Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Ultrathin two-dimensional nanosheets of layered transition metal dichalcogenides (TMDs) are fundamentally and technologically intriguing. In contrast to the graphene sheet, they are chemically versatile. Mono- or few-layered TMDs - obtained either through exfoliation of bulk materials or bottom-up syntheses - are direct-gap semiconductors whose bandgap energy, as well as carrier type (n- or p-type), varies between compounds depending on their composition, structure and dimensionality. In this Review, we describe how the tunable electronic structure of TMDs makes them attractive for a variety of applications. They have been investigated as chemically active electrocatalysts for hydrogen evolution and hydrosulfurization, as well as electrically active materials in opto-electronics. Their morphologies and properties are also useful for energy storage applications such as electrodes for Li-ion batteries and supercapacitors.

http://nanotubes.rutgers.edu/PDFs/nchem_TMDs_2013.pdf

The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets

Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

Graphene-Like Two-Dimensional Materials

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Large-area MoS(2) atomic layers are synthesized on SiO(2) substrates by chemical vapor deposition using MoO(3) and S powders as the reactants. Optical, microscopic and electrical measurements suggest that the synthetic process leads to the growth of MoS(2) monolayer. The TEM images verify that the synthesized MoS(2) sheets are highly crystalline.

Synthesis of Large‐Area MoS2 Atomic Layers with Chemical Vapor Deposition

In the current study, a nanocomposite of molybdenum disulfide and graphene (MoS2/RGO) was proposed for the first time as the counter electrode (CE) catalyst in dye-sensitized solar cells (DSSCs) to speed up the reduction of triiodide (I3−) to iodide (I−). This novel catalyst was synthesized by simply mixing graphene oxide nanosheets with a solution of ammonium tetrathiomolybdate and then converting the solid intermediate into MoS2/RGO nanocomposite in a H2 flow at 650 °C. Atomic force microscopy, X-ray powder diffraction and X-ray photoemission spectroscopy confirmed that MoS2 nanoparticles were deposited onto the graphene surface. The extensive cyclic voltammograms (CV) showed that the cathodic current density of the MoS2/RGO CE was higher than those of MoS2, RGO and sputtered Pt CEs, due to the increased active surface area of the former. Moreover, the peak current densities of the MoS2/RGO CE showed no sign of degradation after 100 consecutive CV tests, suggesting the great electrochemical stability of the MoS2/RGO CE. Furthermore, the MoS2/RGO CE demonstrated an impressively low charge-transfer resistance (0.57 Ω cm2) for I3− reduction. Finally, the DSSC assembled with the MoS2/RGO CE showed a high power conversion efficiency of 6.04%, which is comparable to the DSSC with a Pt CE (6.38%).

Facile synthesis of MoS2/graphene nanocomposite with high catalytic activity toward triiodide reduction in dye-sensitized solar cells

Organic room temperature phosphorescence (RTP) materials with ultralong lifetime possess the remarkable advantage in bioimaging for elimination of background noise by characteristic time scale. However, most of RTP luminogens need to be excited by the harmful ultraviolet (UV) lamp, and exhibit green or yellow emission with shallow tissue penetration, constraining the in vivo bioimaging for further application in clinical diagnosis and pathological study. In this text, the much safer excitation process by sunlight and mobile phone flashlight is realized by organic luminogens with various electronic pull–push systems. Moreover, the bright red RTP emission with lifetime up to 344 ms is achieved by optimizing molecular geometry and electronic property. Especially, the mobile phone flashlight‐excited red afterglow imaging of lymph nodes in living mice has been realized for the first time, affording a safe and conventional approach to achieve the afterglow imaging of living mice with deep issue penetration and high signal‐to‐noise ratios.

Mobile Phone Flashlight‐Excited Red Afterglow Bioimaging

Designing an earth-abundant electrode material with high activity and durability is a major challenge for water splitting to produce clean and green hydrogen energy. In this study, we reported a...

3D Hierarchical Network Derived from 2D Fe-doped NiSe Nanosheets/Carbon Nanotubes with Enhanced OER Performance for Overall Water Splitting

The development of organic room-temperature phosphorescence (RTP) materials with ultralong lifetimes is desired but remains challenging, especially those with blue RTP emission. Herein, through the cycloalkyl modification of phenothiazine-5,5-dioxide (CsO)...

Kai-Di Chang

Papers

Synthesis of Large‐Area MoS2 Atomic Layers with Chemical Vapor Deposition

Facile synthesis of MoS2/graphene nanocomposite with high catalytic activity toward triiodide reduction in dye-sensitized solar cells

Mobile Phone Flashlight‐Excited Red Afterglow Bioimaging

3D Hierarchical Network Derived from 2D Fe-doped NiSe Nanosheets/Carbon Nanotubes with Enhanced OER Performance for Overall Water Splitting

Ultralong Blue Room-temperature Phosphorescence by Cycloalkyl Engineering