On the pointwise limits of sequences of Świątkowski functions

The characterization of the pointwise limits of the sequences of ?wi?tkowski functions is given. Modifications of ?wi?tkowski property with respect to different topologies finer than the Euclidean topology are discussed.     

Synergic effect of catalyst/binder in passivation side-products of Li-oxygen cells

Journal of Solid State Electrochemistry - While used in minor proportion respect to other components in cathode formulations, binders play a crucial role in lithium batteries cathode. This is...     

Zirconium Oxycarbide: A Highly Stable Catalyst Material for Electrochemical Energy Conversion

Metal carbides and oxycarbides have recently gained considerable interest due to their (electro)catalytic properties that differ from those of transition metals and that have potential to outperform them as well. The stability of zirconium oxycarbide nanopowders (ZrO_0.31C_0.69), synthesized via a hybrid solid-liquid route, is investigated in different gas atmospheres from room temperature to 800 °C by using in-situ X-ray diffraction and in-situ electrical impedance spectroscopy. To feature the properties of a structurally stable Zr oxycarbide with high oxygen content, a stoichiometry of ZrO_0.31C_0.69 has been selected. ZrO_0.31C_0.69 is stable in reducing gases with only minor amounts of tetragonal ZrO₂ being formed at high temperatures, whereas it decomposes in CO₂ and O₂ gas atmosphere. From online differential electrochemical mass spectrometry measurements, the hydrogen evolution reaction (HER) onset potential is determined at −0.4 V_RHE. CO₂ formation is detected at potentials as positive as 1.9 V_RHE as ZrO_0.31C_0.69 decomposition product, and oxygen is anodically formed at 2.5 V_RHE, which shows the high electrochemical stability of this material in acidic electrolyte. This peopwery makes the material suited for electrocatalytic reactions at anodic potentials, such as CO and alcohol oxidation reactions, in general.     

Tuning the Electron Storage Potential of a Charge-Photoaccumulating RuII Complex by a DFT-Guided Approach

Molecular photosensitizers that are able to store multiple reducing equivalents are of great interest in the field of solar fuel production, where most reactions involve multielectronic reduction processes. In order to increase the reducing power of a ruthenium tris-diimine charge-photoaccumulating complex, two structural modifications on its fused dipyridophenazine-pyridoquinolinone ligand were computationally investigated. Addition of an electron-donating oxime group was calculated to substantially decrease the reduction potentials of the complex, thus guiding the synthesis of a pyridoquinolinone-oxime derivative. Its spectroscopic and (spectro)electrochemical characterization experimentally confirmed the DFT predictions, with the first and second reduction processes cathodically shifted by −0.24 and −0.14 V, respectively, compared to the parent complex. Moreover, the ability of this novel artificial photosynthetic system to store two photogenerated electrons at a more reducing potential, via a proton-coupled electron-transfer mechanism, was demonstrated.     

Gold Difluorocarbenoid Complexes: Spectroscopic and Chemical Profiling

Gold carbenes of the general type [LAu=CR₂]⁺ are sufficiently long‐lived for spectroscopic inspection only if the substituents compensate for the largely missing stabilization of the carbene center by the [LAu]⁺ fragment. π‐Donation by two fluorine substituents (R=F) is insufficient; rather, difluorocarbene complexes are so deprived in electron density that they sequester even “weakly coordinating” anions such as triflate or triflimide. This particular bonding situation translates into unmistakable carbenium ion chemistry upon reaction with stilbene as a model substrate.     

Design of experiments as a valuable tool for biopharmaceutical analysis with (imaged) capillary isoelectric focusing

Capillary isoelectric focusing is indispensable for characterizing charge heterogeneity and isoelectric points of biopharmaceuticals. However, there are many influencing parameters and therefore method development is challenging. This study was performed to obtain an in‐depth understanding of the imaged CIEF methodology by applying a design of experiments approach. To describe the parameter's effects as objectively as possible, a polynomial regression model was derived for the most important responses. For this purpose, the reference monoclonal antibody suggested by the National Institute of Standards and Technology (NISTmAb) was used as test molecule. The total concentration and the mixing ratio of two types of carrier ampholytes and the added amounts of urea and l ‐arginine were selected as factors. The effects of these factors on 13 different responses such as resolution or pI values were investigated. In order to reduce the total number of experiments, a d ‐optimal design with 20 different parameter combinations and six replicates each was chosen. The most significant effects of the four factors were shown for the parameters related to separation efficiency and peak position. In addition, the extent of the factor's effect could be assessed. Depending on the selected factor combination, the pI value can differ up to approximately 0.15 pI units and the resolution value between main peak and adjacent basic peak can range from approximately 1.6 to 2.5, for example.     

Janus Graft Block Copolymers: Design of a Polymer Architecture for Independently Tuned Nanostructures and Polymer Properties

The graft‐through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self‐assembly of GBCPs resulted in ordered nanostructures with ultra‐small domain sizes down to 2.8 nm (half‐pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self‐assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique.