TY - JOUR A1 - Melani, Giacomo A1 - Nagata, Yuki A1 - Saalfrank, Peter T1 - Vibrational energy relaxation of interfacial OH on a water-covered alpha-Al2O3(0001) surface BT - a non-equilibrium ab initio molecular dynamics study JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - Vibrational relaxation of adsorbates is a sensitive tool to probe energy transfer at gas/solid and liquid/solid interfaces. The most direct way to study relaxation dynamics uses time-resolved spectroscopy. Here we report on a non-equilibrium ab initio molecular dynamics (NE-AIMD) methodology to model vibrational relaxation of OH vibrations on a hydroxylated, water-covered alpha-Al2O3(0001) surface. In our NE-AIMD approach, after exciting selected O-H bonds their coupling to surface phonons and to the water adlayer is analyzed in detail, by following both the energy flow in time, as well as the time-evolution of Vibrational Density of States (VDOS) curves. The latter are obtained from Time-dependent Correlation Functions (TCFs) and serve as prototypical, generic representatives of time-resolved vibrational spectra. As most important results, (i) we find a few-picosecond lifetime of the excited modes and (ii) identify both hydrogen-bonded aluminols and water molecules in the adsorbed water layer as main dissipative channels, while the direct coupling to Al2O3 surface phonons is of minor importance on the timescales of interest. Our NE-AIMD/TCF methodology is powerful for complex adsorbate systems, in principle even reacting ones, and opens a way towards time-resolved vibrational spectroscopy. Y1 - 2021 U6 - https://doi.org/10.1039/d0cp03777j SN - 1463-9076 SN - 1463-9084 VL - 23 IS - 13 SP - 7714 EP - 7723 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Wang, Zhenyu A1 - Fritsch, Daniel A1 - Berendts, Stefan A1 - Lerch, Martin A1 - Breternitz, Joachim A1 - Schorr, Susan T1 - Elucidation of the reaction mechanism for the synthesis of ZnGeN2 through Zn2GeO4 ammonolysis JF - Chemical science / RSC, Royal Society of Chemistry N2 - Ternary II-IV-N-2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III-V materials to ternary II-IV-N-2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we present a systematic study of the reaction of Zn2GeO4 with NH3 that produces zinc germanium oxide nitrides, and ultimately approach stoichiometric ZnGeN2, using a combination of chemical analyses, X-ray powder diffraction and DFT calculations. Elucidating the reaction mechanism as being dominated by Zn and O extrusion at the later reaction stages, we give an insight into studying structure-property relationships in this emerging class of materials. Y1 - 2021 U6 - https://doi.org/10.1039/d1sc00328c SN - 2041-6539 VL - 12 IS - 24 SP - 8493 EP - 8500 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Nicolai, Merle Marie A1 - Weishaupt, Ann-Kathrin A1 - Baesler, Jessica A1 - Brinkmann, Vanessa A1 - Wellenberg, Anna A1 - Winkelbeiner, Nicola Lisa A1 - Gremme, Anna A1 - Aschner, Michael A1 - Fritz, Gerhard A1 - Schwerdtle, Tanja A1 - Bornhorst, Julia T1 - Effects of manganese on genomic integrity in the multicellular model organism Caenorhabditis elegans JF - International Journal of Molecular Sciences N2 - Although manganese (Mn) is an essential trace element, overexposure is associated with Mn-induced toxicity and neurological dysfunction. Even though Mn-induced oxidative stress is discussed extensively, neither the underlying mechanisms of the potential consequences of Mn-induced oxidative stress on DNA damage and DNA repair, nor the possibly resulting toxicity are characterized yet. In this study, we use the model organism Caenorhabditis elegans to investigate the mode of action of Mn toxicity, focusing on genomic integrity by means of DNA damage and DNA damage response. Experiments were conducted to analyze Mn bioavailability, lethality, and induction of DNA damage. Different deletion mutant strains were then used to investigate the role of base excision repair (BER) and dePARylation (DNA damage response) proteins in Mn-induced toxicity. The results indicate a dose- and time-dependent uptake of Mn, resulting in increased lethality. Excessive exposure to Mn decreases genomic integrity and activates BER. Altogether, this study characterizes the consequences of Mn exposure on genomic integrity and therefore broadens the molecular understanding of pathways underlying Mn-induced toxicity. Additionally, studying the basal poly(ADP-ribosylation) (PARylation) of worms lacking poly(ADP-ribose) glycohydrolase (PARG) parg-1 or parg-2 (two orthologue of PARG), indicates that parg-1 accounts for most of the glycohydrolase activity in worms. KW - manganese KW - oxidative stress KW - DNA repair KW - DNA damage response KW - Caenorhabditis elegans Y1 - 2021 U6 - https://doi.org/10.3390/ijms222010905 SN - 1422-0067 VL - 22 IS - 20 PB - MDPI CY - Basel ER - TY - JOUR A1 - Geiger, Christina A1 - Reitenbach, Julija A1 - Henschel, Cristiane A1 - Kreuzer, Lucas A1 - Widmann, Tobias A1 - Wang, Peixi A1 - Mangiapia, Gaetano A1 - Moulin, Jean-François A1 - Papadakis, Christine M. A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter T1 - Ternary nanoswitches realized with multiresponsive PMMA-b-PNIPMAM films in mixed water/acetone vapor atmospheres JF - Advanced engineering materials N2 - To systematically add functionality to nanoscale polymer switches, an understanding of their responsive behavior is crucial. Herein, solvent vapor stimuli are applied to thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylmethacrylamide) (PNIPMAM) block for realizing ternary nanoswitches. Three significantly distinct film states are successfully implemented by the combination of amphiphilicity and co-nonsolvency effect. The exposure of the thin films to nitrogen, pure water vapor, and mixed water/acetone (90 vol%/10 vol%) vapor switches the films from a dried to a hydrated (solvated and swollen) and a water/acetone-exchanged (solvated and contracted) equilibrium state. These three states have distinctly different film thicknesses and solvent contents, which act as switch positions "off," "on," and "standby." For understanding the switching process, time-of-flight neutron reflectometry (ToF-NR) and spectral reflectance (SR) studies of the swelling and dehydration process are complemented by information on the local solvation of functional groups probed with Fourier-transform infrared (FTIR) spectroscopy. An accelerated responsive behavior beyond a minimum hydration/solvation level is attributed to the fast build-up and depletion of the hydration shell of PNIPMAM, caused by its hydrophobic moieties promoting a cooperative hydration character. KW - co-nonsolvency KW - diblock copolymers KW - nanoswitches KW - neutron reflectometry KW - thin films Y1 - 2021 U6 - https://doi.org/10.1002/adem.202100191 SN - 1438-1656 SN - 1527-2648 VL - 23 IS - 11 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Quan, Ting A1 - Haerk, Eneli A1 - Xu, Yaolin A1 - Ahmet, Ibbi A1 - Höhn, Christian A1 - Mei, Shilin A1 - Lu, Yan T1 - Unveiling the formation of solid electrolyte interphase and its temperature dependence in "Water-in-Salt" supercapacitors JF - ACS applied materials & interfaces N2 - "Water-in-salt" (WIS) electrolytes have emerged as an excellent superconcentrated ionic medium for high-power energy storage systems such as supercapacitors due to their extended working potential compared to the conventional dilute aqueous electrolyte. In this work, we have investigated the performance of WIS supercapacitors using hollow carbon nanoplates as electrodes and compared it to that based on the conventional "salt-in-water" electrolytes. Moreover, the potentiostatic electrochemical impedance spectroscopy has been employed to provide an insightful look into the charge transport properties, which also, for the first time, reveals the formation of a solid-electrolyte interphase (SEI and their temperature-dependent impedance for charge transfer and adsorption. Furthermore, the effect of temperature on the electrochemical performance of the WIS supercapacitors in the temperature range from 15 to 60 degrees C has been studied, which presents a gravimetric capacitance of 128 F g(-1) and a volumetric capacitance of 197.12 F cm(-3) at 55 degrees C compared to 87.5 F g(-1) and 134.75 F cm(-3) at 15 degrees C. The in-depth understanding about the formation of SEI layer and the electrochemical performance at different temperatures for WIS supercapacitors will assist the efforts toward designing better aqueous electrolytes for supercapacitors. KW - "water-in-salt" KW - supercapacitor KW - solid electrolyte interphase KW - electrochemical impedance spectroscopy KW - temperature effect Y1 - 2021 U6 - https://doi.org/10.1021/acsami.0c19506 SN - 1944-8244 SN - 1944-8252 VL - 13 IS - 3 SP - 3979 EP - 3990 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schlappa, Stephanie A1 - Brenker, Lee Josephine A1 - Bressel, Lena A1 - Hass, Roland A1 - Münzberg, Marvin T1 - Process characterization of polyvinyl acetate emulsions applying inline photon density wave spectroscopy at high solid contents JF - Polymers / Molecular Diversity Preservation International N2 - The high solids semicontinuous emulsion polymerization of polyvinyl acetate using poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated by optical spectroscopy. The suitability of Photon Density Wave (PDW) spectroscopy as inline Process Analytical Technology (PAT) for emulsion polymerization processes at high solid contents (>40% (w/w)) is studied and evaluated. Inline data on absorption and scattering in the dispersion is obtained in real-time. The radical polymerization of vinyl acetate to polyvinyl acetate using ascorbic acid and sodium persulfate as redox initiator system and poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated. Starved-feed radical emulsion polymerization yielded particle sizes in the nanometer size regime. PDW spectroscopy is used to monitor the progress of polymerization by studying the absorption and scattering properties during the synthesis of dispersions with increasing monomer amount and correspondingly decreasing feed rate of protective colloid. Results are compared to particle sizes determined with offline dynamic light scattering (DLS) and static light scattering (SLS) during the synthesis. KW - photon density wave spectroscopy KW - multiple light scattering KW - emulsion KW - polymerization KW - process analytical technology KW - polyvinyl acetate Y1 - 2021 U6 - https://doi.org/10.3390/polym13040669 SN - 2073-4360 VL - 13 IS - 4 PB - MDPI CY - Basel ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Intramolecular carbene stabilization via 3c,2e bonding on basis of the magnetic criterion JF - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of bent cyclobutylcarbene 8, 1,2-diboretane-3-ylidene 9, and some carbene analogues of boron 14-18 as most intriguing examples of carbenes, which can be stabilized as homoaromatic systems with 3c,2e bonding, have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually, ring current effect/anisotropy effects as measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the degree of present 3c,2e-homoaromaticity. Results are confirmed by geometry (bond angles and bond lengths) and spectroscopic data, the delta(B-11)/ppm data and the C-13 chemical shifts of the carbene electron-deficient centre. KW - Cyclobutylcarbene KW - 1,2-diboretane-3-ylidene KW - 3c,2e-bonding KW - Through-space NMR shieldings (TSNMRS) KW - NICS Y1 - 2021 U6 - https://doi.org/10.1016/j.tet.2021.132357 SN - 0040-4020 SN - 1464-5416 VL - 95 PB - Elsevier Science CY - Amsterdam ER - TY - JOUR A1 - Buyinza, Daniel A1 - Derese, Solomon A1 - Ndakala, Albert A1 - Heydenreich, Matthias A1 - Yenesew, Abiy A1 - Koch, Andreas A1 - Oriko, Richard T1 - A coumestan and a coumaronochromone from Millettia lasiantha JF - Biochemical systematics and ecology N2 - The manuscript describes the phytochemical investigation of the roots, leaves and stem bark of Millettia lasiantha resulting in the isolation of twelve compounds including two new isomeric isoflavones lascoumestan and las-coumaronochromone. The structures of the new compounds were determined using different spectroscopic techniques. KW - Millettia lasiantha KW - Leguminosae KW - Coumestan KW - Coumaronochromone Y1 - 2021 U6 - https://doi.org/10.1016/j.bse.2021.104277 SN - 0305-1978 SN - 1873-2925 VL - 97 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Xu, Xun A1 - Nie, Yan A1 - Wang, Weiwei A1 - Ma, Nan A1 - Lendlein, Andreas T1 - Periodic thermomechanical modulation of toll-like receptor expression and distribution in mesenchymal stromal cells JF - MRS communications / a publication of the Materials Research Society N2 - Toll-like receptor (TLR) can trigger an immune response against virus including SARS-CoV-2. TLR expression/distribution is varying in mesenchymal stromal cells (MSCs) depending on their culture environments. Here, to explore the effect of periodic thermomechanical cues on TLRs, thermally controlled shape-memory polymer sheets with programmable actuation capacity were created. The proportion of MSCs expressing SARS-CoV-2-associated TLRs was increased upon stimulation. The TLR4/7 colocalization was promoted and retained in the endoplasmic reticula. The TLR redistribution was driven by myosin-mediated F-actin assembly. These results highlight the potential of boosting the immunity for combating COVID-19 via thermomechanical preconditioning of MSCs. KW - Actuation KW - Antiviral KW - Biomaterial KW - COVID-19 KW - Shape memory Y1 - 2021 U6 - https://doi.org/10.1557/s43579-021-00049-5 SN - 2159-6867 VL - 11 IS - 4 SP - 425 EP - 431 PB - Springer CY - Berlin ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Dative or coordinative carbon-boron bond in boron trapped N-heterocyclic carbenes (NHCs)? BT - an answer given on the magnetic criterion JF - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of isolated as well as B-C bond length varied model compounds (BR3 trapped NHCs) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the present dative vs. coordinative bond character of the boron-carbon bond in the trapped NHCs. Results are confirmed by bond lengths and B-11/C-13 chemical shift variations in the BR3 trapped NHCs. KW - NHCs KW - Dative vs. coordinative NHC -> BR3 bond KW - Through-space NMR KW - shieldings (TSNMRS) KW - NICS KW - Anisotropy effect Y1 - 2021 U6 - https://doi.org/10.1016/j.tet.2020.131787 SN - 0040-4020 SN - 1464-5416 VL - 80 PB - Elsevier CY - Amsterdam ER -