Growth mechanism and characterization of zinc oxide microcages

We report the growth mechanism and structural properties of micrometer sized ZnO cages which were synthesized directly from Zn vapor deposition and oxidation. The ZnO microcages exhibit a hexagonal or spherical shape with partly or completely open surfaces and hollow interiors. The growth process of the microcages includes the deposition of Zn polyhedral particles, top face breaking of the Zn particles and Zn sublimation, and subsequent reaction to ZnO. By controlling the various growth stages, we obtained information on the growth mechanism of the ZnO cages, which appears to be different from a mechanism reported previously. The chemical composition and crystalline structure were studied using energy dispersive X-ray spectroscopy and transmission electron microscopy, respectively. The room-temperature photoluminescence spectrum indicates a large quantity of oxygen-vacancy related defects within the wall of the ZnO cages.     

Preparation and Spectral Characterization of Sulphur-Containing Diarylazo Compounds

Abstract

By reaction of arylazo-substituted aryl halides with mercaptides, new arylazo-substituted arylsulfides are formed. These compounds are deeply coloured and exhibit an intense absorption band in the visible region, which can be reproduced quantitatively and interpreted satisfactorily by means of quantum chemical calculations in the framework of the PPP and LHM methods, respectively.     

Guest-induced conformation shift of p-sulphonatothiacalix[4]arene in the solid state and solution manipulated by [Zn(dipy)3]2+

The ¹H NMR and X-ray analysis data reveal the guest-induced cone → partial cone and cone → 1,2-alternate conformational shift in aqueous methanol solutions and solid state for a p-sulphonatothiacalix[4]arene-[Zn(dipy)₃]²⁺ host–guest system. The experimental data, together with DFT calculations, show that the guest-induced conformational shift of p-sulphonatothiacalix[4]arene is facilitated by the deprotonation of phenolic groups.     

Metal-metal bond or isolated metal centers? Interaction of Hg(CN)2 with square planar transition metal cyanides

Three adducts have been prepared from Hg(CN)(2) and square planar M(II)(CN)(4)(2)(-) transition metal cyanides (M = Pt, Pd, or Ni, with d(8) electron shell) as solids. The structure of the compounds K(2)PtHg(CN)(6).2H(2)O (1), Na(2)PdHg(CN)(6).2H(2)O (2), and K(2)NiHg(CN)(6).2H(2)O (3) have been studied by single-crystal X-ray diffraction, XPS, Raman spectroscopy, and luminescence spectroscopy in the solid state. The structure of K(2)PtHg(CN)(6).2H(2)O consists of one-dimensional wires. No CN(-) bridges occur between the heterometallic centers. The wires are strictly linear, and the Pt(II) and Hg(II) centers alternate. The distance d(Hg)(-)(Pt) is relatively short, 3.460 A. Time-resolved luminescence spectra indicate that Hg(CN)(2) units incorporated into the structure act as electron traps and shorten the lifetime of both the short-lived and longer-lived exited states in 1 compared to K(2)[Pt(CN)(4)].2H(2)O. The structures of Na(2)PdHg(CN)(6).2H(2)O and K(2)NiHg(CN)(6).2H(2)O can be considered as double salts; the lack of heterometallophilic interaction between the remote Hg(II) and Pd(II) atoms, d(Hg)(-)(Pd) = 4.92 A, and Hg(II) and Ni(II) atoms, d(Hg)(-)(Ni) = 4.61 A, is apparent. Electron binding energy values of the metallic centers measured by XPS show that there is no electron transfer between the metal ions in the three adducts. In solution, experimental findings clearly indicate the lack of metal-metal bond formation in all studied Hg(II)-CN(-)-M(II)(CN)(4)(2)(-) systems (M = Pt, Pd, or Ni).     

The H2-phase of the lyotropic liquid crystal sodium 3,4,5-tris(omega-acryloyloxyundecyloxy)benzoate

The phase behaviour of the lyotropic liquid crystal sodium 3,4,5-tris(omega-acryloyloxyundecyloxy)-benzoate was investigated by small angle X-ray scattering. The water content of the lyotropic liquid crystal phase was varied between 8 and 20wt% and the investigations were performed in a temperature range up to 70^oC. A reversed hexagonal structure (H₂-phase) as well as the isotropic phase were observed. The lattice constant of the H₂-phase was found to be independent of the water content. An extremely small dependence on temperature could be found. Based on the shape of the molecules and the observed structural properties, a model for the arrangement of the molecules within the H₂-phase is given. The transition temperature from the H₂-phase to the isotropic phase decreases significantly from 60^oC for the sample with 8wt% water content to 30^oC for the sample with 20wt% water content.     

Mapping of Malus domestica allergens by 2-D electrophoresis and IgE-reactivity

The importance of apple allergens has been repeatedly emphasized, and their presence has been confirmed both in pollen and in fruits. In the present study, a combination of proteomic tools have been used to build a complete allergen map of apple. The water-soluble fraction of an apple extract was precipitated using a phenol-based procedure and separated by 2-DE. Initially four previously classified allergens, Mal d 1, Mal d 2, Mal d 3 and Mal d 4, could be identified in Western blots with polyclonal rabbit antibodies directed to the four respective allergens, and subsequently matched to the bands recognized by several patient sera. Further, all four known apple allergens were localized on a 2-DE map and they were matched with spots recognized by sera of patients with different allergic patterns. Moreover, a new, putative allergen could be identified using MS. We evaluated the influence of post-translational modifications and the immunoreactivity under different analytical conditions. The comparison of different visualization methods for 2-DE gels and blots revealed that even very low concentrations of the intact epitopes are detectable by IgEs of patients, and therefore might be sufficient to trigger allergic symptoms in sensitized individuals.     

Generalized Hermite Polynomials and the Heat Equation for Dunkl Operators

Based on the theory of Dunkl operators, this paper presents a general concept of multivariable Hermite polynomials and Hermite functions which are associated with finite reflection groups on ℝ ^N . The definition and properties of these generalized Hermite systems extend naturally those of their classical counterparts; partial derivatives and the usual exponential kernel are here replaced by Dunkl operators and the generalized exponential kernel K of the Dunkl transform. In the case of the symmetric group S _N , our setting includes the polynomial eigenfunctions of certain Calogero-Sutherland type operators. The second part of this paper is devoted to the heat equation associated with Dunkl's Laplacian. As in the classical case, the corresponding Cauchy problem is governed by a positive one-parameter semigroup; this is assured by a maximum principle for the generalized Laplacian. The explicit solution to the Cauchy problem involves again the kernel K, which is, on the way, proven to be nonnegative for real arguments. Received: 10 March 1997 / Accepted: 7 July 1997