Effect of intermolecular distance and contact hollow-type on the transport properties of parallel atomic wires

We use non-equilibrium Green's function combined with density functional theory to investigate the electronic transport properties of two parallel molecular wires made of carbon atomic chains (triynes) capped with thiol. The results show that the transport behaviors clearly depend on the intermolecular distance when the two wires are separated by a relatively small distance. However, with increasing the wire spacing, the transport properties are dramatically affected by the molecule-electrode contact hollow-type and insensitive to the intermolecular distance. A quantum interference mechanism is proposed to interpret the contact hollow-type dependence of transport properties at large intermolecular distance.     

Cross-linked gelatin/nanoparticles composite coating on micro-arc oxidation film for corrosion and drug release

A composite coating which could control drug release and biocorrosion of magnesium alloy stent materials WE42 was prepared. This composite coating was fabricated on the surface of the micro-arc oxidation (MAO) film of the magnesium alloy, WE42, by mixing different degrees of cross-linked gelatin with well-dispersed poly(dl-lactide-co-glycolide) (PLGA) nanoparticles. The PLGA nanoparticles were prepared by emulsion solvent evaporation/extraction technique. Nano ZS laser diffraction particle size analyzer detected that the size of the nanoparticles to be 150-300 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to analyze the morphology of the nanoparticles and the composite coating. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of the composite coating. Drug release was determined by ultraviolet-visible (UV-vis) spectrophotometer. The corrosion resistance of the composite coating was improved by preventing the corrosive ions from diffusing to the MAO films. The drug release rate of paclitaxel (PTX) exhibited a nearly linear sustained-release profile with no significant burst releases.     

Morphological effect of MoS2 nanoparticles on catalytic oxidation and vacuum lubrication

The closed layered MoS₂ nano-balls and the opened layered MoS₂ nano-slices were prepared by decomposing MoS₃ in hydrogen atmosphere. The obtained MoS₂ nanoparticles were respectively used as catalysts for S²⁻ oxidation into SO₄²⁻ and lubricating fillers in polyoxymethylene (POM) plastic. Only basal surface could be found in the closed layered MoS₂ nano-balls, which represented very low catalytic efficiency for S²⁻ oxidation into SO₄²⁻. However, the opened layered MoS₂ nano-slices were of both basal surface and rim-edge surface and showed excellent catalytic properties. Moreover, it was shown that MoS₂ nano-balls could improve the self-lubrication of POM plastic in vacuum. However, MoS₂ nano-slices led to the obvious degradation of POM, implying it is not a proper additive for POM. The high activity of MoS₂ nano-slices for catalyzing S²⁻oxidation and degrading POM was ascribed to their small sizes and partly wedge-like shapes, which led to a considerable increase in the rim sites. The weak catalysis and excellent lubrication of MoS₂ nano-balls were resulted from its closed structure and chemical inertness.     

Facile fabrication of pomponlike microarchitectures of lanthanum molybdate via an ultrasound route

Pomponlike La₂(MoO₄)₃ microstructures assembled with single-crystalline nanoflakes have been facilely fabricated via a surfactant-assisted ultrasound route for the first time. Various synthesis conditions were examined, such as the surfactant concentration, the molecular structure of surfactants, and the pH value. The obtained pomponlike microstructures were characterized by X-ray diffraction (XRD), (field-emission) scanning electron microscopy [(FE)SEM], transmission electron microscopy (TEM), and nitrogen adsorption/desorption isotherms. It has been revealed that a minimum concentration of sodium dodecylsulfate (SDS) was required for the formation of pomponlike La₂(MoO₄)₃ microstructures. When the SDS concentration is above 0.02 mol L⁻¹, the pomponlike microstructures become more perfect, and the size is also increased with the increasing SDS concentration. Under the same sonication, similar pomponlike microstructures were obtained when a cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), was used instead of the anionic surfactant SDS, indicating that the hydrophobic alkyl chains are an important factor for the formation of the pomponlike La₂(MoO₄)₃ microstructures. It is also found that the pomponlike La₂(MoO₄)₃ microstructures can only be obtained within an optimal pH range of 8.0–9.0 under sonication. Based on TEM, Fourier transform infrared spectroscopy (FT-IR) and solubilization experiment, a formation mechanism of pomponlike La₂(MoO₄)₃ microstructures was proposed, in which the collaborative action of surfactants and sonication plays a key role. Furthermore, the porosity of the pomponlike La₂(MoO₄)₃ microstructures were discussed.     

Understanding formation of molecular rotor array on Au(111) surface

The motion of single molecules on surfaces plays an important role in nanoscale engineering and bottom-up construction of complex devices at single molecular scale. In this article, we review the recent progress on single molecular rotors self-assembled on Au(111) surfaces. We focus on the motion of single phthalocyanine molecules on the reconstructed Au(111) surface based on the most recent results obtained by scanning tunneling microscopy (STM). An ordered array of single molecular rotors with large scale is self-assembled on Au(111) surface. Combined with first principle calculations, the mechanism of the surface-supported molecular rotor is investigated. Based on these results, phthalocyanine molecules on Au (111) are a promising candidate system for the development of adaptive molecular device structures.     

Self-organized periodic surface structures on ZnO induced by femtosecond laser

Self-organized periodic surface structures on ZnO have been observed after multiple linearly polarized femtosecond laser pulse irradiation. The observed self-organized structures are attributed to the second harmonics in the sample surface excited by the incident laser. The grating orientation could be adjusted by the laser polarization direction. We also find that fluences play an important role in the formation of self-organized nanostructures.     

Stochastic resonance in a time-delayed asymmetric bistable system with mixed periodic signal

This paper studies the phenomenon of stochastic resonance in an asymmetric bistable system with time-delayed feedback and mixed periodic signal by using the theory of signal-to-noise ratio in the adiabatic limit. A general approximate Fokker--Planck equation and the expression of the signal-to-noise ratio are derived through the small time delay approximation at both fundamental harmonics and mixed harmonics. The effects of the additive noise intensity $Q$, multiplicative noise intensity $D$, static asymmetry $r$ and delay time $\tau$ on the signal-to-noise ratio are discussed. It is found that the higher mixed harmonics and the static asymmetry $r$ can restrain stochastic resonance, and the delay time $\tau $ can enhance stochastic resonance. Moreover, the longer the delay time $\tau $ is, the larger the additive noise intensity $Q$ and the multiplicative noise intensity $D$ are, when the stochastic resonance appears.     

Eu掺杂TbMnO3多晶材料的介电性质

采用固相反应法制备了Tb_0.8Eu_0.2MnO₃多晶材料.对样品的X射线衍射（XRD）分析表明Eu³⁺固溶于TbMnO₃中.测量了样品在低温(100 K ≤T≤ 300 K)和低频下(200 Hz≤f≤100 kHz)的复介电性质.在此温度区间内发现了两个介电弛豫峰.经分析认为低温峰（T≈170 K）起源于局域载流子漂移引起的偶极子极化效应,而高温峰（T≈290 K）则是由离子电导产生的边界和界面层的电容效应引起的.电阻率的测量显示在低温下（T≈230 K）存在明显的导电机制转变.     

准单色噪声驱动的耗散动力系统的信息熵演化

准单色噪声是一类所谓真正有色的噪声.本文对准单色噪声驱动的耗散动力系统的信息熵演化进行研究,文中首先运用线性变换的方法给出了所研究系统的Fokker-Planck方程,然后结合Shannon信息熵定义推导了该系统随时间演化信息熵的精确表达式, 最后分析了系统耗散参数和准单色噪声对系统信息熵的显著影响.