Site‐Selective and van der Waals Epitaxial Growth of Rhenium Disulfide on Graphene

The surface property of growth substrate imposes significant influence in the growth behaviors of 2D materials. Rhenium disulfide (ReS₂) is a new family of 2D transition metal dichalcogenides with unique distorted 1T crystal structure and thickness‐independent direct bandgap. The role of growth substrate is more critical for ReS₂ owing to its weak interlayer coupling property, which leads to preferred growth along the out‐of‐plane direction while suppressing the uniform in‐plane growth. Herein, graphene is introduced as the growth substrate for ReS₂ and the synthesis of graphene/ReS₂ vertical heterostructure is demonstrated via chemical vapor deposition. Compared with the rough surface of SiO₂/Si substrate with dangling bonds which hinders the uniform growth of ReS₂, the inert and smooth surface nature of graphene sheet provides a lower energy barrier for migration of the adatoms, thereby promoting the growth of ReS₂ on the graphene surface along the in‐plane direction. Furthermore, patterning of the graphene/ReS₂ heterostructure is achieved by the selective growth of ReS₂, which is attributed to the strong binding energy between sulfur atoms and graphene surface. The fundamental studies in the role of graphene as the growth template in the formation of van der Waals heterostructures provide better insights into the synthesis of 2D heterostructures.     

Edge‐Epitaxial Growth of 2D NbS2‐WS2 Lateral Metal‐Semiconductor Heterostructures

2D metal‐semiconductor heterostructures based on transition metal dichalcogenides (TMDs) are considered as intriguing building blocks for various fields, such as contact engineering and high‐frequency devices. Although, a series of p–n junctions utilizing semiconducting TMDs have been constructed hitherto, the realization of such a scheme using 2D metallic analogs has not been reported. Here, the synthesis of uniform monolayer metallic NbS₂ on sapphire substrate with domain size reaching to a millimeter scale via a facile chemical vapor deposition (CVD) route is demonstrated. More importantly, the epitaxial growth of NbS₂‐WS₂ lateral metal‐semiconductor heterostructures via a “two‐step” CVD method is realized. Both the lateral and vertical NbS₂‐WS₂ heterostructures are achieved here. Transmission electron microscopy studies reveal a clear chemical modulation with distinct interfaces. Raman and photoluminescence maps confirm the precisely controlled spatial modulation of the as‐grown NbS₂‐WS₂ heterostructures. The existence of the NbS₂‐WS₂ heterostructures is further manifested by electrical transport measurements. This work broadens the horizon of the in situ synthesis of TMD‐based heterostructures and enlightens the possibility of applications based on 2D metal‐semiconductor heterostructures.     

Graphene‐Assisted Growth of Patterned Perovskite Films for Sensitive Light Detector and Optical Image Sensor Application

Controlled growth of high‐quality patterned perovskite films on a large scale is essentially required for the application of this class of materials in functional integrated devices and systems. Herein, graphene‐assisted hydrophilic–hydrophobic surface‐induced growth of Cs‐doped FAPbI₃ perovskite films with well‐patterned shapes by a one‐step spin‐coating process is developed. Such a facile fabrication technique is compatible with a range of spin‐coated perovskite materials, perovskite manufacturing processes, and substrates. By employing this growing method, controllable perovskite photodetector arrays are realized, which have not only prominent photoresponse properties with a responsivity and specific detectivity of 4.8 AW^?1 and 4.2 × 10¹² Jones, respectively, but also relatively small pixel‐to‐pixel variation. Moreover, the photodetectors array can function as an effective visible light image sensor with a decent spatial resolution. Holding the above merits, the proposed technique provides a convenient and effective pathway for large‐scale preparation of patterned perovskite films for multifunctional application purposes.     

Atomic Interface Engineering and Electric‐Field Effect in Ultrathin Bi2MoO6 Nanosheets for Superior Lithium Ion Storage

Ultrathin 2D materials can offer promising opportunities for exploring advanced energy storage systems, with satisfactory electrochemical performance. Engineering atomic interfaces by stacking 2D crystals holds huge potential for tuning material properties at the atomic level, owing to the strong layer–layer interactions, enabling unprecedented physical properties. In this work, atomically thin Bi₂MoO₆ sheets are acquired that exhibit remarkable high‐rate cycling performance in Li‐ion batteries, which can be ascribed to the interlayer coupling effect, as well as the 2D configuration and intrinsic structural stability. The unbalanced charge distribution occurs within the crystal and induces built‐in electric fields, significantly boosting lithium ion transfer dynamics, while the extra charge transport channels generated on the open surfaces further promote charge transport. The in situ synchrotron X‐ray powder diffraction results confirm the material's excellent structural stability. This work provides some insights for designing high‐performance electrode materials for energy storage by manipulating the interface interaction and electronic structure.     

Fast and Highly Sensitive Ionic‐Polymer‐Gated WS2–Graphene Photodetectors

The combination of graphene with semiconductor materials in heterostructure photodetectors enables amplified detection of femtowatt light signals using micrometer‐scale electronic devices. Presently, long‐lived charge traps limit the speed of such detectors, and impractical strategies, e.g., the use of large gate‐voltage pulses, have been employed to achieve bandwidths suitable for applications such as video‐frame‐rate imaging. Here, atomically thin graphene–WS₂ heterostructure photodetectors encapsulated in an ionic polymer are reported, which are uniquely able to operate at bandwidths up to 1.5 kHz whilst maintaining internal gain as large as 10⁶. Highly mobile ions and the nanometer‐scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of the graphene over an unprecedented range at the interface with WS₂. Responsivity R = 10⁶ A W^?1 and detectivity D* = 3.8 × 10¹¹ Jones are observed, approaching that of single‐photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video‐frame‐rate imaging applications.     

Alignment and Graphene‐Assisted Decoration of Lyotropic Chromonic Liquid Crystals Containing DNA Origami Nanostructures

Composites of DNA origami nanostructures dispersed in a lyotropic chromonic liquid crystal are studied by polarizing optical microscopy. The homogeneous aqueous dispersions can be uniformly aligned by confinement between two glass substrates, either parallel to the substrates owing to uniaxial rubbing or perpendicular to the substrates using ozonized graphene layers. These opportunities of uniform alignment may pave the way for tailored anisometric plasmonic DNA nanostructures to photonic materials. In addition, a decorated texture with nonuniform orientation is observed on substrates coated with pristine graphene. When the water is allowed to evaporate slowly, microscopic crystal needles appear, which are aligned along the local orientation of the director. This decoration method can be used for studying the local orientational order and the defects in chromonic liquid crystals.     

Graphene‐Like MoS2/Graphene Composites: Cationic Surfactant‐Assisted Hydrothermal Synthesis and Electrochemical Reversible Storage of Lithium

A cationic surfactant‐assisted hydrothermal route is developed for the facile synthesis of graphene‐like MoS₂/graphene (GL‐MoS₂/G) composites based on the hydrothermal reduction of Na₂MoO₄ and graphene oxide sheets with L‐cysteine in the presence of cetyltrimethylammonium bromide (CTAB), following by annealling in N₂ atmosphere. The GL‐MoS₂/G composites are characterized by X‐ray diffraction, electron microscopy, high‐resolution transmission electron microscopy, and Raman spectroscopy. The effects of CTAB concentration on the microstructures and electrochemical performances of the composites for reversible Li⁺ storage are investigated. It is found that the layer number of MoS₂ sheets decreases with increasing CTAB concentration. The GL‐MoS₂ sheets in the composites are few‐layer in the case of 0.01～0.03 mol L^?1 CTAB of hydrothermal solution and single‐layer in the case of 0.05 mol L^?1 CTAB. The GL‐MoS₂/G composites prepared with 0.01–0.02 mol·L^?1 of CTAB solution exhibit a higher reversible capacity of 940–1020 mAh g^?1, a greater cycle stability, and a higher rate capability than other samples. The exceptional electrochemical performance of GL‐MoS₂/G composites for reversible Li⁺ storage could be attributed to an effective integration of GL‐MoS₂ sheets and graphene that maximizes the synergistic interaction between them.