TY - JOUR A1 - Schimka, Selina A1 - Klier, Dennis Tobias A1 - de Guerenu, Anna Lopez A1 - Bastian, Philipp A1 - Lomadze, Nino A1 - Kumke, Michael Uwe A1 - Santer, Svetlana T1 - Photo-isomerization of azobenzene containing surfactants induced by near-infrared light using upconversion nanoparticles as mediator JF - Journal of physics : Condensed matter N2 - Here we report on photo-isomerization of azobenzene containing surfactants induced during irradiation with near-infrared (NIR) light in the presence of upconversion nanoparticles (UCNPs) acting as mediator. The surfactant molecule consists of charged head group and hydrophobic tail with azobenzene group incorporated in alkyl chain. The azobenzene group can be reversible photo-isomerized between two states: trans- and cis- by irradiation with light of an appropriate wavelength. The trans-cis photo-isomerization is induced by UV light, while cis-trans isomerization proceeds either thermally in darkness, or can be accelerated by exposure to illumination with a longer wavelength typically in a blue/green range. We present the application of lanthanide doped UCNPs to successfully switch azobenzene containing surfactants from cis to trans conformation in bulk solution using NIR light. Using Tm-3(+) or Er-3(+) as activator ions, the UCNPs provide emissions in the spectral range of 450 nm < lambda(em) < 480 nm (for Tm-3(+), three and four photon induced emission) or 525 nm < lambda(em) < 545 nm (for Er-3(+), two photon induced emission), respectively. Especially for UCNPs containing Tm-3(+) a good overlap of the emissions with the absorption bands of the azobenzene is present. Under illumination of the surfactant solution with NIR light (lambda(ex) = 976 nm) in the presence of the Tm-3(+)-doped UCNPs, the relaxation time of cis-trans photo-isomerization was increased by almost 13 times compared to thermally induced isomerization. The influence of thermal heating due to the irradiation using NIR light was shown to be minor for solvents not absorbing in NIR spectral range (e.g. CHCl3) in contrast to water, which shows a distinct absorption in the NIR. KW - upconversion nanoparticles KW - azobenzene containing surfactants KW - kinetic of cis-trans isomerization Y1 - 2019 U6 - https://doi.org/10.1088/1361-648X/aafcfa SN - 0953-8984 SN - 1361-648X VL - 31 IS - 12 PB - IOP Publ. Ltd. CY - Bristol 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 - JOUR A1 - Schuck, Götz A1 - Lehmann, Frederike A1 - Ollivier, Jacques A1 - Mutka, Hannu A1 - Schorr, Susan T1 - Influence of chloride substitution on the rotational dynamics of methylammonium in MAPbI(3-x)Cl(x) perovskites JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Hybrid halide perovskites, MAPbI(3), MAPbI(2.94)Cl(0.0)6, and MAPbCl(3) (MA, methylammonium), were investigated using inelastic and quasielastic neutron scattering (QENS) with the aim of elucidating the impact of chloride substitution on the rotational dynamics of MA. In this context, we discuss the influence of the inelastic neutron scattering caused by low-energy phonons on QENS, resulting from the MA rotational dynamics in MAPbI(3-x)Cl(x). Through a comparative temperature-dependent QENS investigation with different energy resolutions, which allow a wide Fourier time window, we achieved a consistent description of the influence of chlorine substitution in MAPbI(3) on the MA dynamics. Our results showed that chlorine substitution in the low-temperature orthorhombic phase leads to a weakening of the hydrogen bridge bonds, since the characteristic relaxation times of C-3 rotation at 70 K in MAPbCl(3) (135 ps) and MAPbI(2.94)Cl(0.06) (485 ps) are much shorter than that in MAPbI(3) (1635 ps). For the orthorhombic phase, we obtained the activitin energies from the temperature-dependent characteristic relaxation times tau (c3). by Arrhenius fits, indicating lower values of E-a for MAPbCl(3) and MAPbI(2.94)Cl(0.06) compared to that of MAPbI(3). We also performed QENS analyses at 190 K for all three samples. Here, we observed that MAPbCI(3) shows slower MA rotational dynamics than MAPbI(3) in the disordered structure. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpcc.9b01238 SN - 1932-7447 VL - 123 IS - 18 SP - 11436 EP - 11446 PB - American Chemical Society CY - Washington 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 - Schönemann, Eric A1 - Koc, Julian A1 - Aldred, Nick A1 - Clare, Anthony S. A1 - Laschewsky, André A1 - Rosenhahn, Axel A1 - Wischerhoff, Erik T1 - Synthesis of Novel Sulfobetaine Polymers with Differing Dipole Orientations in Their Side Chains, and Their Effects on the Antifouling Properties JF - Macromolecular rapid communications N2 - The impact of the orientation of zwitterionic groups, with respect to the polymer backbone, on the antifouling performance of thin hydrogel films made of polyzwitterions is explored. In an extension of the recent discussion about differences in the behavior of polymeric phosphatidylcholines and choline phosphates, a quasi-isomeric set of three poly(sulfobetaine methacrylate)s is designed for this purpose. The design is based on the established monomer 3-[N-2-(methacryloyloxy)ethyl-N,N-dimethyl]ammonio-propane-1-sulfonate and two novel sulfobetaine methacrylates, in which the positions of the cationic and the ionic groups relative to the polymerizable group, and thus also to the polymer backbone, are altered. The effect of the varied segmental dipole orientation on their water solubility, wetting behavior by water, and fouling resistance is compared. As model systems, the adsorption of the model proteins bovine serum albumin (BSA), fibrinogen, and lysozyme onto films of the various polyzwitterion surfaces is studied, as well as the settlement of a diatom (Navicula perminuta) and barnacle cyprids (Balanus improvisus) as representatives of typical marine fouling communities. The results demonstrate the important role of the zwitterionic group's orientation on the polymer behavior and fouling resistance. KW - antifouling KW - coatings KW - crosslinking KW - hydrophilic polymers KW - polyzwitterions Y1 - 2019 U6 - https://doi.org/10.1002/marc.201900447 SN - 1022-1336 SN - 1521-3927 VL - 41 IS - 1 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kleinpeter, Erich A1 - Suslova, E. N. T1 - Conformational Analysis of (1,1′-Phenyl-1,1′-silacyclohex-1-yl)disiloxane BT - DFT and Low-Temperature 13C NMR Spectroscopy Study JF - Russian journal of general chemistry N2 - The DFT and MP2 theoretical conformational analysis of the recently synthesized (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane has revealed the energetic preference of the Ph-ax,Ph-ax conformer. The Ph-ax,Ph-ax: Ph-ax,Ph-eq: Ph-eq,Ph-eq conformers ratio has been estimated as of 46.6: 33.1: 20.3 from the M062X/6-311G(d,p) free energy simulation, suggesting the possibility of detecting individual conformers experimentally, e.g., by low-temperature H-1 and C-13 NMR spectroscopy. However, only the presence of several conformers has been detected by means of H-1 NMR spectroscopy at 113 K; determination of the (Hz) and G(#) (kcal/mol) parameters for the 6-membered ring interconversion has been impossible due to the signals broadening at low temperature, signal temperature shifts, and extremely low barrier of ring inversion at T-c < 113 K. KW - siloxanes KW - silacyclohexanes KW - conformational analysis KW - DFT and MP2 simulation KW - low-temperature NMR spectroscopy Y1 - 2019 U6 - https://doi.org/10.1134/S1070363219040121 SN - 1070-3632 SN - 1608-3350 VL - 89 IS - 4 SP - 713 EP - 716 PB - Pleiades Publ. CY - New York 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 - 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 - 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 -