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- ItemTowards efficient initiators for two-photon induced polymerization: Fine tuning of the donor/acceptor properties(Cambridge : Royal Society of Chemistry, 2019) Holzer, Brigitte; Lunzer, Markus; Rosspeintner, Arnulf; Licari, Giuseppe; Tromayer, Maximilian; Naumov, Sergej; Lumpi, Daniel; Horkel, Ernst; Hametner, Christian; Ovsianikov, Aleksandr; Liska, Robert; Vauthey, Eric; Fröhlich, JohannesIn this work we present the design, synthesis and systematic investigation of the optical properties of symmetric triphenylamine (TPA)-substituted thiophenes. The use of electron-donating (-OMe, -tBu, -Me, -TMS), -neutral (-H) or -withdrawing (-F, -CN, -SO2Me) substituents gives rise to D-A-D based two-photon absorption (2PA) chromophores. The photophysical properties of these compounds, including one-photon absorption and 2PA using two-photon-excited fluorescence, were investigated in different organic solvents with varying polarity. The maximum 2PA cross sections prove to be strongly dependent on the nature of the TPA substituent and range between ~173 GM (Goeppert-Mayer units) and 379 GM. Although most of the investigated substances also exhibit high fluorescence quantum yields, two-photon absorption screening tests of an acrylate monomer formulation revealed the efficiency of these materials as 2PA photoinitiators. These results are supported by quantum chemical calculations of the spin density distribution indicating that the mechanism of polymerization initiation using acrylate monomer is favored by strong localization of the unpaired electrons in the triplet state on the C2 carbon of the thiophene moiety. © 2019 The Royal Society of Chemistry.
- ItemReaction of 1-propanol with Ozone in Aqueous Media(Basel : Molecular Diversity Preservation International, 2019) Reisz, Erika; Tekle-Röttering, Agnes; Naumov, Sergej; Schmidt, Winfried; Schmidt, Torsten C.The main aim of this work is to substantiate the mechanism of 1-propanol oxidation by ozone in aqueous solution when the substrate is present in large excess. Further goals are assessment of the products, their formation yields as well as the kinetic parameters of the considered reaction. The reaction of ozone with 1-propanol in aqueous solution occurs via hydride transfer, H-abstraction and insertion. Of these three mechanisms, the largest share is for hydride transfer. This implies the extraction of an hydride ion from the activated C-H group by O3 according to reaction: (C2H5)(H)(HO)C-H + O3 ?[(C2H5)(H)(HO)C-H+O3?]cage ?(C2H5)(H)(HO)C+ + HO3 -. The experimentally determined products and their overall formation yields with respect to ozone are: propionaldehyde-(60 ± 3)%, propionic acid-(27.4 ± 1.0)%, acetaldehyde-(4.9 ± 0.3)%, acetic acid-(0.3 ± 0.1)%, formaldehyde-(1.0 ± 0.1)%, formic acid-(4.6 ± 0.3)%, hydrogen peroxide- (11.1 ± 0.3)% and hydroxyl radical-(9.8 ± 0.3)%. The reaction of ozone with 1-propanol in aqueous media follows a second order kinetics with a reaction rate constant of (0.64±0.02)M-1·s-1 atpH = 7 and 23 °C. The dependence of the second order rate constant on temperature is described by the equation: ln kII = (27.17 ± 0.38)-(8180 ± 120) × T-1, which gives the activation energy, Ea = (68 ± 1) kJ mol-1 and pre-exponential factor, A = (6.3 ± 2.4) × 1011 M-1 s-1. The nature of products, their yields and the kinetic data can be used in water treatment. The fact that the hydride transfer is the main pathway in the 1-propanol/ozone system can probably be transferred on other systems in which the substrate is characterized by C-H active sites only. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemRegeneration of TiO 2 Nanotube Arrays after Long-Term Cell and Tissue Culture for Multiple Use - An Environmental Scanning Electron Microscopy (ESEM) Survey of Adult Pig Retina and beyond(New York, NY : Springer, 2019) Friebe, Sabrina; Mayr, Stefan G.Long-term organotypic culture of adult tissues not only open up possibilities for studying complex structures of explants in vitro, but also can be employed e.g. to investigate pathological changes, their fingerprints on tissue mechanics, as well as the effectiveness of drugs. While conventional culture methods do not allow for survival times of more than a few days, we have demonstrated recently that TiO 2 nanotube arrays allow to maintain integrity of numerous tissues, including retina, brain, spline and tonsils, for as long as 2 weeks in vitro. A mystery in culturing has been the interaction of tissue with these substrates, which is also reflected by tissue debris after liftoff. As the latter reveals fingerprints of tissue adhesion and impedes with nanotube array reuse, we address within the present environmental scanning electron study debris nature and the effectiveness of cleaning approaches of distinct physical and chemical methods, including UV-light irradiation, O2 plasma treatment and application of an enzyme-based buffer. This will lays the foundation for large-scale regeneration and reuse of nanotube arrays in science and clinical research. © 2019 The Author(s).
- ItemCorrection: Towards efficient initiators for two-photon induced polymerization: Fine tuning of the donor/acceptor properties (Molecular Systems Design and Engineering (2019) DOI: 10.1039/c8me00101d)(Cambridge : Royal Society of Chemistry, 2019) Holzer, Brigitte; Lunzer, Markus; Rosspeintner, Arnulf; Licari, Giuseppe; Tromayer, Maximilian; Naumov, Sergej; Lumpi, Daniel; Horkel, Ernst; Hametner, Christian; Ovsianikov, Aleksandr; Liska, Robert; Vauthey, Eric; Fröhlich, JohannesThe authors regret that in the published article, affiliations b and c were inadvertently switched. The correct affiliations are shown here. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry 2019.