Excited States of Xanthene Analogues: Photofragmentation and Calculations by CC2 and Time‐Dependent Density Functional Theory

Action spectroscopy has emerged as an analytical tool to probe excited states in the gas phase. Although comparison of gas‐phase absorption properties with quantum‐chemical calculations is, in principle, straightforward, popular methods often fail to describe many molecules of interest—such as xanthene analogues. We, therefore, face their nano‐ and picosecond laser‐induced photofragmentation with excited‐state computations by using the CC2 method and time‐dependent density functional theory (TDDFT). Whereas the extracted absorption maxima agree with CC2 predictions, the TDDFT excitation energies are blueshifted. Lowering the amount of Hartree–Fock exchange in the DFT functional can reduce this shift but at the cost of changing the nature of the excited state. Additional bandwidth observed in the photofragmentation spectra is rationalized in terms of multiphoton processes. Observed fragmentation from higher‐lying excited states conforms to intense excited‐to‐excited state transitions calculated with CC2. The CC2 method is thus suitable for the comparison with photofragmentation in xanthene analogues.     

Separation of113mIn from113Sn on an isotope generator with inorganic ionite

A method of preparation of hydrated zirconium oxide suitable for^113mIn generators was elaborated. A good separation of^113mIn from¹¹³Sn was obtained in the course of routine use of generator, with a very small admixture of zirconium in the eluate.     

Self-organized nanotubular TiO2 matrix as support for dispersed Pt/Ru nanoparticles: Enhancement of the electrocatalytic oxidation of methanol

We explore oxidative electrocatalytic properties of a system consisting of bimetallic Pt/Ru nanoparticles dispersed over a nanotubular self-organized TiO₂ matrix. The nanotubular TiO₂ layers consist of individual tubes of 100 nm diameter, 500 nm length and 15 nm wall thickness. This nanotubular TiO₂ support provides a high surface area and it significantly enhances the electrocatalytic activity of Pt/Ru for methanol oxidation (relative to the performance of Pt/Ru at the same loading but immobilized on a conventional compact TiO₂ support). Annealed to anatase, the TiO₂ nanotubular support exhibits even higher enhancement effect during electrooxidation of methanol than when used in the “as-formed” amorphous structure. The overall electrocatalytic activity of the system can be further increased by illumination with UV-light (wavelength 325 nm).     

Some aspects of thermal destruction of polyurethanes

A number of Polyurethane elastomers were investigated by means of non-isothermal thermogravimetry to set a general procedure for numerical estimation of kinetic parameters. The value of an assumed objective function. determining the accuracy of the estimation depends on many factors as: the considered region of a TG-curve, the method of choosing points from the curve, and the initial values of the pre-exponential factor and the reaction order. After the optimal conditions were evaluated, the minimum values of the objective function and the corresponding triplet values of kinetic parameters were obtained. Among these, only the activation energy can be considered as a semiquantitative estimate of thermal stability.

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Zusammenfassung Eine Anzahl von Polyurethan-Elastomeren wurde mittels nichtisothermer Thermogravimetrie untersucht, um eine allgemeingültige Verfahrensweise zur numerischen Abschätzung kinetischer Parameter abzuleiten. Der Wert einer angenommenen objektiven Funktion zur Bestimmung der Genauigkeit der Abschätzung hängt von mehreren Faktoren ab: von dem in Betracht gezogenen Teil der TG-Kurve, von der Auswahlmethode für die berücksichtigen Meßpunkte, und von den anfänglichen Werten des Präexponentiellen Faktors und der Reaktionsordnung. Nachdem die optimalen Bedingungen ermittelt waren, wurden die minimalen Werte der objektiven Funktion und die entsprechenden Wertetripel für die kinetischen Parameter erhalten. Von diesen kann nur die Aktivierungsenergie als halbquantitatives Maß für die thermische Stabilität betrachtet werden.

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