TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Benzenium Ion BT - aromatic as the pi-complex or antiaromatic as the sigma-complex being somewhat similar to the cyclopentadienyl cation JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of the benzenium cation (C6H7+) 1 and of +/- I/M-substituted analogues C6H6X+ 3-8 [X = -Me, -CF3, -NH2, -NO2, -NO, -SiH3] have been calculated using the gauge-independent atomic orbital perturbation method employing the nucleus-independent chemical shift concept, and iso-chemical-shielding surfaces of various sizes and directions have been observed. The TSNMRS values were employed to compare the spatial magnetic properties (TSNMRS) of benzene and the benzenium ion 1 and then further compared with analogues 3-8, to answer the question whether the electronic structures of 1 and 3-8 are still similar to those of aromatic species or somewhat similar to the antiaromatic cyclopentadienyl cation 2, supported by structural data and delta(C-13)/ppm values. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpca.9b03121 SN - 1089-5639 VL - 123 IS - 20 SP - 4443 EP - 4451 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wolf, Thomas J. A. A1 - Sanchez, David M. A1 - Yang, J. A1 - Parrish, R. M. A1 - Nunes, J. P. F. A1 - Centurion, M. A1 - Coffee, R. A1 - Cryan, J. P. A1 - Gühr, Markus A1 - Hegazy, Kareem A1 - Kirrander, Adam A1 - Li, R. K. A1 - Ruddock, J. A1 - Shen, Xiaozhe A1 - Vecchione, T. A1 - Weathersby, S. P. A1 - Weber, Peter M. A1 - Wilkin, K. A1 - Yong, Haiwang A1 - Zheng, Q. A1 - Wang, X. J. A1 - Minitti, Michael P. A1 - Martinez, Todd J. T1 - The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction JF - Nature chemistry N2 - The ultrafast photoinduced ring-opening of 1,3-cyclohexadiene constitutes a textbook example of electrocyclic reactions in organic chemistry and a model for photobiological reactions in vitamin D synthesis. Although the relaxation from the photoexcited electronic state during the ring-opening has been investigated in numerous studies, the accompanying changes in atomic distance have not been resolved. Here we present a direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and subangstrom length scale using megaelectronvolt ultrafast electron diffraction. We followed the carbon-carbon bond dissociation and the structural opening of the 1,3-cyclohexadiene ring by the direct measurement of time-dependent changes in the distribution of interatomic distances. We observed a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to a steepening of the electronic potential gradient towards the product minima. The ring-opening motion transforms into rotation of the terminal ethylene groups in the photoproduct 1,3,5-hexatriene on the subpicosecond timescale. KW - Organic chemistry KW - Photochemistry KW - Physical chemistry KW - Theoretical chemistry Y1 - 2019 U6 - https://doi.org/10.1038/s41557-019-0252-7 SN - 1755-4330 SN - 1755-4349 VL - 11 IS - 6 SP - 504 EP - 509 PB - Nature Publ. Group CY - London ER - TY - GEN A1 - Kleinpeter, Erich A1 - Shainyan, Bagrat A. T1 - Very low-temperature dynamic Si-29 NMR study of the conformational equilibrium of (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane T2 - Magnetic resonance in chemistry Y1 - 2019 U6 - https://doi.org/10.1002/mrc.4870 SN - 0749-1581 SN - 1097-458X VL - 57 IS - 6 SP - 317 EP - 319 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Bald, Ilko A1 - Schürmann, Robin Mathis A1 - Ebel, Kenny A1 - Nicolas, Christophe A1 - Milosavljevic, Aleksandar R. T1 - Role of valence band states and plasmonic enhancement in electron-transfer-induced transformation of nitrothiophenol JF - The Journal of Physical Chemistry Letters N2 - Hot-electron-induced reactions are more and more recognized as a critical and ubiquitous reaction in heterogeneous catalysis. However, the kinetics of these reactions is still poorly understood, which is also due to the complexity of plasmonic nanostructures. We determined the reaction rates of the hot-electron-mediated reaction of 4-nitrothiophenol (NTP) on gold nanoparticles (AuNPs) using fractal kinetics as a function of the laser wavelength and compared them with the plasmonic enhancement of the system. The reaction rates can be only partially explained by the plasmonic response of the NPs. Hence, synchrotron X-ray photoelectron spectroscopy (XPS) measurements of isolated NTP-capped AuNP clusters have been performed for the first time. In this way, it was possible to determine the work function and the accessible valence band states of the NP systems. The results show that besides the plasmonic enhancement, the reaction rates are strongly influenced by the local density of the available electronic states of the system. Y1 - 2019 UR - https://pubs.acs.org/doi/10.1021/acs.jpclett.9b00848 U6 - https://doi.org/10.1021/acs.jpclett.9b00848 SN - 1948-7185 VL - 10 SP - 3153 EP - 3158 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Yan, Runyu A1 - Josef, Elinor A1 - Huang, Haijian A1 - Leus, Karen A1 - Niederberger, Markus A1 - Hofmann, Jan P. A1 - Walczak, Ralf A1 - Antonietti, Markus A1 - Oschatz, Martin T1 - Understanding the charge storage mechanism to achieve high capacity and fast ion storage in sodium-ion capacitor anodes by using electrospun nitrogen-doped carbon fibers JF - Advanced functional materials N2 - Microporous nitrogen-rich carbon fibers (HAT-CNFs) are produced by electrospinning a mixture of hexaazatriphenylene-hexacarbonitrile (HAT-CN) and polyvinylpyrrolidone and subsequent thermal condensation. Bonding motives, electronic structure, content of nitrogen heteroatoms, porosity, and degree of carbon stacking can be controlled by the condensation temperature due to the use of the HAT-CN with predefined nitrogen binding motives. The HAT-CNFs show remarkable reversible capacities (395 mAh g(-1) at 0.1 A g(-1)) and rate capabilities (106 mAh g(-1) at 10 A g(-1)) as an anode material for sodium storage, resulting from the abundant heteroatoms, enhanced electrical conductivity, and rapid charge carrier transport in the nanoporous structure of the 1D fibers. HAT-CNFs also serve as a series of model compounds for the investigation of the contribution of sodium storage by intercalation and reversible binding on nitrogen sites at different rates. There is an increasing contribution of intercalation to the charge storage with increasing condensation temperature which becomes less active at high rates. A hybrid sodium-ion capacitor full cell combining HAT-CNF as the anode and salt-templated porous carbon as the cathode provides remarkable performance in the voltage range of 0.5-4.0 V (95 Wh kg(-1) at 0.19 kW kg(-1) and 18 Wh kg(-1) at 13 kW kg(-1)). KW - carbon fibers KW - nitrogen-doped carbon KW - sodium-ion capacitors KW - sodium storage mechanism Y1 - 2019 U6 - https://doi.org/10.1002/adfm.201902858 SN - 1616-301X SN - 1616-3028 VL - 29 IS - 26 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wanjiku, Barbara A1 - Yamamoto, Kenji A1 - Klossek, Andre A1 - Schumacher, Fabian A1 - Pischon, Hannah A1 - Mundhenk, Lars A1 - Rancan, Fiorenza A1 - Judd, Martyna M. A1 - Ahmed, Muniruddin A1 - Zoschke, Christian A1 - Kleuser, Burkhard A1 - Rühl, Eckart A1 - Schäfer-Korting, Monika T1 - Qualifying X-ray and Stimulated Raman Spectromicroscopy for Mapping Cutaneous Drug Penetration JF - Analytical chemistry N2 - Research on topical drug delivery relies on reconstructed human skin (RHS) in addition to ex vivo human and animal skin, each with specific physiological features. Here, we compared the penetration of dexamethasone from an ethanolic hydroxyethyl cellulose gel into ex vivo human skin, murine skin, and RHS. For comprehensive insights into skin morphology and penetration enhancing mechanisms, scanning transmission X-ray microscopy (STXM), liquid chromatography tandem mass spectrometry (LC-MS/MS), and stimulated Raman spectromicroscopy (SRS) were combined. STXM offers high spatial resolution with label-free drug detection and is therefore sensitive to tissue damage. Despite differences in sample preparation and data analysis, the amounts of dexamethasone in RHS, detected and quantified by STXM and LC-MS/MS, were very similar and increased during the first 100 min of exposure. SRS revealed interactions between the gel and the stratum corneum or, more specifically, its protein and lipid structures. Similar to both types of ex vivo skin, higher protein-to-lipid ratios within the stratum corneum of RHS indicated reduced lipid amounts after 30 min of ethanol exposure. Extended ethanol exposure led to a continued reduction of lipids in the ex vivo matrixes, while protein integrity appeared to be compromised in RHS, which led to declining protein signals. In conclusion, LC-MS/MS proved the predictive capability of STXM for label-free drug detection. Combining STXM with SRS precisely dissected the penetration enhancing effects of ethanol. Further studies on topical drug delivery should consider the potential of these complementary techniques. Y1 - 2019 U6 - https://doi.org/10.1021/acs.analchem.9b00519 SN - 0003-2700 SN - 1520-6882 VL - 91 IS - 11 SP - 7208 EP - 7214 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kosmella, Sabine A1 - Klemke, Bastian A1 - Häusler, Ines A1 - Koetz, Joachim T1 - From gel-like Pickering emulsions to highly ordered superparamagnetic magnetite aggregates with embedded gold nanoparticles JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Pickering emulsions with two types of nanoparticles, i.e., superparamagnetic magnetite nanoparticles dispersed in n-hexane and gold nanoparticles dispersed in water, were formed by rigorous mixing in presence of surface active polymeric surfactants. Monodisperse magnetite nanoparticles with a mean particle size of 4 nm were obtained by a microwave-assisted synthesis in n-hexane in presence of oleic acid, and gold nanoparticles were produced in aqueous solution in presence of the hyperbranched poly(ethyleneimine) (PEI) or sodium citrate as reducing and stabilizing agent. After mixing the prepared nanoparticle dispersions in presence of the Pluronics an intermediate gel-like phase is formed. The Pickering emulsion droplets in the intermediate phase are stabilized by both types of nanoparticles, as to be seen by cryo-SEM micrographs. After separating, solvent evaporation and redispersion in water highly ordered Pluronic-stabilized superparamagnetic magnetite nanoparticle aggregates with embedded gold nanoparticles can be obtained. KW - Pickering emulsions KW - Pluronics KW - Magnetite and gold nanoparticles KW - Ring tensiometry KW - Cryo-SEM KW - HRTEM KW - Magnetization measurements Y1 - 2019 U6 - https://doi.org/10.1016/j.colsurfa.2019.03.017 SN - 0927-7757 SN - 1873-4359 VL - 570 SP - 331 EP - 338 PB - Elsevier Science CY - Amsterdam ER - TY - JOUR A1 - Haubitz, Toni A1 - John, Leonard A1 - Wessig, Pablo A1 - Kumke, Michael Uwe T1 - Photophysics of Acyl- and Ester-DBD Dyes BT - Quadrupole-Induced Solvent Relaxation Investigated by Transient Absorption Spectroscopy JF - the journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - A new generation of wavelength-tunable, fluorescent dyes, so-called DBD ([1,3]dioxolo[4,5-f][1,3]benzodioxole) dyes, were developed a few years ago, and they showed great potential as probes, for example, for fluorescence microscopy. However, their photophysics is not fully explored and leaves open questions regarding their large fluorescence Stokes shifts and sensitivity to solvent conditions of differently substituted DBD dyes. To improve the understanding of the influence of the substitution pattern of the DBD dyes on their respective photophysics, transient absorption spectroscopy (TAS) was used, that is, a pump-probe experiment on the femtosecond timescale. TAS allows measurements of excited states, ground state recovery, solvent relaxation, and fluorescence properties on time scales of up to several nanoseconds. Two different DBD dye samples were investigated: aryl- and ester-substituted DBD dyes. Experiments were carried out in solvents with different polarities using different excitation energies and at different viscosities. Based on the experimental data and theoretical calculations, we were able to determine the conformational changes of the molecule due to electronic excitation and were able to investigate solvent relaxation processes for both types of DBD dyes. By generalizing the theory for quadrupole-induced solvent relaxation developed by Togashi et al., we derived quadrupole moments of both molecules in the ground and excited state. Our data showed differences in the binding of polar solvent molecules to the dyes depending on the substituent on the DBD dye. In the case of water as the solvent, an additional efficient quenching process in the electronically excited state was revealed, which was indicated by the observation of solvated electrons in the TAS signals. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpca.9b02973 SN - 1089-5639 VL - 123 IS - 22 SP - 4717 EP - 4726 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hartlieb, Matthias A1 - Catrouillet, Sylvain A1 - Kuroki, Agnes A1 - Sanchez-Cano, Carlos A1 - Peltier, Raoul A1 - Perrier, Sebastien T1 - Stimuli-responsive membrane activity of cyclic-peptide-polymer conjugates JF - Chemical science N2 - Cyclic peptide nanotubes (CPNT) consisting of an even number of amino acids with an alternating chirality are highly interesting materials in a biomedical context due to their ability to insert themselves into cellular membranes. However, unwanted unspecific interactions between CPNT and non-targeted cell membranes are a major drawback. To solve this issue we have synthetized a series of CPNT-polymer conjugates with a cleavable covalent connection between macromolecule and peptide. As a result, the polymers form a stabilizing and shielding shell around the nanotube that can be cleaved on demand to generate membrane active CPNT from non-active conjugates. This approach enables us to control the stacking and lateral aggregation of these materials, thus leading to stimuli responsive membrane activity. Moreover, upon activation, the systems can be adjusted to form nanotubes with an increased length instead of aggregates. We were able to study the dynamics of these systems in detail and prove the concept of stimuli responsive membrane interaction using CPNT-polymer conjugates to permeabilize liposomes as well as mammalian cell membranes. Y1 - 2019 U6 - https://doi.org/10.1039/c9sc00756c SN - 2041-6520 SN - 2041-6539 VL - 10 IS - 21 SP - 5476 EP - 5483 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Machatschek, Rainhard Gabriel A1 - Schöne, Anne-Christin A1 - Raschdorf, Elisa A1 - Ihlenburg, Ramona A1 - Schulz, Burkhard A1 - Lendlein, Andreas T1 - Interfacial properties of morpholine-2,5-dione-based oligodepsipeptides and multiblock copolymers T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air-water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air-water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1106 KW - block-copolymer KW - enzymatic degradation KW - poly(ester amide)s KW - controlled-release KW - films KW - nanocarriers Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-469755 SN - 1866-8372 IS - 1106 SP - 170 EP - 180 ER - TY - JOUR A1 - Nieuwenhuis, Sophie A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Biessmann, Lorenz A1 - Philipp, Martine A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Wang, Jiping A1 - Müller-Buschbaum, Peter T1 - Hydration and Dehydration Kinetics: Comparison between Poly(N-isopropyl methacrylamide) and Poly(methoxy diethylene glycol acrylate) Films JF - Langmuir N2 - Thermoresponsive films of poly(N-isopropyl methacrylamide) (PNIPMAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA) are compared with respect to their hydration and dehydration kinetics using in situ neutron reflectivity. Both as-prepared films present a homogeneous single-layer structure and have similar transition temperatures of the lower critical solution temperature type (TT, PNIPMAM 38 degrees C and PMDEGA 41 degrees C). After hydration in unsaturated D2O vapor at 23 degrees C, a D2O enrichment layer is observed in PNIPMAM films adjacent to the Si substrate. In contrast, two enrichment layers are present in PMDEGA films (close to the vapor interface and the Si substrate). PNIPMAM films exhibit a higher hydration capability, ascribed to having both donor (N-H) and acceptor (C=O) units for hydrogen bonds. "While the swelling of the PMDEGA films is mainly caused by the increase of the enrichment layers, the thickness of the entire PNIPMAM films increases with time. The observed longer relaxation time for swelling of PNIPMAM films is attributed to the much higher glass transition temperature of PNIPMAM. When dehydrating both films by increasing the temperature above the TT, they react with a complex response consisting of three stages (shrinkage, rearrangement, and reswelling). PNIPMAM films respond faster than PMDEGA films. After dehydration, both films still contain a large amount of D2O, and no completely dry film state is reached for a temperature above their TTs. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.9b00535 SN - 0743-7463 VL - 35 IS - 24 SP - 7691 EP - 7702 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Bedurke, Florian A1 - Klamroth, Tillmann A1 - Krause, Pascal A1 - Saalfrank, Peter T1 - Discriminating organic isomers by high harmonic generation BT - A time-dependent configuration interaction singles study JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - High Harmonic Generation (HHG) is a nonlinear optical process that provides a tunable source for high-energy photons and ultrashort laser pulses. Recent experiments demonstrated that HHG spectroscopy may also be used as an analytical tool to discriminate between randomly oriented configurational isomers of polyatomic organic molecules, namely, between the cis- and trans-forms of 1,2-dichloroethene (DCE) [M. C. H. Wong et al., Phys. Rev. A 84, 051403 (2011)]. Here, we suggest as an economic and at the same time a reasonably accurate method to compute HHG spectra for polyatomic species, Time-Dependent Configuration Interaction Singles (TD-CIS) theory in combination with extended atomic orbital bases and different models to account for ionization losses. The HHG spectra are computed for aligned and unaligned cis- and trans-DCE. For the unaligned case, a coherent averaging over possible rotational orientations is introduced. Furthermore, using TD-CIS, possible differences between the HHG spectra of cis- and trans-DCE are studied. For aligned molecules, spectral differences between cis and trans emerge, which can be related to their different point group symmetries. For unaligned, randomly oriented molecules, we also find distinct HHG spectra in partial agreement with experiment. In addition to HHG response in the frequency space, we compute time-frequency HHG spectra to gain insight into which harmonics are emitted at which time. Further differences between the two isomers emerge, suggesting time-frequency HHG as another tool to discriminate configurational isomers. Y1 - 2019 U6 - https://doi.org/10.1063/1.5096473 SN - 0021-9606 SN - 1089-7690 VL - 150 IS - 23 PB - American Institute of Physics CY - Melville ER - TY - GEN A1 - Jiang, Yi A1 - Mansfeld, Ulrich A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memory technology T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 degrees C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 degrees C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads. optical storage, or cell instructive substrates. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1102 KW - shape KW - surfaces KW - modulus Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-469745 SN - 1866-8372 VL - 9 IS - 1 SP - 181 EP - 188 ER - TY - JOUR A1 - Melani, Giacomo A1 - Nagata, Yuki A1 - Campen, Richard Kramer A1 - Saalfrank, Peter T1 - Vibrational spectra of dissociatively adsorbed D2O on Al-terminated alpha-Al2O3(0001) surfaces from ab initio molecular dynamics JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Water can adsorb molecularly or dissociatively onto different sites of metal oxide surfaces. These adsorption sites can be disentangled using surface-sensitive vibrational spectroscopy. Here, we model Vibrational Sum Frequency (VSF) spectra for various forms of dissociated, deuterated water on a reconstructed, Al-terminated α-Al2O3(0001) surface at submonolayer coverages (the so-called 1-2, 1-4, and 1-4′ modes). Using an efficient scheme based on velocity-velocity autocorrelation functions, we go beyond previous normal mode analyses by including anharmonicity, mode coupling, and thermal surface motion in the framework of ab initio molecular dynamics. In this way, we calculate vibrational density of states curves, infrared, and VSF spectra. Comparing computed VSF spectra with measured ones, we find that relative frequencies of resonances are in quite good agreement and linewidths are reasonably well represented, while VSF intensities coincide not well. We argue that intensities are sensitively affected by local interactions and thermal fluctuations, even at such low coverage, while absolute peak positions strongly depend on the choice of the electronic structure method and on the appropriate inclusion of anharmonicity. Y1 - 2019 U6 - https://doi.org/10.1063/1.5099895 SN - 0021-9606 SN - 1089-7690 VL - 150 IS - 24 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Bouakline, Foudhil A1 - Fischer, E. W. A1 - Saalfrank, Peter T1 - A quantum-mechanical tier model for phonon-driven vibrational relaxation dynamics of adsorbates at surfaces JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - We present a quantum-mechanical tier model for vibrational relaxation of low-lying excited states of an adsorbate vibrational mode (system), coupled to surface phonons (bath), at zero temperature. The tier model, widely used in studies of intramolecular vibrational energy redistribution in polyatomics, is adapted here to adsorbate-surface systems with the help of an embedded cluster approach, using orthogonal coordinates for the system and bath modes, and a phononic expansion of their interaction. The key idea of the model is to organize the system-bath zeroth-order vibrational space into a hierarchical structure of vibrational tiers and keep therein only vibrational states that are sequentially generated from the system-bath initial vibrational state. Each tier is generated from the previous one by means of a successor operator, derived from the system-bath interaction Hamiltonian. This sequential procedure leads to a drastic reduction of the dimension of the system-bath vibrational space. We notably show that for harmonic vibrational motion of the system and linear system-bath couplings in the system coordinate, the dimension of the tier-model vibrational basis scales as similar to N-lxv. Here, N is the number of bath modes, l is the highest-order of the phononic expansion, and l is the size of the system vibrational basis. This polynomial scaling is computationally far superior to the exponential scaling of the original zeroth-order vibrational basis, similar to M-N, with M being the number of basis functions per bath mode. In addition, since each tier is coupled only to its adjacent neighbors, the matrix representation of the system-bath Hamiltonian in this new vibrational basis has a symmetric block-tridiagonal form, with each block being very sparse. This favors the combination of the tier-model with iterative Krylov techniques, such as the Lanczos algorithm, to solve the time-dependent Schrodinger equation for the full Hamiltonian. To illustrate the method, we study vibrational relaxation of a D-Si bending mode, coupled via two-and (mainly) one-phonon interactions to a fully D-covered Si(100)-(2 x 1) surface, using a recent first-principles system-bath Hamiltonian. The results of the tier model are compared with those obtained by the Lindblad formalism of the reduced density matrix. We find that the tier model provides much more information and insight into mechanisms of vibration-phonon couplings at surfaces, and gives more reliable estimates of the adsorbate vibrational lifetimes. Moreover, the tier model might also serve as a benchmark for other approximate quantum-dynamics methods, such as multiconfiguration wavefunction approaches. Published under license by AIP Publishing. Y1 - 2019 U6 - https://doi.org/10.1063/1.5099902 SN - 0021-9606 SN - 1089-7690 VL - 150 IS - 24 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Theoretical insights into the effect of solvents on the [4+2] cycloaddition of singlet oxygen to substituted anthracenes BT - A change from a stepwise process to a concerted process JF - Journal of physical organic chemistry N2 - The [4 + 2] cycloadditions of singlet oxygen to 9,10-diphenylanthracene (1) and the meta and para isomers of 9,10-dipyridylanthracene (2m/p) and 9,10-methoxyphenylanthracene (3m/p) have been studied by density functional calculations in the gas phase at the UB3LYP/6-31G* level and for the first time in solvents at the conductor-like polarizable continuum model (CPCM) UM062X/6-31G* level. The differences in calculated transition state (TS) energies derived from this method are in line with experimentally observed reactivity orders in solution. For the gas-phase reaction, the first TS of the stepwise pathway (TS1) has biradical character, and its energy lies below the energy of the TS of the concerted path (TSconc). In contrast, in the solvent acetonitrile, TS1 resembles a zwitterion and lies significantly higher than the TSconc. Thus, a concerted mechanism applies in solvents, and the energy gap between the TS of the two processes decreases with decreasing polarity. A change from a pyridyl against a methoxyphenyl substituent in the para position causes a maximal reduction of the activation barrier by approximately 1.7 kcal/mol, resulting in a fivefold increased reactivity. KW - anthracenes KW - DFT calculations KW - endoperoxides KW - photooxygenation KW - singlet oxygen KW - solvent effect Y1 - 2019 U6 - https://doi.org/10.1002/poc.3951 SN - 0894-3230 SN - 1099-1395 VL - 32 IS - 7 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Zude, Manuela A1 - Hashim, Norhashila A1 - Hass, Roland A1 - Polley, Nabarun A1 - Regen, Christian T1 - Validation study for measuring absorption and reduced scattering coefficients by means of laser-induced backscattering imaging JF - Postharvest Biology and Technology N2 - Decoupling of optical properties appears challenging, but vital to get better insight of the relationship between light and fruit attributes. In this study, nine solid phantoms capturing the ranges of absorption (μa) and reduced scattering (μs’) coefficients in fruit were analysed non-destructively using laser-induced backscattering imaging (LLBI) at 1060 nm. Data analysis of LLBI was carried out on the diffuse reflectance, attenuation profile obtained by means of Farrell’s diffusion theory either calculating μa [cm−1] and μs’ [cm−1] in one fitting step or fitting only one optical variable and providing the other one from a destructive analysis. The nondestructive approach was approved when calculating one unknown coefficient non-destructively, while no ability of the method was found to analysis both, μa and μs’, non-destructively. Setting μs’ according to destructive photon density wave (PDW) spectroscopy and fitting μa resulted in root mean square error (rmse) of 18.7% in comparison to fitting μs’ resulting in rmse of 2.6%, pointing to decreased measuring uncertainty, when the highly variable μa was known. The approach was tested on European pear, utilizing destructive PDW spectroscopy for setting one variable, while LLBI was applied for calculating the remaining coefficient. Results indicated that the optical properties of pear obtained from PDW spectroscopy as well as LLBI changed concurrently in correspondence to water content mainly. A destructive batch-wise analysis of μs’ and online analysis of μa may be considered in future developments for improved fruit sorting results, when considering fruit with high variability of μs’. KW - Absorption KW - European pear KW - Fruit quality KW - Phantoms KW - Reduced scattering coefficient KW - Scattering KW - Spatially resolved spectroscopy Y1 - 2019 U6 - https://doi.org/10.1016/j.postharvbio.2019.04.002 SN - 0925-5214 SN - 1873-2356 VL - 153 SP - 161 EP - 168 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Lai, Feili A1 - Feng, Jianrui A1 - Hei, Tobias A1 - Wang, Gui-Chang A1 - Adler, Peter A1 - Antonietti, Markus A1 - Oschatz, Martin T1 - Strong metal oxide-support interactions in carbon/hematite nanohybrids activate novel energy storage modes for ionic liquid-based supercapacitors JF - Energy Storage Materials N2 - Strong metal oxide-support interaction is crucial to activate high energy storage modes of carbon-supported hybrid electrodes in ionic liquid-based supercapacitors. Although it is known that conductive supports can influence the electrochemical properties of metal oxides, insights into how metal oxide-support interactions can be exploited to optimize joint energy storage properties are lacking. We report the junction between alpha-Fe2O3 nanosplotches and phosphorus-doped ordered mesoporous carbon (CMK-3-P) with strong covalent anchoring of the metal oxide. The oxide-carbon interaction in CMK-3-P-Fe2O3 is strengthening the junction and charge transfer between Fe2O3 and CMK-3-P. It enhances energy storage by intensifying the interaction between ionic liquid ions and the surface of the electrode. Density functional theory simulations reveal that the strong metal oxide-support interaction increases the adsorption energy of ionic liquid to -4.77 eV as compared to -3.85 eV for a CMK-3Fe(2)O(3) hybrid with weaker binding. In spite of the lower specific surface area and apparently similar energy storage mode, the CMK-3-P-Fe2O3 exhibits superior electrical double-layer capacitor performance with a specific capacitance of 179 F g(-1) at 2 mV s(-1) (0-3.5 V) in comparison to Fe2O3-free CMK-3 and CMK-3-P reference materials. This principle for design of hybrid electrodes can be applicable for future rational design of stable metal oxide-support electrodes for advanced energy storage. KW - Supercapacitor KW - Nanohybrid KW - Iron oxide KW - Ionic liquid KW - Ordering transitions KW - Main text Y1 - 2019 U6 - https://doi.org/10.1016/j.ensm.2019.04.035 SN - 2405-8297 VL - 20 SP - 188 EP - 195 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Szatmari, Istvan A1 - Belasri, Khadija A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Fulop, Ferenc T1 - Ortho-Quinone methide driven synthesis of new O,N- or N,N-Heterocycles JF - ChemistryOpen : including thesis treasury N2 - To synthesize functionalized Mannich bases that can serve two different types of ortho-quinone methide (o-QM) intermediates, 2-naphthol and 6-hydroxyquinoline were reacted with salicylic aldehyde in the presence of morpholine. The Mannich bases that can form o-QM and aza-o-QM were also synthesized by mixing 2-naphthol, 2-nitrobenzaldehyde, and morpholine followed by reduction of the nitro group. The highly functionalized aminonaphthol derivatives were then tested in [4+2] cycloaddition with different cyclic imines. The reaction proved to be both regio- and diastereoselective. In all cases, only one reaction product was obtained. Detailed structural analyses of the new polyheterocycles as well as conformational studies including DFT modelling were performed. The relative stability of o-QMs/aza-o-QM were also calculated, and the regioselectivity of the reactions could be explained only when the cycloaddition started from aminodiol 4. It was summarized that starting from diaminonaphthol 25, the regioselectivity of the reaction is driven by the higher nucleophilicity of the amino group compared with the hydroxy group. 12H-benzo[a]xanthen-12-one (11), formed via o-QM formation, was isolated as a side product. The proton NMR spectrum of 11 proved to be very unique from NMR point of view. The reason for the extreme low-field position of proton H-1 could be accounted for by theoretical calculation of structure and spatial magnetic properties of the compound in combination of ring current effects of the aromatic moieties and steric compression within the heavily hindered H(1)-C(1)-C(12b)-C(12a)-C(12)=O structural fragment. KW - ortho-quinone methide (o-QMs) KW - modified Mannich reaction KW - cycloaddition KW - NMR spectroscopy KW - conformational analysis KW - DFT calculations Y1 - 2019 U6 - https://doi.org/10.1002/open.201900150 SN - 2191-1363 VL - 8 IS - 7 SP - 961 EP - 971 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Hwang, Jongkook A1 - Walczak, Ralf A1 - Oschatz, Martin A1 - Tarakina, Nadezda A1 - Schmidt, Bernhard V. K. J. T1 - Micro-Blooming: Hierarchically Porous Nitrogen-Doped Carbon Flowers Derived from Metal-Organic Mesocrystals JF - Small N2 - Synthesis of 3D flower-like zinc-nitrilotriacetic acid (ZnNTA) mesocrystals and their conformal transformation to hierarchically porous N-doped carbon superstructures is reported. During the solvothermal reaction, 2D nanosheet primary building blocks undergo oriented attachment and mesoscale assembly forming stacked layers. The secondary nucleation and growth preferentially occurs at the edges and defects of the layers, leading to formation of 3D flower-like mesocrystals comprised of interconnected 2D micropetals. By simply varying the pyrolysis temperature (550-1000 degrees C) and the removal method of in the situ-generated Zn species, nonporous parent mesocrystals are transformed to hierarchically porous carbon flowers with controllable surface area (970-1605 m(2) g(-1)), nitrogen content (3.4-14.1 at%), pore volume (0.95-2.19 cm(3) g(-1)), as well as pore diameter and structures. The carbon flowers prepared at 550 degrees C show high CO2/N-2 selectivity due to the high nitrogen content and the large fraction of (ultra)micropores, which can greatly increase the CO2 affinity. The results show that the physicochemical properties of carbons are highly dependent on the thermal transformation and associated pore formation process, rather than directly inherited from parent precursors. The present strategy demonstrates metal-organic mesocrystals as a facile and versatile means toward 3D hierarchical carbon superstructures that are attractive for a number of potential applications. KW - 3D flower superstructures KW - hierarchically porous carbon KW - metal-organic mesocrystals KW - thermal transformation mechanism Y1 - 2019 U6 - https://doi.org/10.1002/smll.201901986 SN - 1613-6810 SN - 1613-6829 VL - 15 IS - 37 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yuan, Jinkai A1 - Neri, Wilfrid A1 - Zakri, Cecile A1 - Merzeau, Pascal A1 - Kratz, Karl A1 - Lendlein, Andreas A1 - Poulin, Philippe T1 - Shape memory nanocomposite fibers for untethered high-energy microengines JF - Science N2 - Classic rotating engines are powerful and broadly used but are of complex design and difficult to miniaturize. It has long remained challenging to make large-stroke, high-speed, high-energy microengines that are simple and robust. We show that torsionally stiffened shape memory nanocomposite fibers can be transformed upon insertion of twist to store and provide fast and high-energy rotations. The twisted shape memory nanocomposite fibers combine high torque with large angles of rotation, delivering a gravimetric work capacity that is 60 times higher than that of natural skeletal muscles. The temperature that triggers fiber rotation can be tuned. This temperature memory effect provides an additional advantage over conventional engines by allowing for the tunability of the operation temperature and a stepwise release of stored energy. Y1 - 2019 U6 - https://doi.org/10.1126/science.aaw3722 SN - 0036-8075 SN - 1095-9203 VL - 365 IS - 6449 SP - 155 EP - 158 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Ugwuja, Chidinma G. A1 - Adelowo, Olawale O. A1 - Ogunlaja, Aemere A1 - Omorogie, Martins O. A1 - Olukanni, Olumide D. A1 - Ikhimiukor, Odion O. A1 - Iermak, Ievgeniia A1 - Kolawole, Gabriel A. A1 - Günter, Christina A1 - Taubert, Andreas A1 - Bodede, Olusola A1 - Moodley, Roshila A1 - Inada, Natalia M. A1 - Camargo, Andrea S.S. de A1 - Unuabonah, Emmanuel Iyayi T1 - Visible-Light-Mediated Photodynamic Water Disinfection @ Bimetallic-Doped Hybrid Clay Nanocomposites JF - ACS applied materials & interfaces N2 - This study reports a new class of photocatalytic hybrid clay nanocomposites prepared from low-cost sources (kaolinite clay and Carica papaya seeds) doped with Zn and Cu salts via a solvothermal process. X-ray diffraction analysis suggests that Cu-doping and Cu/Zn-doping introduce new phases into the crystalline structure of Kaolinite clay, which is linked to the reduced band gap of kaolinite from typically between 4.9 and 8.2 eV to 2.69 eV for Cu-doped and 1.5 eV for Cu/Zn hybrid clay nanocomposites (Nisar, J.; Arhammar, C.; Jamstorp, E.; Ahuja, R. Phys. Rev. B 2011, 84, 075120). In the presence of solar light irradiation, Cu- and Cu/Zn-doped nanocomposites facilitate the electron hole pair separation. This promotes the generation of singlet oxygen which in turn improves the water disinfection efficiencies of these novel nanocomposite materials. The nanocomposite materials were further characterized using high-resolution scanning electron microscopy, fluorimetry, therrnogravimetric analysis, and Raman spectroscopy. The breakthrough times of the nanocomposites for a fixed bed mode of disinfection of water contaminated with 2.32 x 10(7) cfu/mL E. coli ATCC 25922 under solar light irradiation are 25 h for Zn-doped, 30 h for Cu-doped, and 35 h for Cu/Zn-doped nanocomposites. In the presence of multidrug and multimetal resistant strains of E. coli, the breakthrough time decreases significantly. Zn-only doped nanocomposites are not photocatalytically active. In the absence of light, the nanocomposites are still effective in decontaminating water, although less efficient than under solar light irradiation. Electrostatic interaction, metal toxicity, and release of singlet oxygen (only in the Cu-doped and Cu/Zn-doped nanocomposites) are the three disinfection mechanisms by which these nanocomposites disinfect water. A regrowth study indicates the absence of any living E. coli cells in treated water even after 4 days. These data and the long hydraulic times (under gravity) exhibited by these nanocomposites during photodisinfection of water indicate an unusually high potential of these nanocomposites as efficient, affordable, and sustainable point-of-use systems for the disinfection of water in developing countries. KW - disinfection KW - nanocomposite material KW - multidrug-resistant Escherichia coli KW - water KW - reactive oxygen species Y1 - 2019 U6 - https://doi.org/10.1021/acsami.9b01212 SN - 1944-8244 SN - 1944-8252 VL - 11 IS - 28 SP - 25483 EP - 25494 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Bruun, Kristina A1 - Hille, Carsten T1 - Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy JF - Scientific reports N2 - Quantum dots increasingly gain popularity for in vivo applications. However, their delivery and accumulation into cells can be challenging and there is still lack of detailed information. Thereby, the application of advanced fluorescence techniques can expand the portfolio of useful parameters for a more comprehensive evaluation. Here, we encapsulated hydrophilic quantum dots into liposomes for studying cellular uptake of these so-called lipodots into living cells. First, we investigated photophysical properties of free quantum dots and lipodots observing changes in the fluorescence decay time and translational diffusion behaviour. In comparison to empty liposomes, lipodots exhibited an altered zeta potential, whereas their hydrodynamic size did not change. Fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS), both combined with two-photon excitation (2P), were used to investigate the interaction behaviour of lipodots with an insect epithelial tissue. In contrast to the application of free quantum dots, their successful delivery into the cytosol of salivary gland duct cells could be observed when applying lipodots. Lipodots with different lipid compositions and surface charges did not result in considerable differences in the intracellular labelling pattern, luminescence decay time and diffusion behaviour. However, quantum dot degradation after intracellular accumulation could be assumed from reduced luminescence decay times and blue-shifted luminescence signals. In addition to single diffusing quantum dots, possible intracellular clustering of quantum dots could be assumed from increased diffusion times. Thus, by using a simple and manageable liposome carrier system, 2P-FLIM and 2P-FCS recording protocols could be tested, which are promising for investigating the fate of quantum dots during cellular interaction. Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-46732-5 SN - 2045-2322 VL - 9 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Weis, Philipp A1 - Hess, Andreas A1 - Kircher, Gunnar A1 - Huang, Shilin A1 - Auernhammer, Günter K. A1 - Koynov, Kaloian A1 - Butt, Hans-Jürgen A1 - Wu, Si T1 - Effects of Spacers on Photoinduced Reversible Solid-to-Liquid Transitions of Azobenzene-Containing Polymers JF - Chemistry - a European journal N2 - Photoisomerization in some azobenzene-containing polymers (azopolymers) results in reversible solid-to-liquid transitions because trans- and cis-azopolymers have different glass transition temperatures. This property enables photoinduced healing and processing of azopolymers with high spatiotemporal resolution. However, a general lack of knowledge about the influence of the polymer structure on photoinduced reversible solid-to-liquid transitions hinders the design of such novel polymers. Herein, the synthesis and photoresponsive behavior of new azopolymers with different lengths of spacers between the polymer backbone and the azobenzene group on the side chain are reported. Azopolymers with no and 20 methylene spacers did not show photoinduced solid-to-liquid transitions. Azopolymers with 6 or 12 methylene spacers showed photoinduced solid-to-liquid transitions. This study demonstrates that spacers are essential for azopolymers with photoinduced reversible solid-to-liquid transitions, and thus, gives an insight into how to design azopolymers for photoinduced healing and processing. KW - azobenzenes KW - isomerization KW - photochemistry KW - polymers KW - self-healing Y1 - 2019 U6 - https://doi.org/10.1002/chem.201902273 SN - 0947-6539 SN - 1521-3765 VL - 25 IS - 46 SP - 10946 EP - 10953 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Qin, Qing A1 - Zhao, Yun A1 - Schmallegger, Max A1 - Heil, Tobias A1 - Schmidt, Johannes A1 - Walczak, Ralf A1 - Gescheidt-Demner, Georg A1 - Jiao, Haijun A1 - Oschatz, Martin T1 - Enhanced Electrocatalytic N-2 Reduction via Partial Anion Substitution in Titanium Oxide-Carbon Composites JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - The electrochemical conversion of N-2 at ambient conditions using renewably generated electricity is an attractive approach for sustainable ammonia (NH3) production. Considering the chemical inertness of N-2, rational design of efficient and stable catalysts is required. Therefore, in this work, it is demonstrated that a C-doped TiO2/C (C-TixOy/C) material derived from the metal-organic framework (MOF) MIL-125(Ti) can achieve a high Faradaic efficiency (FE) of 17.8 %, which even surpasses most of the established noble metal-based catalysts. On the basis of the experimental results and theoretical calculations, the remarkable properties of the catalysts can be attributed to the doping of carbon atoms into oxygen vacancies (OVs) and the formation of Ti-C bonds in C-TixOy. This binding motive is found to be energetically more favorable for N-2 activation compared to the non-substituted OVs in TiO2. This work elucidates that electrochemical N-2 reduction reaction (NRR) performance can be largely improved by creating catalytically active centers through rational substitution of anions into metal oxides. KW - ammonia synthesis KW - anion substitution KW - MOF-derived catalysts KW - N-2 fixation KW - non-noble metal catalysts Y1 - 2019 U6 - https://doi.org/10.1002/anie.201906056 SN - 1433-7851 SN - 1521-3773 VL - 58 IS - 37 SP - 13101 EP - 13106 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Keller, Sebastian A1 - Wetterhorn, Karl M. A1 - Vecellio, Alison A1 - Seeger, Mark A1 - Rayment, Ivan A1 - Schubert, Torsten T1 - Structural and functional analysis of an l-serine O-phosphate decarboxylase involved in norcobamide biosynthesis JF - FEBS letters : the journal for rapid publication of short reports in molecular biosciences N2 - Structural diversity of natural cobamides (Cbas, B12 vitamers) is limited to the nucleotide loop. The loop is connected to the cobalt‐containing corrin ring via an (R)‐1‐aminopropan‐2‐ol O‐2‐phosphate (AP‐P) linker moiety. AP‐P is produced by the l‐threonine O‐3‐phosphate (l‐Thr‐P) decarboxylase CobD. Here, the CobD homolog SMUL_1544 of the organohalide‐respiring epsilonproteobacterium Sulfurospirillum multivorans was characterized as a decarboxylase that produces ethanolamine O‐phosphate (EA‐P) from l‐serine O‐phosphate (l‐Ser‐P). EA‐P is assumed to serve as precursor of the linker moiety of norcobamides that function as cofactors in the respiratory reductive dehalogenase. SMUL_1544 (SmCobD) is a pyridoxal‐5′‐phosphate (PLP)‐containing enzyme. The structural analysis of the SmCobD apoprotein combined with the characterization of truncated mutant proteins uncovered a role of the SmCobD N‐terminus in efficient l‐Ser‐P conversion. KW - cobamides KW - ethanolamine phosphate KW - norcobamide biosynthesis KW - serine phosphate decarboxylase Y1 - 2019 U6 - https://doi.org/10.1002/1873-3468.13543 SN - 0014-5793 SN - 1873-3468 VL - 593 IS - 21 SP - 3040 EP - 3053 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Alrefai, Anas A1 - Mondal, Suvendu Sekhar A1 - Wruck, Alexander A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Brandt, Philipp A1 - Janiak, Christoph A1 - Schoenfeld, Sophie A1 - Weber, Birgit A1 - Rybakowski, Lawrence A1 - Herrman, Carmen A1 - Brennenstuhl, Katlen A1 - Eidner, Sascha A1 - Kumke, Michael Uwe A1 - Behrens, Karsten A1 - Günter, Christina A1 - Müller, Holger A1 - Holdt, Hans-Jürgen T1 - Hydrogen-bonded supramolecular metal-imidazolate frameworks: gas sorption, magnetic and UV/Vis spectroscopic properties JF - Journal of Inclusion Phenomena and Macrocyclic Chemistry N2 - By varying reaction parameters for the syntheses of the hydrogen-bonded metal-imidazolate frameworks (HIF) HIF-1 and HIF-2 (featuring 14 Zn and 14 Co atoms, respectively) to increase their yields and crystallinity, we found that HIF-1 is generated in two different frameworks, named as HIF-1a and HIF-1b. HIF-1b is isostructural to HIF-2. We determined the gas sorption and magnetic properties of HIF-2. In comparison to HIF-1a (Brunauer-Emmett-Teller (BET) surface area of 471m(2) g(-1)), HIF-2 possesses overall very low gas sorption uptake capacities [BET(CO2) surface area=85m(2) g(-1)]. Variable temperature magnetic susceptibility measurement of HIF-2 showed antiferromagnetic exchange interactions between the cobalt(II) high-spin centres at lower temperature. Theoretical analysis by density functional theory confirmed this finding. The UV/Vis-reflection spectra of HIF-1 (mixture of HIF-1a and b), HIF-2 and HIF-3 (with 14 Cd atoms) were measured and showed a characteristic absorption band centered at 340nm, which was indicative for differences in the imidazolate framework. KW - Gas-sorption KW - Ligand design KW - Magnetic properties KW - Supramolecular chemistry KW - Solvothermal synthesis Y1 - 2019 U6 - https://doi.org/10.1007/s10847-019-00926-6 SN - 1388-3127 SN - 1573-1111 VL - 94 IS - 3-4 SP - 155 EP - 165 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Zhang, Pengfei A1 - Behl, Marc A1 - Peng, Xingzhou A1 - Balk, Maria A1 - Lendlein, Andreas T1 - Chemoresponsive Shape-Memory Effect of Rhodium-Phosphine Coordination Polymer Networks JF - Chemistry of materials : a publication of the American Chemical Society N2 - Chemoresponsive polymers are of technological significance for smart sensors or systems capable of molecular recognition. An important key requirement for these applications is the material’s structural integrity after stimulation. We explored whether covalently cross-linked metal ion–phosphine coordination polymers (MPN) can be shaped into any temporary shape and are capable of recovering from this upon chemoresponsive exposure to triphenylphosphine (Ph3P) ligands, whereas the MPN provide structural integrity. Depending on the metal-ion concentration used during synthesis of the MPN, the degree of swelling of the coordination polymer networks could be adjusted. Once the MPN was immersed into Ph3P solution, the reversible ligand-exchange reaction between the metal ions and the free Ph3P in solution causes a decrease of the coordination cross-link density in MPN again. The Ph3P-treated MPN was able to maintain its original shape, indicating a certain stability of shape even after stimulation. In this way, chemoresponsive control of the elastic properties (increase in volume and decrease of mechanical strength) of the MPN was demonstrated. This remarkable behavior motivated us to explore whether the MPN are capable of a chemoresponsive shape-memory effect. In initial experiments, shape fixity of around 60% and shape recovery of almost 90% were achieved when the MPN was exposed to Ph3P in case of rhodium. Potential applications for chemoresponsive shape-memory systems could be shapable semiconductors, e.g., for lighting or catalysts, which provide catalytic activity on demand. Y1 - 2019 U6 - https://doi.org/10.1021/acs.chemmater.9b00363 SN - 0897-4756 SN - 1520-5002 VL - 31 IS - 15 SP - 5402 EP - 5407 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Garakani, Tayebeh Mirzaei A1 - Liu, Zhanzhi A1 - Glebe, Ulrich A1 - Gehrmann, Julia A1 - Lazar, Jaroslav A1 - Mertens, Marie Anna Stephanie A1 - Möller, Mieke A1 - Hamzelui, Niloofar A1 - Zhu, Leilei A1 - Schnakenberg, Uwe A1 - Böker, Alexander A1 - Schwaneberg, Ulrich T1 - In Situ Monitoring of Membrane Protein Insertion into Block Copolymer Vesicle Membranes and Their Spreading via Potential-Assisted Approach JF - ACS applied materials & interfaces N2 - Synthosomes are polymer vesicles with trans membrane proteins incorporated into block copolymer membranes. They have been used for selective transport in or out of the vesicles as well as catalysis inside the compartments. However, both the insertion process of the membrane protein, forming nanopores, and the spreading of the vesicles on planar substrates to form solid-supported biomimetic membranes have been rarely studied yet. Herein, we address these two points and, first, shed light on the real-time monitoring of protein insertion via isothermal titration calorimetry. Second, the spreading process on different solid supports, namely, SiO2, glass, and gold, via different techniques like spin- and dip-coating as well as a completely new approach of potential-assisted spreading on gold surfaces was studied. While inhomogeneous layers occur via traditional methods, our proposed potential-assisted strategy to induce adsorption of positively charged vesicles by applying negative potential on the electrode leads to remarkable vesicle spreading and their further fusion to form more homogeneous planar copolymer films on gold. The polymer vesicles in our study are formed from amphiphilic copolymers poly(2-methyl oxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyl oxazoline) (PMOXA-b-PDMS-b-PMOXA). Engineered variants of the transmembrane protein ferric hydroxamate uptake protein component A (FhuA), one of the largest beta-barrel channel proteins, are used as model nanopores. The incorporation of FhuA Delta 1-160 is shown to facilitate the vesicle spreading process further. Moreover, high accessibility of cysteine inside the channel was proven by linkage of a fluorescent dye inside the engineered variant FhuA Delta CVFtev and hence preserved functionality of the channels after spreading. The porosity and functionality of the spread synthosomes on the gold plates have been examined by studying the passive ion transport response in the presence of Li+ and ClO4- ions and electrochemical impedance spectroscopy analysis. Our approach to form solid-supported biomimetic membranes via the potential-assisted strategy could be important for the development of new (bio-) sensors and membranes. KW - synthosomes KW - solid-supported biomimetic membranes KW - polymersome spreading KW - electrochemical impedance spectroscopy KW - FhuA Y1 - 2019 U6 - https://doi.org/10.1021/acsami.9b09302 SN - 1944-8244 SN - 1944-8252 VL - 11 IS - 32 SP - 29276 EP - 29289 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Friess, Fabian A1 - Roch, Toralf A1 - Seifert, Barbara A1 - Lendlein, Andreas A1 - Wischke, Christian T1 - Phagocytosis of spherical and ellipsoidal micronetwork colloids from crosslinked poly(epsilon-caprolactone) JF - International Journal of Pharmaceutics N2 - The effect of non-spherical particle shapes on cellular uptake has been reported as a general design parameter to control cellular recognition of particulate drug carriers. Beside shape, also size and cell-particle ratio should mutually effect phagocytosis. Here, the capability to control cellular uptake of poly(epsilon-caprolactone) (PCL) based polymer micronetwork colloids (MNC), a carrier system that can be transferred to various shapes, is explored in vitro at test conditions allowing multiple cell-particle contacts. PCL-based MNC were synthesized as spheres with a diameter of similar to 6, similar to 10, and 13 mu m, loaded with a fluorescent dye by a specific technique of swelling, redispersion and drying, and transferred into different ellipsoidal shapes by a phantom stretching method. The boundaries of MNC deformability to prolate ellipsoid target shapes were systematically analyzed and found to be at an aspect ratio AR of similar to 4 as obtained by a phantom elongation epsilon(ph) of similar to 150%. Uptake studies with a murine macrophages cell line showed shape dependency of phagocytosis for selected conditions when varying particle sizes (similar to 6 and 10 mu m),and shapes (epsilon(ph): 0, 75 or 150%), cell-particle ratios (1:1, 1:2, 1:10, 1:50), and time points (1-24 h). For larger-sized MNC, there was no significant shape effect on phagocytosis as these particles may associate with more than one cell, thus increasing the possibility of phagocytosis by any of these cells. Accordingly, controlling shape effects on phagocytosis for carriers made from degradable polymers relevant for medical applications requires considering further parameters besides shape, such as kinetic aspects of the exposure and uptake by cells. KW - Particle shape KW - Phagocytosis KW - Macrophage KW - Polymer micronetwork colloids KW - Poly(epsilon-caprolactone) Y1 - 2019 U6 - https://doi.org/10.1016/j.ijpharm.2019.118461 SN - 0378-5173 SN - 1873-3476 VL - 567 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Benzyne - an acetylene- or cumulene-like electronic structure? JF - Tetrahedron N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzyne 1 and analogues (benzene 2, 1,2,3-cyclohexatriene 3, cyclohexen-3-yne 4, cyclohexen-4-yne 5, cyclohexyne 6) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values could be employed to compare the diatropic ring current effects of benzene and benzyne, and, when compared with the spatial magnetic properties of the analogues, to answer the question whether the benzyne electronic structure is more acetylene- or cumulene-like, supported by structural data and delta(C-13)/ppm values. (C) 2019 Published by Elsevier Ltd. KW - Benzyne-allene or cumulene-like structure KW - Trough-space NMR shieldings (TSNMRS) KW - NICS KW - Iso-chemical shielding surfaces (ICSS) KW - Ring current effect Y1 - 2019 U6 - https://doi.org/10.1016/j.tet.2019.07.011 SN - 0040-4020 VL - 75 IS - 33 SP - 4663 EP - 4668 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Schultze, Christiane A1 - Schmidt, Bernd T1 - Functionalized Benzofurans via Microwave-Promoted Tandem Claisen-Rearrangement/5-endo-dig Cyclization JF - Journal of heterocyclic chemistry N2 - Ortho-allyloxy alkinyl benzenes undergo, upon microwave irradiation in dimethylformamide, a tandem sequence of Claisen-rearrangement and 5-endo-dig cyclization to furnish 7-allyl-substituted benzofurans. With terminal alkynes, chroman-4-ones and enaminoketones become the main products. A mechanistic proposal for this observation relies on a reaction of the starting material with the solvent dimethylformamide under the microwave conditions. Y1 - 2019 U6 - https://doi.org/10.1002/jhet.3671 SN - 0022-152X SN - 1943-5193 VL - 56 IS - 9 SP - 2619 EP - 2629 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Schwarze, Thomas A1 - Riemer, Janine A1 - Müller, Holger A1 - John, Leonard A1 - Holdt, Hans-Jürgen A1 - Wessig, Pablo T1 - Na+ Selective Fluorescent Tools Based on Fluorescence Intensity Enhancements, Lifetime Changes, and on a Ratiometric Response JF - Chemistry - a European journal N2 - Over the years, we developed highly selective fluorescent probes for K+ in water, which show K+-induced fluorescence intensity enhancements, lifetime changes, or a ratiometric behavior at two emission wavelengths (cf. Scheme 1, K1-K4). In this paper, we introduce selective fluorescent probes for Na+ in water, which also show Na+ induced signal changes, which are analyzed by diverse fluorescence techniques. Initially, we synthesized the fluorescent probes 2, 4, 5, 6 and 10 for a fluorescence analysis by intensity enhancements at one wavelength by varying the Na+ responsive ionophore unit and the fluorophore moiety to adjust different K-d values for an intra- or extracellular Na+ analysis. Thus, we found that 2, 4 and 5 are Na+ selective fluorescent tools, which are able to measure physiologically important Na+ levels at wavelengths higher than 500 nm. Secondly, we developed the fluorescent probes 7 and 8 to analyze precise Na+ levels by fluorescence lifetime changes. Herein, only 8 (K-d=106 mm) is a capable fluorescent tool to measure Na+ levels in blood samples by lifetime changes. Finally, the fluorescent probe 9 was designed to show a Na+ induced ratiometric fluorescence behavior at two emission wavelengths. As desired, 9 (K-d=78 mm) showed a ratiometric fluorescence response towards Na+ ions and is a suitable tool to measure physiologically relevant Na+ levels by the intensity change of two emission wavelengths at 404 nm and 492 nm. KW - crown compounds KW - fluorescence lifetime KW - fluorescent probes KW - ratiometric KW - sodium Y1 - 2019 U6 - https://doi.org/10.1002/chem.201902536 SN - 0947-6539 SN - 1521-3765 VL - 25 IS - 53 SP - 12412 EP - 12422 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Rosencrantz, Sophia A1 - Tang, Jo Sing Julia A1 - Schulte-Osseili, Christine A1 - Böker, Alexander A1 - Rosencrantz, Ruben R. T1 - Glycopolymers by RAFT Polymerization as Functional Surfaces for Galectin-3 JF - Macromolecular chemistry and physics N2 - Glycan-protein interactions are essential biological processes with many disease-related modulations and variations. One of the key proteins involved in tumor progression and metastasis is galectin-3 (Gal-3). A lot of effort is put into the development of Gal-3 inhibitors as new therapeutic agents. The avidity of glycan-protein interactions is strongly enhanced by multivalent ligand presentation. Multivalent presentation of glycans can be accomplished by utilizing glycopolymers, which are polymers with pendent glycan groups. For the production of glycopolymers, glycomonomers are synthesized by a regioselective, microwave-assisted approach starting from lactose. The resulting methacrylamide derivatives are polymerized by RAFT and immobilized on gold surfaces using the trithiocarbonate group of the chain transfer agent. Surface plasmon resonance spectroscopy enables the label free kinetic characterization of Gal-3 binding to these multivalent glycopolymers. The measurements indicate oligomerization of Gal-3 upon exposure to multivalent environments and reveal strong specific interaction with the immobilized polymers. KW - galectin-3 KW - glycopolymers KW - multivalency KW - RAFT KW - surface plasmon resonance Y1 - 2019 U6 - https://doi.org/10.1002/macp.201900293 SN - 1022-1352 SN - 1521-3935 VL - 220 IS - 20 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Sperling, Marcel A1 - Reifarth, Martin A1 - Grobe, Richard A1 - Böker, Alexander T1 - Tailoring patches on particles: a modified microcontact printing routine using polymer-functionalised stamps JF - Chemical communications N2 - Herein, we report a modified microcontact printing (mu CP) routine suitable to introduce particle patches of a low molecular weight ink (LMWI) on porous SiO2 microparticles. Thereby, patch precision could be significantly improved by utilising stamps which have been surface-functionalised with grafted polymers. This improvement was evaluated by a profound software-assisted statistical analysis. Y1 - 2019 U6 - https://doi.org/10.1039/c9cc03903a SN - 1359-7345 SN - 1364-548X VL - 55 IS - 68 SP - 10104 EP - 10107 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Schürmann, Robin Mathis A1 - Pacholski, Claudia T1 - One Spot-Two Sensors: Porous Silicon Interferometers in Combination With Gold Nanostructures Showing Localized Surface Plasmon Resonance JF - Frontiers in chemistry N2 - Sensors composed of a porous silicon monolayer covered with a film of nanostructured gold layer, which provide two optical signal transduction methods, are fabricated and thoroughly characterized concerning their sensing performance. For this purpose, silicon substrates were electrochemically etched in order to obtain porous silicon monolayers, which were subsequently immersed in gold salt solution facilitating the formation of a porous gold nanoparticle layer on top of the porous silicon. The deposition process was monitored by reflectance spectroscopy, and the appearance of a dip in the interference pattern of the porous silicon layer was observed. This dip can be assigned to the absorption of light by the deposited gold nanostructures leading to localized surface plasmon resonance. The bulk sensitivity of these sensors was determined by recording reflectance spectra in media having different refractive indices and compared to sensors exclusively based on porous silicon or gold nanostructures. A thorough analysis of resulting shifts of the different optical signals in the reflectance spectra on the wavelength scale indicated that the optical response of the porous silicon sensor is not influenced by the presence of a gold nanostructure on top. Moreover, the adsorption of thiol-terminated polystyrene to the sensor surface was solely detected by changes in the position of the dip in the reflectance spectrum, which is assigned to localized surface plasmon resonance in the gold nanostructures. The interference pattern resulting from the porous silicon layer is not shifted to longer wavelengths by the adsorption indicating the independence of the optical response of the two nanostructures, namely porous silicon and nanostructured gold layer, to refractive index changes and pointing to the successful realization of two sensors in one spot. KW - porous silicon KW - interferometry KW - gold nanostructures KW - surface plasmon resonance KW - optical sensor Y1 - 2019 U6 - https://doi.org/10.3389/fchem.2019.00593 SN - 2296-2646 VL - 7 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Lai, Feili A1 - Feng, Jianrui A1 - Heil, Tobias A1 - Tian, Zhihong A1 - Schmidt, Johannes A1 - Wang, Gui-Chang A1 - Oschatz, Martin T1 - Partially delocalized charge in Fe-doped NiCo2S4 nanosheet-mesoporous carbon-composites for high-voltage supercapacitors JF - Journal of materials chemistry : A, Materials for energy and sustainability N2 - Unraveling the effect of transition-metal doping on the energy storage properties of bimetallic sulfides remains a grand challenge. Herein, we construct bimetallic sulfide nanosheets and hence deliberately introduce transition-metal doping domains on their surface. The resulting materials show not only an enhanced density of states near the Fermi level but also partially delocalized charge as shown by density functional theory (DFT) calculations. Fe-doped NiCo2S4 nanosheets wrapped on N,S-doped ordered mesoporous carbon (Fe-NiCo2S4@N,S-CMK-3) are prepared, which show an enhanced specific capacitance of 197.8 F g(-1) in ionic liquid-based supercapacitors at a scan rate of 2 mV s(-1). This is significantly higher as compared to the capacitance of 155.2 and 135.9 F g(-1) of non-iron-doped NiCo2S4@N,S-CMK and Fe-NiCo2S4@CMK-3 electrodes, respectively. This result arises from the enhanced ionic liquid polarization effect and transportation ability from the Fe-NiCo2S4 surface and N,S-CMK-3 structure. Furthermore, the importance of matching multi-dimensional structures and ionic liquid ion sizes in the fabrication of asymmetric supercapacitors (ASCs) is demonstrated. As a result, the ASC device exhibits a high energy density of 107.5 W h kg(-1) at a power density of 100 W kg(-1) in a working-voltage window of 4 V when using Fe-NiCo2S4@N,S-CMK-3 and N,S-CMK-3 as positive and negative electrodes, respectively. This work puts forward a new direction to design supercapacitor composite electrodes for efficient ionic liquid coupling. Y1 - 2019 U6 - https://doi.org/10.1039/c9ta06250e SN - 2050-7488 SN - 2050-7496 VL - 7 IS - 33 SP - 19342 EP - 19347 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Reinicke, Stefan A1 - Fischer, Thilo A1 - Bramski, Julia A1 - Pietruszka, Jörg A1 - Böker, Alexander T1 - Biocatalytically active microgels by precipitation polymerization of N-isopropyl acrylamide in the presence of an enzyme JF - RSC Advances N2 - We present a novel protocol for the synthesis of enzymatically active microgels. The protocol is based on the precipitation polymerization of N-isopropylacrylamide (NIPAm) in the presence of an enzyme and a protein binding comonomer. A basic investigation on the influence of different reaction parameters such as monomer concentration and reaction temperature on the microgel size and size distribution is performed and immobilization yields are determined. Microgels exhibiting hydrodynamic diameters between 100 nm and 1 mu m and narrow size distribution could be synthesized while about 31-44% of the enzyme present in the initial reaction mixture can be immobilized. Successful immobilization including a verification of enzymatic activity of the microgels is achieved for glucose oxidase (GOx) and 2-deoxy-d-ribose-5-phosphate aldolase (DERA). The thermoresponsive properties of the microgels are assessed and discussed in the light of activity evolution with temperature. The positive correlation of enzymatic activity with temperature for the GOx containing microgel originates from a direct interaction of the enzyme with the PNIPAm based polymer matrix whose magnitude is highly influenced by temperature. Y1 - 2019 U6 - https://doi.org/10.1039/c9ra04000e SN - 2046-2069 VL - 9 IS - 49 SP - 28377 EP - 28386 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Shou, Keyun A1 - Bremer, Anne A1 - Rindfleisch, Tobias A1 - Knox-Brown, Patrick A1 - Hirai, Mitsuhiro A1 - Rekas, Agata A1 - Garvey, Christopher J. A1 - Hincha, Dirk K. A1 - Stadler, Andreas M. A1 - Thalhammer, Anja T1 - Conformational selection of the intrinsically disordered plant stress protein COR15A in response to solution osmolarity - an X-ray and light scattering study JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - The plant stress protein COR15A stabilizes chloroplast membranes during freezing. COR15A is an intrinsically disordered protein (IDP) in aqueous solution, but acquires an alpha-helical structure during dehydration or the increase of solution osmolarity. We have used small- and wide-angle X-ray scattering (SAXS/WAXS) combined with static and dynamic light scattering (SLS/DLS) to investigate the structural and hydrodynamic properties of COR15A in response to increasing solution osmolarity. Coarse-grained ensemble modelling allowed a structure-based interpretation of the SAXS data. Our results demonstrate that COR15A behaves as a biomacromolecule with polymer-like properties which strongly depend on solution osmolarity. Biomacromolecular self-assembly occurring at high solvent osmolarity is initiated by the occurrence of two specific structural subpopulations of the COR15A monomer. The osmolarity dependent structural selection mechanism is an elegant way for conformational regulation and assembly of COR15A. It highlights the importance of the polymer-like properties of IDPs for their associated biological function. Y1 - 2019 U6 - https://doi.org/10.1039/c9cp01768b SN - 1463-9076 SN - 1463-9084 VL - 21 IS - 34 SP - 18727 EP - 18740 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kuroki, Agnes A1 - Tchoupa, Arnaud Kengmo A1 - Hartlieb, Matthias A1 - Peltier, Raoul A1 - Locock, Katherine E. S. A1 - Unnikrishnan, Meera A1 - Perrier, Sebastien T1 - Targeting intracellular, multi-drug resistant Staphylococcus aureus with guanidinium polymers by elucidating the structure-activity relationship JF - Biomaterials : biomaterials reviews online N2 - Intracellular persistence of bacteria represents a clinical challenge as bacteria can thrive in an environment protected from antibiotics and immune responses. Novel targeting strategies are critical in tackling antibiotic resistant infections. Synthetic antimicrobial peptides (SAMPs) are interesting candidates as they exhibit a very high antimicrobial activity. We first compared the activity of a library of ammonium and guanidinium polymers with different sequences (statistical, tetrablock and diblock) synthesized by RAFT polymerization against methicillin-resistant S. aureus (MRSA) and methicillin-sensitive strains (MSSA). As the guanidinium SAMPs were the most potent, they were used to treat intracellular S. aureus in keratinocytes. The diblock structure was the most active, reducing the amount of intracellular MSSA and MRSA by two-fold. We present here a potential treatment for intracellular, multi-drug resistant bacteria, using a simple and scalable strategy. KW - Antimicrobial KW - Intracellular bacteria KW - Block copolymers KW - RAFT polymerization Y1 - 2019 U6 - https://doi.org/10.1016/j.biomaterials.2019.119249 SN - 0142-9612 SN - 1878-5905 VL - 217 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Walczak, Ralf A1 - Savateev, Aleksandr A1 - Heske, Julian A1 - Tarakina, Nadezda V. A1 - Sahoo, Sudhir A1 - Epping, Jan D. A1 - Kuehne, Thomas D. A1 - Kurpil, Bogdan A1 - Antonietti, Markus A1 - Oschatz, Martin T1 - Controlling the strength of interaction between carbon dioxide and nitrogen-rich carbon materials by molecular design JF - Sustainable energy & fuels N2 - Thermal treatment of hexaazatriphenylene-hexacarbonitrile (HAT-CN) in the temperature range from 500 degrees C to 700 degrees C leads to precise control over the degree of condensation, and thus atomic construction and porosity of the resulting C2N-type materials. Depending on the condensation temperature of HAT-CN, nitrogen contents of more than 30 at% can be reached. In general, these carbons show adsorption properties which are comparable to those known for zeolites but their pore size can be adjusted over a wider range. At condensation temperatures of 525 degrees C and below, the uptake of nitrogen gas remains negligible due to size exclusion, but the internal pores are large and polarizing enough that CO2 can still adsorb on part of the internal surface. This leads to surprisingly high CO2 adsorption capacities and isosteric heat of adsorption of up to 52 kJ mol(-1). Theoretical calculations show that this high binding enthalpy arises from collective stabilization effects from the nitrogen atoms in the C2N layers surrounding the carbon atom in the CO2 molecule and from the electron acceptor properties of the carbon atoms from C2N which are in close proximity to the oxygen atoms in CO2. A true CO2 molecular sieving effect is achieved for the first time in such a metal-free organic material with zeolite-like properties, showing an IAST CO2/N-2 selectivity of up to 121 at 298 K and a N-2/CO2 ratio of 90/10 without notable changes in the CO2 adsorption properities over 80 cycles. Y1 - 2019 U6 - https://doi.org/10.1039/c9se00486f SN - 2398-4902 VL - 3 IS - 10 SP - 2819 EP - 2827 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Jia, He A1 - Quan, Ting A1 - Liu, Xuelian A1 - Bai, Lu A1 - Wang, Jiande A1 - Boujioui, Fadoi A1 - Ye, Ran A1 - Vald, Alexandru A1 - Lu, Yan A1 - Gohy, Jean-Francois T1 - Core-shell nanostructured organic redox polymer cathodes with superior performance JF - Nano Energy N2 - Core-shell nanoparticles stabilized by a cationic surfactant are prepared from the poly(2,2,6,6-tetra-methylpiperidinyloxy-4-yl methacrylate) redox polymer. The nanoparticles are further self-assembled with negatively charged reduced graphene oxide nanosheets and negatively charged mull-walled carbon nanotubes. This results in the formation of a free-standing cathode with a layered nanostructure and a high content of redox polymer that exhibits 100% utilization of the active substance with a measured capacity as high as 105 mAh/g based on the whole weight of the electrode. KW - Nanostructured KW - Redox polymer KW - Organic electrode KW - Lithium ion battery KW - Energy storage Y1 - 2019 U6 - https://doi.org/10.1016/j.nanoen.2019.103949 SN - 2211-2855 SN - 2211-3282 VL - 64 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Lendlein, Andreas A1 - Balk, Maria A1 - Tarazona, Natalia A. A1 - Gould, Oliver E. C. T1 - Bioperspectives for Shape-Memory Polymers as Shape Programmable, Active Materials JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - Within the natural world, organisms use information stored in their material structure to generate a physical response to a wide variety of environmental changes. The ability to program synthetic materials to intrinsically respond to environmental changes in a similar manner has the potential to revolutionize material science. By designing polymeric devices capable of responsively changing shape or behavior based on information encoded into their structure, we can create functional physical behavior, including a shape memory and an actuation capability. Here we highlight the stimuli-responsiveness and shape-changing ability of biological materials and biopolymer-based materials, plus their potential biomedical application, providing a bioperspective on shape-memory materials. We address strategies to incorporate a shape memory (actuation) function in polymeric materials, conceptualized in terms of its relationship with inputs (environmental stimuli) and outputs (shape change). Challenges and opportunities associated with the integration of several functions in a single material body to achieve multifunctionality are discussed. Finally, we describe how elements that sense, convert, and transmit stimuli have been used to create multisensitive materials. Y1 - 2019 U6 - https://doi.org/10.1021/acs.biomac.9b01074 SN - 1525-7797 SN - 1526-4602 VL - 20 IS - 10 SP - 3627 EP - 3640 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Miedema, Piter S. A1 - Thielemann-Kühn, Nele A1 - Calafell, Irati Alonso A1 - Schüßler-Langeheine, Christian A1 - Beye, Martin T1 - Strain analysis from M-edge resonant inelastic X-ray scattering of nickel oxide films JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Electronic structure modifications due to strain are an effective method for tailoring nano-scale functional materials. Demonstrated on nickel oxide (NiO) thin films, Resonant Inelastic X-ray Scattering (RIXS) at the transition-metal M-2,M-3-edge is shown to be a powerful tool for measuring the electronic structure modification due to strain in the near-surface region. Analyses from the M-2,M-3-edge RIXS in comparison with dedicated crystal field multiplet calculations show distortions in 40 nm NiO grown on a magnesium oxide (MgO) substrate (NiO/MgO) similar to those caused by surface relaxation of bulk NiO. The films of 20 and 10 nm NiO/MgO show slightly larger differences from bulk NiO. Quantitatively, the NiO/MgO samples all are distorted from perfect octahedral (O-h) symmetry with a tetragonal parameter Ds of about -0.1 eV, very close to the Ds distortion from octahedral (O-h) symmetry parameter of -0.11 eV obtained for the surface-near region from a bulk NiO crystal. Comparing the spectra of a 20 nm film of NiO grown on a 20 nm magnetite (Fe3O4) film on a MgO substrate (NiO/Fe3O4/MgO) with the calculated multiplet analyses, the distortion parameter Ds appears to be closer to zero, showing that the surface-near region of this templated film is less distorted from O-h symmetry than the surface-near region in bulk NiO. Finally, the potential of M-2,M-3-edge RIXS for other investigations of strain on electronic structure is discussed. Y1 - 2019 U6 - https://doi.org/10.1039/c9cp03593a SN - 1463-9076 SN - 1463-9084 VL - 21 IS - 38 SP - 21596 EP - 21602 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Braune, Steffen A1 - Latour, Robert A. A1 - Reinthaler, Markus A1 - Landmesser, Ulf A1 - Lendlein, Andreas A1 - Jung, Friedrich T1 - In Vitro Thrombogenicity Testing of Biomaterials JF - Advanced healthcare materials N2 - The short- and long-term thrombogenicity of implant materials is still unpredictable, which is a significant challenge for the treatment of cardiovascular diseases. A knowledge-based approach for implementing biofunctions in materials requires a detailed understanding of the medical device in the biological system. In particular, the interplay between material and blood components/cells as well as standardized and commonly acknowledged in vitro test methods allowing a reproducible categorization of the material thrombogenicity requires further attention. Here, the status of in vitro thrombogenicity testing methods for biomaterials is reviewed, particularly taking in view the preparation of test materials and references, the selection and characterization of donors and blood samples, the prerequisites for reproducible approaches and applied test systems. Recent joint approaches in finding common standards for a reproducible testing are summarized and perspectives for a more disease oriented in vitro thrombogenicity testing are discussed. KW - biomaterials KW - blood tests KW - implants KW - in vitro KW - thrombogenicity Y1 - 2019 U6 - https://doi.org/10.1002/adhm.201900527 SN - 2192-2640 SN - 2192-2659 VL - 8 IS - 21 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Xiong, Tao A1 - Saalfrank, Peter T1 - Vibrationally Broadened Optical Spectra of Selected Radicals and Cations Derived from Adamantane: A Time-Dependent Correlation Function Approach JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - Diamondoids are hydrogen-saturated molecular motifs cut out of diamond, forming a class of materials with tunable optoelectronic properties. In this work, we extend previous work on neutral, closed-shell diamondoids by computing with hybrid density functional theory and time-dependent correlation functions vibrationally broadened absorption spectra of cations and radicals derived from the simplest diamondoid, adamantane, namely, the neutral 1- and 2-adamantyl radicals (C10H15), the 1- and 2-adamantyl cations (C10H15+), and the adamantane radical cation (C10H16+). For selected cases, we also report vibrationally broadened emission, photoelectron, and resonance Raman spectra. Furthermore, the effect of the damping factor on the vibrational fine-structure is studied. The following trends are found: (1) Low-energy absorptions of the adamantyl radicals and cations, and of the adamantane cation, are all strongly red-shifted with respect to adamantane; (2) also, emission spectra are strongly red-shifted, whereas photoelectron spectra are less affected for the cases studied; (3) vibrational fine-structures are reduced compared to those of adamantane; (4) the spectroscopic signals of 1- and 2-adamantyl species are significantly different from each other; and (5) reducing the damping factor has only a limited effect on the vibrational fine-structure in most cases. This suggests that removing hydrogen atoms and/or electrons from adamantane leads to new optoelectronic properties, which should be detectable by vibronic spectroscopy. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpca.9b03305 SN - 1089-5639 SN - 1520-5215 VL - 123 IS - 41 SP - 8871 EP - 8880 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Sass, Stephan A1 - Stöcklein, Walter F. M. A1 - Klevesath, Anja A1 - Hurpin, Jeanne A1 - Menger, Marcus A1 - Hille, Carsten T1 - Binding affinity data of DNA aptamers for therapeutic anthracyclines from microscale thermophoresis and surface plasmon resonance spectroscopy JF - The analyst : the analytical journal of the Royal Society of Chemistry N2 - Anthracyclines like daunorubicin (DRN) and doxorubicin (DOX) play an undisputed key role in cancer treatment, but their chronic administration can cause severe side effects. For precise anthracycline analytical systems, aptamers are preferable recognition elements. Here, we describe the detailed characterisation of a single-stranded DNA aptamer DRN-10 and its truncated versions for DOX and DRN detection. Binding affinities were determined from surface plasmon resonance (SPR) and microscale thermophoresis (MST) and combined with conformational data from circular dichroism (CD). Both aptamers displayed similar nanomolar binding affinities to DRN and DOX, even though their rate constants differed as shown by SPR recordings. SPR kinetic data unravelled a two-state reaction model including a 1 : 1 binding and a subsequent conformational change of the binding complex. This model was supported by CD spectra. In addition, the dissociation constants determined with MST were always lower than that from SPR, and especially for the truncated aptamer they differed by two orders of magnitude. This most probably reflects the methodological difference, namely labelling for MST vs. immobilisation for SPR. From CD recordings, we suggested a specific G-quadruplex as structural basis for anthracycline binding. We concluded that the aptamer DRN-10 is a promising recognition element for anthracycline detection systems and further selected aptamers can be also characterised with the combined methodological approach presented here. Y1 - 2019 U6 - https://doi.org/10.1039/c9an01247h SN - 0003-2654 SN - 1364-5528 VL - 144 IS - 20 SP - 6064 EP - 6073 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Wolff, Christian Michael A1 - Caprioglio, Pietro A1 - Stolterfoht, Martin A1 - Neher, Dieter T1 - Nonradiative Recombination in Perovskite Solar Cells BT - the Role of Interfaces JF - Advanced materials N2 - Perovskite solar cells combine high carrier mobilities with long carrier lifetimes and high radiative efficiencies. Despite this, full devices suffer from significant nonradiative recombination losses, limiting their V-OC to values well below the Shockley-Queisser limit. Here, recent advances in understanding nonradiative recombination in perovskite solar cells from picoseconds to steady state are presented, with an emphasis on the interfaces between the perovskite absorber and the charge transport layers. Quantification of the quasi-Fermi level splitting in perovskite films with and without attached transport layers allows to identify the origin of nonradiative recombination, and to explain the V-OC of operational devices. These measurements prove that in state-of-the-art solar cells, nonradiative recombination at the interfaces between the perovskite and the transport layers is more important than processes in the bulk or at grain boundaries. Optical pump-probe techniques give complementary access to the interfacial recombination pathways and provide quantitative information on transfer rates and recombination velocities. Promising optimization strategies are also highlighted, in particular in view of the role of energy level alignment and the importance of surface passivation. Recent record perovskite solar cells with low nonradiative losses are presented where interfacial recombination is effectively overcome-paving the way to the thermodynamic efficiency limit. KW - interfacial recombination KW - open-circuit voltage KW - perovskite solar cells KW - photoluminescence Y1 - 2019 U6 - https://doi.org/10.1002/adma.201902762 SN - 0935-9648 SN - 1521-4095 VL - 31 IS - 52 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kopyshev, Alexey A1 - Kanevche, Katerina A1 - Lomadze, Nino A1 - Pfitzner, Emanuel A1 - Loebner, Sarah A1 - Patil, Rohan R. A1 - Genzer, Jan A1 - Heberle, Joachim A1 - Santer, Svetlana T1 - Light-Induced Structuring of Photosensitive Polymer Brushes JF - ACS Applied polymer materials N2 - We investigate light-induced irreversible structuring of surface topographies in poly(3-sulfopropyl methacrylate/potassium salt) (PSPMK) brushes on flat solid substrates prepared by surface-initiated atom transfer radical polymerization. The brushes have been loaded with azobenzene-based surfactant comprised of positively charged headgroups and hydrophobic tail. The surfactant exhibits photoresponsive properties through photoisomerization from the trans to cis states leading to significant changes in physicochemical properties of grafted polymer chains. The azobenzene surfactant enables photoresponsive behavior without introducing irreversible changes to chemical composition of the parent polymer brush. Exposing these photosensitive brushes to irradiation with UV interference beams causes the polymer brush to form surface relief grating (SRG) patterns. The cationic surfactant penetrates only similar to 25% of the upper portion of the PSPMK brush, resulting in the formation of two sections within the brush: a photoresponsive upper layer and nonfunctional buried layer, which is not affected by the UV irradiation. Using nano-FTIR spectroscopy, we characterize locally the chemical composition of the polymer brush and confirm partial penetration of the surfactant within the film. Strong optomechanical stresses take place only within the upper layer of the brush that is impregnated with the surfactants and causes surface topography alternation due to a local rupture of grafted polymer chains. The cleaved polymer chains are then removed from the surface by using a good solvent, leaving behind topographical grating on top of the nonfunctional brush layer. We demonstrate that photostructured polymer brush can be used for reversible switching of brush topography by varying external humidity. KW - photosensitive polymer brushes KW - reversible and irreversible structuring of polymer brushes KW - photosensitive azobenzene containing surfactant KW - strong polyelectrolyte brush KW - SRG formation in polymer brushes Y1 - 2019 U6 - https://doi.org/10.1021/acsapm.9b00705 SN - 2637-6105 VL - 1 IS - 11 SP - 301 EP - 3026 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Qin, Qing A1 - Heil, T. A1 - Schmidt, J. A1 - Schmallegger, Max A1 - Gescheidt, Georg A1 - Antonietti, Markus A1 - Oschatz, Martin T1 - Electrochemical Fixation of Nitrogen and Its Coupling with Biomass Valorization with a Strongly Adsorbing and Defect Optimized Boron-Carbon-Nitrogen Catalyst JF - ACS Applied Energy Materials N2 - The electrochemical conversion of low-cost precursors into high-value chemicals using renewably generated electricity is a promising approach to build up an environmentally friendly energy cycle, including a storage element. The large-scale implementation of such process can, however, only be realized by the design of cost-effective electrocatalysts with high efficiency and highest stability. Here, we report the synthesis of N and B codoped porous carbons. The constructed B-N motives combine abundant unpaired electrons and frustrated Lewis pairs (FLPs). They result in desirable performance for electrochemical N-2 reduction reaction (NRR) and electrooxidation of 5-hydroxymethylfurfural (HMF) in the absence of any metal cocatalyst. A maximum Faradaic efficiency of 15.2% with a stable NH3 production rate of 21.3 mu g h(-1) mg(-1) is obtained in NRR. Besides, 2,5-furandicarboxylic acid (FDCA) is first obtained by using non-metalbased electrocatalysts at a conversion of 71% and with yield of 57%. Gas adsorption experiments elucidate the relationship between the structure and the ability of the catalysts to activate the substrate molecules. This work opens up deep insights for the rational design of non-metal-based catalysts for potential electrocatalytic applications and the possible enhancement of their activity by the introduction of FLPs and point defects at grain boundaries. KW - non-metal catalysis KW - porous carbon KW - heteroatoms KW - N-2 reduction KW - HMF oxidation Y1 - 2019 U6 - https://doi.org/10.1021/acsaem.9b01852 SN - 2574-0962 VL - 2 IS - 11 SP - 8359 EP - 8365 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Yang, Guang A1 - Zheng, Wei A1 - Tao, Guoqing A1 - Wu, Libin A1 - Zhou, Qi-Feng A1 - Kochovski, Zdravko A1 - Ji, Tan A1 - Chen, Huaijun A1 - Li, Xiaopeng A1 - Lu, Yan A1 - Ding, Hong-ming A1 - Yang, Hai-Bo A1 - Chen, Guosong A1 - Jiang, Ming T1 - Diversiform and Transformable Glyco-Nanostructures Constructed from Amphiphilic Supramolecular Metallocarbohydrates through Hierarchical Self-Assembly: The Balance between Metallacycles and Saccharides JF - ACS nano N2 - During the past decade, self-assembly of saccharide-containing amphiphilic molecules toward bioinspired functional glycomaterials has attracted continuous attention due to their various applications in fundamental and practical areas. However, it still remains a great challenge to prepare hierarchical glycoassemblies with controllable and diversiform structures because of the complexity of saccharide structures and carbohydrate-carbohydrate interactions. Herein, through hierarchical self-assembly of modulated amphiphilic supramolecular metallocarbohydrates, we successfully prepared various well-defined glyco-nanostructures in aqueous solution, including vesicles, solid spheres, and opened vesicles depending on the molecular structures of metallocarbohydrates. More attractively, these glyco-nanostructures can further transform into other morphological structures in aqueous solutions such as worm-like micelles, tubules, and even tupanvirus-like vesicles (TVVs). It is worth mentioning that distinctive anisotropic structures including the opened vesicles (OVs) and TVVs were rarely reported in glycobased nano-objects. This intriguing diversity was mainly controlled by the subtle structural trade-off of the two major components of the amphiphiles, i.e., the saccharides and metallacycles. To further understand this precise structural control, molecular simulations provided deep physical insights on the morphology evolution and balancing of the contributions from saccharides and metallacycles. Moreover, the multivalency of glyco-nanostructures with different shapes and sizes was demonstrated by agglutination with a diversity of sugarbinding protein receptors such as the plant lectins Concanavalin A (ConA). This modular synthesis strategy provides access to systematic tuning of molecular structure and self-assembled architecture, which undoubtedly will broaden our horizons on the controllable fabrication of biomimetic glycomaterials such as biological membranes and supramolecular lectin inhibitors. KW - glycomaterials KW - diversiform structures KW - hierarchical self-assembly KW - metallocarbohydrates KW - anisotropic structures Y1 - 2019 U6 - https://doi.org/10.1021/acsnano.9b07134 SN - 1936-0851 SN - 1936-086X VL - 13 IS - 11 SP - 13474 EP - 13485 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Suslova, Elena N. A1 - Tran Dinh Phien, A1 - Shlykov, Sergey A. A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich T1 - 1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational preferences in gas and solution by GED, NMR and theoretical calculations JF - Tetrahedron N2 - 1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature C-13 and Si-29 NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeSaxPheq conformer in gas phase (1-Ph-eq :1-Ph-ax = 55:45, Delta G degrees = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph-eq:1-Ph-ax = 65:35, Delta G degrees = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory. (C) 2019 Elsevier Ltd. All rights reserved. KW - 1-Methylthio-1-phenyl-1-silacyclohexane KW - Conformational analysis KW - Gas phase electron diffraction KW - Low-temperature C-13 and Si-29 NMR KW - DFT and MP2 calculations Y1 - 2019 U6 - https://doi.org/10.1016/j.tet.2019.130677 SN - 0040-4020 VL - 75 IS - 46 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Otte, Fabian A1 - Schmidt, Bernd T1 - Matsuda-Heck Arylation of Glycals for the Stereoselective Synthesis of Aryl C-Glycosides JF - The journal of organic chemistry N2 - The methoxymethyl-protected glycal L-amicetal, synthesized de novo from L-ethyl lactate through tandem ring-closing metathesis-isomerization sequence, undergoes a highly trans-diastereoselective Heck-type coupling reaction with various arene diazonium salts to furnish 2,3-unsaturated aryl C-glycosides in moderate to excellent yields. The products can be further functionalized, e.g., by hydrogenation, epoxidation, or dihydroxylation to furnish 2,3,6-tridesoxy, 2,3-anhydro-6-desoxy, or 6-desoxy aryl C-glycosides, respectively. The method was applied to the synthesis of an a-configured 6-desoxy-gliflozin derivative. Y1 - 2019 U6 - https://doi.org/10.1021/acs.joc.9b02410 SN - 0022-3263 SN - 1520-6904 VL - 84 IS - 22 SP - 14816 EP - 14829 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Aloni, Sapir Shekef A1 - Perovic, Milena A1 - Weitman, Michal A1 - Cohen, Reut A1 - Oschatz, Martin A1 - Mastai, Yitzhak T1 - Amino acid-based ionic liquids as precursors for the synthesis of chiral nanoporous carbons JF - Nanoscale Advances N2 - The synthesis of chiral nanoporous carbons based on chiral ionic liquids (CILs) of amino acids as precursors is described. Such unique precursors for the carbonization of CILs yield chiral carbonaceous materials with high surface area (approximate to 620 m(2) g(-1)). The enantioselectivities of the porous carbons are examined by advanced techniques such as selective adsorption of enantiomers using cyclic voltammetry, isothermal titration calorimetry, and mass spectrometry. These techniques demonstrate the chiral nature and high enantioselectivity of the chiral carbon materials. Overall, we believe that the novel approach presented here can contribute significantly to the development of new chiral carbon materials that will find important applications in chiral chemistry, such as in chiral catalysis and separation and in chiral sensors. From a scientific point of view, the approach and results reported here can significantly deepen our understanding of chirality at the nanoscale and of the structure and nature of chiral nonporous materials and surfaces. Y1 - 2019 U6 - https://doi.org/10.1039/c9na00520j SN - 2516-0230 VL - 1 IS - 12 SP - 4981 EP - 4988 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zehbe, Kerstin A1 - Lange, Alyna A1 - Taubert, Andreas T1 - Stereolithography Provides Access to 3D Printed lonogels with High Ionic Conductivity JF - Energy Fuels N2 - New ionogels (IGs) were prepared by combination of a series of sulfonate-based ionic liquids (ILs), 1-methyl-3-(4-sulfobutyl)imidazolium para-toluenesulfonate [BmimSO(3)][pTS], 1-methyl-1-butylpiperidiniumsulfonate para-toluenesul-fonate [BmpipSO(3)] [pTS], and 1-methyl-3-(4-sulfobutyl) imidazolium methylsulfonate [BmimSO(3)H][MeSO3] with a commercial stereolithography photoreactive resin. The article describes both the fundamental properties of the ILs and the resulting IGs. The IGs obtained from the ILs and the resin show high ionic conductivity of up to ca. 0.7.10(-4) S/cm at room temperature and 3.4-10(-3) S/cm at 90 degrees C. Moreover, the IGs are thermally stable to about 200 degrees C and mechanically robust. Finally, and most importantly, the article demonstrates that the IGs can be molded three-dimensionally using stereolithography. This provides, for the first time, access to IGs with complex 3D shapes with potential application in battery or fuel cell technology. Y1 - 2019 U6 - https://doi.org/10.1021/acs.energyfuels.9b03379 SN - 0887-0624 SN - 1520-5029 VL - 33 IS - 12 SP - 12885 EP - 12893 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Taubert, Andreas A1 - Leroux, Fabrice A1 - Rabu, Pierre A1 - de Zea Bermudez, Veronica T1 - Advanced hybrid nanomaterials JF - Beilstein journal of nanotechnology KW - colloidal chemistry KW - environmental remediation KW - hybrid nanomaterials KW - nanocomposite KW - nanofillers KW - nanomedicine KW - nanostructures KW - polymer fillers KW - pore templating KW - smart materials Y1 - 2019 U6 - https://doi.org/10.3762/bjnano.10.247 SN - 2190-4286 VL - 10 SP - 2563 EP - 2567 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt am Main ER - TY - THES A1 - Melani, Giacomo T1 - From structural fluctuations to vibrational spectroscopy of adsorbates on surfaces T1 - Von Strukturfluktuationen bis zur Schwingungsspektroskopie von Adsorbaten auf Oberflächen BT - a theoretical study of H2O on α-Al2O3(0001) BT - eine theoretische Untersuchung von H2O auf α-Al2O3 (0001) N2 - Aluminum oxide is an Earth-abundant geological material, and its interaction with water is of crucial importance for geochemical and environmental processes. Some aluminum oxide surfaces are also known to be useful in heterogeneous catalysis, while the surface chemistry of aqueous oxide interfaces determines the corrosion, growth and dissolution of such materials. In this doctoral work, we looked mainly at the (0001) surface of α-Al 2 O 3 and its reactivity towards water. In particular, a great focus of this work is dedicated to simulate and address the vibrational spectra of water adsorbed on the α-alumina(0001) surface in various conditions and at different coverages. In fact, the main source of comparison and inspiration for this work comes from the collaboration with the “Interfacial Molecular Spectroscopy” group led by Dr. R. Kramer Campen at the Fritz-Haber Institute of the MPG in Berlin. The expertise of our project partners in surface-sensitive Vibrational Sum Frequency (VSF) generation spectroscopy was crucial to develop and adapt specific simulation schemes used in this work. Methodologically, the main approach employed in this thesis is Ab Initio Molecular Dynamics (AIMD) based on periodic Density Functional Theory (DFT) using the PBE functional with D2 dispersion correction. The analysis of vibrational frequencies from both a static and a dynamic, finite-temperature perspective offers the ability to investigate the water / aluminum oxide interface in close connection to experiment. The first project presented in this work considers the characterization of dissociatively adsorbed deuterated water on the Al-terminated (0001) surface. This particular structure is known from both experiment and theory to be the thermodynamically most stable surface termination of α-alumina in Ultra-High Vacuum (UHV) conditions. Based on experiments performed by our colleagues at FHI, different adsorption sites and products have been proposed and identified for D 2 O. While previous theoretical investigations only looked at vibrational frequencies of dissociated OD groups by staticNormal Modes Analysis (NMA), we rather employed a more sophisticated approach to directly assess vibrational spectra (like IR and VSF) at finite temperature from AIMD. In this work, we have employed a recent implementation which makes use of velocity-velocity autocorrelation functions to simulate such spectral responses of O-H(D) bonds. This approach allows for an efficient and qualitatively accurate estimation of Vibrational Densities of States (VDOS) as well as IR and VSF spectra, which are then tested against experimental spectra from our collaborators. In order to extend previous work on unimolecularly dissociated water on α-Al 2 O 3 , we then considered a different system, namely, a fully hydroxylated (0001) surface, which results from the reconstruction of the UHV-stable Al-terminated surface at high water contents. This model is then further extended by considering a hydroxylated surface with additional water molecules, forming a two-dimensional layer which serves as a potential template to simulate an aqueous interface in environmental conditions. Again, employing finite-temperature AIMD trajectories at the PBE+D2 level, we investigated the behaviour of both hydroxylated surface (HS) and the water-covered structure derived from it (known as HS+2ML). A full range of spectra, from VDOS to IR and VSF, is then calculated using the same methodology, as described above. This is the main focus of the second project, reported in Chapter 5. In this case, comparison between theoretical spectra and experimental data is definitely good. In particular, we underline the nature of high-frequency resonances observed above 3700 cm −1 in VSF experiments to be associated with surface OH-groups, known as “aluminols” which are a key fingerprint of the fully hydroxylated surface. In the third and last project, which is presented in Chapter 6, the extension of VSF spectroscopy experiments to the time-resolved regime offered us the opportunity to investigate vibrational energy relaxation at the α-alumina / water interface. Specifically, using again DFT-based AIMD simulations, we simulated vibrational lifetimes for surface aluminols as experimentally detected via pump-probe VSF. We considered the water-covered HS model as a potential candidate to address this problem. The vibrational (IR) excitation and subsequent relaxation is performed by means of a non-equilibrium molecular dynamics scheme. In such a scheme, we specifically looked at the O-H stretching mode of surface aluminols. Afterwards, the analysis of non-equilibrium trajectories allows for an estimation of relaxation times in the order of 2-4 ps which are in overall agreement with measured ones. The aim of this work has been to provide, within a consistent theoretical framework, a better understanding of vibrational spectroscopy and dynamics for water on the α-alumina(0001) surface,ranging from very low water coverage (similar to the UHV case) up to medium-high coverages, resembling the hydroxylated oxide in environmental moist conditions. N2 - Das Hauptziel dieser Doktorarbeit war die Untersuchung der Wechselwirkung zwischen Aluminiumoxid (α-Al2O3) und Wasser, wobei die (0001)-Oberfläche von α-Al2O3 im Fokus der Betrachtungen stand. Infolge der Entwicklung moderner oberflächensensitiver spektroskopischer Methoden, insbesondere in der Schwingungsspektroskopie, ist es inzwischen experimentell möglich, die Oberflächenchemie dieser Oxidmaterialien zu untersuchen und atomistische Informationen über ihre wässrigen Grenzflächen zu erhalten. Unsere Gruppe hat mit der Interfacial Molecular Spectroscopy Gruppe des Fritz-Haber-Instituts der MPG in Berlin zusammengearbeitet, deren Expertise in der oberflächensensitiven Vibrational Sum Frequency (VSF) Generation liegt. Diese Technik gestattet den spezifischen Nachweis von Adsorbatvibrationen, beispielsweise des Produkts der Wasserdissoziation und -adsorption. Zur theoretischen Untersuchung dieses Systems wurden verschiedene Berechnungsmethoden genutzt, wobei bevorzugt die Ab-initio-Molekulardynamik (AIMD) zum Einsatz kam. Darüber hinaus konzentrierten wir uns auf die Simulation von Schwingungsfrequenzen und -spektren für verschiedene Systeme unter Verwendung eines neuen, effizienten Algorithmus, der auf Grundlage klassischer Zeitkorrelationsfunktionen entwickelt wurde. Das erste Projekt untersuchte die einfachsten Adsorptionsprodukte von Wasserreaktionen auf der Al-terminierten α-Al2O3(0001)-Oberfläche, die unter Ultrahochvakuumbedingungen (UHV) als stabilste Struktur bekannt ist. Mit AIMD-basierten Methoden haben wir verschiedene Spezies simuliert, die aus unimolekular adsorbiertem Wasser stammen, und ihre Schwingungsfrequenzen im Vergleich zum Experiment bestimmt. In einem zweiten Projekt widmeten wir uns einer Situation, in der eine vollständig hydroxylierte α-Aluminiumoxid-Oberfläche mit einer ebenfalls vollständig hydroxylierten, aber um eine zusätzliche Wasserschicht erweiterten α-Aluminiumoxid-Oberfläche wechselwirkt. Diese beiden Strukturen dienen als Grundlage zur weitergehenden Untersuchung von Aluminiumoxid-Oberflächen mit größeren Wasser-Bedeckungsgraden unter Umgebungsbedingungen. Wiederum simulierten wir vollständige Schwingunsspektren (einschließlich IR und VSF). Hierzu wurden etablierte Methoden genutzt, die auf der Verwendung von Zeitkorrelationsfunktionen basieren, jedoch von uns im Rahmen dieser Doktorarbeit weiterentwickelt wurden. Schließlich haben wir in einem dritten Projekt in Zusammenarbeit mit Experimentatoren die Schwingungsrelaxation an der Wasser / α-Al2O3-Grenzfläche beschrieben. Motiviert durch Pump-Probe-VSF-Experimente zur Bestimmung der Schwingungslebensdauer adsorbierter OH-Spezies entwickelten und verwendeten wir einen AIMD-Ansatz zur Simulation der Anregungs- und Relaxationsprozesse. Auf Grundlage von Nichtgleichgewichtstrajektorien konnten wir auch eine Relaxationszeitskala für OH-Gruppen ermitteln, die zwischen 2 und 4 Pikosekunden beträgt und gut mit experimentellen Werten übereinstimmt. KW - theoretical chemistry KW - molecular dynamics KW - DFT KW - vibrational spectroscopy KW - theoretische Chemie KW - Molekulardynamik KW - DFT KW - Schwingungsspektroskopie Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-441826 ER - TY - JOUR A1 - Günther, Erika A1 - Klauß, André A1 - Toro-Nahuelpan, Mauricio A1 - Schüler, Dirk A1 - Hille, Carsten A1 - Faivre, Damien T1 - The in vivo mechanics of the magnetotactic backbone as revealed by correlative FLIM-FRET and STED microscopy JF - Scientific reports N2 - Protein interaction and protein imaging strongly benefit from the advancements in time-resolved and superresolution fluorescence microscopic techniques. However, the techniques were typically applied separately and ex vivo because of technical challenges and the absence of suitable fluorescent protein pairs. Here, we show correlative in vivo fluorescence lifetime imaging microscopy Forster resonance energy transfer (FLIM-FRET) and stimulated emission depletion (STED) microscopy to unravel protein mechanics and structure in living cells. We use magnetotactic bacteria as a model system where two proteins, MamJ and MamK, are used to assemble magnetic particles called magnetosomes. The filament polymerizes out of MamK and the magnetosomes are connected via the linker MamJ. Our system reveals that bacterial filamentous structures are more fragile than the connection of biomineralized particles to this filament. More importantly, we anticipate the technique to find wide applicability for the study and quantification of biological processes in living cells and at high resolution. Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-55804-5 SN - 2045-2322 VL - 9 PB - Nature Publ. Group CY - London ER - TY - THES A1 - Vranic, Marija T1 - 3D Structure of the biomarker hepcidin-25 in its native state T1 - 3D-Struktur des Biomarkers Hepcidin-25 im eigenen nativen Zustand N2 - Hepcidin-25 (Hep-25) plays a crucial role in the control of iron homeostasis. Since the dysfunction of the hepcidin pathway leads to multiple diseases as a result of iron imbalance, hepcidin represents a potential target for the diagnosis and treatment of disorders of iron metabolism. Despite intense research in the last decade targeted at developing a selective immunoassay for iron disorder diagnosis and treatment and better understanding the ferroportin-hepcidin interaction, questions remain. The key to resolving these underlying questions is acquiring exact knowledge of the 3D structure of native Hep-25. Since it was determined that the N-terminus, which is responsible for the bioactivity of Hep-25, contains a small Cu(II)-binding site known as the ATCUN motif, it was assumed that the Hep-25-Cu(II) complex is the native, bioactive form of the hepcidin. This structure has thus far not been elucidated in detail. Owing to the lack of structural information on metal-bound Hep-25, little is known about its possible biological role in iron metabolism. Therefore, this work is focused on structurally characterizing the metal-bound Hep-25 by NMR spectroscopy and molecular dynamics simulations. For the present work, a protocol was developed to prepare and purify properly folded Hep-25 in high quantities. In order to overcome the low solubility of Hep-25 at neutral pH, we introduced the C-terminal DEDEDE solubility tag. The metal binding was investigated through a series of NMR spectroscopic experiments to identify the most affected amino acids that mediate metal coordination. Based on the obtained NMR data, a structural calculation was performed in order to generate a model structure of the Hep-25-Ni(II) complex. The DEDEDE tag was excluded from the structural calculation due to a lack of NMR restraints. The dynamic nature and fast exchange of some of the amide protons with solvent reduced the overall number of NMR restraints needed for a high-quality structure. The NMR data revealed that the 20 Cterminal Hep-25 amino acids experienced no significant conformational changes, compared to published results, as a result of a pH change from pH 3 to pH 7 and metal binding. A 3D model of the Hep-25-Ni(II) complex was constructed from NMR data recorded for the hexapeptideNi(II) complex and Hep-25-DEDEDE-Ni(II) complex in combination with the fixed conformation of 19 C-terminal amino acids. The NMR data of the Hep-25-DEDEDE-Ni(II) complex indicates that the ATCUN motif moves independently from the rest of the structure. The 3D model structure of the metal-bound Hep-25 allows for future works to elucidate hepcidin’s interaction with its receptor ferroportin and should serve as a starting point for the development of antibodies with improved selectivity. N2 - Hepcidin-25 (Hep-25) spielt eine entscheidende Rolle bei der Kontrolle der Eisenhomöostase. Da die Dysfunktion des Hepcidin-Signalweges aufgrund des Eisenungleichgewichts zu mehreren Krankheiten führt, stellt Hepcidin ein potenzielles Ziel für die Diagnose und Behandlung von Störungen des Eisenstoffwechsels dar. Trotz intensiver Forschung in den letzten zehn Jahren, die darauf abzielte, einen selektiven Immunoassay für die Diagnose und Behandlung von Eisenerkrankungen zu entwickeln und die Ferroportin-Hepcidin-Interaktion besser zu verstehen, bleiben Fragen offen. Der Schlüssel zur Lösung dieser grundlegenden Fragen liegt darin, genaue Kenntnisse über die 3D-Struktur des nativen Hep-25 zu erlangen. Da festgestellt wurde, dass der N-Terminus, der für die Bioaktivität von Hep-25 verantwortlich ist, eine kleine Cu(II)-Bindungsstelle enthält, die als ATCUN-Motiv bekannt ist, wurde angenommen, dass der Hep-25- Cu(II)-Komplex die native, bioaktive Form des Hepcidins ist. Diese Struktur ist bisher noch nicht im Detail untersucht worden. Aufgrund fehlender Strukturinformationen über metallgebundenes Hep-25 ist wenig über seine mögliche biologische Rolle im Eisenstoffwechsel bekannt. Daher konzentriert sich diese Arbeit auf die strukturelle Charakterisierung des metallgebundenen Hep-25 mittels NMR-Spektroskopie und Molekulardynamik Simulationen. In der vorliegenden Arbeit wurde ein Protokoll zur Präparation und Reinigung von korrekt gefaltetem Hep-25 in hohen Mengen entwickelt. Um das Problem der geringen Löslichkeit von Hep-25 bei neutralem pH-Wert zu überwinden, haben wir einen C-terminalen DEDEDEDE Löslichkeits-Tag eingeführt. Die Metallbindung wurde durch eine Reihe von NMRspektroskopischen Experimenten untersucht, um die Aminosäuren zu identifizieren, welche an der Metallkoordination beteiligt sind. Basierend auf den erhaltenen NMR-Daten wurde eine Strukturberechnung durchgeführt, um eine Modellstruktur des Hep-25-Ni(II)-Komplexes zu erzeugen. Der DEDEDE-Tag wurde aufgrund fehlender NMR- restraints von der Strukturberechnung ausgeschlossen. Die dynamische Natur und der schnelle Austausch eines Teils der Amid-Protonen mit dem Lösungsmittel reduzierten die Gesamtzahl der NMR- restraints, die für eine hochwertige Struktur erforderlich waren. Die NMR-Daten zeigten, dass die 20 C-terminalen Hep-25-Aminosäuren keine signifikanten Konformationsänderungen als Folge eines pH-Wechsels von pH 3 auf pH 7 und einer Metallbindung erfuhren. Ein 3D-Modell des Hep-25-Ni(II)-Komplexes wurde aus den NMR-Daten des Hexapeptid-Ni(II)-Komplexes und des Hep-25-DEDEDE-Ni(II)-Komplexes in Kombination mit der bekannten Konformation der 19 C-terminalen Aminosäuren erstellt. Die NMR-Daten des Hep-25-DEDEDE-Ni(II)Komplexes zeigen, dass sich das Ni-ATCUN-Motiv unabhängig vom C-Terminus bewegt. Die 3D-Modellstruktur des metallgebundenen Hep-25 ermöglicht es, in Zukunft die Interaktion von Hepcidin mit seinem Rezeptor Ferroportin zu untersuchen und soll als Ausgangspunkt für die Entwicklung von Antikörpern mit verbesserter Selektivität dienen. KW - iron KW - hepcidin KW - peptide KW - metal KW - binding KW - NMR KW - Eisen KW - Hepcidin KW - Peptid KW - Metall KW - Bindung KW - NMR Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-459295 ER - TY - JOUR A1 - Scholz, Robert A1 - Lindner, Steven A1 - Loncaric, Ivor A1 - Tremblay, Jean Christophe A1 - Juaristi, J. A1 - Alducin, Maite A1 - Saalfrank, Peter T1 - Vibrational response and motion of carbon monoxide on Cu(100) driven by femtosecond laser pulses: Molecular dynamics with electronic friction JF - Physical review : B, Condensed matter and materials physics N2 - Carbon monoxide on copper surfaces continues to be a fascinating, rich microlab for many questions evolving in surface science. Recently, hot-electron mediated, femtosecond-laser pulse induced dynamics of CO molecules on Cu(100) were the focus of experiments [Inoue et al., Phys. Rev. Lett. 117, 186101 (2016)] and theory [Novko et al., Phys. Rev. Lett. 122, 016806 (2019)], unraveling details of the vibrational nonequilibrium dynamics on ultrashort (subpicoseconds) timescales. In the present work, full-dimensional time-resolved hot-electron driven dynamics are studied by molecular dynamics with electronic friction (MDEF). Dissipation is included by a friction term in a Langevin equation which describes the coupling of molecular degrees of freedom to electron-hole pairs in the copper surface, calculated from gradient-corrected density functional theory (DFT) via a local density friction approximation (LDFA). Relaxation due to surface phonons is included by a generalized Langevin oscillator model. The hot-electron induced excitation is described via a time-dependent electronic temperature, the latter derived from an improved two-temperature model. Our parameter-free simulations on a precomputed potential energy surface allow for excellent statistics, and the observed trends are confirmed by on-the-fly ab initio molecular dynamics with electronic friction (AIMDEF) calculations. By computing time-resolved frequency maps for selected molecular vibrations, instantaneous frequencies, probability distributions, and correlation functions, we gain microscopic insight into hot-electron driven dynamics and we can relate the time evolution of vibrational internal CO stretch-mode frequencies to measured data, notably an observed redshift. Quantitatively, the latter is found to be larger in MDEF than in experiment and possible reasons are discussed for this observation. In our model, in addition we observe the excitation and time evolution of large-amplitude low-frequency modes, lateral CO surface diffusion, and molecular desorption. Effects of surface atom motion and of the laser fluence are also discussed. Y1 - 2019 U6 - https://doi.org/10.1103/PhysRevB.100.245431 SN - 2469-9950 SN - 2469-9969 VL - 100 IS - 24 PB - American Physical Society CY - College Park ER - TY - GEN A1 - Erler, Alexander A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Gebbers, Robin T1 - Soil Nutrient Detection for Precision Agriculture Using Handheld Laser-Induced Breakdown Spectroscopy (LIBS) and Multivariate Regression Methods (PLSR, Lasso and GPR) T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Precision agriculture (PA) strongly relies on spatially differentiated sensor information. Handheld instruments based on laser-induced breakdown spectroscopy (LIBS) are a promising sensor technique for the in-field determination of various soil parameters. In this work, the potential of handheld LIBS for the determination of the total mass fractions of the major nutrients Ca, K, Mg, N, P and the trace nutrients Mn, Fe was evaluated. Additionally, other soil parameters, such as humus content, soil pH value and plant available P content, were determined. Since the quantification of nutrients by LIBS depends strongly on the soil matrix, various multivariate regression methods were used for calibration and prediction. These include partial least squares regression (PLSR), least absolute shrinkage and selection operator regression (Lasso), and Gaussian process regression (GPR). The best prediction results were obtained for Ca, K, Mg and Fe. The coefficients of determination obtained for other nutrients were smaller. This is due to much lower concentrations in the case of Mn, while the low number of lines and very weak intensities are the reason for the deviation of N and P. Soil parameters that are not directly related to one element, such as pH, could also be predicted. Lasso and GPR yielded slightly better results than PLSR. Additionally, several methods of data pretreatment were investigated. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 815 KW - LIBS KW - lasso KW - PLS regression KW - gaussian processes KW - soil KW - precision agriculture KW - nutrients Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-444183 SN - 1866-8372 IS - 815 ER - TY - THES A1 - Qin, Qing T1 - Chemical functionalization of porous carbon-based materials to enable novel modes for efficient electrochemical N2 fixation T1 - Chemische Funktionalisierung von porösen Materialien auf Kohlenstoffbasis zur Ermöglichung neuartiger Verfahren für eine effiziente elektrochemische N2-Fixierung N2 - The central motivation of the thesis was to provide possible solutions and concepts to improve the performance (e.g. activity and selectivity) of electrochemical N2 reduction reaction (NRR). Given that porous carbon-based materials usually exhibit a broad range of structural properties, they could be promising NRR catalysts. Therefore, the advanced design of novel porous carbon-based materials and the investigation of their application in electrocatalytic NRR including the particular reaction mechanisms are the most crucial points to be addressed. In this regard, three main topics were investigated. All of them are related to the functionalization of porous carbon for electrochemical NRR or other electrocatalytic reactions. In chapter 3, a novel C-TixOy/C nanocomposite has been described that has been obtained via simple pyrolysis of MIL-125(Ti). A novel mode for N2 activation is achieved by doping carbon atoms from nearby porous carbon into the anion lattice of TixOy. By comparing the NRR performance of M-Ts and by carrying out DFT calculations, it is found that the existence of (O-)Ti-C bonds in C-doped TixOy can largely improve the ability to activate and reduce N2 as compared to unoccupied OVs in TiO2. The strategy of rationally doping heteroatoms into the anion lattice of transition metal oxides to create active centers may open many new opportunities beyond the use of noble metal-based catalysts also for other reactions that require the activation of small molecules as well. In chapter 4, a novel catalyst construction composed of Au single atoms decorated on the surface of NDPCs was reported. The introduction of Au single atoms leads to active reaction sites, which are stabilized by the N species present in NDPCs. Thus, the interaction within as-prepared AuSAs-NDPCs catalysts enabled promising performance for electrochemical NRR. For the reaction mechanism, Au single sites and N or C species can act as Frustrated Lewis pairs (FLPs) to enhance the electron donation and back-donation process to activate N2 molecules. This work provides new opportunities for catalyst design in order to achieve efficient N2 fixation at ambient conditions by utilizing recycled electric energy. The last topic described in chapter 5 mainly focused on the synthesis of dual heteroatom-doped porous carbon from simple precursors. The introduction of N and B heteroatoms leads to the construction of N-B motives and Frustrated Lewis pairs in a microporous architecture which is also rich in point defects. This can improve the strength of adsorption of different reactants (N2 and HMF) and thus their activation. As a result, BNC-2 exhibits a desirable electrochemical NRR and HMF oxidation performance. Gas adsorption experiments have been used as a simple tool to elucidate the relationship between the structure and catalytic activity. This work provides novel and deep insights into the rational design and the origin of activity in metal-free electrocatalysts and enables a physically viable discussion of the active motives, as well as the search for their further applications. Throughout this thesis, the ubiquitous problems of low selectivity and activity of electrochemical NRR are tackled by designing porous carbon-based catalysts with high efficiency and exploring their catalytic mechanisms. The structure-performance relationships and mechanisms of activation of the relatively inert N2 molecules are revealed by either experimental results or DFT calculations. These fundamental understandings pave way for a future optimal design and targeted promotion of NRR catalysts with porous carbon-based structure, as well as study of new N2 activation modes. N2 - Die zentrale Motivation der Arbeit war es, mögliche Lösungen und Konzepte zur Verbesserung der Leistung (z.B. Aktivität und Selektivität) der elektrochemischen N2-Reduktionsreaktion (NRR) anzubieten. Da poröse Materialien auf Kohlenstoffbasis in der Regel ein breites Spektrum an strukturellen Eigenschaften aufweisen, könnten sie vielversprechende NRR-Katalysatoren sein. Daher sind das fortgeschrittene Design neuartiger poröser Materialien auf Kohlenstoffbasis und die Untersuchung ihrer Anwendung in der elektrokatalytischen NRR einschließlich der besonderen Reaktionsmechanismen die wichtigsten Punkte, die angegangen werden müssen. In diesem Zusammenhang wurden drei Hauptthemen untersucht. Alle von ihnen stehen im Zusammenhang mit der Funktionalisierung von porösem Kohlenstoff für elektrochemische NRR oder andere elektrokatalytische Reaktionen. In Kapitel 3 wurde ein neuartiger C-TixOy/C-Nanokomposit beschrieben, der durch einfache Pyrolyse von MIL-125(Ti) gewonnen wurde. Ein neuartiger Modus für die N2-Aktivierung wird durch Dotierung von Kohlenstoffatomen aus nahegelegenem porösem Kohlenstoff in das Aniongitter von TixOy erreicht. Durch den Vergleich der NRR-Leistung von M-Ts und die Durchführung von DFT-Berechnungen wird festgestellt, dass die Existenz von (O-)Ti-C-Bindungen in C-dotiertem TixOy die Fähigkeit zur Aktivierung und Reduktion von N2 im Vergleich zu unbesetzten OVs in TiO2 erheblich verbessern kann. Die Strategie, Heteroatome rational in das Aniongitter von Übergangsmetalloxiden zu dotieren, um aktive Zentren zu schaffen, kann viele neue Möglichkeiten eröffnen, die über den Einsatz von edelmetallbasierten Katalysatoren hinausgehen, auch für andere Reaktionen, die ebenfalls die Aktivierung von kleinen Molekülen erfordern. In Kapitel 4 wurde über eine neuartige Katalysatorkonstruktion aus Au-Einzelatomen berichtet, die auf der Oberfläche von NDPCs dekoriert sind. Die Einführung von Au-Einzelatomen führt zu aktiven Reaktionsstellen, die durch die in NDPCs vorhandenen N-Spezies stabilisiert werden. So ermöglichte die Interaktion innerhalb von hergestellten AuSAs-NDPCs-Katalysatoren eine vielversprechende Leistung für die elektrochemische NRR. Für den Reaktionsmechanismus können Au-Einzelstandorte und N- oder C-Spezies als frustrierte Lewis-Paare (FLPs) fungieren, um den Elektronenabgabe- und Rückgabeprozess zur Aktivierung von N2-Molekülen zu verbessern. Diese Arbeit bietet neue Möglichkeiten für das Design von Katalysatoren, um eine effiziente N2-Fixierung unter Umgebungsbedingungen durch die Nutzung recycelter elektrischer Energie zu erreichen. Das letzte in Kapitel 5 beschriebene Thema konzentrierte sich hauptsächlich auf die Synthese von dualem heteroatomdotiertem porösem Kohlenstoff aus einfachen Vorläufern. Die Einführung von N- und B-Heteroatomen führt zur Konstruktion von N-B-Motiven und frustrierten Lewis-Paaren in einer mikroporösen Architektur, die ebenfalls reich an Punktdefekten ist. Dies kann die Adsorptionskraft verschiedener Reaktanden (N2 und HMF) und damit deren Aktivierung verbessern. Infolgedessen weist BNC-2 eine wünschenswerte elektrochemische NRR- und HMF-Oxidationsleistung auf. Gasadsorptionsexperimente wurden als einfaches Werkzeug zur Aufklärung des Zusammenhangs zwischen Struktur und katalytischer Aktivität eingesetzt. Diese Arbeit liefert neue und tiefe Einblicke in das rationale Design und den Ursprung der Aktivität bei metallfreien Elektrokatalysatoren und ermöglicht eine physikalisch tragfähige Diskussion der aktiven Motive, sowie die Suche nach deren weiteren Anwendungen. Während dieser Arbeit, die allgegenwärtigen Probleme der niedrigen Selektivität und Aktivität der elektrochemischen NRR werden durch die Gestaltung poröser Katalysatoren auf Kohlenstoffbasis mit hoher Effizienz und die Erforschung ihrer katalytischen Mechanismen. Die Struktur-Leistungsbeziehungen und Aktivierungsmechanismen der relativ inerten N2-Moleküle werden entweder durch experimentelle Ergebnisse oder DFT-Berechnungen aufgezeigt. Diese grundlegenden Erkenntnisse ebnen den Weg für ein zukünftiges optimales Design und eine gezielte Förderung von NRR-Katalysatoren mit poröser Kohlenstoffstruktur, sowie für die Untersuchung neuer N2-Aktivierungsmodi. KW - N2 fixation KW - porous carbon-based materials KW - ammonia KW - selectivity KW - N2-Fixierung KW - porösen Materialien auf Kohlenstoffbasis KW - Ammoniak KW - Selektivität Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-443397 ER - TY - JOUR A1 - Burek, Katja A1 - Dengler, Joachim A1 - Emmerling, Franziska A1 - Feldmann, Ines A1 - Kumke, Michael Uwe A1 - Stroh, Julia T1 - Lanthanide Luminescence Revealing the Phase Composition in Hydrating Cementitious Systems JF - ChemistryOpen N2 - The hydration process of Portland cement in a cementitious system is crucial for development of the high‐quality cement‐based construction material. Complementary experiments of X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM) and time‐resolved laser fluorescence spectroscopy (TRLFS) using europium (Eu(III)) as an optical probe are used to analyse the hydration process of two cement systems in the absence and presence of different organic admixtures. We show that different analysed admixtures and the used sulphate carriers in each cement system have a significant influence on the hydration process, namely on the time‐dependence in the formation of different hydrate phases of cement. Moreover, the effect of a particular admixture is related to the type of sulphate carrier used. The quantitative information on the amounts of the crystalline cement paste components is accessible via XRD analysis. Distinctly different morphologies of ettringite and calcium−silicate−hydrates (C−S−H) determined by SEM allow visual conclusions about formation of these phases at particular ageing times. The TRLFS data provides information about the admixture influence on the course of the silicate reaction. The dip in the dependence of the luminescence decay times on the hydration time indicates the change in the structure of C−S−H in the early hydration period. Complementary information from XRD, SEM and TRLFS provides detailed information on distinct periods of the cement hydration process. KW - cement admixtures KW - cement hydration KW - Europium KW - luminescence KW - SEM KW - X-ray diffraction Y1 - 2019 U6 - https://doi.org/10.1002/open.201900249 SN - 2191-1363 VL - 8 IS - 12 SP - 1441 EP - 1452 PB - Wiley-VCH-Verl. CY - Weinheim ER - TY - GEN A1 - Burek, Katja A1 - Dengler, Joachim A1 - Emmerling, Franziska A1 - Feldmann, Ines A1 - Kumke, Michael Uwe A1 - Stroh, Julia T1 - Lanthanide Luminescence Revealing the Phase Composition in Hydrating Cementitious Systems T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The hydration process of Portland cement in a cementitious system is crucial for development of the high‐quality cement‐based construction material. Complementary experiments of X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM) and time‐resolved laser fluorescence spectroscopy (TRLFS) using europium (Eu(III)) as an optical probe are used to analyse the hydration process of two cement systems in the absence and presence of different organic admixtures. We show that different analysed admixtures and the used sulphate carriers in each cement system have a significant influence on the hydration process, namely on the time‐dependence in the formation of different hydrate phases of cement. Moreover, the effect of a particular admixture is related to the type of sulphate carrier used. The quantitative information on the amounts of the crystalline cement paste components is accessible via XRD analysis. Distinctly different morphologies of ettringite and calcium−silicate−hydrates (C−S−H) determined by SEM allow visual conclusions about formation of these phases at particular ageing times. The TRLFS data provides information about the admixture influence on the course of the silicate reaction. The dip in the dependence of the luminescence decay times on the hydration time indicates the change in the structure of C−S−H in the early hydration period. Complementary information from XRD, SEM and TRLFS provides detailed information on distinct periods of the cement hydration process. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 808 KW - cement admixtures KW - cement hydration KW - Europium KW - luminescence KW - SEM KW - X-ray diffraction Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-442433 SN - 1866-8372 IS - 808 ER - TY - THES A1 - Wang, Xuepu T1 - Polydimethylsiloxane wrinkles for surface patterns and assembly of metallic nanoparticles Y1 - 2019 ER - TY - THES A1 - Debsharma, Tapas T1 - Cellulose derived polymers T1 - Polymere aus Cellulose BT - synthesis of functional and degradable polymers from cellulose N2 - Plastics, such as polyethylene, polypropylene, and polyethylene terephthalate are part of our everyday lives in the form of packaging, household goods, electrical insulation, etc. These polymers are non-degradable and create many environmental problems and public health concerns. Additionally, these polymers are produced from finite fossils resources. With the continuous utilization of these limited resources, it is important to look towards renewable sources along with biodegradation of the produced polymers, ideally. Although many bio-based polymers are known, such as polylactic acid, polybutylene succinate adipate or polybutylene succinate, none have yet shown the promise of replacing conventional polymers like polyethylene, polypropylene and polyethylene terephthalate. Cellulose is one of the most abundant renewable resources produced in nature. It can be transformed into various small molecules, such as sugars, furans, and levoglucosenone. The aim of this research is to use the cellulose derived molecules for the synthesis of polymers. Acid-treated cellulose was subjected to thermal pyrolysis to obtain levoglucosenone, which was reduced to levoglucosenol. Levoglucosenol was polymerized, for the first time, by ring-opening metathesis polymerization (ROMP) yielding high molar mass polymers of up to ~150 kg/mol. The poly(levoglucosenol) is thermally stable up to ~220 ℃, amorphous, and is exhibiting a relatively high glass transition temperature of ~100 ℃. The poly(levoglucosenol) can be converted to a transparent film, resembling common plastic, and was found to degrade in a moist acidic environment. This means that poly(levoglucosenol) may find its use as an alternative to conventional plastic, for instance, polystyrene. Levoglucosenol was also converted into levoglucosenyl methyl ether, which was polymerized by cationic ring-opening metathesis polymerization (CROP). Polymers were obtained with molar masses up to ~36 kg/mol. These polymers are thermally stable up to ~220 ℃ and are semi-crystalline thermoplastics, having a glass transition temperature of ~35 ℃ and melting transition of 70-100 ℃. Additionally, the polymers underwent cross-linking, hydrogenation and thiol-ene click chemistry. N2 - Kunststoffe wie Polyethylen, Polypropylen und Polyethylenterephthalat sind ein großer Bestandteil unseres Alltags und finden Verwendung unter anderem als Verpackungsmaterialien, Haushaltswaren und Elektroisolierungen. Diese Polymere werden aus fossilen Ressourcen hergestellt, sind nicht abbaubar und verursachen nicht nur viele Umweltprobleme sondern können auch zu Gesundheitsschäden führen. Aufgrund dessen muss die Verwendung von erneuerbaren Ressourcen geachtet werden, wobei die hergestellten Polymere im Idealfall komplett biologisch abbaubar sind. Obwohl viele biobasierte Polymere, wie Polymilchsäure, Polybutylensuccinatadipat oder Polybutylensuccinat, bekannt sind, hat noch keines das Potential gezeigt, herkömmliche Polymere zu ersetzen. Cellulose ist einer der am häufigsten in der Natur produzierten nachwachsenden Rohstoffe und kann in verschiedene kleine organische Moleküle wie Zucker (Saccharide), Furan und auch Levoglucosenon umgewandelt werden. Ziel dieser Arbeit ist die Verwendung von Levoglucosenon als Monomer für die Synthese von Polymeren. Säurebehandelte Cellulose wurde einer thermischen Pyrolyse unterzogen, um Levoglucosenon zu erhalten, das dann weiter zu Levoglucosenol reduziert wurde. Das Levoglucosenol wurde zum ersten Mal erfolgreich über eine Ringöffnungsmetathese-Polymerisation (ROMP) polymerisiert. Die Molmassen der hergestellten Polymere erreichten Werte von bis zu ~150 kg/mol. Die thermische Analyse von Poly(levoglucosenol) zeigt, dass es bis zu einer Temperatur von ~220 ℃ stabil ist, eine Glasübergangstemperatur bei ~100 ℃ hat und ein amorphes Polymer ist. Weiterhin kann das Poly(levoglucosenol) in feuchter saurer Umgebung in kurzer Zeit abgebaut werden. Aufgrund dieser Eigenschaften kann Poly(levoglucosenol) als Alternative zu konventionellem Kunststoff, wie z.B. Polystyrol, eingesetzt werden kann. Levoglucosenol wurde weiter in Levoglucosenylmethylether umgewandelt. Levoglucosenylmethylether kann mit kationischer Ringöffnungs-Polymerisation (CROP) polymerisiert werden. Es wurden Polymere mit Molmassen von bis zu ~36 kg/mol hergestellt. Die Polymere weisen eine thermische Stabilität bis zu einer Temperatur von ~220 °C auf. Es handelt sich bei den hergestellten Poly(levoglucosenylmethylethern) um teilkristalline Thermoplaste, deren Glasüberganstemperatur bei ~35 °C und der Schmelzbereich bei 70-100 °C liegt. Die Doppelbindungen des Levoglucosenylmethylethers wurden genutzt um das Polymer zu vernetzen und zu funktionalisieren. KW - biomass valorization KW - levoglucosenol KW - ring-opening polymerization KW - degradable polymer KW - sustainable chemistry KW - Biomasseverwertung KW - Levoglucosenol KW - ringöffnende Polymerisation KW - abbaubares Polymer KW - nachhaltige Chemie Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-441312 ER - TY - THES A1 - Zhang, Shuhao T1 - Synthesis and self-assembly of protein-polymer conjugates for the preparation of biocatalytically active membranes T1 - Synthese und Selbstassemblierung von Protein/Polymer-Konjugaten für die Herstellung einer biokatalytisch aktiven Membran N2 - This thesis covers the synthesis of conjugates of 2-Deoxy-D-ribose-5-phosphate aldolase (DERA) with suitable polymers and the subsequent immobilization of these conjugates in thin films via two different approaches. 2-Deoxy-D-ribose-5-phosphate aldolase (DERA) is a biocatalyst that is capable of converting acetaldehyde and a second aldehyde as acceptor into enantiomerically pure mono- and diyhydroxyaldehydes, which are important structural motifs in a number of pharmaceutically active compounds. Conjugation and immobilization renders the enzyme applicable for utilization in a continuously run biocatalytic process which avoids the common problem of product inhibition. Within this thesis, conjugates of DERA and poly(N-isopropylacrylamide) (PNIPAm) for immobilization via a self-assembly approach were synthesized and isolated, as well as conjugates with poly(N,N-dimethylacrylamide) (PDMAA) for a simplified and scalable spray-coating approach. For the DERA/PNIPAm-conjugates different synthesis routes were tested, including grafting-from and grafting-to, both being common methods for the conjugation. Furthermore, both lysines and cysteines were addressed for the conjugation in order to find optimum conjugation conditions. It turned out that conjugation via lysine causes severe activity loss as one lysine plays a key role in the catalyzing mechanism. The conjugation via the cysteines by a grafting-to approach using pyridyl disulfide (PDS) end-group functionalized polymers led to high conjugation efficiencies in the presence of polymer solubilizing NaSCN. The resulting conjugates maintained enzymatic activity and also gained high acetaldehyde tolerance which is necessary for their use later on in an industrial relevant process after their immobilization. The resulting DERA/PNIPAm conjugates exhibited enhanced interfacial activity at the air/water interface compared to the single components, which is an important pre-requisite for the immobilization via the self-assembly approach. Conjugates with longer polymer chains formed homogeneous films on silicon wafers and glass slides while the ones with short chains could only form isolated aggregates. On top of that, long chain conjugates showed better activity maintenance upon the immobilization. The crosslinking of conjugates, as well as their fixation on the support materials, are important for the mechanical stability of the films obtained from the self-assembly process. Therefore, in a second step, we introduced the UV-crosslinkable monomer DMMIBA to the PNIPAm polymers to be used for conjugation. The introduction of DMMIBA reduced the lower critical solution temperature (LCST) of the polymer and thus the water solubility at ambient conditions, resulting in lower conjugation efficiencies and in turn slightly poorer acetaldehyde tolerance of the resulting conjugates. Unlike the DERA/PNIPAm, the conjugates from the copolymer P(NIPAM-co-DMMIBA) formed continuous, homogenous films only after the crosslinking step via UV-treatment. For a firm binding of the crosslinked films, a functionalization protocol for the model support material cyclic olefin copolymer (COC) and the final target support, PAN based membranes, was developed that introduces analogue UV-reactive groups to the support surface. The conjugates immobilized on the modified COC films maintained enzymatic activity and showed good mechanical stability after several cycles of activity assessment. Conjugates with longer polymer chains, however, showed a higher degree of crosslinking after the UV-treatment leading to a pronounced loss of activity. A porous PAN membrane onto which the conjugates were immobilized as well, was finally transferred to a dead end filtration membrane module to catalyze the aldol reaction of the industrially relevant mixture of acetaldehyde and hexanal in a continuous mode. Mono aldol product was detectable, but yields were comparably low and the operational stability needs to be further improved Another approach towards immobilization of DERA conjugates that was followed, was to generate the conjugates in situ by simply mixing enzyme and polymer and spray coat the mixture onto the membrane support. Compared to the previous approach, the focus was more put on simplicity and a possible scalability of the immobilization. Conjugates were thus only generated in-situ and not further isolated and characterized. For the conjugation, PDMAA equipped with N-2-thiolactone acrylamide (TlaAm) side chains was used, an amine-reactive comonomer that can react with the lysine residues of DERA, as well as with amino groups introduced to a desired support surface. Furthermore disulfide formation after hydrolysis of the Tla groups causes a crosslinking effect. The synthesized copolymer poly(N,N-Dimethylacrylamide-co-N-2-thiolactone acrylamide) (P(DMAA-co-TlaAm)) thus serves a multiple purpose including protein binding, crosslinking and binding to support materials. The mixture of DERA and polymer could be immobilized on the PAN support by spray-coating under partial maintenance of enzymatic activity. To improve the acetaldehyde tolerance, the polymer in used was further equipped with cysteine reactive PDS end-groups that had been used for the conjugation as described in the first part of the thesis. The generated conjugates indeed showed good acetaldehyde tolerance and were thus used to be coated onto PAN membrane supports. Post treatment with a basic aqueous solution of H2O2 was supposed to further crosslink the spray-coated film hydrolysis and oxidation of the thiolactone groups. However, a washing off of the material was observed. Optimization is thus still necessary. N2 - Die vorliegende Arbeit beschreibt die Synthese von Konjugaten aus 2-Deoxy-D-ribose-5-phosphat aldolase (DERA) und geeigneten Polymeren sowie deren nachfolgende Immobilisierung in dünnen Filmen mittels zwei verschiedener Herangehensweisen. DERA ist ein Biokatalysator, der in der Lage ist, Acetaldehyd mit einem weiteren Aldehyd zu enantiomerenreinen Mono- und Dihydroxyaldehyden zu verknüpfen. Diese Verbindungen sind wichtige Strukturmotive für eine Reihe von pharmazeutisch aktiven Verbindungen. Konjugation und Immobilisierung machen das Enzym nutzbar für den Einsatz in einem kontinuierlich betriebenen, biokatalytischen Prozess, welcher das bekannte Problem der Produktinhibierung umgeht. In der vorliegenden Arbeit wurden einerseits Konjugate aus DERA und Poly(N-isopropylacrylamid) (PNIPAm) für die Immobilisierung mittels eines Selbstassemblierungsverfahrens synthetisiert und isoliert, sowie andererseits entsprechende Konjugate mit Poly(N,N-dimethylacrylamid) (PDMAA) für ein vereinfachtes und skalierbares Immobilisierungsverfahren mittels Sprühauftrag hergestellt. Für die DERA/PNIPAm-Konjugate wurden verschiedene Syntheserouten getestet, einschließlich grafting-from und grafting-to. Beide Methoden werden standardmäßig für entsprechende Konjugationen eingesetzt. Weiterhin wurden sowohl die Lysine als auch die Cysteine des Enzyms für die Konjugation herangezogen, um optimale Konjugationsbedingungen zu finden. Konjugation über die Lysine verursachte deutliche Aktivitätsverluste, da ein Lysin auch die Schlüsselrolle im katalytischen Mechanismus des Enzyms spielt. Die Konjugation über die Cysteine sowie einen grafting-to-Ansatz unter Nutzung eines entsprechenden Polymers mit cysteinreaktiver Pyridyldisulfid-Endgruppe (PDS) führte zu einer hohen Konjugationseffizienz, sofern polymersolubilisierendes NaSCN eingesetzt wurde. Die resultierenden Konjugate behielten ihre enzymatische Aktivität bei deutlich gesteigerter Toleranz gegenüber Acetaldehyd. Beide Aspekte sind wichtig für den Einsatz des Enzyms in einem industriell relevanten Prozess nach dem Immobilisierungsschritt. Die DERA/PNIPAm-Konjugate zeigten eine erhöhte Oberflächenaktivität im Vergleich zu den Einzelkomponenten, was eine wichtige Voraussetzung für die Immobilisierung über eine Selbstassemblierung darstellt. Konjugate mit relativ langen Polymerketten bildeten nach dem Selbstassemblierungsschritt homogene Filme auf Silizium-Wafern und Glass-Objektträgern während Konjugate mit kurzen Ketten nur isolierte Aggregate bildeten. Darüber hinaus zeigten die Konjugate mit längeren Ketten einen besseren Erhalt der Enzymaktivität im Zuge der Immobilisierung. Die nachträgliche Vernetzung der Konjugate, sowie ihre feste Anbindung an die Trägermaterialien sind wichtige Voraussetzungen für die mechanische Stabilität des aus dem Selbstassemblierungsschritt erhaltenen Films. Aus diesem Grund wurde in einem zweiten Schritt das UV-vernetzbare Monomer DMMIBA in das für die Konjugation vorgesehene, PNIPAm-basierte Polymer eingeführt. Die Einbindung von DMMIBA setzte die untere kritische Lösungstemperatur (LCST) und damit die Löslichkeit des Polymers in Wasser bei Raumtemperatur herab. Dies führte zu niedrigeren Konjugationseffizienzen und damit zu einer etwas schlechteren Acetaldehydtoleranz der resultierenden Konjugate. Anders als im Fall von DERA/PNIPAm, bildeten die mit P(NIPAM-co-DMMIBA) synthetisierten Konjugate einen homogenen Film nur nach Vernetzung mittels UV-Behandlung aus. Für eine feste Anbindung des vernetzten Films wurde ein Funktionalisierungsprotokoll für das Modell-Trägermaterial aus cycloolefinischem Copolymer (COC) und das letztliche Zielmaterial, PAN-basierte Membranen, entwickelt, welches analoge UV-reaktive Gruppen auf der Trägeroberfläche erzeugt. Die auf COC immobilisierten Konjugate bewahrten ihre Enzymaktivität und zeigten eine gute mechanische Stabilität nach mehreren Aktivitäts-Messzyklen. Der Einsatz von Konjugaten mit längeren Polymerketten führte jedoch zu Filmen mit zu hohem Vernetzungsgrad was einen deutlichen Aktivitätsverlust bedingte. Eine poröse, PAN-basierte Membran, auf welcher die Konjugate ebenso immobilisiert wurden, wurde schlussendlich in ein Dead-End-Filtrationsmodul überführt, um die Aldolreaktion eines industriell relevanten Gemisches aus Acetaldehyd und Hexanal in einem kontinuierlich betriebenen Verfahren durchzuführen. Es konnte Monoaldolprodukt detektiert werden, jedoch waren die Ausbeuten vergleichsweise niedrig, während sich die operative Stabilität als verbesserungswürdig erwies. Ein weiterer Immobilisierungsansatz für DERA-Konjugate, beinhaltete die in-situ-Generierung der Konjugate durch einfaches Vermischen von Enzym und Polymer gefolgt von unmittelbaren Auftrag des Materials auf ein Membranträgermaterial mittels Sprühen. Im Vergleich zum ersten Ansatz lag der Fokus hier mehr auf der Einfachheit und prinzipiellen Skalierbarkeit der Immobilisierung. Daher wurden die Konjugate hier nur in-situ erzeugt und nicht weiter isoliert sowie charakterisiert. Für die Konjugation wurde PDMAA herangezogen, welches mit Thiolactongruppen entlang der Seitenkette ausgerüstet ist. Die Thiolactongruppen sind reaktiv gegenüber Aminen und können daher sowohl mit den Lysineinheiten der DERA reagieren als auch mit Aminogruppen, die im Vorfeld auf dem Trägermaterial erzeugt wurden. Darüber hinaus können durch Hydrolyse der Thiolactoneinheiten sowie anschließender Ausbildung von Disulfidbrücken Vernetzungspunkte erzeugt werden. Das hergestellte Copolymer poly(N,N-Dimethylacrylamide-co-N-2-thiolactone acrylamide) (P(DMAA-co-TlaAm) übernimmt daher mehrere Aufgaben einschließlich Proteinbindung, Vernetzung und Anbindung an das Trägermaterial. Mischungen aus DERA und Polymer konnten durch Sprühauftrag auf funktionalisierten PAN-Trägermaterialien unter teilweisem Erhalt der Enzymaktivität immobilisiert werden. Um auch hier die Acetaldehydtoleranz zu verbessern, wurde das Polymer in einem zweiten Schritt wieder mit PDS-Endgruppen ausgerüstet, die schon zuvor im ersten Teil der Arbeit für die Konjugatsynthese mittels grafting-to herangezogen wurden. Die hergestellten Konjugate zeigten eine gute Acetaldehydtoleranz und wurden daher verwendet, um PAN-Membranen zu beschichten. Eine Nachbehandlung mittels einer basischen Wasserstoffperoxidlösung sollte den aufgesprühten Film vernetzen. Im Ergebnis wurde jedoch ein großer Teil des aufgebrachten Materials im Zuge dieses Schritts heruntergewaschen. Eine weitere Optimierung dieses Schritts ist daher noch notwendig. KW - 2-deoxy-D-ribose-5-phoshphate aldolase KW - enzyme immobilization KW - enzymatically active membrane KW - enzyme/polymer conjugate KW - self-assembly Y1 - 2019 ER - TY - THES A1 - Schürings, Marco Philipp Hermann T1 - Synthesis of 1D microgel strands and their motion analysis in solution T1 - Synthese von 1D-Mikrogelsträngen und ihre Bewegungsanalyse in der Lösung N2 - The fabrication of 1D nanostrands composed of stimuli responsive microgels has been shown in this work. Microgels are well known materials able to respond to various stimuli from outer environment. Since these microgels respond via a volume change to an external stimulus, a targeted mechanical response can be achieved. Through carefully choosing the right composition of the polymer matrix, microgels can be designed to react precisely to the targeted stimuli (e.g. drug delivery via pH and temperature changes, or selective contractions through changes in electrical current125). In this work, it was aimed to create flexible nano-filaments which are capable of fast anisotropic contractions similar to muscle filaments. For the fabrication of such filaments or strands, nanostructured templates (PDMS wrinkles) were chosen due to a facile and low-cost fabrication and versatile tunability of their dimensions. Additionally, wrinkling is a well-known lithography-free method which enables the fabrication of nanostructures in a reproducible manner and with a high long-range periodicity. In Chapter 2.1, it was shown for the first time that microgels as soft matter particles can be aligned to densely packed microgel arrays of various lateral dimensions. The alignment of microgels with different compositions (e.g. VCL/AAEM, NIPAAm, NIPAAm/VCL and charged microgels) was shown by using different assembly techniques (e.g. spin-coating, template confined molding). It was chosen to set one experimental parameter constant which was the SiOx surface composition of the templates and substrates (e.g. oxidized PDMS wrinkles, Si-wafers and glass slides). It was shown that the fabrication of nanoarrays was feasible with all tested microgel types. Although the microgels exhibited different deformability when aligned on a flat surface, they retained their thermo-responsivity and swelling behavior. Towards the fabrication of 1D microgel strands interparticle connectivity was aspired. This was achieved via different cross-linking methods (i.e. cross-linking via UV-irradiation and host-guest complexation) discussed in Chapter 2.2. The microgel arrays created by different assembly methods and microgel types were tested for their cross-linking suitability. It was observed that NIPAAm based microgels cannot be cross-linked with UV light. Furthermore, it was found that these microgels exhibit a strong surface-particle-interaction and therefore could not be detached from the given substrates. In contrast to the latter, with VCL/AAEM based microgels it was possible to both UV cross-link them based on the keto-enol tautomerism of the AAEM copolymer, and to detach them from the substrate due to the lower adhesion energy towards SiOx surfaces. With VCL/AAEM microgels long, one-dimensional microgel strands could be re-dispersed in water for further analysis. It has also been shown that at least one lateral dimension of the free dispersed 1D microgel strands is easily controllable by adjusting the wavelength of the wrinkled template. For further work, only VCL/AAEM based microgels were used to focus on the main aim of this work, i.e. the fabrication of 1D microgel nanostrands. As an alternative to the unspecific and harsh UV cross-linking, the host-guest complexation via diazobenzene cross-linkers and cyclodextrin hosts was explored. The idea behind this approach was to give means to a future construction kit-like approach by incorporation of cyclodextrin comonomers in a broad variety of particle systems (e.g. microgels, nanoparticles). For this purpose, VCL/AAEM microgels were copolymerized with different amounts of mono-acrylate functionalized β-cyclodextrin (CD). After successfully testing the cross-linking capability in solution, the cross-linking of aligned VCL/AAEM/CD microgels was tried. Although the cross-linking worked well, once the single arrays came into contact to each other, they agglomerated. As a reason for this behavior residual amounts of mono-complexed diazobenzene linkers were suspected. Thus, end-capping strategies were tried out (e.g. excess amounts of β-cyclodextrin and coverage with azobenzene functionalized AuNPs) but were unsuccessful. With deeper thought, entropy effects were taken into consideration which favor the release of complexed diazobenzene linker leading to agglomerations. To circumvent this entropy driven effect, a multifunctional polymer with 50% azobenzene groups (Harada polymer) was used. First experiments with this polymer showed promising results regarding a less pronounced agglomeration (Figure 77). Thus, this approach could be pursued in the future. In this chapter it was found out that in contrast to pearl necklace and ribbon like formations, particle alignment in zigzag formation provided the best compromise in terms of stability in dispersion (see Figure 44a and Figure 51) while maintaining sufficient flexibility. For this reason, microgel strands in zigzag formation were used for the motion analysis described in Chapter 2.3. The aim was to observe the properties of unrestrained microgel strands in solution (e.g. diffusion behavior, rotational properties and ideally, anisotropic contraction after temperature increase). Initially, 1D microgel strands were manipulated via AFM in a liquid cell setup. It could be observed that the strands required a higher load force compared to single microgels to be detached from the surface. However, with the AFM it was not possible to detach the strands in a controllable manner but resulted in a complete removal of single microgel particles and a tearing off the strands from the surface, respectively. For this reason, to observe the motion behavior of unrestrained microgel strands in solution, confocal microscopy was used. Furthermore, to hinder an adsorption of the strands, it was found out that coating the surface of the substrates with a repulsive polymer film was beneficial. Confocal and wide-field microscopy videos showed that the microgel strands exhibit translational and rotational diffusive motion in solution without perceptible bending. Unfortunately, with these methods the detection of the anisotropic stimuli responsive contraction of the free moving microgel strands was not possible. To summarize, the flexibility of microgel strands is more comparable to the mechanical behavior of a semi flexible cable than to a yarn. The strands studied here consist of dozens or even hundreds of discrete submicron units strung together by cross-linking, having few parallels in nanotechnology. With the insights gained in this work on microgel-surface interactions, in the future, a targeted functionalization of the template and substrate surfaces can be conducted to actively prevent unwanted microgel adsorption for a given microgel system (e.g. PVCL and polystyrene coating235). This measure would make the discussed alignment methods more diverse. As shown herein, the assembly methods enable a versatile microgel alignment (e.g. microgel meshes, double and triple strands). To go further, one could use more complex templates (e.g. ceramic rhombs and star shaped wrinkles (Figure 14) to expand the possibilities of microgel alignment and to precisely control their aspect ratios (e.g. microgel rods with homogeneous size distributions). N2 - In dieser Arbeit wurde die Herstellung von Nanostrukturen aus stimuli-responsiven Mikrogelen gezeigt. Mikrogele sind bekannt dafür auf verschiedene Reize aus der Umgebung reagieren zu können, so werden sie z.B. in der Industrie seit langem als Superabsorber eingesetzt. Da diese Mikrogele über eine Volumenäderung auf den externen Reiz reagieren, kann so eine gezielte mechanische Antwort erreicht werden. Durch eine sorgfältige Auswahl der Polymermatrix ist es möglich die Mikrogele so zu gestalten, dass sie präzise auf die gesetzten Stimuli reagieren (z.B. Wirkstoffabgabe über pH- und Temperaturänderungen oder selektive Kontraktionen durch Zufuhr von elektrischem Strom). In dieser Arbeit wurde das Ziel verfolgt, flexible Nanofilamente zu schaffen, die ähnlich wie Muskelfilamente zu schnellen anisotropen Kontraktionen fähig sind. Für die Herstellung solcher Stränge wurden nanostrukturierte Template (PDMS-Wrinkles) verwendet, da diese einfach und kostengünstig herzustellen und in ihren Abmessungen vielseitig skalierbar sind. Darüber hinaus ist die Strukturbildung via Wrinkles ein bekanntes lithographiefreies Verfahren, das die Herstellung von Nanostrukturen in reproduzierbarer Weise und mit hoher Fernordnung auf Nanoskala ermöglicht. In Kapitel 2.1 wurde erstmals gezeigt, dass Mikrogele als weiche bzw. schwammartige Materialien zu dicht gepackten Mikrogelarrays mit einstellbaren lateralen Dimensionen ausgerichtet werden können. Obwohl die Mikrogele bei der Anordnung auf ebene Oberflächen unterschiedliche Verformbarkeiten zeigten, behielten sie ihre Thermoresponsivität und ihr Quellverhalten bei. Zur Herstellung von Mikrogelsträngen wurde eine interpartikuläre Konnektivität angestrebt. In Kapitel 2.2 wurde dies durch verschiedene Vernetzungsmethoden (d.h. Vernetzung durch UV-Bestrahlung und Wirt-Gast-Komplexierung) erreicht. Mit VCL/AAEM-Mikrogelen ist es möglich stabile, eindimensionale Mikrogelstränge herzustellen und zur weiteren Analyse in Wasser zu redispergieren. In diesem Kapitel wurde gezeigt, dass eindimensionale Partikelanordnungen in der Zickzackformation im Gegensatz zu Anordnungen in einer Perlenkettenstruktur oder zweidimensionaler Bandstruktur den besten Kompromiss in Bezug auf die Stabilität der Mikrogelstränge in Lösung bei gleichzeitigem Erhalt einer ausreichenden Flexibilität darstellt. In Kapitel 2.3 wurden für die Bewegungsanalysen Mikrogelstränge in Zickzackformation verwendet. Zusammenfassend lässt sich sagen, dass die Flexibilität der Mikrogelstränge eher mit der mechanischen Biegefähigkeit eines halbflexiblen Kabels als mit dem eines Fadens vergleichbar ist. Die hier untersuchten Stränge bestehen aus Dutzenden oder sogar Hunderten von diskreten Einzelpartikeln, die durch Vernetzung miteinander verbunden sind und für die es in der Nanotechnologie nur wenige Parallelen gibt. Wie hier dargestellt, ermöglichen die diversen Anordnungsmethoden eine vielseitige Mikrogelarchitektur (z.B. Mikrogelnetze, Doppel- und Dreifachstränge). In Zukunft könnte man komplexere Template (z.B. keramische Rhomben und sternförmige Wrinkles) verwenden, um die Möglichkeiten der nanoskaligen Mikrogelanordnungen zu erweitern und deren Seitenverhältnisse präzise zu steuern (z.B. zur Herstellung von homogenen Mikrogelstäbchen). KW - anisotropic microgels KW - microgel strands KW - microgel chains KW - template assisted alignment of soft particles KW - microgel array KW - Mikrogele KW - Mikrogelstränge KW - Mikrogelketten KW - tamplat unterstütze Anordnung von weichen Partikeln KW - Mikrogel-Array Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439532 ER - TY - GEN A1 - Riebe, Daniel A1 - Erler, Alexander A1 - Brinkmann, Pia A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Gebbers, Robin T1 - Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - The lack of soil data, which are relevant, reliable, affordable, immediately available, and sufficiently detailed, is still a significant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within fields, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, different calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural fields in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The first method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both fields. The second univariate model derived the calibration from the reference analytics of all samples from one field. The prediction is validated by LIBS data of the second field. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the first field are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the first field and independently on the second field data. The second univariate method yielded better calibration and prediction results compared to the first method, since matrix effects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 786 KW - laser-induced breakdown spectroscopy KW - LIBS KW - proximal soil sensing KW - soil nutrients KW - elemental composition Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-440079 SN - 1866-8372 IS - 786 ER - TY - JOUR A1 - Riebe, Daniel A1 - Erler, Alexander A1 - Brinkmann, Pia A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Gebbers, Robin T1 - Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture JF - Sensors N2 - The lack of soil data, which are relevant, reliable, affordable, immediately available, and sufficiently detailed, is still a significant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within fields, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, different calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural fields in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The first method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both fields. The second univariate model derived the calibration from the reference analytics of all samples from one field. The prediction is validated by LIBS data of the second field. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the first field are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the first field and independently on the second field data. The second univariate method yielded better calibration and prediction results compared to the first method, since matrix effects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method. KW - laser-induced breakdown spectroscopy KW - LIBS KW - proximal soil sensing KW - soil nutrients KW - elemental composition Y1 - 2019 U6 - https://doi.org/10.3390/s19235244 SN - 1424-8220 VL - 19 IS - 23 PB - MDPI CY - Basel ER - TY - GEN A1 - Büchele, Dominique A1 - Chao, Madlen A1 - Ostermann, Markus A1 - Leenen, Matthias A1 - Bald, Ilko T1 - Multivariate chemometrics as a key tool for prediction of K and Fe in a diverse German agricultural soil-set using EDXRF T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Within the framework of precision agriculture, the determination of various soil properties is moving into focus, especially the demand for sensors suitable for in-situ measurements. Energy-dispersive X-ray fluorescence (EDXRF) can be a powerful tool for this purpose. In this study a huge diverse soil set (n = 598) from 12 different study sites in Germany was analysed with EDXRF. First, a principal component analysis (PCA) was performed to identify possible similarities among the sample set. Clustering was observed within the four texture classes clay, loam, silt and sand, as clay samples contain high and sandy soils low iron mass fractions. Furthermore, the potential of uni- and multivariate data evaluation with partial least squares regression (PLSR) was assessed for accurate determination of nutrients in German agricultural samples using two calibration sample sets. Potassium and iron were chosen for testing the performance of both models. Prediction of these nutrients in 598 German soil samples with EDXRF was more accurate using PLSR which is confirmed by a better overall averaged deviation and PLSR should therefore be preferred. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 784 Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439988 SN - 1866-8372 IS - 784 ER - TY - JOUR A1 - Büchele, Dominique A1 - Chao, Madlen A1 - Ostermann, Markus A1 - Leenen, Matthias A1 - Bald, Ilko T1 - Multivariate chemometrics as a key tool for prediction of K and Fe in a diverse German agricultural soil-set using EDXRF JF - Scientific Reports N2 - Within the framework of precision agriculture, the determination of various soil properties is moving into focus, especially the demand for sensors suitable for in-situ measurements. Energy-dispersive X-ray fluorescence (EDXRF) can be a powerful tool for this purpose. In this study a huge diverse soil set (n = 598) from 12 different study sites in Germany was analysed with EDXRF. First, a principal component analysis (PCA) was performed to identify possible similarities among the sample set. Clustering was observed within the four texture classes clay, loam, silt and sand, as clay samples contain high and sandy soils low iron mass fractions. Furthermore, the potential of uni- and multivariate data evaluation with partial least squares regression (PLSR) was assessed for accurate determination of nutrients in German agricultural samples using two calibration sample sets. Potassium and iron were chosen for testing the performance of both models. Prediction of these nutrients in 598 German soil samples with EDXRF was more accurate using PLSR which is confirmed by a better overall averaged deviation and PLSR should therefore be preferred. Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-53426-5 SN - 2045-2322 VL - 9 PB - Macmillan Publishers Limited, part of Springer Nature CY - London ER - TY - GEN A1 - Liebig, Ferenc A1 - Henning, Ricky A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Schmitt, Clemens Nikolaus Zeno A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - A simple one-step procedure to synthesise gold nanostars in concentrated aqueous surfactant solutions T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Due to the enhanced electromagnetic field at the tips of metal nanoparticles, the spiked structure of gold nanostars (AuNSs) is promising for surface-enhanced Raman scattering (SERS). Therefore, the challenge is the synthesis of well designed particles with sharp tips. The influence of different surfactants, i.e., dioctyl sodium sulfosuccinate (AOT), sodium dodecyl sulfate (SDS), and benzylhexadecyldimethylammonium chloride (BDAC), as well as the combination of surfactant mixtures on the formation of nanostars in the presence of Ag⁺ ions and ascorbic acid was investigated. By varying the amount of BDAC in mixed micelles the core/spike-shell morphology of the resulting AuNSs can be tuned from small cores to large ones with sharp and large spikes. The concomitant red-shift in the absorption toward the NIR region without losing the SERS enhancement enables their use for biological applications and for time-resolved spectroscopic studies of chemical reactions, which require a permanent supply with a fresh and homogeneous solution. HRTEM micrographs and energy-dispersive X-ray (EDX) experiments allow us to verify the mechanism of nanostar formation according to the silver underpotential deposition on the spike surface in combination with micelle adsorption. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 769 KW - optical-properties KW - nanoparticles KW - sers KW - ultrafast KW - size KW - nanotriangles KW - nanoflowers KW - wavelength Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-438743 SN - 1866-8372 IS - 769 SP - 23633 EP - 23641 ER - TY - JOUR A1 - Liebig, Ferenc A1 - Henning, Ricky A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Schmitt, Clemens Nikolaus Zeno A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - A simple one-step procedure to synthesise gold nanostars in concentrated aqueous surfactant solutions JF - RSC Advances N2 - Due to the enhanced electromagnetic field at the tips of metal nanoparticles, the spiked structure of gold nanostars (AuNSs) is promising for surface-enhanced Raman scattering (SERS). Therefore, the challenge is the synthesis of well designed particles with sharp tips. The influence of different surfactants, i.e., dioctyl sodium sulfosuccinate (AOT), sodium dodecyl sulfate (SDS), and benzylhexadecyldimethylammonium chloride (BDAC), as well as the combination of surfactant mixtures on the formation of nanostars in the presence of Ag⁺ ions and ascorbic acid was investigated. By varying the amount of BDAC in mixed micelles the core/spike-shell morphology of the resulting AuNSs can be tuned from small cores to large ones with sharp and large spikes. The concomitant red-shift in the absorption toward the NIR region without losing the SERS enhancement enables their use for biological applications and for time-resolved spectroscopic studies of chemical reactions, which require a permanent supply with a fresh and homogeneous solution. HRTEM micrographs and energy-dispersive X-ray (EDX) experiments allow us to verify the mechanism of nanostar formation according to the silver underpotential deposition on the spike surface in combination with micelle adsorption. KW - optical-properties KW - nanoparticles KW - sers KW - ultrafast KW - size KW - nanotriangles KW - nanoflowers KW - wavelength Y1 - 2019 U6 - https://doi.org/10.1039/C9RA02384D SN - 2046-2069 VL - 9 SP - 23633 EP - 23641 PB - RSC Publishing CY - London ER - TY - THES A1 - Naderi Mehr, Fatemeh T1 - Preparation and self-assembly behavior of anisotropic polymer patchy particles Y1 - 2019 ER - TY - THES A1 - Noack, Sebastian T1 - Poly(lactide)-based amphiphilic block copolymers T1 - Polylactid-basierte amphiphile Blockcopolymere BT - self-assembly and stereocomplexation in aqueous media BT - Selbstorganisation und Stereokomplexierung in wässrigem Medium N2 - Due to its bioavailability and (bio)degradability, poly(lactide) (PLA) is an interesting polymer that is already being used as packaging material, surgical seam, and drug delivery system. Dependent on various parameters such as polymer composition, amphiphilicity, sample preparation, and the enantiomeric purity of lactide, PLA in an amphiphilic block copolymer can affect the self-assembly behavior dramatically. However, sizes and shapes of aggregates have a critical effect on the interactions between biological and drug delivery systems, where the general understanding of these polymers and their ability to influence self-assembly is of significant interest in science. The first part of this thesis describes the synthesis and study of a series of linear poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA)-based amphiphilic block copolymers with varying PLA (hydrophobic), and poly(ethylene glycol) (PEG) (hydrophilic) chain lengths and different block copolymer sequences (PEG-PLA and PLA-PEG). The PEG-PLA block copolymers were synthesized by ring-opening polymerization of lactide initiated by a PEG-OH macroinitiator. In contrast, the PLA-PEG block copolymers were produced by a Steglich-esterification of modified PLA with PEG-OH. The aqueous self-assembly at room temperature of the enantiomerically pure PLLA-based block copolymers and their stereocomplexed mixtures was investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). Spherical micelles and worm-like structures were produced, whereby the obtained self-assembled morphologies were affected by the lactide weight fraction in the block copolymer and self-assembly time. The formation of worm-like structures increases with decreasing PLA-chain length and arises from spherical micelles, which become colloidally unstable and undergo an epitaxial fusion with other micelles. As shown by DSC experiments, the crystallinity of the corresponding PLA blocks increases within the self-assembly time. However, the stereocomplexed self-assembled structures behave differently from the parent polymers and result in irregular-shaped clusters of spherical micelles. Additionally, time-dependent self-assembly experiments showed a transformation, from already self-assembled morphologies of different shapes to more compact micelles upon stereocomplexation. In the second part of this thesis, with the objective to influence the self-assembly of PLA-based block copolymers and its stereocomplexes, poly(methyl phosphonate) (PMeP) and poly(isopropyl phosphonate) (PiPrP) were produced by ring-opening polymerization to implement an alternative to the hydrophilic block PEG. Although, the 1,8 diazabicyclo[5.4.0]unde 7 ene (DBU) or 1,5,7 triazabicyclo[4.4.0]dec-5-ene (TBD) mediated synthesis of the corresponding poly(alkyl phosphonate)s was successful, however, not so the polymerization of copolymers with PLA-based precursors (PLA-homo polymers, and PEG-PLA block copolymers). Transesterification, obtained by 1H-NMR spectroscopy, between the poly(phosphonate)- and PLA block caused a high-field shifted peak split of the methine proton in the PLA polymer chain, with split intensities depending on the used catalyst (DBU for PMeP, and TBD for PiPrP polymerization). An additional prepared block copolymer PiPrP-PLLA that wasn’t affected in its polymer sequence was finally used for self-assembly experiments with PLA-PEG and PEG-PLA mixing. This work provides a comprehensive study of the self-assembly behavior of PLA-based block copolymers influenced by various parameters such as polymer block lengths, self-assembly time, and stereocomplexation of block copolymer mixtures. N2 - Aufgrund seiner Bioverfügbarkeit und (biologischen) Abbaubarkeit stellt Polylactid (PLA) ein interessantes Polymer dar, welches bereits in Verpackungsmaterialien, chirurgische Fäden und in selbst organisierten Wirkstofftransportsystemen eingesetzt wird. Als ein Teil von amphiphilen Blockcopolymeren kann PLA die molekulare Selbstorganisation in wässrigen Lösungen wesentlich beeinflussen. Die gebildeten Strukturen sind dabei essenziell von Faktoren wie der Blockcopolymer Zusammensetzung, Amphiphilie, Proben Vorbereitung und der Enantiomerenreinheit des Monomers abhängig. Die Kenntnis über die beschriebenen Faktoren und das allgemeine Verständnis für die dazugehörigen Polymere sowie die Möglichkeit ihre Selbstorganisation zu beeinflussen, ist von entscheidender Bedeutung in biomedizinischen Anwendungen. Unterschiedliche Größen oder Formen der selbst organisierten Wirkstoffträgern haben einen erheblichen Effekt auf die Wechselwirkung mit dem entsprechenden biologischen System und somit einen essenziellen Einfluss auf den Ausgang der medikamentösen Therapie. Der erste Teil dieser Doktorarbeit beschreibt die Synthese und Untersuchung einer Serie von Poly(L-Lactid) (PLLA) und Poly(D-Lactid) (PDLA)-basierten amphiphilen Blockcopolymeren mit variierenden PLA (hydrophob) und Polyethylenglycol (PEG) (hydrophil) Kettenlägen, sowie unterschiedlichen Polymersequenzen (PEG-PLA und PLA-PEG). Die genannten PEG-PLA Blockcopolymere wurden mittels organokatalysierter ringöffnender Polymerisation (ROP) hergestellt, wobei das entsprechende PEG-OH als Makroinitiator diente. Im Gegensatz dazu mussten die entsprechenden PLA-PEG Blockcopolymere mittels Steglich Veresterung von modifizierten PLA mit PEG-OH hergestellt werden. Die Selbstorganisation der PLLA-basierten Blockcopolymeren und deren stereokomplexierten Mischungen in wässriger Lösung erfolgte unter Raumtemperatur und wurde mittels Dynamischer Lichtstreuung (DLS), Transmissionselektronenmikroskopie (TEM), Röntgenstrukturanalyse und Dynamische Differenzkalorimetrie (DSC) untersucht. Dabei wurden kugel- und wurmförmige Strukturen beobachtet, wobei die gebildeten Strukturen vom Lactid Gewichtsanteil im Polymer, sowie der Selbstorganisationszeit abhängig waren. Mit andauernder Selbstorganisation und zunehmender Kristallinität wurden die zuerst gebildeten kugelförmigen Strukturen kolloidal unstabil und es erfolgte ein epitaktisches Wachstum zu wurmförmigen Strukturen in Abhängigkeit der Lactid Kettenlänge. Die stereokomplexierten Blockcopolymer Mischungen hingegen bildeten, unabhängig von der Copolymersequenz der entsprechenden Polymer Partner, hauptsächlich unregelmäßige Ansammlungen kugelförmiger Strukturen welche den Eindruck einer Perlenkette erweckten. Mit dem Einsetzen der Stereokomplexierung zeigten zeitlich aufgelöste Selbstorganisationsexperimente eine Transformation von bereits gebildeten Strukturen verschiedenster Formen und Größen (Polymer abhängig) zu kompakten Mizellen. Im zweiten Teil dieser Doktorarbeit wurden, mit dem Ziel die Selbstorganisation von PLA-basierten Blockcopolymeren und deren Stereokomplexmischung vermehrt zu beeinflussen, zwei alternative Polymere zu PEG untersucht. Ähnlich wie PLA, konnten mittels organokatalysierter ROP Polymethylphosphonat (PMeP) und Polyisopropylphosphonat (PiPrP) erfolgreich hergestellt werden. Die Blockcopolymer Synthese mit PLA-basierten Polymervorgängern erwies sich jedoch als schwierig. Aufgrund einer Protonenpeakspaltung der Methingruppe in der PLA-Wiederholeinheit konnten mittels 1H-NMR Spektroskopie Umersterungsprozesse zwischen dem Polyalkylphosphonat- und PLA block nachgewiesen werden, welche in Abhängigkeit des verwendeten Katalysators (DBU oder TBD) unterschiedlich stark ausfielen. Das ebenfalls hergestellte PiPrP-PLLA Blockcopolymer wies keine Unregelmäßigkeiten in der Polymersequenz auf und wurde anschließend für Selbstorganisationsexperimente mit PLA-PEG und PEG-PLA genutzt. Diese Arbeit liefert eine umfangreiche Studie zur Selbstorganisation PLA-basierter Blockcopolymere und untersucht verschiedenste Einflussparameter wie Blocklängen, Selbstorganisationszeit und Stereokomplexierung in Polymermischungen. KW - polylactide KW - polymer KW - self-assembly KW - stereocomplexation KW - block copolymer KW - Polylactid KW - Polymer KW - Selbstorganisation KW - Stereokomplexierung KW - Block Copolymer Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-436168 ER - TY - GEN A1 - Kirste, Matthias A1 - Brietzke, Thomas Martin A1 - Holdt, Hans-Jürgen A1 - Schilde, Uwe T1 - The crystal structure of 1,12-diazaperylene, C₁₈H₁₀N₂ T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - C₁₈H₁₀N₂, monoclinic, P2₁/c (no. 14), a=7.9297(9) Å, b=11.4021(14) Å, c=13.3572(15) Å, β=105.363(8)°, V =1164.5(2) ų, Z =4, Rgt(F)=0.0325, wRref(F²)=0.0774, T =210(2) K. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 752 Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-436501 SN - 1866-8372 IS - 752 ER - TY - JOUR A1 - Kirste, Matthias A1 - Brietzke, Thomas Martin A1 - Holdt, Hans-Jürgen A1 - Schilde, Uwe T1 - The crystal structure of 1,12-diazaperylene, C₁₈H₁₀N₂ JF - Zeitschrift für Kristallographie - New Crystal Structures N2 - C₁₈H₁₀N₂, monoclinic, P2₁/c (no. 14), a=7.9297(9) Å, b=11.4021(14) Å, c=13.3572(15) Å, β=105.363(8)°, V =1164.5(2) ų, Z =4, Rgt(F)=0.0325, wRref(F²)=0.0774, T =210(2) K. Y1 - 2019 U6 - https://doi.org/10.1515/NCRS-2019-0385 SN - 2196-7105 SN - 2194-4946 VL - 234 IS - 6 SP - 1255 EP - 1257 PB - De Gruyter CY - Berlin ER - TY - GEN A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Hess, Andreas A1 - Schlaad, Helmut A1 - Koetz, Joachim T1 - Temperature-triggered reversible breakdown of polymer-stabilized olive BT - silicone oil Janus emulsions T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol% oleoyl side chains. Completely engulfed emulsion droplets remained stable at room temperature and could be destabilized on demand upon heating to the transition temperature of the polymeric stabilizer. Time-dependent light micrographs demonstrate the temperature-induced breakdown of the Janus droplets, which opens new aspects of application, for instance in biocatalysis. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 751 KW - microgels KW - step Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-436461 SN - 1866-8372 IS - 751 SP - 19271 EP - 19277 ER - TY - JOUR A1 - Raju, Rajarshi Roy A1 - Liebig, Ferenc A1 - Hess, Andreas A1 - Schlaad, Helmut A1 - Koetz, Joachim T1 - Temperature-triggered reversible breakdown of polymer-stabilized olive BT - silicone oil Janus emulsions JF - RSC Advances N2 - A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol% oleoyl side chains. Completely engulfed emulsion droplets remained stable at room temperature and could be destabilized on demand upon heating to the transition temperature of the polymeric stabilizer. Time-dependent light micrographs demonstrate the temperature-induced breakdown of the Janus droplets, which opens new aspects of application, for instance in biocatalysis. KW - microgels KW - step Y1 - 2019 U6 - https://doi.org/10.1039/c9ra03463c SN - 2046-2069 VL - 9 IS - 35 SP - 19271 EP - 19277 PB - RSC Publishing CY - London ER - TY - THES A1 - Walczak, Ralf T1 - Molecular design of nitrogen-doped nanoporous noble carbon materials for gas adsorption T1 - Molekulares Design Stickstoffdotierter, Nanoporöser, und Edler Kohlenstoffmaterialien für Gasadsorption N2 - In den modernen Gesellschaften führt ein stetig steigender Energiebedarf zu dem zunehmenden Verbrauch fossiler Brennstoffe wie Kohle, Öl, und Gas. Die Verbrennung dieser kohlenstoffbasierten Brennstoffe führt unweigerlich zur Freisetzung von Treibhausgasen, vor allem von CO2. Die CO2 Aufnahme unmittelbar bei den Verbrennungsanlagen oder direkt aus der Luft, zusammen mit Regulierung von CO2 produzierenden Energiesektoren (z.B. Kühlanlagen), können den CO2 Ausstoß reduzieren. Allerdings führen insbesondere bei der CO2 Aufnahme die geringen CO2 Konzentrationen und die Aufnahme konkurrierender Gase zu niedrigen CO2 Kapazitäten und Selektivitäten. Das Zusammenspiel der Gastmoleküle mit porösen Materialien ist dabei essentiell. Poröse Kohlenstoffmaterialien besitzen attraktive Eigenschaften, unter anderem elektrische Leitfähigkeit, einstellbare Porosität, als auch chemische und thermische Stabilität. Allerdings führt die zu geringe Polarisierbarkeit dieser Materialien zu einer geringen Affinität zu polaren Molekülen (z.B. CO2, H2O, oder NH3). Diese Affinität kann durch den Einbau von Stickstoff erhöht werden. Solche Materialien sind oft „edler“ als reine Kohlenstoffe, dies bedeutet, dass sie eher oxidierend wirken, als selbst oxidiert zu werden. Die Problematik besteht darin, einen hohen und gleichmäßig verteilten Stickstoffgehalt in das Kohlenstoffgerüst einzubauen. Die Zielsetzung dieser Dissertation ist die Erforschung neuer Synthesewege für stickstoffdotierte edle Kohlenstoffmaterialien und die Entwicklung eines grundlegenden Verständnisses für deren Anwendung in Gasadsorption und elektrochemischer Energiespeicherung. Es wurde eine templatfreie Synthese für stickstoffreiche, edle, und mikroporöse Kohlenstoffmaterialien durch direkte Kondensation eines stickstoffreichen organischen Moleküls als Vorläufer erarbeitet. Dadurch konnten Materialien mit hohen Adsorptionskapazitäten für H2O und CO2 bei niedrigen Konzentrationen und moderate CO2/N2 Selektivitäten erzielt werden. Um die CO2/N2 Selektivitäten zu verbessern, wurden mittels der Einstellung des Kondensationsgrades die molekulare Struktur und Porosität der Kohlenstoffmaterialien kontrolliert. Diese Materialien besitzen die Eigenschaften eines molekularen Siebs für CO2 über N2, das zu herausragenden CO2/N2 Selektivitäten führt. Der ultrahydrophile Charakter der Porenoberflächen und die kleinen Mikroporen dieser Kohlenstoffmaterialien ermöglichen grundlegende Untersuchungen für die Wechselwirkungen mit Molekülen die polarer sind als CO2, nämlich H2O und NH3. Eine weitere Reihe stickstoffdotierter Kohlenstoffmaterialien wurde durch Kondensation eines konjugierten mikroporösen Polymers synthetisiert und deren strukturelle Besonderheiten als Anodenmaterial für die Natriumionen Batterie untersucht. Diese Dissertation leistet einen Beitrag zur Erforschung stickstoffdotierter Kohlenstoffmaterialien und deren Wechselwirkungen mit verschiedenen Gastmolekülen. N2 - The growing energy demand of the modern economies leads to the increased consumption of fossil fuels in form of coal, oil, and natural gases, as the mains sources. The combustion of these carbon-based fossil fuels is inevitably producing greenhouse gases, especially CO2. Approaches to tackle the CO2 problem are to capture it from the combustion sources or directly from air, as well as to avoid CO2 production in energy consuming sources (e.g., in the refrigeration sector). In the former, relatively low CO2 concentrations and competitive adsorption of other gases is often leading to low CO2 capacities and selectivities. In both approaches, the interaction of gas molecules with porous materials plays a key role. Porous carbon materials possess unique properties including electric conductivity, tunable porosity, as well as thermal and chemical stability. Nevertheless, pristine carbon materials offer weak polarity and thus low CO2 affinity. This can be overcome by nitrogen doping, which enhances the affinity of carbon materials towards acidic or polar guest molecules (e.g., CO2, H2O, or NH3). In contrast to heteroatom-free materials, such carbon materials are in most cases “noble”, that is, they oxidize other matter rather than being oxidized due to the very positive working potential of their electrons. The challenging task here is to achieve homogenous distribution of significant nitrogen content with similar bonding motives throughout the carbon framework and a uniform pore size/distribution to maximize host-guest interactions. The aim of this thesis is the development of novel synthesis pathways towards nitrogen-doped nanoporous noble carbon materials with precise design on a molecular level and understanding of their structure-related performance in energy and environmental applications, namely gas adsorption and electrochemical energy storage. A template-free synthesis approach towards nitrogen-doped noble microporous carbon materials with high pyrazinic nitrogen content and C2N-type stoichiometry was established via thermal condensation of a hexaazatriphenylene derivative. The materials exhibited high uptake of guest molecules, such as H2O and CO2 at low concentrations, as well as moderate CO2/N2 selectivities. In the following step, the CO2/N2 selectivity was enhanced towards molecular sieving of CO2 via kinetic size exclusion of N2. The precise control over the condensation degree, and thus, atomic construction and porosity of the resulting materials led to remarkable CO2/N2 selectivities, CO2 capacities, and heat of CO2 adsorption. The ultrahydrophilic nature of the pore walls and the narrow microporosity of these carbon materials served as ideal basis for the investigation of interface effects with more polar guest molecules than CO2, namely H2O and NH3. H2O vapor physisorption measurements, as well as NH3-temperature programmed desorption and thermal response measurements showed exceptionally high affinity towards H2O vapor and NH3 gas. Another series of nitrogen-doped carbon materials was synthesized by direct condensation of a pyrazine-fused conjugated microporous polymer and their structure-related performance in electrochemical energy storage, namely as anode materials for sodium-ion battery, was investigated. All in all, the findings in this thesis exemplify the value of molecularly designed nitrogen-doped carbon materials with remarkable heteroatom content implemented as well-defined structure motives. The simultaneous adjustment of the porosity renders these materials suitable candidates for fundamental studies about the interactions between nitrogen-doped carbon materials and different guest species. KW - carbon materials KW - nitrogen-doped KW - gas adsorption KW - porosity KW - Porösität KW - Gasadsorption KW - Stickstoffdotiert KW - Kohlenstoffmaterialien Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-435241 ER - TY - JOUR A1 - Krueger, Tobias A1 - Kelling, Alexandra A1 - Linker, Torsten A1 - Schilde, Uwe T1 - Crystal structures of three cyclohexane‑based γ‑spirolactams BT - determination of configurations and conformations JF - BMC Chemistry N2 - The title compounds, 2-azaspiro[4.5]deca-1-one, C₉H₁₅NO, (1a), cis-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1b), and trans-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1c), were synthesized from benzoic acids 2 in only 3 steps in high yields. Crystallization from n-hexane afforded single crystals, suitable for X-ray diffraction. Thus, the configurations, conformations, and interesting crystal packing effects have been determined unequivocally. The bicyclic skeleton consists of a lactam ring, attached by a spiro junction to a cyclohexane ring. The lactam ring adopts an envelope conformation and the cyclohexane ring has a chair conformation. The main difference between compound 1b and compound 1c is the position of the carbonyl group on the 2-pyrrolidine ring with respect to the methyl group on the 8-position of the cyclohexane ring, which is cis (1b) or trans (1c). A remarkable feature of all three compounds is the existence of a mirror plane within the molecule. Given that all compounds crystallize in centrosymmetric space groups, the packing always contains interesting enantiomer-like pairs. Finally, the structures are stabilized by intermolecular N–H···O hydrogen bonds. KW - 2-Azaspiro[4.5]deca-1-ones KW - Cis- and trans-form KW - Configuration KW - Conformation KW - Lactams Y1 - 2019 U6 - https://doi.org/10.1186/s13065-019-0586-7 SN - 2661-801X VL - 13 IS - 69 PB - Springer International Publishing CY - Basel ER - TY - GEN A1 - Krueger, Tobias A1 - Kelling, Alexandra A1 - Linker, Torsten A1 - Schilde, Uwe T1 - Crystal structures of three cyclohexane‑based γ‑spirolactams BT - determination of configurations and conformations T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - The title compounds, 2-azaspiro[4.5]deca-1-one, C₉H₁₅NO, (1a), cis-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1b), and trans-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1c), were synthesized from benzoic acids 2 in only 3 steps in high yields. Crystallization from n-hexane afforded single crystals, suitable for X-ray diffraction. Thus, the configurations, conformations, and interesting crystal packing effects have been determined unequivocally. The bicyclic skeleton consists of a lactam ring, attached by a spiro junction to a cyclohexane ring. The lactam ring adopts an envelope conformation and the cyclohexane ring has a chair conformation. The main difference between compound 1b and compound 1c is the position of the carbonyl group on the 2-pyrrolidine ring with respect to the methyl group on the 8-position of the cyclohexane ring, which is cis (1b) or trans (1c). A remarkable feature of all three compounds is the existence of a mirror plane within the molecule. Given that all compounds crystallize in centrosymmetric space groups, the packing always contains interesting enantiomer-like pairs. Finally, the structures are stabilized by intermolecular N–H···O hydrogen bonds. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 738 KW - 2-Azaspiro[4.5]deca-1-ones KW - Cis- and trans-form KW - Configuration KW - Conformation KW - Lactams Y1 - 1019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-434911 IS - 738 ER - TY - THES A1 - Tian, Zhihong T1 - Oxygen-, Sulfur-doped Novel Porous Carbon-Nitrogen Frameworks by Salt Melt Method Y1 - 2019 ER - TY - THES A1 - Lai, Feili T1 - Functionalized ordered mesoporous carbon materials for enhancing the energy density of supercapacitors Y1 - 2019 ER - TY - THES A1 - Sarhan, Radwan Mohamed T1 - Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy T1 - Plasmonen-getriebene photokatalytische Reaktionen, gemessen mittels oberflächenverstärkter Raman-Spektroskopie N2 - Plasmonic metal nanostructures can be tuned to efficiently interact with light, converting the photons into energetic charge carriers and heat. Therefore, the plasmonic nanoparticles such as gold and silver nanoparticles act as nano-reactors, where the molecules attached to their surfaces benefit from the enhanced electromagnetic field along with the generated energetic charge carriers and heat for possible chemical transformations. Hence, plasmonic chemistry presents metal nanoparticles as a unique playground for chemical reactions on the nanoscale remotely controlled by light. However, defining the elementary concepts behind these reactions represents the main challenge for understanding their mechanism in the context of the plasmonically assisted chemistry. Surface-enhanced Raman scattering (SERS) is a powerful technique employing the plasmon-enhanced electromagnetic field, which can be used for probing the vibrational modes of molecules adsorbed on plasmonic nanoparticles. In this cumulative dissertation, I use SERS to probe the dimerization reaction of 4-nitrothiophenol (4-NTP) as a model example of plasmonic chemistry. I first demonstrate that plasmonic nanostructures such as gold nanotriangles and nanoflowers have a high SERS efficiency, as evidenced by probing the vibrations of the rhodamine dye R6G and the 4-nitrothiophenol 4-NTP. The high signal enhancement enabled the measurements of SERS spectra with a short acquisition time, which allows monitoring the kinetics of chemical reactions in real time. To get insight into the reaction mechanism, several time-dependent SERS measurements of the 4-NTP have been performed under different laser and temperature conditions. Analysis of the results within a mechanistic framework has shown that the plasmonic heating significantly enhances the reaction rate, while the reaction is probably initiated by the energetic electrons. The reaction was shown to be intensity-dependent, where a certain light intensity is required to drive the reaction. Finally, first attempts to scale up the plasmonic catalysis have been performed showing the necessity to achieve the reaction threshold intensity. Meanwhile, the induced heat needs to quickly dissipate from the reaction substrate, since otherwise the reactants and the reaction platform melt. This study might open the way for further work seeking the possibilities to quickly dissipate the plasmonic heat generated during the reaction and therefore, scaling up the plasmonic catalysis. N2 - Plasmonische Metallnanostrukturen können so eingestellt werden, dass sie effizient mit Licht interagieren, Photonen in energetische Ladungsträger und wärmeenergie umwandeln. Aus diesem Grund wirken plasmonische Nanopartikel wie Gold und Silbernanopartikel als Nanoreaktoren, wenn Moleküle mit deren Oberfläche verbunden sind. Durch das verstärkte elektromagnetische Feld und den somit erzeugten energetischen Ladungsträgern und der wärmeenergie können chemische Umwandlungen entstehen. Das bedeutet, in der plasmonischen Chemie sind Metallnanopartikel ein einzigartiges system um chemische Reaktionen auf der Nanoebene unter der Kontrolle von Licht verfolgen zu können. Die Herausforderung liegt darin, grundlegende Konzepte hinter den Reaktionen für das mechanistische Verständnis in Bezug auf die plasmonisch unterstützte Chemie zu definieren. Oberflächenverstärkte Raman Streuung (SERS) ist eine leistungsfähige Technik, die sich mit plasmonverstärkten, elektromagnetischen Feldern beschäftigt, um die Vibrationsmoden von den auf den Nanopartikeln absorbierten Molekülen zu analysieren. In dieser kumulativen Dissertation wurde die Dimerisierung von 4-Nitrothiophenol (4-NTP) mittels SERS als Beispielreaktion für die plasmonische Chemie untersucht. Aufgrund der hohen SERS Signalverstärkung konnten die SERS Spektren mit einer kurzen Erfassungszeit aufgenommen werden, was die Untersuchung der Kinetik und des Reaktionsmechanismus in Echtzeit ermöglichte. KW - plasmonic chemistry KW - plasmonische Chemie KW - heiße Elektronen KW - SERS KW - SERS Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-433304 ER - TY - THES A1 - Ruiz Rodriguez, Janete Lorena T1 - Osmotic pressure effects on collagen mimetic peptides N2 - Collagen is the most abundant protein in mammals. In many tissues, collagen molecules assemble to form a hierarchical structure. In the smallest supramolecular unit, named fibril, each molecule is displaced in the axial direction with respect to its neighbors. This staggering creates a periodic gap and overlap regions, where the gap regions exhibit 20% less density. These fibril-forming collagens play an essential role in the strength of connective tissues. Despite much effort, directed at understanding collagen function and regulation, the influence of the chemical environment on the local structural and mechanical properties remains poorly understood. Recent studies, aimed at elucidating the effect of osmotic pressure, showed that collagen contracts upon water removal. This observation highlights the importance of water for the stabilization and mechanics of the collagen molecule. Using collagen mimetic peptides (CMPs), which fold into triple helical structures reminiscent of natural collagen, the primary goal of this work was to investigate the effect of the osmotic pressure on specific collagen-mimetic sequences. CMPs were used as the model system as they provide sequence control, which is essential for discriminating local from global structural changes and for relating the observed effects to existing knowledge about the full-length collagen molecule. Of specific interest was the structure of individual collagen triple helices as well as their organization into self-assembled higher order structures. These key structural features were monitored with infrared spectroscopy (IR) and synchrotron X-ray scattering, while varying the osmotic pressure. For controlling the osmotic pressure, CMP powder samples were incubated in air of defined relative humidity, ranging from dry conditions to highly “humid”. In addition, to obtain more biologically relevant conditions, the CMPs were measured in ultrapure water and in solutions containing small molecule osmolytes. Using the sequences (Pro-Pro-Gly)10, (Pro-Hyp-Gly)10 and (Hyp-Hyp-Gly)10, it was shown that CMPs with different degrees of proline hydroxylation (Hyp = hydroxyproline) exhibit a sequence-specific response to osmotic pressure. IR spectroscopy revealed that osmotic pressure changes affect the strength of the triple helix stabilizing, interchain hydrogen bond and that the extent of this change depends on the degree of hydroxylation. X-ray scattering experiments further showed that changes in osmotic pressure affect both the molecular length as well as the higher order organization of CMPs. Starting from a pseudo-hexagonal packing in the dry state, all three CMPs showed isotropic swelling when increasing the water content to approximately 1.2 water molecules per amino acid, again to different extents depending on the degree of hydroxylation. When increasing the water content further, this pseudo-hexagonal arrangement breaks down. In the fully hydrated state, each CMP is characterized by its own specific and more complex packing geometry. While these changes in the lateral packing arrangement suggest swelling upon hydration, an overall decrease of the molecular length (i.e. contraction) was observed in the axial direction. Also for this structural feature, a strong dependency on the specific amino acid sequence was found. Interestingly, the observed contraction is the opposite of what has been reported for natural collagen. As (Pro-Pro-Gly)n, (Pro-Hyp-Gly)n and (Hyp-Hyp-Gly)n repeat units are found in collagen with a relatively high abundance, this suggests that other collagen sequence fragments need to respond to hydration in the opposite way to obtain a net elongation of the full-length collagen molecule. To test this hypothesis, sequences predicted to be sensitive to osmotic pressure were considered. One such sequence, consisting of two repeat units (Ala-Arg-Gly-Ser-Asp-Gly), was inserted as a guest into a (Pro-Pro-Gly) host. When compared to the canonical CMP sequences investigated earlier, the lateral helix packing follows a similar trend with increasing hydration; however, the host-guest CMP axially elongates with increasing water content. This behavior is more similar to what has been found for natural collagen and suggests that different sequences do determine the molecular length of collagen sequences differently. Interestingly, the canonical sequences are more abundant in the overlap region while the guest sequence is found in the gap region. This allows to speculate that sequences in the gap and overlap regions possess a specifically fine-tuned local response to osmotic pressure changes. Clearly, more experiments with additional sequences are needed to confirm this. In conclusion, the results obtained in this work indicate a highly sequence specific interaction between collagen and water. Osmotic pressure-induced conformational changes mostly originate from local geometries and bonding patterns and affect both the structure of individual triple helices as well as higher order assemblies. One key remaining question is how these conformational changes affect the local mechanical properties of the collagen molecule. As a first step, the stiffness (persistence length) of full-length collagen was determined using atomic force microscopy. In the future, experimental strategies need to be developed that allow for investigating the mechanical properties of specific collagen sequences, e.g. performing single-molecule force spectroscopy of CMPs. Y1 - 2019 ER - TY - THES A1 - Yan, Runyu T1 - Nitrogen-doped and porous carbons towards new energy storage mechanisms for supercapacitors with high energy density T1 - Neuartige Energiespeichermechanismen in porösen und stickstoffdotierten Kohlenstoffen für die Anwendung in Superkondensatoren mit hoher Energiedichte N2 - Supercapacitors are electrochemical energy storage devices with rapid charge/discharge rate and long cycle life. Their biggest challenge is the inferior energy density compared to other electrochemical energy storage devices such as batteries. Being the most widely spread type of supercapacitors, electrochemical double-layer capacitors (EDLCs) store energy by electrosorption of electrolyte ions on the surface of charged electrodes. As a more recent development, Na-ion capacitors (NICs) are expected to be a more promising tactic to tackle the inferior energy density due to their higher-capacity electrodes and larger operating voltage. The charges are simultaneously stored by ion adsorption on the capacitive-type cathode surface and via faradic process in the battery-type anode, respectively. Porous carbon electrodes are of great importance in these devices, but the paramount problems are the facile synthetic routes for high-performance carbons and the lack of fundamental understanding of the energy storage mechanisms. Therefore, the aim of the present dissertation is to develop novel synthetic methods for (nitrogen-doped) porous carbon materials with superior performance, and to reveal a deeper understanding energy storage mechanisms of EDLCs and NICs. The first part introduces a novel synthetic method towards hierarchical ordered meso-microporous carbon electrode materials for EDLCs. The large amount of micropores and highly ordered mesopores endow abundant sites for charge storage and efficient electrolyte transport, respectively, giving rise to superior EDLC performance in different electrolytes. More importantly, the controversial energy storage mechanism of EDLCs employing ionic liquid (IL) electrolytes is investigated by employing a series of porous model carbons as electrodes. The results not only allow to conclude on the relations between the porosity and ion transport dynamics, but also deliver deeper insights into the energy storage mechanism of IL-based EDLCs which is different from the one usually dominating in solvent-based electrolytes leading to compression double-layers. The other part focuses on anodes of NICs, where novel synthesis of nitrogen-rich porous carbon electrodes and their sodium storage mechanism are investigated. Free-standing fibrous nitrogen-doped carbon materials are synthesized by electrospinning using the nitrogen-rich monomer (hexaazatriphenylene-hexacarbonitrile, C18N12) as the precursor followed by condensation at high temperature. These fibers provide superior capacity and desirable charge/discharge rate for sodium storage. This work also allows insights into the sodium storage mechanism in nitrogen-doped carbons. Based on this mechanism, further optimization is done by designing a composite material composed of nitrogen-rich carbon nanoparticles embedded in conductive carbon matrix for a better charge/discharge rate. The energy density of the assembled NICs significantly prevails that of common EDLCs while maintaining the high power density and long cycle life. N2 - Superkondensatoren sind elektrochemische Energiespeicher, die eine hohe Lade-/Entladerate und Zyklensta-bilität aufweisen, deren größte Einschränkung derzeit jedoch bei ihrer im Vergleich zu anderen Speicherlösungen, wie etwa Batterien, geringen Energiedichte liegt. Im am weitesten verbreiteten Superkondensatortyp, dem elektrochemischen Doppelschichtkondensator (engl. electrochemical double-layer capacitor, EDLC), wird die Energie durch Elektrosorption der Elektrolytionen an die geladene Elektrodenoberfläche gespeichert. Der Natrium-Ionen-Kondensator (engl. Na-ion capacitor, NIC) ist eine neuere Entwicklung und löst das Problem der geringen Energiedichte durch Verwendung von Elektroden mit einer höheren Kapazität und Betriebsspannung. Dies wird dadurch erreicht, dass simultan anodenseitig ein faradayscher Prozess und kathodenseitig der Aufbau einer elektrochemischen Doppelschicht genutzt werden. Somit kommen die Vorteile beider Phänomene zum Tragen. Poröse Kohlenstoffelektroden sind wichtig für beide Speichersysteme, wobei die Entwicklung einfacher Syn-theserouten für die Herstellung von Hochleistungskohlenstoffen und der Aufbau eines grundlegenden Ver-ständnisses der dem Energiespeicher zugrunde liegenden Mechanismen die vordergründigen Herausforde-rungen sind. Daher ist es das Ziel der vorliegenden Dissertation, neue Methoden zur Synthese (stickstoffdo-tierter) Kohlenstoffmaterialien mit überlegener Leistung zu erschließen und eine tiefere Einsicht in die me-chanistischen Aspekte der Funktionsweise der eingangs vorgestellten Superkondensatorsysteme zu erhalten. Im ersten Teil der Arbeit wird eine neuartige Synthese von Kohlenstoff-Elektrodenmaterialien für EDLCs vor-gestellt, welche ein hohes Volumen an Mikroporen und hochgeordneten Mesoporen aufweisen. Durch deren Einsatz kann in verschiedenen Elektrolytsystemen eine herausragende Energiedichte erzielt werden. Umso bedeutender sind die Ergebnisse der Untersuchung des kontrovers diskutierten Energiespeichermechanismus in EDLCs mit Elektrolyten auf Basis ionischer Flüssigkeiten (engl. ionic liquids, ILs) und Elektroden aus porösen Modellkohlenstoffen. Aus diesen können nicht nur Rückschlüsse auf den Zusammenhang zwischen Porosität und Ionentransportdynamik gezogen werden, sondern sie lassen auch wichtige Erkenntnisse auf die Mechanismen des Ladungsspeichers in IL-basierten EDLCs zu, welche sich grundlegend von dem in lösungsmittelbasierten Elektrolyten vorherrschenden Mechanismus, der Bildung einer Kompressionsdoppelschicht, unterscheiden. Im zweiten Teil des Werks liegt der Fokus auf der Synthese stickstoffreicher poröser Kohlenstoffelektroden als Anoden für NICs und der Untersuchung der Vorgänge während der Natriumeinlagerung in solchen Syste-men. Freistehende, faserartige und stickstoffdotierte Kohlenstoffmaterialien wurden durch Elektrospinnen des stickstoffreichen Monomers Hexaazatriphenylen-hexacarbonitril (C18N12) gefolgt von dessen Kondensati-on bei hoher Temperatur erhalten. Diese Fasern überzeugen durch überragende Kapazität und eine hohe Lade-/Entladerate beim Natriumspei-chervorgang. In diesem Rahmen wurde auch der Mechanismus der Natriumeinlagerung in stickstoffdotierten Kohlenstoffen beleuchtet und auf Basis dieser Erkenntnisse wurde eine weitere Optimierung vorgenommen. Indem ein Kompositmaterial aus stickstoffreichen Kohlenstoffnanopartikeln in einer leitfähigen Kohlenstoffmatrix erzeugt wurde, konnte die Lade-/Entladerate abermals verbessert werden. Somit übertrifft die Energiedichte der so konstruierten NICs die gewöhnlicher EDLCs, während deren hohe Leistungsdichte und Lebensdauer erhalten bleibt. KW - porous carbons KW - supercapacitors KW - high energy density KW - energy storage mechanism KW - poröse Kohlenstoffe KW - Superkondensatoren KW - hohe Energiedichte KW - Energiespeichermechanismus Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-431413 ER - TY - GEN A1 - Heck, Christian A1 - Kanehira, Yuya A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures T2 - Mathematisch-Naturwissenschaftliche Reihe N2 - Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 732 KW - amorphous carbon KW - DNA origami KW - SERS KW - nanoparticle dimers KW - nanolenses Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-430812 SN - 1866-8372 IS - 732 ER - TY - JOUR A1 - Heck, Christian A1 - Kanehira, Yuya A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures JF - Molecules N2 - Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates. KW - amorphous carbon KW - DNA origami KW - SERS KW - nanoparticle dimers KW - nanolenses Y1 - 2019 U6 - https://doi.org/10.3390/molecules24122324 SN - 1420-3049 VL - 24 IS - 12 PB - MDPI CY - Basel ER - TY - THES A1 - Jiang, Yi T1 - Tailoring surface functions of micro/nanostructured polymeric substrates by thermo-mechanical treatments Y1 - 2019 ER - TY - GEN A1 - Abbas, Ioana M. A1 - Vranic, Marija A1 - Hoffmann, Holger A1 - El-Khatib, Ahmed H. A1 - Montes-Bayón, María A1 - Möller, Heiko Michael A1 - Weller, Michael G. T1 - Investigations of the Copper Peptide Hepcidin-25 by LC-MS/MS and NMR⁺ T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 701 KW - hepcidin-25 KW - copper KW - nickel KW - copper complex KW - ATCUN motif KW - metal complex KW - MS KW - NMR structure KW - metal peptide KW - metalloprotein KW - metallopeptide KW - isomerization KW - racemization KW - purity KW - reference material Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427926 SN - 1866-8372 IS - 701 ER - TY - THES A1 - Al Nakeeb, Noah T1 - Self-assembly and crosslinking approaches of double hydrophilic linear-brush block copolymers BT - a biocompatible platform for the next generation of nanoreactors Y1 - 2019 ER -