Trivalent ion overcharging on electrified graphene

The structure of the electrical double layer (EDL) formed near graphene in aqueous environments strongly impacts its performance for a plethora of applications, including capacitive deionization. In particular, adsorption and organization of multivalent counterions near the graphene interface can promote nonclassical behaviors of EDL including overcharging followed by co-ion adsorption. In this paper, we characterize the EDL formed near an electrified graphene interface in dilute aqueous YCl3 solution using in situ high resolution x-ray reflectivity (also known as crystal truncation rod (CTR)) and resonant anomalous x-ray reflectivity (RAXR). These interface-specific techniques reveal the electron density profiles with molecular-scale resolution. We find that yttrium ions (Y3+) readily adsorb to the negatively charged graphene surface to form an extended ion profile. This ion distribution resembles a classical diffuse layer but with a significantly high ion coverage, i.e., 1 Y3+ per 11.4 ± 1.6 Å2, compared to the value calculated from the capacitance measured by cyclic voltammetry (1 Y3+ per ~240 Å2). Such overcharging can be explained by co-adsorption of chloride that effectively screens the excess positive charge. The adsorbed Y3+ profile also shows a molecular-scale gap (≥5 Å) from the top graphene surfaces, which is attributed to the presence of intervening water molecules between the adsorbents and adsorbates as well as the lack of inner-sphere surface complexation on chemically inert graphene. We also demonstrate controlled adsorption by varying the applied potential and reveal consistent Y3+ ion position with respect to the surface and increasing cation coverage with increasing the magnitude of the negative potential. This is the first experimental description of a model graphene-aqueous system with controlled potential and provides important insights into the application of graphene-based systems for enhanced and selective ion separations.

Hardening of a quick-speed steel tool through nitration process with nitrogen controlled potential

The study of the gas nitriding method, which allows obtaining high-quality diffuse layers in high-speed steel P6M5 on the basis of an internal nitrogen hardening zone with no brittle nitride zone, has been viewed. Research results of phase composition of nitrided steel with a change in the nitrogen potential of the atmosphere during dilution of ammonia are presented. Nitrided tool increased resistance during drilling constructional steel and titanium alloy, which is due to precipitation hardening treatment of the internal nitrogenization zone using tungsten nitrides, is given.

A Green Protocol for the Electrochemical Synthesis of a Fluorescent Dye with Antibacterial Activity from Imipramine Oxidation

Electrochemical oxidation of imipramine (IMP) has been studied in aqueous solutions by cyclic voltammetry and controlled-potential coulometry techniques. Our voltammetric results show a complex behavior for oxidation of IMP at different pH values. In this study, we focused our attention on the electrochemical oxidation of IMP at a pH of about 5. Under these conditions, our results show that the oxidation of IMP leads to the formation of a unique dimer of IMP (DIMP). The structure of synthesized dimer is fully characterized by UV-visible, FTIR, 1H NMR, 13C NMR and mass spectrometry techniques. It seems that the first step in the oxidation of IMP is the cleavage of the alkyl group (formation of IMPH). After this, a domino oxidation-hydroxylation-dimerization-oxidation reaction, converts IMPH to (E)-10,10',11,11'-tetrahydro-[2,2'-bidibenzo[b,f]azepinylidene]-1,1'(5H,5'H)-dione (DIMP). The synthesis of DIMP is performed in an aqueous solution under mild conditions, without the need for any catalyst or oxidant. Based on our electrochemical findings as well as the identification of the final product, a possible reaction mechanism for IMP oxidation has been proposed. Conjugated double bonds in the DIMP structure cause the compound to become colored with sufficient fluorescence activity (excitation wave-length 535 nm and emission wave-length 625 nm). Moreover, DIMP has been evaluated for in vitro antibacterial. The antibacterial tests indicated that DIMP showed good antibacterial performance against all examined gram-positive and gram-negative bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Shigella sonnei).

ZIF-12/Fe-Cu LDH Composite as a High Performance Electrocatalyst for Water Oxidation

Layered double hydroxides (LDH) are being used as electrocatalysts for oxygen evolution reactions (OERs). However, low current densities limit their practical applications. Herein, we report a facile and economic synthesis of an iron-copper based LDH integrated with a cobalt-based metal-organic framework (ZIF-12) to form LDH-ZIF-12 composite (1) through a co-precipitation method. The as-synthesized composite 1 requires a low overpotential of 337 mV to achieve a catalytic current density of 10 mA cm−2 with a Tafel slope of 89 mV dec−1. Tafel analysis further demonstrates that 1 exhibits a slope of 89 mV dec−1 which is much lower than the slope of 284 mV dec−1 for LDH and 172 mV dec−1 for ZIF-12. The slope value of 1 is also lower than previously reported electrocatalysts, including Ni-Co LDH (113 mV dec−1) and Zn-Co LDH nanosheets (101 mV dec−1), under similar conditions. Controlled potential electrolysis and stability test experiments show the potential application of 1 as a heterogeneous electrocatalyst for water oxidation.

Huge magnetoresistance in topological insulator spin-valves at room temperature

Topological insulators (TI) have extremely high potential in spintronic applications. Here, a topological insulators thin-film (TITF) spin valve with the use of the segment gate-controlled potential exhibits a huge magnetoresistance (MR) value higher than 1000% at room temperature which is more than 50 times the MR of typical topological insulators (TI) spin-valves. A high spin-polarized current is provided by the band structure generated by the tunable segment potential. The results reveal a very large resistance difference between the parallel and antiparallel configurations. The MR effect is strongly influenced by the thin-film thickness, the gate potential, the gate size, and the distribution. The proposed results will help to not only improve the room-temperature performance of the spin-valves but also enhance the applications of magnetic memories and spintronic devices.

Development and Research of Electrochemical Cells of Gas Analyzers for Determination of Carbon Oxide in Gas Media

The method for determining the concentration of carbon oxide in vapor-gas mixtures, based on the method of controlled potential amperometry, which belongs to the category of absolute measurement methods, is proposed. Metrological characteristics of electrochemical cells: with diffusion supply of the analyzed gas; with diffusion gas supply; with condensed electrolyte and forced gas supply have been developed and studied

CREATION OF AUTOMATED LOW-INTENSITY IRRIGATION SYSTEMS CONTROLLED THROUGH AN INTERNET CHANNEL IN AZERBAIJAN (ASMO)

With the correct process management, low-intensity irrigation allows not only to drastically reduce water consumption for irrigation of agricultural crops, but also to provide the necessary microclimate for plants and the supply of water and fertilizers in the required amount directly to the root zone of plants, which contributes to the earlier entry of plants into the season fruiting and increased productivity while reducing water per unit of crop and reducing production costs. For this, we have developed a perfect safe technological system of automated irrigation based on IDAD with automated control of the controlled potential moisture supply of the plant, an optimized irriga-tion regime taking into account the controlled soil and agroclimatic parameters that affect the growth and develop-ment of the plant phase, while maintaining the ecological environment that contributes to obtaining a guaranteed and high-quality yield per unit area meeting the requirement of mi ovyh standards. The system of low-intensity irri-gation created by the results of the study compared to traditional surface irrigation methods is more technologically demanding and in the remote areas from settlements it is difficult to provide qualified service; to ensure their possi-ble efficiency, they require complex automation of the irrigation technological process.

Electron-Reservoir Effect on a Perylene Diimide Tethered Rhenium Bipyridine Complex for CO2 Reduction

Here we report on a molecular catalyst with a built-in electron-reservoir for enhanced CO2 conversion. The synthesis and characterization of this N-annulated perylene diimide (PDI) photosensitized Re(bpy) supramolecular dyad [Re(bpy-TAz-PDI)], as well as successful electro- and photocatalytic CO2-to-CO conversion, are detailed herein. Upon electrochemical reduction in the presence of CO2 and a proton source, Re(bpy-TAz-PDI) exhibited significant current enhancement, where the onset of electrocatalytic CO2 reduction for Re(bpy-TAz-PDI) occurred at a much less negative potential than standard Re(bpy) complexes. At an applied potential of -1.8 V vs. Fc+/0, 400 mV lower than the benchmark Re(dmbpy) catalyst, Re(bpy-TAz-PDI) was able to achieve the same catalytic activity (TONco = 24) and Faradaic efficiency (FE = 92 %) during controlled potential electrolysis (CPE) experiments. Through a combination of UV-visible-nearIR spectroelectrochemistry (SEC), FTIR SEC, and chemical reduction experiments, it was shown that the PDI-moiety served as an electron-reservoir for Re(bpy), thereby allowing catalytic activity at lower overpotentials. Density functional theory (DFT) studies probing the optimized geometries, frontier molecular orbitals, and spin-densities of various catalytic intermediates revealed that the geometric configuration of PDI, relative to the Re(bpy)-moiety, plays a critical role in accessing electrons from the electron-reservoir. The near identical performance of Re(bpy-TAz-PDI) at lower overpotentials relative to the benchmark Re(dmbpy) catalyst highlights the utility of organic chromophore electron-reservoirs as a method for lowering the required overpotential for CO2 conversion. <br>