Lattice structure and symmetry of two-dimensional (2D) layered materials are of key importance to their fundamental mechanical, thermal, electronic and optical properties. Raman spectroscopy, as a convenient and nondestructive tool, however has its limitations on identifying all symmetry allowing Raman modes and determining the corresponding crystal structure of 2D layered materials with high symmetry like graphene and MoS 2 . Due to lower structural symmetry and extraordinary weak interlayer coupling of ReS 2 , we successfully identified all 18 first-order Raman active modes for bulk and monolayer ReS 2 . Without van der Waals (vdW) correction, our local density approximation (LDA) calculations successfully reproduce all the Raman modes.Our calculations also suggest no surface reconstruction effect and the absence of low frequency rigid-layer Raman modes below 100 cm -1 . Combining with Raman and LDA thus provides a general approach for studying the vibrational and structural properties of 2D layered materials with lower symmetry.3

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Photocatalytic hydrogen evolution from water has triggered an intensive search for metal-free semiconducting photocatalysts. However, traditional semiconducting materials suffer from limited hydrogen evolution efficiency owing to low intrinsic electron transfer, rapid recombination of photogenerated carriers, and lack of artificial microstructure. Herein, we report a metal-free half-metallic carbon nitride for highly efficient photocatalytic hydrogen evolution. The introduced half-metallic features not only effectively facilitate carrier transfer but also provide more active sites for hydrogen evolution reaction. The nanosheets incorporated into a micro grid mode resonance structure via in situ pyrolysis of ionic liquid, which show further enhanced photoelectronic coupling and entire solar energy exploitation, boosts the hydrogen evolution rate reach up to 1009 μmol g−1 h−1. Our findings propose a strategy for micro-structural regulations of half-metallic carbon nitride material, and meanwhile the fundamentals provide inspirations for the steering of electron transfer and solar energy absorption in electrocatalysis, photoelectrocatalysis, and photovoltaic cells.

In the paper, we mainly study the existence and uniqueness of global weak solutions for the Novikov equation. We first recall some results and definitions on strong solutions and weak solutions for the equation. Then, we show that the equation has smooth solutions which exist globally in time, provided the initial data satisfy certain sign conditions. Finally we prove the existence and uniqueness of global weak solutions to the equation with the initial data satisfying certain sign conditions.

Using CMOS-compatible Pd catalysts, we demonstrated the formation of high-mobility ⟨111⟩-oriented GaSb nanowires (NWs) via vapor-solid-solid (VSS) growth by surfactant-assisted chemical vapor deposition through a complementary experimental and theoretical approach. In contrast to NWs formed by the conventional vapor-liquid-solid (VLS) mechanism, cylindrical-shaped PdGa catalytic seeds were present in our Pd-catalyzed VSS-NWs. As solid catalysts, stoichiometric PdGa was found to have the lowest crystal surface energy and thus giving rise to a minimal surface diffusion as well as an optimal in-plane interface orientation at the seed/NW interface for efficient epitaxial NW nucleation. These VSS characteristics led to the growth of slender NWs with diameters down to 26.9 ± 3.5 nm. Over 95% high crystalline quality NWs were grown in ⟨111⟩ orientation for a wide diameter range of between 10 and 70 nm. Back-gated field-effect transistors (FETs) fabricated using the Pd-catalyzed GaSb NWs exhibit a superior peak hole mobility of ∼330 cm V s, close to the mobility limit for a NW channel diameter of ∼30 nm with a free carrier concentration of ∼10 cm. This suggests that the NWs have excellent homogeneity in phase purity, growth orientation, surface morphology and electrical characteristics. Contact printing process was also used to fabricate large-scale assembly of Pd-catalyzed GaSb NW parallel arrays, confirming the potential constructions and applications of these high-performance electronic devices.

The magnetic and electrical properties of crystalline Mn0.05Si0.95 films prepared by post-thermal treatment of the as-deposited amorphous Si-Mn (95at.%−5at.%) have been investigated. Both the temperature dependence and field dependence of magnetization were measured using superconducting quantum interference devices, and it has been indicated that the film materials are ferromagnetic with Curie temperature over 400K. X-ray diffraction analysis revealed full crystallization of the films and the incorporation of Mn into the host crystalline Si lattice. Behavior of thermally activated conduction processes of the films has been evinced by electrical property measurement for the films.

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In this paper, we mainly study the Cauchy problem of the Novikov equation. We first establish the local well-posedness and give the precise blow-up scenario for the equation. Then we show that the equation has smooth solutions which exist globally in time. Finally we prove that peakon solutions to the equation are global weak solutions.