The surface plays an exceptionally important role in nanoscale materials, exerting a strong influence on their properties. Consequently, even a very thin coating can greatly improve optoelectronic properties of nanostructures by modifying the light absorption and spatial distribution of charge carriers. To use these advantages, 1D/1D heterostructures of ZnO/WS 2 core/shell nanowires with a-few-layers thick WS 2 shell were fabricated. These heterostructures were thoroughly characterized by scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. Then, a single-nanowire photoresistive device was assembled by mechanically positioning ZnO/WS 2 core/shell nanowires onto gold electrodes

Core–shell nanowires are an interesting and perspective class of radially heterostructured nanomaterials where epitaxial growth of the shell can be realized even at noticeable core–shell lattice mismatch. In this study epitaxial hexagonally shaped shell consisting of WS2 nanolayers was grown on {11̅00} facets of prismatic wurtzite-structured [0001]-oriented ZnO nanowires for the first time. A synthesis was performed by annealing in a sulfur atmosphere of ZnO/WO3 core–shell structures, produced by reactive dc magnetron sputtering of an amorphous a-WO3 layer on top of ZnO nanowire array. The morphology and phase composition of synthesized ZnO/WS2 core–shell nanowires were confirmed by scanning and transmission electron microscopy (SEM and TEM), micro-Raman, and photoluminescence spectroscopy. Epitaxial growth of WS2(0001) layer(s) on {11̅00} facets of ZnO nanowire is unexpected due to incompatibility of their symmetry and structure parameters. To relax the interfacial incoherence, we propose a model of ZnO/WS2 interface containing WS2 bridging groups inside and use first-principles simulations to support its feasibility.

The growth direction of nanowires (NWs) can change during synthesis as a result of stochastic processes or modulation of certain growth conditions. This phenomenon is known as kinking. Although deviations from a uniform vertical growth are typically considered to be undesirable, kinking opens a route for additional tweaking of the characteristics and functionalities of NWs in a controllable manner, thus extending the range of potential applications. In the present Review, we give an insight into the kinking mechanisms and summarize the most crucial factors that can lead to kinking of NWs during synthesis. Additionally, the properties and applications of kinked NWs are discussed.

Hybrid nanostructures composed of layered materials have recently attracted a lot of attention due to their promising electronic and catalytic properties. In this study, we describe a novel synthesis strategy of ZnO/ZnS/MoS 2 core-shell nanowire growth using a three-step route. First, ZnO nanowire array was grown on a silicon wafer. Second, the sample was immersed in ammonium molybdate solution and dried. At the third step, the sample was annealed in a sulfur atmosphere at 700 ºC. Two solid state chemical reactions occur simultaneously during the annealing and result in a formation of ZnS and MoS 2 phases. Produced ZnO/ZnS/MoS 2 coreshell nanowires were characterized by scanning and transmission electron microscopy, whereas their chemical composition was confirmed by selected area electron diffraction and micro-Raman spectroscopy.

Thin films of rhenium trioxide (ReO 3) were produced by reactive DC magnetron sputtering from metallic rhenium target followed by annealing in the air in the range of temperatures from 200C to 350C. Nanocrystalline singlephase ReO 3 films were obtained upon annealing at about 250C. The thin films appear bright red in reflected light and blue-green in transmitted light, thus showing an optical transparency window in the spectral range of 475-525 nm. The film exhibits high conductivity, evidenced by macro-and nano-scale conductivity measurements. The longrange and local atomic structures of the films were studied in detail by structural methods as X-ray diffraction and X-ray absorption spectroscopy. The oxidation state (6+) of rhenium was confirmed by X-ray photoemission and Xray absorption spectroscopies. The nanocrystalline morphology of the annealed films was evidenced by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The obtained results allowed us to propose the mechanism of rhenium oxide conversion from the initially amorphous ReO x phase to cubic ReO 3. 1. Introduction Rhenium oxides are known to exist in the three main phases ReO 2 , ReO 3 and Re 2 O 7 , corresponding to the oxidation states of Re 4+ , Re 6+ and Re 7+ , respectively. ReO 2 is dark blue or black solid and has a monoclinic phase α-ReO 2 below 300°C [1]. When heated above 300°C, it irreversibly turns into the orthorhombic phase β-ReO 2 , which is stable in vacuum to 850-1000°C but oxidizes in the air to Re 2 O 7 above 400°C. Both phases of ReO 2 have metallic conductivity [2]. Crystalline Re 2 O 7 is an inorganic polymer and it is electrically insulating material [2]. It consists of ReO 6 octahedra and ReO 4 tetrahedra. In each octahedral ReO 6 group, three of the Re-O bonds are longer than the others, and if weak bonds are broken (e.g., upon heating) volatile molecules of Re 2 O 7 are produced. Re 2 O 7 sublimes at temperatures above 360°C. Besides, Re 2 O 7 is highly hygroscopic, decomposing into perrhenic acid (HReO 4) when exposed to moisture [3]. ReO 3 is a red solid with a metallic luster. Its cubic crystalline structure is of perovskite-type and is formed by a network of regular ReO 6 octahedra, which have common vertices in three

A comparative study of heterostructured CuO/CuWO4 core/shell nanowires and doublelayer thin films was performed through X-ray diffraction, confocal micro-Raman spectroscopy and electron (SEM and TEM) microscopies. The heterostructures were produced using a two-step process, starting from a deposition of amorphous WO3 layer on top of CuO nanowires and thin films by reactive DC magnetron sputtering and followed by annealing at 650°C in air. The second step induced a solid-state reaction between CuO and WO3 oxides through a thermal diffusion process, revealed by SEM-EDX analysis. Morphology evolution of core/shell nanowires and double-layer thin films upon heating was studied by electron (SEM and TEM) microscopies. A formation of CuWO4 phase was confirmed by X-ray diffraction and confocal micro-Raman spectroscopy.

Transition metal dichalcogenide (TMD) MoS2 and WS2 monolayers (MLs) deposited atop of crystalline zinc oxide (ZnO) and graphene-like ZnO (g-ZnO) substrates have been investigated by means of density functional theory (DFT) using PBE and GLLBSC exchange-correlation functionals. In this work, the electronic structure and optical properties of studied hybrid nanomaterials are described in view of the influence of ZnO substrates thickness on the MoS2@ZnO and WS2@ZnO two-dimensional (2D) nanocomposites. The thicker ZnO substrate not only triggers the decrease of the imaginary part of dielectric function relatively to more thinner g-ZnO but also results in the less accumulated charge density in the vicinity of the Mo and W atoms at the conduction band minimum. Based on the results of our calculations, we predict that MoS2 and WS2 monolayers placed at g-ZnO substrate yield essential enhancement of the photoabsorption in the visible region of solar spectra and, thus, can be used as a promising catalyst for photo-driven water splitting applications.

Layered 2D van der Waals (vdW) materials such as graphene and transition metal dichalcogenides have recently gained a great deal of scientific attention due to their unique properties and prospective applications in various fields such as electronics and optoelectronics, sensors and energy. As a direct bandgap semiconductor in both bulk and monolayer forms, ReS2 stands out for its unique distorted octahedral structure that results in distinctive anisotropic physical properties; however, only a few scalable synthesis methods for few-layer ReS2 have been proposed thus far. Here, the growth of high-quality few-layer ReS2 is demonstrated via sulfurization of a pre-deposited rhenium oxide coating on different semiconductor material nanowires (GaN, ZnS, ZnO). As-produced core-shell heterostructures were characterized by X-ray diffraction, scanning and transmission electron microscopy, micro-Raman spectroscopy and X-ray absorption spectroscopy. Experimental characterizations were supported by total energy calculations of the electronic structure of ReS2 nanosheets and GaN, ZnS, and ZnO substrates. Our results demonstrate the potential of using nanowires as a template for the growth of layered vdW materials to create novel core-shell heterostructures for energy applications involving photocatalytic and electrocatalytic hydrogen evolution.