TY - JOUR A1 - Klaumünzer, Bastian A1 - Kroener, Dominik T1 - N-Inversion in 2-azabicyclopentane derivatives : model simulations for a laser controlled molecular switch N2 - We report model quantum simulations for the nitrogen inversion in 2-azabicyclo[1.1.1] pentane derivates controlled by laser pulses proposing to use this class of molecules as molecular switches. The derivatives trans-5- fluoro-2-methyl-2-azabicyclo[1.1.1] pentane and cis-5-fluoro-2-methyl-2-azabicyclo[1.1.1] pentane are investigated by means of density functional theory and quantum wave packet dynamics. The molecules have two stable, i.e. energetically well-separated, conformers along the N-inversion coordinate. In 1D model simulations the transformation from one conformer to the other is accomplished in the electronic ground state by using two overlapping chirped linearly polarized IR laser pulses for the trans-and cis-isomer or alternatively via an electronic excited state employing a pump- dump sequence of ultrashort UV laser pulses. Y1 - 2009 UR - http://rsc.org/Publishing/Journals/nj/ U6 - https://doi.org/10.1039/B812319e SN - 1144-0546 ER - TY - JOUR A1 - Klamroth, Tillmann A1 - Nest, Mathias T1 - Ultrafast electronic excitations of small sodium clusters and the onset of electron thermalization N2 - In this paper we report simulations of the ultrafast laser excitation and relaxation of the correlated valence electrons of a Na-8 cluster. The aim is twofold: first, while the total energy stays constant when the exciting laser pulse is over, we observe that the entropy computed from the reduced one electron density matrix rises on a much longer time scale. We discuss whether this can be understood as the onset of the thermalization of a finite system. Second, we describe this process with eight different methods of wavefunction-based electronic structure theory, which have been adapted for an explicitly time-dependent description. Their respective advantages and limitations for the simulation of the excitation and subsequent relaxation are explained. Y1 - 2009 UR - http://pubs.rsc.org/en/Journals/JournalIssues/CP U6 - https://doi.org/10.1039/B813619j SN - 1463-9076 ER - TY - JOUR A1 - Kind, Lucy A1 - Plamper, Felix A. A1 - Goebel, Ronald A1 - Mantion, Alexandre A1 - Mueller, Axel H. E. A1 - Pieles, Uwe A1 - Taubert, Andreas A1 - Meier, Wolfgang P. T1 - Silsesquioxane/polyamine nanoparticle-templated formation of star- or raspberry-like silica nanoparticles N2 - Silica is an important mineral in biology and technology, and many protocols have been developed for the synthesis of complex silica architectures. The current report shows that silsesquioxane nanoparticles carrying polymer arms on their surface are efficient templates for the fabrication of silica particles with a star- or raspberry-like morphology. The shape of the resulting particles depends on the chemistry of the polymer arms. With poly(N,N- dimethylaminoethyl methacrylate) (PDMAEMA) arms, spherical particles with a less electron dense core form. With poly {[2- (methacryloyloxy)ethyl] trimethylammonium iodide} (PMETAI), star- or raspberry-like particles form. Electron microscopy, electron tomography, and small-angle X-ray scattering show that the resulting silica particles have a complex structure, where a silsequioxane nanoparticle carrying the polymer arms is in the center. Next is a region that is polymer-rich. The outermost region of the particle is a silica layer, where the outer parts of the polymer arms are embedded. Time- resolved zeta-potential and pH measurements, dynamic light scattering, and electron microscopy reveal that silica formation proceeds differently if PDMAEMA is exchanged for PMETAI. Y1 - 2009 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La900229n SN - 0743-7463 ER - TY - JOUR A1 - Kadjane, Pascal A1 - Starck, Matthieu A1 - Camerel, Franck A1 - Hill, Diana A1 - Hildebrandt, Niko A1 - Ziessel, Raymond A1 - Charbonnière, Loïc J. T1 - Divergent approach to a large variety of versatile luminescent lanthanide complexes N2 - Using a regioselective strategy for nucleophilic aromatic substitution on polyfluoropyridines, a nonacoordinating precursor was designed that is adequately suited for complexation of lanthanide cations. Further functionalizations afforded numerous applications for near-IR emission, two-photon absorption spectroscopy, or the formation of luminescent gels. Y1 - 2009 UR - http://pubs.acs.org/journal/inocaj U6 - https://doi.org/10.1021/Ic9001169 SN - 0020-1669 ER - TY - JOUR A1 - Jyotishkumar, P. A1 - Koetz, Joachim A1 - Tiersch, Brigitte A1 - Strehmel, Veronika A1 - oezdilek, Ceren A1 - Moldenaers, Paula A1 - Hässler, Rüdiger A1 - Thomas, Sabu T1 - Complex phase separation in poly(acrylonitrile-butadiene-styrene)-modified epoxy/4,4 '-diaminodiphenyl sulfone blends : generation of new micro- and nanosubstructures N2 - The epoxy system containing diglycidyl ether of bisphenol A and 4,4'-diaminodiphenyl sulfone is modified with poly(acrylonitrile-butadiene-styrene) (ABS) to explore the effects of the ABS content on the phase morphology, mechanism of phase separation, and viscoelastic properties. The amount of ABS in the blends was 5, 10, 15, and 20 parts per hundred of epoxy resin (phr). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to investigate the final morphology of ABS-modified epoxy blends. Scanning electron microscopic studies of 15 phr ABS-modified epoxy blends reveal a bicontinuous structure in which both epoxy and ABS are continuous, with substructures of the ABS phase dispersed in the continuous epoxy phase and substructures of the epoxy phase dispersed in the continuous ABS phase. TEM micrographs of 15 phr ABS-modified epoxy blends confirm the results observed by SEM. TEM micrographs reveal the existence of nanosubstructures of ABS in 20 phr ABS-modified epoxy blends. To the best of our knowledge, to date, nanosubstructures have never been reported in any epoxy/thermoplastic blends. The influence of the concentration of the thermoplastic on the generated morphology as analyzed by SEM and TEM was explained in detail. The evolution and mechanism of phase separation was investigated in detail by optical microscopy (OM) and small-angle laser light scattering (SALLS). At concentrations lower than 10 phr the system phase separates through nucleation and growth (NG). However, at higher concentrations, 15 and 20 phr, the blends phase separate through both NG and spinodal decomposition mechanisms. On the basis of OM and SALLS, we conclude that the phenomenon of complex substructure formation in dynamic asymmetric blends is due to the combined effect of hydrodynamics and viscoelasticity. Additionally, dynamic mechanical analysis was carried out to evaluate the viscoelastic behavior of the cross-linked epoxy/ABS blends. Finally, apparent weight fractions of epoxy and ABS components in epoxy- and ABS-rich phases were evaluated from T-g analysis. Y1 - 2009 UR - http://pubs.acs.org/journal/jpcbfk U6 - https://doi.org/10.1021/Jp8094566 SN - 1520-6106 ER - TY - JOUR A1 - Graf, Philipp A1 - Mantion, Alexandre A1 - Foelske, Annette A1 - Shkilnyy, Andriy A1 - MaÜic, Admir A1 - Thuenemann, Andreas F. A1 - Taubert, Andreas T1 - Peptide-coated silver nanoparticles : synthesis, surface chemistry, and pH-triggered, reversible assembly into particle assemblies N2 - Simple tripeptides are scaffolds for the synthesis and further assembly of peptide/silver nanoparticle composites. Herein, we further explore peptide-con trolled silver nanoparticle assembly processes. Silver nanoparticles with a pH-responsive peptide coating have been synthesized by using a one-step precipitation/coating route. The nature of the peptide/silver interaction and the effect of the peptide oil the formation of the silver particles have been studied via UV/Vis, X-ray photoelectron, and surface-enhanced Raman spectroscopies as well as through electron microscopy, small angle X-ray scattering and powder Xray diffraction with Rietveld refinement. The particles reversibly form aggregates of different sizes in aqueous solution. The state of aggregation call be controlled by the solution pH value. At low pH values, individual particles are present. At neutral pH values, small clusters form and at high pH values, large precipitates are observed. Y1 - 2009 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/26293/ U6 - https://doi.org/10.1002/chem.200802329 SN - 0947-6539 ER - TY - JOUR A1 - Götze, Jan A1 - Saalfrank, Peter T1 - Serine in BLUF domains displays spectral importance in computational models N2 - The BLUF (blue-light sensing using flavine) domain of the AppA photoreceptor protein from Rhodobacter sphaeroides was modelled by using quantum chemical chromophore plus amino acid models at the (TD-)B3LYP/6-31G* level of theory. The models were based on NMR structures, and further refined by CHARM force field molecular dynamics simulations. The goal is to explain the total redshift by about 10 nm in the UV/Vis spectra of BLUF domains after illumination, and to relate it to structural changes. For this purpose UV/Vis spectra of the available NMR structures were calculated and related to geometrical features. In particular, the hydrogen network embedding the central chromophore is discussed. Specifically, the position of a conserved glutamine, Q63, is found to be important in agreement with findings from previous works. Additionally, however, we find a systematic dependence also on the geometry of a conserved serine, S41. Based on a series of calculations with known structures and with artificial structural models, we argue that indeed the light-induced switching of both Q63 and S41 is necessary to explain the full similar to 10 nm redshift in the light (signalling) state of serine containing BLUF domains. Following or accompanying the double switching, two structurally highly important residues W104 and M106 exchange places, but do not affect the overall UV/ Vis properties of the chromophore. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/10111344 U6 - https://doi.org/10.1016/j.jphotobiol.2008.10.003 SN - 1011-1344 ER - TY - JOUR A1 - Goebel, Ronald A1 - Hesemann, Peter A1 - Weber, Jens A1 - Moeller, Eléonore A1 - Friedrich, Alwin A1 - Beuermann, Sabine A1 - Taubert, Andreas T1 - Surprisingly high, bulk liquid-like mobility of silica-confined ionic liquids N2 - Mesoporous silica monoliths were prepared by the sol - gel technique and. lled with 1-ethyl-3-methyl imidazolium [Emim]-X (X = dicyanamide [N(CN)(2)], ethyl sulfate [EtSO4], thiocyanate [SCN], and triflate [TfO]) ionic liquids (ILs) using a methanol-IL exchange technique. The structure and behavior of the ILs inside the silica monoliths were studied using X-ray scattering, nitrogen sorption, IR spectroscopy, solid-state NMR, and thermal analysis. DSC finds shifts in both the glass transition temperature and melting points (where applicable) of the ILs. Glass transition and melting occur well below room temperature. There is thus no conflict with the NMR and IR data, which show that the ILs are as mobile at room temperature as the bulk (not confined) ILs. The very narrow line widths of the NMR spectra suggest that the ILs in our materials have the highest mobility reported for confined ILs so far. As a result, our data suggest that it is possible to generate IL/silica hybrid materials (ionogels) with bulk-like properties of the IL. This could be interesting for applications in, e.g., the solar cell or membrane fields. Y1 - 2009 UR - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CP U6 - https://doi.org/10.1039/B821833a SN - 1463-9076 ER - TY - JOUR A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Photoimaging with singlet oxygen at the solid-air interface N2 - Films of anthracene carboxylic acids were irradiated through photomasks and oxidized at the exposed regions by singlet oxygen upon sensitization. The efficiency of a photomask to protect the material underneath was investigated by optical and infrared spectroscopy. As the thickness of the film is reduced, the efficiency of the mask drops. This is explained by the migration of singlet oxygen at the solid-air interface, which in turn reacts at the masked area. For films with a thickness of < 15 nm, the efficiency of the mask approaches zero: sufficient efficiency is achieved at thicknesses > 100 nm. From the investigations, it will become clear that the contrast between the irradiated and masked area of an image is affected by reduction of the film thickness. On the other hand, the resolution of an image, which relates to the minimum feature size of an image, is not dependent on the thickness of the film. The contributions of "inside" and "outside" reactions are examined separately, and it quantitative approximation of the spatial range of both modes of the oxygenation is given. We set tip an approximate relation between mask efficiency and experimental conditions comprising internal and external oxygen diffusion, film thickness, and mask dimensions. These results give it deeper insight into the limits of resolution and contrast in singlet oxygen lithography. Y1 - 2009 UR - http://pubs.acs.org/journal/langd5 U6 - https://doi.org/10.1021/La9008976 SN - 0743-7463 ER - TY - JOUR A1 - Elamparuthi, Elangovan A1 - Linker, Torsten T1 - Carbohydrate-2-deoxy-2-phosphonates : simple synthesis and Horner-Emmons reaction N2 - Phosphorus meets carbohydrates: Dimethyl phosphite reacts with ceric(IV) ammonium nitrate (CAN) to give phosphonyl radicals that add to glycals 1. The derivatives 2 were isolated in high yields and during a subsequent Horner-Emmons reaction underwent an interesting elimination to give 3,6-dihydro-2H-pyrans 3. The short sequence with simple precursors is applicable to the transformation of hexoses, pentoses, and disaccharides. Bn=benzyl. Y1 - 2009 UR - http://onlinelibrary.wiley.com/journal/10.1002/(28ISSN)291521-3773 U6 - https://doi.org/10.1002/anie.200804725 SN - 1433-7851 ER -