TY - JOUR A1 - Glatzel, Stefan A1 - Badi, Nezha A1 - Paech, Michael A1 - Laschewsky, André A1 - Lutz, Jean-Francois T1 - Well-defined synthetic polymers with a protein-like gelation behavior in water N2 - Homopolymers of N-acryloyl glycinamide were prepared by reversible addition-fragmentation chain transfer polymerization in water. The formed macromolecules exhibit strong polymer-polymer interactions in aqueous milieu and therefore form thermoreversible physical hydrogels in pure water, physiological buffer or cell medium. Y1 - 2010 UR - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CC U6 - https://doi.org/10.1039/C0cc00038h SN - 1359-7345 ER - TY - THES A1 - Sievers, Torsten T1 - Tuning and understanding chain-length of metallo-supramolecular coordination polymers Y1 - 2010 CY - Potsdam ER - TY - JOUR A1 - Xie, Zai-Lai A1 - Jelicic, Aleksandra A1 - Wang, Feipeng A1 - Rabu, Pierre A1 - Friedrich, Alwin A1 - Beuermann, Sabine A1 - Taubert, Andreas T1 - Transparent, flexible, and paramagnetic ionogels based on PMMA and the iron-based ionic liquid 1-butyl-3- methylimidazolium tetrachloroferrate(III) [Bmim][FeCl4] N2 - The iron-containing ionic liquid (IL) 1-butyl-3-methylimidazolium tetrachloroferrate(III) [Bmim][FeCl4] has been used as a building block in the synthesis of transparent, ion-conducting, and paramagnetic ionogels. UV/Vis spectroscopy shows that the coordination around the Fe(III) ion does slightly change upon incorporation of the IL into PMMA. The thermal stability of the PMMA increases significantly with IL incorporation. In particular, the onset weight loss observed at ca. 265 degrees C for pure PMMA is completely suppressed. The ionic conductivity shows a strong temperature dependence and increases with increasing IL weight fractions. The magnetic properties are similar to those reported for the pure IL and are not affected by the incorporation into the PMMA matrix. The resulting ionogel is thus an interesting prototype for soft, flexible, and transparent materials combining the mechanical properties of the matrix with the functionality of the metal-containing IL, such as magnetism. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/jm/index.asp U6 - https://doi.org/10.1039/C0jm01733g SN - 0959-9428 ER - TY - JOUR A1 - Tremblay, Jean Christophe A1 - Krause, Pascal A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - Time-dependent response of dissipative electron systems N2 - We present a systematic study of the influence of energy and phase relaxation on dynamic polarizability simulations in the linear response regime. The nonperturbative approach is based on explicit electron dynamics using short laser pulses of low intensities. To include environmental effects on the property calculation, we use the time- dependent configuration-interaction method in its reduced density matrix formulation. Both energy dissipation and nonlocal pure dephasing are included. The explicit treatment of time-resolved electron dynamics gives access to the phase shift between the electric field and the induced dipole moment, which can be used to define a useful uncertainty measure for the dynamic polarizability. The nonperturbative treatment is compared to perturbation theory expressions, as applied to a simple model system, the rigid H-2 molecule. It is shown that both approaches are equivalent for low field intensities, but the time-dependent treatment provides complementary information on the phase of the induced dipole moment, which allows for the definition of an uncertainty associated with the computation of the dynamic polarizability in the linear response regime. Y1 - 2010 UR - http://pra.aps.org/ U6 - https://doi.org/10.1103/Physreva.81.063420 SN - 1050-2947 ER - TY - THES A1 - Stöckle, Silke T1 - Thin liquid films with nanoparticles and rod-like ions as models for nanofluidics T1 - Dünne flüssige Filme mit Nanopartikeln und stäbchenförmigen Ionen als Nanofluidische Modelle N2 - With the rise of nanotechnology in the last decade, nanofluidics has been established as a research field and gained increased interest in science and industry. Natural aqueous nanofluidic systems are very complex, there is often a predominance of liquid interfaces or the fluid contains charged or differently shaped colloids. The effects, promoted by these additives, are far from being completely understood and interesting questions arise with regards to the confinement of such complex fluidic systems. A systematic study of nanofluidic processes requires designing suitable experimental model nano – channels with required characteristics. The present work employed thin liquid films (TLFs) as experimental models. They have proven to be useful experimental tools because of their simple geometry, reproducible preparation, and controllable liquid interfaces. The thickness of the channels can be adjusted easily by the concentration of electrolyte in the film forming solution. This way, channel dimensions from 5 – 100 nm are possible, a high flexibility for an experimental system. TLFs have liquid IFs of different charge and properties and they offer the possibility to confine differently shaped ions and molecules to very small spaces, or to subject them to controlled forces. This makes the foam films a unique “device” available to obtain information about fluidic systems in nanometer dimensions. The main goal of this thesis was to study nanofluidic processes using TLFs as models, or tools, and to subtract information about natural systems plus deepen the understanding on physical chemical conditions. The presented work showed that foam films can be used as experimental models to understand the behavior of liquids in nano – sized confinement. In the first part of the thesis, we studied the process of thinning of thin liquid films stabilized with the non – ionic surfactant n – dodecyl – β – maltoside (β – C₁₂G₂) with primary interest in interfacial diffusion processes during the thinning process dependent on surfactant concentration 64. The surfactant concentration in the film forming solutions was varied at constant electrolyte (NaCl) concentration. The velocity of thinning was analyzed combining previously developed theoretical approaches. Qualitative information about the mobility of the surfactant molecules at the film surfaces was obtained. We found that above a certain limiting surfactant concentration the film surfaces were completely immobile and they behaved as non – deformable, which decelerated the thinning process. This follows the predictions for Reynolds flow of liquid between two non – deformable disks. In the second part of the thesis, we designed a TLF nanofluidic system containing rod – like multivalent ions and compared this system to films containing monovalent ions. We presented first results which recognized for the first time the existence of an additional attractive force in the foam films based on the electrostatic interaction between rod – like ions and oppositely charged surfaces. We may speculate that this is an ion bridging component of the disjoining pressure. The results show that for films prepared in presence of spermidine the transformation of the thicker CF to the thinnest NBF is more probable as films prepared with NaCl at similar conditions of electrostatic interaction. This effect is not a result of specific adsorption of any of the ions at the fluid surfaces and it does not lead to any changes in the equilibrium properties of the CF and NBF. Our hypothesis was proven using the trivalent ion Y3+ which does not show ion bridging. The experimental results are compared to theoretical predictions and a quantitative agreement on the system’s energy gain for the change from CF to NBF could be obtained. In the third part of the work, the behavior of nanoparticles in confinement was investigated with respect to their impact on the fluid flow velocity. The particles altered the flow velocity by an unexpected high amount, so that the resulting changes in the dynamic viscosity could not be explained by a realistic change of the fluid viscosity. Only aggregation, flocculation and plug formation can explain the experimental results. The particle systems in the presented thesis had a great impact on the film interfaces due to the stabilizer molecules present in the bulk solution. Finally, the location of the particles with respect to their lateral and vertical arrangement in the film was studied with advanced reflectivity and scattering methods. Neutron Reflectometry studies were performed to investigate the location of nanoparticles in the TLF perpendicular to the IF. For the first time, we study TLFs using grazing incidence small angle X – ray scattering (GISAXS), which is a technique sensitive to the lateral arrangement of particles in confined volumes. This work provides preliminary data on a lateral ordering of particles in the film. N2 - Mit dem Heranwachsen der Nanotechnologie in den vergangenen zehn Jahren hat sich die Nanofluidik als Forschungsbereich etabliert und erfährt wachsende Aufmerksamkeit in der Wissenschaft, sowie auch in der Industrie. Im biomedizinischen Bereich, wo intrazelluläre Prozesse häufig komplexer, nanofluidischer Natur sind, wird sich vermehrt für ein detailliertes Verständnis von nanofluidischen Prozessen interessiert, z.B. für den Einfluss von Kolloiden verschiedenster Form oder elektrischer Ladung auf die Kanäle und auf das Fließverhalten oder die Auswirkungen der Einengung von Flüssigkeiten und Kolloiden in Nanometer Geometrien. In der vorliegenden Arbeit werden dünne flüssige Filme, hinsichtlich ihrer Funktion als nanofluidische Modelle untersucht. Im ersten Teil der Arbeit wurde die Fließgeschwindigkeit des Fluids aus dem dünnen Film, abhängig von der Konzentration der filmstabilisierenden Tensidmoleküle n – Dodecyl β – D – Maltoside ( β – C₁₂G₂) bei einer konstanten Elektrolytkonzentration von 0.2 mM NaCl untersucht. Mit einem theoretischen Modell konnte das Dünnungsverhalten nachgezeichnet werden. Es wurde eine kritische Tensidkonzentration gefunden, unter der die Oberflächen lateral mobil sind und über der sie sich wie fest verhalten. Dadurch konnten wir Aufschluss darüber erlangen, wie die Oberfläche des Films unter verschiedenen Bedingungen geschaffen ist, und das in Bezug zur Verteilungsdichte der Moleküle an den Oberflächen setzen. Im weiteren wurden komplexere, nanofluidische Systeme untersucht, wobei zum einen ~ 1 nm lange, stäbchenförmige, multivalent geladene Spermidin - Moleküle die punktförmigen Elektrolyte ersetzten. Es konnte eine deutliche Veränderung der Stabilität zwischen Filmen mit und ohne Stäbchen festgestellt werden. Die Filme, mit NaCl, blieben länger in dem metastabilen „Common Film“ (CF) Zustand als die Filme, die eine vergleichbare Konzentration von Spermidin Stäbchen beinhalteten. Die Ergebnisse deuteten auf eine zusätzliche Anziehungskraft durch Brückenbildung zwischen zwei geladenen Oberflächen durch gegensätzlich geladene Stäbchenförmige Moleküle hin. Es konnte gezeigt werden, dass dieser Effekt weder ein Ergebnis von spezifischer Ionenadsorption an die Filmoberfläche war, noch ein Unterschied in den Gleichgewichtszuständen von den Dicken der CFs und der Newton Black Films (NBFs) hervorrief, was auf die korrekte Annahme der Ionenstärke in der Lösung schließen ließ. Auch in Versuchen mit ebenfalls trivalenten Ionen YCl3 wurde festgestellt, dass kein vergleichbarer Überbrückungseffekt auftritt. Die Ergebnisse wurden mit theoretischen Simulationen verglichen und es wurde eine quantitative Übereinstimmung gefunden bezüglich der Größe des Systeminternen Energiegewinns durch den Überbrückungseffekt. Desweiteren wurde das Fließverhalten von Fluiden mit Kolloiden eingeengt in Nanometer Geometrien untersucht. Für zwei verschiedene Arten von Nanopartikeln (Fe3O4 stabilisiert mit Oleinsäure und polymerstabilisierte Goldpartikel) wurde eine Verlangsamung der Fließgeschwindigkeit festgestellt. Mit einem theoretischen Modell konnte das Fließverhalten nur für enorm erhöhte Viskositätswerte des Fluids erklärt werden. Die Viskositätserhöhung wurde mit Partikelaggregaten, die den Ausfluss behindern, erklärt und diskutiert, unter der Annahme eines nicht - Newtonischen Fließverhaltens der Dispersionen. Gleichermaßen wurde die strukturelle Anordnung der Partikel in den Filmen hinsichtlich ihrer vertikalen und lateralen Verteilung untersucht. In dieser Arbeit werden vorläufige Ergebnisse präsentiert, die noch weiteren Studien bedürfen. Mit Neutronenreflexion sollte die Anordnung der Partikel orthogonal zur Oberfläche im Film analysiert werden. Eine qualitative Analyse lässt schließen, dass bei einer höheren Konzentration von Partikeln in Lösung, sich auch eine erhöhte Konzentration von Partikeln im dünnen Film befindet. Leider konnten die Daten nicht hinsichtlich der Lage der Partikel analysiert werden. Zum ersten Mal wurden dünne flüssige Filme mit Kleinwinkelröntgenstreuung unter streifendem Einfall (GISAXS) analysiert. Mit Hilfe dieser Methode sollte eine laterale Anordnung der Partikel im Film untersucht werden. Es konnten erfolgreiche Messungen durchgeführt werden und mit Hilfe der rechnergestützten Analyse konnte eine Aussage gemacht werden, dass ~ 6 nm große Teilchen in ~ 43 nm Abstand sich im Film befinden. Die Aussage bezüglich der kleinen Teilchen könnte sich auf einzelne, kleinere Partikel beziehen, allerdings könnten auch die 43 nm eine relevante Strukturgröße darstellen, da es in der Dispersion gehäuft Aggregate mit dem Durchmesser in dem Größenbereich vorliegen. Zusammenfassend können sich mit dieser Arbeit die dünnen flüssigen Filme als eine wichtige Kernmethode der Untersuchung von nanofluidischen Prozessen, wie sie häufig in der Natur vorkommen, behaupten. KW - Nanofluidik KW - Schaumfilme KW - Spermidin KW - Nanopartikel KW - Oberflächenkräfte KW - nanofluidics KW - foam films KW - spermidine KW - nanoparticles KW - interfacial forces Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-46370 ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Kulkarni, Amit A1 - Jain, Abhinav A1 - Wang, Weinan A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Pipich, Vitaliy A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Thermoresponsive PS-b-PNIPAM-b-PS micelles : aggregation behavior, segmental dynamics, and thermal response N2 - We have studied I lie thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylarnicle) (PNIPAM) middle block exhibiting a lower critical solution temperature (LCST) in aqueous solution. A wide range of concentrations (0.1-300 mg/mL) is investigated using it number of analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and neutron spin-echo spectroscopy (NSE). The critical micelle concentration is determined using FCS to be 1 mu M or less. The collapse of the micelles at the LCST is investigated using turbidimetry and DLS and shows a weak dependence on the degree of polymerization of the PNIPAM block. SANS with contrast matching allows its to reveal the core-shell Structure of the micelles as well as their correlation as a function of temperature. The segmental dynamics of the PNIPAM shell are studied as a function of temperature and arc found to be faster in the collapsed state than in the swollen state. The mode detected has a linear dispersion in q(2) and is found to be faster in the collapsed state as compared to the swollen state. We attribute this result to the averaging over mobile and immobilized segments. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma902714p SN - 0024-9297 ER - TY - JOUR A1 - Bivigou Koumba, Achille Mayelle A1 - Goernitz, Eckhard A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Thermoresponsive amphiphilic symmetrical triblock copolymers with a hydrophilic middle block made of poly(N- isopropylacrylamide) : synthesis, self-organization, and hydrogel formation N2 - Several series of symmetrical triblock copolymers were synthesized by the reversible addition fragmentation chain transfer method. They consist of a long block of poly(N-isopropylacrylamide) as hydrophilic, thermoresponsive middle block, which is end-capped by two small strongly hydrophobic blocks made from five different vinyl polymers. The association of the amphiphilic polymers was studied in dilute and concentrated aqueous solution. The polymer micelles found at low concentrations form hydrogels at high concentrations, typically above 30-35 wt.%. Hydrogel formation and the thermosensitive rheological behavior were studied exemplarily for copolymers with hydrophobic blocks of polystyrene, poly(2-ethylhexyl acrylate), and poly(n-octadecyl acrylate). All systems exhibited a cloud point around 30 A degrees C. Heating beyond the cloud point initially favors hydrogel formation but continued heating results in macroscopic phase separation. The rheological behavior suggests that the copolymers associate into flower-like micelles, with only a small share of polymers that bridge the micelles and act as physical cross-linkers, even at high concentrations. Y1 - 2010 UR - http://www.springerlink.com/content/101551 U6 - https://doi.org/10.1007/s00396-009-2179-9 SN - 0303-402X ER - TY - JOUR A1 - Schwarz, Guntram A1 - Sievers, Torsten K. A1 - Bodenthin, Yves A1 - Hasslauer, Ires A1 - Geue, Thomas A1 - Koetz, Joachim A1 - Kurth, Dirk G. T1 - The structure of metallo-supramolecular polyelectrolytes in solution and on surfaces N2 - Metal ion induced self-assembly of the rigid ligand 1,4-bis(2,2':6',2 ''-terpyridine- 4'-yl) benzene (1) with Fe(II), Co(II), Ni(II) and Zn(II) acetate in aqueous solution results in extended, rigid- rod like metallosupramolecular coordination polyelectrolytes (MEPE-1). Under the current experimental conditions the molar masses range from 1000 g mol(-1) up to 500 000 g mol(-1). The molar mass depends on concentration, stoichiometry, metal-ion and time. In addition, we present viscosity measurements, small angle neutron scattering and AFM data. We introduce a protocol to precisely control the stoichiometry during self-assembly using conductometry. The protocol can be used with different terpyridine ligands and the above-mentioned metal ions and is of paramount importance to obtain meaningful and reproducible results. As a control experiment we studied the mononuclear 4'- (phenyl)2,2':6',2 ''-terpyridine (3) complex with Ni(II) and Zn(II) and the flexible ligand 1,3- bis[4'-oxa(2,2': 6',2 ''-terpyridinyl)] propane (2) with Ni(II) acetate (Ni-MEPE-2). This ligand does not form extended macroassemblies but likely ring-like structures with 3 to 4 repeat units. Through spin- coating of Ni-MEPE-1 on a solid surface we can image the MEPEs in real space by AFM. SANS measurements of Fe-MEPE-1 verify the extended rigid-rod type structure of the MEPEs in aqueous solution. Y1 - 2010 UR - http://pubs.rsc.org/en/content/articlehtml/2010/jm/b926783b U6 - https://doi.org/10.1039/B926783b SN - 0959-9428 ER - TY - JOUR A1 - Schmidt, Bernd A1 - Werner, Frank A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - The reaction of 3,4-dihydro-2H-pyran with oxalyl chloride : formation and crystal structure analysis of an unexpected bicyclic product N2 - 3,4-Dihydro-2-H-pyran and oxalyl chloride react, depending on the conditions, to keto esters, a pyran-3- carboxylic acid or derivatives thereof, or to an hitherto unknown bicyclic acetal containing a vinyl chloride moiety. The structure of the latter product has been unambiguously elucidated by single-crystal X-ray structure analysis. A mechanism for its formation is proposed. Y1 - 2010 UR - 1960 = dx.doi.org/10.1002/jhet.456 SN - 0022-152X ER - TY - JOUR A1 - Strehmel, Veronika A1 - Rexhausen, Hans A1 - Strauch, Peter A1 - Strehmer, Bernd T1 - Temperature dependence of interactions between stable piperidine-1-yloxyl derivatives and a semicrystalline ionic liquid N2 - The stable 2,2,6,6-tetramethylpiperidine-1-yloxyl and its derivatives with hydrogen-bond-forming (-OH, -OSO3H), anionic (-OSO3- bearing K+ or [K(18-crown-6)](+) as counter ion), or cationic (-N+-(CH3)(3) bearing I-, BF4-, PF6- or N- (SO2CF3)(2) as counter ion) substituents are investigated in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide over a wide temperature range. The temperature dependence of the viscosity of the ionic liquid is well described by the Vogel-Fulcher-Tammann equation. Interestingly, the temperature dependence of the rotational correlation time of the spin probes substituted with either a hydrogen-bond-forming group or an ionic substituent can be described using the Stokes-Einstein equation. In contrast, the temperature dependence of the rotational correlation time of the spin probe without an additional substituent at the 4-position to the nitroxyl group does not follow this trend. The activation energy for the mobility of the unsubstituted spin probe, determined from an Arrhenius plot of the spin-probe mobility in the ionic liquid above the melting temperature, is comparable with the activation energy for the viscous flow of the ionic liquid, but is higher for spin probes bearing an additional substituent at the 4-position. Quantum chemical calculations of the spin probes using the 6-31G+d method give information about the rotational volume of the spin probes and the spin density at the nitrogen atom of the radical structure as a function of the substituent at the spin probes in the presence and absence of a counter ion. The results of these calculations help in understanding the effect of the additional substituent on the experimentally determined isotropic hyperfine coupling constant. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/72514732/ U6 - https://doi.org/10.1002/cphc.200900977 SN - 1439-4235 ER - TY - THES A1 - Kleineidam, Anja Melanie T1 - Sythese und Verhalten von abbaubaren Fluortensiden Y1 - 2010 CY - Potsdam ER - TY - JOUR A1 - Schwarze, Thomas A1 - Mickler, Wulfhard A1 - Dosche, Carsten A1 - Flehr, Roman A1 - Klamroth, Tillmann A1 - Löhmannsröben, Hans-Gerd A1 - Saalfrank, Peter A1 - Holdt, Hans-Jürgen T1 - Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination N2 - Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorophore probes 1-13 consist of a fluorophore group, in alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed, dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second. fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (E-Ox) through electron-withdrawing or -donating groups on the anthracene moiety regulates file thermodynamic driving force for oxidative PET (Delta G(PET)) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (Phi(f)), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized. Y1 - 2010 UR - http://onlinelibrary.wiley.com/doi/10.1002/chem.200902281/pdf U6 - https://doi.org/10.1002/chem.200902281 SN - 0947-6539 ER - TY - JOUR A1 - Schwarze, Thomas A1 - Mickler, Wulfhard A1 - Dosche, Carsten A1 - Flehr, Roman A1 - Klamroth, Tillmann A1 - Löhmannsröben, Hans-Gerd A1 - Saalfrank, Peter A1 - Holdt, Hans-Jürgen T1 - Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination N2 - Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorescent probes 1-13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed a dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second, fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (EOx) through electron-withdrawing or -donating groups on the anthracene moiety regulates the thermodynamic driving force for oxidative PET (GPET) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (f), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized. Y1 - 2010 UR - http://www3.interscience.wiley.com/journal/26293/home SN - 0947-6539 ER - TY - JOUR A1 - Skrabania, Katja A1 - von Berlepsch, Hans A1 - Böttcher, Christoph A1 - Laschewsky, André T1 - Synthesis of ternary, hydrophilic-lipophilic-fluorophilic block copolymers by consecutive RAFT polymerizations and their self-assembly into multicompartment micelles N2 - Linear amphiphilic diblock and ternary triblock copolymers were synthesized by the RAFT method in three Successive Steps, using oligo(ethylene oxide) monomethyl ether acrylate, butyl or 2-ethylhexyl acrylate, and 1H, 1H, 2H, 2H-perfluorodecyl acrylate. The diblock and the triblock copolymers, which consist of a hydrophilic, a lipophilic, and a fluorophilic block, self-assemble in water into spherical micellar aggregates. Imaging by cryogenic transmission electron microscopy (cryo-TEM) revealed that the cores of the micellar aggregates made from these "triphilic" copolymers undergo local phase separation to form various ultrastructures, which depend sensitivity on the given block sequence. While the sequence hydrophilic-lipophilic-fluorophilic resulted in multicompartment cores with core-shell-corona morphology, the sequence lipophilic-hydrophilic-fluorophilic provided new "patched double micelle" and larger "soccer ball" structures. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma901913f SN - 0024-9297 ER - TY - THES A1 - Chanana, Munish T1 - Synthesis of stimuli-responsive and switchable inorganic nanoparticles for biomedical applications Y1 - 2010 CY - Potsdam ER - TY - JOUR A1 - Senge, Mathias O. A1 - Shaker, Yasser M. A1 - Pintea, Monica A1 - Ryppa, Claudia A1 - Hatscher, Sabine S. A1 - Ryan, Aoife A1 - Sergeeva, Yulia T1 - Synthesis of meso-substituted ABCD-Type porphyrins by functionalization reactions N2 - Considerable progress has been made in recent years in the search for synthetic methods leading to functionalized porphyrins, especially for modification of either the beta- or meso positions. For the latter, total synthesis based on condensation methods or partial synthesis through functionalization of preformed porphyrin have emerged as possible methods. The increasing number of possible technical and medicinal applications for unsymmetrically meso-substituted porphyrins requires straightforward methods for the preparation of the so-called ABCD-porphyrins, i.e., porphyrins with up to four different meso substituents. Here, we describe new strategies for the synthesis of ABCD-type porphyrins based on porphyrin reactions with organolithium reagents and the use of Pd-catalyzed coupling reactions. With the whole repertoire of contemporary functionalization methods, a comprehensive analysis and comparison of the various strategies for A-, AB-, A(2)B-, ABC-, A(2)BC- and ABCD-type porphyrins is given. In addition, we report on the synthesis of new functionalized derivatives for some of these porphyrin classes. In practical terms and taking an applied-science- oriented approach, the synthesis of unsymmetrically meso-substituted porphyrins is best accomplished by a combination of well-developed condensation methods with subsequent functionalization. by organolithium compounds or transition-metal- catalyzed coupling protocols. The methods described are suitable for the preparation of porphyrins for many divergent applications ranging over amphiphilic porphyrins for photodynamic therapy, push-pull systems for optical applications and chiral systems useful in catalysis to donor-acceptor systems suitable for electron-transfer studies. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/27380/ U6 - https://doi.org/10.1002/ejoc.200901113 SN - 1434-193X ER - TY - JOUR A1 - Cywinski, Piotr J. A1 - Idzik, Krzysztof R. A1 - Cranfield, Charles G. A1 - Beckert, Rainer A1 - Mohr, Gerhard J. T1 - Synthesis and sensing properties of a new carbazole fluorosensor for detection of abacavir N2 - An abacavir-targeted fluorosensor based on the carbazole moiety has been synthesised and characterised. Recognition of abacavir is by base pairing between a uracil moiety present in the fluorosensor and the guanine moiety of abacavir. The fluorosensor exhibits five-fold quenching in the presence of 50M abacavir. Its sensitivity to abacavir is superior to that of other reverse transcriptase inhibitors: zidovudine, lamivudine and didanosine. Due to its high sensitivity, this fluorosensor has the potential to be used in multi-analyte array-based detection platforms as well as in microfluidics systems. Y1 - 2010 UR - http://www.informaworld.com/openurl?genre=journal&issn=1061-0278 U6 - https://doi.org/10.1080/10610278.2010.506541 SN - 1061-0278 ER - TY - THES A1 - Thesen, Manuel Wolfram T1 - Synthese und Charakterisierung von phosphoreszenten Terpolymeren und nichtkonjugierten Matrixpolymeren für effiziente polymere Leuchtdioden T1 - Synthesis and characterization of phosphoreszent terpolymers and nonconjugated matrixpolymers for efficient polymer light emitting diodes N2 - Mit Seitenkettenpolystyrenen wurde ein neues Synthesekonzept für phosphoreszente polymere LED-Materialien aufgestellt und experimentell verifiziert. Zunächst erfolgten auf Grundlage strukturell einfacher Verbindungen Untersuchungen zum Einfluss von Spacern zwischen aktiven Seitengruppen und dem Polystyrenrückgrat. Es wurden Synthesemethoden für die Monomere etabliert, durch die aktive Elemente - Elektronen- und Lochleiter - mit und ohne diesen Spacer zugänglich sind. Durch Kombination dieser Monomere waren unter Hinzunahme von polymerisierbaren Iridium-Komplexen in unterschiedlicher Emissionswellenlänge statistische Terpolymere darstellbar. Es wurde gezeigt, dass die Realisierung bestimmter Verhältnisse zwischen Loch-, Elektronenleiter und Triplettemitter in ausreichender Molmasse möglich ist. Die Glasstufen der Polymere zeigten eine deutliche Strukturabhängigkeit. Auf die Lage der Grenzorbitale übten die Spacer nahezu keinen Einfluss aus. Die unterschiedlichen Makromoleküle kamen in polymeren Licht emittierenden Dioden (PLEDs) zum Einsatz, wobei ein deutlicher Einfluss der Spacereinheiten auf die Leistungscharakteristik der PLEDs festzustellen war: Sowohl Effizienz, Leuchtdichte wie auch Stromdichte waren durch den Einsatz der kompakten Makromoleküle ohne Spacer deutlich höher. Diese Beobachtungen begründeten sich hauptsächlich in der Verwendung der aliphatischen Spacer, die den Anteil im Polymer erhöhten, der keine Konjugation und damit elektrisch isolierende Eigenschaften besaß. Diese Schlussfolgerungen waren mit allen drei realisierten Emissionsfarben grün, rot und blau verifizierbar. Die besten Messergebnisse erzielte eine PLED aus einem grün emittierenden und spacerlosen Terpolymer mit einer Stromeffizienz von etwa 28 cd A-1 (bei 6 V) und einer Leuchtdichte von 3200 cd m-2 (bei 8 V). Ausgehend von obigen Ergebnissen konnten neue Matrixmaterialien aus dem Bereich verdampfbarer Moleküle geringer Molmasse in das Polystyrenseitenkettenkonzept integriert werden. Es wurden Strukturvariationen sowohl von loch- wie auch von elektronenleitenden Verbindungen als Homopolymere dargestellt und als molekular dotierte Systeme in PLEDs untersucht. Sieben verschiedene lochleitende Polymere mit Triarylamin-Grundkörper und drei elektronendefizitäre Polymere auf der Basis von Phenylbenzimidazol konnten erfolgreich in den Polymeransatz integriert werden. Spektroskopische und elektrochemische Untersuchungen zeigten kaum eine Veränderung der Charakteristika zwischen verdampfbaren Molekülen und den dargestellten Makromolekülen. Diese ladungstransportierenden Makro-moleküle wurden als polymere Matrizes molekular dotiert und lösungsbasiert zu Einschicht-PLEDs verarbeitet. Als aussichtsreichstes Lochleiterpolymer dieser Reihe, mit einer Strom-effizenz von etwa 33 cd A-1 (bei 8 V) und einer Leuchtdichte von 6700 cd m-2 (bei 10 V), stellte sich ein Triarylaminderivat mit Carbazolsubstituenten heraus. Als geeignetstes Matrixmaterial für die Elektronenleitung wurde ein meta-verknüpftes Di-Phenylbenzimidazol ausfindig gemacht, das in der PLED eine Stromeffizienz von etwa 20 cd A-1 (bei 8 V) und eine Leuchtdichte von 7100 cd m-2 (bei 10 V) erzielte. Anschließend wurden die geeignetsten Monomere zu Copolymeren kombiniert: Die lochleitende Einheit bildete ein carbazolylsubstituiertes Triarylamin und die elektronen-leitende Einheit war ein disubstituiertes Phenylbenzimidazol. Dieses Copolymer diente im Folgenden dazu, PLEDs zu realisieren und die Leistungsdaten mit denen eines Homopolymer-blends zu vergleichen, wobei der Blend die bessere Leistungscharakteristik zeigte. Mit dem Homopolymerblend waren Bauteileffizienzen von annähernd 30 cd A-1 (bei 10 V) und Leuchtdichten von 6800 cd m-2 neben einer Verringerung der Einsatzspannung realisierbar. Für die abschließende Darstellung bipolarer Blockcopolymere wurde auf die Nitroxid-vermittelte Polymerisation zurückgegriffen. Mit dieser Technik waren kontrollierte radikalische Polymersiationen mit ausgewählten Monomeren in unterschiedlichen Block-längen durchführbar. Diese Blockcopolymere kamen als molekular dotierte Matrizes in phosphoreszenten grün emittierenden PLEDs zum Einsatz. Die Bauteile wurden sowohl mit statistischen Copolymeren, wie auch mit Homopolymerblends in gleicher Zusammensetzung aber unterschiedlichem Polymerisationsgrad hinsichtlich der Leistungscharakteristik verglichen. Kernaussage dieser Untersuchungen ist, dass hochmolekulare Systeme eine bessere Leistungscharakteristik aufweisen als niedermolekulare Matrizes. Über Rasterkraft-mikroskopie konnte eine Phasenseparation in einem Größenbereich von etwa 10 nm für den hochmolekularen Homopolymerblend nachgewiesen werden. Für die Blockcopolymere war es nicht möglich eine Phasenseparation zu beobachten, was vorwiegend auf deren zu geringe Blocklänge zurückgeführt wurde. N2 - A new synthetic approach for the synthesis of side chain polystyrenes was established and their use as phosphorescent polymers for polymer light emitting diodes (PLEDs) is shown by experiments. An assay was introduced to clarify influences on electroluminescent behavior for RGB-colored phosphorescent terpolymers with N,N-Di-p-tolyl-aniline as hole-transporting unit, 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tert-BuPBD) as electron-transporting unit, and different iridium complexes in RGB-colors as triplet emitting materials. All monomers were attached with spacer moieties to the “para” position of a polystyrene. PLEDs were built to study the electro-optical behavior of these materials. The gist was a remarkable influence of hexyl-spacer units to the PLED performance. For all three colors only very restricted PLED performances were found. In comparison RGB-terpolymers were synthesized with directly attached charge transport materials to the polymer backbone. For this directly linked systems efficiencies were 28 cd A−1 @ 6 V (green), 4.9 cd A−1 @ 5 V (red) and 4.3 cd A−1 @ 6 V (bluish). In summary it is assumed that an improved charge percolation pathways regarding to the higher content of semiconducting molecules and an improved charge transfer to the phosphorescent dopand in the case of the copolymers without spacers are responsible for the better device performance comparing the copolymers with hexyl spacers. It was found that the approach of the directly connected charge transport materials at the nonconjugated styrene polymer backbone is favored for further investigations as shown in the following. A series of styrene derived monomers with triphenylamine-based units, and their polymers have been synthesized and compared with the well-known structure of polymer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine with respect to their hole-transporting behavior in PLEDs. A vinyltriphenylamine structure was selected as a basic unit, functionalized at the para positions with the following side groups: diphenylamine, 3-methylphenyl-aniline, 1- and 2-naphthylamine, carbazole, and phenothiazine. The polymers are used in PLEDs as host polymers for blend systems. It is demonstrated that two polymers are excellent hole-transporting matrix materials for these blend systems because of their good overall electroluminescent performances and their comparatively high glass transition temperatures. For the carbazole-substituted polymer (Tg = 246 °C), a luminous efficiency of 35 cd A−1 and a brightness of 6700 cd m−2 at 10 V is accessible. The phenothiazine-functionalized polymer (Tg = 220 °C) shows nearly the same outstanding PLED behavior. Hence, both these polymers outperform the well-known polymer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine, showing only a luminous efficiency of 7.9 cd A−1 and a brightness of 2500 cd m−2 (10 V). Furthermore, novel styrene functionalized monomers with phenylbenzo[d]imidazole units and the corresponding homopolymers are prepared. The macromolecules are used as matrices for phosphorescent dopants to prepare PLEDs. The devices exhibit current efficiencies up to 38.5 cd A−1 at 100 cd m−2 and maximum luminances of 7400 cd m−2 at 10 V. Afterwards the most efficient monomers of this investigations were combined and statistical copolymers were synthesized. As hole-transporting monomer the carbazole substituted triarylamine and as electron-transporting monomer a disubstituted phenylbenzoimidazole was selected. This statistical copolymer was used in the following as matrix material for phosporescent PLEDs and the device performance was compared with a matrix system of a polymer blend matrix system of corresponding homopolymers. With this homopolymer blend efficiencies of about 30 cd A-1 at 10 V and luminances of 6800 cd m-2 beside a decreased onset voltage were realized. Finally bipolar blockcopolymers of structural basic monomers were synthesized via nitroxide mediated polymerization. With these technique and the chosen hole- and electron-transporting monomers a controlled radical polymerization was realized leading to blockcopolymers in different block lengths. These blockcopolymers were used as molecular doped matrix systems in green phosphoreszent PLEDs. The devices were compared in regard to their performances with PLEDs made of statistical copolymers and homopolymer blends. It was found that high molecular systems show a better device performance compared to low molecular polymer matrices. With atomic force microscopy it is shown that a phase separation takes place for the high molecular blend of homopolymers. For the synthesized blockcopolymers no phase separation could be verified, mainly because of the comparatively low molecular weight of these systems. KW - phosphoreszente Terpolymere KW - Elektrolumineszenz KW - organische Licht emittierende Diode KW - Ladungstransport KW - bipolare Blockcopolymere KW - phosphorescent Terpolymers KW - electroluminsecence KW - organic light emitting diode KW - charge transport KW - bipolar blockcopolymers Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-51709 ER - TY - JOUR A1 - Wang, Weijia A1 - Kaune, Gunar A1 - Perlich, Jan A1 - Paradakis, Christine M. A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Schlage, K. A1 - Röhlsberger, Ralf A1 - Roth, Stephan V. A1 - Cubitt, Robert A1 - Müller-Buschbaum, Peter T1 - Swelling and switching kinetics of gold coated end-capped poly(N-isopropylacrylamide) thin films N2 - Thin thermoresponsive hydrogel films of poly(N-isopropylacrylamide) end-capped with n-butyltrithiocarbonate(nbc- PNIPAM) oil si I icon supports with a gold layer on top, causing an asymmetric confinement, are investigated. For two different gold layer thicknesses (nominally 0.4 and 5 rim), the swelling and switching kinetics are probed with in situ neutron reflectivity. With a temperature jump from 23 to 40 degrees C the film is switched from a swollen into a collapsed state. For the thin gold layer this switching is faster as compared to the thick gold layer. The switching is a two-step process of water release and a subsequent structural relaxation. fit swelling and deswelling cycles, aging of the films is probed. After five cycles, the film exhibits enhanced water storage capacity. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that these gold coated nbc-PNIPAM films do not age with respect to the inner structure but slightly roughen at the gold surface. As revealed by atomic force microscopy, the morphology of the gold layer is changed by the water uptake and release. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma902637a SN - 0024-9297 ER - TY - THES A1 - Zhao, Li T1 - Sustainable approaches towards novel nitrogen-doped carbonaceous structures Y1 - 2010 CY - Potsdam ER - TY - JOUR A1 - Schweizer, S. A1 - Schuster, T. A1 - Junginger, Matthias A1 - Siekmeyer, Gerd A1 - Taubert, Andreas T1 - Surface modification of ickel/Titanium Alloy and Titanium Surfaces via a Polyelectrolyte Multilayer/Calcium Phosphate Hybrid Coating N2 - The report shows that simple LbL deposition of positively charged chitosan and negatively charged heparin can be used to efficiently modify the native surface of both NiTi and Ti without any previous treatments. Moreover, mineralization of the polymer multilayers with calcium phosphate leads to surfaces with low contact angles around 70 and 20 degrees for NiTi and Ti, respectively. This suggests that a polymer multilayer/calcium phosphate hybrid coating could be useful for making NiTi or Ti implants that are at the same time antibacterial (via the chitosan), suppress blood clot formation (via the heparin), and favor fast endothelialization (via the improved surface hydrophilicity compared to the respective neat material). Y1 - 2010 UR - http://onlinelibrary.wiley.com/doi/10.1002/mame.200900347/pdf U6 - https://doi.org/10.1002/mame.200900347 SN - 1438-7492 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Boelke, Ute A1 - Koch, Andreas T1 - Subtle Trade-off Existing between (Anti)Aromaticity, Push-Pull Interaction, Keto-Enol Tautomerism, and Steric Hindrance When Defining the Electronic Properties of Conjugated Structures Y1 - 2010 SN - 1089-5639 ER - TY - JOUR A1 - Fokou, Patrice A. A1 - Meier, Michael A. R. T1 - Studying and suppressing olefin isomerization side reactions during ADMET polymerizations N2 - Olefin isomerization side reactions that occur during ADMET polymerizations were studied by preparing polyesters via ADMET and subsequently degrading these polyesters via transesterification with methanol. The resulting diesters, representing the repeating units of the previously prepared polyesters, were then analyzed by GC-MS. This strategy allowed quantification of the amount of olefin isomerization that took place during ADMET polymerization with second generation ruthenium metathesis catalysts. In a second step, it was shown that the addition of benzoquinone to the polymerization mixture prevented the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts may now be used for the preparation of well-defined polymers via ADMET with very little isomerization, which was not possible before. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/10003270 U6 - https://doi.org/10.1002/marc.200900678 SN - 1022-1336 ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Klaumuenzer, Ute A1 - Markovic, Rade A1 - Kleinpeter, Erich T1 - Structure, configuration, conformation and quantification of the push pull-effect of 2-alkylidene-4- thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives N2 - Structures of a series of push-pull 2-alkylidene-4-thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives were optimized at the B3LYP/6-31G(d) level of theory in the gas phase and discussed with respect to configurational and conformational stability. Employing the GIAO method, C-13 NMR chemical shifts of the C-2, C-2', C-4 and C-5 atoms were calculated at the same level of theory in the gas phase and with inclusion of solvent, and compared with experimental data. Push-pull effect of all compounds was quantified by means of the quotient pi*/pi, length of the partial double bond, C-13 NMR chemical shift difference (Delta delta(C=C)) and H-1 NMR chemical shifts of olefinic protons. The effect of bromine on donating and accepting ability of other substituents of the push- pull C=C double bond is discussed, too. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2010.09.040 SN - 0040-4020 ER - TY - JOUR A1 - Schwarz, Guntram A1 - Bodenthin, Yves A1 - Geue, Thomas A1 - Koetz, Joachim A1 - Kurth, Dirk G. T1 - Structure and properties of dynamic rigid rod-like metallo-supramolecular polyelectrolytes in solution N2 - Metal-ion-induced self-assembly in aqueous solution of the rigid ligand 1,4-bis(2,2':6',2 ''-terpyridine-4'-yl)benzene (1) with Fe(OAc)(2) and Ni(OAc)(2) is investigated with viscosimetry, SANS, and AFM. Ligand 1 forms extended, rigid-rod like metallo-supramolecular coordination polyeectrolytes (MEPEs) with a molar mass of up to 200 000 g mol(-1) under the Current experimental conditions. The molar mass depends oil concentration, stoichiometry, and time. By spin-coating MEPEs oil a solid surface, we call image the MEPEs in real space by AFM. Both AFM and SANS confirm the extended rigid-rod-type structure of the MEPEs. As a control experiment, we also studied the flexible ligand 1,3-bis[4'-oxa(2,2':6',2 ''-terpyridinyl)]propane (2). Ligand 2 does not form extended macro-assemblies but likely ringlike structures with three 10 four repeat units. Finally, we present it protocol to control the stoichiometry during self-assembly using conductometry, which is of paramount importance to obtain meaningful and reproducible results. Y1 - 2010 UR - http://pubs.acs.org/doi/full/10.1021/ma902057f U6 - https://doi.org/10.1021/Ma902057f SN - 0024-9297 ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Parvulescu, Vasile A1 - Parvulescu, Victoria A1 - Cotoi, Elena A1 - Gessner, Andre A1 - Kumke, Michael Uwe A1 - Simon, Simion A1 - Vasiliu, Florin T1 - Structural and photoluminescence characterization of mesoporous silicon-phosphates N2 - Two different types of mesoporous silicon-phosphate supports using different surfactants (a mixture of (CH3)(3)C13H27NBr with an organophosphorus coupling molecule (HO-PO(i-C3H7)(2)) and with a co-surfactant ((C2H5)(3)(C6H5)PCl), respectively) were synthesized. Trivalent europium (Eu) ions were immobilized via ion-exchange on these supports. The resulting materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, SEM, TEM, FT-IR, PXRD, CP/MAS. (HSi)-H-1-Si-29 and P-31 NMR, DR-UV-vis as well as steady- state and time-resolved photoluminescence spectroscopy. The results evidenced that the co-polymerization of silicon and phosphorous yielded a unique morphology in these materials. Following calcination at 450 and 900 degrees C europium- exchanged silicon-phosphates with great surface area (BET=600-705 m(2) g(-1)) and 3.4 nm sized mesopores were obtained. The differences among the optical properties of the non-calcined europium materials such as the emission lifetimes, local environment at the europium sites or the relative contribution of the upper excited levels to the total photoluminescence were assigned to the surfactants used in the synthesis. Calcination of the silicon-phosphates at higher temperatures than 450 degrees C did not induce major changes in the structural properties: in contrast, photoluminescence properties of europium were markedly improved in terms of intensity and average lifetime. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/10106030 U6 - https://doi.org/10.1016/j.jphotochem.2010.07.015 SN - 1010-6030 ER - TY - JOUR A1 - Bouakline, Foudhil A1 - Althorpe, Stuart C. A1 - Larregaray, Pascal A1 - Bonnet, Laurent T1 - Strong geometric-phase effects in the hydrogen-exchange reaction at high collision energies : II. quasiclassical trajectory analysis N2 - Recent calculations on the hydrogen-exchange reaction [Bouakline et al., J. Chem. Phys. 128, 124322 (2008)], have found strong geometric phase (GP) effects in the state-to-state differential cross-sections (DCS), at energies above the energetic minimum of the conical intersection (CI) seam, which cancel out in the integral cross-sections (ICS). In this article, we explain the origin of this cancellation and make other predictions about the nature of the reaction mechanisms at these high energies by carrying out quasiclassical trajectory (QCT) calculations. Detailed comparisons are made with the quantum results by splitting the quantum and the QCT cross-sections into contributions from reaction paths that wind in different senses around the CI and that scatter the products in the nearside and farside directions. Reaction paths that traverse one transition state (1-TS) scatter their products in just the nearside direction, whereas paths that traverse two transition states (2-TS) scatter in both the nearside and farside directions. However, the nearside 2-TS products scatter into a different region of angular phase-space than the 1-TS products, which explains why the GP effects cancel out in the ICS. Analysis of the QCT results also suggests that two separate reaction mechanisms may be responsible for the 2-TS scattering at high energies. Y1 - 2010 UR - http://www.informaworld.com/openurl?genre=journal&issn=0026-8976 U6 - https://doi.org/10.1080/00268971003610218 SN - 0026-8976 ER - TY - JOUR A1 - Füchsel, Gernot A1 - Klamroth, Tillmann A1 - Tremblay, Jean Christophe A1 - Saalfrank, Peter T1 - Stochastic approach to laser-induced ultrafast dynamics : the desorption of H-2/D-2 from Ru(0001) N2 - The desorption of molecular hydrogen and deuterium induced by femtosecond-laser pulses is studied theoretically for the so-called DIMET (Desorption Induced by Multiple Electronic Transitions) process. These investigations are based on nonadiabatic classical Monte Carlo trajectory (CMCT) simulations on a ground and an excited state potential energy surface, including up to all six adsorbate degrees of freedom. The focus is on the hot-electron mediated energy transfer from the surface to the molecule and back, and the energy partitioning between the different degrees of freedom of the desorbing molecules. We first validate for a two-mode model comprising the desorption mode and the internal vibrational coordinate, the classical Monte Carlo trajectory method by comparing with Monte Carlo wavepacket (MCWP) calculations arising from a fully quantum mechanical open-system density matrix treatment. We then proceed by extending the CMCT calculations to include all six nuclear degrees of freedom of the desorbing molecule. This allows for a detailed comparison between theory and experiment concerning isotope effects, energy partitioning (translational, vibrational, and rotational energies and their distributions), and the dependence of these properties on the laser fluence. The most important findings are as follows. (i) CMCT agrees qualitative with the MCWP scheme. (ii) The basic experimental features such as the large isotope effect, the non-linear increase of yield with laser fluence, translationally hot products (in the order of several 1000 K) and non-equipartitioning of translational and internal energies (E-trans > E- vib > E-rot) are well reproduced. (iii) Predictions concerning a strong angular dependence of translational energies at large observation angles are also made. Y1 - 2010 UR - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CP U6 - https://doi.org/10.1039/C0cp00895h SN - 1463-9076 ER - TY - JOUR A1 - Kramer, Markus A1 - Kleinpeter, Erich T1 - STD-DOSY : a new NMR method to analyze multi-component enzyme/substrate systems N2 - A new approach to analyze multi-component Saturation Transfer Difference (STD) NMR spectra by combining the STD and the DOSY experiment is proposed. The resulting pulse sequence was successfully used to simplify an exemplary multi- component protein/substrate system by means of standard DOSY processing methods. Furthermore, the same experiment could be applied to calculate the ratio of saturated substrate molecules and its saturation rate in the case of competitive interactions. This ratio depends on the strength of this interaction between the substrates and the protein, so that this kind of information could be extracted from the results of our experiment. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/10907807 U6 - https://doi.org/10.1016/j.jmr.2009.11.007 SN - 1090-7807 ER - TY - JOUR A1 - Starke, Ines A1 - Kammer, Stefan A1 - Holdt, Hans-Jürgen A1 - Kleinpeter, Erich T1 - Stability of disubstituted copper complexes in the gas phase analyzed by electrospray ionization mass spectrometry N2 - A series of nitrogen ligand (L)/copper complexes of the type [(CuL)-L-I](+), [(CuL)-L-II(X)](+) and [(CuL2)-L- I](+) (X = Cl-, BF4-, acac(-), CH3COO- and SO3CF3-) was studied in the gas phase by electrospray ionization mass spectrometry. The following ligands (L) were employed: 1,12-diazaperylene (dap), 1,1'-bisiso-quinoline (bis), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 2,11-disubstituted 1,12-diazaperylenes (dap), 3,3'- disubstituted 1,1'-bisisoquinoline (bis), 5,8-dimethoxy-substituted diazaperylene (meodap), 6,6'-dimethoxy- substituted bisisoquinoline (meobis) and 2,9-dimethyl-1,10-phenanthroline (dmphen). Collision-induced decomposition measurements were applied to evaluate the relative stabilities of the different copper complexes. The influence of the spatial arrangement of the ligands, of the type of substituents and of the counter ion of the copper salts employed for the complexation was examined. Correlations were found between the binding constants of the [ML2](+) complexes in solution and the relative stabilities of the analogous complexes in the gas phase. Furthermore, complexation with the ligands 2,11-dialkylated 1,12-diazaperylenes [alkyl = ethyl (dedap) and isopropyl (dipdap)] was studied in the solvents CH3OH and CH3CN. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/4849 U6 - https://doi.org/10.1002/Rcm.4519 SN - 0951-4198 ER - TY - JOUR A1 - Wischerhoff, Erik A1 - Badi, Nezha A1 - Lutz, Jean-Francois A1 - Laschewsky, André T1 - Smart bioactive surfaces N2 - The purpose of this highlight is to define the emerging field of bioactive surfaces. In recent years, various types of synthetic materials capable of "communicating'' with biological objects such as nucleic acids, proteins, polysaccharides, viruses, bacteria or living cells have been described in the literature. This novel area of research certainly goes beyond the traditional field of smart materials and includes different types of sophisticated interactions with biological entities, such as reversible adhesion, conformational control, biologically-triggered release and selective permeation. These novel materials may be 2D planar surfaces as well as colloidal objects or 3D scaffolds. Overall, they show great promise for numerous applications in biosciences and biotechnology. For instance, practical applications of bioactive surfaces in the fields of bioseparation, cell engineering, biochips and stem-cell differentiation are briefly discussed herein. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/sm/index.asp U6 - https://doi.org/10.1039/B913594d SN - 1744-683X ER - TY - JOUR A1 - Witzel, Franziska A1 - Goetze, Jan A1 - Ebenhoeh, Oliver T1 - Slow deactivation of ribulose 1,5-bisphosphate carboxylase/oxygenase elucidated by mathematical models N2 - Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is the key enzyme of the Calvin cycle, catalyzing the fixation of inorganic carbon dioxide to organic sugars. Unlike most enzymes, RuBisCO is extremely slow, substrate unspecific, and catalyzes undesired side-reactions, which are considered to be responsible for the slow deactivation observed in vitro, a phenomenon known as fallover. Despite the fact that amino acid sequences and the 3D structures of RuBisCO from a variety of species are known, the precise molecular mechanisms for the various side reactions are still unclear. In the present study, we investigate the kinetic properties of RuBisCO using mathematical models. Initially, we formulate a minimal model that quantitatively reflects the kinetic behavior of RuBisCOs from different organisms. By relating rate parameters for single molecular steps to experimentally determined K-m and V-max values, we can examine mechanistic differences among species. The minimal model further demonstrates that two inhibitor producing side reactions are sufficient to describe experimentally determined fallover kinetics. To explain the observed kinetics of the limited capacity of RuBisCO to accept xylulose 1,5-bisphosphate as substrate, the inclusion of other side reactions is necessary. Our model results suggest a yet undescribed alternative enolization mechanism that is supported by the molecular structure. Taken together, the presented models serve as a theoretical framework to explain a wide range of observed kinetic properties of RuBisCOs derived from a variety of species. Thus, we can support hypotheses about molecular mechanisms and can systematically compare enzymes from different origins. Y1 - 2010 UR - http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1742-4658 U6 - https://doi.org/10.1111/j.1742-4658.2009.07541.x SN - 1742-464X ER - TY - JOUR A1 - Bramborg, Andrea A1 - Linker, Torsten T1 - Selective synthesis of 1,4-dialkylbenzenes from terephthalic acid N2 - Terephthalic acid reacts with alkyl halides under Birch conditions to substituted 1,4-cyclohexadienes in high yields and good stereoselectivities. Electrophiles containing ester or nitrile groups undergo a surprising fragmentation under the reaction conditions. Subsequent treatment with chlorosulfonic acid proceeds by an interesting tandem decarbonylation/decarboxylation, affording 1,4-dialkylbenzenes in excellent regioselectivity. Thus our new method is superior to classical Friedel-Crafts alkylations. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/77002176 U6 - https://doi.org/10.1002/adsc.201000322 SN - 1615-4150 ER - TY - JOUR A1 - Strehmel, Veronika A1 - Lungwitz, Ralf A1 - Rexhausen, Hans A1 - Spange, Stefan T1 - Relationship between hyperfine coupling constants of spin probes and empirical polarity parameters of some ionic liquids N2 - The polarity of 1-alkyl-3-methylimidazolium-based ionic liquids containing hexafluorophosphate, tetrafluoroborate, dicyanoimide, or bis(trifluoromethanesulfonyl) imide as anions and a variation of the alkyl-chain length of the cation are investigated by both solvatochromic dyes and spin probes. Two different polarity scales are used for discussion of the polarity of these ionic liquids. These polarity scales are the empirical Kamlet-Taft parameters alpha, beta, and pi* and the hyperfine coupling constants A(iso)(N-14) obtained for spin probes substituted either with an ammonio or a sulfate group at 4-position. The results show that both polarity scales are valid for description of the ionic liquid polarity although differences are found between the two polarity scales. The most clear trend is found in all ionic liquids investigated for the hydrogen-bond accepting ability (beta) and the hyperfine- coupling constant of the anionic spin probe, where both parameters increase for all ionic liquids investigated until an alkyl chain length of eight carbon atoms and keep constant at longer alkyl chains. Y1 - 2010 UR - http://rsc.org/Publishing/Journals/nj/ U6 - https://doi.org/10.1039/C0nj00253d SN - 1144-0546 ER - TY - JOUR A1 - Borchert, Manuela A1 - Wilke, Max A1 - Schmidt, Christian A1 - Rickers, Karen T1 - Rb and Sr partitioning between haplogranitic melts and aqueous solutions N2 - Rubidium and strontium partitioning experiments between haplogranitic melts and aqueous fluids (water or 1.16- 3.56 m (NaCl + KCl) +/- HCl) were conducted at 750-950 degrees C and 0.2-1.4 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. In addition, we studied if the applied technique (rapid and slow quench, and in-situ determination of trace element concentration in the fluid) has a bearing on the obtained data. There is good agreement of the data from different techniques for chloridic solutions, whereas back reactions between fluid and Melt upon cooling have a significant effect on results from the experiments with water. The Rb fluid-melt partition coefficient shows no recognizable dependence on melt composition and temperature. For chloridic Solutions, it is similar to 0.4, independent of pressure. In experiments with water, it is one to two orders of magnitude lower and increases with pressure. The strontium fluid-melt partition coefficient does not depend on temperature. It increases slightly with pressure in Cl free experiments. In chloridic fluids, there is a sharp increase in the Sr partition coefficient with the alumina saturation index (ASI) from 0.003 at an ASI of 0.8 to a maximum of 0.3 at an ASI of 1.05. At higher ASI, it decreases slightly to 0.2 at an ASI of 1.6. It is one to two orders of magnitude higher in chloridic fluids compared to those found in H2O experiments. The Rb/Sr ratio in non-chloridic solutions in equilibrium with metaluminous melts increases with pressure, whereas the Rb/Sr ratio in chloridic fluids is independent of pressure and decreases with fluid salinity. The obtained fluid-melt partition coefficients are in good agreement with data from natural cogenetic fluid and melt inclusions. Numerical modeling shows that although the Rb/Sr ratio in the residual melt is particularly sensitive to the degree of fractional crystallization, exsolution of a fluid phase, and associated fluid-melt partitioning is not a significant factor controlling Rb and Sr concentrations in the residual melt during crystallization of most granitoids. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00167037 U6 - https://doi.org/10.1016/j.gca.2009.10.033 SN - 0016-7037 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Boelke, Ute A1 - Kreicberga, Jana T1 - Quantification of the push-pull character of azo dyes and a basis for their evaluation as potential nonlinear optical materials N2 - The push-pull characters of a large series of donor-acceptor substituted azo dyesù71 structures in allùhave been quantified by the NN double bond lengths, dNN, the 15N NMR chemical shift differences, ;;15N, of the two nitrogen atoms and the quotient, ;*/;, of the occupations of the antibonding ;*, and bonding ; orbitals of this partial NN double bond. The excellent correlation of the occupation quotients with the bond lengths strongly infers that both ;*/; and dNN are excellent parameters for quantifying charge alternation in the push-pull chromophore and the molecular hyperpolarizability, ;0, of these compounds. By this approach, selected compounds can be appropriately considered as viable candidates for nonlinear optical (NLO) applications. Y1 - 2010 SN - 0040-4020 ER - TY - THES A1 - Verch, Andreas T1 - Pränukleationscluster und ihre Wechselwirkungen mit Additiven Y1 - 2010 CY - Potsdam ER - TY - JOUR A1 - Siegmann, Rebekka A1 - Jelicic, Aleksandra T1 - Propagation and termination kinetics of PEGylated methacrylate radical polymerizations N2 - Propagation and chain-length averaged termination rate coefficients, k(p) and , for radical polymerizations of methacrylates carrying poly(ethylene glycol) (PEG) units are reported. kp derived from pulsed laser initiated polymerizations in bulk, in organic solvents, and in ionic liquids follows the methacrylate-type family behavior. Contrary, diffusion controlled k(t) values obtained from chemically initiated polymerizations with in-line FT- NIR monitoring of monomer conversion are strongly affected by the PEG units in the ester group. Compared to alkyl methacrylates is unexpectedly high. Moreover, of poly(ethylene glycol) ethyl ether methacrylate shows a significant reduction in k(t) already at 15% conversion, whereas dodecyl methacrylate is constant up to at least 70% conversion. Y1 - 2010 UR - http://www3.interscience.wiley.com/journal/10003495/home U6 - https://doi.org/10.1002/macp.200900527 SN - 1022-1352 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Probing the exohedral magnetic properties of C20 derivatives by through space NMR shieldings (TSNMRS) N2 - The through space NMR shieldings (TSNMRS) of dodecahedrane C20H20, of the isomeric hydrocarbons C20H12, of the ions C20H122+ and C20H122- of the fluxional fullerene C20 and of its dication C202+ have been ab initio calculated employing the NICS concept on basis of MP2/6-31G* geometries and visualized as iso-chemical-shielding/deshielding surfaces (ICSSs). TSNMRS values were employed to study the exohedral magnetic properties of the compounds studied. Hereby, the curved It-conjugation in the compounds studied could be quantified. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/01661280 U6 - https://doi.org/10.1016/j.theochem.2009.09.018 SN - 0166-1280 ER - TY - THES A1 - Cui, Jing T1 - Preparation of medical grade, amorphous polymer systems with adjustable stiffness and development of self- surfficiently moving model scaffolds based on shape-memory polymer composites Y1 - 2010 CY - Potsdam ER - TY - THES A1 - Hermes, Florian Johannes T1 - Polypeptide-hybrid block copolymers : chain length and conformation effects on the self-assembly in solution Y1 - 2010 CY - Potsdam ER - TY - JOUR A1 - Tiseanu, Carmen A1 - Parvulescu, Vasile Ion A1 - Cojocaru, Bogdan A1 - Lorenz-Fonfria, Victor A. A1 - Kumke, Michael Uwe A1 - Gessner, Andre A1 - Enculescu, Ion T1 - Polymer-microporous host interactions probed by photoluminescence spectroscopy N2 - Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed. Y1 - 2010 UR - http://www.rsc.org/Publishing/Journals/CP/index.asp U6 - https://doi.org/10.1039/B922591a SN - 1463-9076 ER - TY - JOUR A1 - Webster, Dean C. A1 - Meier, Michael A. R. T1 - Polymer libraries : preparation and applications N2 - Polymer libraries offer straightforward opportunities for the investigation of structure property relationships and for a more thorough understanding of certain research problems. Furthermore, if combined with high-throughput methods for their preparation as well as screening, they offer the additional advantage of time savings and/or the reduction of experimental efforts. Thus, the herein discussed methods of polymer library preparation and selected literature examples of polymer libraries describe efficient and state-of-the-art methods to tackle difficult research challenges in polymer and materials science. Y1 - 2010 UR - http://www.springerlink.com/content/tk40663747722833/ U6 - https://doi.org/10.1007/12_2009_15 SN - 0065-3195 ER - TY - JOUR A1 - de Espinosa, Lucas Montero A1 - Meier, Michael A. R. A1 - Ronda, Juan C. A1 - Galiß, Marina A1 - Cßdiz, Virginia T1 - Phosphorus-containing renewable polyester-polyols via ADMET polymerization : synthesis, functionalization, and radical crosslinking N2 - An alpha,omega-diene containing hydroxyl groups was prepared from plant oil-derived platform chemicals. The acyclic diene metathesis copolymerization (ADMET) of this monomer with a phosphorus-containing alpha,omega-cliene (DOPO II), also plant oil derived, afforded a series of phosphorus containing linear polyesters, which have been fully characterized. The backbone hydroxyls of these polyesters have been acrylated and radically polymerized to produce crosslinked polymers. The thermomechanical and mechanical properties, the thermal stability, and the flame retardancy of these phosphorus-based thermosets have been studied. Moreover, methyl 10-undecenoate has been used as chain stopper in selected ADMET polymerizations to study the effect of the prepolymers' molecular weights on the different properties of the final materials. Y1 - 2010 UR - http://www3.interscience.wiley.com/journal/117932467/tocgroup U6 - https://doi.org/10.1002/Pola.23887 SN - 0887-624X ER - TY - JOUR A1 - Fechner, Mabya A1 - Kosmella, Sabine A1 - Koetz, Joachim T1 - pH-dependent polyampholyte SDS interactions N2 - Aqueous solutions of sodium dodecylsulfate (SDS) and poly(N,N'-diallyl-N,N'-dimethyl-alt-maleamic carboxylate) (PalH), a synthetic pH-tuneable polyelectrolyte (PEL), have been investigated by various techniques at different pH-values in absence and presence of NaCl. Potentiometric measurements using a surfactant-selective electrode indicate a quite complex interaction mechanism, which can be subdivided into different regions, where non-cooperative, electrostatic and cooperative hydrophobic interactions are of relevance. It was concluded, that in dependence on pH, conformational changes are responsible for the different interaction behavior in the NaCl-free system. Isothermal titration calorimetry (ITC) suggests that early stage hydrophobic binding is an exothermic process followed by electrostatic interactions, which are endothermic in nature and entropy driven. After NaCl addition the interaction mechanism becomes independent of pH due to a screening of (i) attractive interactions between the surfactant head groups and oppositely charged binding sites and (ii) repulsive forces between the surfactant head groups. Furthermore, the ITC investigations have revealed that after salt-addition surfactant micelles interact with the polymer instead of separated SDS molecules due to a depression of the CMC. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00219797 U6 - https://doi.org/10.1016/j.jcis.2010.01.092 SN - 0021-9797 ER - TY - THES A1 - Rasch, Claudia T1 - Optische Spektroskopie zum Nachweis von Schimmelpilzen und deren Mykotoxine T1 - Optical spectroscopy for the determination of mould and mycotoxins N2 - Gesunde sowie qualitativ hochwertige Nahrungsmittel sind wichtige Voraussetzungen, um einerseits die Lebensmittelsicherheit entlang der Wertschöpfungskette (Wachstum, Verarbeitung, Lagerung und Transport) und andererseits einen vorbeugenden Verbraucherschutz zu gewährleisten. Die Belastung der Nahrung mit Rückständen jeglicher Art war in letzter Zeit häufig Mittelpunkt heftiger öffentlicher Diskussionen. Zahlreiche Untersuchungen haben gezeigt, dass unter bestimmten Bedingungen durch Pilze gebildete Giftstoffe, so genannte Mykotoxine, die Ernteprodukte belasten und es bei deren Verzehr durch Menschen oder Tiere zu Vergiftungen kommen kann. Die FAO schätzt, dass etwa 25% der Weltproduktion von Nahrungsmitteln mit Mykotoxinen kontaminiert und in 20% der Getreideernte der Europäischen Union messbare Konzentrationen an Mykotoxinen detektierbar sind. Damit die Lebensmittelsicherheit weiterhin gewährleistet bleibt, werden neben den Routinemethoden schnellere und zerstörungsfreie Methoden benötigt, um die Lebensmittel direkt vor Ort auf Schimmelpilze und deren Mykotoxine zu untersuchen. In dieser Arbeit wird das Potenzial von ausgewählten optisch-basierten spektroskopischen Methoden für die in-situ bzw. in-line Detektion von Schimmelpilzen sowie Mykotoxinen in Getreide(produkten) untersucht. Es werden Absorptions- und Reflexionsmethoden einerseits und Fluoreszenztechniken andererseits eingesetzt. Die spektroskopischen Methoden werden dabei auf Proben unterschiedlicher Komplexität angewandt - beginnend mit der Untersuchung der photophysikalischen Eigenschaften der reinen Mykotoxine in Lösung über künstlich mit verschiedenen Mykotoxinen kontaminierten Getreideproben bis hin zu mit Pilzen befallenem Getreide und hochveredelte Lebensmittel (Wein und Bier) als Proben höchster Komplexität. N2 - Problems of food safety have led to an increasing concern regarding contamination of foods and feeds with mycotoxins and the relevant toxigenic fungi, mainly Aspergillus, Penicillium and Fusarium genera. There is a real need for rapid, sensitive and inexpensive sensors for the detection of toxigenic fungi and mycotoxins, both in the field and after harvest in order to obtain real-time monitoring data on contamination and this assist in food safety assessment. This will result in an enormous cost saving to the farmers as well as to agro-food industry through the prevention and reduction of product recalls and reduced treatment costs. The German Ministry of Education and Research (BMBF) has provided funding of more than 1.9 million Euros from July 2006 to December 2009 for the large joint project "ProSeso.net2" on the development of innovative sensor-based techniques and processes in the field of food quality and safety. In this research-project "Exploration of sustainability potentials by use of sensor-based technologies and integrated assessment models in the production chain of plant related food" 13 partners from universities, non-university institutions and industry cooperate within seven subprojects. The expected results shall contribute to maintain freshness and improve safety of the food production chain. In the subproject “Indicators and sensor technology for the identification of mycotoxin producing fungi in the processing of grain” spectroscopic methods are tested for in-situ and in-line detection of moulds and/or mycotoxins. This presentation focuses on some possible spectroscopic methods for the rapid detection of mycotoxins and fungi on grains. Methods based on one- and two-photon-induced fluorescence spectroscopy are highly attractive because of their outstanding sensitivity and selectivity. In order to utilize a fluorescence technique for the analysis of the mycotoxins in food and feedstuff as well as for basic research on the fungal metabolism, the photochemistry and photophysics of the mycotoxins and fungi need to be elucidated in detail, especially the influence of solvent parameters such as polarity and pH value. Consequently, for a sensitive and selective spectroscopic analysis, it is indispensable to take the specific photophysic of the known mycotoxins into account in order to minimize serious limitations upon sensitivity, selectivity, and accuracy of a potential fluorescence-based sensing application. The spectroscopic techniques are complemented by chemometric tools (Principle Component Analysis) to extract the desired chemical information, e.g. with respect to presence of contaminations. The combination of data obtained from different spectroscopic methods (such as optimal excitation and emission wavelength, fluorescence decay times, and fluorescence quantum efficiency) on the one hand side and NIR spectroscopy on the other side shows promising results for the qualitative as well as quantitative identification of mycotoxins grains. Moreover, NIR reflectance spectra yield additional information on ingredients, moisture content, and the presence (or absence) of fungi in the sample. KW - Mykotoxine KW - Schimmelpilze KW - Fluoreszenz KW - Chemometrie KW - Zweiphotonenanregung KW - mycotoxins KW - mould KW - fluorescence KW - chemometrics KW - Two-Photon-Absorption Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-50746 ER - TY - JOUR A1 - Coy, Ericsson D. A1 - Jovanovic, Ljubisa A1 - Sefkow, Michael T1 - One-pot, Pd-catalyzed synthesis of trans-dihydrobenzofurans from o-aminophenols N2 - An efficient and facile synthesis of trans-dihydrobenzofurans has been accomplished from o-aminophenols and phenylpropenes via a novel (one-pot) diastereoselective Pd-catalyzed oxyarylation reaction. The development and optimization of this method is described. Y1 - 2010 UR - http://pubs.acs.org/journal/orlef7 U6 - https://doi.org/10.1021/Ol100433z SN - 1523-7060 ER - TY - JOUR A1 - Schmidt, Roland A1 - Hagen, Sebastian A1 - Brete, Daniel A1 - Carley, Robert A1 - Gahl, Cornelius A1 - Dokic, Jadranka A1 - Saalfrank, Peter A1 - Hecht, Stefan A1 - Tegeder, Petra A1 - Weinelt, Martin T1 - On the electronic and geometrical structure of the trans- and cis-isomer of tetra-tert-butyl-azobenzene on Au(111) N2 - Near edge X-ray absorption. ne structure and X-ray photoelectron spectroscopy have been employed to follow the reversible trans to cis isomerization of tetra-tert-butyl-azobenzene (TBA) adsorbed on Au(111). For one monolayer the molecules adopt an adsorption geometry characteristic of the trans-TBA isomer. The azo-bridge (N = N) is aligned nearly parallel to the surface and the phenyl rings exhibit a planar orientation with a small tilt angle <= 4 degrees with respect to the surface normal. Illumination of the molecular layer at 455 nm triggers the trans to cis isomerization which is associated with a pronounced change of the geometrical and electronic structure. The N1s to pi* transition of the central azo-bridge shifts by 0.45 +/- 0.05 eV to higher photon energy and the transition dipole moment (TDM) is tilted by 59 +/- 5 degrees with respect to the surface normal. The pi-system of one phenyl ring is tilted by about 30 degrees with respect to the surface normal, while the second ring plane is oriented nearly perpendicular to the surface. This reorientation is supported by a shift and broadening of the C-H resonances associated with the tert-butyl legs of the molecule. These findings support a configuration of the photo-switched TBA molecule on Au(111) which is comparable to the cis-isomer of the free molecule. In the photo-stationary state 53 +/- 5% of the TBA molecules are switched to the cis configuration. Thermal activation induces the back reaction to trans-TBA. Y1 - 2010 UR - http://pubs.rsc.org/en/content/articlehtml/2010/cp/b924409c U6 - https://doi.org/10.1039/B924409c SN - 1463-9076 ER - TY - JOUR A1 - Ayi, Ayi A. A1 - Khare, Varsha A1 - Strauch, Peter A1 - Girard, Jèrôme A1 - Fromm, Katharina M. A1 - Taubert, Andreas T1 - On the chemical synthesis of titanium nanoparticles from ionic liquids N2 - We report on attempts towards the synthesis of titanium nanoparticles using a wet chemical approach in imidazolium-based ionic liquids (ILs) under reducing conditions. Transmission electron microscopy finds nanoparticles in all cases. UV/Vis spectroscopy confirms the nanoparticulate nature of the precipitate, as in all cases an absorption band between ca. 280 and 300 nm is visible. IR spectroscopy shows that even after extensive washing and drying, some IL remains adsorbed on the nanoparticles. Raman spectroscopy suggests the formation of anatase nanoparticles, but X-ray diffraction reveals that, possibly, amorphous titania forms or that the nanoparticles are so small that a clear structure assignment is not possible. The report thus shows that (possibly amorphous) titanium oxides even form under reducing conditions and that the chemical synthesis of titanium nanoparticles in ILs remains elusive. Y1 - 2010 UR - http://www.springerlink.com/content/101572 U6 - https://doi.org/10.1007/s00706-010-0403-4 SN - 0026-9247 ER - TY - JOUR A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Novel anthracene materials for applications in lithography and reversible photoswitching by light and air N2 - Herein we demonstrate how the photoreaction between anthracenes and singlet oxygen (O-1(2)) is employed for applications either as photoswitch or as photoresist. Thin Films of the diaryl-alkyl anthracene 1 and the analogous oligomeric species 2 were it-radiated under photomasks to generate pattern structures composed of 1/1-O-2 and 2/2-O-2. Kelvin probe force microscopy (KPFM) provided a powerful and nondestructive method to image the pattern information. The following studies based on AFM, KPFM and contact angle measurements unfold that the two species 1 and 2 underwent different progressions after the imaging step. Degrading is observed for the monomeric compound 1 and the pattern eventually becomes recognizable in topography. In the oxidized state (1-O-2) the monomeric species remains physically stable. In consequence, the unreacted portion is removable and the remaining oxygenated form 1-O-2 is sufficiently stable to protect in underlying substrate (e.g., silver) from etching. Thus, the system 1/1-O-2 operates as photoresist. Oil the other hand, both states of the oligomier 2 remain stable. The Film is stable up to temperatures > 120 degrees C required to erase the pattern within acceptable time by cycloreversion. Anthracene 2 therefore acts as erasable and rewritable photochromic switch. The different behavior between 1 and 2 is explained by phase transitions which cause crystallization and finally ablation. Such transitions affect only the monomeric system 1/1-O-2 and not the oligomeric system 2/2-O-2. In conclusion, we designed two very similar materials based on diarylanthracenes, which can act either as a photoresist or as a rewritable photochrornic switch. Y1 - 2010 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La904299n SN - 0743-7463 ER -