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.     

Lattice dynamics of corundum crystals with vacancies in various charge states

The lattice dynamics of an α-Al₂O₃ crystal with vacancies in various charge states is simulated using the recursive method in the shell model. The frequencies of resonant vibrations induced by defects in various directions are calculated. Characteristic features in vibrational spectra of anion-nonstoichiometric α-Al₂O₃ crystals, mostly associated with changes in the effective interaction between vacancies and the nearest neighbor atoms, are analyzed and explained.     

Synthesis and Polymerization in Unsaturated Co β-Diketonates

Polymerization of some unsaturated -diketonates of cobalt containing double bonds both unconjugated and conjugated with a metal cycle. Unlike monomeric complexes, cobalt in metal-containing polymers was shown to have tetrahedral structure of the coordination polyhedron. The kinetic parameters of polymerization depend on electronic and steric properties of -diketonates.     

Real-time one-dimensional coherent imaging through single-mode fibers by space time conversion processors

We introduce and experimentally demonstrate a novel technique for one-dimensional coherent imaging through a single-mode optical fiber by use of a pulse shaper and a pulse imager. In contrast to the wavelength-division-multiplexed encoding technique, our approach preserves both amplitude and phase information of the optical signal transmitted through the fiber, allowing one to encode longitudinal in addition to transverse optical information. The effect of the fiber-material dispersion on our imaging technique is analyzed, and potential solutions are discussed.     

Simulation of the lattice dynamics of an Al-Cu-Fe icosahedral quasicrystal

The total and partial vibrational spectra of aluminum, copper, and iron atoms in an Al-Cu-Fe icosahedral quasicrystal are calculated by the recursive method. The calculations are based on the 1/1 crystal approximant. The interaction of atoms in the Al-Cu-Fe quasicrystal is described within the EAM model. The calculated spectra are in satisfactory agreement with the experimental data on neutron inelastic scattering.     

Optical properties of anodic aluminum oxide produced in a complex electrolyte

Features of the absorption, transmission, photoluminescence, and infrared (IR) spectra of anodic aluminum oxide (AAO) formed in a complex electrolyte and annealed at 800, 900, 1000, and 1300°C are investigated. The variations in the phase composition changes of the anodic aluminum oxide are reflected in the respective features of its optical properties. A decrease in the transmission coefficient in the visible range of the spectrum is shown for the phase series: amorphous AOA → γ-Al₂O₃, γ-, θ-, δ-Al₂O₃ mixture → α-Al₂O₃. It is established that the highest absorption coefficient is characteristic of α-Al₂O₃, and the amorphous samples are the most transparent in the visible range. An intensive luminescence band in the red region of the spectrum with maxima at 678 and 694 nm is found for α-Al₂O₃. The emergence of this band is explained by the presence of octahedrally coordinated Mn₊₄ and Cr₊₃ impurity ions in the structure. A luminescence band at 700–800 nm is observed for the mixture of low-temperature phases. Intense luminescence in the region 350–500 nm is found for amorphous AAO and γ-Al₂O₃.