Electron injection from nanostructured carbon electrodes at moderate cathodic potentials

Voltammograms of electrodes based on nanostructured carbon of different morphology (single-wall carbon nanotubes, carbon nanofilaments, columnar structures) are taken in hexamethylphosphortriamide solutions. For all listed electrodes, direct experimental proof of the electron injection to the electrolyte solution at moderate cathodic potentials is obtained. It is found that this phenomenon is associated with the existence of atomically sharp spots at the electrode surface, which operate as local cathodes for the electron emission. It is shown that the current-voltage characteristics for the electron injection to the electrolyte solution differ from those for the field electron emission current at the electrode/vacuum interface.     

New functionalized pyrazolines from 1-aroyl-2-phenylacetylenes and thiocarbonohydrazides

The reaction of 1-aroyl-2-phenylacetylenes with thiocarbonohydrazide and benzaldehyde thiocarbohydrazone in acetic acid-water or ethanol-water systems with the reagents in an equimolar ratio leads to the selective formation of 1-carbothiohydrazinoyl-5-hydroxy-3-phenyl-5-R-2-pyrazolines. Ring-chain tautomerism involving the enamine and hydrazone forms was detected for solutions of the pyrazolines (with R = 2-thienyl) in DMSO. Dedicated to Academician M. G. Voronkov on his 85th birthday. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1655–1661, November, 2006.     

Pyrroles from ketoximes and acetylene. 22. Dihaloethanes in place of acetylene in reactions with cyclohexanone oxime

4,5,6,7-Tetrahydroindole and its 1-vinyl derivative were obtained in overall yields of 30–60% by the reaction of cyclohexanone oxime with 1,2-dichloro- and 1,2-dibromoethane in the MOH-dimethyl sulfoxide (DMSO) superbase system (M = K, Na, Li). Nucleophilic substitution of the halogen in the dihaloethanes by the oximate anion to give the corresponding ethylene glycol bis (imido ether) is a side reaction. The effect of the reaction conditions on the yields of products and the selectivity of the process was examined.See [1] for communication 21.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1202–1204, September, 1982.     

Optimization of silicon dioxide surface functionalization protocol for designing the receptor layer of a biosensor for detecting explosives

The development of the receptor layer of the biosensor for detecting explosive compounds is described. The covalent modification has been chosen for immobilizing E. coli nitroreductase on the gate oxide of the ion-sensitive field effect transistor (ISFET) that is comprised of silicon dioxide. The self-assembled monolayer technique has been used for immobilization. This method assumes the usage of different silanes and spacer molecules for activating the surface of SiO₂. Two different immobilization strategies have been compared, one using asymmetric spacers (3-maleimidobenzoic acid N-hydroxysuccinimide ester (MBS) and 4-(4-maleimidophenyl)butyric acid N-hydroxysuccinimide ester (SMPB)) and another using a symmetric glutaric dialdehyde linker both accompanied by appropriate silanes. For the first method, the dependence of functionalization efficiency on silane concentration has been studied. The sufficient density of enzyme molecules on the surface of SiO₂ has been achieved at a concentration of silane of 0.0015%. The type of asymmetric linker has no influence on immobilization efficiency. The method implying glutaric dialdehyde results in higher activity of the immobilized enzyme. For this method, the immobilization procedure has been optimized. The method has been adapted for immobilization of E. coli nitroreductase inside the channel of a microfluidic system on the surface of ISFET. For this purpose, (3-aminopropyl)triethoxysilane (APTES) has been changed to the corresponding silatrane, and the concentration of the enzyme has been increased to 30 μg/mL. The optimized procedure has been successfully used to develop a biosensor for detecting explosives.     

New chiral Schiff bases derived from (+)- and (−)-α-pinenes in the metal complex catalyzed asymmetric oxidation of sulfides

New chiral Schiff bases were derived from (+)- and (−)-α-pinenes for the first time. Coordinated to vanadium ions, they can be used as ligands in catalytic oxidation of sulfides into chiral sulfoxides. Conditions for the asymmetric oxidation of thioanisole to methyl phenyl sulfoxide in optical purity up to 32% were found. Variation of substituents in the ligand has a significant effect not only on enantioselectivity of the reaction, but also on absolute configuration of the sulfoxide formed. Dedicated to Academician G. A. Tolstikov in honor of his 75th anniversary. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 105–113, January, 2008.     

Low-molecular-weight phenolic compounds from <Emphasis Type="Italic">Hedysarum theinum</Emphasis> roots

Isoflavonoids (−)-medicarpin, (−)-vestitol, formononetin, 8-hydroxydaidzein, and 6″-O-acetylononin were isolated for the first time in addition to (−)-catechin, (−)-epicatechin, protocatechoic acid, raspberry ketone, and rhododendrol from the alcohol extract of Hedysarum theinum roots. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–28, January–February, 2008.     

Cyclic structure of n-methyl- 2-aminobenzoyl- and 2-mercapto- benzoylhydrazones of fatty- aromatic aldehydes

It has been shown by ¹H NMR spectroscopic methods that the previously unknown N-methyl-2-amino-benzoyl- and 2-mercaptobenzoylhydrazones of phenylacetic and 3-phenylpropionic aldehydes have cyclic benzo-1,2,4-triazepine and benzo-1,3,4-thiadiazepine structures respectively.     

Bipolar Electrochemical Exfoliation of Graphite for Synthesizing Electrocatalysts of Oxygen Reduction

Russian Journal of Electrochemistry - A nanocomposite of few-layer graphene structures with cobalt oxides is synthesized for the first time in an aqueous electrolyte containing Co2+ ions by the...