Graphene Oxide Functionalized Biosensor for Detection of Stress-Related Biomarkers

A graphene oxide (GO)-based cortisol biosensor was developed to accurately detect cortisol concentrations from sweat samples at point-of-care (POC) sites. A reference electrode, counter electrode, and working electrode make up the biosensor, and the working electrode was functionalized using multiple layers consisting of GO and antibodies, including Protein A, IgG, and anti-Cab. Sweat samples contact the anti-Cab antibodies to transport electrons to the electrode, resulting in an electrochemical current response. The sensor was tested at each additional functionalization layer and at cortisol concentrations between 0.1 and 150 ng/mL to determine how the current response differed. A potentiostat galvanostat device was used to measure and quantify the electrochemical response in the GO-based biosensor. In both tests, the electrochemical responses were reduced in magnitude with the addition of antibody layers and with increased cortisol concentrations. The proposed cortisol biosensor has increased accuracy with each additional functionalization layer, and the proposed device has the capability to accurately measure cortisol concentrations for diagnostic purposes.

On-site corrosion monitoring experience in concrete structures: potential improvements on the current-controlled polarization resistance method

The need for proactive maintenance of reinforced concrete structures with non-destructive testing (NDT) is less disputable today than ever. One of the most promising strategies in this regard is the in-situ measurement of the reinforcement corrosion rate. This study explored the reliability of modulated current confinement method (hereafter MCC) based on a review of in-situ measurements made with that technique in real-life structures over a 13-year period. The most prominent problems detected included defective confinement of the polarization current in low-resistivity environments and over-polarization of passive reinforcement. The findings, which showed enhancement of MCC reliability to depend on improving the electrochemical current regulation and control methodologies presently in place, are being applied to improve the design of the next generation of corrosion meters.

Photocatalytic Activity of Diverse Organic Radical Anions: Catalyst Discovery Enables Cleavage of Strong C(sp2)–N and C(sp2)–O Bonds

<div> <div> <div> <p>Herein, we leverage electrochemistry to examine the photocatalytic activity of a range of structurally diverse persistent radical anions and find that many are effective electrophotocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2)–N and C(sp2)–O bonds even when reduction potentials hundreds of mV more negative than Li0 are required. We illustrated several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employed electrochemical current measurements to perform a reaction progress kinetic analysis that revealed that the improved activity of this new catalyst was a consequence of an enhanced stability profile. </p> </div> </div> </div>

Photocatalytic Activity of Diverse Organic Radical Anions: Catalyst Discovery Enables Cleavage of Strong C(sp2)–N and C(sp2)–O Bonds

<div> <div> <div> <p>Herein, we leverage electrochemistry to examine the photocatalytic activity of a range of structurally diverse persistent radical anions and find that many are effective electrophotocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2)–N and C(sp2)–O bonds even when reduction potentials hundreds of mV more negative than Li0 are required. We illustrated several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employed electrochemical current measurements to perform a reaction progress kinetic analysis that revealed that the improved activity of this new catalyst was a consequence of an enhanced stability profile. </p> </div> </div> </div>

Diborides of transition metals: Properties, application and production. Review. Part 1. Titanium and vanadium diborides

The properties, applications and methods for producing titanium and vanadium diborides are considered. These diborides are oxygen-free refractory metal-like compounds. As a result, they are characterized by high values of thermal and electrical conductivity. Their hardness is relatively high. Titanium and vanadium diborides exhibit significant chemical resistance in aggressive environments. For these reasons, they have found application in modern technics. So, they are used as surfacing materials when applying wear-resistant coatings on steel products. It is also possible to use vanadium diboride as a catalyst in organic synthesis and the anode in renewable electrochemical current sources. Perspective are ceramics B4C – TiB2 and B4C – VB2 , which make it possible to obtain products based on boron carbide with high-quality performance characteristics, in particular, with increased crack resistance. Such composite ceramics are obtained by means of hot pressing, spark plasma sintering and pressureless sintering. The properties of refractory compounds depend on the content of impurities and dispersion. Therefore, to solve a specific problem associated with the use of refractory compounds, it is important to choose the method of their preparation correctly, to determine the admissible content of impurities in the starting components. This leads to the presence of different methods for the synthesis of borides. The main methods for their preparation are: synthesis from simple substances (metals and boron); borothermal reduction of oxides; carbothermal reduction (reduction of mixtures of metal oxides and boron with carbon; metallothermal reduction of mixtures of metal oxides and boron; carbide-boron reduction. Plasma-chemical synthesis (deposition from the vapor-gas phase) is also used to obtain diboride nanopowders. Each of these methods is characterized in the article.

Use of electrochemical current noise method to monitor carbon steel corrosion under mineral wool insulation

Corrosion of carbon steel under mineral wool insulation was studied using the electrochemical current noise (ECN) method. Intensities of corrosion were validated using gravimetry, and the form of corrosion confirmed using optical microscopy. The standard deviation of the current noise signal agreed with weight loss results and was demonstrated as a reliable indicator of the degree of corrosion under mineral wool insulation. Recurrence quantification analysis was used to extract feature variables from ECN signals, which were later used to develop a random forest model to identify the type of corrosion, i.e., uniform or localised corrosion. The trained model was successfully applied to predict the extent of localised corrosion associated with mineral wool insulation.

Electrochemical Evaluation of Chrysin Flavonoid as Corrosion Inhibitor for Mild Steel in Sulphuric Acid Solution

Recently research is focused on natural organic compounds as metallic corrosion inhibitors demonstrating good corrosion protection and efficiencies. Steel corrosion behavior in acid media was evaluated in the presence of a pure natural flavonoid metabolite named Chrysin present in different plants. The evaluation of corrosion protection was studied using polarization curves, electrochemical impedance spectroscopy (EIS) and electrochemical current density under potentiostatic conditions. Polarization curves present active dissolution and at high overpotentials two passivation regions were found. Slight corrosion protection was obtained from EIS measurements and potentiostatic curves at three different anodic potentials: -370, +216 and +600 mV, revealed a more stable passive film in the presence of Chrysin at both passive regions. High corrosion protection was obtained on the film formed at +600 mV during the first 4 hours of immersion.

Electrochemical characterization of an oil/water alternately wetted rotating cylinder electrode

To characterize the corrosion at oil/water interfaces, a vertically adjustable rotating cylinder electrode (VA-RCE) was developed based on the concept of “alternate wetting cell”, in which the electrochemical current reflecting the wet state of the RCE surface can be continuously monitored. Under a sinusoidal moving mode, the current waveform varied with the rotation rate and the longitudinal displacement speed or amplitude of the VA-RCE, implying that the dynamic wetting behavior of the VA-RCE surface in the oil/water interface region was influenced by the flow conditions; the replacement of oil phase by water phase became easier with increasing flow rate and alternating frequency of change between water wet and oil wet. The results also indicated that the wettability of the VA-RCE surface could be modified by the formation of corrosion products. All the results suggested that the VA-RCE could be used to quantitatively characterize the dynamic water/oil wetting state and the corrosion at an oil/water interface in a multiphase flow.

Electron Transfer via Helical Oligopeptide to Laccase Including Chiral Schiff Base Copper Mediators

The oxygen reduction efficiency of a laccase-modified electrode was found to depend on the chirality of the oligopeptide linker used to bind the enzyme to the surface. At the same time, the electron transfer between the cathode electrode and the enzyme is improved by using a copper(II) complex with amino-acid derivative Schiff base ligand with/without azobenzene moiety as a mediator. The increased electrochemical current under both O2 and N2 proves that both the mediators are active towards the enzyme.