Das amphotere Verhalten von Titan(IV)-chlorid in Phosphoroxychlorid

Zusammenfassung Konduktometrische und potentiometrische Titrationen zeigen, daß TiCl₄ in POCl₃ sowohl 2 Chloridionen aufnehmen als auch ein Chloridion abgeben kann. Die Existenz der Koordinationsformen [TiCl₆]^2–, [TiCl₅]^– _solv, (TiCl₄)_solv und [TiCl₃]⁺ _solv läßt sich nachweisen. Das Verhältnis von Donor-und Akzeptorstärke ist von der Konzentration abhängig; in verd. Lösungen ist TiCl₄ vor allem Donor, in konz. Lösungen Akzeptor.Mit 6 AbbildungenZugleich 21. Mitt. der Reihe: Das Solvosystem Phosphoroxychlorid.20. Mitt.:M. Baaz, V. Gutmann undL. Hübner, J. Inorg. Nucl. Chem., im Druck.     

Synthesis and Biological Activity of Some New Pyrazolo[3,4‐b]Pyrazines

New derivatives of pyrazolo[3,4‐b]pyrazine and related heterocycles were prepared starting from 6‐amino‐3‐methyl‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyrazine‐5‐carbonitrile ( 2 ) and using the key intermediates 4 , 5 , 6 , 14 , 15 and 16 . Some of the prepared compounds were evaluated for their antifungal and antibacterial activities.     

Quantum dynamics of heavy light heavy reactions: Application to (F + CH4 → FCH3 + H) reaction

We apply the time-dependent theory to the collinear exchange reaction F + CH₄ → FCH₃ + H. We have performed detailed calculations on two-dimensional potential surfaces representing the ground electronic potentials of the collinear F + CH₄ → FCH₃ + H reaction, at incident energies. Transmission coefficients range from zero to unity, depending upon the incident energy. Normal modes of vibrations are displayed along the reaction path.     

Investigation of solid-state reaction in Ag/Sn nanostructured thin films at room temperature

Diffusion intermixing processes in nanostructured Ag/Sn thin-film system at room temperature were investigated by means of secondary neutral mass Spectrometry depth profiling technique. As it was confirmed by X-ray diffraction too, the reaction started already in the as-deposited sample. Since the bulk diffusion was frozen at room temperature, the Ag₃Sn phase was formed along the grain boundaries (GBs), gradually consuming the interior of grains, and was grown perpendicular to the GBs. At the same time, formation and growth of a small compact reaction layer near the interface were observed and the shift of the bordering parallel interfaces was controlled by GB diffusion. From the kinetics of the diffusion process in the above two mechanisms, both the interface velocity in the diffusion-induced grain boundary motion regime as well as the coefficient of parabolic growth in the planar growth regime were determined.     

Characterization of optical properties of Porous Silicon using Photoacoustic Technique

Photoacoustic absorption spectra of the porous silicon samples (P-Si) of different thickness and porosity percentage were measured at different modulation frequency. The absorption edge of the P-Si layer for all samples shows a blue shift from that of crystalline silicon (C-Si) at 1.1 eV. At low modulation frequency the estimated energy gap (1.88 eV) is almost the same for all samples and the PA signal increases as the porosity percentage increases. At the higher modulation frequency, the spectra show an increase in the energy gap indicating the effect of quantum confinement as the porosity increasing. The Raman shifts of the P-Si samples are correlated with the particle size leading to an estimated average particle size. The quantum confinement interpretation of the PA results is in agreement with the Raman measurements that indicate the presence of such nanostructure in the P-Si layer.     

Photoacoustic characterization of optical and thermal properties of CdSe quantum dots

We report on the optical absorption properties of as prepared CdSe quantum dots (QDs) measured by the photoacoustic (PA) method. CdSe QDs were fabricated by the chemical solution deposition (CD) technique. With increasing growing time, the redshift of the PA spectra can be clearly observed and optical absorption in the visible region due to CdSe Q-dots is demonstrated. The average diameters of the CdSe QDs for each growth time interval is estimated using the effective mass approximation giving diameters ranging from 2.6 nm to 3.4 nm. These values are comparable to those obtained by scanning tunnelling microscope (STM). Thus, PA spectroscopy is useful to obtain the QDs sizes as grown and with no further preparation. In addition, PA measurements provide also the thermal diffusivity of samples of different sizes which in this case show an increase by at least an order of magnitude than the bulk value.     

Synthesis and characterization of Mg-doped ZnO hollow spheres

Mg-doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Mg:Zn atomic ratio from 0 to 7%. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and magnesium acetate tetrahydrate were heated under refluxing at 65 °C using methanol as a solvent. X-ray diffraction analysis reveals that the Mg-doped ZnO crystallizes in a wurtzite structure with crystal size of 5–12 nm. These nanocrystals self-aggregated themselves into hollow spheres of size of 800–1100 nm. High resolution transmission electron microscopy images show that each sphere is made up of numerous nanoparticles of average diameter 5–11 nm. The XRD patterns, SEM and TEM micrographs of doping of Mg in ZnO confirmed the formation of hollow spheres indicating that the Mg²⁺ is successfully substituted into the ZnO host structure of the Zn²⁺ site. Furthermore, the UV–Vis spectra and photoluminescence (PL) spectra of the ZnO nanoparticles were also investigated. The band gap of the nanoparticles can be tuned in the range of 3.36–3.55 eV by the use of the dopants.     

Computational method for solving space fractional Fisher's nonlinear equation

This paper aims to present a general framework of the quadratic spline functions to develop a numerical method for solving the nonlinear space fractional Fisher's equation. Using Von Neumann method, the proposed method is shown to be conditionally stable. Finally, a numerical example is given to verify the effectiveness of the proposed algorithm. The results reveal that the proposed approach is very effective, convenient, and quite accurate to such considered problems. Copyright © 2013 John Wiley & Sons, Ltd.     

A Validated TLC-Densitometric Method for the Simultaneous Determination of Formoterol Fumarate and Budesonide in Pressurized Metered-Dose Inhaler

JPC – Journal of Planar Chromatography – Modern TLC - A simple and robust thin-layer chromatography (TLC) method has been developed and validated for the simultaneous quantitative...