A new phototransistor based on the mechanically exfoliated single-layer MoS(2) nanosheet is fabricated, and its light-induced electric properties are investigated in detail. Photocurrent generated from the phototransistor is solely determined by the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation can be completely finished within ca. 50 ms, and it shows good stability. Especially, the single-layer MoS(2) phototransistor exhibits a better photoresponsivity as compared with the graphene-based device. The unique characteristics of incident-light control, prompt photoswitching, and good photoresponsivity from the MoS(2) phototransistor pave an avenue to develop the single-layer semiconducting materials for multifunctional optoelectronic device applications in the future.

Hydrogen evolution reaction (HER) on earth-abundant molybdenum disulfide (MoS 2) in acidic media is a robust process, but is kinetically retarded in alkaline media. Thus, improving the sluggish kinetics for HER in alkaline media is crucial for advancing the performance of water-alkali electrolyzers. Here, we demonstrate a dramatic enhancement of HER kinetics in base by judiciously hybridizing vertical MoS 2 sheets with another earth-abundant material, layered double hydroxide (LDH). The resultant MoS 2 /NiCo-LDH hybrid exhibits an extremely low HER overpotential of 78 mV at 10 mA/cm 2 and a low Tafel slope of 76.6 mV/dec in 1 M KOH solution. At the current density of 20 mA/cm 2 or even higher, the MoS 2 /NiCo-LDH composite can operate without degradation for 48 hr. This work not only brought forth a cost-effective and robust electrocatalyst, but more generally opened up new vistas for developing high-performance electrocatalysts in unfavorable media recalcitrant to conventional catalyst design.

energy conversion and storage. [1,2] Developing efficient electrocatalysts that can effectively enhance the sluggish kinetic processes are particularly important to the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at low overpotentials. [3,4] Platinum group metals and noble metal oxides (e.g., IrO 2 , RuO 2 ) are considered as pioneering HER and OER catalysts, respectively. However, the large-scale applications are limited by the scarcity and high cost of these materials. [5,6] Recently, a great deal of effort and progress has been made toward the development of earth-abundant, highly efficient, and durable HER and OER catalysts, such as transition metal chalcogenides, [7][8][9] phosphides, [10][11][12] nitrides, [13][14][15] and carbides [16][17][18] (for HER), and transition metal oxide, [19][20][21] hydroxide/oxyhydroxide, [22][23][24] phosphate, [25][26][27] and carbon materials [28][29][30] (for OER). Due to the thermodynamic convenience and practical application in proton-exchange membrane or alkaline electrolyzers, these HER and OER catalysts generally exhibit high activity in strongly acidic and basic conditions, separately; thus pairing the two type catalysts in an integrated electrolyzer with high efficiency and stability for overall water splitting is difficult due to the mismatch of electrolyte pH. [31,32] There is Developing efficient, durable, and earth-abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing largescale water splitting. The authors report that FeB 2 nanoparticles, prepared by a facile chemical reduction of Fe 2+ using LiBH 4 in an organic solvent, are a superb bifunctional electrocatalyst for overall water splitting. The FeB 2 electrode delivers a current density of 10 mA cm −2 at overpotentials of 61 mV for hydrogen evolution reaction (HER) and 296 mV for oxygen evolution reaction (OER) in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV dec −1 , respectively. The electrode can sustain the HER at an overpotential of 100 mV for 24 h and OER for 1000 cyclic voltammetry cycles with negligible degradation. Density function theory calculations demonstrate that the boron-rich surface possesses appropriate binding energy for chemisorption and desorption of hydrogen-containing intermediates, thus favoring the HER process. The excellent OER activity of FeB 2 is ascribed to the formation of a FeOOH/ FeB 2 heterojunction during water oxidation. An alkaline electrolyzer is constructed using two identical FeB 2 -NF electrodes as both anode and cathode, which can achieve a current density of 10 mA cm −2 at 1.57 V for overall water splitting with a faradaic efficiency of nearly 100%, rivalling the integrated state-of-the-art Pt/C and RuO 2 /C.

This article provides an overview on the design, fabrication and characterization of the most widely used cathode buffer layers (CBLs) constructed with pristine zinc oxide (ZnO), doped-ZnO, and ZnO-based composites as well as the surface modified ZnO-based CBLs for the improvement of power conversion efficiency (PCE) and long-term device stability of inverted polymer solar cells (PSCs). To achieve high PCE in inverted PSCs, the selection of an appropriate material to form the high quality CBL so as to optimize the electron collection and transport is particularly important. Among the different materials for CBL in inverted PSCs, ZnO has attracted most extensive research in view of its relatively high electron mobility, optical transparency, ease synthesis with versatile morphologies via low cost solution methods at low temperatures, and being environmentally stable. The research has revealed that the electronic processes at the interface between ZnO CBL and polymer active layer play an important role in determining the solar cells performance, and such processes are related to the ZnO CBL in terms of its morphology, microstructure, doping and surface modification. This review attempts to give a general review to better understand the impacts of (1) morphology, (2) thickness, (3) nanostructures, (4) doping, (5) surface modification and (6) composition/hybrids of ZnO CBLs on the solar cells performance. The fundamental understanding of the rapid progress of interfacial engineering made in PSCs would also be beneficial to the development of perovskite solar cells due to similar energy level and device structures.Fig. 12 (a) Schematic illustration of device structure with ZnMgO CBL. (b) Energy levels of the components in the inverted PSCs with various ZMO CBLs. (c) Optical absorption spectra of ZMO films. The inset shows an increase in the bandgap of ZMO films with the increasing of Mg content (x). (d) J-V curve of the device with the ZMO ( x = 0.3) CBL. 48 Fig. 13 (a) Chemical structures of PTB7-Th, PC 71 BM and BisNPC60-OH, (b) Schematic illustration of the proposed cathode interlayer from XPS depth profile; (c) Energy levels diagram for ZnO, InZnO, ZnO-BisC60 and InZnO-BisC60 determined from ultraviolet photoelectron spectroscopy (UPS) and UV-Vis results and for all the components in the inverted PSCs.

Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this work, highly monodisperse CoP and Co P nanocrystals (NCs) are synthesized using a robust solution-phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal-rich Co P NCs show higher OER performance owing to easier formation of plentiful Co P@COOH heterojunctions. Density functional theory calculation results indicate that the desorption of OH* from cobalt sites is the rate-limiting step for both CoP and Co P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co P NC anode can achieve a current density of 10 mA cm at 1.56 V, comparable even to the noble metal-based Pt/C and RuO /C pair. Furthermore, the CoP NCs are employed as an air cathode in a primary zinc-air battery, exhibiting a high power density of 62 mW cm and good stability.

A highly sensitive and tailorable pressure sensor is designed based on the variation of contact resistance between an Au covered micropillar array and a conductive polymer film. The sensitivity of such pressure sensors can be tuned from 0.03 kPa−1 to 17 kPa−1 at pressures less than 1 kPa, and a limit of detection of 2 Pa has been demonstrated.

The development of rapid, specific, cost-effective, and robust tools in monitoring Hg(2+) levels in both environmental and biological samples is of utmost importance due to the severe mercury toxicity to humans. A number of techniques exist, but the colorimetric assay, which is reviewed herein, is shown to be a possible tool in monitoring the level of mercury. These assays allow transforming target sensing events into color changes, which have applicable potential for in-the-field application through naked-eye detection. Specifically, plasmonic nanoparticle-based colorimetric assay exhibits a much better propensity for identifying various targets in terms of sensitivity, solubility, and stability compared to commonly used organic chromophores. In this review, recent progress in the development of gold nanoparticle-based colorimetric assays for Hg(2+) is summarized, with a particular emphasis on examples of functionalized gold nanoparticle systems with oligonucleotides, oligopeptides, and functional molecules. Besides highlighting the current design principle for plasmonic nanoparticle-based colorimetric probes, the discussions on challenges and the prospect of next-generation probes for in-the-field applications are also presented.

Underwater landslides are a common source of small-scale tsunamis in coastal areas.They have been the object of only a few theoretical and experimental studies. A numerical model is developed to study the coupling of a submarine landslide and the surface waves which it generates. A formulation of the dynamics of the problem is presented, where the landslide is treated as the laminar flow of an incompressible viscous fluid and the water motion is assumed h'rotational. Long-wave approximation is adopted for both water waves and the mudslide. The resulting differential equations are solved by a finite-difference method. We present the numerical results which contrast the behavior of the mud flow under a f'zxed surface, in the presence of one-way coupling (bottom deformations affect the free surface), and with full coupling (surface pressure gradients react on the mud flow). It is found that three main waves are generated by a landslide starting from rest on a gentle uniform slope. The fkst wave is a crest which propagates away from the mudslide site into deeper water; this crest is followed by a trough in the form of a forced wave which propagates with the speed of the mudslide front. The third wave is a relatively small trough which propagates shoreward. Two major parameters dominate the interaction between the slide and the waves it produces: the density of sliding material and the depth of water at the mudslide site. The two-way interactions are significant for the cases of a smaller mud density and shallower waters. For the cases of larger mud density and shallower waters, the two-way interactions are small, but the waves generated are very large. For larger initiation depth of the mudslide, the interactions are weak and the waves generated are small. We also examined the possibility of a resonance between the slide and the waves. Our numerical results indicate that a resonance is not expected in many practical cases. l. INTRODUCTIONUnderwater ground motions can generate surface water waves. A tsunami, a kind of surface wave, is formed in the sea following a large-scale, short-duration disturbance of the water surface. The disturbance is generally produced by two kinds of ground motions. One is the earthquakeinduced rigid ground motion ending with a permanent bottom displacement; the other is a landslide. Many small, but locally destructive, surface waves have resulted from underwater landslides with sufficient displaced volume. This kind of wave, though much more localized than a "true" tsunami, can still produce large run-up heights at the coast, especially when the energy is trapped in a basin (e.g., a fjord) or along the coast. There have been several instances of large water waves which were generated by underwater landslides.A major submarine landslide occured April 27, 1975, in Kitimat INlet, British Columbia, Canada, generating water waves with a height of up to 8.2 m [Murty, 1979]. The volume of the materials involved in the slide was estimated to be approximately 2.6x 107 m 3. The duration of the slide...