TY - JOUR A1 - Traulsen, C.H.-H. A1 - Kunz, V. A1 - Heinrich, Thomas A1 - Richter, S. A1 - Holzweber, Markus A1 - Schulz, A. A1 - von Krbek, L.K.S. A1 - Scheuschner, U.T.J. A1 - Poppenberg, J. A1 - Unger, Wolfgang A1 - Schalley, C.A. T1 - Synthesis and coordinative layer-by-layer deposition of pyridine-functionalized gold nanoparticles and tetralactam macrocycles on silicon substrates N2 - Coordination chemistry was applied to deposit pyridine-functionalized gold nanoparticles on silicon substrates. The particles were synthesized through the Brust/Schiffrin route with a subsequent ligand exchange reaction yielding well-defined particles of two different sizes. Multilayer deposition was carried out on a pyridine-terminated SAM, anchored on a hydroxyl-terminated silicon surface. Analogously, Hunter/Vögtle-type tetralactam macrocycle multilayers were deposited as well as mixed layers containing both either in an alternating sequence or as a macrocycle multilayer with a terminating nanoparticle layer. These composite layers were examined with respect to their ability to bind squaraine axles in the macrocycle cavities. The amount of guest bound is higher for the composite layer with alternating macrocycles and nanoparticles. KW - Layer-by-layer deposition KW - Functionalized Au nanoparticles KW - SEM KW - TEM KW - DLS KW - XPS KW - NEXAFS KW - ToF-SIMS KW - IR KW - UV-vis PY - 2013 U6 - https://doi.org/10.1021/la403222x SN - 0743-7463 SN - 1520-5827 VL - 29 IS - 46 SP - 14284 EP - 14292 PB - American Chemical Society CY - Washington, DC AN - OPUS4-29699 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ehlert, Christopher A1 - Holzweber, Markus A1 - Lippitz, Andreas A1 - Unger, Wolfgang A1 - Saalfrank, Peter T1 - A detailed assignment of NEXAFS resonances of imidazolium based ionic liquids N2 - In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC₁im]⁺[NTf₂]⁻ and [C₄C₁im]⁺[I]⁻). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra. KW - Ionic liquids KW - NEXAFS KW - DFT spectrum simulations PY - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-367223 SN - 1463-9076 SN - 1463-9084 VL - 18 IS - 12 SP - 8654 EP - 8661 PB - Royal Society of Chemistry CY - Cambridge, UK AN - OPUS4-36722 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dietrich, Paul A1 - Hennig, Andreas A1 - Holzweber, Markus A1 - Thiele, T. A1 - Borcherding, H. A1 - Lippitz, Andreas A1 - Schedler, U. A1 - Resch-Genger, Ute A1 - Unger, Wolfgang T1 - Surface analytical study of poly(acrylic acid)-grafted microparticles (beads): characterization, chemical derivatization, and quantification of surface carboxyl groups N2 - We report a surface analytical study of poly(methyl methacrylate) (PMMA) microparticles (beads) with a grafted shell of poly(acrylic acid) (PAA) with thicknesses up to 4 nm using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy. These polymer microparticles were analyzed before and after reaction of the surface carboxyl (CO2H) groups with 2,2,2-trifluoroethylamine (TFEA) to gain a better understanding of methods with use of covalently bound probe molecules for surface group analysis. The results obtained with chemical derivatization XPS using TFEA are discussed in terms of surface quantification of reactive CO2H groups on these PAA-coated microparticles. A labeling yield of about 50% was found for TFEA-derivatized particles with amounts of surface-grafted CO2H groups of 99 µmol/g or more, which is consistent with predicted reaction yields for homogeneously dispersed PAA hydrogels. KW - Polymer microparticles KW - Poly(acrylic acid)-grafted microparticles KW - Beads KW - XPS KW - SEM KW - NEXAFS KW - Surface analysis KW - Fluorine labeling PY - 2014 U6 - https://doi.org/10.1021/jp505519g SN - 1932-7447 SN - 1089-5639 VL - 118 IS - 35 SP - 20393 EP - 20404 PB - Soc. CY - Washington, DC AN - OPUS4-31326 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinrich, Thomas A1 - Traulsen, Christoph Hans-Henning A1 - Holzweber, Markus A1 - Richter, S. A1 - Kunz, V. A1 - Kastner, S.K. A1 - Krabbenborg, S.O. A1 - Huskens, J. A1 - Unger, Wolfgang A1 - Schalley, C.A. T1 - Coupled molecular switching processes in ordered mono- and multilayers of stimulus-responsive rotaxanes on gold surfaces N2 - Interfaces provide the structural basis for function as, for example, encountered in nature in the membrane-embedded photosystem or in technology in solar cells. Synthetic functional multilayers of molecules cooperating in a coupled manner can be fabricated on surfaces through layer-by-layer self-assembly. Ordered arrays of stimulus-responsive rotaxanes undergoing well-controlled axle shuttling are excellent candidates for coupled mechanical motion. Such stimulus-responsive surfaces may help integrate synthetic molecular machines in larger systems exhibiting even macroscopic effects or generating mechanical work from chemical energy through cooperative action. The present work demonstrates the successful deposition of ordered mono- and multilayers of chemically switchable rotaxanes on gold surfaces. Rotaxane mono- and multilayers are shown to reversibly switch in a coupled manner between two ordered states as revealed by linear dichroism effects in angle-resolved NEXAFS spectra. Such a concerted switching process is observed only when the surfaces are well packed, while less densely packed surfaces lacking lateral order do not exhibit such effects. KW - Molecular machine KW - Rotaxane KW - LBL growth KW - XPS KW - NEXAFS KW - SIMS PY - 2015 U6 - https://doi.org/10.1021/ja512654d SN - 0002-7863 SN - 1520-5126 VL - 137 IS - 13 SP - 4382 EP - 4390 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-33077 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, S. A1 - Traulsen, C. H.-H. A1 - Heinrich, Thomas A1 - Poppenberg, J. A1 - Leppich, C. A1 - Holzweber, Markus A1 - Unger, Wolfgang A1 - Schalley, C.A. T1 - Sequence-programmable multicomponent multilayers of nanometer-sized tetralactam macrocycles on gold surfaces N2 - Multicomponent multilayers have been deposited on gold surfaces by metal-ion-mediated layer-by-layer self-assembly of differently functionalized tetralactam macrocycles. The layer stack can be programmed with respect to the sequences of metal ions and macrocycles by the deposition sequence. KW - Organic layer KW - XPS KW - SIMS KW - NEXAFS PY - 2013 U6 - https://doi.org/10.1021/jp405492v SN - 1932-7447 SN - 1089-5639 VL - 117 IS - 37 SP - 18980 EP - 18985 PB - Soc. CY - Washington, DC AN - OPUS4-32576 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -