Considerable efforts have been devoted to enhancing the photocatalytic activity and solar energy utilization of photocatalysts. The fabrication of type II heterostructures plays an important role in photocatalysts modification and has been extensively studied. In this review, we briefly trace the application of type II heterostructured semiconductors in the area of environmental remediation and water splitting, summarize major fabrication methods, describe some of the progress and resulting achievements, and discuss the future prospects. The scope of this review covers a variety of type II heterostructures, focusing particularly on TiO2 and ZnO based visible light driven type II 0D and 1D heterostructured photocatalysts. Some other low dimensional nanomaterials which have shown high-performance photocatalysis are also presented. We expect this review to provide a guideline for readers to gain a clear picture of fabrication and application of type II heterostructures.

The exponentially growing works on 2D materials have resulted in both high scientific interest and huge potential applications in nanocatalysis, optoelectronics, and spintronics. Of especial note is that the newly emerged and promising family of metal phosphorus trichalcogenides (MPX 3 ) contains semiconductors, metals, and insulators with intriguing layered structures and architectures. The bandgaps of the members in this family range from 1.3 to 3.5 eV, significantly enriching the application of 2D materials in the broad wavelength spectrum. In this review, emphasizing their remarkable structural, physicochemical, and magnetic properties, as well as the numerous applications in various fields, the innovative progress on layered MPX 3 crystals is summarized. Different from other layered materials, these crystals will advance a fascinating frontier in magnetism and spintronic devices with their especially featured atomic layered nanosheets. Thus, their crystal and electronic structures, along with some related researches in magnetism, are discussed in detail. The assortments of growth methods are then summarized. Considering their potential applications, the prominent utilization of these 2D MPX 3 nanoscrystals in catalysis, batteries, and optoelectronics is also discussed. Finally, the outlook of these kinds of layered nanomaterials is provided. Metal Phosphorus Trichalcogenidesions. Friedel [17] and Ferrand [18,19] discovered them in the late 1800s. Based on the interesting structure of these materials, significant research works were reported in the early 2000s. As expected, 2D MPX 3 phases share most of the abovementioned specific properties of 2D TMDs. According to the theoretical and experimental results, MPX 3 compounds are the most sought functional materials for their intermediate bandgaps ranging from 1.3 to 3.5 eV, [20,21] indicating their enhanced light absorption efficiency as compared to the TMD materials. In addition, their unusual intercalation-substitution or intercalation-reduction behavior as well as the incipient ionic conductivity promote their usage in Li-ion batteries, [22,23] gas storage, [24] and photo-electrochemical reactions. [25] Unlike TMDs, several MPX 3 materials show intrinsic anti-ferromagnetism below the Neel temperatures of 78 K for MnPS 3 , 116 K for FePS 3 , and 155 K for NiPS 3 . [26,27] Recently, Li et al. [28] predicted that transformation from the anti-ferromagnetism to ferromagnetism for exfoliated MnPSe 3 nanosheet will be reduced by carrier doping. And the Monte Carlo simulation reveals the Curie temperature of the doped MnPSe 3 nanosheets can reach 206 K, rendering it with potential for utilizations in spintronic devices at high temperature. Therefore, the members in the MPX 3 family have the abovementioned properties along with structural flexibility stemming from their van der Waals nature; thus, it is reasonable to assume that they will contribute to the next major frontier in 2D vdW layered materials.Herein, we emphasize on reviewing the impressive recent progress...

Owing to the excellent potential for fundamental research and technical applications in optoelectronic devices and catalytic activity for hydrogen evolution reaction (HER), transition metal dichalcogenides have recently attracted much attention. Transition metal sulfide nanostructures have been reported and demonstrated promising application in transistors and photodetectors. However, the growth of transition metal selenide nanostructures and their applications has still been a challenge. In this work, we successfully synthesized high-quality WSe2 nanotubes on carbon fibers via selenization. More importantly, through optimizing the growth conditions, ternary WS2(1–x)Se2x nanotubes were synthesized and the composition of S and Se can be systematically controlled. The as-grown WS2(1–x)Se2x nanotubes on carbon fibers, assembled as a working electrode, revealing low overpotential, high exchange current density, and small series resistance, exhibit excellent electrocatalytic properties for hydrogen evolution reaction. Our study provides the experimental groundwork for the synthesis of low-dimensional transition metal dichalcogenides and may open up exciting opportunities for their application in electronics, photoelectronics, and catalytic electrochemical reactions.

www.advmat.de www.advancedsciencenews.com production challenging. Since the discovery of the chemical vapor deposition (CVD) method as a successful approach for the growth of graphene crystals, [53,54] the method has also been expanded to the preparation of other 2D layered materials. Currently, this approach has been extended to rationally design various 2D TMD materials, such as MoS 2 nanosheets, [55][56][57][58] MoSe 2 nanosheets, [59,60] WS 2 nanosheets, [61,62] ReS 2 nanosheets, [63] and some heterostructures, [64,65] which have sparkled several interesting chemical and electronic properties. Although various 2D TMDs have been successfully grown using a facile CVD method, the intrinsic growth mechanism and the batch production of wafer-scale films, conducive to the high-performance in electronics/optoelectronics and other fields, still need more exploration. Very recently, some important progress on the synthesis of 2D TMDs, multi-heterostructures and superlattices has been realized.Herein, we concentrate on the recent progress in the synthesis of 2D TMDs and related heterostructures via the CVD method. We start with the effects of some key factors such as temperature, carrier gas, and the ratio of precursors on the synthesis of 2D TMDs via CVD technique. Then we summarize the importance of the growth substrates and the growth system to large-scale synthesis. Hence, large-scale 2D TMDs have been obtained on the basis of properly designed CVD growth. Furthermore, some recent breakthroughs in the growth of new kinds of semiconducting and metallic 2D TMDs via the CVD technique are described. The fundamental electronic properties and unique physical phenomena emanating from high quality CVD-grown TMDs are also reviewed. Finally, the controlled growth of alloys with tunable band structures, different multiheterostructures with atomically sharp interfaces and superlattices from 2D TMD crystals is analyzed, which can offer further step for the synthesis of 2D crystals and provides significantly more material systems. Lastly, we emphasize a summary of this review and the future prospects of these materials.Recently, the CVD method has been widely regarded as a technique available for growing 2D atomic crystals. Various atomically thin layered MX 2 semiconductors, such as MoS 2 , [55,66,67] WS 2 , [68] MoSe 2 , [69] MoTe 2 , [70,71] etc., have been successfully achieved by the CVD method. Through in-depth research on the growth dynamics in the CVD system, several key factors in the growth process for obtaining a large-scale, uniform monolayer MX 2 have been explored. For example, triangular WS 2 flakes were synthesized on a sapphire substrate via a CVD system, and a detailed analysis of the controllable growth behavior was given. [61] The growth system is maintained at a very low pressure during the growth process via an operating pump, which provides a uniform flow of vapor precursors and is beneficial to the uniform growth. First, the distance between the source and substrate (D ss ) was discovered to be a vital fa...

The desire for sustainable and clean energy future continues to be the concern of the scientific community. Researchers are incessantly targeting the development of scalable and abundant electro- or photo-catalysts for water splitting. Owing to their suitable band-gap and excellent stability, an enormous amount of transition-metal dichalcogenides (TMDs) with hierarchical nanostructures have been extensively explored. Herein, we present an overview of the recent research progresses in the design, characterization and applications of the TMD-based electro- or photo-catalysts for hydrogen and oxygen evolution. Emphasis is given to the layered and pyrite-phase structured TMDs encompassing semiconducting and metallic nanomaterials. Illustrative results and the future prospects are pointed out. This review will provide the readers with insight into the state-of-the-art research progresses in TMD based nanomaterials for water splitting.

Two-dimensional layered materials (2DLMs) have attracted a tremendous amount of attention as photodetectors due to their fascinating features, including high potentials in new-generation electronic devices, wide coverage of bandgaps, ability to construct van der Waals heterostructures, extraordinary light-mass interaction, strong mechanical flexibility, and the capability of enabling synthesis of 2D nonlayered materials. Until now, most attention has been focused on the well-known graphene and transition metal dichalcogenides (TMDs). However, a growing number of functional materials (more than 5619) with novel optoelectronic and electronic properties are being re-discovered, thereby widening the horizon of 2D libraries. In addition to showing common features of 2DLMs, these new 2D members may bring new opportunities to their well-known analogues, like wider bandgap coverage, direct bandgaps independence with thickness, higher mechanical flexibility, and new photoresponse phenomena. The impressive results communicated so far testify that they have shown high potentials with photodetections covering THz, IR, visible, and UV ranges with comparable or even higher performances than well-known TMDs. Here, we give a comprehensive review on the state-of-the-art photodetections of two-dimensional materials beyond graphene and TMDs. The review is organized as follows: fundamentals of photoresponse first are discussed, followed by detailed photodetections of new 2D members including both layered and non-layered ones. After that, photodiodes and hybrid structures based on these new 2D materials are summarized. Then, the integration of these 2D materials with flexible substrates is reviewed. Finally, we conclude with the current research status of this area and offer our perspectives on future developments. We hope that, through reading this manuscript, readers will quickly have a comprehensive view on this research area.

We report a high-performance field-effect transistor (FET) and phototransistor based on back-gated multilayer GaTe nanosheets. Through both electrical transport measurements at variable temperatures and first-principles calculations, we find Ga ion vacancy is the critical factor that causes high off-state current, low on/off ratio, and large hysteresis of GaTe FET at room temperature. By suppressing thermally activated Ga vacancy defects at liquid nitrogen temperature, a GaTe nanosheet FET with on/off ratio of ∼10(5), off-state current of ∼10(-12) A, and negligible gate hysteresis is successfully demonstrated. Furthermore, a GaTe phototransistor with high photogain above 2000 and high responsivity over 800 AW(-1) is achieved, as well. Our findings are of scientific importance to understand the physical nature of intrinsic GaTe transistor performance degradation and also technical significance to unlock the hurdle for practical applications of GaTe transistors in the future.

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