TY - JOUR A1 - Mazurek-Budzyńska, Magdalena A1 - Behl, Marc A1 - Razzaq, Muhammad Yasar A1 - Nöchel, Ulrich A1 - Rokicki, Gabriel A1 - Lendlein, Andreas T1 - Hydrolytic stability of aliphatic poly(carbonate-urea-urethane)s: Influence of hydrocarbon chain length in soft segment JF - Polymer Degradation and Stability N2 - Poly(carbonate-urethane)s (PCUs) exhibit improved resistance to hydrolytic degradation and in vivo stress cracking compared to poly(ester-urethane)s and their degradation leads to lower inflammation of the surrounding tissues. Therefore, PCUs are promising implant materials and are considered for devices such as artificial heart or spine implants. In this work, the hydrolytic stability of different poly(carbonate-urethane-urea)s (PCUUs) was studied under variation of the length of hydrocarbon chain (6, 9, 10, and 12 methylene units) between the carbonate linkages in the precursors. PCUUs were synthesized from isophorone diisocyanate and oligo(alkylene carbonate) diols using the moisture-cure method. The changes of sample weight, thermal and mechanical properties, morphology, as well as the degradation products after immersion in a buffer solution (PBS, pH = 7.4) for up to 10 weeks at 37 degrees C were monitored and analyzed. In addition, mechanical properties after 20 weeks (in PBS, 37 degrees C) were investigated. The gel content was determined based on swelling experiments in chloroform. Based on the DSC analysis, slight increases of melting transitions of PCUUs were observed, which were attributed to structure reorganization related to annealing at 37 degrees C rather than to the degradation of the PCUU. Tensile strength after 20 weeks of all investigated samples remained in the range of 29-39 MPa, whereas the elongation at break e(m) decreased only slightly and remained in the range between 670 and 800%. Based on the characterization of degradation products after up to 10 weeks of immersion it was assessed that oligomers are mainly consisting of hard segments containing urea linkages, which could be assigned to hindered-urea dissociation mechanism. The investigations confirmed good resistance of PCUUs to hydrolysis. Only minor changes in the crystallinity, as well as thermal and mechanical properties were observed and depended on hydrocarbon chain length in soft segment of PCUUs. (C) 2019 Published by Elsevier Ltd. KW - Poly(carbonate-urea-urethane)s KW - Hydrolytic stability KW - Degradation Y1 - 2019 SN - 0141-3910 SN - 1873-2321 VL - 161 SP - 283 EP - 297 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Rothe, Martin A1 - Zhao, Yuhang A1 - Kewes, Günter A1 - Kochovski, Zdravko A1 - Sigle, Wilfried A1 - van Aken, Peter A. A1 - Koch, Christoph A1 - Ballauff, Matthias A1 - Lu, Yan A1 - Benson, Oliver T1 - Silver nanowires with optimized silica coating as versatile plasmonic resonators JF - Scientific reports N2 - Metal nanoparticles are the most frequently used nanostructures in plasmonics. However, besides nanoparticles, metal nanowires feature several advantages for applications. Their elongation offers a larger interaction volume, their resonances can reach higher quality factors, and their mode structure provides better coupling into integrated hybrid dielectric-plasmonic circuits. It is crucial though, to control the distance of the wire to a supporting substrate, to another metal layer or to active materials with sub-nanometer precision. A dielectric coating can be utilized for distance control, but it must not degrade the plasmonic properties. In this paper, we introduce a controlled synthesis and coating approach for silver nanowires to fulfill these demands. We synthesize and characterize silver nanowires of around 70 nm in diameter. These nanowires are coated with nm-sized silica shells using a modified Stober method to achieve a homogeneous and smooth surface quality. We use transmission electron microscopy, dark-field microscopy and electron-energy loss spectroscopy to study morphology and plasmonic resonances of individual nanowires and quantify the influence of the silica coating. Thorough numerical simulations support the experimental findings showing that the coating does not deteriorate the plasmonic properties and thus introduce silver nanowires as usable building blocks for integrated hybrid plasmonic systems. Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-40380-5 SN - 2045-2322 VL - 9 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Is the term "Carbene" justified for remote N-heterocyclic carbenes (r-NHCs) and abnormal N-heterocyclic carbenes (aNHCs/MICs)? JF - Tetrahedron N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of typical N-heterocyclic carbenes NHCs, r-NHCs, a-NHCs and MICs 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. Prior to that both structures and 13C chemical shifts were calculated and in case of isolated carbenes the computed δ(13C)/ppm values compared (as a quality criterion for obtained structures) with the experimental ones. The TSNMRS values of the studied carbenes, which are in mesomeric equilibrium with zwitterionic (ylide/betaine/mesoionic) resonance contributors, are employed to qualify and quantify the present electronic structure and if the term carbene is still justified to denote the compounds studied. The results, thus obtained from spatial magnetic properties (TSNMRS), are compared with the geometry of the compounds, the corresponding WIBERG's bond index values, and the 13C chemical shifts especially of the carbene electron-deficient centre. KW - Carbene or zwitterions KW - Ylide KW - Mesomeric equilibrium of carbene/zwitterion KW - Through-space NMR shieldings (TSNMRS) KW - NICS Y1 - 2019 U6 - https://doi.org/10.1016/j.tet.2019.02.005 SN - 0040-4020 VL - 75 IS - 11 SP - 1548 EP - 1554 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Zaitsev-Doyle, John J. A1 - Puchert, Anke A1 - Pfeifer, Yannik A1 - Yan, Hao A1 - Yorke, Briony A. A1 - Müller-Werkmeister, Henrike A1 - Uetrecht, Charlotte A1 - Rehbein, Julia A1 - Huse, Nils A1 - Pearson, Arwen R. A1 - Sans, Marta T1 - Synthesis and characterisation of alpha-carboxynitrobenzyl photocaged l-aspartates for applications in time-resolved structural biology JF - RSC Advances N2 - We report a new synthetic route to a series of a-carboxynitrobenzyl photocaged L-aspartates for application in time-resolved structural biology. The resulting compounds were characterised in terms of UV/Vis absorption properties, aqueous solubility and stability, and photocleavage rates (tau = ms to ms) and quantum yields (phi = 0.05 to 0.14). Y1 - 2019 U6 - https://doi.org/10.1039/c9ra00968j SN - 2046-2069 VL - 9 IS - 15 SP - 8695 EP - 8699 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Jetzschmann, Katharina J. A1 - Tank, Steffen A1 - Jagerszki, Gyula A1 - Gyurcsanyi, Robert E. A1 - Wollenberger, Ulla A1 - Scheller, Frieder W. T1 - Bio-Electrosynthesis of Vectorially Imprinted Polymer Nanofilms for Cytochrome P450cam JF - ChemElectroChem N2 - A new approach for synthesizing a vectorially imprinted polymer (VIP) is presented for the microbial cytochrome P450cam enzyme. A surface attached binding motif of a natural reaction partner of the target protein, putidaredoxin (Pdx), is the anchor to the underlying transducer. The 15 amino acid peptide anchor, which stems from the largest continuous amino acid chain within the binding site of Pdx was modified: (i) internal cysteines were replaced by serines to prevent disulfide bond formation; (ii) 2 ethylene glycol units were attached to the N-terminus as a spacer region; and (iii) an N-terminal cysteine was added to allow the immobilization on the gold electrode surface. Immobilization on GCE was achieved via an N-(1-pyrenyl)maleimide (NPM) cross-linker. In this way oriented immobilization of P450cam was accomplished by binding it to a peptide-modified gold or glassy carbon electrode (GCE) prior to the electrosynthesis of a polymer nanofilm around the immobilized target. This VIP nanofilm enabled reversible oriented docking of P450cam as it is indicated by the catalytic oxygen reduction via direct electron transfer between the enzyme and the underlying electrode. Catalysis of oxygen reduction by P450cam bound to the VIP-modified GCE was used to measure rebinding to the VIP. The mild coupling of an oxidoreductase with the electrode may be appropriate for realizing electrode-driven substrate conversion by instable P450 enzymes without the need of NADPH co-factor. KW - cytochrome P450 KW - direct electron transfer KW - electropolymerization KW - molecularly imprinted polymers KW - protein imprinting Y1 - 2019 U6 - https://doi.org/10.1002/celc.201801851 SN - 2196-0216 VL - 6 IS - 6 SP - 1818 EP - 1823 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Vogel, Stefanie A1 - Ebel, Kenny A1 - Schürmann, Robin Mathis A1 - Heck, Christian A1 - Meiling, Till A1 - Milosavljevic, Aleksandar R. A1 - Giuliani, Alexandre A1 - Bald, Ilko T1 - Vacuum-UV and Low-Energy Electron-Induced DNA Strand Breaks BT - Influence of the DNA Sequence and Substrate JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - DNA is effectively damaged by radiation, which can on the one hand lead to cancer and is on the other hand directly exploited in the treatment of tumor tissue. DNA strand breaks are already induced by photons having an energy below the ionization energy of DNA. At high photon energies, most of the DNA strand breaks are induced by low-energy secondary electrons. In the present study we quantified photon and electron induced DNA strand breaks in four different 12mer oligonucleotides. They are irradiated directly with 8.44 eV vacuum ultraviolet (VUV) photons and 8.8 eV low energy electrons (LEE). By using Si instead of VUV transparent CaF2 as a substrate the VUV exposure leads to an additional release of LEEs, which have a maximum energy of 3.6 eV and can significantly enhance strand break cross sections. Atomic force microscopy is used to visualize strand breaks on DNA origami platforms and to determine absolute values for the strand break cross sections. Upon irradiation with 8.44 eV photons all the investigated sequences show very similar strand break cross sections in the range of 1.7-2.3x10(-16) cm(2). The strand break cross sections for LEE irradiation at 8.8 eV are one to two orders of magnitude larger than the ones for VUV photons, and a slight sequence dependence is observed. The sequence dependence is even more pronounced for LEEs with energies <3.6 eV. The present results help to assess DNA damage by photons and electrons close to the ionization threshold. KW - DNA origami KW - DNA radiation damage KW - DNA strand breaks KW - low-energy electrons KW - vacuum-UV radiation Y1 - 2019 U6 - https://doi.org/10.1002/cphc.201801152 SN - 1439-4235 SN - 1439-7641 VL - 20 IS - 6 SP - 823 EP - 830 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Mehr, Fatemeh Naderi A1 - Grigoriev, Dmitry A1 - Puretskiy, Nikolay A1 - Böker, Alexander T1 - Mono-patchy zwitterionic microcolloids as building blocks for pH-controlled self-assembly JF - Soft matter N2 - A directional molecular interaction between microcolloids can be achieved through pre-defined sites on their surface, patches, which might make them follow each other in a controlled way and assemble into target structures of more complexity. In this article, we report the successful generation and characterization of mono-patchy melamine-formaldehyde microparticles with oppositely charged patches made of poly(methyl vinyl ether-alt-maleic acid) or polyethyleneimine via microcontact printing. The study of their self-aggregation behavior in solution shows that by change of pH, particle dimers are formed via attractive electrostatic force between the patchy and non-patchy surface of the particles, which reaches its optimum at a specific pH. Y1 - 2019 U6 - https://doi.org/10.1039/c8sm02151a SN - 1744-683X SN - 1744-6848 VL - 15 IS - 11 SP - 2430 EP - 2438 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Heiden, Sophia A1 - Usvyat, Denis A1 - Saalfrank, Peter T1 - Theoretical Surface Science Beyond Gradient-Corrected Density Functional Theory BT - Water at alpha-Al2O3(0001) as a Case Study JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - The quantum chemical description of the adsorption, vibrations, and reactions of molecules at periodic solid surfaces is frequently based on a methodological "standard model": density functional theory (DFT) in the generalized gradient approximation (GGA), using plane wave bases and three-dimensional supercells. Although the computationally efficient GGA functionals can be very successful, cases are known where they do not perform so well. Most importantly, activation energies for chemical reactions are typically underestimated, with the consequence of computed reaction rates being too large. In this work, we consider a well-studied model system: water or water fragments adsorbed on an Al-terminated alpha-Al2O3(0001) surface as a test bed for studying the performance of electronic structure methods, both from DFT and wave function theory. On the DFT side, we employ two GGA exchange correlation functionals: PW91 and PBE with and without dispersion corrections, whose results are then compared to those of hybrid functionals B3LYP and HSE06. Further, we follow a periodic wave function approach in the form of local second-order Moller-Plesset perturbation theory, LMP2, on a Hartree-Fock reference. En route, we address issues arising from the choice of the basis set. The key findings of our study are as follows: (i) DFT-GGA adsorption energies are in reasonable agreement with both hybrid-DFT and LMP2 values. In particular, the deviations between the relative energies, corresponding to different adsorption structures, are in the range of the error due to missing dispersion corrections or the basis set error. (ii) Harmonic DFT-GGA vibrational frequencies for oxygen hydrogen stretch modes are by several tens of wavenumbers red-shifted compared to corresponding hybrid-DFT values. The latter are in much better agreement with recent experimental data. (iii) The activation energy for a hydrogen diffusion reaction is grossly underestimated by GGA compared to hybrid-DFT or LMP2, which in turn are quite comparable. Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpcc.9b00407 SN - 1932-7447 VL - 123 IS - 11 SP - 6675 EP - 6684 PB - American Chemical Society CY - Washington ER - 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 - Quan, Ting A1 - Goubard-Bretesche, Nicolas A1 - Haerk, Eneli A1 - Kochovski, Zdravko A1 - Mei, Shilin A1 - Pinna, Nicola A1 - Ballauff, Matthias A1 - Lu, Yan T1 - Highly Dispersible Hexagonal Carbon-MoS2-Carbon Nanoplates with Hollow Sandwich Structures for Supercapacitors JF - Chemistry - a European journal N2 - MoS2, a typical layered transition-metal dichalcogenide, is promising as an electrode material in supercapacitors. However, its low electrical conductivity could lead to limited capacitance if applied in electrochemical devices. Herein, a new nanostructure composed of hollow carbon-MoS2-carbon was successfully synthesized through an L-cysteine-assisted hydrothermal method by using gibbsite as a template and polydopamine as a carbon precursor. After calcination and etching of the gibbsite template, uniform hollow platelets, which were made of a sandwich-like assembly of partial graphitic carbon and two-dimensional layered MoS2 flakes, were obtained. The platelets showed excellent dispersibility and stability in water, and good electrical conductivity due to carbon provided by the calcination of polydopamine coatings. The hollow nanoplate morphology of the material provided a high specific surface area of 543 m(2) g(-1), a total pore volume of 0.677 cm(3) g(-1), and fairly small mesopores (approximate to 5.3 nm). The material was applied in a symmetric supercapacitor and exhibited a specific capacitance of 248 F g(-1) (0.12 F cm(-2)) at a constant current density of 0.1 Ag-1; thus suggesting that hollow carbon-MoS2 carbon nanoplates are promising candidate materials for supercapacitors. KW - carbon KW - chalcogens KW - electrochemistry KW - nanostructures KW - supercapacitors Y1 - 2019 U6 - https://doi.org/10.1002/chem.201806060 SN - 0947-6539 SN - 1521-3765 VL - 25 IS - 18 SP - 4757 EP - 4766 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Koch, Andreas A1 - Stamboliyska, Bistra A1 - Mikhova, Bozhana A1 - Breznica-Selmani, Pranvera A1 - Mladenovska, Kristina A1 - Popovski, Emil T1 - Calculations of C-13 NMR chemical shifts and F-C coupling constants of ciprofloxacin JF - Magnetic resonance in chemistry N2 - Ciprofloxacin is a widely used fluoroquinolone antibiotic. In this work, a comprehensive evaluation of MP2 and DFT with different functionals and basis sets was carried out to select the most suitable level of theory for the study of the NMR properties of ciprofloxacin. Their relative predictive capabilities were evaluated comparing the theoretically predicted and experimental spectral data. Our computational results indicated that in contrast to the solid state, the molecule of ciprofloxacin does not exist as a zwitterion in gaseous state. The results of the calculations of the chemical shifts most close to the experimental were obtained with B3LYP/aug-cc-pVDZ. The F-C coupling constants were calculated systematically with different DFT methods and several basis sets. In general, the calculations of the coupling constants with the BHandH computational method including the applied in this work 6-311++G**, EPRII, and EPRIII basis sets showed a good reproducibility of the experimental values of the coupling constants. KW - C-13 chemical shifts KW - ciprofloxacin KW - DFT calculations KW - F-C coupling constants KW - NMR Y1 - 2019 U6 - https://doi.org/10.1002/mrc.4827 SN - 0749-1581 SN - 1097-458X VL - 57 IS - 4 SP - 75 EP - 84 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Omole, Ruth Anyango A1 - Moshi, Mainen Julius A1 - Heydenreich, Matthias A1 - Malebo, Hamisi Masanja A1 - Gathirwa, Jeremiah Waweru A1 - Ochieng, Sharon Alice A1 - Omosa, Leonida Kerubo A1 - Midiwo, Jacob Ogweno T1 - Two lignans derivatives and two fusicoccane diterpenoids from the whole plant of Hypoestes verticillaris (L.F.) Sol. Ex roem. & schult JF - Phytochemistry letters N2 - Bioassay-guided screening of Hypoestes verticillaris whole plant CH2Cl2: MeOH (1:1) extract for anti-plasmodial activity yielded four new compounds: two lignans 2, 6-dimethoxysavinin (1), 2,6-dimethoxy-(7E)-7,8-dehydroheliobuphthalmin (2); and two fusicoccane diterpenoids: 11(12)-epoxyhypoestenone (3) and 3(11)-epoxyhypoestenone (4). The chemical structures were determined using various spectroscopic techniques: UV-vis, IR, CD, 1D, 2D and MS. Two fractions (RAO-43B and RAO-43D) and the isolated compounds were tested for activity against CQ susceptible (D6) and resistant (W2) Plasmodium falciparum parasite strains, in vitro and the IC50 values determined. While the whole extract and some resultant fractions displayed moderate activity, the isolated compounds exhibited mild anti-plasmodial activity against the both strains ranging from IC50 value of 328 mu M in 1 to 93 mu M in 3 against W2 strain. KW - Fusicoccane diterpenes KW - Lignans KW - Hypoestes verticillaris KW - Anti-Plasmodial activity Y1 - 2019 U6 - https://doi.org/10.1016/j.phytol.2019.02.019 SN - 1874-3900 SN - 1876-7486 VL - 30 SP - 194 EP - 200 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mameri, Fatima A1 - Koutchoukali, Ouahiba A1 - Koutchoukali, Mohamed Salah A1 - Hartwig, Anne A1 - Nemdili, Leila A1 - Ulrich, Joachim T1 - Optimum operating conditions for manufacturing ibuprofen tablets coated with polyethylene glycol by melt crystallization process JF - Journal of Thermal Analysis and Calorimetry N2 - The aim of this work is to apply the melt crystallization technology to manufacture ibuprofen tablets coated with polyethylene glycol in a single step. This technology, based on a pastillation process, allows in situ separation between two components (active ingredient and coating material). The design and application of this technique depend on the thermo-physical properties of the substances used, as well as on the existence of a eutectic point in the phase diagram. To evaluate the prerequisite conditions, first, DSC curves, allowing the construction of the phase diagram of the binary system, were investigated and the eutectic point was determined (30 mass% ibuprofen, 52 degrees C). Then, the stability of the selected mixture (10:90 mass% of ibuprofen, PEG6000) was studied by thermogravimetric analysis. Finally, the coating quality was investigated under different operating conditions including viscosity, cooling plate temperature, the power of ultrasound and seeding. This parametric study showed that seeding with PEG6000 is necessary to obtain a hemispherical pastille shape, a suitable separation and a pure and thick coating layer. In addition to the optimization of operating conditions of the in situ coating process, it was possible to determine the optimum viscosity and the cooling plate temperature (271.77 m Pa s, 25 degrees C) to obtain a uniform and crystalline coating. During the deposition of molten drops on the cooled surface, the progression of crystal growth was monitored online by optical microscopy. According to the good separation achieved and to the purity and thickness of the microscopic cross-sectional material, the in situ coating process is conceivable for the production of PEG6000-coated ibuprofen tablets. KW - Ibuprofen KW - PEG6000 KW - Eutectic mixture KW - In situ coating KW - Melt crystallization KW - Pastillation Y1 - 2019 U6 - https://doi.org/10.1007/s10973-018-7667-z SN - 1388-6150 SN - 1588-2926 VL - 136 IS - 2 SP - 833 EP - 842 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Zhang, Su-Yun A1 - Guo, Wen-Bin A1 - Tang, Ying-Ying A1 - Xu, Jin-Qiu A1 - He, Zhang-Zhen T1 - Observation of Spin Relaxation in a Vanadate Chloride with Quasi-One-Dimensional Linear Chain JF - Crystal growth & design : integrating the fields of crystal engineering and crystal growth for the synthesis and applications of new materials N2 - A new cobalt(II) vanadate chloride, Pb2Co(OH)(V2O7)Cl, has been synthesized under mild hydrothermal conditions. It contains quasi-one-dimensional (1D) linear chains built by edge-sharing of (CoO6)-O-II octahedra. The cobalt(II) oxide chains are further interconnected by (V2O7)(4-) dimers into a three-dimensional (3D) anionic framework with Pb2+ and Cl- ions residing in Co4V8 12-member ring tunnels. The intrachain Co center dot center dot center dot Co distance is 3.041 angstrom, while the interchain distances are 8.742 and 9.256 angstrom. Magnetic measurements suggest the ferromagnetic intrachain and the antiferromagnetic interchain interactions with a specific value of J(intra)/J(inter) = 1.7 x 10(3). Zero-field heat capacity demonstrates the magnetic long-range ordering at 5.5 K. Alternating current (AC) magnetic susceptibility under zero external direct current (DC) fields displays two slow magnetic relaxations at low temperatures, giving characteristic relaxations (tau(0)) of 1.2(3) x 10(-12) and 1.9(4) x 10(-10) s with effective energy barriers (Delta(r)) of 76.1(2) and 48.4(5) K. The energy barrier between the spin up and spin-down states can be ascribed to the ferromagnetic spin chain and the Ising-like magnetic anisotropy in Pb2Co(OH)(V2O7)Cl. Y1 - 2019 U6 - https://doi.org/10.1021/acs.cgd.8b01839 SN - 1528-7483 SN - 1528-7505 VL - 19 IS - 4 SP - 2228 EP - 2234 PB - American Chemical Society CY - Washington 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 - Behrendt, Felix Nicolas A1 - Hess, Andreas A1 - Lehmann, Max A1 - Schmidt, Bernd A1 - Schlaad, Helmut T1 - Polymerization of cystine-derived monomers JF - Polymer Chemistry N2 - Cystine was used as a platform chemical to prepare cyclic and acyclic monomers for entropy-driven ringopening polymerization (ED-ROMP) via olefin or disulfide metathesis and for step-growth polymerization. The olefin ED-ROMP of an olefin/disulfide containing 16-atom macrocycle using the 3rd generation Grubbs catalyst was examined in greater detail. Kinetic studies revealed that the catalyst turned inactive during the polymerization, which limited the achievable (apparent) polymer molar mass to similar to 70 kg mol(-1). Such limitation could be overcome with the disulfide ED-ROMP of the same macrocycle to yield polymers with molar masses of up to 180 kg mol(-1). The step-growth polymerizations of acyclic diene and dithiol monomers via olefin metathesis or oxidation were far less effective and yielded just low molar mass polymers or oligomers; photopolymerization of a thiol-ene monomer produced a polyester with a molar mass of 35 kg mol(-1). Y1 - 2019 U6 - https://doi.org/10.1039/c9py00118b SN - 1759-9954 SN - 1759-9962 VL - 10 IS - 13 SP - 1636 EP - 1641 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - da Silva, Filipe Ferreira A1 - Varella, Marcio T. do N. A1 - Jones, Nykola C. A1 - Hoffmann, Soren Vronning A1 - Denifl, Stephan A1 - Bald, Ilko A1 - Kopyra, Janina T1 - Electron-Induced Reactions in 3-Bromopyruvic Acid JF - Chemistry - a European journal N2 - 3-Bromopyruvic acid (3BP) is a potential anticancer drug, the action of which on cellular metabolism is not yet entirely clear. The presence of a bromine atom suggests that it is also reactive towards low-energy electrons, which are produced in large quantities during tumour radiation therapy. Detailed knowledge of the interaction of 3BP with secondary electrons is a prerequisite to gain a complete picture of the effects of 3BP in different forms of cancer therapy. Herein, dissociative electron attachment (DEA) to 3BP in the gas phase has been studied both experimentally by using a crossed-beam setup and theoretically through scattering and quantum chemical calculations. These results are complemented by a vacuum ultraviolet absorption spectrum. The main fragmentation channel is the formation of Br- close to 0 eV and within several resonant features at 1.9 and 3-8 eV. At low electron energies, Br- formation proceeds through sigma* and pi* shape resonances, and at higher energies through core-excited resonances. It is found that the electron-capture cross-section is clearly increased compared with that of non-brominated pyruvic acid, but, at the same time, fragmentation reactions through DEA are significantly altered as well. The 3BP transient negative ion is subject to a lower number of fragmentation reactions than those of pyruvic acid, which indicates that 3BP could indeed act by modifying the electron-transport chains within oxidative phosphorylation. It could also act as a radio-sensitiser. KW - density functional calculations KW - dissociative electron attachment KW - drug discovery KW - gas-phase reactions KW - sensitizers Y1 - 2019 U6 - https://doi.org/10.1002/chem.201806132 SN - 0947-6539 SN - 1521-3765 VL - 25 IS - 21 SP - 5498 EP - 5506 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Polley, Nabarun A1 - Basak, Supratim A1 - Hass, Roland A1 - Pacholski, Claudia T1 - Fiber optic plasmonic sensors BT - Providing sensitive biosensor platforms with minimal lab equipment JF - Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics N2 - A simple, convenient, and inexpensive method to fabricate optical fiber based biosensors which utilize periodic hole arrays in gold films for signal transduction is reported. The process of hole array formation mainly relies on self-assembly of hydrogel microgels in combination with chemical gold film deposition and subsequent transfer of the perforated film onto an optical fiber tip. In the fabrication process solely chemical wet lab techniques are used, avoiding cost-intensive instrumentation or clean room facilities. The presented method for preparing fiber optic plasmonic sensors provides high throughput and is perfectly suited for commercialization using batch processing. The transfer of the perforated gold film onto an optical fiber tip does not affect the sensitivity of the biosensor ((420 +/- 83) nm/refractive index unit (RIU)), which is comparable to sensitivities of sensor platforms based on periodic hole arrays in gold films prepared by significantly more complex methods. Furthermore, real-time and in-line immunoassay studies with a specially designed 3D printed flow cell are presented exploiting the presented optical fiber based biosensors. KW - Surface plasmon resonance KW - Optical fiber KW - Bottom-up fabrication KW - Biosensor KW - 3D printed flow-cell Y1 - 2019 U6 - https://doi.org/10.1016/j.bios.2019.03.020 SN - 0956-5663 SN - 1873-4235 VL - 132 SP - 368 EP - 374 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Balk, Maria A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Quadruple-shape hydrogels JF - Smart materials and structures N2 - The capability of directed movements by two subsequent shape changes could be implemented in shape-memory hydrogels by incorporation of two types of crystallizable side chains While in non-swollen polymer networks even more directed movements could be realized, the creation of multi-shape hydrogels is still a challenge. We hypothesize that a quadruple-shape effect in hydrogels can be realized, when a swelling capacity almost independent of temperature is generated, whereby directed movements could be enabled, which are not related to swelling. In this case, entropy elastic recovery could be realized by hydrophilic segments and the fixation of different macroscopic shapes by means of three semi-crystalline side chains generating temporary crosslinks. Monomethacrylated semi-crystalline oligomers were connected as side chains in a hydrophilic polymer network via radical copolymerization. Computer assisted modelling was utilized to design a demonstrator capable of complex shape shifts by creating a casting mold via 3D printing from polyvinyl alcohol. The demonstrator was obtained after copolymerization of polymer network forming components within the mold, which was subsequently dissolved in water. A thermally-induced quadruple-shape effect was realized after equilibrium swelling of the polymer network in water. Three directed movements were successfully obtained when the temperature was continuously increased from 5 degrees C to 90 degrees C with a recovery ratio of the original shape above 90%. Hence, a thermally-induced quadruple-shape effect as new record for hydrogels was realized. Here, the temperature range for the multi-shape effect was limited by water as swelling media (0 degrees C-100 degrees C), simultaneously distinctly separated thermal transitions were required, and the overall elasticity indispensable for successive deformations was reduced as result of partially chain segment orientation induced by swelling in water. Conclusively the challenges for penta- or hexa-shape gels are the design of systems enabling higher elastic deformability and covering a larger temperature range by switching to a different solvent. KW - shape-memory KW - hydrogels KW - semi-crystalline Y1 - 2019 U6 - https://doi.org/10.1088/1361-665X/ab0e91 SN - 0964-1726 SN - 1361-665X VL - 28 IS - 5 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Zhang, Quanchao A1 - Rudolph, Tobias A1 - Benitez, Alejandro J. A1 - Gould, Oliver E. C. A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Temperature-controlled reversible pore size change of electrospun fibrous shape-memory polymer actuator based meshes JF - Smart materials and structures N2 - Fibrous membranes capable of dynamically responding to external stimuli are highly desirable in textiles and biomedical materials, where adaptive behavior is required to accommodate complex environmental changes. For example, the creation of fabrics with temperature-dependent moisture permeability or self-regulating membranes for air filtration is dependent on the development of materials that exhibit a reversible stimuli-responsive pore size change. Here, by imbuing covalently crosslinked poly(ε-caprolactone) (cPCL) fibrous meshes with a reversible bidirectional shape-memory polymer actuation (rbSMPA) we create a material capable of temperature-controlled changes in porosity. Cyclic thermomechanical testing was used to characterize the mechanical properties of the meshes, which were composed of randomly arranged microfibers with diameters of 2.3 ± 0.6 μm giving an average pore size of approx. 10 μm. When subjected to programming strains of εm = 300% and 100% reversible strain changes of εʹrev = 22% ± 1% and 6% ± 1% were measured, with switching temperature ranges of 10 °C–30 °C and 45 °C–60 °C for heating and cooling, respectively. The rbSMPA of cPCL fibrous meshes generated a microscale reversible pore size change of 11% ± 3% (an average of 1.5 ± 0.6 μm), as measured by scanning electron microscopy. The incorporation of a two-way shape-memory actuation capability into fibrous meshes is anticipated to advance the development and application of smart membrane materials, creating commercially viable textiles and devices with enhanced performance and novel functionality. KW - reversible shape-memory effect KW - fiber meshes KW - electrospinning Y1 - 2019 U6 - https://doi.org/10.1088/1361-665X/ab10a1 SN - 0964-1726 SN - 1361-665X VL - 28 IS - 5 PB - IOP Publ. Ltd. CY - Bristol ER -