@article{BoggioBodenmuellerFrembergetal.2014, author = {Boggio, Jose M. Chavez and Bodenmueller, D. and Fremberg, T. and Haynes, R. and Roth, Martin M. and Eisermann, R. and Lisker, M. and Zimmermann, L. and Boehm, Michael}, title = {Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization}, series = {Journal of the Optical Society of America : B, Optical physics}, volume = {31}, journal = {Journal of the Optical Society of America : B, Optical physics}, number = {11}, publisher = {Optical Society of America}, address = {Washington}, issn = {0740-3224}, doi = {10.1364/JOSAB.31.002846}, pages = {2846 -- 2857}, year = {2014}, abstract = {Dispersion engineering in silicon nitride (SiXNY) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multicladding arrangement. Ultraflat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during fabrication of the SiXNY waveguides are a limitation for obtaining ultraflat dispersion profiles. Single- and multicladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in single-and multicladding waveguides with small refractive index contrast (3\%). A flat dispersion profile with +/- 3.2 ps/nm/km variation over 500 nm is obtained in a multicladding waveguide fabricated with a refractive index contrast of 37\%. Finally, we generate a nearly three-octave supercontinuum in this dispersion flattened multicladding SiXNY waveguide. (C) 2014 Optical Society of America}, language = {en} } @article{MetzlerJeonCherstvyetal.2014, author = {Metzler, Ralf and Jeon, Jae-Hyung and Cherstvy, Andrey G. and Barkai, Eli}, title = {Anomalous diffusion models and their properties}, series = {physical chemistry, chemical physics : PCCP}, volume = {2014}, journal = {physical chemistry, chemical physics : PCCP}, number = {16}, issn = {1463-9076}, doi = {10.1039/c4cp03465a}, pages = {24128 -- 24164}, year = {2014}, abstract = {Modern microscopic techniques following the stochastic motion of labelled tracer particles have uncovered significant deviations from the laws of Brownian motion in a variety of animate and inanimate systems. Such anomalous diffusion can have different physical origins, which can be identified from careful data analysis. In particular, single particle tracking provides the entire trajectory of the traced particle, which allows one to evaluate different observables to quantify the dynamics of the system under observation. We here provide an extensive overview over different popular anomalous diffusion models and their properties. We pay special attention to their ergodic properties, highlighting the fact that in several of these models the long time averaged mean squared displacement shows a distinct disparity to the regular, ensemble averaged mean squared displacement. In these cases, data obtained from time averages cannot be interpreted by the standard theoretical results for the ensemble averages. Here we therefore provide a comparison of the main properties of the time averaged mean squared displacement and its statistical behaviour in terms of the scatter of the amplitudes between the time averages obtained from different trajectories. We especially demonstrate how anomalous dynamics may be identified for systems, which, on first sight, appear to be Brownian. Moreover, we discuss the ergodicity breaking parameters for the different anomalous stochastic processes and showcase the physical origins for the various behaviours. This Perspective is intended as a guidebook for both experimentalists and theorists working on systems, which exhibit anomalous diffusion.}, language = {en} } @article{WessigGerngrossPapeetal.2014, author = {Wessig, Pablo and Gerngroß, Maik and Pape, Simon and Bruhns, Philipp and Weber, Jens}, title = {Novel porous materials based on oligospiroketals (OSK)}, series = {RSC Advances : an international journal to further the chemical sciences}, volume = {2014}, journal = {RSC Advances : an international journal to further the chemical sciences}, number = {4}, issn = {2046-2069}, doi = {10.1039/c4ra04437a}, pages = {31123 -- 31129}, year = {2014}, abstract = {New porous materials based on covalently connected monomers are presented. The key step of the synthesis is an acetalisation reaction. In previous years we used acetalisation reactions extensively to build up various molecular rods. Based on this approach, investigations towards porous polymeric materials were conducted by us. Here we wish to present the results of these studies in the synthesis of 1D polyacetals and porous 3D polyacetals. By scrambling experiments with 1D acetals we could prove that exchange reactions occur between different building blocks (evidenced by MALDI-TOF mass spectrometry). Based on these results we synthesized porous 3D polyacetals under the same mild conditions.}, language = {en} } @article{ZamponiPenfoldNachtegaaletal.2014, author = {Zamponi, Flavio and Penfold, Thomas J. and Nachtegaal, Maarten and L{\"u}bcke, Andrea and Rittmann, Jochen and Milne, Chris J. and Chergui, Majed and van Bokhoven, Jeroen A.}, title = {Probing the dynamics of plasmon-excited hexanethiol-capped gold nanoparticles by picosecond X-ray absorption spectroscopy}, series = {physical chemistry, chemical physics : PCCP}, volume = {2014}, journal = {physical chemistry, chemical physics : PCCP}, number = {16}, issn = {1463-9076}, doi = {10.1039/c4cp03301a}, pages = {23157 -- 23163}, year = {2014}, abstract = {Picosecond X-ray absorption spectroscopy (XAS) is used to investigate the electronic and structural dynamics initiated by plasmon excitation of 1.8 nm diameter Au nanoparticles (NPs) functionalised with 1-hexanethiol. We show that 100 ps after photoexcitation the transient XAS spectrum is consistent with an 8\% expansion of the Au-Au bond length and a large increase in disorder associated with melting of the NPs. Recovery of the ground state occurs with a time constant of ∼1.8 ns, arising from thermalisation with the environment. Simulations reveal that the transient spectrum exhibits no signature of charge separation at 100 ps and allows us to estimate an upper limit for the quantum yield (QY) of this process to be <0.1.}, language = {en} } @article{MeyerMatissekMuelleretal.2014, author = {Meyer, S{\"o}ren and Matissek, M. and M{\"u}ller, Sandra Marie and Taleshi, M. S. and Ebert, Franziska and Francesconi, Kevin A. and Schwerdtle, Tanja}, title = {In vitro toxicological characterisation of three arsenic-containing hydrocarbons}, series = {Metallomics}, volume = {2014}, journal = {Metallomics}, number = {6}, issn = {1756-591X}, doi = {10.1039/c4mt00061g}, pages = {1023 -- 1033}, year = {2014}, abstract = {Arsenic-containing hydrocarbons are one group of fat-soluble organic arsenic compounds (arsenolipids) found in marine fish and other seafood. A risk assessment of arsenolipids is urgently needed, but has not been possible because of the total lack of toxicological data. In this study the cellular toxicity of three arsenic-containing hydrocarbons was investigated in cultured human bladder (UROtsa) and liver (HepG2) cells. Cytotoxicity of the arsenic-containing hydrocarbons was comparable to that of arsenite, which was applied as the toxic reference arsenical. A large cellular accumulation of arsenic, as measured by ICP-MS/MS, was observed after incubation of both cell lines with the arsenolipids. Moreover, the toxic mode of action shown by the three arsenic-containing hydrocarbons seemed to differ from that observed for arsenite. Evidence suggests that the high cytotoxic potential of the lipophilic arsenicals results from a decrease in the cellular energy level. This first in vitro based risk assessment cannot exclude a risk to human health related to the presence of arsenolipids in seafood, and indicates the urgent need for further toxicity studies in experimental animals to fully assess this possible risk.}, language = {en} } @article{UnterbergLeffersHuebneretal.2014, author = {Unterberg, Marlies and Leffers, Larissa and H{\"u}bner, Florian and Humpf, Hans-Ulrich and Lepikhov, Konstantin and Walter, J{\"o}rn and Ebert, Franziska and Schwerdtle, Tanja}, title = {Toxicity of arsenite and thio-DMAV after long-term (21 days) incubation of human urothelial cells: cytotoxicity, genotoxicity and epigenetics}, series = {Toxicology Research}, volume = {3}, journal = {Toxicology Research}, number = {6}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2045-4538}, pages = {456 -- 464}, year = {2014}, abstract = {This study aims to further mechanistically understand toxic modes of action after chronic inorganic arsenic exposure. Therefore long-term incubation studies in cultured cells were carried out, to display chronically attained changes, which cannot be observed in the generally applied in vitro short-term incubation studies. Particularly, the cytotoxic, genotoxic and epigenetic effects of an up to 21 days incubation of human urothelial (UROtsa) cells with pico- to nanomolar concentrations of iAsIII and its metabolite thio-DMAV were compared. After 21 days of incubation, cytotoxic effects were strongly enhanced in the case of iAsIII and might partly be due to glutathione depletion and genotoxic effects on the chromosomal level. These results are in strong contrast to cells exposed to thio-DMAV. Thus, cells seemed to be able to adapt to this arsenical, as indicated among others by an increase in the cellular glutathione level. Most interestingly, picomolar concentrations of both iAsIII and thio-DMAV caused global DNA hypomethylation in UROtsa cells, which was quantified in parallel by 5-medC immunostaining and a newly established, reliable, high resolution mass spectrometry (HRMS)-based test system. This is the first time that epigenetic effects are reported for thio-DMAV; iAsIII induced epigenetic effects occur in at least 8000 fold lower concentrations as reported in vitro before. The fact that both arsenicals cause DNA hypomethylation at really low, exposure-relevant concentrations in human urothelial cells suggests that this epigenetic effect might contribute to inorganic arsenic induced carcinogenicity, which for sure has to be further investigated in future studies.}, language = {en} } @article{GhoshCherstvyMetzler2014, author = {Ghosh, Surya K. and Cherstvy, Andrey G. and Metzler, Ralf}, title = {Non-universal tracer diffusion in crowded media of non-inert obstacles}, series = {Physical Chemistry Chemical Physics}, volume = {3}, journal = {Physical Chemistry Chemical Physics}, number = {17}, editor = {Metzler, Ralf}, publisher = {The Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, pages = {1847 -- 1858}, year = {2014}, abstract = {We study the diffusion of a tracer particle, which moves in continuum space between a lattice of excluded volume, immobile non-inert obstacles. In particular, we analyse how the strength of the tracer-obstacle interactions and the volume occupancy of the crowders alter the diffusive motion of the tracer. From the details of partitioning of the tracer diffusion modes between trapping states when bound to obstacles and bulk diffusion, we examine the degree of localisation of the tracer in the lattice of crowders. We study the properties of the tracer diffusion in terms of the ensemble and time averaged mean squared displacements, the trapping time distributions, the amplitude variation of the time averaged mean squared displacements, and the non-Gaussianity parameter of the diffusing tracer. We conclude that tracer-obstacle adsorption and binding triggers a transient anomalous diffusion. From a very narrow spread of recorded individual time averaged trajectories we exclude continuous type random walk processes as the underlying physical model of the tracer diffusion in our system. For moderate tracer-crowder attraction the motion is found to be fully ergodic, while at stronger attraction strength a transient disparity between ensemble and time averaged mean squared displacements occurs. We also put our results into perspective with findings from experimental single-particle tracking and simulations of the diffusion of tagged tracers in dense crowded suspensions. Our results have implications for the diffusion, transport, and spreading of chemical components in highly crowded environments inside living cells and other structured liquids.}, language = {en} } @article{ShinCherstvyMetzler2014, author = {Shin, Jaeoh and Cherstvy, Andrey G. and Metzler, Ralf}, title = {Kinetics of polymer looping with macromolecular crowding: effects of volume fraction and crowder size}, series = {Soft Matter}, journal = {Soft Matter}, editor = {Metzler, Ralf}, publisher = {The Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, pages = {472 -- 488}, year = {2014}, abstract = {The looping of polymers such as DNA is a fundamental process in the molecular biology of living cells, whose interior is characterised by a high degree of molecular crowding. We here investigate in detail the looping dynamics of flexible polymer chains in the presence of different degrees of crowding. From the analysis of the looping-unlooping rates and the looping probabilities of the chain ends we show that the presence of small crowders typically slows down the chain dynamics but larger crowders may in fact facilitate the looping. We rationalise these non-trivial and often counterintuitive effects of the crowder size on the looping kinetics in terms of an effective solution viscosity and standard excluded volume. It is shown that for small crowders the effect of an increased viscosity dominates, while for big crowders we argue that confinement effects (caging) prevail. The tradeoff between both trends can thus result in the impediment or facilitation of polymer looping, depending on the crowder size. We also examine how the crowding volume fraction, chain length, and the attraction strength of the contact groups of the polymer chain affect the looping kinetics and hairpin formation dynamics. Our results are relevant for DNA looping in the absence and presence of protein mediation, DNA hairpin formation, RNA folding, and the folding of polypeptide chains under biologically relevant high-crowding conditions.}, language = {en} } @article{OmosaAmuguneNdundaetal.2014, author = {Omosa, Leonidah K. and Amugune, Beatrice and Ndunda, Beth and Milugo, Trizah K. and Heydenreich, Matthias and Yenesew, Abiy and Midiwo, Jacob O.}, title = {Antimicrobial flavonoids and diterpenoids from Dodonaea angustifolia}, series = {South African journal of botany : an international interdisciplinary journal for botanical sciences}, volume = {91}, journal = {South African journal of botany : an international interdisciplinary journal for botanical sciences}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0254-6299}, doi = {10.1016/j.sajb.2013.11.012}, pages = {58 -- 62}, year = {2014}, language = {en} } @article{PrimusRitschelSigueenzaetal.2014, author = {Primus, Philipp-Alexander and Ritschel, Thomas and Sigueenza, Pilar Y. and Cauqui, Miguel Angel and Hernandez-Garrido, Juan Carlos and Kumke, Michael Uwe}, title = {High-resolution spectroscopy of europium-doped ceria as a tool to correlate structure and catalytic activity}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {118}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {40}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/jp505467r}, pages = {23349 -- 23360}, year = {2014}, abstract = {Site-selective emission spectra of Eu3+-doped CeO2 nanoparticles up to the D-5(0) - F-7(5) transition were recorded under cryogenic conditions to identify the local structure around the Eu3+ dopants in ceria. It is found that pretreatment conditions are crucial for the redistribution of dopants from a broad variety of environments to six well-defined lattice sites. The influence of the dopant and the host structure on the catalytic activity was investigated. A relationship between structure and reactivity is discussed. It is shown that oxygen transport is most efficient in particles with a pronounced amorphous character.}, language = {en} } @article{SchulzeAppelhansTierschetal.2014, author = {Schulze, Nicole and Appelhans, D. and Tiersch, Brigitte and Koetz, Joachim}, title = {Morphological transformation of vesicles into tubular structures by adding polyampholytes or dendritic glycopolymers}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {457}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2014.06.007}, pages = {326 -- 332}, year = {2014}, abstract = {For the first time tubulating properties of spherical dendritic glycopolymers and linear alternating polyampholytes against non-uniform negatively charged giant vesicles are proven by light microscopy and cryo-scanning electron microscopy study. Real time observation of the morphological transformation from giant vesicles to tubular structures, simulating morphogenesis in living cells, is given by using the cationic and H-bond active dendritic glycopolymer accompanied by reducing the size of the giant vesicles and the evidence of vesicle-vesicle interaction which was only postulated in a previous study. Similar morphogenesis of non-uniform giant vesicles into tubular network structure can be observed by using a polyampholyte in the stretched conformation at pH 9. Pearl necklace and tubular network structure formation are also observed by applying anionic vesicles of significant smaller dimensions with average size dimensions of 35 nm, after adding the polyampholyte at pH 9. However, the fitting accuracy between the functional groups along the backbone chain of the polyampholyte on one side and the vesicle surface on the other side is of high importance for the transformation process by using polyampholytes. The resulting tubular and network structures offer new fields of application as microfluidic transport channels or template phases for the shape controlled formation of nanoparticles. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{CisekTokarzKrouglovetal.2014, author = {Cisek, Richard and Tokarz, Danielle and Krouglov, Serguei and Steup, Martin and Emes, Michael J. and Tetlow, Ian J. and Barzda, Virginijus}, title = {Second harmonic generation mediated by aligned water in starch granules}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {118}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {51}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp508751s}, pages = {14785 -- 14794}, year = {2014}, abstract = {The origin of second harmonic generation (SHG) in starch granules was investigated using ab initio quantum mechanical modeling and experimentally examined using polarization-in, polarization-out (PIPO) second harmonic generation microscopy. Ab initio calculations revealed that the largest contribution to the SHG signal from A- and B-type allomorphs of starch originates from the anisotropic organization of hydroxide and hydrogen bonds mediated by aligned water found in the polymers. The hypothesis was experimentally tested by imaging maize starch granules under various hydration and heat treatment conditions that alter the hydrogen bond network. The highest SHG intensity was found in fully hydrated starch granules, and heat treatment diminished the SHG intensity. The PIPO SHG imaging showed that dried starch granules have a much higher nonlinear optical susceptibility component ratio than fully hydrated granules. In contrast, deuterated starch granules showed a smaller susceptibility component ratio demonstrating that SHG is highly sensitive to the organization of the hydroxyl and hydrogen bond network. The polarization SHG imaging results of potato starch granules, representing starch allomorph B, were compared to those of maize starch granules representing allomorph A. The results showed that the amount of aligned water was higher in the maize granules. Nonlinear microscopy of starch granules provides evidence that varying hydration conditions leads to significant changes in the nonlinear susceptibility ratio as well as the SHG intensity, supporting the hypothesis from ab initio calculations that the dominant contribution to SHG is due to the ordered hydroxide and hydrogen bond network.}, language = {en} } @article{PiekarczykBaldFlosadottiretal.2014, author = {Piekarczyk, Andreas and Bald, Ilko and Flosadottir, Helga D. and Omarsson, Benedikt and Lafosse, Anne and Ingolfsson, Oddur}, title = {Influence of metal ion complexation on the metastable fragmentation of DNA hexamers}, series = {The European physical journal : D, Atomic, molecular, optical and plasma physics}, volume = {68}, journal = {The European physical journal : D, Atomic, molecular, optical and plasma physics}, number = {6}, publisher = {Springer}, address = {New York}, issn = {1434-6060}, doi = {10.1140/epjd/e2014-40838-7}, pages = {7}, year = {2014}, abstract = {Here, we study the metastable decay of 5'-d(TTGCTT) in the presence of 0-6 alkaline metal ions (Li+, Na+, K+, Rb+) and 0-3 alkaline earth metal ions (Mg2+ and Ca2+), which replace the corresponding number of protons in the oligonucleotide. We find that all ions studied here stabilize the oligonucleotide with respect to simple 3'-C-O backbone cleavage, but at the same time these metal ions promote a central oligonucleotide deletion accompanied by a concomitant recombination of the terminal d(TT) groups. We find that the quenching of the 3'-C-O backbone cleavage is not ion specific, since it is due to the removal of the phosphate protons upon replacement with the respective metal ions. The central nucleotide deletion competes with the 3'-C-O backbone cleavage channels and is thus promoted through the replacement of the exchangeable protons against metal ions. However, with increasing positive charge density of the metal ions the yield of the central nucleotide deletion further increases. We attribute this effect to the necessity of sufficient proximity of the terminal d(TT) group to allow for their recombination on this reaction path. Hence, the formation of a reactive conformer is mediated by the metal ions.}, language = {en} } @article{KopyraKellerBald2014, author = {Kopyra, Janina and Keller, A. and Bald, Ilko}, title = {On the role of fluoro-substituted nucleosides in DNA radiosensitization for tumor radiation therapy}, series = {RSC Advances}, volume = {4}, journal = {RSC Advances}, number = {13}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c3ra46735j}, pages = {6825 -- 6829}, year = {2014}, language = {en} } @article{SchmidtBehlLendleinetal.2014, author = {Schmidt, Christian and Behl, Marc and Lendlein, Andreas and Beuermann, Sabine}, title = {Synthesis of high molecular weight polyglycolide in supercritical carbon dioxide}, series = {RSC Advances}, volume = {4}, journal = {RSC Advances}, number = {66}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c4ra06815g}, pages = {35099 -- 35105}, year = {2014}, abstract = {Polyglycolide (PGA) is a biodegradable polymer with multiple applications in the medical sector. Here the synthesis of high molecular weight polyglycolide by ring-opening polymerization of diglycolide is reported. For the first time stabilizer free supercritical carbon dioxide (scCO(2)) was used as a reaction medium. scCO(2) allowed for a reduction in reaction temperature compared to conventional processes. Together with the lowering of monomer concentration and consequently reduced heat generation compared to bulk reactions thermal decomposition of the product occurring already during polymerization is strongly reduced. The reaction temperatures and pressures were varied between 120 and 150 degrees C and 145 to 1400 bar. Tin(II) ethyl hexanoate and 1-dodecanol were used as catalyst and initiator, respectively. The highest number average molecular weight of 31 200 g mol(-1) was obtained in 5 hours from polymerization at 120 degrees C and 530 bar. In all cases the products were obtained as a dry white powder. Remarkably, independent of molecular weight the melting temperatures were always at (219 +/- 2)degrees C.}, language = {en} } @article{GhobadiHeuchelKratzetal.2014, author = {Ghobadi, Ehsan and Heuchel, Matthias and Kratz, Karl and Lendlein, Andreas}, title = {Atomistic simulation of the shape-memory effect in dry and water swollen Poly[(rac-lactide)-co-glycolide] and copolyester urethanes thereof}, series = {Macromolecular chemistry and physics}, volume = {215}, journal = {Macromolecular chemistry and physics}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201300507}, pages = {65 -- 75}, year = {2014}, abstract = {An atomistic molecular dynamics simulation approach is applied to model the influence of urethane linker units as well as the addition of water molecules on the simulated shape-memory properties of poly[(rac-lactide)-co-glycolide] (PLGA) and PLGA-based copolyester urethanes comprising different urethane linkers. The shape-memory performance of these amorphous packing models is explored in a simulated heating-deformation-cooling-heating procedure. Depending on the type of incorporated urethane linker, the mechanical properties of the dry copolyester urethanes are found to be significantly improved compared with PLGA, which can be attributed to the number of intermolecular hydrogen bonds between the urethane units. Good shape-memory properties are observed for all the modeled systems. In the dry state, the shape fixation is found to be improved by implementation of urethane units. After swelling of the copolymer models with water, which results in a reduction of their glass transition temperatures, the relaxation kinetics during unloading and shape recovery are found to be substantially accelerated.}, language = {en} } @article{FriessLendleinWischke2014, author = {Friess, Fabian and Lendlein, Andreas and Wischke, Christian}, title = {Photoinduced synthesis of polyester networks from methacrylate functionalized precursors: analysis of side reactions}, series = {Polymers for advanced technologies}, volume = {25}, journal = {Polymers for advanced technologies}, number = {11}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1042-7147}, doi = {10.1002/pat.3313}, pages = {1285 -- 1292}, year = {2014}, abstract = {Polyester networks can be prepared by ultraviolet (UV)-light-induced radical polymerization of methacrylate functionalized oligo(epsilon-caprolactone)s. The properties and functions of the obtained materials depend on defined network structures and may be altered, if crosslinking would occur by side reactions in other positions than the methacrylate endgroups. In order to explore whether and to which extent such side reactions occur, network synthesis as well as related model reactions were performed in the absence of photoinitiator. Hereby precursor structures (linear and four-arm star-shaped) and reaction conditions (in solution and in the melt) were varied. Unspecific side reactions were found only upon extensive UV irradiation for 60min (26 mW cm(-2)) with minor but detectable alterations of physicochemical properties of the networks. The analysis of model reactions suggested minor photolytic cleavage of ester bonds during polymer network synthesis. However, the effect of these side reactions on network properties and functions appeared to be less relevant than an incomplete precursor integration because of a too short UV irradiation for crosslinking. Copyright (c) 2014 John Wiley \& Sons, Ltd.}, language = {en} } @article{SchwarzeMuellerAstetal.2014, author = {Schwarze, Thomas and M{\"u}ller, Holger and Ast, Sandra and Steinbr{\"u}ck, D{\"o}rte and Eidner, Sascha and Geißler, Felix and Kumke, Michael Uwe and Holdt, Hans-J{\"u}rgen}, title = {Fluorescence lifetime-based sensing of sodium by an optode}, series = {Chemical Communications}, journal = {Chemical Communications}, editor = {Kumke, Michael Uwe}, publisher = {The Royal Society Chemistry}, address = {Cambridge}, issn = {0022-4936}, pages = {14167 -- 14170}, year = {2014}, abstract = {We report a 1,2,3-triazol fluoroionophore for detecting Na+ that shows in vitro enhancement in the Na+-induced fluorescence intensity and decay time. The Na+-selective molecule 1 was incorporated into a hydrogel as a part of a fiber optical sensor. This sensor allows the direct determination of Na+ in the range of 1-10 mM by measuring reversible fluorescence decay time changes.}, language = {en} } @article{BaierMetznerKoerzdoerferetal.2014, author = {Baier, Heiko and Metzner, Philipp and K{\"o}rzd{\"o}rfer, Thomas and Kelling, Alexandra and Holdt, Hans-J{\"u}rgen}, title = {Efficient palladium(II) precatalysts bearing 4,5-dicyanoimidazol-2-ylidene for the Mizoroki-Heck reaction}, series = {European journal of inorganic chemistry : a journal of ChemPubSoc Europe}, journal = {European journal of inorganic chemistry : a journal of ChemPubSoc Europe}, number = {18}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-1948}, doi = {10.1002/ejic.201402040}, pages = {2952 -- 2960}, year = {2014}, abstract = {The new N-heterocyclic carbene (NHC) complex [PdCl2{(CN)(2)IMes}(PPh3)] (2) ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) and the NHC palladacycle [PdCl(dmba){(CN)(2)IMes}] (3) (dmba: N,N-dimethylbenzylamine) have been synthesized by thermolysis of 4,5-dicyano-1,3-dimesityl-2-(pentafluorophenyl) imidazoline (1) in the presence of suitable palladium(II) precursors. The acyclic complex 2 was formed by ligand exchange using the mononuclear precursor [PdCl2(PPh3)(2)] and the palladacycle 3 was formed by cleavage of the dinuclear chloro-bridged precursor [Pd(mu-Cl)(dmba)](2). The new NHC precursor 1-benzyl-4,5-dicyano-2-(pentafluorophenyl)-3-picolylimidazoline (5) was formed by condensation of pentafluorobenzaldehyde with N-benzyl-N'-picolyldiaminomaleonitrile (4). The NHC palladacycle [PdCl2{(CN)(2)IBzPic}] (6) ({(CN)(2)IBzPic}: 1-benzyl-4,5-dicyano-3-picolylimidazol-2-ylidene) was prepared by in situ thermolysis of 5 in the presence of [PdCl2(PhCN)(2)]. The three palladium(II) complexes were characterized by NMR and IR spectroscopy, mass spectrometry and elemental analysis. In addition, the molecular structures of 2 and 3 were determined by X-ray diffraction. The pi-acidity of (CN)(2)IBzPic was compared with (CN)(2)IMes and perviously reported pi-acidic imidazol-2-ylidenes by NBO analysis. The Mizoroki-Heck (MH) reactions of various aryl halides with n-butyl acrylate were performed in the presence of complexes 2, 3 and 6. The new precatalysts showed high activity in the MH reactions giving good-to-excellent product yields with 0.1 mol-\% pre-catalyst. The nature of the catalytically active species of 2, 3 and 6 was investigated by poisoning experiments with mercury and transmission electron microscopy. It was found that palladium nanoparticles formed from the precatalysts were involved in the catalytic process.}, language = {en} } @article{TrautmannLubahnHoldt2014, author = {Trautmann, Michael and Lubahn, Susanne and Holdt, Hans-J{\"u}rgen}, title = {Preparation, characterisation and properties of sulphoxide modified polystyrene resins for solid-phase extraction of Pt-IV, Ru-III and Ru-IV from hydrochloric acid}, series = {Reactive \& functional polymers}, volume = {83}, journal = {Reactive \& functional polymers}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1381-5148}, doi = {10.1016/j.reactfunctpolym.2014.07.001}, pages = {84 -- 97}, year = {2014}, abstract = {New sulphoxide modified resins were synthesized using poly(styrene-co-divinylbenzene) (PS-DVB) as matrix. Infrared spectroscopy and elemental analysis were used for characterisation. Solid-phase extraction of Pt-IV, Ru-III and Ru-IV from acidic chloride solutions was performed via batch experiments. Influence of spacer length between sulphoxide and matrix (ethylene, hexamethylene), substitution of sulphoxide (R-1: ethyl, hexyl, phenyl) and bead size of PS-DVB (spherical beads: d(50) < 155 mu m, d(50) < 80 mu m; powder: d(50) < 30 mu m) on adsorption was investigated subjected to acidity. Experimental results showed that ethyl substituted sulphoxide immobilised onto ground PS-DVB and hexamethylene spacer exhibited best adsorption properties. Different kinetic models and isotherms were fitted to the experimental data to identify extraction mechanism. Pt-IV was quantitative sorbed at [HCl] <= 0.1 mol/L whereas Ru-III and Ru-IV sorption ranged between 90\% and 95\% at [HCl] 5 mol/L. Desorption was reached using a solution of 0.5 M thiourea (Tu) in 0.1 M HCl at 90 degrees C. Separation of Pt-IV and Rum occurred at [HCl] <= 0.1 mol/L whereas Pt-IV was extracted and Ru-III remained in solution. A further separation was achieved by extracting Pt-IV and Ru-IV at 5 M HCl followed by sequential elution of Pt-IV with concentrated HCl and Ru-IV with 0.5 M Tu in 0.1 M HCl at 90 degrees C. 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{SchwarzeMuellerAstetal.2014, author = {Schwarze, Thomas and Mueller, Holger and Ast, Sandra and Steinbr{\"u}ck, Dorte and Eidner, Sascha and Geißler, Felix and Kumke, Michael Uwe and Holdt, Hans-J{\"u}rgen}, title = {Fluorescence lifetime-based sensing of sodium by an optode}, series = {Chemical communications}, volume = {50}, journal = {Chemical communications}, number = {91}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1359-7345}, doi = {10.1039/c4cc06112h}, pages = {14167 -- 14170}, year = {2014}, abstract = {We report a 1,2,3-triazol fluoroionophore for detecting Na+ that shows in vitro enhancement in the Na+-induced fluorescence intensity and decay time. The Na+-selective molecule 1 was incorporated into a hydrogel as a part of a fiber optical sensor. This sensor allows the direct determination of Na+ in the range of 1-10 mM by measuring reversible fluorescence decay time changes.}, language = {en} } @article{SchwarzeGarzTeuchneretal.2014, author = {Schwarze, Thomas and Garz, Andreas and Teuchner, Klaus and Menzel, Ralf and Holdt, Hans-J{\"u}rgen}, title = {Two-photon probes for metal ions based on phenylaza[18]crown-6 ethers and 1,2,3-triazoles as pi-linkers}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {15}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {12}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201402232}, pages = {2436 -- 2439}, year = {2014}, language = {en} } @article{TritschlerZlotnikovKeckeisetal.2014, author = {Tritschler, Ulrich and Zlotnikov, Igor and Keckeis, Philipp and Schlaad, Helmut and C{\"o}lfen, Helmut}, title = {Optical properties of self-organized gold nanorod-polymer hybrid films}, series = {Langmuir}, volume = {30}, journal = {Langmuir}, number = {46}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/la503507u}, pages = {13781 -- 13790}, year = {2014}, abstract = {High fractions of gold nanorods were locally aligned by means of a polymeric liquid crystalline phase. The gold nanorods constituting >80 wt \% of the thin organic-inorganic composite films form a network with side-by-side and end-to-end combinations. Organization into these network structures was induced by shearing gold nanorod-LC polymer dispersions via spin-coating. The LC polymer is a polyoxazoline functionalized with pendent cholesteryl and carboxyl side groups enabling the polymer to bind to the CTAB stabilizer layer of the gold nanorods via electrostatic interactions, thus forming the glue between organic and inorganic components, and to form a chiral nematic lyotropic phase. The self-assembled locally oriented gold nanorod structuring enables control over collective optical properties due to plasmon resonance coupling, reminiscent of enhanced optical properties of natural biomaterials.}, language = {en} } @article{BrosnanSchlaad2014, author = {Brosnan, Sarah M. and Schlaad, Helmut}, title = {Modification of polypeptide materials by Thiol-X chemistry}, series = {Polymer : the international journal for the science and technology of polymers}, volume = {55}, journal = {Polymer : the international journal for the science and technology of polymers}, number = {22}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-3861}, doi = {10.1016/j.polymer.2014.08.067}, pages = {5511 -- 5516}, year = {2014}, abstract = {Thiol-X chemistry has proven to be a valuable toolbox for modification of peptides, proteins, monomers, and polymers. Recently, this has become especially true for the modification of polypeptides (monomers or polymers), which has resulted in a plethora of novel polymers and materials. With this in mind, this highlight focuses on the recent literature concerning the modification of polypeptides by the use of thiol-X chemistry, in particular to synthetic polypeptides either at the monomer or polymer stage modified by thiol-ene, -Michael addition, and -yne chemistries. (C) 2014 Published by Elsevier Ltd.}, language = {en} } @article{SchmidtElizarovBergeretal.2014, author = {Schmidt, Bernd and Elizarov, Nelli and Berger, Ren{\´e} and H{\"o}lter, Frank}, title = {Scope and limitations of the Heck-Matsuda-coupling of phenol diazonium salts and styrenes: a protecting-group economic synthesis of phenolic stilbenes}, issn = {1477-0520}, doi = {10.1039/C3OB40420J}, year = {2014}, abstract = {4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4{\"i}-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior.}, language = {en} } @article{SchoenbornHartke2014, author = {Sch{\"o}nborn, Jan Boyke and Hartke, Bernd}, title = {Photochemical dynamics of Photochemical dynamics of E-methylfurylfulgide - Kinematic effects in photorelaxation dynamics of furylfulgides}, doi = {10.1039/C3CP53495B}, year = {2014}, abstract = {With the present theoretical study of the photochemical switching of E-methylfurylfulgide we contribute an important step towards the understanding of the photochemical processes in furylfulgide-related molecules. We have carried out large-scale, full-dimensional direct semiempirical configuration-interaction surface-hopping dynamics of the photoinduced ring-closure reaction. Simulated static and dynamical UV/Vis-spectra show good agreement with experimental data of the same molecule. By a careful investigation of our dynamical data, we were able to identify marked differences to the dynamics of the previously studied E-isopropylfurylfulgide. With our simulations we can not only reproduce the experimentally observed quantum yield differences qualitatively but we can also pinpoint two reasons for them: kinematics and pre-orientation. With our analysis, we thus offer straightforward molecular explanations for the high sensitivity of the photodynamics towards seemingly minor changes in molecular constitution. Beyond the realm of furylfulgides, these insights provide additional guidance to the rational design of photochemically switchable molecules.}, language = {en} } @article{SchmidtHauke2014, author = {Schmidt, Bernd and Hauke, Sylvia}, title = {Cross metathesis of allyl alcohols: how to suppress and how to promote double bond isomerization}, issn = {1477-0520}, doi = {10.1039/c3ob40167g}, year = {2014}, abstract = {Under standard conditions the cross metathesis of allyl alcohols and methyl acrylate is accompanied by the formation of ketones, resulting from uncontrolled and undesired double bond isomerization. By conducting the CM in the presence of phenol, the catalyst loading and the reaction time required for quantiative conversion can be reduced, and isomerization can be suppressed. On the other hand, consecutive isomerization can be deliberately promoted by evaporating excess methyl acrylate after completing cross metathesis and by adding a base or silane as chemical triggers.}, language = {en} } @article{MagadulaMasimbaTarimoetal.2014, author = {Magadula, Joseph J. and Masimba, Pax J. and Tarimo, Rose B. and Msengwa, Zaituni and Mbwambo, Zakariah H. and Heydenreich, Matthias and Breard, Dimitri and Richomme, Pascal}, title = {Mammea-type coumarins from Mammea usambarensis Verdc.}, series = {Biochemical systematics and ecology}, volume = {56}, journal = {Biochemical systematics and ecology}, publisher = {Elsevier}, address = {Oxford}, issn = {0305-1978}, doi = {10.1016/j.bse.2014.05.004}, pages = {65 -- 67}, year = {2014}, abstract = {Phytochemical investigations of Mammea usambarensis resulted into the isolation a delta-tocotrienol (1) and five known mammea-type coumarins (2-6). Their structures were determined by NMR, IR, and LC-MS spectroscopic methods and by comparison of their spectral and physical data with those reported previously in the literature. The presence of these compounds is consistent with the compound classes reported from other members of the genus Mammal. Compound 6 is isolated from the Mammea genus for the first time. This is the new source of mammea-type coumarin compounds while the chemotaxonomic significance of this investigation is summarized. (C) 2014 Elsevier Ltd. All rights reserved.}, language = {en} } @article{HasinovicFribergKovachetal.2014, author = {Hasinovic, H. and Friberg, S. E. and Kovach, Ildyko and Koetz, Joachim}, title = {Destabilization of a dual emulsion to form a Janus emulsion}, series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, volume = {292}, journal = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, number = {9}, publisher = {Springer}, address = {New York}, issn = {0303-402X}, doi = {10.1007/s00396-014-3263-3}, pages = {2319 -- 2324}, year = {2014}, abstract = {A vegetable oil (VO) was added to an emulsion of silicone oil in water (SO/W) with mixing limited to once turning the test tube upside down. Initially, the VO was dispersed into virtually centimeter-sized drops and the emulsion contained effectively no Janus drops, while after 1 h of agitation at a low level to prevent creaming, drops of 50-100-mu m size of the two oils were observed: in addition to an insignificant number of Janus drops. The topology of the latter showed them to emanate from flocculated individual drops of the two oils, but with no discernible effect by the interfacial tension equilibrium on the drop topology. Continued gentle mixing gave increasing fraction of Janus drops of increased size with a topology gradually approaching the one expected from the interfacial equilibrium at the contact line. The spontaneous formation of Janus drops indicated a reduction of the interfacial free energy in the process and the interfacial energy difference between separate and Janus drops was calculated for an appropriate range of interfacial tensions and for all oil fractions. The calculations enabled a distinction of the decrease due to interfacial area changes from the reduction of interfacial tensions per se, with the latter only a minor fraction.}, language = {en} } @article{PlehnMegowMay2014, author = {Plehn, Thomas and Megow, J{\"o}rg and May, Volkhard}, title = {Concerted charge and energy transfer processes in a highly flexible fullerene-dye system: a mixed quantum-classical study}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {25}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp01081g}, pages = {12949 -- 12958}, year = {2014}, abstract = {Photoinduced excitation energy transfer and accompanying charge separation are elucidated for a supramolecular system of a single fullerene covalently linked to six pyropheophorbide-a dye molecules. Molecular dynamics simulations are performed to gain an atomistic picture of the architecture and the surrounding solvent. Excitation energy transfer among the dye molecules and electron transfer from the excited dyes to the fullerene are described by a mixed quantum-classical version of the Forster rate and the semiclassical Marcus rate, respectively. The mean characteristic time of energy redistribution lies in the range of 10 ps, while electron transfer proceeds within 150 ps. In between, on a 20 to 50 ps time-scale, conformational changes take place in the system. This temporal hierarchy of processes guarantees efficient charge separation, if the structure is exposed to a solvent. The fast energy transfer can adopt the dye excitation to the actual conformation. In this sense, the probability to achieve charge separation is large enough since any dominance of unfavorable conformations that exhibit a large dye-fullerene distance is circumvented. And the slow electron transfer may realize an averaging with respect to different conformations. To confirm the reliability of our computations, ensemble measurements on the charge separation dynamics are simulated and a very good agreement with the experimental data is obtained.}, language = {en} } @article{ErmeydanCabaneHassetal.2014, author = {Ermeydan, Mahmut Ali and Cabane, Etienne and Hass, Philipp and Koetz, Joachim and Burgert, Ingo}, title = {Fully biodegradable modification of wood for improvement of dimensional stability and water absorption properties by poly(epsilon-caprolactone) grafting into the cell walls}, series = {Green chemistry : an international journal and green chemistry resource}, volume = {16}, journal = {Green chemistry : an international journal and green chemistry resource}, number = {6}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9262}, doi = {10.1039/c4gc00194j}, pages = {3313 -- 3321}, year = {2014}, abstract = {Materials derived from renewable resources are highly desirable in view of more sustainable manufacturing. Among the available natural materials, wood is one of the key candidates, because of its excellent mechanical properties. However, wood and wood-based materials in engineering applications suffer from various restraints, such as dimensional instability upon humidity changes. Several wood modification treatments increase water repellence, but the insertion of hydrophobic polymers can result in a composite material which cannot be considered as renewable anymore. In this study, we report on the grafting of the fully biodegradable poly(epsilon-caprolactone) (PCL) inside the wood cell walls by Sn(Oct)(2) catalysed ring-opening polymerization (ROP). The presence of polyester chains within the wood cell wall structure is monitored by confocal Raman imaging and spectroscopy as well as scanning electron microscopy. Physical tests reveal that the modified wood is more hydrophobic due to the bulking of the cell wall structure with the polyester chains, which results in a novel fully biodegradable wood material with improved dimensional stability.}, language = {en} } @article{SarauliXuDietzeletal.2014, author = {Sarauli, David and Xu, Chenggang and Dietzel, Birgit and Schulz, Burkhard and Lisdat, Fred}, title = {A multilayered sulfonated polyaniline network with entrapped pyrroloquinoline quinone-dependent glucose dehydrogenase: tunable direct bioelectrocatalysis}, series = {Journal of materials chemistry : B, Materials for biology and medicine}, volume = {2}, journal = {Journal of materials chemistry : B, Materials for biology and medicine}, number = {21}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2050-750X}, doi = {10.1039/c4tb00336e}, pages = {3196 -- 3203}, year = {2014}, abstract = {A feasible approach to construct multilayer films of sulfonated polyanilines - PMSA1 and PABMSA1 containing different ratios of aniline, 2-methoxyaniline-5-sulfonic acid (MAS) and 3-aminobenzoic acid (AB), with the entrapped redox enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) on Au and ITO electrode surfaces, is described. The formation of layers has been followed and confirmed by electrochemical impedance spectroscopy (EIS), which demonstrates that the multilayer assembly can be achieved in a progressive and uniform manner. The gold and ITO electrodes subsequently modified with PMSA1:PQQ-GDH and PABMSA1 films are studied by cyclic voltammetry (CV) and UV-Vis spectroscopy which show a significant direct bioelectrocatalytical response to the oxidation of the substrate glucose without any additional mediator. This response correlates linearly with the number of deposited layers. Furthermore, the constructed polymer/enzyme multilayer system exhibits a rather good long-term stability, since the catalytic current response is maintained for more than 60\% of the initial value even after two weeks of storage. This verifies that a productive interaction of the enzyme embedded in the film of substituted polyaniline can be used as a basis for the construction of bioelectronic units, which are useful as indicators for processes liberating glucose and allowing optical and electrochemical transduction.}, language = {en} } @article{SangoroIacobAgapovetal.2014, author = {Sangoro, Joshia R. and Iacob, C. and Agapov, A. L. and Wang, Yangyang and Berdzinski, Stefan and Rexhausen, Hans and Strehmel, Veronika and Friedrich, C. and Sokolov, A. P. and Kremer, F.}, title = {Decoupling of ionic conductivity from structural dynamics in polymerized ionic liquids}, series = {Soft matter}, volume = {10}, journal = {Soft matter}, number = {20}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c3sm53202j}, pages = {3536 -- 3540}, year = {2014}, abstract = {Charge transport and structural dynamics in low molecular weight and polymerized 1-vinyl-3-pentylimidazolium bis(trifluoromethylsulfonyl) imide ionic liquids (ILs) are investigated by a combination of broadband dielectric spectroscopy, dynamic mechanical spectroscopy and differential scanning calorimetry. While the dc conductivity and fluidity exhibit practically identical temperature dependence for the non-polymerized IL, a significant decoupling of ionic conduction from structural dynamics is observed for the polymerized IL. In addition, the dc conductivity of the polymerized IL exceeds that of its molecular counterpart by four orders of magnitude at their respective calorimetric glass transition temperatures. This is attributed to the unusually high mobility of the anions especially at lower temperatures when the structural dynamics is significantly slowed down. A simple physical explanation of the possible origin of the remarkable decoupling of ionic conductivity from structural dynamics is proposed.}, language = {en} } @article{CywinskiNonoCharbonniereetal.2014, author = {Cywinski, Piotr J. and Nono, Katia Nchimi and Charbonniere, Loic J. and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {13}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c3cp54883j}, pages = {6060 -- 6067}, year = {2014}, abstract = {A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved Forster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surfacefunctionalised with streptavidins. The permanent spatial donor-acceptor proximity is assured through strong and stable biotin-streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with Forster theory, Forsterradii (R0) were found to be around 60 angstrom for organic dyes and around 105 angstrom for QDs. The FRET efficiency (Z) reached 80\% and 25\% for dye and QD acceptors, respectively. Physical donor-acceptor distances (r) have been determined in the range 45-60 angstrom for organic dye acceptors, while for acceptor QDs between 120 angstrom and 145 angstrom. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing.}, language = {en} } @article{BauerGodecMetzler2014, author = {Bauer, Maximilian and Godec, Aljaz and Metzler, Ralf}, title = {Diffusion of finite-size particles in two-dimensional channels with random wall configurations}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {13}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c3cp55160a}, pages = {6118 -- 6128}, year = {2014}, abstract = {Diffusion of chemicals or tracer molecules through complex systems containing irregularly shaped channels is important in many applications. Most theoretical studies based on the famed Fick-Jacobs equation focus on the idealised case of infinitely small particles and reflecting boundaries. In this study we use numerical simulations to consider the transport of finite-size particles through asymmetrical two-dimensional channels. Additionally, we examine transient binding of the molecules to the channel walls by applying sticky boundary conditions. We consider an ensemble of particles diffusing in independent channels, which are characterised by common structural parameters. We compare our results for the long-time effective diffusion coefficient with a recent theoretical formula obtained by Dagdug and Pineda}, language = {en} } @article{FudickarLinker2014, author = {Fudickar, Werner and Linker, Torsten}, title = {Intermediates in the formation and thermolysis of peroxides from oxidations with singlet oxygen}, series = {Australian journal of chemistry}, volume = {67}, journal = {Australian journal of chemistry}, number = {3}, publisher = {CSIRO}, address = {Clayton}, issn = {0004-9425}, doi = {10.1071/CH13423}, pages = {320 -- 327}, year = {2014}, abstract = {Herein we describe the recent mechanistic understandings of the singlet oxygen ene reaction to give hydroperoxides and the [4+2] cycloaddition affording endoperoxides. Both experimental findings and theoretical work conclude in the formation of intermediates structurally similar to perepoxides during the ene reaction. Such intermediates mainly control the regio- and stereoselectivities of this reaction class. For the [4+2] cycloaddition, both a synchronous concerted reaction (benzene, naphthalenes) and a stepwise reaction with a non-symmetric zwitterionic intermediate (larger acenes) have been found. The thermolysis of endoperoxides derived from acenes proceeds stepwise for anthracenes, but in a concerted manner for less stable adducts such as naphthalene.}, language = {en} } @article{ErmeydanCabaneGierlingeretal.2014, author = {Ermeydan, Mahmut Ali and Cabane, Etienne and Gierlinger, Notburga and Koetz, Joachim and Burgert, Ingo}, title = {Improvement of wood material properties via in situ polymerization of styrene into tosylated cell walls}, series = {RSC Advances}, volume = {4}, journal = {RSC Advances}, number = {25}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c4ra00741g}, pages = {12981 -- 12988}, year = {2014}, abstract = {As an engineering material derived from renewable resources, wood possesses excellent mechanical properties in view of its light weight but also has some disadvantages such as low dimensional stability upon moisture changes and low durability against biological attack. Polymerization of hydrophobic monomers in the cell wall is one of the potential approaches to improve the dimensional stability of wood. A major challenge is to insert hydrophobic monomers into the hydrophilic environment of the cell walls, without increasing the bulk density of the material due to lumen filling. Here, we report on an innovative and simple method to insert styrene monomers into tosylated cell walls (i.e. -OH groups from natural wood polymers are reacted with tosyl chloride) and carry out free radical polymerization under relatively mild conditions, generating low wood weight gains. In-depth SEM and confocal Raman microscopy analysis are applied to reveal the distribution of the polystyrene in the cell walls and the lumen. The embedding of polystyrene in wood results in reduced water uptake by the wood cell walls, a significant increase in dimensional stability, as well as slightly improved mechanical properties measured by nanoindentation.}, language = {en} } @article{JeonChechkinMetzler2014, author = {Jeon, Jae-Hyung and Chechkin, Aleksei V. and Metzler, Ralf}, title = {Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {30}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp02019g}, pages = {15811 -- 15817}, year = {2014}, abstract = {Anomalous diffusion is frequently described by scaled Brownian motion (SBM), a Gaussian process with a power-law time dependent diffusion coefficient. Its mean squared displacement is < x(2)(t) similar or equal to 2K(t)t with K(t) similar or equal to t(alpha-1) for 0 < alpha < 2. SBM may provide a seemingly adequate description in the case of unbounded diffusion, for which its probability density function coincides with that of fractional Brownian motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a significant amplitude scatter of the time averaged mean squared displacement. More severely, we demonstrate that under confinement, the dynamics encoded by SBM is fundamentally different from both fractional Brownian motion and continuous time random walks. SBM is highly non-stationary and cannot provide a physical description for particles in a thermalised stationary system. Our findings have direct impact on the modelling of single particle tracking experiments, in particular, under confinement inside cellular compartments or when optical tweezers tracking methods are used.}, language = {en} } @article{HildebrandLaschewskyZehm2014, author = {Hildebrand, Viet and Laschewsky, Andr{\´e} and Zehm, Daniel}, title = {On the hydrophilicity of polyzwitterion poly (N, N-dimethyl-N(3-(methacrylamido)propyl)ammoniopropane sulfonate) in water, deuterated water, and aqueous salt solutions}, series = {Journal of biomaterials science : Polymer edition}, volume = {25}, journal = {Journal of biomaterials science : Polymer edition}, number = {14-15}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {0920-5063}, doi = {10.1080/09205063.2014.939918}, pages = {1602 -- 1618}, year = {2014}, language = {en} } @article{WessigGerngrossPapeetal.2014, author = {Wessig, Pablo and Gerngross, Maik and Pape, Simon and Bruhns, Philipp and Weber, Jens}, title = {Novel porous materials based on oligospiroketals (OSK)}, series = {RSC Advances}, volume = {4}, journal = {RSC Advances}, number = {59}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c4ra04437a}, pages = {31123 -- 31129}, year = {2014}, abstract = {New porous materials based on covalently connected monomers are presented. The key step of the synthesis is an acetalisation reaction. In previous years we used acetalisation reactions extensively to build up various molecular rods. Based on this approach, investigations towards porous polymeric materials were conducted by us. Here we wish to present the results of these studies in the synthesis of 1D polyacetals and porous 3D polyacetals. By scrambling experiments with 1D acetals we could prove that exchange reactions occur between different building blocks (evidenced by MALDI-TOF mass spectrometry). Based on these results we synthesized porous 3D polyacetals under the same mild conditions.}, language = {en} } @article{GrunzelPilarekSteinbruecketal.2014, author = {Grunzel, Petra and Pilarek, Maciej and Steinbrueck, Doerte and Neubauer, Antje and Brand, Eva and Kumke, Michael Uwe and Neubauer, Peter and Krause, Mirja}, title = {Mini-scale cultivation method enables expeditious plasmid production in Escherichia coli}, series = {Biotechnology journal : systems \& synthetic biology, nanobiotech, medicine}, volume = {9}, journal = {Biotechnology journal : systems \& synthetic biology, nanobiotech, medicine}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1860-6768}, doi = {10.1002/biot.201300177}, pages = {128 -- 136}, year = {2014}, abstract = {The standard procedure in the lab for plasmid isolation usually involves a 2-mL, 16 h over-night cultivation in 15-mL bioreaction tubes in LB medium. This is time consuming, and not suitable for high-throughput applications. This study shows that it is possible to produce plasmid DNA (pDNA) in a 1.5-mL microcentrifuge tube with only 100 L cultivation volume in less than 7 h with a simple protocol. Compared with the standard LB cultivation for pDNA production reaching a final pDNA concentration range of 1.5-4 mu g mL(-1), a 6- to 10-fold increase in plasmid concentration (from 10 up to 25 mu g mL(-1) cultivation volume) is achieved using an optimized medium with an internal substrate delivery system (EnBase (R)). Different strains, plasmids, and the applicability of different inoculation tools (i.e. different starting ODs) were compared, demonstrating the robustness of the system. Additionally, dissolved oxygen was monitored in real time online, indicating that under optimized conditions oxygen limitation can be avoided. We developed a simple protocol with a significantly decreased procedure time, enabling simultaneous handling of more samples, while a consistent quality and a higher final pDNA concentration are ensured.}, language = {en} } @article{VaskovaKitanovskiJaglicicetal.2014, author = {Vaskova, Zuzana and Kitanovski, Nives and Jaglicic, Zvonko and Strauch, Peter and Ruzickova, Zdenka and Valigura, Dusan and Koman, Marian and Kozlevcar, Bojan and Moncol, Jan}, title = {Synthesis and magneto-structural characterization of copper(II) nitrobenzoate complexes containing nicotinamide or methylnicotinamide ligands}, series = {Polyhedron : the international journal of inorganic and organometallic chemistry}, volume = {81}, journal = {Polyhedron : the international journal of inorganic and organometallic chemistry}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-5387}, doi = {10.1016/j.poly.2014.07.017}, pages = {555 -- 563}, year = {2014}, abstract = {Three new copper(II) 4-nitrobenzoato coordination compounds (4-NO(2)bz(-) = 4-nitrobenzoate anions) with N-methylnicotinamide (mna) [Cu(4-NO(2)bz)(2)(mna)(2)(H2O)] (1), [Cu(4-NO(2)bz)(2)(mu-mna)(H2O)](2) (2) and [Cu(mu-4-NO(2)bz)(2)(mna)](2) (3) were synthesized and characterized. Due to a comparison, additional two related compounds [Cu(3,5-(NO2)(2)bz)(2)(mna)(2)(H2O)] (4) (nia = nicotinamide, 3,5-(NO2)(2)bz(-) = 3,5-dinitrobenzoate anions) and [Cu(mu-2-NO(2)bz)(2)(mna)](2) (5) (2-NO(2)bz(-) = 2-nitrobenzoate anions) were isolated. The mononuclear compounds with mna 1 and nia 4 show CuO2N2O chromophores with the water molecule placed at the apex of the square pyramid. The square-pyramidal coordination sphere CuO3NO in 2 differs to CuO2N2O in 1 and 4. Differently, the water molecule is in 2 at the basal-plane, while two mna molecules serve also as bridges via N-py and 0-amido enabling a dinuclear molecular structure 1, 2 and 4 are paramagnetic though a dinuclear structure is seen in 2, while a clear-cut strong antiferromagnetic (AFM) coupling (2J -300 cm(-1)) is found for the compounds 3 and 5. (C) 2014 Elsevier Ltd. All rights reserved.}, language = {en} } @article{PereiraNascimentoMagalhaesetal.2014, author = {Pereira, Fernanda S. and Nascimento, Heliara D. L. and Magalhaes, Alvicler and Peter, Martin G. and Bataglion, Giovana Anceski and Eberlin, Marcos N. and Gonzalez, Eduardo R. P.}, title = {ESI(+)-MS and GC-MS study of the hydrolysis of N-azobenzyl derivatives of chitosan}, series = {Molecules}, volume = {19}, journal = {Molecules}, number = {11}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules191117604}, pages = {17604 -- 17618}, year = {2014}, abstract = {New N-p-chloro-, N-p-bromo-, and N-p-nitrophenylazobenzylchitosan derivatives, as well as the corresponding azophenyl and azophenyl-p-sulfonic acids, were synthesized by coupling N-benzylvchitosan with aryl diazonium salts. The synthesized molecules were analyzed by UV-Vis, FT-IR, H-1-NMR and N-15-NMR spectroscopy. The capacity of copper chelation by these materials was studied by AAS. Chitosan and the derivatives were subjected to hydrolysis and the products were analyzed by ESI(+)-MS and GC-MS, confirming the formation of N-benzyl chitosan. Furthermore, the MS results indicate that a nucleophilic aromatic substitution (SnAr) reaction occurs under hydrolysis conditions, yielding chloroaniline from N-p-bromo-, and N-p-nitrophenylazo-benzylchitosan as well as bromoaniline from N-p-chloro-, and N-p-nitrophenylazobenzyl-chitosan.}, language = {en} } @article{CywinskiHammannHuehnetal.2014, author = {Cywinski, Piotr J. and Hammann, Tommy and Huehn, Dominik and Parak, Wolfgang J. and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Europium-quantum dot nanobioconjugates as luminescent probes for time-gated biosensing}, series = {Journal of biomedical optics}, volume = {19}, journal = {Journal of biomedical optics}, number = {10}, publisher = {SPIE}, address = {Bellingham}, issn = {1083-3668}, doi = {10.1117/1.JBO.19.10.101506}, pages = {8}, year = {2014}, abstract = {Nanobioconjugates have been synthesized using cadmium selenide quantum dots (QDs), europium complexes (EuCs), and biotin. In those conjugates, long-lived photoluminescence (PL) is provided by the europium complexes, which efficiently transfer energy via Forster resonance energy transfer (FRET) to the QDs in close spatial proximity. As a result, the conjugates have a PL emission spectrum characteristic for QDs combined with the long PL decay time characteristic for EuCs. The nanobioconjugates synthesis strategy and photo-physical properties are described as well as their performance in a time-resolved streptavidin-biotin PL assay. In order to prepare the QD-EuC-biotin conjugates, first an amphiphilic polymer has been functionalized with the EuC and biotin. Then, the polymer has been brought onto the surface of the QDs (either QD655 or QD705) to provide functionality and to make the QDs water dispersible. Due to a short distance between EuC and QD, an efficient FRET can be observed. Additionally, the QD-EuC-biotin conjugates' functionality has been demonstrated in a PL assay yielding good signal discrimination, both from autofluorescence and directly excited QDs. These newly designed QD-EuC-biotin conjugates expand the class of highly sensitive tools for bioanalytical optical detection methods for diagnostic and imaging applications. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)}, language = {en} } @article{SarauliPetersXuetal.2014, author = {Sarauli, David and Peters, Kristina and Xu, Chenggang and Schulz, Burkhard and Fattakhova-Rohlfing, Dina and Lisdat, Fred}, title = {3D-Electrode architectures for enhanced direct bioelectrocatalysis of pyrroloquinoline quinone-dependent glucose dehydrogenase}, series = {ACS applied materials \& interfaces}, volume = {6}, journal = {ACS applied materials \& interfaces}, number = {20}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/am5046026}, pages = {17887 -- 17893}, year = {2014}, abstract = {We report on the fabrication of a complex electrode architecture for efficient direct bioelectrocatalysis. In the developed procedure, the redox enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase entrapped in a sulfonated polyaniline [poly(2-methoxyaniline-5-sulfonic acid)-co-aniline] was immobilized on macroporous indium tin oxide (macroITO) electrodes. The use of the 3D-conducting scaffold with a large surface area in combination with the conductive polymer enables immobilization of large amounts of enzyme and its efficient communication with the electrode, leading to enhanced direct bioelectrocatalysis. In the presence of glucose, the fabricated bioelectrodes show an exceptionally high direct bioelectrocatalytical response without any additional mediator. The catalytic current is increased more than 200-fold compared to planar ITO electrodes. Together with a high long-term stability (the current response is maintained for >90\% of the initial value even after 2 weeks of storage), the transparent 3D macroITO structure with a conductive polymer represents a valuable basis for the construction of highly efficient bioelectronic units, which are useful as indicators for processes liberating glucose and allowing optical and electrochemical transduction.}, language = {en} } @article{GoetzeKroenerBanerjeeetal.2014, author = {Goetze, Jan P. and Kr{\"o}ner, Dominik and Banerjee, Shiladitya and Karasulu, Bora and Thiel, Walter}, title = {Carotenoids as a shortcut for chlorophyll Soret-to-Q band energy flow}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {15}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {15}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201402233}, pages = {3391 -- 3400}, year = {2014}, abstract = {It is proposed that xanthophylls, and carotenoids in general, may assist in energy transfer from the chlorophyll Soret band to the Q band. Ground-state (1A(g)) and excited-state (1B(u)) optimizations of violaxanthin (Vx) and zeaxanthin (Zx) are performed in an environment mimicking the light-harvesting complex II (LHCII), including the closest chlorophyll b molecule (Chl). Time-dependent density functional theory (TD-DFT, CAM-B3LYP functional) is used in combination with a semi-empirical description to obtain the excited-state geometries, supported by additional DFT/multireference configuration interaction calculations, with and without point charges representing LHCII. In the ground state, Vx and Zx show similar properties. At the 1B(u) minimum, the energy of the Zx 1Bu state is below the Chl Q band, in contrast to Vx. Both Vx and Zx may act as acceptors of Soret-state energy; transfer to the Q band seems to be favored for Vx. These findings suggest that carotenoids may generally mediate Soret-to-Q energy flow in LHCII.}, language = {en} } @article{CommingesFrascaSuetterlinetal.2014, author = {Comminges, Clement and Frasca, Stefano and Suetterlin, Martin and Wischerhoff, Erik and Laschewsky, Andr{\´e} and Wollenberger, Ursula}, title = {Surface modification with thermoresponsive polymer brushes for a switchable electrochemical sensor}, series = {RSC Advances}, volume = {4}, journal = {RSC Advances}, number = {81}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c4ra07190e}, pages = {43092 -- 43097}, year = {2014}, abstract = {Elaboration of switchable surfaces represents an interesting way for the development of a new generation of electrochemical sensors. In this paper, a method for growing thermoresponsive polymer brushes from a gold surface pre-modified with polyethyleneimine (PEI), subsequent layer-by-layer polyelectrolyte assembly and adsorption of a charged macroinitiator is described. We propose an easy method for monitoring the coil-to-globule phase transition of the polymer brush using an electrochemical quartz crystal microbalance with dissipation (E-QCM-D). The surface of these polymer modified electrodes shows reversible switching from the swollen to the collapsed state with temperature. As demonstrated from E-QCM-D measurements using an original signal processing method, the switch is operating in three reversible steps related to different interfacial viscosities. Moreover, it is shown that the one electron oxidation of ferrocene carboxylic acid is dramatically affected by the change from the swollen to the collapsed state of the polymer brush, showing a spectacular 86\% decrease of the charge transfer resistance between the two states.}, language = {en} } @article{BrauneWalterSchulzeetal.2014, author = {Braune, Steffen and Walter, M. and Schulze, F. and Lendlein, Andreas and Jung, Friedrich}, title = {Changes in platelet morphology and function during 24 hours of storage}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {58}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {1}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-141876}, pages = {159 -- 170}, year = {2014}, abstract = {For in vitro studies assessing the interaction of platelets with implant materials, common and standardized protocols for the preparation of platelet rich plasma (PRP) are lacking, which may lead to non-matching results due to the diversity of applied protocols. Particularly, the aging of platelets during prolonged preparation and storage times is discussed to lead to an underestimation of the material thrombogenicity. Here, we study the influence of whole blood-and PRP-storage times on changes in platelet morphology and function. Whole blood PFA100 closure times increased after stimulation with collagen/ADP and collagen/epinephrine. Twenty four hours after blood collection, both parameters were prolonged pathologically above the upper limit of the reference range. Numbers of circulating platelets, measured in PRP, decreased after four hours, but no longer after twenty four hours. Mean platelet volumes (MPV) and platelet large cell ratios (P-LCR, 12 fL - 40 fL) decreased over time. Immediately after blood collection, no debris or platelet aggregates could be visualized microscopically. After four hours, first debris and very small aggregates occurred. After 24 hours, platelet aggregates and also debris progressively increased. In accordance to this, the CASY system revealed an increase of platelet aggregates (up to 90 mu m diameter)with increasing storage time. The percentage of CD62P positive platelets and PF4 increased significantly with storage time in resting PRP. When soluble ADP was added to stored PRP samples, the number of activatable platelets decreased significantly over storage time. The present study reveals the importance of a consequent standardization in the preparation of WB and PRP. Platelet morphology and function, particularly platelet reactivity to adherent or soluble agonists in their surrounding milieu, changed rapidly outside the vascular system. This knowledge is of crucial interest, particularly in the field of biomaterial development for cardiovascular applications, and may help to define common standards in the in vitro hemocompatibility testing of biomaterials.}, language = {en} } @article{KovachKoetzFriberg2014, author = {Kovach, Ildyko and Koetz, Joachim and Friberg, Stig E.}, title = {Janus emulsions stabilized by phospholipids}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {441}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2013.08.065}, pages = {66 -- 71}, year = {2014}, abstract = {Janus emulsions were formed by mixing three immiscible liquids; this implies two oil components (i.e. olive oil (00) and silicone oil (SiO)) with water in presence of interfacial active components. The morphology and size of Janus droplets formed strongly depended on the type of surfactant used. In presence of a non-ionic surfactant, i.e. Tween 80, large engulfed Janus droplets were formed. By adding phospholipids to the system the droplet size was decreased and more stable Janus droplets formed. Interfacial tension measurements carried out using a spinning drop apparatus and a ring tensiometer demonstrate that interfacial tension is the most important factor controlling the size, morphology and stability of Janus droplets. When the interfacial tension between oil and water becomes <= 1 mN/m, smaller Janus droplets are formed. Such conditions are fulfilled when phospholipids are used in combination with non-ionic surfactant Tween 80. The morphology of the double droplets is predominantly controlled by the viscosity and interfacial tension between the two oil phases. By using different types of phospholipids, i.e. asolectin and lecithin instead of a more concentrated phosphatidylcholine (phospholipon), the interfacial tension is decreased and different morphologies of engulfing can be observed.}, language = {en} } @article{KroenerSchimkaKlamroth2014, author = {Kroener, Dominik and Schimka, Selina and Klamroth, Tillmann}, title = {Laser control for coupled torsions in chiroptical switches: a combined quantum and classical dynamics approach}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {118}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {2}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/jp410342a}, pages = {1322 -- 1331}, year = {2014}, abstract = {We present a novel laser pulse control for the chiroptical switch 1-(2-cis-fluoroethenyl)-2-fluoro-3,5-dibromobenzene mounted on adamantane, where the latter imitates a linker group or part of a solid surface. This molecular device offers three switching states: a true achiral "off"-state and two chiral "on"-states of opposite handedness. Due to the alignment of its chiral axis along the surface normal several defined orientations of the switch have to be considered for an efficient stereocontrol strategy. In addition to these different initial conditions, coupled torsional degrees of freedom around the chiral axis make the quest for highly stereoselective laser pulses a challenge. The necessary flexibility in pulse accomplished by employing the iterative stochastic pulse optimization method we presented recently. Still, the complexity of the system dictates a combined treatment by fast molecular dynamics and computationally intensive quantum dynamics. Although quantum effects are found to be of importance, the pulses optimized within the classical treatment allow us to turn on the chirality of the switch, achieving high enantioselectivity in the quantum treatment for all orientations at the same time.}, language = {en} }