Rhenium disulfide (ReS2) and diselenide (ReSe2), the group 7 transition metal dichalcogenides (TMDs), are known to have a layered atomic structure showing an in-plane motif of diamond-shaped-chains (DS-chains) arranged in parallel. Using a combination of transmission electron microscopy and transport measurements, we demonstrate here the direct correlation of electron transport anisotropy in single-layered ReS2 with the atomic orientation of the DS-chains, as also supported by our density functional theory calculations. We further show that the direction of conducting channels in ReS2 and ReSe2 can be controlled by electron beam irradiation at elevated temperatures and follows the strain induced to the sample. Furthermore, high chalcogen deficiency can induce a structural transformation to a nonstoichiometric phase, which is again strongly direction-dependent. This tunable in-plane transport behavior opens up great avenues for creating nanoelectronic circuits in 2D materials.

Whlte spot syndrome baculovirus (WSBV) has been found across ddferent shrimp species and in different Asian countries. The detection of WSBV in shrimp with white spot syndrome has already been achieved by means of l-step polymerase chain reaction (PCR). In an attempt to establish a more sensitive assay, we evaluated the effect of 2-step amplification with nested primers on the sensitivity of WSBV diagnostic PCR. The sensitivity of the 2-step amplification was 10" to 10"imes higher than that of l-step amplification. Using both techniques, we successfully detected WSBV DNA in cultured and captured shrimp, crabs and other arthropods. Cultured Penaeus monodon (black tiger shrimp), P. japonicus (kuruma shrimp), P penicjllatus (red tail shrimp), and Metapenaeus ensis (sand shrimp) displaying white spot syndrome were collected from farms at different localities. One-step amplification of the DNA extracted from these shrimps consistently yielded an expected 1447 bp PCR product. Some of the tested specimens of cultured Scylla serrata (mud crab) that exhibited white spot syndrome were positive in l-step WSBV diagnostic PCR, while others were positive only in 2-step WSBV diagnostic PCR. Use of the 2-step amplification protocol also detected a WSBV-specific DNA fragment in Macrobrachium rosenbergii (the giant freshwater prawn) exhibiting white spot syndrome. We also confirmed that WSBV exists in wild-caught shrimp (P monodon, f! japonicus, P semisulcatus and P penicillatus) and crabs (Charybdisferiatus. Portunuspelagicus and P. sanguinolentus) collected from the natural environment in coastal waters around southern Taiwan. Detection of WSBV in non-cultured arthropods collected from WSBV-affected shrimp farms revealed that copepods, the pest crab Hehce tndens, small pest Palaemonidae prawn and the larvae of an Ephydridae insect were reservoir hosts of WSBV. The relatedness between WSBV and Thailand's systemc ectodermal and mesodermal baculovirus (SEMBV) is d~scussed in this paper.

Atomically thin rhenium disulphide (ReS2) is a member of the transition metal dichalcogenide family of materials. This two-dimensional semiconductor is characterized by weak interlayer coupling and a distorted 1T structure, which leads to anisotropy in electrical and optical properties. Here we report on the electrical transport study of mono- and multilayer ReS2 with polymer electrolyte gating. We find that the conductivity of monolayer ReS2 is completely suppressed at high carrier densities, an unusual feature unique to monolayers, making ReS2 the first example of such a material. Using dual-gated devices, we can distinguish the gate-induced doping from the electrostatic disorder induced by the polymer electrolyte itself. Theoretical calculations and a transport model indicate that the observed conductivity suppression can be explained by a combination of a narrow conduction band and Anderson localization due to electrolyte-induced disorder.

1 of 6) 1600814and optical absorption behaviors of GeS nanosheets have been studied and proposed for energy applications, [16,17] however, the light-emitting property of a thin multilayer GeS was not yet explored.Herein, in-plane optical anisotropy of band-edge emission of a multilayer GeS stripe (t ≈ 40 nm) is characterized by using polarized micro-photoluminescence (µPL) measurement with polarization angles ranging from 0 to 90° with respect to the multilayer's longest crystal edge (b axis). Light emission from multilayer GeS is completely forbidden at θ = 0° (E||b), and fully allowed (intense light) at θ = 90° (E||a), which obeys a dichroic Malus law [18] for the emission peak at 1.622 eV. Multilayer GeS behaves like a dichroic light emitter with linear polarization along the multilayer's a axis. To understand the band-edge characteristic of the GeS multilayer, polarized thermoreflectance (PTR) measurement by using microscope white-light guiding was also implemented. The selection rule of the PTR spectra also reveals that the lower band-edge transition E A = 1.622 eV is only allowed with E||a polarization while another higher energy transition, E B = 1.732 eV, appears merely along the E||b polarization in the multilayer. In-plane anisotropy of the c plane GeS multilayer occurs with linear polarization along a and b axes. The energy position of the E A transition matches well with the main band-edge emission observed by µPL, while the E B transition may probably originate from valence-band splitting (dominated by the S p orbital) of the multilayer GeS. The structural and optical anisotropy of the multilayer GeS is discussed here.Layered single crystals of IV-VI GeS with different areas, sizes, and thicknesses were grown by using the chemical vapor transport (CVT) method [19] with iodine as the transport agent. The crystals were prepared from their elements (Ge: 99.999% pure and S: 99.999%) by reaction at 600 °C for two days in evacuated quartz ampoules. Sulfur was added in 1 mol% excess with respect to the stoichiometric mixture of the constituent elements. About 10 g of the elements, together with an appropriate amount of transport agent (I 2 about 10 mg cm −3 ), were introduced into a quartz ampoule (22 mm OD, 17 mm ID, 20 cm length), which was then cooled with liquid nitrogen, evacuated to 10 −6 Torr and sealed. The mixture was slowly heated to 600 °C and maintained at this temperature for two days. The temperature was then altered from 600 °C (heating zone) → 520 °C (growth zone) with a gradient of -4 °C cm −1 for crystal growth. The reaction was left 240 h to produce large single crystals. The as-grown GeS crystals are dark red and have a shiny surface with an area of up to 5 mm 2 and thickness of up to 100 µm. The crystals are mostly like ribbon or stripe-shape layered crystals (see Figure S1 in the Supporting Information). The powder and single-crystal X-ray diffraction (XRD) results of GeS shown in Figure S1 reveal an orthorhombic phase. The lattice constants are a = 4.36 Å, b = 3.67 Å, and c = 10.53 Å,

We have measured the temperature dependence of the spectral features in the vicinity of direct band-edge excitonic transitions of single crystals from 25 to 300 K using piezoreflectance (PzR). From a detailed lineshape fit of the PzR spectra, the energies and broadening parameters of the A and B excitons have been determined accurately. The origin of these excitonic transitions is discussed. The transition energies and their splittings vary smoothly with the tungsten composition x, indicating that the natures of the direct band edges are similar for the compounds. In addition, the parameters that describe the temperature variation of the energies and broadening function of the excitonic transitions are evaluated and discussed.