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Elaborate design of highly active catalysts from earth-abundant elements is important for the development of water-splitting devices. We have synthesized {2̅ 1 1} high index-faceted Ni12P5 nanoplates and Ni12P5 spherical nanoparticles (SNPs) by the one-step solvothermal method. The Ni12P5 nanoplates show enhanced hydrogen evolution reaction activity with a lower overpotential of −128 mV and a smaller Tafel slope of 60.6 mV dec−1 compared to Ni12P5 SNPs. Stability tests reveal exceptional durability of the catalyst. This study offers an attractive catalytic material for large-scale hydrogen production technology. [ABSTRACT FROM AUTHOR]

Single-crystalline hollow CoO nanooctahedra were successfully synthesized by the combination of self-gas-leaching and Ostwald ripening processes through a template-free route. Elaborate microscopy evidence discloses that hollow CoO nanocrystals (NCs) evolve from the channeled CoO NCs, which is an essential intermediate state to construct the hollow structure. Electrochemical measurements indicate that hollow CoO NCs exhibit three times higher specific capacitance than the solid CoO and show excellent cycling stability with the specific capacitance retaining more than 97% after 4500 cycles at a current density of 2 A g−1. Meanwhile, as a catalyst for oxygen evolution reaction and hydrogen production from hydrolysis of sodium borohydride, the hollow and channeled CoO NCs exhibit much better performances than their solid counterparts. The hollow CoO NCs afford a current density of 10 mA cm−2 at a small overpotential of merely 0.375 V and a small Tafel slope of 55 mV decade−1, and they also possess more steady catalytic activity than the channeled CoO. [ABSTRACT FROM AUTHOR]

A 2D wave-like layered framework based on benzotriazole-5-carboxylic acid (H2btca), 2,2′-bipy and zinc ions – [Zn(btca)(2,2′-bipy)]n (1) – has been resoundingly designed and synthesized by a solvothermal method. By changing the solvent from DMF to DMA, a 3D porous framework – [Zn2(btca)2(bpy)(H2O)]n·n(DMA) (2) – was obtained. Complexes 1 and 2 have been determined by single-crystal X-ray diffraction analysis and further characterized by powder X-ray diffraction (PXRD), elemental analysis, IR spectroscopy, and thermogravimetric (TG) analysis. Complex 1 shows an AA packing 2D layered structure and complex 2 displays a 3D open honeycomb framework with a (3,4)-connected 2-nodal fsc topology. Moreover, gas adsorption of 2a (the activated form of 2) and the luminescence properties of 1, 2 and 2a have also been investigated intensively. [ABSTRACT FROM AUTHOR]

Hexagonal Ni0.25Co0.75(OH)2 nanoplates with rough and smooth surfaces have been synthesized with various amounts of CTAB by a mild wet chemical approach. The diameters of these two nanoplates are estimated to be ~150 nm and their thicknesses are ~30 nm. The electrochemical properties of the hexagonal nanoplates have also been investigated by using a three-electrode system under alkaline conditions. The scobinate Ni0.25Co0.75(OH)2 nanoplates show enhanced supercapacitor capacity compared with the smooth samples. For scobinate nanoplates, the specific capacitance is 306 F g−1 at a current density of 0.5 A g−1 and remains 90% as the current density increases 16 times. At a current density of 3 A g−1, the specific capacitance still remains 98% after 7000 cycles. [ABSTRACT FROM AUTHOR]

Au dendritic nanostructures with sharp tips have been successfully fabricated on a large scale by reducing potassium tetrachloroaurate (KAuCl4) with hydrofluoric acid on a Si wafer locally processed using a focused ion beam (FIB) technique. Surface enhanced Raman scattering (SERS) with Rhodamine B (RhB) molecules on a nanostructured substrate is greatly enhanced, originating from “hot-spots” located at the nanogaps between adjacent branches on dendritic nanostructures. Furthermore, Au dendritic nanostructures as recyclable SERS substrates exhibit an ultrasensitive response to the pico-scale concentration of probe molecules. This work shows that greatly enhanced SERS substrates with a high degree of reliability and reproducibility can be fabricated at a relatively low cost, which could help SERS to realize its full potential as a very sensitive tool for trace analysis. [ABSTRACT FROM AUTHOR]

Nickel ferrite (NiFe2O4) nanomaterials with different morphologies, including nano-spheres (10–25 nm in diameter), nano-rods (50–60 nm in diameter and ~1 μm in length), and nano-octahedrons (side length ~150 nm), have been synthesized by a single mild hydrothermal method at 160 °C without any surfactant. The crystal structures have been investigated by TEM, HRTEM, and studied by simulations using the program Materials Studio. The variations in the morphology, as well as the preferential crystal growth directions, depend only on the pH value of the reaction solution. A phase formation mechanism is thus proposed. Magnetization measurements at T = 300 K indicate that the NiFe2O4 nano-spheres of 10–25 nm diameter are superparamagnetic with non-saturating magnetization at H = 7 kOe. The saturation magnetization, MS, of the nanorods is 40 emu g−1, less than the bulk value, MS = 46.7 to 55 emu g−1. The coercivity is HC = 40 Oe, reduced from the bulk value of 100 Oe. On the other hand, the nano-octahedrons have a saturation magnetization of MS = 50 emu g−1, the same as the bulk value. However the coercivity, HC = 50 Oe is also much reduced from the bulk value. [ABSTRACT FROM AUTHOR]

Highly efficient photoluminescence (PL) emission is obtained from flower-like silicon oxide (SiOx)–Au nanostructures that were synthesized by annealing silicon substrates coated with Au thin film under Ar–H2 atmosphere at 1100 °C via the vapour–liquid–solid process. The morphologies and structures of the SiOx–Au nanoflowers were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and helium ion microscopy. The results revealed that the silicon oxide–Au nanoflowers were amorphous with an Au nanoparticle core at the centre. As compared to simple SiOx nanowires, the SiOx–Au nanoflowers show a 5-fold enhancement in intensity of room temperature photoluminescence, which can be attributed to the unique nanostructures, the strong coupling between the photoluminescence emission of the SiOx nanoflowers and the local surface plasmon resonance of the Au nanoparticles. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of 5-hydroxyisophthalic acid (hip) and different N-containing auxiliary ligands with transition metal salts provided four new metal–organic coordination polymers (MOPs), namely, {Zn(hip)(2,2′-bipy)·2H2O}n (1), {[Ni(hip)(4,4′-bipy)(H2O)]·DMF·2H2O}n (2), {Zn(hip)(tib)·2H2O}n (3), {[Zn2(hip)2]·5H2O}n (4), (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, DMF = N,N′-dimethylformamide, tib = 1,3,5-tris(1-imidazolyl)benzene). All of the complexes have been structurally characterized by single-crystal X-ray diffraction analyses, infrared spectra (IR), elemental analyses and powder X-ray diffraction (PXRD). Single crystal X-ray diffraction analysis reveals that complex 1 exhibits a one-dimensional zig-zag chain, in which strong π…π interactions are found between neighbouring 2,2′-bipy molecules. Complex 2 has a 2D double-layer square framework, exhibiting AA stacking sequence, and the topology of each layer is typical 2D (44)-sql. In complex 3, both hip and tripodal ligand tib act as bidentate bridging ligand and extend the tetragonal pyramid Zn(ii) centers to a 2D wavy framework, exhibiting an AB stacking sequence. The 2D layer structures in 2 and 3 are different from each other. In complex 4, the oxygen atoms of the hydroxy group of hip participate in constructing a framework, which results to the 3D net framework with 1D channel. The structural and topological differences of the four MOPs indicate that the auxiliary ligand play important roles in the formation of final structures. Furthermore, the thermal stability and photoluminescence properties of complexes 1–4 were investigated. [ABSTRACT FROM AUTHOR]