Bulk plasmon‐polaritons in hyperbolic nanorod metamaterial waveguides

Hyperbolic metamaterials comprised of an array of plasmonic nanorods provide a unique platform for designing optical sensors and integrating nonlinear and active nanophotonic functionalities. In this work, the waveguiding properties and mode structure of planar anisotropic metamaterial waveguides are characterized experimentally and theoretically. While ordinary modes are the typical guided modes of the highly anisotropic waveguides, extraordinary modes, below the effective plasma frequency, exist in a hyperbolic metamaterial slab in the form of bulk plasmon‐polaritons, in analogy to planar‐cavity exciton‐polaritons in semiconductors. They may have very low or negative group velocity with high effective refractive indices (up to 10) and have an unusual cut‐off from the high‐frequency side, providing deep‐subwavelength (λ₀/6–λ₀/8 waveguide thickness) single‐mode guiding. These properties, dictated by the hyperbolic anisotropy of the metamaterial, may be tuned by altering the geometrical parameters of the nanorod composite.

     

Isostructural copper-zinc mixed metal complexes for single source deposition of Cu-ZnO composite thin films

The mixed metal complex [Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)Br]·THF (1) and its isostructural analogues ([Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)Cl]·THF (2) and [Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)Cl/Br]·THF (3)) have been prepared by a simple metal ligand assembly method and were characterized by their melting points, elemental analysis, IR spectroscopy, thermogravimetry and single crystal X-ray structures. The compounds are distinguished only by the nature of the halide ions and are made up of the same [Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)X]·THF molecular building block with Cu(3)ZnO(4) cubane moieties as the central core in which the four metal ions and four oxygen atoms are joined together in alternate positions of the cuboid. All the complexes crystallize with similar packing and crystallographically related symmetry settings, distinguished mainly by the degree of disorder within the complexes and the ordering of the complexes in the structures. The triclinic cell of (1) emulates the monoclinic cell of (2) and is pseudomerohedrally twinned by a symmetry operation of the monoclinic cell. The molecules in (2) are 1:1 disordered around a crystallographic mirror plane. The structure of the mixed halogen compound (3) in turn is a superstructure of the less symmetric structures of (1) and (2) formed by ordering of the complexes along the longest axis of (3). Aerosol-assisted chemical vapour deposition (AACVD) experiments showed that they are promising precursors to deposit thin films of crystalline Cu/ZnO composites. The surface morphology, microstructure, chemical composition and crystallinity of the resulting Cu/ZnO composite thin films were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDAX), which suggest that the films are thin, crystalline, uniform, smooth and tightly adherent to the substrates with average crystallite sizes in a range between 40.2 and 80.0 nm. Particle sizes, shapes and film morphology were investigated as a function of precursor and decomposition temperature.     

Fluorometric method for the determination of hydrogen peroxide and glucose with Fe3O4 as catalyst

In this paper, we utilized the instinct peroxidase-like property of Fe₃O₄ magnetic nanoparticles (MNPs) to establish a new fluorometric method for determination of hydrogen peroxide and glucose. In the presence of Fe₃O₄ MNPs as peroxidase mimetic catalyst, H₂O₂ was decomposed into radical that could quench the fluorescence of CdTe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdTe QDs by H₂O₂ producer with Fe₃O₄ MNPs catalyst, which can be used to detect glucose. Under the optimal reaction conditions, a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of H₂O₂ from 1.8 × 10⁻⁷ to 9 × 10⁻⁴ mol/L with a detection limit of 1.8 × 10⁻⁸ mol/L. And a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of glucose from 1.6 × 10⁻⁶ to 1.6 × 10⁻⁴ mol/L with a detection limit of 1.0 × 10⁻⁶ mol/L. The proposed method was applied to the determination of glucose in human serum samples with satisfactory results.     

Synthesis,spectroscopic, and biological studies of tris[(dimethylethylsilyl) methylene]tin mono(or di)thiophosphates

Twenty-one new compounds of the general structure (EtMe₂SiCH₂)₃SnSP(X)(OR₁)(OR₂) (X=O:R₁=C₂H₅, R₂-substituted phenyl; X=S:R₁=R₂=hydrocarbyl) have been synthesized. Their structures were characterized by IR, ¹H, ¹¹⁹Sn, and ³¹PNMR spectroscopy and by MS and elemental analyses. ¹¹⁹Sn NMR measurements of chemical shifts have shown that there is a good linear relationship of ¹¹⁹Sn chemical shifts with Hammett para-substituent constants. The results of biological tests show that the compounds possess good acaricidal activity. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:299–305, 1998     

Numerical analysis of a corrected Smagorinsky model

The classical Smagorinsky model's solution is an approximation to a (resolved) mean velocity. Since it is an eddy viscosity model, it cannot represent a flow of energy from unresolved fluctuations to the (resolved) mean velocity. This model has recently been corrected to incorporate this flow and still be well-posed. Herein we first develop some basic properties of the corrected model. Next, we perform a complete numerical analysis of two algorithms for its approximation. They are tested and proven to be effective.