TY - THES A1 - Frieß, Fabian T1 - Shape-memory polymer micronetworks Y1 - 2016 ER - TY - JOUR A1 - Gallandi, Lukas A1 - Marom, Noa A1 - Rinke, Patrick A1 - Körzdörfer, Thomas T1 - Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules II: Non-Empirically Tuned Long-Range Corrected Hybrid Functionals JF - Journal of chemical theory and computation N2 - The performance of non-empirically tuned long-range corrected hybrid functionals for the prediction of vertical ionization potentials (IPs) and electron affinities (EAs) is assessed for a set of 24 organic acceptor molecules. Basis set extrapolated coupled cluster singles, doubles, and perturbative triples [CCSD(T)] calculations serve as a reference for this study. Compared to standard exchange-correlation functionals, tuned long-range corrected hybrid functionals produce highly reliable results for vertical IPs and EAs, yielding mean absolute errors on par with computationally more demanding GW calculations. In particular, it is demonstrated that long-range corrected hybrid functionals serve as ideal starting points for non-self-consistent GW calculations. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jctc.5b00873 SN - 1549-9618 SN - 1549-9626 VL - 12 SP - 605 EP - 614 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Gangloff, Niklas A1 - Ulbricht, Juliane A1 - Lorson, Thomas A1 - Schlaad, Helmut A1 - Luxenhofer, Robert T1 - Peptoids and Polypeptoids at the Frontier of Supra- and Macromolecular Engineering JF - Chemical reviews Y1 - 2016 U6 - https://doi.org/10.1021/acs.chemrev.5b00201 SN - 0009-2665 SN - 1520-6890 VL - 116 SP - 1753 EP - 1802 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Guiet, Amandine A1 - Unmüssig, Tobias A1 - Göbel, Caren A1 - Vainio, Ulla A1 - Wollgarten, Markus A1 - Driess, Matthias A1 - Schlaad, Helmut A1 - Polte, Jörg A1 - Fischer, Anna T1 - Yolk@Shell Nanoarchitectures with Bimetallic Nanocores - Synthesis and Electrocatalytic Applications JF - Earth & planetary science letters KW - AgAu alloy nanoparticles KW - tin-rich ITO KW - yolk@shell materials KW - nanoreactor KW - soft-templating KW - inverse micelles KW - polystyrene-block-poly(4-vinylpyridine) Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b06595 SN - 1944-8244 VL - 8 SP - 28019 EP - 28029 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Göbel, Ronald A1 - Stoltenberg, Marcus A1 - Krehl, Stefan A1 - Biolley, Christine A1 - Rothe, Regina A1 - Schmidt, Bernd A1 - Hesemann, Peter A1 - Taubert, Andreas T1 - A Modular Approach towards Mesoporous Silica Monoliths with Organically Modified Pore Walls: Nucleophilic Addition, Olefin Metathesis, and Cycloaddition JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - We have synthesized mesoporous silica (monoliths) with defined surface chemistry by means of a number of addition reactions: (i) coupling of an isocyanate to a surface-immobilized thiol, (ii) addition of an epoxide to a surface-immobilized thiol, (iii) cross-metathesis between two olefins, and (iv) Huisgen [2+3] cycloaddition of an alkyne-functionalized silica monolith with an azide. Functionalization of the mesopores was observed, but there are significant differences between individual approaches. Isocyanate and epoxide additions lead to high degrees of functionalization, whereas olefin metathesis and [2+3] cycloaddition are less effective. We further show that the efficiency of the modification is about twice as high in mesoporous silica particles than in macroscopic silica monoliths. KW - Mesoporous materials KW - Hybrid materials KW - Surface chemistry KW - Click chemistry KW - Nucleophilic addition Y1 - 2016 U6 - https://doi.org/10.1002/ejic.201500638 SN - 1434-1948 SN - 1099-0682 VL - 6 SP - 2088 EP - 2099 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Hardy, John G. A1 - Torres-Rendon, Jose Guillermo A1 - Leal-Egana, Aldo A1 - Walther, Andreas A1 - Schlaad, Helmut A1 - Coelfen, Helmut A1 - Scheibel, Thomas R. T1 - Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering JF - Materials N2 - Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering. KW - spider silk KW - recombinant protein KW - biodegradable polymers KW - biomaterials KW - biomineralization KW - bone tissue engineering Y1 - 2016 U6 - https://doi.org/10.3390/ma9070560 SN - 1996-1944 VL - 9 SP - 93 EP - 108 PB - MDPI CY - Basel ER - TY - JOUR A1 - Herfurth, Christoph A1 - Laschewsky, Andre A1 - Noirez, Laurence A1 - von Lospichl, Benjamin A1 - Gradzielski, Michael T1 - Thermoresponsive (star) block copolymers from one-pot sequential RAFT polymerizations and their self-assembly in aqueous solution JF - Polymer : the international journal for the science and technology of polymers N2 - A series of hydrophobically end-capped linear triblock copolymers as well as of three-arm and four-arm star block copolymers was synthesized in a one-pot procedure from N,N-dimethylacrylamide (DMA) and N, N-diethylacrylamide (DEA). The sequential reversible addition-fragmentation chain transfer (RAFT) polymerization of these monomers via the R-approach using bi-, tri- and tetrafunctional chain transfer agents (CrAs) bearing hydrophobic dodecyl moieties proceeded in a well-controlled manner up to almost quantitative conversion. Polymers with molar masses up to 150 kDa, narrow molar mass distribution (PDI <= 1.3) and high end group functionality were obtained, which are thermoresponsive in aqueous solution showing a LCST (lower critical solution temperature) transition. The temperature-dependent associative behavior of the polymers was examined using turbidimetry, static and dynamic light scattering (SLS, DLS), and small angle neutron scattering (SANS) for structural analysis. At 25 degrees C, the polymers form weak transient networks, and rather small hydrophobic domains are already present for polymer concentrations of 5 wt%. However, when heating above the LCST transition (35-40 degrees C) of the PDEA blocks, the enhanced formation of hydrophobic domains is observed by means of light and neutron scattering. These domains have a size of about 12-15 nm and must be effectively physically cross-linked as they induce high viscosity for the more concentrated samples. SANS shows that these domains are ordered as evidenced by the appearance of a correlation peak. The copolymer architecture affects in particular the extent of ordering as the four-arm star block copolymer shows much more repulsive interactions compared to the analogous copolymers with a lower number of arms. (C) 2016 Elsevier Ltd. All rights reserved. KW - RAFT polymerization KW - Block copolymers KW - Thermosensitivity KW - LCST KW - SANS KW - Light scattering Y1 - 2016 U6 - https://doi.org/10.1016/j.polymer.2016.09.089 SN - 0032-3861 SN - 1873-2291 VL - 107 SP - 422 EP - 433 PB - Elsevier CY - Oxford ER - TY - THES A1 - Hildebrand, Viet T1 - Twofold switchable block copolymers based on new polyzwitterions T1 - Neue Polyzwitterionbasierte Blockcopolymere mit „Schizophrenem Verhalten“ N2 - In complement to the well-established zwitterionic monomers 3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate (“SPE”) and 3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate (“SPP”), the closely related sulfobetaine monomers were synthesized and polymerized by reversible addition-fragmentation chain transfer (RAFT) polymerization, using a fluorophore labeled RAFT agent. The polyzwitterions of systematically varied molar mass were characterized with respect to their solubility in water, deuterated water, and aqueous salt solutions. These poly(sulfobetaine)s show thermoresponsive behavior in water, exhibiting upper critical solution temperatures (UCST). Phase transition temperatures depend notably on the molar mass and polymer concentration, and are much higher in D2O than in H2O. Also, the phase transition temperatures are effectively modulated by the addition of salts. The individual effects can be in parts correlated to the Hofmeister series for the anions studied. Still, they depend in a complex way on the concentration and the nature of the added electrolytes, on the one hand, and on the detailed structure of the zwitterionic side chain, on the other hand. For the polymers with the same zwitterionic side chain, it is found that methacrylamide-based poly(sulfobetaine)s exhibit higher UCST-type transition temperatures than their methacrylate analogs. The extension of the distance between polymerizable unit and zwitterionic groups from 2 to 3 methylene units decreases the UCST-type transition temperatures. Poly(sulfobetaine)s derived from aliphatic esters show higher UCST-type transition temperatures than their analogs featuring cyclic ammonium cations. The UCST-type transition temperatures increase markedly with spacer length separating the cationic and anionic moieties from 3 to 4 methylene units. Thus, apparently small variations of their chemical structure strongly affect the phase behavior of the polyzwitterions in specific aqueous environments. Water-soluble block copolymers were prepared from the zwitterionic monomers and the non-ionic monomer N-isopropylmethacrylamide (“NIPMAM”) by the RAFT polymerization. Such block copolymers with two hydrophilic blocks exhibit twofold thermoresponsive behavior in water. The poly(sulfobetaine) block shows an UCST, whereas the poly(NIPMAM) block exhibits a lower critical solution temperature (LCST). This constellation induces a structure inversion of the solvophobic aggregate, called “schizophrenic micelle”. Depending on the relative positions of the two different phase transitions, the block copolymer passes through a molecularly dissolved or an insoluble intermediate regime, which can be modulated by the polymer concentration or by the addition of salt. Whereas, at low temperature, the poly(sulfobetaine) block forms polar aggregates that are kept in solution by the poly(NIPMAM) block, at high temperature, the poly(NIPMAM) block forms hydrophobic aggregates that are kept in solution by the poly(sulfobetaine) block. Thus, aggregates can be prepared in water, which switch reversibly their “inside” to the “outside”, and vice versa. N2 - Diese Arbeit befasst sich mit der Synthese und Charakterisierung von doppelt thermisch-responsiven Blockcopolymeren mit einem polaren nicht-ionischen Block (der einen LCST-Übergang in wässriger Lösung induziert) und einem zwitterionischen Block (der einen UCST-Übergang aufweisen soll), der durch Salzzusatz über einen weiten Temperaturbereich modulierbar ist. Dafür wurden geeignete zwitterionische Polymer¬blöcke identifiziert und hergestellt, die ein derartiges Löslichkeitsprofil aufweisen. Da bislang nur relativ wenige Poly-sulfobetaine beschrieben sind und entsprechend das wässrige Phasenverhalten nur für einzelne ausgewählte Polymere bekannt ist, wurde ein Grundverständnis von chemischer Struktur und Phasen¬übergangs¬verhalten durch eine systematische Variation des Substitutionsmusters angestrebt. Die als geeignet erkannten Sulfobetain-Monomere wurden mit dem nicht-ionischen Monomer N-Isopropyl-methacrylamid („NIPMAM“) zu Blockcopolymeren von unterschiedlicher Größe und Blocklängen zusammengefügt. Die neuen Blockcopolymere wurden anschließend bezüglich der Lage der Phasenübergänge mit Trübheitsmessungen untersucht. Es wurden 2 Serien neuer zwitterionischer Monomere synthetisiert, deren Struktur den sehr gut untersuchten 3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate („SPE“) und 3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate („SPP“) ähnlich ist. Aus den Monomeren wurden fluoreszenz-markierte Homopolymere mit unterschiedlichen Molmassen mittels der Reversiblen Additions-Fragmentierungs Kettenübertragungs (RAFT) – Polymerisation unter Verwendung eines geeigneten RAFT Reagenzes synthetisiert. Die Poly¬sulfobetaine wurden bezüglich ihrer Löslichkeit in Wasser, in deuteriertem Wasser und in Salzlösungen untersucht. Ihr wässriges Phasenverhalten mit einem UCST-Übergang ist stark abhängig von ihrer Molmasse und von der Polymerkonzentration der untersuchten Lösung. Auffällig ist, dass die Phasenübergangstemperatur in D2O deutlich höher liegt als in H2O. Des Weiteren konnten die Löslichkeit und Phasen-übergangstemperatur durch Salzzusatz effektiv moduliert werden. Prinzipiell stellte sich bei den untersuchten Anionen heraus, dass das Einsalzen bzw. das Aussalzen der empirischen Hofmeister Serie folgt. Dabei hängen die individuellen Effekte sehr stark von der Konzentration und von der Art des Salzes, aber auch in nicht-trivialer Weise von der detaillierten zwitterionischen Struktur stark ab. Durch die systematische Variation der Monomerstruktur wurden interessante Tendenzen offenbar. Die Methacrylamid-basierte Polysulfobetaine besitzen eine höhere Phasenübergangstemperatur als ihre Methacrylat-basierten Analoga. Die Vergrößerung der Distanz zwischen Polymerrückrat und der zwitterionischen Gruppe von 2 auf 3 Methylengruppen führt zu einer Erniedrigung der Phasenübergangstemperatur. Polysulfobetaine mit aliphatischen Resten (Methyl-gruppen) am Ammonium-Ion haben eine höhere Phasenübergangstemperatur als ihre Analoga, in denen der Ammonium-Stickstoff Teil eines Heterozyklus ist. Als letzte Strukturvariable wurde die Distanz zwischen Kation und Anion von 3 auf 4 Methylengruppen vergrößert; diese Änderung führt zu einer massiven Erhöhung der Phasenübergangstemperatur. Die Polysulfobetaine wurden verwendet, um mit dem nicht-ionischen Monomer NIPMAM wasserlösliche Blockcopolymere mittels der RAFT Polymerisation herzustellen. Diese Blockcopolymere besitzen doppelt thermisch-responsives Verhalten (mit einem UCST- und einem LCST-Übergang). Die Besonderheit einer solchen Konstellation ist, dass eine Strukturinversion der solvophoben Aggregate induziert werden kann. Daher werden solche Blockcopolymer-Assoziate auch als „schizophrene Mizellen“ bezeichnet. Je nach der relativen Lage der beiden Phasenübergänge, die sich durch Polymerkonzentration oder durch Salzzusatz einstellen lässt, läuft die Strukturinversion über ein molekular gelöstes oder über ein unlösliches Zwischenstadium ab. Der Polysulfobetain-Block bildet bei niedriger Temperatur Aggregate, die durch den gelösten poly(NIPMAM)-Block in Lösung gehalten werden. Dahingegen bildet der poly(NIPMAM)-Block bei hoher Temperatur Aggregate, welche ihrerseits durch den gelösten Polysulfobetain-Block in Lösung gehalten werden. Somit werden „schizophrene“ Aggregate in Wasser erzeugt, die fähig sind, reversibel ihr „Inneres“ nach „Außen“ und umgekehrt zu schalten durch Nutzen eines einfachen thermischen Impulses. KW - switchable block copolymer KW - polyzwitterion KW - polysulfobetaine KW - thermoresponsive polymers KW - schizophrenic behavior KW - LCST and UCST KW - electrolyte sensitivity KW - zweifach schaltbare Blockcopolymere KW - Polyzwitterion KW - Polysulfobetaine KW - thermoresponsive Polymere KW - schizophrenes Verhalten KW - LCST und UCST KW - Elektrolytempfindlichkeit Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-101372 ER - TY - JOUR A1 - Hildebrand, Viet A1 - Laschewsky, Andre A1 - Wischerhoff, Erik T1 - Modulating the solubility of zwitterionic poly((3methacrylamidopropyl)ammonioalkane sulfonate)s in water and aqueous salt solutions via the spacer group separating the cationic and the anionic moieties JF - Polymer Chemistry N2 - Complementary to the well-established zwitterionic monomer 3-((3-methacrylamidopropyl) dimethylammonio) propane-1-sulfonate (SPP), the closely related monomers 2-hydroxy-3-((3-methacrylamidopropyl) dimethylammonio) propane-1-sulfonate (SHPP) and 4-((3-methacrylamidopropyl) dimethylammonio)butane- 1-sulfonate (SBP) were synthesised and polymerised by reversible addition-fragmentation chain transfer (RAFT) polymerisation, using a fluorophore labeled RAFT agent. The polyzwitterions of systematically varied molar masses were characterised with respect to their solubility in water and aqueous salt solutions. Both poly(sulfobetaine)s show thermoresponsive behaviour in water, exhibiting phase separation at low temperatures and upper critical solution temperatures (UCST). For both polySHPP and polySBP, cloud points depend notably on the molar mass, and are much higher in D2O than in H2O. Also, the cloud points are effectively modulated by the addition of salts. The individual effects can be in parts correlated to the Hofmeister series for the anions studied. Still, they depend in a complex way on the concentration and the nature of the added electrolytes, on the one hand, and on the detailed nature of the spacer group separating the anionic and the cationic charges of the betaine moiety, on the other hand. As anticipated, the cloud points of polySBP are much higher than the ones of the analogous polySPP of identical molar mass. Surprisingly, the cloud points of polySHPP are also somewhat higher than the ones of their polySPP analogues, despite the additional hydrophilic hydroxyl group present in the spacer separating the ammonium and the sulfonate moieties. These findings point to a complicated interplay of the various hydrophilic components in polyzwitterions with respect to their overall hydrophilicity. Thus, the spacer group in the betaine moiety proves to be an effective additional molecular design parameter, apparently small variations of which strongly influence the phase behaviour of the polyzwitterions in specific aqueous environments. Y1 - 2016 U6 - https://doi.org/10.1039/c5py01642h SN - 1759-9954 SN - 1759-9962 VL - 7 SP - 731 EP - 740 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Päch, Michael A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates) N2 - A series of new sulfobetaine methacrylates, including nitrogen-containing saturated heterocycles, was synthesised by systematically varying the substituents of the zwitterionic group. Radical polymerisation via the RAFT (reversible addition–fragmentation chain transfer) method in trifluoroethanol proceeded smoothly and was well controlled, yielding polymers with predictable molar masses. Molar mass analysis and control of the end-group fidelity were facilitated by end-group labeling with a fluorescent dye. The polymers showed distinct thermo-responsive behaviour of the UCST (upper critical solution temperature) type in an aqueous solution, which could not be simply correlated to their molecular structure via an incremental analysis of the hydrophilic and hydrophobic elements incorporated within them. Increasing the spacer length separating the ammonium and the sulfonate groups of the zwitterion moiety from three to four carbons increased the phase transition temperatures markedly, whereas increasing the length of the spacer separating the ammonium group and the carboxylate ester group on the backbone from two to three carbons provoked the opposite effect. Moreover, the phase transition temperatures of the analogous polyzwitterions decreased in the order dimethylammonio > morpholinio > piperidinio alkanesulfonates. In addition to the basic effect of the polymers’ precise molecular structure, the concentration and the molar mass dependence of the phase transition temperatures were studied. Furthermore, we investigated the influence of added low molar mass salts on the aqueous-phase behaviour for sodium chloride and sodium bromide as well as sodium and ammonium sulfate. The strong effects evolved in a complex way with the salt concentration. The strength of these effects depended on the nature of the anion added, increasing in the order sulfate < chloride < bromide, thus following the empirical Hofmeister series. In contrast, no significant differences were observed when changing the cation, i.e. when adding sodium or ammonium sulfate. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 298 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102028 ER - TY - JOUR A1 - Hiltl, Stephanie A1 - Böker, Alexander T1 - Wetting Phenomena on (Gradient) Wrinkle Substrates JF - Langmuir N2 - We characterize the wetting behavior of nano structured wrinkle and gradient wrinkle substrates. Different contact angles on both sides of a water droplet after deposition on a gradient sample induce the self-propelled motion of the liquid toward smaller wrinkle dimensions. The droplet motion is self-limited by the contact angles balancing out. Because of the correlation between droplet motion and contact angles, we investigate the wetting behavior of wrinkle substrates with constant dimensions (wavelengths of 400-1200 nm). Contact angles of water droplets on those substrates increase with increasing dimensions of the underlying substrate. The results are independent of the two measurement directions, parallel and perpendicular to the longitudinal axis of the nanostructure. The presented findings may be considered for designing microfluidic or related devices and initiate ideas for the development of further wrinkle applications. Y1 - 2016 U6 - https://doi.org/10.1021/acs.langmuir.6b02364 SN - 0743-7463 VL - 32 SP - 8882 EP - 8888 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Holert, Johannes A1 - Yücel, Onur A1 - Jagmann, Nina A1 - Prestel, Andreas A1 - Möller, Heiko Michael A1 - Philipp, Bodo T1 - Identification of bypass reactions leading to the formation of one central steroid degradation intermediate in metabolism of different bile salts in Pseudomonas sp strain Chol1 JF - Environmental microbiology Y1 - 2016 U6 - https://doi.org/10.1111/1462-2920.13192 SN - 1462-2912 SN - 1462-2920 VL - 18 SP - 3373 EP - 3389 PB - Wiley-Blackwell CY - Hoboken ER - TY - GEN A1 - Hoogenboom, Richard A1 - Schlaad, Helmut T1 - Thermoresponsive poly(2-oxazoline)s, polypeptoids, and polypeptides N2 - This review covers the recent advances in the emerging field of thermoresponsive polyamides or polymeric amides, i.e., poly(2-oxazoline)s, polypeptoids, and polypeptides, with a specific focus on structure–thermoresponsive property relationships, self-assembly, and applications. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 328 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-395022 ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Bai, Wubin A1 - Nunns, Adam A1 - Gwyther, Jessica A1 - Manners, Ian A1 - Böker, Alexander A1 - Tsarkova, Larisa A1 - Ross, Caroline A. T1 - Electric field manipulated nanopatterns in thin films of metalorganic 3-miktoarm star terpolymers JF - Soft matter N2 - We report the effect of electric field on the morphological transitions and ordering behavior of polyferrocenylethylmethylsilane block (PFEMS)-containing copolymers. By analyzing structures in solvent-annealed films of metalorganic sphere-and cylinder-forming diblock copolymers, as well as of 3-miktoarm polyisoprene-arm-polystyrene-arm-PFEMS (3 mu-ISF) terpolymers, we decouple two types of responses to the electric field: morphological transformations as a result of an increase in the volume fraction of the PFEMS block by oxidation of the ferrocenyl groups, and the orientation of the dielectric interfaces of microdomains parallel to the electric field vector. In the case of 3m-ISF, the former effect dominates at high electric field strengths which results in an unexpected cylinder-to-sphere transition, leading to a well-ordered hexagonal dot pattern. Our results demonstrate multiple tunability of ordered microdomain morphologies, suggesting future applications in nanofabrication and surface patterning. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm00451b SN - 1744-683X SN - 1744-6848 VL - 12 SP - 4866 EP - 4874 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Pester, Christian A1 - Ruppel, Markus A1 - Jung, Maike A1 - Zimmermann, Marc A1 - Böker, Alexander T1 - Reorientation mechanisms of block copolymer/CdSe quantum dot composites under application of an electric field JF - Soft matter N2 - Time- and temperature-resolved in situ birefringence measurements were applied to analyze the effect of nanoparticles on the electric field-induced alignment of a microphase separated solution of poly(styrene)-block-poly(isoprene) in toluene. Through the incorporation of isoprene-confined CdSe quantum dots the reorientation behavior is altered. Particle loading lowers the order-disorder transition temperature, and increases the defect density, favoring nucleation and growth as an alignment mechanism over rotation of grains. The temperature dependent alteration in the reorientation mechanism is analyzed via a combination of birefringence and synchrotron SAXS. The detailed understanding of the effect of nanoparticles on the reorientation mechanism is an important prerequisite for optimization of electricfield-induced alignment of block copolymer/nanoparticle composites where the block copolymer guides the nanoparticle self-assembly into anisotropic structures. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm01073c SN - 1744-683X SN - 1744-6848 VL - 12 SP - 8417 EP - 8424 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Khadem, S. M. J. A1 - Hille, Carsten A1 - Löhmannsröben, Hans-Gerd A1 - Sokolov, Igor M. T1 - What information is contained in the fluorescence correlation spectroscopy curves, and where JF - Physical review : E, Statistical, nonlinear and soft matter physics Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevE.94.022407 SN - 2470-0045 SN - 2470-0053 VL - 94 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Klaper, Matthias A1 - Wessig, Pablo A1 - Linker, Torsten T1 - Base catalysed decomposition of anthracene endoperoxide JF - Chemical communications N2 - Catalytic amounts of a weak base are sufficient to induce the decomposition of anthracene endoperoxides to anthraquinone. The mechanism has been elucidated by isolation of intermediates in combination with DFT calculations. The whole process is suitable for the convenient generation of hydrogen peroxide under very mild conditions. Y1 - 2016 U6 - https://doi.org/10.1039/c5cc08606j SN - 1359-7345 SN - 1364-548X VL - 52 SP - 1210 EP - 1213 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Y-aromaticity - existing: yes or no? An answer given on the magnetic criterion (TSNMRS) JF - Tetrahedron N2 - The spatial magnetic properties (Through Space NMR Shieldings - TSNMRS) of a number of Y-shaped structures possessing 4n+2 pi-electrons (i.a. the trimethylenemethane ions TMM2+, TMM2-, the guanidinium cation, substituted and hetero analogues) have been computed, visualized as Isochemical Shielding Surfaces (ICSS) of various size and direction, were examined subject to present Y-aromaticity and the results compared with energetic and geometric criteria obtained already. (C) 2016 Elsevier Ltd. All rights reserved. KW - Y-aromaticity KW - pi-Electron delocalization KW - Theoretical calculations KW - ICSS KW - TSNMRS Y1 - 2016 U6 - https://doi.org/10.1016/j.tet.2016.02.020 SN - 0040-4020 VL - 72 SP - 1675 EP - 1685 PB - Elsevier CY - Oxford ER - TY - THES A1 - Klier, Dennis Tobias T1 - Upconversion luminescence in Er-codoped NaYF4 nanoparticles T1 - Frequenzaufkonversion in Er-codotierten NaYF4 Nanopartikeln BT - fundamental photophysics and optimization for life science applications BT - fundamentale Photophysik und Optimierung für Anwendungen in den Lebenswissenschaften N2 - In the context of an increasing population of aging people and a shift of medical paradigm towards an individualized medicine in health care, nanostructured lanthanides doped sodium yttrium fluoride (NaYF4) represents an exciting class of upconversion nanomaterials (UCNM) which are suitable to bring forward developments in biomedicine and -biodetection. Despite the fact that among various fluoride based upconversion (UC) phosphors lanthanide doped NaYF4 is one of the most studied upconversion nanomaterial, many open questions are still remaining concerning the interplay of the population routes of sensitizer and activator electronic states involved in different luminescence upconversion photophysics as well as the role of phonon coupling. The collective work aims to explore a detailed understanding of the upconversion mechanism in nanoscaled NaYF4 based materials co-doped with several lanthanides, e.g. Yb3+ and Er3+ as the "standard" type upconversion nanoparticles (UCNP) up to advanced UCNP with Gd3+ and Nd3+. Especially the impact of the crystal lattice structure as well as the resulting lattice phonons on the upconversion luminescence was investigated in detail based on different mixtures of cubic and hexagonal NaYF4 nanoscaled crystals. Three synthesis methods, depending on the attempt of the respective central spectroscopic questions, could be accomplished in the following work. NaYF4 based upconversion nanoparticles doped with several combination of lanthanides (Yb3+, Er3+, Gd3+ and Nd3+) were synthesized successfully using a hydrothermal synthesis method under mild conditions as well as a co-precipitation and a high temperature co-precipitation technique. Structural information were gathered by means of X-ray diffraction (XRD), electron microscopy (TEM), dynamic light scattering (DLS), Raman spectroscopy and inductively coupled plasma atomic emission spectrometry (ICP-OES). The results were discussed in detail with relation to the spectroscopic results. A variable spectroscopic setup was developed for multi parameter upconversion luminescence studies at various temperature 4 K to 328 K. Especially, the study of the thermal behavior of upconversion luminescence as well as time resolved area normalized emission spectra were a prerequisite for the detailed understanding of intramolecular deactivation processes, structural changes upon annealing or Gd3+ concentration, and the role of phonon coupling for the upconversion efficiency. Subsequently it became possible to synthesize UCNP with tailored upconversion luminescence properties. In the end, the potential of UCNP for life science application should be enunciated in context of current needs and improvements of a nanomaterial based optical sensors, whereas the "standard" UCNP design was attuned according to the special conditions in the biological matrix. In terms of a better biocompatibility due to a lower impact on biological tissue and higher penetrability for the excitation light. The first step into this direction was to use Nd3+ ions as a new sensitizer in tridoped NaYF4 based UCNP, whereas the achieved absolute and relative temperature sensitivity is comparable to other types of local temperature sensors in the literature. N2 - Ziel der Arbeit war es ein erweitertes Verständnis des Mechanismus der Lichtaufkonversion, sowie dessen gezielte Manipulation in verschiedenen Nanomaterialien auf Natriumyttrium-fluoridbasis zu erlangen. Die optischen Eigenschaften werden dabei durch eine gezielte Zusammenstellung verschiedener Lanthanoidionen hervorgerufen, welche während der Synthese in die Materialien eingebracht werden. Der Fokus lag hierbei in der Aufklärung des Zusammenspiels zwischen der Struktur der Materialien und deren Lichtaufkonver-sionsvermögen sowie dem Erlangen eines generellen Verständnisses der einzelnen Teilschritte des Lichtaufkonversionsmechanismus. Dabei wird das Licht, welches nach Anregung der Lanthanoidionen durch einen Laser von diesen emittiert wird, hinsichtlich der Farbzusammensetzung und des Abklingverhaltens der Lumineszenz untersucht. Diese Erkenntnisse geben sowohl einen Einblick in die verschiedenen Teilschritte des Lichtaufkonversionsmechanismus, als auch deren Korrelation zur Struktur der Nanomaterialien. Während der Arbeit wurde ein variabler Messplatz mit einer wellenlängendurchstimmbaren Anregungslichtquelle, einer Detektionseinheit mit hervorragender spektraler und zeitlicher Auflösung für die Messung des emittierten Lichtes sowie einer Temperiereinheit, mit der die Proben in einem Temperaturbereich von 4 Kelvin (-269,15 °C) bis 328 Kelvin (50 °C) temperiert werden können, aufgebaut. Die Proben wurden mithilfe der modernen Kopräzipitations- und Hydrothermalsynthese in verschiedenen Zusammensetzungen und Oberflächenmodifizierungen hergestellt, um sowohl Partikel für fundamentale Untersuchungen der Lichtaufkonversion verfügbar zu haben, als auch den hohen Anforderungen für Anwendungen in den Lebenswissenschaften gerecht zu werden. Die Reaktion fand bei hohen Temperaturen (160 °C bis 320 °C) unter Schutzgasatmosphäre statt und gewährleistete so die Bildung von hochkristallinen Partikeln, deren Größe stark mit der Synthesetemperatur korreliert. Mithilfe von zeitaufgelösten Lumineszenzuntersuchungen gelang ein sehr detaillierter Einblick in strukturelle Veränderungen der Nanopartikeln, welche durch klassische strukturanalytische Methoden, wie der Röntgenpulverdiffraktometrie, nicht in dem Maße möglich sind. Zudem konnte ein erheblicher Teil dazu beigetragen werden, das komplexe Zusammenspiel von Energietransportmechanismen, Gitterschwingungen und thermisch induzierten Prozessen zu verstehen. Zuletzt wurden, basierend auf der Vielzahl an gewonnenen Erkenntnissen, speziell designte Nanopartikel hergestellt. Die Farbe des Emissionslichts dieser Partikel wies dabei eine hohe Abhängigkeit von der Umgebungstemperatur auf. Auftretende Herausforderungen induziert durch das verwendete Anregungslicht im Nahinfrarotenbereich, wie das Aufheizen oder die zu hohe Absorption der Probe, wurden durch die Erweiterung des Aufkonversionssystems gelöst. Damit konnten beste Voraussetzungen für potentielle Anwendungen, wie zum Beispiel als Nanothermometer geschaffen werden. KW - Nanopartikel KW - nanoparticle KW - Frequenzaufkonversion KW - upconversion KW - Lanthanoide KW - lanthanides Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98486 ER - TY - JOUR A1 - Knight, Joseph W. A1 - Wang, Xiaopeng A1 - Gallandi, Lukas A1 - Dolgounitcheva, Olga A1 - Ren, Xinguo A1 - Ortiz, J. Vincent A1 - Rinke, Patrick A1 - Körzdörfer, Thomas A1 - Marom, Noa T1 - Accurate Ionization Potentials and Electron Affinities of Acceptor Molecules III: A Benchmark of GW Methods JF - Journal of chemical theory and computation N2 - The performance of different GW methods is assessed for a set of 24 organic acceptors. Errors are evaluated with respect to coupled cluster singles, doubles, and perturbative triples [CCSD(T)] reference data for the vertical ionization potentials (IPs) and electron affinities (EAs), extrapolated to the complete basis set limit. Additional comparisons are made to experimental data, where available. We consider fully self-consistent GW (scGW), partial self-consistency in the Green’s function (scGW0), non-self-consistent G0W0 based on several mean-field starting points, and a “beyond GW” second-order screened exchange (SOSEX) correction to G0W0. We also describe the implementation of the self-consistent Coulomb hole with screened exchange method (COHSEX), which serves as one of the mean-field starting points. The best performers overall are G0W0+SOSEX and G0W0 based on an IP-tuned long-range corrected hybrid functional with the former being more accurate for EAs and the latter for IPs. Both provide a balanced treatment of localized vs delocalized states and valence spectra in good agreement with photoemission spectroscopy (PES) experiments. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jctc.5b00871 SN - 1549-9618 SN - 1549-9626 VL - 12 SP - 615 EP - 626 PB - American Chemical Society CY - Washington ER -