Tungsten trioxide/bismuth vanadate heterojunction is one of the best pairs for solar water splitting, but its photocurrent densities are insufficient. Here we investigate the advantages of using helical nanostructures in photoelectrochemical solar water splitting. A helical tungsten trioxide array is fabricated on a fluorine-doped tin oxide substrate, followed by subsequent coating with bismuth vanadate/catalyst. A maximum photocurrent density of B5.35±0.15 mA cm À 2 is achieved at 1.23 V versus the reversible hydrogen electrode, and related hydrogen and oxygen evolution is also observed from this heterojunction. Theoretical simulations and analyses are performed to verify the advantages of this helical structure. The combination of effective light scattering, improved charge separation and transportation, and an enlarged contact surface area with electrolytes due to the use of the bismuth vanadatedecorated tungsten trioxide helical nanostructures leads to the highest reported photocurrent density to date at 1.23 V versus the reversible hydrogen electrode, to the best of our knowledge.

The edge sites of MoS are catalytically active for the hydrogen evolution reaction (HER), and growing monolayer structures that are edge-rich is desirable. Here, we show the production of large-area highly branched MoS dendrites on amorphous SiO/Si substrates using an atmospheric pressure chemical vapor deposition and explore their use in electrocatalysis. By tailoring the substrate construction, the monolayer MoS evolves from triangular to dendritic morphology because of the change of growth conditions. The rough edges endow dendritic MoS with a fractal dimension down to 1.54. The highly crystalline basal plane and the edge of the dendrites are visualized at atomic resolution using an annular dark field scanning transmission electron microscope. The monolayer dendrites exhibit strong photoluminescence, which is indicative of the direct band gap emission, which is preserved after being transferred. Post-transfer sulfur annealing restores the structural defects and decreases the n-type doping in MoS monolayers. The annealed MoS dendrites show good and highly durable HER performance on the glassy carbon with a large exchange current density of 32 μA cm, demonstrating its viability as an efficient HER catalyst.

We investigated the neuroprotective effect of glucosamine (GlcN) in a rat middle cerebral artery occlusion model. At the highest dose used, intraperitoneal GlcN reduced infarct volume to 14.3% ± 7.4% that of untreated controls and afforded a reduction in motor impairment and neurological deficits. Neuroprotective effects were not reproduced by other amine sugars or acetylated-GlcN, and GlcN suppressed postischemic microglial activation. Moreover, GlcN suppressed lipopolysaccharide (LPS)-induced upregulation of proinflammatory mediators both in vivo and in culture systems using microglial or macrophage cells. The anti-inflammatory effects of GlcN were mainly attributable to its ability to inhibit nuclear factor kappaB (NF-κB) activation. GlcN inhibited LPS-induced nuclear translocation and DNA binding of p65 to both NF-κB consensus sequence and NF-κB binding sequence of inducible nitric oxide synthase promoter. In addition, we found that GlcN strongly repressed p65 transactivation in BV2 cells using Gal4-p65 chimeras system. P65 displayed increased O-GlcNAcylation in response to LPS; this effect was also reversed by GlcN. The LPS-induced increase in p65 O-GlcNAcylation was paralleled by an increase in interaction with O-GlcNAc transferase, which was reversed by GlcN. Finally, our results suggest that GlcN or its derivatives may serve as novel neuroprotective or anti-inflammatory agents.

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A hybrid catalyst -Pt nanocrystals deposited on the surface of MoS2 vertically standing nanoplatelets is synthesized via chemical vapor deposition (CVD) and subsequent thermal annealing (TA) of Pt precursor.The hybrid material shows promising results as an electrocatalyst for the hydrogen evolution reaction (HER). By varying Pt synthesis condition -precursor loading and TA temperature -the deposition sites, size and morphology of Pt nanostructure can be controlled. The size effect of Pt nanoparticle on catalytic activity and sintering resistance is discussed. Results show that higher Pt loading yields better HER performance despite of smaller specific surface area; higher TA temperature delivers larger average particle size of Pt crystals and lower HER activity. Larger average size leads to fast sintering and thus poor durability of the catalyst. Based on the correlation between HER performance and growth behaviors of Pt on MoS2 surfaces, optimization route for a highly active and stable co-catalyst can be established.The optimized Pt-MoS2 catalyst (400 °C, 11 wt%) reported in this study possesses superior overpotential of 9 mV (close to zero), Tafel slope of 44mV/dec and moderate exchange current density of 373 µA/cm 2 ; 2 it exhibits activity degradation of 140 mV @ 20mA/cm 2 after 10,000 cycles. The Tafel slope indicates the combination of Volmer-Heyrovsky steps as HER mechanism in this particular hybrid catalyst system. The outstanding HER activity attributes to highly-dispersed Pt nanoparticles grown on MoS2 basal surfaces, large MoS2 edge density and Pt -S bonding effect induced activity improvement of MoS2 as well as 3D porous network assisted superaerophobic surface.

The breaking of symmetry across an oxide heterostructure causes the electronic orbitals to be reconstructed at the interface into energy states that are different from their bulk counterparts . The detailed nature of the orbital reconstruction critically affects the spatial confinement and the physical properties of the electrons occupying the interfacial orbitals. Using an example of two-dimensional electron liquids forming at LaAlO/SrTiO interfaces with different crystal symmetry, we show that the selective orbital occupation and spatial quantum confinement of electrons can be resolved with subnanometre resolution using inline electron holography. For the standard (001) interface, the charge density map obtained by inline electron holography shows that the two-dimensional electron liquid is confined to the interface with narrow spatial extension (~1.0 ± 0.3 nm in the half width). On the other hand, the two-dimensional electron liquid formed at the (111) interface shows a much broader spatial extension (~3.3 ± 0.3 nm) with the maximum density located ~2.4 nm away from the interface, in excellent agreement with density functional theory calculations.

Doping of two-dimensional materials provides them tunable physical properties and widens their applications. Here, we demonstrate the postgrowth doping strategy in monolayer and bilayer tungsten disulfide (WS 2 ) crystals, which utilizes a metal exchange mechanism, whereby Sn atoms become substitutional dopants in the W sites by energetically favorable replacement. We achieve this using chemical vapor deposition techniques, where high-quality grown WS 2 single crystals are first grown and then subsequently reacted with a SnS precursor. Thermal control of the exchange doping mechanism is revealed, indicating that a sufficiently high enough temperature is required to create the S vacancies that are the initial binding sites for the SnS precursor and metal exchange occurrence. This results in a better control of dopant distribution compared to the tradition all-in-one approach, where dopants are added during the growth phase. The Sn dopants exhibit an n-type doping behavior in the WS 2 layers based on the decreased threshold voltage obtained from transistor device measurements. Annular dark-field scanning transmission electron microscopy shows that in bilayer WS 2 the Sn doping occurs only in the top layer, creating vertical heterostructures with atomic layer doping precision. This postgrowth modification opens up ways to selectively dope one layer at a time and construct mixed stoichiometry vertical heterojunctions in bilayer crystals.