Impedance Analysis of Inherently Redox‐Active Ionic‐Liquid‐Based Photoelectrochemical Cells: Charge‐Transfer Mechanism in the Presence of an Additional Redox Couple

An intensive electrochemical impedance study was carried out to understand the charge‐transfer processes in photoelectrochemical (PEC) cells based on ionic liquid (IL) electrolytes. Three different electrolytes were utilized to understand the role of redox species as well as the medium on the charge‐transfer mechanism. The negligible diffusion resistance, despite the presence of two different redox species in the case of Fe(CN)₆^?4/?3 in IL, was explained on the basis of charge transfer between species of two different redox couples. Accordingly, the redox species are not required to travel through the bulk of the electrolyte for the removal of accumulated charges, as short‐range charge transfer between the IL and the Fe(CN)₆^?4/?3 species facilitates the removal of accumulated charges. It is also shown that PEC cells utilizing dual redox couples are highly stable with larger photoelectrochmeical windows, >3 V.     

Redox Properties of CeO2 at Low Temperature: The Direct Synthesis of Imines from Alcohol and Amine

We disclosed the redox properties of CeO₂ in organic reactions at low temperature of 303 K. CeO₂ works as the most effective heterogeneous catalyst for imine formation from benzyl alcohol and aniline at 303 K among various metal oxides and showed more than 38‐fold higher activity than other simple metal oxides. CeO₂ is applicable to the reaction of various alcohols and amines and gives high yields (80–98 %) and high selectivities (89–>99 %). Kinetic measurements, MS, and FTIR analyses demonstrated that the high activity of CeO₂ is a result of reactive oxygen species at the redox sites on CeO₂. This discovery can help to create a new field in metal oxide catalysis.     

Towards the Application of Structure–Property Relationship Modeling in Materials Science: Predicting the Seebeck Coefficient for Ionic Liquid/Redox Couple Systems

This work focuses on determining the influence of both ionic‐liquid (IL) type and redox couple concentration on Seebeck coefficient values of such a system. The quantitative structure–property relationship (QSPR) and read‐across techniques are proposed as methods to identify structural features of ILs (mixed with LiI/I₂ redox couple), which have the most influence on the Seebeck coefficient (S_e) values of the system. ILs consisting of small, symmetric cations and anions with high values of vertical electron binding energy are recognized as those with the highest values of S_e. In addition, the QSPR model enables the values of S_e to be predicted for each IL that belongs to the applicability domain of the model. The influence of the redox‐couple concentration on values of S_e is also quantitatively described. Thus, it is possible to calculate how the value of S_e will change with changing redox‐couple concentration. The presence of the LiI/I₂ redox couple in lower concentrations increases the values of S_e, as expected.     

Reactivity of a Nickel(II) Bis(amidate) Complex with meta‐Chloroperbenzoic Acid: Formation of a Potent Oxidizing Species

Herein, we report the formation of a highly reactive nickel–oxygen species that has been trapped following reaction of a Ni^II precursor bearing a macrocyclic bis(amidate) ligand with meta‐chloroperbenzoic acid (HmCPBA). This compound is only detectable at temperatures below 250 K and is much more reactive toward organic substrates (i.e., C?H bonds, C?C bonds, and sulfides) than previously reported well‐defined nickel–oxygen species. Remarkably, this species is formed by heterolytic O?O bond cleavage of a Ni–HmCPBA precursor, which is concluded from experimental and computational data. On the basis of spectroscopy and DFT calculations, this reactive species is proposed to be a Ni^III–oxyl compound.     

Non‐Thermal Plasma in Contact with Water: The Origin of Species

Non‐thermal atmospheric pressure plasma has attracted considerable attention in recent years due to its potential for biomedical applications. Determining the mechanism of the formation of reactive species in liquid treated with plasma is thus of paramount importance for both fundamental and applied research. In this work, the origin of reactive species in plasma‐treated aqueous solutions was investigated by using spin‐trapping, hydrogen and oxygen isotopic labelling and electron paramagnetic resonance (EPR) spectroscopy. The species originating from molecules in the liquid phase and those introduced with the feed gas were differentiated by EPR and ¹H NMR analysis of liquid samples. The effects of water vapour and oxygen admixtures in the feed gas were investigated. All the reactive species detected in the liquid samples were shown to be formed largely in the plasma gas phase. It is suggested that hydrogen peroxide (determined by UV/Vis analysis) is formed primarily in the plasma tube, whereas the radical species ?OOH, ?OH and ?H are proposed to originate from the region between the plasma nozzle and the liquid sample.     

Binding of Reactive Oxygen Species at FeS Cubane Clusters

Reactive oxygen species (ROS) play an important role in the biochemistry of the cell and occur in degenerative processes as well as in signal transduction. Iron?sulfur proteins are particularly oxygen‐sensitive and their inorganic cofactors frequently undergo ROS‐induced decomposition reactions. As experimental knowledge about these processes is still incomplete we present here a quantum chemical study of the relative energetics for the binding of the most relevant ROS to [Fe₄S₄] clusters. We find that cubane clusters with one uncoordinated Fe atom (as found, for instance, in aconitase) bind all oxygen derivatives considered, whereas activation of triplet O₂ to singlet O₂ is required for binding to valence‐saturated iron centers in these clusters. The radicals NO and OH feature the most exothermic binding energies to Fe atoms. Direct sulfoxidation of coordinating cysteine residues is only possible by OH or H₂O₂ as attacking agents. The thermodynamic picture of ROS binding to iron?sulfur clusters established here can serve as a starting point for studying reactivity‐modulating effects of the cluster‐embedding protein environment on ROS‐induced decomposition of iron?sulfur proteins.     

Exhaled breath condensate: Determination of non-volatile compounds and their potential for clinical diagnosis and monitoring. A review

Exhaled breath condensate is a promising, non-invasive, diagnostic sample obtained by condensation of exhaled breath. Starting from a historical perspective of early attempts of breath testing towards the contemporary state-of-the-art breath analysis, this review article focuses mainly on the progress in determination of non-volatile compounds in exhaled breath condensate. The mechanisms by which the aerosols/droplets of non-volatile compounds are formed in the airways are discussed with methodological consequences for sampling. Dilution of respiratory droplets is a major problem for correct clinical interpretation of the measured data and there is an urgent need for standardization of EBC. This applies also for collection instrumentation and therefore various commercial and in-house built devices are described and compared with regard to their design, function and collection parameters. The analytical techniques and methods for determination of non-volatile compounds as potential markers of oxidative stress and lung inflammation are scrutinized with an emphasis on method suitability, sensitivity and appropriateness. The relevance of clinical findings for each group of possible non-volatile markers of selected pulmonary diseases and methodological recommendations with emphasis on interdisciplinary collaboration that is essential for future development into a fully validated clinical diagnostic tool are given.