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The two-dimensional hexagonal boron nitride (h-BN) has been used as resistive switching (RS) material for memory due to its insulation, good thermal conductivity and excellent thermal/chemical stability. A typical h-BN based RS memory employs a metal-insulator-metal vertical structure, in which metal ions pass through the h-BN layers to realize the transition from high resistance state to low resistance state. Alternatively, just like the horizontal structure widely used in the traditional MOS capacitor based memory, the performance of in-plane h-BN memory should also be evaluated to determine its potential applications. As consequence, a horizontal structured resistive memory has been designed in this work by forming freestanding h-BN across Ag nanogap, where the two-dimensional h-BN favored in-plane transport of metal ions to emphasize the RS behavior. As a result, the memory devices showed switching slope down to 0.25 mV decâˆ'1, ON/OFF ratio up to 108, SET current down to pA and SET voltage down to 180 mV. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) Co 3 O 4 nanoclusters were fabricated with the assistance of tetrasodium ethylene diamine tetraacetic acid (EDTANa 4 ) through a one-pot wet-chemical reaction, featuring self-limiting assembly of building blocks and controlled regrowth process. The molar ratio of Co 2+ and EDTANa 4 plays a key role in building initial clusters as blocks, and the amount of NaOH effects the regrowth process. A possible formation mechanism for the Co 3 O 4 nanoclusters was proposed based on the characterization results of X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The designed hierarchical Co 3 O 4 nanoclusters exhibit a high specific capacitance of 221 F g −1 at a current density of 2 A g −1 in 2 mol L −1 KOH electrolyte. [ABSTRACT FROM AUTHOR]

Stable phase α-MoO3 nanobelts with preferred orientation were successfully evolved on transforming from metastable phase h-MoO3via an aqueous approach. H+ ions play a key role in the nuclei formation and crystal growth processes. Variation of the Mo : H+ molar ratio led to MoO3 crystals with different polymorphs. Oriented α-MoO3 nanobelts along the [001] direction were achieved under a Mo : H+ ratio of 1 : 9, which is relative to a heterogeneous nucleation process on the surface of metastable phase h-MoO3. The α-MoO3 nanobelts along the [100] direction were obtained under a Mo : H+ ratio of 1 : 10; homogeneous nucleation dominated the synthesis without the presentation of h-MoO3 microrods. The α-MoO3 nanobelts with distinguishing crystalline growth orientations exhibited different photochromic behaviors. [ABSTRACT FROM AUTHOR]

A facile aqueous approach to the synthesis of metastable hexagonal tungsten oxide ( h-WO3) hierarchical nanostructures at low temperature was investigated. The spherelike h-WO3 architectures are constructed from 1D nanorods. Polyvinyl pyrrolidone (PVP) in the reaction system facilitates the quick formation of h-WO3 nuclei of the metastable phase through electrostatic interactions between protonated PVP and tungstate anions, which is in accord with the rule of kinetics favoring the formation of the metastable form. PVP also acts as a soft template for the assembly of WO3 crystallites. Oriented growth of WO3 crystallites along the [001] direction resulted in the nanorod-assembled h-WO3 architectures. The h-WO3-rich samples all exhibited good recycled visible-light photochromic performance. [ABSTRACT FROM AUTHOR]

A simple and reliable high-performance liquid chromatography method with diode array detection (HPLC–DAD) was developed and validated for the simultaneous determination of six bioactive components, rutaevine, limonin, evodiamine, rutaecarpine, N-formyldihydrorutaecarpine and dihydroevocarpine, in the traditional Chinese medicine Evodiae Fructus (Wuzhuyu in Chinese). HPLC separation was conducted on an Agilent Eclipse C18 column (4.6 × 150 mm, 5 µm) at 35°C with a mixture of mobile phase A [tetrahydrofuran–0.02% phosphoric acid (16 : 35)] and mobile phase B (acetonitrile) (gradient elution as follows: 0 min, 22% B; 23 min, 22% B; 24 min, 75% B) at a flow rate of 1 mL/min, and the DAD detection wavelength was set at 220 nm. A linear relationship within the range of investigated concentrations was observed for the six compounds, with correlation coefficients greater than 0.999. The average recovery yields of the six compounds ranged from 98.39 to 104.96%. The HPLC–DAD method was validated by its repeatability [relative standard deviation (RSD) < 2.0%] and intra-day and inter-day precision (RSD < 2.0%). The method was successfully applied to the simultaneous determination of the six previously mentioned components in Evodiae Fructus. It is the first report of a simultaneous qualitative and quantitative analysis for three classes of bioactive components in Wuzhuyu, including the indolequinazoline alkaloids, quinolone alkaloid and limonoids. Based on these results, it is suggested, for possible future revision of the Chinese Pharmacopoeia, that the total contents of evodiamine and rutaecarpine are not less than 0.15% and the total contents of rutaevine and limonin are not less than 0.50%. [ABSTRACT FROM PUBLISHER]

Urchin-like tungsten oxide hydrate (WO3 ·H2O) hollow spheres were successfully synthesized via a self-sacrifice template method at low temperature. The effects of reaction parameters on the preparation were studied in solution. The growth mechanism was also proposed on the basis of experimental results. In addition, the acid amount and temperature have important effects on size control of the as-obtained samples. The achieved nanoarchitectures have typical diameters of 4-6 μm with nanoflakes of several nanometers at surface. Crystal structure, morphology, and composition of final nanostructures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Degradation experiments of organic contaminant were also performed on samples of hollow spheres and walnut-like structures under visible-light illumination. Hollow sphere sample exhibited better photocatalytic capability than walnut-like sample. Possible mechanism was studied for WO3 ·H2O assisted photocatalytic degradation of organic contaminant under visible light. [ABSTRACT FROM AUTHOR]