Synthesis of several types of 2,8-dioxabicyclo[3.3.1]nonanes using amberlyst-15 as an efficient recyclable heterogeneous catalyst

A facile synthesis of 2,8-dioxabicyclo[3.3.1]nonane derivatives starting from simple molecules, such as 2-hydroxychalcones as one component and dimedone, 4-hydroxycoumarin, 2-hydroxynaphthoquinone, 2-naphthol or 1-naphthol, as the other has been achieved by use of amberlyst-15, a sulfonated polystyrene resin, as a recyclable heterogeneous catalyst. The methodology involves a domino sequence of Michael addition and two-stage cyclisation.     

Electrochemical deposition of uranium dioxide coatings on alloy 600: effect of annealing on Ni and Cu interlayer mixing

3.5–4.75 mg cm⁻² thick UO₂ coatings were electrodeposited using alkaline uranyl nitrate-ammonium oxalate bath on alloy 600 onto which nickel and copper interlayers were previously electrochemically formed. Micro laser Raman spectroscopy of annealed coating confirmed the formation of UO₂ by showing a peak at 447 cm⁻¹. Scanning electron microscopy showed uniform morphology with an average grain size of 1 µm. Glow discharge optical emission spectroscopy revealed no significant diffusion of nickel and copper into UO₂ due to annealing. Rutherford backscattering spectroscopy showed increased thickness of annealed coating. Scratch adhesion test indicated improved cohesive and adhesive strength of coating after annealing.

     

Preparation and chromatographic evaluation of new branch-type diamide-embedded octadecyl stationary phase with enhanced shape selectivity

A novel branch-type diamide-embedded octadecyl stationary phase was prepared by facile amidation. The preparation of this new phase involves the synthesis of new bifunctional silane ligand and surface modification of spherical silica via anchoring of silane coupling agent. The obtained diamide-embedded octadecyl stationary phase demonstrated excellent hydrophobic selectivity, as well as enhanced shape and planarity selectivity in comparison to commercial polymeric and monomeric C₁₈ phases, respectively, as revealed by the systematic investigation into its liquid chromatographic retention of isomeric polycyclic aromatic hydrocarbons. The applicability of this new stationary phase was further testified by the effective separation of isomeric compounds belong to different chemical classes, including chain isomers of alkylbenzenes, and positional isomers of substituted aromatics. An in-depth analysis of the separation mechanisms other than molecular shape recognition involved in the new stationary phase was performed using a linear solvation energy relationships model and compared with its monoamide and pure C₁₈ counterparts correspondingly. The performance of the new stationary phase in quantitative analysis of phenols from real-world samples was also evaluated.     

Dependence of photoconductivity on the crystallite orientations and porosity of polycrystalline ZnO films

Hexagonal ZnO films deposited on quartz glass, sapphire and glass substrates by sol–gel coating are found to be randomly oriented; maximum randomness is found in the film on quartz glass substrate. All the films are ultra-violet (UV) sensitive at around 360 nm sensitivity being maximum for the film with maximum randomness in the crystallite orientations. The film on quartz showed the lowest dark current and maximum photoresponse, which is related to the lowering of the barrier heights, introduced by the adsorbed oxygen at the grain boundaries. Faster decay in photocurrent is observed for the film deposited on glass, which is attributed due to the smaller crystallite sizes with porous microstructure of the film. PACS 73.61.Ga; 68.55.Jk; 73.50.Pz     

Growth of Bi-Sb alloy thin films and their characterization by TEM, PIXE and RBS

Polycrystalline bulk materials of Bi₉₃Sb₇ Bi₈₈Sb₁₂, Bi₈₅Sb₁₅ and Bi₈₀Sb₂₀ were synthesized by melt-quench technique starting from the stoichiometric mixture of constituent elements. The phase purity and compositional uniformity of bulk materials were investigated using powder X-ray diffraction (XRD) and proton induced X-ray emission (PIXE) experiments. The single phase formation and the compositional analysis of thin films were confirmed by transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS). X-ray diffraction studies confirmed the phase homogeneity of the materials. Atomic concentration ratio of constituent elements (Bi and Sb) determined by PIXE and RBS revealed that near-stoichiometric composition is nearly the same in the bulk as well as in thin film forms.     

Scattering amplitude and shift in self-energy in medium

Two simple proofs are presented for the first order virial expansion of the self-energy of a particle moving through a medium, characterised by temperature and/or chemical potential(s). One is based on the virial expansion of the self-energy operator itself, while the other is based on the analysis of its Feynman diagrams in configuration space. Received: 26 December 2001 / Published online: 5 April 2002     

$$\mathcal{P}\mathcal{T}$$ -supersymmetric partner of a short-range square well

In a box of size L, a spatially antisymmetric square-well potential of a purely imaginary strength ig and size l < L is interpreted as an initial element of the SUSY hierarchy of solvable Hamiltonians, the energies of which are all real for g < g _c (l). The first partner potential is constructed in closed form and discussed. Presented at the 3rd International Workshop “Pseudo-Hermitian Hamiltonians in Quantum Physics”, Istanbul, Turkey, June 20–22, 2005.     

Facile synthesis of high-density poly(octadecyl acrylate)-grafted silica for reversed-phase high-performance liquid chromatography by surface-initiated atom transfer radical polymerization

To introduce high-density polymeric organic phase onto silica, initiator-modified silica was prepared and then surface-initiated atom transfer radical polymerization (ATRP) ("grafting-from" method) was carried out with octadecyl acrylate. The resultant polymer-grafted silica was characterized by diffuse reflectance infrared Fourier transform, suspension-state (1)H NMR, solid-state (13)C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS-NMR), solid-state (29)Si-CP-MAS-NMR spectroscopies, elemental analysis and differential scanning calorimetry measurements. ATRP-based poly(octadecyl acrylate)-grafted silica (Sil-ODA(n)-1), was used as a stationary phase in high-performance liquid chromatography (HPLC) and the chromatographic behavior was evaluated by the retention studies of polycyclic aromatic hydrocarbons (PAHs) and aromatic positional isomers. Compared with previous poly(octadecyl acrylate)-grafted silica (Sil-ODA(n)), which was prepared by the "grafting-to" method, we have observed longer retention and greater selectivity for Sil-ODA(n)-1 towards PAHs event at higher temperature.