Highly Efficient Ionic Photocurrent Generation through WS2‐Based 2D Nanofluidic Channels

The unique feature of nacre‐like 2D layered materials provides a facile, yet highly efficient way to modulate the transmembrane ion transport from two orthogonal transport directions, either vertical or horizontal. Recently, light‐driven active transport of ionic species in synthetic nanofluidic systems attracts broad research interest. Herein, taking advantage of the photoelectric semiconducting properties of 2D transition metal dichalcogenides, the generation of a directional and greatly enhanced cationic flow through WS₂‐based 2D nanofluidic membranes upon asymmetric visible light illumination is reported. Compared with graphene‐based materials, the magnitude of the ionic photocurrent can be enhanced by tens of times, and its photo‐responsiveness can be 2–3.5 times faster. This enhancement is explained by the coexistence of semiconducting and metallic WS₂ nanosheets in the hybrid membrane that facilitates the asymmetric diffusion of photoexcited charge carriers on the channel wall, and the high ionic conductance due to the neat membrane structure. To further demonstrate its application, photonic ion switches, photonic ion diodes, and photonic ion transistors as the fundamental elements for light‐controlled nanofluidic circuits are further developed. Exploring new possibilities in the family of liquid processable colloidal 2D materials provides a way toward high‐performance light‐harvesting nanofluidic systems for artificial photosynthesis and sunlight‐driven desalination.     

Low‐Temperature Wafer‐Scale Deposition of Continuous 2D SnS2 Films

Semiconducting 2D materials, such as SnS₂, hold immense potential for many applications ranging from electronics to catalysis. However, deposition of few‐layer SnS₂ films has remained a great challenge. Herein, continuous wafer‐scale 2D SnS₂ films with accurately controlled thickness (2 to 10 monolayers) are realized by combining a new atomic layer deposition process with low‐temperature (250 °C) postdeposition annealing. Uniform coating of large‐area and 3D substrates is demonstrated owing to the unique self‐limiting growth mechanism of atomic layer deposition. Detailed characterization confirms the 1T‐type crystal structure and composition, smoothness, and continuity of the SnS₂ films. A two‐stage deposition process is also introduced to improve the texture of the films. Successful deposition of continuous, high‐quality SnS₂ films at low temperatures constitutes a crucial step toward various applications of 2D semiconductors.     

A Free‐Standing and Self‐Healable 2D Supramolecular Material Based on Hydrogen Bonding: A Nanowire Array with Sub‐2‐nm Resolution

In many 2D materials reported thus far, the forces confining atoms in a 2D plane are often strong interactions, such as covalent bonding. Herein, the first demonstration that hydrogen (H)‐bonding can be utilized to assemble polydiacetylene (a conductive polymer) toward a 2D material, which is stable enough to be free‐standing, is shown. The 2D material is well characterized by a large number of techniques (mainly different microscopy techniques). The H‐bonding allows splitting of the material into ribbons, which can reassemble, similar to a zipper, leading to the first example of a healable 2D material. Moreover, such technology can easily create 2D, organic, conductive nanowire arrays with sub‐2‐nm resolution. This material may have potential applications in stretchable electronics and nanowire cross‐bar arrays.     

Twinned Growth of Metal‐Free,Triazine‐Based Photocatalyst Films as Mixed‐Dimensional (2D/3D) van der Waals Heterostructures

Design and synthesis of ordered, metal‐free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed‐dimensional (2D/3D) metal‐free van der Waals (vdW) heterostructures based on triazine (C₃N₃) linkers grow as large area, transparent yellow‐orange membranes on copper surfaces from solution. The membranes have an indirect band gap (E _g,opt = 1.91 eV, E _g,elec = 1.84 eV) and are moderately porous (124 m² g^?1). The material consists of a crystalline 2D phase that is fully sp² hybridized and provides structural stability, and an amorphous, porous phase with mixed sp²–sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one‐pot reaction mixture: unprecedented for metal‐free frameworks and a direct consequence of on‐catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the material is capable of metal‐free, light‐induced hydrogen evolution from water without the need for a noble metal cocatalyst (34 µmol h^?1 g^?1 without Pt). The results highlight that twinned growth mechanisms are observed in the realm of “wet” chemistry, and that they can be used to fabricate otherwise challenging 2D/3D vdW heterostructures with composite properties.