Just Bone Tired: Equine Bone Stress

The field of biophotoelectrochemistry and its application in biophotovoltaics and biosensors has gained more and more attention in recent years. Knowledge of the redox potentials of the catalytically active protein cofactors in biophotovoltaic devices is crucial for accurate modelling and in discerning the mechanisms of their operation. Here, for the first time, we used spectroelectrochemical methods to investigate thermodynamic parameters of a biophotoelectrode in situ. We determined redox potentials of two elements of the system: the primary electron donor in photosynthetic reaction centers (RCs) of the bacterium Rhodobacter sphaeroides and osmium-complex based redox mediators that are bound to a hydrogel matrix. We observe that the midpoint potential of the primary donor is shifted towards more positive potentials in comparison to literature data for RCs solubilized in buffered water solution, likely due to interaction with the polymer matrix. We also demonstrate that the osmium-complex modified redox polymer efficiently wires the RCs to the electrode, maintaining a high Internal Quantum Efficiency with approximately one electron per two photons generated (IQE=50±12%). Overall, this biophotoelectrode may be attractive for controlling the redox state of the protein when performing other types of experiments, e.g. time resolved absorption or fluorescence measurements, in order to gain insights into kinetic limitations and thereby help in the rational design of bioelectronic devices

Redox-Polymer-Wired [NiFeSe] Hydrogenase Variants with Enhanced O2 Stability for Triple-Protected High-Current-Density H2-Oxidation Bioanodes

Variants of the highly active [NiFeSe] hydrogenase from D. vulgaris Hildenborough that exhibit enhanced O2 tolerance were used as H2-oxidation catalysts in H2/O2 biofuel cells. Two [NiFeSe] variants were electrically wired by means of low-potential viologen-modified redox polymers and evaluated with respect to H2-oxidation and stability against O2 in the immobilized state. The two variants showed maximum current densities of (450±84) μA cm−2 for G491A and (476±172) μA cm−2 for variant G941S on glassy carbon electrodes and a higher O2 tolerance than the wild type. In addition, the polymer protected the enzyme from O2 damage and high-potential inactivation, establishing a triple protection for the bioanode. The use of gas-diffusion bioanodes provided current densities for H2-oxidation of up to 6.3 mA cm−2. Combination of the gas-diffusion bioanode with a bilirubin oxidase-based gas-diffusion O2-reducing biocathode in a membrane-free biofuel cell under anode-limiting conditions showed unprecedented benchmark power densities of 4.4 mW cm−2 at 0.7 V and an open-circuit voltage of 1.14 V even at moderate catalyst loadings, outperforming the previously reported system obtained with the [NiFeSe] wild type and the [NiFe] hydrogenase from D. vulgaris Miyazaki F.inpres

Photoreduction of CO2 with a Formate Dehydrogenase Driven by Photosystem II Using a Semi-artificial Z-Scheme Architecture.

Solar-driven coupling of water oxidation with CO2 reduction sustains life on our planet and is of high priority in contemporary energy research. Here, we report a photoelectrochemical tandem device that performs photocatalytic reduction of CO2 to formate. We employ a semi-artificial design, which wires a W-dependent formate dehydrogenase (FDH) cathode to a photoanode containing the photosynthetic water oxidation enzyme, Photosystem II, via a synthetic dye with complementary light absorption. From a biological perspective, the system achieves a metabolically inaccessible pathway of light-driven CO2 fixation to formate. From a synthetic point of view, it represents a proof-of-principle system utilizing precious-metal-free catalysts for selective CO2-to-formate conversion using water as an electron donor. This hybrid platform demonstrates the translatability and versatility of coupling abiotic and biotic components to create challenging models for solar fuel and chemical synthesis.ERC Consolidator Grant, EPSRC, Christian Doppler Research Association (Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development), the OMV group, Deutsche Forschungsgemeinschaft, European Union's Horizon 2020 MSCA, Fundação para a Ciência e Tecnologia (Portugal), COMPETE2020/POCI and European Union’s Horizon 202

Metal complexe modified silica particles - Synthesis and characterization of Stöber-SiO2-Materials and Co-Schiff-base complexes for their modification

Monodisperse, sphärische, unporöse Kieselgelpartikel mit Durchmessern von 140 - 600 nm wurden nach dem Stöber-Prozess dargestellt und mittels DLS, REM, DRIFT und BET Messungen charakterisiert. Dabei wurde der Partikeldurchmesser durch die Temperatur kontrolliert. Für die Modifizierung der Partikel wurden verschiedene Co(II)-Komplexe mit vierzähnigen N2O2-Schiff-Basen-Liganden dargestellt und mit spektroskopischen (NMR, IR, MS) und elektroanalytischen Methoden (CV) untersucht. Mittels DRIFT-Spektroskopie und Elementaranalyse konnte die erfolgreiche Immobilisierung eines Co(II)-Komplexes mit Alkoxysilylsubstituenten auf einem mit Hydroxygruppen modifiziertem Kieselgelmaterial nachgewiesen werden.Monodisperse, spherical, nonporous silica particles with diameters from 140 - 600 nm have been prepared by the Stöber process and were characterized by DLS, SEM, DRIFT and BET messurements. The particle diameter was controlled by temperature. Several Co(II) complexes with tetradentate N2O2-Schiff-base ligands have been synthesized as possible modifiers. These were studied by spectroscopic (NMR, IR, MS) and electrochemical (CV) methods. The successful immobilization of an alkoxysilyl substituted Co(II) complexe on hydroxy modified silica particles was studied by DRIFT spectroscopy and elemental analysis

Redox-active nanoparticles – viologen modified silica materials: synthesis and electrochemical characterization

Die vorliegende Arbeit beschreibt die Synthese und elektrochemische Charakterisierung von viologenmodifizierten core/shell-Systemen auf Basis von monodispersen, sphärischen und nicht-porösen Stöber-Kieselgelpartikeln mit Durchmessern im Submikrometerbereich. Das Trägermaterial wurde hinsichtlich seiner physikalischen und chemischen Eigenschaften mit materialwissenschaftlichen Methoden (Rasterelektronenmikroskopie, dynamische Lichtstreuung, BET, He-Pyknometrie, Gay-Lussac-Pyknometrie und DRIFT-Spektroskopie) untersucht. Die mit redoxaktiven Verbindungen (Viologene) modifizierten Materialien wurden sowohl mit spektroskopischen Methoden (CP/MAS-NMR-, Reflexion UV/Vis-, DRIFT-Spektroskopie) als auch mittels der Rasterelektronenmikroskopie, dynamischer Lichtstreuung und EDX-Analyse charakterisiert. Durch eine kovalente Verankerung der aktiven Spezies auf der Partikeloberfläche wird ein hohes Maß an Stabilität gewährleistet. Die spezifische Oberflächenkonzentration wurde argentometrisch und über die Bestimmung des C-Gehalts bestimmt (10 – 100 µmol/g). Elektrochemische Untersuchungen in wässrigen und nicht wässrigen Elektrolyten mittels voltammetrischer Methoden (CV und DPV) zeigten, dass durch den Ladungstransfer von der Elektrode zu immobilisierten Viologeneinheiten Elektronen-Hopping Prozesse in der redoxaktiven Hülle der Partikel (core) induziert werden. Diese ermöglichen eine Ladungsdiffusion über das gesamte Partikel und/oder über Partikelcluster. Weiterhin konnte mittels der ESR- sowie der UV/Vis-Spektroelektroskopie gezeigt werden, dass durch eine elektrochemische und/oder chemische Reduktion der immobilisierten Viologeneinheiten – in Bezug auf eine Disproportionierung – stabile Radikalspezies im Festkörper erzeugt werden können. Der damit verbundene Farbumschlag des Materials von gelb nach blau demonstriert, dass die in der vorliegenden Arbeit synthetisierten neuartigen core/shell Systeme potentielle Redoxindikatoren darstellen.The present work describes the synthesis and electrochemical characterization of novel viologen modified core/shell-systems based on nonporous, monodisperse, and spherical Stöber silica particles with diameters in the sub micrometer range. The physical and chemical properties of the silica base material was characterized by means of scanning electron microscopy, dynamic light scattering, measurement of the N2-adsorption-desorption isotherm (BET), helium and Gay-Lussac pycnometry as well as DRIFT-spectroscopy. The redox-active materials were characterizied by spectroscopic methods (CP/MAS-NMR, refelectance UV/Vis-, DRIFT-spectroscopy) as well as scanning electron microscopy, dynamic light scattering and EDS-analysis. A covalent attachment of the modifiers (viologens) ensures a stable anchoring of the redox-active centers on the particles´ surface. The specific surface concentration was estimated by elemental analysis (C-content) and by Fajans titration of the counter anions (10 – 100 µmol/g). Voltammetric experiments (CV and DPV) in aqueous and non-aqueous electrolytes show that electron hopping processes within the shell of the modified materials are coupled to the electron transfer reaction between the electrode and the redox-active sites on the particle surface. These hopping processes ensure charge diffusion within the whole shell and/or over particle clusters. EPR-spectroelectrochemical experiments as well as UV/Vis-spectroscopy clearly demonstrate that stable free radicals (with respect to disproportionation) in the immobilized state can be generated by bulk electrolysis or by chemical reduction of the viologen units with Na2S2O4. A color change from yellow to blue which is coupled to the reduction of the surface bound oxidized viologen units indicates that the presented core/shell structured materials are potential redox-indicators

Effect of the type and number of organic addends on fullerene acceptors for n‐type electronic devices: redox properties and energy levels

Fullerenes are still among the best performing electron acceptor materials for electronic applications such as organic solar cells, organic‐inorganic perovskite solar cells and transistors. We demonstrate that voltammetry is a very powerful tool for the determination of the redox potentials and thus the LUMO levels of various fullerene acceptor materials when identical conditions, i. e. same electrolyte, electrode material and potential standard, are used. The analyzed fullerene derivatives bear several types (indene, anthracene and 1,2‐dimethoxymethano groups) and numbers (mono‐, bis‐ and tris‐adducts) of addends. Our systematical study enables a direct correlation of the values obtained for the individual fullerenes, and a linear relationship of the redox potential and the number of addends was found. The high lying LUMO levels of the bis‐ and tris‐adducts are favorable in terms of a high open circuit voltage in combination with polymer donors in bulk heterojunction solar cells. Considering only high LUMO values IC60TA and IC70TA are the most promising materials for organic solar cells revealing a high VOC. The bis‐adducts of the fullerenes reveal LUMO levels that closely match the energy level of the widely used organometal trihalide CH3NH3PbI in perovskite solar cells