Water Formation Reaction under Interfacial Confinement: Al0.25Si0.75O2 on O-Ru(0001)

Confined nanosized spaces at the interface between a metal and a seemingly inert material, such as a silicate, have recently been shown to influence the chemistry at the metal surface. In prior work, we observed that a bilayer (BL) silica on Ru(0001) can change the reaction pathway of the water formation reaction (WFR) near room temperature when compared to the bare metal. In this work, we looked at the effect of doping the silicate with Al, resulting in a stoichiometry of Al0.25Si0.75O2. We investigated the kinetics of WFR at elevated H2 pressures and various temperatures under interfacial confinement using ambient pressure X-ray photoelectron spectroscopy. The apparent activation energy was lower than that on bare Ru(0001) but higher than that on the BL-silica/Ru(0001). The apparent reaction order with respect to H2 was also determined. The increased residence time of water at the surface, resulting from the presence of the BL-aluminosilicate (and its subsequent electrostatic stabilization), favors the so-called disproportionation reaction pathway (*H2O + *O ↔ 2 *OH), but with a higher energy barrier than for pure BL-silica.

Reproducible perovskite solar cells using a simple solvent mediated sol−gel synthesized NiOx hole transport layer

Nickel oxide (NiOx) hole transport layer was made from nickel oxide powder by a simple process and non-stabilizer or chelating agent. We used ethanol as main solvent and nitric acid less than 2% as co-solvent. The formation reaction mechanism of NiOx thin film was also studied. Perovskite solar cells (PSCs) with the optimum thickness of 70 nm exhibited power conversion efficiency as high as 12.99%, which is superior to those of PSCs with their counterparts. The moisture stability of NiOx based device (non-encapsulated) remained above 70% of their initial output after 700h storage at ambient conditions.

Highly Stable Low Redox Potential Quinone for Aqueous Flow Batteries

Aqueous organic redox flow batteries are promising candidates for large-scale energy storage. However, the design of stable and inexpensive electrolytes is challenging. Here, we report a highly stable, low redox potential, and potentially inexpensive negolyte species, sodium 3,3',3'',3'''-((9,10-anthraquinone-2,6-diyl)bis(azanetriyl))tetrakis(propane-1-sulfonate) (2,6-N-TSAQ), which is synthesized in a single step from inexpensive precursors. Pairing 2,6-N-TSAQ with potassium ferrocyanide at pH 14 yielded a battery with the highest open-circuit voltage, 1.14 V, of any anthraquinone-based cell with a capacity fade rate <10%/yr. When 2,6-N-TSAQ was cycled at neutral pH, it exhibited two orders of magnitude higher capacity fade rate. The great difference in anthraquinone cycling stability at different pH is interpreted in terms of the thermodynamics of the anthrone formation reaction. This work shows the great potential of organic synthetic chemistry for the development of viable flow battery electrolytes and demonstrates the remarkable performance improvements achievable with an understanding of decomposition mechanisms.

SIMPLE AND HIGHLY SELECTIVE DIRECT STABILITY INDICATING ULTRAVIOLET AND INDIRECT VISIBLE SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF ENROFLOXACIN IN PHARMACEUTICALS

Three simple, economic, selective and accurate and precise spectrophotometric methods are developed for determination of enrofloxacin (EFX) in pharmaceuticals. Method A is based on the measurement of absorbance of EFX in 0.1M HOAc at 315 nm. The ketoxime formation reaction has been employed in method B, in which the absorbance measurement of EFX oxime product at 275 nm is described. The third method (Method C) is indirect one and is based on the oxidation of EFX by cerium(IV), reaction of unreacted cerium(IV) with p-toludine (p-TD) and measurement of coloured solution at 540 nm. The Beer’s law is obeyed in the concentration ranges of 1.2–24, 1–8, and 1–20 μg/mL EFX in methods A, B, and C, respectively, with the corresponding molar extinction coefficients of 1.52×104, 3.86×104, and 6.6×103 L/mol/cm. The regression coefficients of calibration lines are 0.9996, 0.9913, and –0.9965, in methods A, B, and C, respectively. The limits of detection (LOD) and quantification (LOQ) have also been reported for each method. The methods have been validated to check accuracy, precision, robustness and ruggedness. The application of the methods proposed to determine EFX in tablets has been described and the results have been compared with a standard method. The results of validation and application have been found to be with excellent agreement. The standard addition procedure has been adopted in recovery experiments to further ascertain the accuracy of the methods and the results of the experiments are well satisfied. The stability indicating ability of Method A has been studied by subjecting EFX to acid and alkaline hydrolysis, oxidative, thermal and UV degradation followed by measurement of absorbance of resultant EFX solutions at 315 nm. The results of degradation study indicated unsusceptible nature of EFX to any of the stress conditions.

Microwave Induced Green chemistry approach towards synthesis of heterocyclic compounds via C-N Bond Forming Reactions

: The synthesis of heterocyclic compounds via carbon-nitrogen (C-N) bond formation reaction is considered as an emerged and efficient protocol in the field of synthetic chemistry. The C–N bond-forming reactions can proceed through condensation, coupling, ring-opening, cyclization or ring closure process etc. The reactivity pattern of these reactions mainly depends upon the reaction conditions as well as the type of catalysts and reacting substances that are associated with the synthesis of heterocyclic compounds containing the C-N system including pyrazole, imidazole, pyridine, pyrimidine, thiazole, tetrazole, isoxazole, benzothiazine and benzimidazole etc. Further, the technique of microwave-induced synthesis becomes an alternative strategy for the sustainable production of structurally diverse organic compounds. This method provides a cleaner reaction, faster reaction rate, atom economy and energy-efficient. So, the utilization of microwave radiation in organic synthesis becomes resource-friendly and eco-friendly processes. It follows the green chemistry approach by using safer solvents, renewable starting materials and green catalysts. The unique feature of this method is to generate various types of bioactive or medicinal agents.

7,10-Dibromo-2,3-dicyanopyrazinophenanthrene Aggregates as a Photosensitizer for Nickel-Catalyzed Aryl Esterification

Self-assembled aggregates of 7,10-dibromo-2,3-dicyanopyrazinophenanthrene which act as a new organophotocatalyst in combination with Ni catalyst for the Caryl–Oacyl cross-coupling reactions of carboxylic acids with aryl halides are described. This visible-light-induced Caryl–Oacyl bond-formation reaction proceeds smoothly to afford aryl esters with satisfactory to excellent yields.

SYNTHESIS AND PROPERTIES OF OLIGODIURETANEDIOLS BASED ON A MIXTURE OF (2,4–2,6) TOLUILENDIISOCYANATE

The paper describes the synthesis, the reaction of a mixture of isomers (2,4–2,6) of toluilendiisocyanate with a double molar excess of aliphatic individual or oligomeric diols, a number of previously unknown oligodiuretanediols and their physicochemical constants. It is shown that with an increase in the synthesis temperature from 50 to 70 °C, the reaction time to complete depletion in the mixture of free NCO-groups decreases from 8–9 hours to 3–4 hours. The reaction temperature of 70–2 °С should be considered optimal, because at higher temperatures side reactions of free NCO-groups with already formed urethane ones are possible. Because the presence of even a small amount of moisture in the diols can provoke side effects during the urethane formation reaction, all of the above diols were dried from the adsorbed moisture by azeotropic distillation with toluene before use in the reaction. Since the final products are even at the synthesis temperature (68–70 °C) viscous liquids, and there are difficulties with the homogenization of the reaction mass during synthesis, and when unloading the finished product from the reaction plant, in all cases, the synthesis was performed in solution cyclohexanone by 50 % by weight of the final product. Control of the reaction was performed by changing the % wt. free NCO-groups in time. The reaction was considered complete if the measured % wt. free NCO-groups in the reaction mixture for at least one hour twice showed zero. The isolated oligodiuretanediols range from solid at room temperature to very viscous products, which significantly depends on the molecular weight of the diol used in the reaction (ie the concentration of urethane groups formed). They are homogeneous, transparent compounds that are readily soluble in esters, ethers, aromatic and halide-containing, aprotic solvents, ketones, poorly or completely insoluble in aliphatic saturated hydrocarbons. The structure of the synthesized oligomeric products is confirmed by functional analysis, IR–spectra. In the IR-spectra of each of the synthesized oligodiuretanediols there are no absorption bands in the region of 2270 cm-1, which confirms the complete completion of the reaction of urethane formation according to the scheme. At the same time, the absorption bands in the region of 3450 cm-1, 1720 cm-1, 1540 cm-1 are fixed, which are characteristic of the presence of urethane groups in the structure of the target products. As the chain length of the diol component –R– increases in the target product (which synchronously leads to an increase in molecular weight), the intensity of these absorption bands decreases, which is associated with a decrease in the concentration of formed urethane groups in the structure of oligodiuretanediols. The refractive index also decreases synchronously. Synthesized series of oligodiuretanediols can be used for synthesis on its basis of other classes of oligomers with the simultaneous presence in the structure of urethane groups. The ability of such compounds to be soluble in solvents of different nature has been studied, which provides information for the directions of their further use (varnishes, enamels, primers).