Electrical properties of polymeric composites based on nanocrystalline tin dioxide modified with copper iodide

Electrical properties of synthesized nanostructured materials based on nanocrystalline tin dioxide modified with copper iodide and polychlorotrifl uoroethylene were studied. It was shown that the complex dielectric permittivity in the microwave range and the low-frequency electrical conductivity of the polymeric composites depend on the copper iodide concentration on the surface of tin dioxide and reach the maximum values at a volume fraction of CuI of about 0.5. The percolation thresholds were determined for the three-component system. Their values increase from 0.04 to 0.05 vol. fraction as the content of copper iodide in the CuI/SnO₂ system is raised from 0.04 to 0.6 vol. fraction.     

Recent advances in surface chemistry of electrodes to promote direct enzymatic bioelectrocatalysis

Redox enzymes catalyze major reactions in microorganisms to supply energy for life. Their use in electrochemical biodevices requires their integration on electrodes, while maintaining their activity and optimizing their stability. In return, such applicative development puts forward the knowledge on involved catalytic mechanisms, providing a direct electrode connection of the enzyme is fulfilled. Enzymes being large molecules with active site embedded in an insulating moiety, direct bioelectrocatalysis supposes strategies for specific orientation of the enzyme to be developed. In this review, we summarize recent advances during the past 3 years in the chemical modification of electrodes favoring direct electrocatalysis. We present the different methodologies used according to the electrode materials, including metals, carbon-based electrodes, or porous structures and discuss the gained insights into bioelectrocatalysis. We especially focus on enzyme engineering, which appears as an emerging strategy for enzyme anchoring. Remaining challenges will be discussed with regard to these later findings.     

Double counting in LDA + DMFT—The example of NiO

An intrinsic issue of the LDA + DMFT approach is the so called double counting of interaction terms. How to choose the double-counting potential in a manner that is both physically sound and consistent is unknown. We have conducted an extensive study of the charge-transfer system NiO in the LDA + DMFT framework using quantum Monte Carlo and exact diagonalization as impurity solvers. By explicitly treating the double-counting correction as an adjustable parameter we systematically investigated the effects of different choices for the double counting on the spectral function. Different methods for fixing the double counting can drive the result from Mott insulating to almost metallic. We propose a reasonable scheme for the determination of double-counting corrections for insulating systems.