We report the creation of an unusual simple cubic -phase W͑100͒ nanorods with a pyramidal tip having four ͑110͒ facets using an oblique-angle sputter deposition technique with substrate rotation ͑also known as glancing-angle deposition͒. During the oblique-angle deposition, both -phase W͑100͒ and ␣-phase W͑110͒ islands exist at the initial stages of growth. The -phase W͑100͒ islands grow taller due to the lower adatom mobility on these islands. The taller islands survive in the competition and form isolated nanorods in the later stages of growth. This is in contrast to the sputter deposition at normal incidence, where only the thermodynamically stable bcc ␣-phase W͑110͒ polycrystalline films were formed when the film grows to a certain thickness.
Electron field emission is a quantum tunneling phenomenon whereby electrons are emitted from a solid surface due to a strong electric field. Graphene and its derivatives are expected to be efficient field emitters due to their unique geometry and electrical properties. So far, electron field emission has only been achieved from the edges of graphene and graphene oxide sheets. We have supported graphene oxide sheets on nickel nanotip arrays to produce a high density of sharp protrusions within the sheets and then applied electric fields perpendicular to the sheets. Highly efficient and stable field emission with low turn-on fields was observed for these graphene oxide sheets, because the protrusions appear to locally enhance the electric field and dramatically increase field emission. Our simple and robust approach provides prospects for the development of practical electron sources and advanced devices based on graphene and graphene oxide field emitters.
In our effort to develop effective neuroprotectants as potential treatments for Alzheimer's disease (AD), hybrid compounds of curcumin and melatonin, two natural products that have been extensively studied in various AD models, were designed, synthesized, and biologically characterized. A lead hybrid compound (7) was discovered to show significant neuroprotection with nanomolar potency (EC50 = 27.60 ± 9.4 nM) in MC65 cells, a cellular AD model. Multiple in vitro assay results established that 7 exhibited moderate inhibitory effects on the production of amyloid-β oligomers (AβOs) in MC65 cells, but not on the aggregation of Aβ species. It also exhibited significant antioxidative properties. Further mechanistic studies demonstrated that 7's antioxidant effects correlate well with its neuroprotective potency for MC65 cells, and these effects might be due to its interference with the interactions of AβOs within the mitochondria of MC65 cells. Furthermore, 7 was confirmed to cross the blood-brain barrier (BBB) and deliver a sufficient amount to brain tissue after oral administration. Collectively, these results strongly support the hybridization approach as an efficient strategy to help identify novel scaffolds with a desired pharmacology, and strongly encourage further optimization of 7 to develop more potent neuroprotectants for AD.
We report the melting of nanorod arrays of copper at temperatures much lower than its bulk melting point ͑1083°C͒. The Cu nanorods were produced by an oblique angle sputter deposition technique through a physical self-assembly mechanism due to the shadowing effect. The as-deposited nanorods were ϳ2300 nm in length, ϳ100 nm in diameter, and separated from each other with gaps varying between ϳ10 and ϳ30 nm. The melting process was investigated through the analysis of scanning electron microscopy, transmission electron microscopy, and x-ray diffraction measurements. Start of premelting ͑or surface melting͒ has been observed to occur at annealing temperature ϳ400°C under vacuum ͑10 −6 Torr͒. As the temperature was raised the arrays of Cu nanorods started to coalesce and formed a dense continuous film with a ͑111͒ texture at ϳ550°C. The results of this work may be useful for low temperature soldering applications.
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