal that both the electron and ultrafast optical absorption signals of the as-grown 2D PtS₂ show strong nonlinear layer-dependent responses which manifest discriminated transition in 1L–4L PtS₂ ribbons. The layer-dependent nonlinear response of 2D PtS₂ can be well interpreted in the frame of calculated electron and phonon structures. These achievements offer a platform for successfully fabricating large-sized ultrathin 2D PtS₂ and facilitating our knowledge about its electronic and optoelectronic properties.

Growing high quality graphene films directly on glass by chemical vapor deposition (CVD) meets a growing demand for constructing high-performance electronic and optoelectronic devices. However, the graphene synthesized by prevailing methodologies is normally of polycrystalline nature with high nucleation density and limited domain size, which significantly handicaps its overall properties and device performances. Herein, we report an oxygen-assisted CVD strategy to allow the direct synthesis of 6-inch-scale graphene glass harvesting markedly increased graphene domain size (from 0.2 to 1.8 μm). Significantly, as-produced graphene glass attains record high electrical conductivity (realizing a sheet resistance of 900 Ω·sq^-1 at a visible-light transmittance of 92%) amongst the state-of-the-art counterparts, readily serving as transparent electrodes for fabricating high-performance optical filter devices. This work might open a new avenue for the scalable production and application of emerging graphene glass materials with high quality and low cost.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have emerged as perfect platforms for developing applications in nano-electronics, catalysis, energy storage and environmental-related fields due to their superior properties. However, the low-cost, batch production of high-quality 2D TMDCs remains a huge challenge with the existing synthetic strategies. Herein, we present a scalable chemical vapor deposition (CVD) approach for the batch production of high-quality MoS₂ nanosheet powders, by using naturally abundant, water-soluble and recyclable NaCl crystal powders as templates. The high-quality MoS₂ nanosheets powders are achieved by a facile water dissolution-filtration process, by virtue of the excellent dispersibility of the as-grown products in water. The internal mechanism for the scalable synthesis strategy is explored. The applications of the MoS₂ nanosheets powders are also demonstrated as catalysts or adsorbents in hydrogen evolution reaction (HER) and organic dyes adsorption, respectively. This work should hereby pave ways for the mass production and application of powdery TMDCs in energetic and environmental related fields.

Direct growth of large area uniform graphene on functional insulating materials is essential for engineering versatile applications of graphene. However, the existing synthesis approaches can hardly avoid the generation of non-uniform multilayer graphene along the gas flow direction, affording huge challenges for further scaling up. Herein, by exploiting the molten state of soda-lime glass, we have accomplished the direct growth of large area uniform (up to 30 cm × 6 cm) graphene via a facile chemical vapor deposition route on low cost soda-lime glass. The use of molten glass eliminates the chemically active sites (surface corrugations, scratches, defects), and improves the mobility of carbon precursors, affording uniform nucleation and growth of monolayer graphene. Intriguingly, thus-obtained graphene acts as an ideal coating layer for the surface crystallographic modification of soda-lime glass, making it epitaxy substrates for synthesizing high-quality PbI₂ nanoplates and continues films. Accordingly, a prototype photodetector was fabricated to present excellent photoelectrical properties of high responsivity (~ 600 on/off current ratio) and fast response speed (18 μs). This work hereby paves ways for the batch production and the direct applications of graphene glass as platforms for constructing high performance electronic and optoelectronic devices.

Exploring high-efficient catalysts for hydrogen evolution reaction (HER) has become very urgent for resolving the energy related issues. Recently, two-dimensional layered MoS₂ and its heterostructures with graphene or other traditional photocatalysts have presented great potentials for electrocatalytic and photocatalytic HER applications. On-site investigations of the atomic-scale structures and local electronic properties of the catalytically active sites are the key points for understanding the internal mechanisms, which however are hard to be achieved from the practical systems. Hereby, this review focuses on the recent progresses on the on-site scanning tunneling microscopy/spectroscopy investigations of the atomic structures and electronic properties of the ultrahigh-vacuum deposited and chemical vapor deposition (CVD) synthesized monolayer MoS₂ and MoS₂/graphene vertical stacks on the electrodes of Au(111) and Au foils. The correlations between the respective HER activities, edge types and edge electronic states are comparatively introduced. Secondly, this review also introduces the photocatalytic HER applications of CVD-grown MoS₂/WS₂ and WS₂/MoS₂ vertical stacks on Au foils, mainly considering of their type-II band alignments and the novel interlayer charge transfer behaviors. Finally, future research directions are also proposed for in-depth understanding of the catalytic mechanism, as well as for exploring more efficient HER catalysts.

Vertical heterostructures based on two-dimensional (2D) materials have attracted widespread interest for their numerous applications in electronic and optoelectronic devices. Herein, we report the direct construction of an abnormal graphene/ReSe₂ stack on Au foils by a two-step chemical vapor deposition (CVD) strategy. During the second growth stage, monolayer ReSe₂ is found to preferentially evolve at the interface between the first-grown graphene layer and the Au substrate. The unusual stacking behavior is unraveled by in-situ pcutting openq the upper graphene from the defects to expose the lower ReSe₂ using scanning tunneling microscopy (STM). From combination of these results with density functional theory calculations, the domain boundaries and edge sites of graphene are proposed to be adsorption sites for Re and Se precursors, further facilitating the growth of ReSe₂ at the van der Waals gap of graphene/Au. This work hereby offers an intriguing strategy for obtaining vertical 2D heterostructures featured with an ultra-clean interface and a designed stacking geometry.

A high-performance heterojunction photodetector is formed by combining an n-type Si substrate with p-type monolayer WSe₂ obtained using physical vapor deposition. The high quality of the WSe₂/Si heterojunction is demonstrated by the suppressed dark current of 1 nA and the extremely high rectification ratio of 10⁷. Under illumination, the heterojunction exhibits a wide photoresponse range from ultraviolet to near-infrared radiation. The introduction of graphene quantum dots (GQDs) greatly elevates the photodetective capabilities of the heterojunction with strong light absorption and long carrier lifetimes. The GQDs/WSe₂/Si heterojunction exhibits a high responsivity of ~ 707 mA·W^–1, short response time of 0.2 ms, and good specific detectivity of ~ 4.51 × 10⁹ Jones. These properties suggest that the GQDs/WSe₂/Si heterojunction holds great potential for application in future high-performance photodetectors.

Vertically-oriented graphene (VG) has many advantages over flat lying graphene, including a large surface area, exposed sharp edges, and non-stacking three-dimensional geometry. Recently, VG nanosheets assembled on specific substrates have been used for applications in supersensitive gas sensors and high-performance energy storage devices. However, to realize these intriguing applications, the direct growth of high-quality VG on a functional substrate is highly desired. Herein, we report the direct synthesis of VG nanosheets on traditional soda-lime glass due to its low-cost, good transparency, and compatibility with many applications encountered in daily life. This synthesis was achieved by a direct-current plasma enhanced chemical vapor deposition (dc-PECVD) route at 580 ℃, which is right below the softening point of the glass, and featured a scale-up size ~6 inches. Particularly, the fabricated VG nanosheets/glass hybrid materials at a transmittance range of 97%–34% exhibited excellent solarthermal performances, reflected by a 70%–130% increase in the surface temperature under simulated sunlight irradiation. We believe that this graphene glass hybrid material has great potential for use in future transparent "green-warmth" construction materials.

Controlled synthesis of structurally anisotropic rhenium diselenide (ReSe₂) with macroscopically uniform and strictly monolayer thickness as well as tunable domain shape/size is of great interest for electronics-, optoelectronics-, and electrocatalysis-related applications. Herein, we describe the controlled synthesis of uniform monolayer ReSe₂ flakes with variable morphology (sunflower- or truncated-triangle-shaped) on SiO₂/Si substrates using different ambient-pressure chemical vapor deposition (CVD) setups. The prepared polycrystalline ReSe₂ flakes were transferred intact onto Au foil electrodes and tested for activity in the hydrogen evolution reaction (HER). Interestingly, compared to the compact truncated-triangle-shaped ReSe₂ flakes, their edge-abundant sunflower-shaped counterparts exhibited superior electrocatalytic HER activity, featuring a relatively low Tafel slope of ~76 mV/dec and an exchange current density of 10.5 μA/cm². Thus, our work demonstrates that CVD-grown ReSe₂ is a promising two-dimensional anisotropic material for applications in the electrocatalytic HER.