A “sodium trap” based on benzo-15-crown-5 with an exocyclic N-(thiophosphoryl)thiourea moiety

For N-(thio)phosphorylthioureas of the common formula RC(S)NHP(X)(OiPr)₂HL^I (R = N-(4′-aminobenzo-15-crown-5), X = S), HL^II (R = N-(4′-aminobenzo-15-crown-5), X = O), HL^III (R = PhNH, X = S), HL^IV (R = PhNH, X = O), and (N,N′-bis-[C(S)NHP(S)(OiPr)₂]₂-1,10-diaza-18-crown-6) H₂L^V, salts LiL^I,III,IV, NaL^I–IV, KL^I–IVM₂L^V (M = Li⁺, Na⁺, K⁺), Ba(L^I,III,IV)₂, and BaL^V have been synthesized and investigated. Compounds NaL^I,II quantitatively drop out as a deposit in ethanol medium, allowing the separation of Na⁺ and K⁺ cations. This effect is not displayed for the other compounds. The crystal structures of HL^III and the solvate of the composition [K(Me₂CO)L^III] have been investigated by X-ray crystallography.     

Label-free screening of bio-molecular interactions

The majority of techniques currently employed to interrogate a biomolecular interaction require some type of radio- or enzymatic- or fluorescent-labelling to report the binding event. However, there is an increasing awareness of novel techniques that do not require labelling of the ligand or the receptor, and that allow virtually any complex to be screened with minimal assay development. This review focuses on three major label-free screening platforms: surface plasmon resonance biosensors, acoustic biosensors, and calorimetric biosensors. Scientists in both academia and industry are using biosensors in areas that encompass almost all areas drug discovery, diagnostics, and the life sciences. The capabilities and advantages of each technique are compared and key applications involving small molecules, proteins, oligonucleotides, bacteriophage, viruses, bacteria, and cells are reviewed. The role of the interface between the biosensor surface (in the case of SPR and acoustic biosensors) and the chemical or biological systems to be studied is also covered with attention to the covalent and non-covalent coupling chemistries commonly employed.     

Ag/Ag3PO4/g-C3N4三元复合光催化剂的制备及其可见光驱动下的光催化活性增强

报道了一种新型Ag/Ag₃PO₄/g-C₃N₄三元复合光催化剂的制备及其半导体界面处的快速载流子分离所引起的光催化活性的显著增强效应。通过X射线衍射,扫描电子显微镜,紫外-可见吸收光谱以及光致发光光谱等就其晶体结构、形貌、组分、光学吸收以及载流子的快速分离行为进行了表征与分析。以罗丹明B作为模型化合物分子,研究发现,所制备的Ag/Ag₃PO₄/g-C₃N₄三元复合光催化剂在可见光照射下表现出比Ag₃PO₄以及Ag₃PO₄/g-C₃N₄二元催化剂更为优异的光催化活性。研究认为,Ag₃PO₄表面尺寸约为40 nm的Ag纳米粒子在可见光下受激所产生的等离子表面共振效应以及Ag₃PO₄与g-C₃N₄界面处所形成的类似异质结结构对所制备的Ag/Ag₃PO₄/g-C₃N₄三元复合光催化剂光催化活性的显著增强起到重要作用。     

Design of tungsten complex gratings for thermophotovoltaic radiators

The concept of a kind of complex grating based on superposition of two simple binary gratings is described for potential application as thermophotovoltaic (TPV) radiators. The grating with one-dimensional microstructured surface is relatively easy to fabricate and the predicted directional-spectral emittance exhibits apparent enhancement over simple grating structures. Specifically, the emittance of the complex grating has a wider peak in the spectral region where the quantum efficiency of TPV cells is high. This enhancement can be explained by the excitation of surface plasmon polaritons coupled with the grating microstructures. At longer wavelengths, the emittance remains low to reduce the radiative heat transfer from the radiator to the TPV cells by low-energy photons that do not produce any photocurrent. Calculations using the rigorous coupled-wave analysis demonstrate that the emittance peak is insensitive to the direction, suggesting that the proposed structure may be well suitable for TPV applications.     

Strong optical transmission through the ellipsoid metal-film nanohole arrays

The transmission characteristics of a metallic film with subwavelength ellipsoid nanohole arrays are investigated by using the three-dimensional finite-difference time-domain (3D-FDTD) method. The extraordinary transmission is attributed to the collaboration of localized waveguide resonance and surface plasmon resonance. The influences of the lattice constant and the hole shape on the transmission are studied. By analyzing the picture of electric field and electromagnetic energy distribution, we show the mechanisms of the two different resonances: Localized waveguide resonance mode can be confined inside the ellipsoid holes region, while electric field and electromagnetic energy are localized separately at the two ends of ellipsoid holes for the surface plasma resonance mode. Supported by the National Natural Science Foundation of China (Grant No. 60708014), the Distinguished Youth Foundation of Hunan Province (Grant No. 03JJY1008), the Science Foundation for Post-doctorate of China (Grant No. 2004035083), and the Natural Science Foundation of Hunan Province (Grant No. 06JJ20034)     

Mobility and conductivity of ionic and bonded defects in hydrogen-bonded chains with nonlinear interactions

The proton conductivity and the mobility arising from motions of the ionic and bonded defects, in hydrogen-bonded molecular systems are investigated by means of the quantum mechanical method. Our two component model goes beyond the usual classical harmonic interaction by inclusion of a quartic interaction potential between the nearest-neighbor protons. Among the rich variety of soliton patterns obtained in this model, we focus our attention to compact kink (kinkon) solutions to calculate analytically, the mobility of the kinkon-antikinkon pair and the specific electrical-conductivity of the protons transfer in the hydrogen-bonded systems under an externally applied electrical-field through the dynamic equation of the kinkon-antikinkon pair. For ice, the mobility and the electrical conductivity of the proton transfer obtained are about 5.307×10^-7 m²  V^-1  s^-1 and 6.11×10^-4 Ω^-1 m^-1, respectively. The results obtained are in qualitative agreement with experimental data.     

Metal-insulator transition in Ni-doped Na0.75CoO2: Insights from infrared studies

Nickel substitution at the cobalt site in Na_0.75CoO₂ induces an upturn in the resistivity on lowering the temperature, with the metal-to-insulator transition temperature (T _MIT) increasing with the Ni content. Low temperature far infrared measurements on polycrystalline samples of Na_0.75CoO₂ and Na_0.75Co_0.95Ni_0.05O₂, the latter having T _MIT ∼ 175 K, have been carried out. Dramatic changes in the Na mode frequencies, and relative intensities of the out-of-plane modes corresponding to the two Na sites are observed, coincident with the MIT in Na_0.75Co_0.95Ni_0.05O₂. It is argued that these changes are associated with a charge ordering of the CoO₂ layer, associated with the metal-insulator transition.     

The role of intermolecular vibrations and reorganization of a reaction system in tunneling reactions with H atom transfer. A Debye model for the medium

Mechanisms of temperature dependence of the rate constants for two types of solid-state tunneling chemical reactions, namely, transfer of an H atom between two molecules and intramolecular transfer, are analyzed. To this end, an analytical expression for the rate constant for tunneling atom transfer in solids is derived in the framework of a modified theory of nonradiative transitions. The mechanisms of the temperature dependence of the rate constant considered in this work include oscillations of the potential barrier to chemical reaction in intermolecular fluctuations and reorganization of the medium. The effect of pressure on the distance between reactants and on the frequency of intermolecular vibrations is taken into account. The theory developed is used to interpret experimental data on tunneling transfer of an H atom in two reactions: a) intramolecular hydrogen transfer in a matrix-isolated formic acid molecule entrapped in an argon crystal and b) H atom transfer from a fluorene molecule to an excited acridine molecule in a fluorene crystal. Dedicated to the 90th anniversary of the L. Ya. Karpov Institute of Physical Chemistry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1073–1085, June, 2008.     

Strongly nonlinear modal equations for nearly integrable PDEs

Summary The purpose of this paper is the derivation of reduced, finite-dimensional dynamical systems that govern the near-integrable modulations ofN-phase, spatially periodic, integrable wavetrains. The small parameter in this perturbation theory is the size of the nonintegrable perturbation in the equation, rather than the amplitude of the solution, which is arbitrary. Therefore, these reduced equations locally approximate strongly nonlinear behavior of the nearly integrable PDE. The derivation we present relies heavily on the integrability of the underlying PDE and applies, in general, to anyN-phase periodic wavetrain. For specific applications, however, a numerical pretest is applied to fix the truncation orderN. We present one example of the reduction philosophy with the damped, driven sine-Gordon system and summarize our present progress toward application of the modulation equations to this numerical study.     

用双折射晶体相位延迟法选纵横的理论分析和实验研究

提出了一种新的固体激光器纵模选择技术，分析了该方法的损耗调制原理，用半经典理论建立二模光场竞争的运动方程，并对这种方法的纵模选择能力进行了计算。实验中用KTP和方解石两种双折射晶体都实现了固体激光器的单纵模振荡，用KTP晶体获得了CW 44 mW的单纵模激光输出，稳定性优于±3％。实验表明在半导体激光泵浦的中小功率固体激光器中用该方法选纵模具有稳定、可靠的优点。