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- ItemA Diverse View of Science to Catalyse Change(Weinheim : Wiley-VCH, 2020) Urbina-Blanco, César A.; Jilani, Safia Z.; Speight, Isaiah R.; Bojdys, Michael J.; Friščić, Tomislav; Stoddart, J. Fraser; Nelson, Toby L.; Mack, James; Robinson, Renã A.S.; Waddell, Emanuel A.; Lutkenhaus, Jodie L.; Godfrey, Murrell; Abboud, Martine I.; Aderinto, Stephen O.; Aderohunmu, Damilola; Bibič, Lučka; Borges, João; Dong, Vy M.; Ferrins, Lori; Fung, Fun Man; John, Torsten; Lim, Felicia P.L.; Masters, Sarah L.; Mambwe, Dickson; Thordarson, Pall; Titirici, Maria-Magdalena; Tormet-González, Gabriela D.; Unterlass, Miriam M.; Wadle, Austin; Yam, Vivian W.-W.; Yang, Ying-WeiValuing diversity leads to scientific excellence, the progress of science and most importantly, it is simply the right thing to do. We can value diversity not only in words, but also in actions. From the structure of DNA,1 to computer science,2 and space-station batteries,3 several key scientific discoveries that enhance our lives today, were made by marginalized scientists. These three scientists, Rosalind E. Franklin, Alan M. Turing and Olga D. González-Sanabria, did not conform to the cultural expectations of how scientists should look and behave. Unfortunately, marginalized scientists are often viewed as just a resource rather than the lifeblood that constitutes science itself. We need to embrace scientists from all walks of life and corners of the globe; this will also mean that nobody is excluded from tackling the life-threatening societal challenges that lie ahead. An awareness of science policy is essential to safeguarding our future. Science policy deals with creating the framework and codes of conduct that determine how science can best serve society.4-6 Discussions around science policy are often accompanied by anecdotes of “good” and “bad” practices regarding the merits of diversity and inclusion. Excellence and truth, which flow inexorably from diversity and inclusion, are the bedrocks upon which science should influence political and economic outcomes. A vital area of science policy is to support the professional development of marginalized scientists, an objective that must be acted upon by scientific leaders and communicators...
- ItemSynthesis of Modified Poly(vinyl Alcohol)s and Their Degradation Using an Enzymatic Cascade(Weinheim : Wiley-VCH, 2023) von Haugwitz, Gerlis; Donnelly, Kian; Di Filippo, Mara; Breite, Daniel; Phippard, Max; Schulze, Agnes; Wei, Ren; Baumann, Marcus; Bornscheuer, Uwe T.Poly(vinyl alcohol) (PVA) is a water-soluble synthetic vinyl polymer with remarkable physical properties including thermostability and viscosity. Its biodegradability, however, is low even though a large amount of PVA is released into the environment. Established physical-chemical degradation methods for PVA have several disadvantages such as high price, low efficiency, and secondary pollution. Biodegradation of PVA by microorganisms is slow and frequently involves pyrroloquinoline quinone (PQQ)-dependent enzymes, making it expensive due to the costly cofactor and hence unattractive for industrial applications. In this study, we present a modified PVA film with improved properties as well as a PQQ-independent novel enzymatic cascade for the degradation of modified and unmodified PVA. The cascade consists of four steps catalyzed by three enzymes with in situ cofactor recycling technology making this cascade suitable for industrial applications.
- ItemFibroblast Response to Nanocolumnar TiO2 Structures Grown by Oblique Angle Sputter Deposition(Weinheim : Wiley-VCH, 2021) Kapprell, Uta; Friebe, Sabrina; Grüner, Susann; Grüner, Christoph; Kupferer, Astrid; Rauschenbach, Bernd; Mayr, Stefan G.Cells are established to sense and respond to the properties, including nano- and microscale morphology, of the substrate they adhere to, which opens up the possibility to tailor bioactivity. With this background, the potential of tilted TiO2 nanostructures grown by oblique angle sputtering to affect fibroblasts with particular focus on inducing anisotropy in cell behavior is explored. By depositing TiO2 at different oblique angles relative to the substrate normal, morphologies, columnar tilt angle, roughness, and distances between neighbored nanocolumns can be adjusted. To assess bioactivity of the resulting structures, L929-mouse fibroblasts are seeded in vitro on TiO2 nanostructured substrates. Angle-dependent movement and velocity distributions of the cells on differently tilted columns and a smooth reference sample are studied. Cell proliferation rates and cell areas are additional factors which provide information about viability and the well-being of cells. It could be shown that the local topography of the surface has an influence on the directed movement of the cells. © 2021 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH
- ItemOrientation‐dependent nanostructuring of titanium surfaces by low‐energy ion beam erosion(Chichester [u.a.] : Wiley, 2020) Bauer, Jens; Frost, FrankRegular nanoscopic ripple and dot patterns are fabricated on poly-crystalline titanium samples by irradiation with 1.5 keV argon ions at normal incidence. The morphology of the nanostructures is investigated by scanning electron microscopy and scanning force microscopy. The ripple structures exhibit a saw-tooth cross-section profile. Electron backscatter diffraction experiments are performed to analyze the local grain structure. The study suggests a distinct correlation of the nanostructure morphology to the crystallographic orientation of the titanium surface.
- ItemTiOx/Pt3Ti(111) surface-directed formation of electronically responsive supramolecular assemblies of tungsten oxide clusters(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2021) Moors, Marco; An, Yun; Kuc, Agnieszka; Monakhov, Kirill YuHighly ordered titanium oxide films grown on a Pt3Ti(111) alloy surface were utilized for the controlled immobilization and tip-induced electric field-triggered electronic manipulation of nanoscopic W3O9 clusters. Depending on the operating conditions, two different stable oxide phases, z'-TiO x and w'-TiO x , were produced. These phases show a strong effect on the adsorption characteristics and reactivity of W3O9 clusters, which are formed as a result of thermal evaporation of WO3 powder on the complex TiO x /Pt3Ti(111) surfaces under ultra-high vacuum conditions. The physisorbed tritungsten nano-oxides were found as isolated single units located on the metallic attraction points or as supramolecular self-assemblies with a W3O9-capped hexagonal scaffold of W3O9 units. By applying scanning tunneling microscopy to the W3O9-(W3O9)6 structures, individual units underwent a tip-induced reduction to W3O8. At elevated temperatures, agglomeration and growth of large WO3 islands, which thickness is strongly limited to a maximum of two unit cells, were observed. The findings boost progress toward template-directed nucleation, growth, networking, and charge state manipulation of functional molecular nanostructures on surfaces using operando techniques.
- ItemFour-Step Domino Reaction Enables Fully Controlled Non-Statistical Synthesis of Hexaarylbenzene with Six Different Aryl Groups*(Weinheim : Wiley-VCH, 2021) Grau, Benedikt W.; Dill, Maximilian; Hampel, Frank; Kahnt, Axel; Jux, Norbert; Tsogoeva, Svetlana B.Hexaarylbenzene (HAB) derivatives are versatile aromatic systems playing a significant role as chromophores, liquid crystalline materials, molecular receptors, molecular-scale devices, organic light-emitting diodes and candidates for organic electronics. Statistical synthesis of simple symmetrical HABs is known via cyclotrimerization or Diels–Alder reactions. By contrast, the synthesis of more complex, asymmetrical systems, and without involvement of statistical steps, remains an unsolved problem. Here we present a generally applicable synthetic strategy to access asymmetrical HAB via an atom-economical and high-yielding metal-free four-step domino reaction using nitrostyrenes and α,α-dicyanoolefins as easily available starting materials. Resulting domino product—functionalized triarylbenzene (TAB)—can be used as a key starting compound to furnish asymmetrically substituted hexaarylbenzenes in high overall yield and without involvement of statistical steps. This straightforward domino process represents a distinct approach to create diverse and still unexplored HAB scaffolds, containing six different aromatic rings around central benzene core. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemOn-chip mass spectrometric analysis in non-polar solvents by liquid beam infrared matrix-assisted laser dispersion/ionization(Berlin [u.a.] : Springer, 2021) Urban, Raphael D.; Fischer, Tillmann G.; Charvat, Ales; Wink, Konstantin; Krafft, Benjamin; Ohla, Stefan; Zeitler, Kirsten; Abel, Bernd; Belder, DetlevBy the on-chip integration of a droplet generator in front of an emitter tip, droplets of non-polar solvents are generated in a free jet of an aqueous matrix. When an IR laser irradiates this free liquid jet consisting of water as the continuous phase and the non-polar solvent as the dispersed droplet phase, the solutes in the droplets are ionized. This ionization at atmospheric pressure enables the mass spectrometric analysis of non-polar compounds with the aid of a surrounding aqueous matrix that absorbs IR light. This works both for non-polar solvents such as n-heptane and for water non-miscible solvents like chloroform. In a proof of concept study, this approach is applied to monitor a photooxidation of N-phenyl-1,2,3,4-tetrahydroisoquinoline. By using water as an infrared absorbing matrix, analytes, dissolved in non-polar solvents from reactions carried out on a microchip, can be desorbed and ionized for investigation by mass spectrometry.
- ItemLong-Living Holes in Grey Anatase TiO2 Enable Noble-Metal-Free and Sacrificial-Agent-Free Water Splitting(Weinheim : Wiley-VCH, 2020) Liu, Ning; Mohajernia, Shiva; Nguyen, Nhat Truong; Hejazi, Seyedsina; Plass, Fabian; Kahnt, Axel; Yokosawa, Tadahiro; Osvet, Andres; Spiecker, Erdmann; Guldi, Dirk M.; Schmuki, PatrikTitanium dioxide has been the benchmark semiconductor in photocatalysis for more than 40 years. Full water splitting, that is, decomposing water into H2 and O2 in stoichiometric amounts and with an acceptable activity, still remains a challenge, even when TiO2-based photocatalysts are used in combination with noble-metal co-catalysts. The bottleneck of anatase-type TiO2 remains the water oxidation, that is, the hole transfer reaction from pristine anatase to the aqueous environment. In this work, we report that “grey” (defect engineered) anatase can provide a drastically enhanced lifetime of photogenerated holes, which, in turn, enables an efficient oxidation reaction of water to peroxide via a two-electron pathway. As a result, a Ni@grey anatase TiO2 catalyst can be constructed with an impressive performance in terms of photocatalytic splitting of neutral water into H2 and a stoichiometric amount of H2O2 without the need of any noble metals or sacrificial agents. The finding of long hole lifetimes in grey anatase opens up a wide spectrum of further photocatalytic applications of this material. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemMixed-ligand lanthanide complexes supported by ditopic bis(imino-methyl)-phenol/calix[4]arene macrocycles: synthesis, structures, and luminescence properties of [Ln2(L2)(MeOH)2] (Ln = La, Eu, Tb, Yb)(London : Soc., 2020) Ullmann, Steve; Hahn, Peter; Mini, Parvathy; Tuck, Kellie L.; Kahnt, Axel; Abel, Bernd; Gutierrez Suburu, Matias E.; Strassert, Cristian A.; Kersting, BertholdThe lanthanide binding ability of a macrocyclic ligand H6L2 comprising two bis(iminomethyl)phenol and two calix[4]arene units has been studied. H6L2 is a ditopic ligand which provides dinuclear neutral complexes of composition [Ln2(L2)(MeOH)2] (Ln = La (1), Eu (2), Tb (3), and Yb (4)) in very good yield. X-ray crystal structure analyses for 2 and 3 show that (L2)6- accommodates two seven coordinated lanthanide ions in a distorted monocapped trigonal prismatic/octahedral coordination environment. UV-vis spectroscopic titrations performed with La3+, Eu3+, Tb3+ and Yb3+ ions in mixed MeOH/CH2Cl2 solution (I = 0.01 M NBu4PF6) reveal that a 2 : 1 (metal : ligand) stoichiometry is present in solution, with log K11 and K21 values ranging from 5.25 to 6.64. The ratio α = K11/K21 of the stepwise formation constants for the mononuclear (L2 + M = ML2, log K11) and the dinuclear complexes (ML2 + M = M2L2, log K21) was found to be invariably smaller than unity indicating that the binding of the first Ln3+ ion augments the binding of the second Ln3+ ion. The present complexes are less luminescent than other seven-coordinated Eu and Tb complexes, which can be traced to vibrational relaxation of excited EuIII and TbIII states by the coligated MeOH and H2O molecules and/or low-lying ligand-to-metal charge-transfer (LMCT) states. © 2020 The Royal Society of Chemistry.
- ItemRole of Reaction Intermediate Diffusion on the Performance of Platinum Electrodes in Solid Acid Fuel Cells(Basel : MDPI, 2021) Lorenz, Oliver; Kühne, Alexander; Rudolph, Martin; Diyatmika, Wahyu; Prager, Andrea; Gerlach, Jürgen W.; Griebel, Jan; Winkler, Sara; Lotnyk, Andriy; Anders, André; Abel, BerndUnderstanding the reaction pathways for the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) is the key to design electrodes for solid acid fuel cells (SAFCs). In general, electrochemical reactions of a fuel cell are considered to occur at the triple-phase boundary where an electrocatalyst, electrolyte and gas phase are in contact. In this concept, diffusion processes of reaction intermediates from the catalyst to the electrolyte remain unconsidered. Here, we unravel the reaction pathways for open-structured Pt electrodes with various electrode thicknesses from 15 to 240 nm. These electrodes are characterized by a triple-phase boundary length and a thickness-depending double-phase boundary area. We reveal that the double-phase boundary is the active catalytic interface for the HOR. For Pt layers ≤ 60 nm, the HOR rate is rate-limited by the processes at the gas/catalyst and/or the catalyst/electrolyte interface while the hydrogen surface diffusion step is fast. For thicker layers (>60 nm), the diffusion of reaction intermediates on the surface of Pt be-comes the limiting process. For the ORR, the predominant reaction pathway is via the triple-phase boundary. The double-phase boundary contributes additionally with a diffusion length of a few nanometers. Based on our results, we propose that the molecular reaction mechanism at the electrode interfaces based upon the triple-phase boundary concept may need to be extended to an effective area near the triple-phase boundary length to include all catalytically relevant diffusion processes of the reaction intermediates. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.