Unusually Large Lattice Mismatch‐Induced Optical Behaviors of Au@Cu–Cu2O Core–Shell Nanocrystals with Noncentrally Located Cores

To extend the optical property characterization of metal–Cu₂O polyhedra, 50 nm Au@Cu cubic cores are used to fabricate Au@Cu–Cu₂O core–shell cubes, octahedra, and rhombic dodecahedra with tunable sizes. Despite the unusually large lattice mismatch of 15.1% between Cu and Cu₂O, fine adjustment in the volumes of reagents introduced allows the formation of these heterostructures. To relieve the lattice strain, the metal cores are essentially never found to locate at the particle center, and slight lattice spacing shifts are recorded. Although efforts are made to reduce the heterostructure sizes, the Cu₂O shells are generally too thick to reveal surface plasmon resonance (SPR) absorption band from the metal cores. Only the Au@Cu–Cu₂O cubes with many cores located near the particle corners show observable SPR band red‐shift, but UV–vis spectra of all particle shapes are still dominated by Cu₂O absorption and light scattering bands. Au@Cu–Cu₂O cubes consistently show the most red‐shifted absorption bands than those of octahedra resulting from the optical facet effects.     

Thermal Stability of Modified i‐Motif Oligonucleotides with Naphthalimide Intercalating Nucleic Acids

In continuation of our investigation of characteristics and thermodynamic properties of the i‐motif 5′‐d[(CCCTAA)₃CCCT)] upon insertion of intercalating nucleotides into the cytosine‐rich oligonucleotide, this article evaluates the stabilities of i‐motif oligonucleotides upon insertion of naphthalimide (1H‐benzo[de]isoquinoline‐1,3(2H)‐dione) as the intercalating nucleic acid. The stabilities of i‐motif structures with inserted naphthalimide intercalating nucleotides were studied using UV melting temperatures (T_m) and circular dichroism spectra at different pH values and conditions (crowding and non‐crowding). This study indicated a positive effect of the naphthalimide intercalating nucleotides on the stabilities of the i‐motif structures compared to the wild‐type structure which is in contrast to a previous observation for a pyrene‐intercalating nucleotide showing a decrease in T_m values.     

Modeling and deformation analyzing of InSb focal plane arrays detector under thermal shock

A higher fracture probability appearing in indium antimonide (InSb) infrared focal plane arrays (IRFPAs) subjected to the thermal shock test, restricts its final yield. In light of the proposed equivalent method, where a 32 × 32 array is employed to replace the real 128 × 128 array, a three-dimensional modeling of InSb IRFPAs is developed to explore its deformation rules. To research the damage degree to the mechanical properties of InSb chip from the back surface thinning process, the elastic modulus of InSb chip along the normal direction is lessened. Simulation results show when the out-of-plane elastic modulus of InSb chip is set with 30% of its Young’s modulus, the simulated Z-components of strain distribution agrees well with the top surface deformation features in 128 × 128 InSb IRFPAs fracture photographs, especially with the crack origination sites, the crack distribution and the global square checkerboard buckling pattern. Thus the Z-components of strain are selected to explore the deformation rules in the layered structure of InSb IRFPAs. Analyzing results show the top surface deformation of InSb IRFPAs originates from the thermal mismatch between the silicon readout integrated circuits (ROIC) and the intermediate layer above, made up of the alternating indium bump array and the reticular underfill. After passing through both the intermediate layer and the InSb chip, the deformation amplitude is reduced firstly from 2.23 μm to 0.24 μm, finally to 0.09 μm. Finally, von Mises stress criterion is employed to explain the causes that cracks always appear in the InSb chip.     

Controlling the surface buckling wrinkles by patterning the material system of hard-nano-film/soft-matter-substrate

Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant substrate,which exploits the curvatures of the curve cracks designed on the stiff film.The procedures of the method are summarized as:1)curve patterns are fabricated on the surface of PDMS(Polydimethylsiloxane)substrate and then the aluminum film with the thickness of several hundred nano-meters is deposited on the substrate;2)the curve patterns are transferred onto the aluminum film and lead to cracking of the film along the curves.The cracking redistributes the stress in the compressed film on the substrate;3)on the concave side of the curve,the wrinkling of the film surface is suppressed to be identified as shielding effect and on the convex side the wrinkling of the film surface is induced to be identified as inductive effect.The shielding and inductive effects make the dis-ordered wrinkling and buckling controllable.This phenomenon provides a potential application in the fabrication of flexible electronic devices.     

时隙交织信道的四波混频均衡再生

给出了适用于多波长再生的数据抽运简并四波混频(FWM)耦合模方程组,提出了时隙交织波长信道再生的准相位匹配均衡方法。从优化设计简并FWM相位失配因子入手,针对实验室已有的光纤,实现了4个固定波长信道的均衡再生;通过设计光纤参数,在一定带宽范围内可实现任意4个波长的均衡再生。计算结果表明,再生输出信号的脉冲峰值功率、消光比(ER)和Q值之间的差异分别不超过0.25dB、0.42dB和1.5。     

三维光存储中折射率失配引起的球差补偿

为实现三维光存储中折射率失配引起的球差补偿,建立了光学存储系统模型,获得了折射率失配引起的波前偏差函数与存储深度的表达式.采用泽尔尼克循环多项式对波前偏差函数进行补偿展开.在双光子荧光和单光子共焦荧光读出方式下,均可获得读出荧光强度与存储深度的关系:在折射率失配引起的球差未得到补偿矫正的情况下,存储深度在200 μm左右读出荧光强度基本上下降为零;当折射率失配引起的初级球差被补偿矫正后,读出荧光强度随存储深度的下降得到较好改善;当折射率失配引起的二级球差被补偿矫正后,存储深度在1 mm内存储点强度随深度基本上没有明显地变化.并且对像差补偿方法进行了具体地分析.     

5-甲基胞嘧啶及胞嘧啶无辐射失活的半经典动力学模拟和CASSCF计算

采用半经典动力学方法模拟了5-甲基胞嘧啶(5m-Cyt)和胞嘧啶(Cyt)在267 nm紫外光辐射下的光物理失活过程. 模拟发现, 5m-Cyt 和Cyt 的激发态通过C₅－C₆键的扭曲以及甲基(或H₅)和H₆原子平面外振动失活.失活时, 甲基(或H₅)和H₆原子几乎与环面垂直并指向不同方向, 形成“双自由基态”. 由于甲基的体积比H原子的大, 振动频率较小, 使得C₅原子的变形受到抑制, 导致5m-Cyt 的激发态寿命比胞嘧啶更长. 完全活性空间自洽场(CASSCF)计算显示, 5m-Cyt的圆锥交叉(CI)点能量比Cyt 高0.3 eV, 这也证明5m-Cyt演化至CI 需要克服更大的能垒, 因此激发态寿命长于胞嘧啶.     

Effects of divalent alkaline earth ions on the magnetic and transport features of La0.65A0.35Mn0.95Fe0.05O3 (A = Ca, Sr, Pb, Ba) compounds

We have studied the magnetic and transport properties of Fe doped La_0.65A_0.35Mn_0.95Fe_0.05O₃ (A = Ca, Sr, Pb, Ba) manganites. All the compositions show ferromagnetic/metal to paramagnetic/insulator transition (T_C) except the Pb doped sample which is insulating and ferromagnetic (FM) in the entire temperature range. The magnetization and T_C are decreased by decreasing the cation size on La site. The transition temperature and magnetic moment at 77 K is a maximum for Sr doped sample and is decreasing if we increase or decrease the cation size from Sr size. The maximum value of T_C and magnetic moment for Sr based sample is most likely due to the closer ionic sizes of La and Sr as compared to the other dopants (Ca, Pb, and Ba). We observed a spin freezing type effect in the Pb doped sample below 120 K in resistivity, ac susceptibility and in magnetization. This suggests that the AFM interactions introduced by the Fe are most effective in the Pb doped composition leading to increased competition between the FM and AFM interactions. This FM and AFM interaction generates some degree of frustration leading to the appearance of spin glass like phase whose typical magnetic behavior is studied for small ion when the metallic like behavior is lost.     

Selective Determination of Cytosine Based on Its Fluorogenic Reaction with Triethylamine/Chloroacetonitrile

Abstract

A sensitive fluorometric method is described For selective determination of cytosine in nucleobases. The method is based on chemical derivatization of cytosine by triethylamine/chloroacetonitrile. The effects of solvent, reaction temperature, reaction time and concentration of reagents on the efficiency of the reaction were studied. A good linear relationship between fluorescence intensities and cytosine concentrations in the range of 2.0–800 ng/mt was observed. The detection limit for cytosine is 0.6 ng/ml (S/N=3). The relative standard deviations (7 replicates) for measurements of 50 and 500 ng/ml cytosine were 2.1 and 2.5%, respectively.     

Off‐center shallow donors in a spherical Si quantum dot with dielectric border

Within the effective mass approximation and using a finite element method, the ground state energy and electron cloud localization of the shallow donors in a Si quantum dot (QD) with dielectric border are calculated. Simultaneous effects of dielectric mismatch (DM) at the core–shell interface, the impurity radial position, and the external electric field on the electronic properties are investigated. We found that (i) for a freestanding QD, the binding energy is strongly enhanced due to the additional interactions of the electron with the polarization charges; (ii) the electron cloud distribution can be easily modulated by varying the impurity position; (iii) the electric field‐induced shift in energy levels increases with the DM. Therefore, the electronic energy levels of the nanocrystal could be tuned by properly tailoring the heterostructure parameters (DM with the surrounding matrix, impurity location) as well as by varying the electric field strength. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012