Sorption of Iron(II) on Ferromanganese Nodules

The dynamic capacity, specific surface area, grindability, and wearability of filter materials based on pyrolusite were determined. The dynamic capacity of ferromanganese nodules was compared with the capacity of imported filter materials.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 599-605.Original Russian Text Copyright © 2005 by Chirkst, Cheremisina, Ivanov, Chistyakov.     

Electrolytic Synthesis of Binary Oxide Systems Based on Manganese(II) Oxide

Joint anodic deposition of manganese, cobalt, nickel, and chromium oxides, which form binary oxide systems, from two-component sulfate solutions of the constituent metals was studied under different electrolysis conditions.     

Development of a Ruthenium(II) Complex Based Luminescent Probe for Imaging Nitric Oxide Production in Living Cells

A unique ruthenium(II) complex, bis(2,2′‐bipyridine)(4‐(3,4‐diaminophenoxy)‐2,2′‐bipyridine)ruthenium(II) hexafluorophosphate ([(Ru(bpy)₂(dabpy)][PF₆]₂), has been designed and synthesized as a highly sensitive and selective luminescence probe for the imaging of nitric oxide (NO) production in living cells. The complex can specifically react with NO in aqueous buffers under aerobic conditions to yield its triazole derivative with a high reaction rate constant at the 10¹⁰ M ^?1 s^?1 level; this reaction is accompanied by a remarkable increase of the luminescence quantum yield from 0.13 to 2.2 %. Compared with organic probes, the new Ru^II complex probe shows the advantages of a large Stokes shift (>150 nm), water solubility, and a wide pH‐availability range (pH independent at pH>5). In addition, it was found that the new probe could be easily transferred into both living animal cells and plant cells by the coincubation method, whereas the triazole derivative was cell‐membrane impermeable. The probe was successfully used for luminescence‐imaging detection of the exogenous NO in mouse macrophage cells and endogenous NO in gardenia cells. The results demonstrated the efficacy and advantages of the new probe for NO detection in living cells.     

Highly Efficient Nitric Oxide Capture by Azole‐Based Ionic Liquids through Multiple‐Site Absorption

A novel method for highly efficient nitric oxide absorption by azole‐based ionic liquid was reported. The NO absorption capacity reached up to 4.52 mol per mol ionic liquid and is significant higher than the capacity other traditional absorbents. Moreover, the absorption of NO by this ionic liquid was reversible. Through a combination of experimental absorption, quantum chemical calculation, NMR and FT‐IR spectroscopic investigation, the results indicated that such high capacity originated from multiple‐site interactions between NO and the anion through the formation of NONOate with the chemical formula R¹R²N?(NO^?)?N=O, where R¹ and R² are alkyl groups. We believe that this highly efficient and reversible NO absorption by an azole‐based ionic liquid paves a new way for gas capture and utilization.     

Oxidation of Phenols and Hydroquinones by Mercury(II) Trifluoroacetate and Mercury(II) Oxide

Treatment of phenols with mercury(II) salts normally results in rapid electrophilic aromatic mercuration and formation of arylmercurial derivatives in good yield. The use of mercury(II) salts as oxidants for phenols and hydroquinones has not, however, been investigated in any detail. In 1935, Montignie reported that hydroquinone reduced mercury(II) iodide to mercury(O), but the organic reaction product was not identified.¹ A similar observation was made by Koton,² who found that reaction of hydroquinone, 4-hydroxy-aniline and pyrogallol with mercury(II) acetate did not result in mercuration but led to formation of mercury(0), while Ohno has described the “strong reducing action” of catechol and nitrohydroquinones to mercury(II) salts.³ Mercury(II) acetate has been shown to oxidise hydroquinone and 1,4-bis[β-(2,5-dihydroxyphenyl)-α-methylethylamino] anthraquinone to the corresponding quinones,^4,5 and treatment of 2,6-di-t-butyl-4-methylphenol—with mercury(II) oxide has been found to give the expected products of phenolic oxidative coupling via quinone methide formation.⁶     

Recovery of Cadmium(II) Ions with a Sulfur-Containing Carbon Sorbent

The sorptive properties of a sulfur-containing sorbent, selective with respect to cadmium(II) ions in extraction from aqueous solutions, including process solutions, were studied.     

Super-Paramagnetic Nanoparticles by Surface Imprinting on Graphene Oxide Modified Iron (II,III) with Application for the Determination of Ovalbumin by Absorption Spectroscopy

Protein surface imprinting produces materials capable of selective recognition and capture of proteins. Herein, a protein surface imprinted polymer on graphene oxide modified super-paramagnetic Fe₃O₄ nanoparticles is reported. The molecularly imprinted polymer was synthesized by ultrasound-assisted suspension polymerization, using ovalbumin as the template molecule, 3-aminophenylboronie acid as the functional monomer, and methylene-bis-acrylamide as the cross-linking agent. The nanoparticles were approximately 40 nanometers in size and super-paramagnetic. Moreover, these particles demonstrated considerably high adsorption capacity, fast adsorption kinetics, and selective binding affinities toward the template protein ovalbumin. The calibration curve of ovalbumin was linear from 5.0 × 10^?11 to 1.0 × 10^?10 molar. The limit of detection of ovalbumin was 2.0 × 10^?11 M. These results show that this super-paramagnetic material has potential for biological macromolecule separation and determination.     

Determination of Nitric Oxide by Glassy Carbon Electrodes Modified with Poly(Neutral Red)

Nitric oxide can be oxidized to NO⁻₂ (then to NO⁻₃) and reduced to N₂O at a glassy carbon electrode modified with the film of poly(neutral red). When the modified electrode is further coated with a thin Nafion film, the interference of NO⁻₂ can be almost thoroughly eliminated, and the electrode can be employed to detect nitric oxide.     

Polyfunctional Anion Exchanger as Sorbent of Copper(II) and Vanadium(V) Ions

Sorption of copper and vanadium ions from aqueous solutions by cross-linked anion exchanger based on a copolymer of glycidyl methacrylate with styrene and polyethylenimine was studied. The effect of the solution pH on the completeness of sorption is considered.     

Fluorescent Nitric Oxide Photodonors Based on BODIPY and Rhodamine Antennae

Two novel NO photodonors (NOPDs) based on BODIPY and Rhodamine antennae activatable with the highly biocompatible green light are reported. Both NOPDs exhibit considerable fluorescence emission and release NO with remarkable quantum efficiencies. The combination of the photoreleasing and emissive performance for both compounds is superior to those exhibited by other NOPDs based on similar light-harvesting centres, making them very intriguing for image-guided phototherapeutic applications. Preliminary biological data prove their easy visualization in cell environment due to the intense green and orange-red fluorescence and their photodynamic action on cancer cells due to the NO photo-liberated.     

Absorption of cesium on potassium cobalt hexacyanoferrate(II)

Potassium cobalt hexacyanoferrate(II) was synthesized with a composition K_1.70Co_1.12Fe(CN)₆ · 1H₂O, a mixture of K₂[CoFe(CN)₆] (85–88%) and K₂[CoFe(CN)₆] (12–15%). Ion exchange was found to be stoichiometric, the exchangeable ions being potassium and cobalt in the ratios presented for the corresponding phases. The effective capacity for cesium was 0.35 meq/g, which is only 6% of the theoretical capacity. Cesium is probably only absorbed as a monolayer on the surface of the crystallites.     

Effect of Chlorine and Nitrosyl Chloride on Nitrogen(II) Oxide Oxidation into Nitrogen(IV) Oxide

The effect of chlorine and nitrosyl chloride impurities on the regeneration of nitrogen(IV) oxide—oxidizing agent in oxychlorination of hydrocarbons—was studied at two temperatures. An assumption is made that the process occurs by radical-chain mechanism and involves chlorine oxides.     

Simple Fabrication of Amperometric Nitric Oxide Microsensors Based on Electropolymerized Membrane Films

Demand for highly sensitive, selective, and practically reliable sensors which could be easily fabricated is increasing for various applications in biological and biomedical systems. Thus, here we present a novel and simple amperometric NO microsensor based on electropolymerized polymeric films. The sensor consists of a platinized Pt disk anode (25‐μm diameter) which surface is modified with electropolymerized polymer films and a Ag/AgCl wire cathode coiled around the anode. Three different electropolymerized films prepared from m‐phenylenediamine (m‐PD), 2,3‐diaminonaphthalene (2,3‐DAN), and 5‐amino‐1‐naphthol (5A1N) are compared in terms of their permselectivity for NO over major biological interferents such as anionic nitrite, ascorbic acid, uric acid; neutral acetaminophen; and cationic dopamine. Poly‐5A1N film layer among the three different polymers shows the best anti‐interference characteristics for all the electroactive interferents examined. Indeed, single polymer film of electropolymerized 5A1N without any additional modification as a NO selective membrane is confirmed to be sufficient to reject anionic, neutral, as well as cationic interferents while allowing relatively high permeation of NO through it. Other analytical performance of the NO microsensor fabricated with poly‐5A1N is evaluated: reliable linear dynamic range (a few tens nM to μM); sensitivity of 122.0±2.5 pA/μM; detection limit of <5.8 nM (S/N=3); response time, t_90%<5 s, which are excellent when considering the small sensor size. Another sensor design which has both an anode (poly‐5A1N modified platinized Pt) and a cathode (Ag/AgCl disk) embedded in a single sensor body is also presented.     

Cyclic Voltammetry and Structural Studies of Nitric Oxide Monolayers Adsorbed on Pt(111)

The structural analysis of the adsorption of NO monolayers on Pt(111) from solution has been explored by cyclic voltammetry (CV) and X‐ray photoelectron spectroscopy (XPS) techniques. The monolayers were formed from acid solutions saturated with NO gas as well and from nitrite solutions in sulfuric acid. Results by both techniques indicate a maximum coverage of 0.2 monolayers as well as the presence of NO molecularly adsorbed on the surface with different orientations. The voltammetric oxidation of NO gives rise to two peaks separated in the voltammogram by 50 mV. This value is in agreement with the theoretical value of 9 kJ corresponding to the difference between different adsorption sites. A mechanism for the surface mediated oxidation process from adsorbed NO to NO₂ under potential control is proposed.     

Nitric Oxide Biosensors Based on the Immobilization of Hemoglobin on Mesoporous Titania Electrodes

A nanocrystalline TiO₂ film is an electrode material with large surface area which allows high levels of protein adsorption without loss of protein structure or activity. As an optically transparent semiconductor, titania can be used to carry out direct spectroelectrochemistry of proteins such as hemoglobin. We demonstrate that the high protein loading and the optical transparency and electrical conductivity of the Hb/TiO₂ films allow the optical and/or electrochemical sensing of nitric oxide. In particular we demonstrate the nitric oxide cycle of oxyhemoglobin immobilized on TiO₂ films and use it to electrochemically measure micromolar levels of nitric oxide.     

Determination of Hg(II) and Methylmercury by Electrothermal Atomic Absorption Spectrometry after Dispersive Solid-Phase Microextraction with a Graphene Oxide Magnetic Material

The toxicity of all species of mercury makes it necessary to implement analytical procedures capable of quantifying the different forms this element presents in the environment, even at very low concentrations. In addition, due to the assorted environmental and health consequences caused by each mercury species, it is desirable that the procedures are able to distinguish these forms. In nature, mercury is mainly found as Hg⁰, Hg²⁺ and methylmercury (MeHg), with the latter being rapidly assimilated by living organisms in the aquatic environment and biomagnified through the food chain. In this work, a dispersive solid-phase microextraction of Hg²⁺ and MeHg is proposed using as the adsorbent a magnetic hybrid material formed by graphene oxide and ferrite (Fe₃O₄@GO), along with a subsequent determination by electrothermal atomic absorption spectrometry (ETAAS). On the one hand, when dithizone at a pH = 5 is used as an auxiliary agent, both Hg(II) and MeHg are retained on the adsorbent. Next, for the determination of both species, the solid collected by the means of a magnet is suspended in a mixture of 50 µL of HNO₃ (8% v/v) and 50 µL of H₂O₂ at 30% v/v by heating for 10 min in an ultrasound thermostatic bath at 80 °C. On the other hand, when the sample is set at a pH = 9, Hg(II) and MeHg are also retained, but if the solid collected is washed with N-acetyl-L-cysteine only, then the Hg(II) remains on the adsorbent, and can be determined as indicated above. The proposed procedure exhibits an enrichment factor of 49 and the determination presents a linear range between 0.1 and 10 µg L⁻¹ of mercury. The procedure has been applied to the determination of mercury in water samples from different sources.     

Nitric oxide reactivity of fluorophore coordinated carboxylate-bridged diiron(II) and dicobalt(II) complexes

The synthesis, structural characterization, and NO reactivity of carboxylate-bridged dimetallic complexes were investigated. The diiron(II) complex [Fe(2)(mu-O(2)CAr(Tol))(4)(Ds-pip)(2)] (1), where O(2)CAr(Tol) = 2,6-di(p-tolyl)benzoate and Ds-pip = dansyl-piperazine, was prepared and determined by X-ray crystallography to have a paddlewheel geometry. This complex reacts with NO within 1 min with a concomitant 4-fold increase in fluorescence emission intensity ascribed to displacement of Ds-pip. Although the diiron complex reacts with NO, as revealed by infrared spectroscopic studies, its sensitivity to dioxygen renders it unsuitable as an atmospheric NO sensor. The air-stable dicobalt(II) analogue was also synthesized and its reactivity investigated. In solution, the dicobalt(II) complex exists as an equilibrium between paddlewheel [Co(2)(mu-O(2)CAr(Tol))(4)(Ds-pip)(2)] (2) and windmill [Co(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(Ds-pip)(2)] (3) geometric isomers. Conditions for crystallizing pure samples of each of these isomers are described. Reaction of 2 with excess NO proceeds by reductive nitrosylation giving [Co(mu-O(2)CAr(Tol))(2)(NO)(4)] (5), which is accompanied by release of the Ds-pip fluorophore that is N-nitrosated in the process. This reaction affords an overall 9.6-fold increase in fluorescence emission intensity, further demonstrating the potential utility of ligand dissociation as a strategy for designing fluorescence-based sensors to detect nitric oxide in a variety of contexts.