Fano effect of a laterally coupled vertical triple quantum dot system

Using the nonequilibrium Green’s function technique,electron transport through a laterally coupled vertical triple quantum dot is investigated.The conductance as a function of electron energy is numerically calculated.The evolution of the conductance strongly depends on the configuration of dot levels and interdot coupling strengths.     

Optoelectronic characterisation of an individual ZnO nanowire in contact with a micro-grid template

Optoelectronic characterisation of an individual ZnO nanowire in contact with a micro-grid template has been studied.The low-cost micro-grid template made by photolithography is used to fabricate the ohmic contact metal electrodes.The current increases linearly with the bias,indicating good ohmic contacts between the nanowire and the electrodes.The resistivity of the ZnO nanowire is calculated to be 3.8 ·cm.We investigate the photoresponses of an individual ZnO nanowire under different light illumination using light emitting diodes(λ = 505 nm,460 nm,375 nm) as excitation sources in atmosphere.When individual ZnO nanowire is exposured to different light irradiation,we find that it is extremely sensitive to UV illumination;the conductance is much larger upon UV illumination than that in the dark at room temperature.This phenomenon may be related to the surface oxygen molecule adsorbtion,which indicates their potential application to the optoelectronic switching device.     

Constructive approximation of solution for fourth‐order nonlinear boundary value problems

In this paper, we obtain a sequence of approximate solution converging uniformly to the exact solution of a class of fourth‐order nonlinear boundary value problems. Its exact solution is represented in the form of series in the reproducing kernel space. The n‐term approximation u_n(x) is proved to converge to the exact solution u(x). Moreover, the derivatives of u_n(x) are also convergent to the derivatives of u(x). Copyright © 2008 John Wiley & Sons, Ltd.     

The Wigner function and phase properties of superposition of two coherent states with the vacuum state

This paper discusses some statistical properties of the superposition of two coherent states with a vacuum state, such as sub-Poissonian photon statistics and negativity of the Wigner function. Phase probability distribution and phase variance are calculated. Special cases of the constructed superposition states are presented. The results show that depending on the vacuum state coefficient γ and the coherent state coefficient α, it can generate a variety of nonclassical states.     

An efficient computational method for linear fifth-order two-point boundary value problems

In this paper, we present a new algorithm to solve general linear fifth-order boundary value problems (BVPs) in the reproducing kernel space . Representation of the exact solution is given in the reproducing kernel space. Its approximate solution is obtained by truncating the n-term of the exact solution. Some examples are displayed to demonstrate the computational efficiency of the method.     

Spin-dependent Fano effect through parallel-coupled double quantum dots

Based on the nonequilibrium Green' function method, the spin-dependent Fano effect through parallel-coupled double quantum dots has been investigated by taking account of both Rashba spin-orbit interaction and intradot Coulomb interaction. It is shown that the quantum interference through the bonding, antibonding states and through their Coulomb blockade counterparts may result in two Breit-Wigner resonances and two Fano resonances in the conductance spectra. Moreover, the Fano lineshape of the two spin components can be modulated by Rashba spin-orbit interaction when the magnetic flux is switched on.     

以大蓟髓芯为模板制备复合孔生物活性玻璃及其体外成骨性能

以天然植物大蓟髓芯为大孔模板, 以嵌段共聚物为介孔软模板, 制备了孔径为60~100 μm、孔壁为介孔相的高度有序多级复合孔生物活性玻璃. 用扫描电子显微镜(SEM)、粉末X射线衍射仪(XRD)、高分辨率透射电镜(HRTEM)及N2吸附-脱附等测试手段对合成的样品进行了表征. 结果表明, 合成的材料精确地复制了植物模板的形貌, 同时具有较高的比表面积和较大的孔容. 通过体外模拟生理体液测试表明, 这种复合孔生物活性玻璃可诱导羟基磷灰石晶体在其表面形成, 具有良好的体外成骨性能, 因而在骨组织修复方面具有潜在应用前景.     

原位构筑质子化氮化碳/碳化钛光催化制氢肖特基异质结

氢气因其具有高燃烧热、可再生性以及燃烧产物无污染等优势被认为是一种绿色可再生能源,是取代化石燃料的候选能源之一.然而,如何利用自然界中丰富的太阳能和水资源实现光分解水制氢的关键在于开发高效的光催化剂.在尺寸明确、能级带隙匹配的纳米材料间进行完美的界面复合(异质结构筑)是实现高效太阳能-氢能转换的最佳途径.石墨相氮化碳(CN)材料因其电子结构可调和化学性能稳定等特性被光催化界所关注.然而,氮化碳材料较弱的电学性能如电荷传输能力差及电子-空穴对复合率高导致其表现出较低的光催化制氢效率.基于此,我们用盐酸对氮化碳进行质子化处理,使材料表面电荷发生改变,从而实现氮化碳的电子带隙调节和电导率提升.在此基础上,将二维碳化钛原位负载于质子化的氮化碳(PCN)纳米片表面构筑肖特基结.PCN纳米片与碳化钛纳米片间的良好界面接触促进了电荷在材料界面上传输,进而加速了氮化碳材料的电荷分离,实现了氮化碳光催化剂活性的提升.Zeta电位测试结果显示,CN和PCN的表面电位分别为?9.5和27.3 mV,表明质子化处理可以有效改变材料表面电荷,并促其与碳化钛纳米片进行静电组装.该结果进一步得到了扫描电子显微镜(SEM)和原子力显微镜(AFM)的证实.改变表面电荷使氮化碳材料的能带宽度由2.53 eV(CN)减小到2.41 eV(PCN),增强了可见光区吸收.同时,PCN的光电流密度提升了约4倍,电子阻抗和激发态电子的辐射复合都显著降低.将PCN与碳化钛复合制得复合材料(PCN-x,x=10,20,40),实验结果表明5 g的PDN最佳负载碳化钛的量为20 mg(PCN-20).在标准太阳模拟器的可见光区(>420 nm),复合材料PCN-20的光催化水分解产氢量可达2181μmol·g-1,是CN催化剂的约5.5倍,PCN的2.7倍,并且经过5次产氢循环后PCN-20仍具有稳定的氢气释放速率.以上结果表明,氮化碳材料可以通过质子化处理以及与适量的碳化钛复合实现光催化产氢性能的提升,其中碳化钛在体系中起助催化剂的作用.该研究结果可为其他半导体光催化剂的性能优化以及非贵金属助催化剂的研究提供新思路.     

Fabrication of bilayer emulsion by ultrasonic emulsification: Effects of chitosan on the interfacial stability of emulsion

In this study, the stable system of bilayer emulsion was fabricated by ultrasonic emulsification. The effect of chitosan (CS) addition (0.05 %-0.4 %, w/v) at pH 5.0 on the stability of rice bran protein hydrolysate-ferulic acid (RBPH-FA) monolayer emulsion was investigated. It was found that the addition of CS (0.3 %) could form a stable bilayer emulsion. The droplet size was 3.38 μm and the absolute ζ-potential value was 31.52 mV. The bilayer emulsion had better storage stability, oxidation stability and environmental stabilities than the monolayer emulsion. The results of in vitro simulations revealed the bilayer emulsion was able to deliver the β-carotene to the small intestine digestive stage stably and the bioaccessibility was increased from 22.34 % to 61.36 % compared with the monolayer emulsion. The research confirmed that the bilayer emulsion prepared by ultrasonic emulsification can be used for the delivery of hydrophobic functional component β-carotene.