Preparation and optical properties of HgWO<Subscript>4</Subscript> nanorods by hydrothermal method coupled with ultrasonic technique

For the first time, a newly luminescent nanomaterial, monoclinic wolframite-type HgWO₄ nanorods (diameter: ∼200 nm; length: ~2000 nm) are prepared by hydrothermal method together with ultrasonic technique. Fluorescent (FL) and UV–Vis results both show that for HgWO₄, ultrasonic irradiation procedure will change its optical behaviors greatly. When the crystals become into nanorods, the fluorescent emitting peaks (365 and 495 nm) shift to central region, and finally form a wider one at 435 nm. Similar results of UV–visible absorption peaks are observed for these two products. FTIR spectra further characterize their structure. All above unique optical performances might result from both small sizes caused by ultrasonic irradiation procedure and involvement of incompact d¹⁰ electrons. Moreover, possible synthesis mechanisms of HgWO₄ nanorods are also investigated.     

Stretch-induced hairpin-coil transitions in designed polynucleotide chains

The structural property of a poly( dG-dC) or poly( dA-dT) nucleotide is investigated. At low force and room temperatures, the polymer takes on compact hairpin structures. An abrupt transition from hairpin to random coil occurs at certain critical forces, its high cooperativity is related to the unfavorable formation of hairpin and other kinds of looped structures. It is hence necessary to consider the enthalpic effects of single-stranded loops in realistic models of RNA folding. A possible new way to obtain the statistical weights of elementary nucleotide arrangements is by single-macromolecular mechanical measurements on specifically designed polynucleotides.     

Synthesis and structure of ytterbium (III) complex containing tetrachlorophthalate dianions

A novel tetrachlorophthalato-Yb(III) complex [Yb(tcph)(H₂O)₇]Htcph·H₂tcph·H₂O (1) (H₂tcph=tetrachlorophthalic acid) has been synthesized and characterized by the single crystal X-ray diffraction analysis. Colorless crystals of 1 crystallize in the triclinic space group P-1, with a=6.8504(5) ?, b=16.1921(12) ?, c=19.0123(14) ? and α=67.4470(10)°, β=86.5290(10)°, γ=81.6480(10)°, V=2.113 g/cm³ and Z=2. Unique reflections with I > 2σ(I) on refinement afford values of R ₁=0.0219 and wR ₂=0.0565.     

Practical Entanglement Concentration for Entangled Coherent States

Entangled coherent state (ECS) is quite important in current quantum communication and quantum computation. In this paper, we discuss two practical entanglement concentration protocols (ECPs) to recover the maximally ECSs from the partially ECSs. In the first ECP, the parties do not need to know the initial coefficients of the partially ECSs. In the second ECP, they should know the initial coefficients. Both protocols are based on the linear optics which make them feasible in current experiment. Especially, in the second ECP, they only require one pair of initial partially ECSs, which makes this ECP optimal. Both ECPs may be useful in current quantum information processing.     

Ensemble method to measure the potential energy of nanoparticles in an optical trap

A method is described for measuring the potential energy of nanoparticles in an optical trap by trapping an ensemble of particles with a focused laser beam. The force balance between repulsive osmotic and confining gradient-force pressures determines the single-particle trapping potential independent of interactions between the particles. The ensemble nature of the measurement permits evaluation of single-particle trapping energies much smaller than k_BT. Energies obtained by this method are compared to those of single-particle methods as well as to theoretical calculations based on classical electromagnetic optics.     

纳米多孔结构镍基复合膜电极的电化学法制备及其电容特性

通过对电沉积法得到的Ni-Cu合金镀层进行电化学去合金化处理, 制备了纳米多孔结构金属镍膜. 采用循环伏安法对多孔金属镍膜在1 mol·L^-1 KOH溶液中进行阳极氧化处理, 获得了纳米多孔结构的镍基复合膜电极. 应用扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和电化学技术对所制备的膜电极的物理性质及赝电容特性进行了表征. SEM、XRD和XPS的测试结果表明, 所制备的纳米多孔结构镍基复合膜由Ni、Ni(OH)₂和NiOOH组成. 电化学实验结果显示, 该复合膜在20 A·g^-1的充放电电流密度下, 给出了578 F·g^-1的初始比电容; 在1000次充放电循环后, 它的比电容值为544 F·g^-1, 电容保持率为94%. 纳米多孔结构有利于KOH电解液的渗透, 从而促进反应物种在电极内部的传输; 纳米多孔的金属镍基体可以提高Ni(OH)₂膜的电子导电性; 纳米大小的Ni(OH)₂颗粒能够缩短质子的固相扩散路径. 上述因素是所制备的纳米多孔结构镍基复合膜电极具有优异赝电容特性的主要原因.     

Simple methods for assessing the conformational sensitivity of infrared bands by dichroism

In characterizing the overall orientation of polymers by infrared (IR) dichroism, the orientation function must be obtained from the dichroic ratios of conformationally insensitive bands. Identification of such bands is thus necessary prior to the calculation of the orientation function. In this study, we devise two simple methods for evaluating the conformational sensitivities of IR bands from the measurement of the dichroic ratio. Both methods are based on the fact that the orientation function calculated by all conformationally insensitive bands should be identical, while this is not true for conformationally sensitive bands. Poly(ether ether ketone) (PEEK) is used as an example to demonstrate the use of these methods.