Reduction Of Nitrite Ions Research Articles

Feasibility of controlled nitric oxide generation via ascorbate induced chemical reduction of nitrite ions.

Inhalable nitric oxide (iNO) is a lifesaving, FDA-approved drug to improve oxygenation in persistent pulmonary hypertension of the newborn. iNO also has many other applications in lung diseases owing to its vasodilatory and antimicrobial effects. However, its wider therapeutic application is often prohibited by the high cost and logistical barriers of traditional NO/N2 gas tanks. Development of low-cost, portable and tankless nitric oxide (NO) generators is a critical need to advance iNO therapy. Here, we describe the feasibility of NO generation by the controlled reduction of nitrite (NO2-) ions. This was accomplished by using ascorbate to reduce NO2- ions mediated by a copper(I/II) redox pair complexed by an azo-crown ether ligand ([Cu(II)L]2+/[Cu(I)L]+) in the solution phase. We found that oxalate, a decomposition product of ascorbate, interferes with the NO generation from the copper-ligand complex. This interference was mitigated, and the reaction was further optimized. NO generation through this method was found to be highly controllable via its proportionality to the flow rate of NO2- injected into a reaction chamber containing the reducing components. Hence, this simple approach adds to the current collection of innovative methods under development to obviate the use of NO tanks for iNO delivery.

A practical FeP nanoarrays electrocatalyst for efficient catalytic reduction of nitrite ions in wastewater to ammonia

Ammonia production is an energy-intensive process while nitrite ions are a substantial environmental pollutant, therefore the conversion of nitrite ions (NO2-) into ammonia (NH3) via an electrochemical process is of great significance. Using a hydrothermal method plus a low temperature phosphating process, iron phosphide nanoarrays (FeP NA) were prepared on a Ti plate to form FeP NA|Ti, which was then used to efficiently convert NO2- ions into NH3. In a single-chamber cell using a neutral pH electrolyte, the Faradaic efficiency for nitrite to ammonia conversion reached 82.5 ± 2.3 %. Various parameters were optimized to ensure the high performance of FeP NA|Ti which were explained with mechanistic studies. It was found that atomic hydrogen (H*) greatly impacts both the reaction rate and selectivity. Furthermore, density functional theory (DFT) calculations reveal that the (211) and (011) facets of FeP are the main active faces for nitrite reduction where the nitrite ions tend to bind with two adjacent Fe atoms of FeP to ensure maximum performance.

Influence of potassium dichromate on the reduction of sulfur, nitrate and nitrite ions by bacteria Desulfuromonas sp.

This article presents the regularities of reduction of sulfur, nitrate and nitrite ions by sulfur reducing bacteria Desulfuromonas sp., which were isolated from the water of the man-made Yavorivske Lake (Lviv Region, Ukraine), under the influence of potassium dichromate. This bacteria in the process of anaerobic respiration can use and reduce different electron acceptors, such as sulfur, nitrates, nitrites, oxidized forms of heavy metals, in particular, hexavalent chromium. Technogenically altered ecotopes are characterized by complex pollution, so several electron acceptors are available to bacteria at the same time. Strains of microorganisms isolated from such ecotopes are adapted to unfavourable conditions and therefore have high biotechnological potential. The purpose of this work was to investigate the regularities of elemental sulfur, nitrate or nitrite ion usage by sulfidogenic bacteria of Desulfuromonas genus in conditions of simultaneous presence in the medium of another electron acceptor – Cr(VI), to establish the succession of reduction of electron acceptors by strains of these bacteria and to evaluate the efficiency of their possible application in technologies of complex purification of the environment from metal compounds and other inorganic toxicants. Bacteria were grown under anaerobic conditions in Kravtsov-Sorokin medium without SO42– and without Mohr’s salt for 10 days. To study the efficiency of sulfur, nitrate or nitrite ions’ reduction at simultaneous presence in the medium of Cr(VI) bacteria were sown in media with elemental sulfur, NaNO3, NaNO2 or K2Cr2O7 to final S0, NO3–, NO2–or Cr(VI) concentration in the medium of 3.47 (concentration of SO42– in medium of standard composition) or 1.74, 3.47, 5.21, 6.94 and 10.41 mM. Biomass was determined by the turbidimetric method, and the concentrations of nitrate, nitrite, ammonium ions, hydrogen sulfide, Cr(VI), Cr(ІІІ) in cultural liquid were determined spectrophotometrically. It has been established that Cr(VI) inhibits the biomass accumulation and hydrogen sulfide production by bacteria of Desulfuromonas sp. after simultaneous addition into the medium of 3.47 mM S0 and 1.74–10.41 mM Cr(VI). In the medium with the same initial content (3.47 mM) of S0 and Cr(VI) bacteria produced Cr(III) at concentrations 3.3–3.4 times higher than that of hydrogen sulfide. It has been shown that K2Cr2O7 inhibits biomass accumulation, nitrate ions’ reduction and ammonium ions’ production by bacteria after simultaneous addition into the medium of 3.47 mM NO3– and 1.74–10.41 mM Cr(VI) or 1.74–10.41 mM NO3– and 3.47 mM Cr(VI). In the medium with the same initial content (3.47 mM) of NO3– and Cr(VI) bacteria reduced up to 1.2 times more nitrate ions than Cr(VI) with the production of ammonium ions at concentrations the same times higher than those of Cr(III). It has been established that K2Cr2O7 inhibits biomass accumulation, nitrite ions’ reduction and ammonium ions’ production by bacteria after simultaneous addition into the medium of 3.47 mM NO2– and 1.74–10.41 mM Cr(VI) or 1.74–10.41 mM NO2– and 3.47 mM Cr(VI). In the medium with the same initial content of (3.47 mM) NO2– and Cr(VI) the reduction of Cr(VI) by bacteria was only slightly, up to 1.1 times, lower than the reduction of nitrite ions, almost the same concentrations of trivalent chromium and ammonium ions were detected in the cultural liquid. The processes of nitrate and nitride reduction carried out by bacteria of Desulfuromonas genus were revealed to be less sensitive to the negative influence of sodium dichromate, as compared with the process of sulfur reduction, because in the media with the same initial content (3.47 mM) of NO3– or NO2– and Cr(VI) bacteria produced 1.1–1.2 times more NH4+ than Cr(III), but in the medium with the same initial content (3.47 mM) of S0 and Cr(VI) ) bacteria produced over than three times more Cr(III) than hydrogen sulfide. Our data allow us to conclude that bacteria of Desulfuromonas genus, the investigated strains of which are adapted to high concentrations (up to 10.41 mM) of inorganic toxicants, play an important role in the geochemical cycles of sulfur, nitrogen and chromium in aquatic environments that have been under anthropogenic influence.

Removal of the Harmful Nitrate Anions from Potable Water Using Different Methods and Materials, including Zero-Valent Iron.

Drinking water containing nitrate ions at a higher concentration level of more than 10 mg/L, according to the World Health Organization (WHO), poses a considerable peril to humans. This danger lies in its reduction of nitrite ions. These ions cause methemoglobinemia during the oxidation of hemoglobin into methemoglobin. Many protocols can be applied to the remediation of nitrate ions from hydra solutions such as Zn metal and amino sulfonic acid. Furthermore, the electrochemical process is a potent protocol that is useful for this purpose. Designing varying parameters, such as the type of cathodic electrode (Sn, Al, Fe, Cu), the type of electrolyte, and its concentration, temperature, pH, and current density, can give the best conditions to eliminate the nitrate as a pollutant. Moreover, the use of accessible, functional, and inexpensive adsorbents such as granular ferric hydroxide, modified zeolite, rice chaff, chitosan, perlite, red mud, and activated carbon are considered a possible approach for nitrate removal. Additionally, biological denitrification is considered one of the most promising methodologies attributable to its outstanding performance. Among these powerful methods and materials exist zero-valent iron (ZVI), which is used effectively in the deletion process of nitrate ions. Non-precious synthesis pathways are utilized to reduce the Fe2+ or Fe3+ ions by borohydride to obtain ZVI. The structural and morphological characteristics of ZVI are elucidated using UV–Vis spectroscopy, zeta potential, XRD, FE-SEM, and TEM. The adsorptive properties are estimated through batch experiments, which are achieved to control the feasibility of ZVI as an adsorbent under the effects of Fe0 dose, concentration of NO3− ions, and pH. The obtained literature findings recommend that ZVI is an appropriate applicant adsorbent for the remediation of nitrate ions.

Dissimilatory reduction of sulfate, nitrate and nitrite ions by bacteria Desulfovibrio sp. under the influence of potassium dichromate

In the process of anaerobic respiration, sulfate reducing bacteria, besides sulfates, can use other electron acceptors: nitrates, nitrites, oxidized forms of heavy metals, in particular, hexavalent chromium, which are harmful for organisms. Selection of pollutant-resistant stains of this kind of bacteria isolated from technogenically altered ecotopes, capable of reductive transformation of various nature pollutants, is an especially relevant task for the creation of new effective remediation biotechnologies. The purpose of this work was to investigate the regularities of usage of sulfate, nitrate or nitrite ions by bacteria of the Desulfovibrio genus, isolated from Yavorivske Lake, at conditions of simultaneous presence in the medium of another electron acceptor – Cr(VI), to establish a succession of electron acceptors’ reduction by investigated sulfidogenic bacteria and to evaluate the efficiency of their possible application in technologies of complex purification of the environment from metal, sulfur and nitrogen compounds. Bacteria were grown under anaerobic conditions for 10 days in Kravtsov-Sorokin medium without Mohr’s salt. To study the efficiency of sulfate, nitrate, or nitrite ions’ reduction at simultaneous presence in the medium of Cr(VI), bacteria were sown in media with Na2SO4×10H2O, NaNO3, NaNO2 or K2Cr2O7 to final SO42–, NO3–, NO2– or Cr(VI) concentration in the medium of 3.47 (concentration of SO42– in medium of standard composition) or 1.74, 3.47, 5.21, 6.94, 10.41 mM. Biomass was determined turbidimetrically, and the concentrations of sulfate, nitrate, nitrite, ammonium ions, hydrogen sulfide, Cr(VI), Cr(ІІІ) in cultural liquid were determined by spectrophotometric method. It has been established that Cr(VI) inhibits the biomass accumulation, sulfate ions’ reduction and hydrogen sulfide production by Desulfovibrio sp. after simultaneous introduction into the medium of 3.47 mM SO42– and 1.74–10.41 mM Cr(VI). In the medium with the same initial content (3.47 mM) of SO42– and Cr(VI), bacteria reduced 2.1–2.3 times more Cr(VI) than sulfate ions with Cr(III) production at concentrations up to 2.2 times higher than hydrogen sulfide. It has been shown that K2Cr2O7 inhibits the biomass accumulation, the nitrate ions reduction and the ammonium ions production by bacteria after simultaneous addition into the medium of 3.47 mM NO3– and 1.74–10.41 mM Cr(VI) or 1.74–10.41 mM NO3– and 3.47 mM Cr(VI). In the medium with the same initial content (3.47 mM) of NO3– and Cr(VI) bacteria reduced 1.1–1.3 times more nitrate ions than Cr(VI) with the production of ammonium ions at concentrations up to 1.3 times higher than that of Cr(III). It has been established that K2Cr2O7 inhibits the biomass accumulation, the nitrite ions’ reduction and the ammonium ions’ production by bacteria after simultaneous addition into the medium of 3.47 mM NO2– and 1.74–10.41 mM Cr(VI) or 1.74–10.41 mM NO2– and 3.47 mM Cr(VI). In the medium with the same initial content (3.47 mM) NO2– and Cr(VI) the reduction of Cr(VI) by bacteria practically did not differ from the reduction of nitrite ions (was only slightly lower – up to 1.1 times), almost the same concentrations of trivalent chromium and ammonium ions in the cultural liquid were detected. The processes of nitrate and nitride reduction, carried out by bacteria of Desulfovibrio genus, were revealed to be less sensitive to the negative influence of sodium dichromate, as compared with the process of sulfate ions’ reduction, which in the medium with 3.47 mM SO42– and 1.74–10.41 mM Cr(VІ) decreased by 3.2–4.6 times as compared with this process in the medium with only Na2SO4×10H2O. The investigated strains of bacteria are adapted to high concentrations of toxic pollutants (up to 10.41 mM) and therefore are promising for application in technologies of complex environment purification from hexavalent chromium, sulfur and nitrogen compounds.

Fabrication and electrochemical study of K(1,1′- (1,4 Butanediyl)dipyridinium)2[PW11O39Co(H2O)]/MWCNTs-COOH nanohybrid immobilized on glassy carbon for electrocatalytic detection of nitrite

• Fabrication an electrochemical sensor based on (bdpy)PW 11 Co/MWCNTs-COOH. • (bdpy)PW 11 Co/MWCNTs-COOH/GCE showed excellent electrocatalysis towards NO 2 – . • (bdpy)PW 11 Co/MWCNTs-COOH/GCE exhibited good selectivity and stability. • The LOD of NO 2 – is about 0.63 µmol L −1 with sensitivity of 17.9 µA mM −1 . A nanocomposite modified glassy carbon electrode (GCE) based on K(1,1′-(1,4-Butanediyl) dipyridinium) 2 [PW 11 O 39 Co(H 2 O)]/carboxyl functionalized multi-walled Carbon Nanotubes ((bdpy)PW 11 Co/MWCNTs-COOH/GCE) was fabricated by electrodeposition method. TEM images demonstrated that ((bdpy)PW 11 Co nanoparticles were dispersed uniformly on the surfaces of MWCNTs-COOH or their interlayers with a diameter of 8.5 nm. The morphological, electrochemical, and electrocatalytic behaviors of the modified electrode were investigated by field emission scanning electron microscopy (FE-SEM) combined with energy-dispersive X-ray spectroscopy, cyclic voltammetry, and amperometry techniques. The FE-SEM images well showed immobilization of (bdpy)PW 11 Co/MWCNTs-COOH on GCE by deformation of the mirror surface to the rough surface. The electrochemical test results confirmed that (bdpy)PW 11 Co/MWCNTs-COOH/GCE has good stability and remarkable electrocatalytic behavior toward the reduction of nitrite ion. The proposed sensor displayed a linear range of 10–1600 µmol L −1 with LOD of 0.63 µmol L −1 (S/N = 3), and sensitivity 17.9 µA mM −1 . Moreover, the results of the electrochemical experiments indicated that this sensor has an excellent selectivity, good reproducibility, and repeatability, high stability, as well as analytical performance in real samples.

DEMS and RAMAN study of the monatomic hydrogen adsorption during electro-reduction of NO3- and NO2- at Pt nanoparticles supported at W18O49-ZrO2-C nanocomposite

A multifunctional hybrid material composed of W18O49 nanobelts (NBs), zirconium oxide, and Vulcan carbon (W18O49-ZrO2-C) has been used as support for platinum nanoparticles (PtWZC). For comparison, platinum supported on Vulcan carbon (PtC) was also synthesized. These catalysts were evaluated in the NO3- and NO2- (NOx) reduction reactions. The addition of W18O49 and ZrO2 to the carbon improved the size and distribution of the platinum nanoparticles. The electrochemical results showed that enhanced electrocatalytic activity for the NOx reduction was obtained on the PtWZC catalyst compared to PtC synthesized by the same technique and PtEtek from a commercial source. Our findings suggest that the adsorbed monatomic hydrogen (Hads) over platinum inhibits the reduction of nitrates and nitrites. Therefore, these reactions need a material that removes Hads from the surface or modifies it for the NOx reduction. The WZC support adsorbed monatomic hydrogen from water to form active bronze species (Hx-W18O49) that interacted with the NO3- and NO2- ions enabling their reduction, in accord with the results from in-situ Raman spectroscopy and Tafel slopes. N2, NO, NH3, and N2H4 products were detected in nitrite ion reduction by the Differential electrochemical mass spectrometry (DEMS) technique on the PtWZC catalyst. The production of N2 dominated in the cathodic and anodic scan. Hence, the novel catalyst can follow the indirect pathway, where the reduction process involves adsorption of NHx and adsorption of NO. The higher electrocatalytic activity obtained by the PtWZC catalyst was attributed to the uniform distribution of platinum on the support, the increased electrical conductivity produced by the W18O49 nanobelts, and the modulation of Hads on the surface.

Synthesis and investigation of two new crystalline organic inorganic nano-hybrids based on Wells-Dawson vanadotungstates and 1H-1, 2, 4-triazole as electro- and photocatalysts

Two new Wells–Dawson polyoxometalate-based organic-inorganic hybrid materials, namely, {[O]2.75[trz]7[α2-P2W17VO62]•12H2O}2(1) and {[O]11.5[trz]7[α2-P2W14.4V3.6O62]}2(2) (trz=1-H-1,2,4-triazole) were synthesized under mildconditions, and characterized by FT-IR, 1H NMR and 31P NMR spectroscopy, powder X-ray diffraction, TGA, field emission SEM and cyclic voltammetry. These hybrids constructed from trz ligand and Wells–Dawson polyoxoanions, in which trzis connected to a mono-vanadium substituted [α2-P2W17VO62]7− in 1 and a hexa-vanadium substituted [P2W12V6O62]12−in 2 by hydrogen bonding interactions. The structures of 1 and 2 were determined by single-crystal X-ray diffraction. Electrocatalytical activities of compounds 1 and 2 in the form of modified carbon paste electrode (MCPE) towards the reduction of nitrite ion have been studied in different pH values at acidic buffer solutions. Compounds 1-MCPE and 2-MCPE exhibit good electrocatalytical activity for reduction of NO2−. Also, the photocatalytical properties of the compounds 1 and 2 for the degradation of methylene blue have been studied.

A new Keggin-based organic-inorganic nanohybrid in the role of a dual-purpose catalyst

A new organic-inorganic hybrid consisting of Keggin-type polyoxometalate ([BW12O40]5−) and protonated piperazine, namely [H5O2]2[Hpip]2.5[BW12O40]·4H2O (pip = piperazine, C4H10N2) (1), has been created under reflux state and identified through material identification devices like single-crystal crystallography, FT-IR and 1H-NMR spectroscopies, Powder XRD, TG-DT Analysis, Field Emission SEM, elemental-analysis and cyclic voltammetry. Crystallography investigation exhibits that the main factor in the formation of 1 is the numerous number of hydrogen bonding between organic and inorganic species. The arrangement of Hpip groups creates holes in which the [BW12O40]5− clusters fit into the holes. Furthermore, the electrochemical and photochemical attributes of 1 have been considered, and the outcomes present that 1 owns privileged electrocatalytic activity against the reduction of nitrite ions as well as an appropriate photochemical effect on methylene blue (MB) dye depredation. A new organic-inorganic hybrid consisting of Keggin-type polyoxometalate ([BW12O40]5-) and protonated piperazine, namely [H5O2]2[Hpip]2.5[BW12O40]·4H2O (pip = piperazine, C4H10N2) (1), has been created under reflux state. The electrochemical and photochemical attributes of 1 have been considered, and the outcomes present that 1 owns privileged electrocatalytic activity against the reduction of nitrite ions as well as an appropriate photochemical effect on methylene blue (MB) dye depredation.

Reduction of sulfur and oxidized forms of nitrogen by bacteria of Desulfuromonas sp., isolated from Yavorivske Lake, under the influence of ferrum citrate

Technogenic reservoirs mainly contain several possible electron acceptors of anaerobic respiration, many of which are dangerous to the environment. The succession of their reduction (and thus detoxification) by sulfur reducing bacteria is not yet sufficiently studied. We investigated the influence of ferrum (III) citrate, present in the cultivation medium, on the reduction of sulfur, nitrate and nitrite ions by sulfur reducing bacteria Desulfuromonas acetoxidans IMV B-7384, Desulfuromonas sp. Yavor-5 and Desulfuromonas sp. Yavor-7, isolated from Yavorivske Lake. It was established that ferrum (III) citrate inhibits the biomass accumulation and hydrogen sulfide production by bacteria of Desulfuromonas sp. after simultaneous addition to the medium of 3.47 mM S0 and 1.74–10.41 mM ferrum (III) citrate, as compared with growth and hydrogen sulfide production by bacteria in the medium with only sulfur. In the medium with the same initial content (3.47 mM) S0 and ferrum (III) citrate bacteria produced ferrum (II) ions at concentrations 3.5–3.9 times higher than that of hydrogen sulfide. Ferrum (III) citrate inhibits the biomass accumulation, the nitrate or nitrite ions reduction and the ammonium ions production by bacteria of Desulfuromonas sp. after simultaneous addition to the medium of 3.47 mM NaNO3 or NaNO2 and 1.74–10.41 mM ferrum (III) citrate. In the medium with the same initial content (3.47 mM) NaNO3 and ferrum (III) citrate, bacteria produced ammonium ions at concentrations in 1.1 times higher than that of ferrum (II) ions. In the medium with the same initial content (3.47 mM) NaNO2 and ferrum (III) citrate, bacteria reduced 1.5–1.6 times more ferrum (III) than nitrite ions with production of ferrum (II) ions at concentrations 1.7 times higher than that of ammonium ions. The process of nitrate reduction carried out by bacteria of Desulfuromonas genus was less sensitive to the negative influence of ferrum (III) citrate, compared to the process of nitrite ions reduction. When the reduction of nitrate ions by bacteria in the presence of 1.74–10.41 mM ferrum (III) citrate decreased by 1.4–2.2 times, then the reduction of nitrite ions decreased by 1.8–3.2 times compared to their reduction in media with only NaNO3 or NaNO2, respectively. Although the reduction of ferrum (III) by cells in media with 3.47 mM S0, NaNO3 or NaNO2 and 1.74–10.41 mM ferrum (III) citrate decreased by 1.6–2.7, 1.6–2.7 and 1.1–2.2 times, respectively, compared to the reduction in medium with only ferrum (III) citrate, the investigated strains of bacteria were resistant to high concentrations of trivalent ferrum compounds and can therefore can be used in technologies of complex purification of environments polluted by heavy metal and nitrogen compounds.

A new organic-inorganic nano hybrid based on borotungstic anion and imidazole ring as a two-functional green catalyst

A new organic-inorganic hybrid consisting of Keggin-type polyoxometalate ([BW12O40]5-) and imidazole, namely [H5O2][imi]4 [BW12O40]·nH2O (imi = Imidazole) (1), has been created under reflux state and identified through material identification devices like single crystal crystallography, FT-IR and 1H NMR spectroscopies, powder XRD, TG-DT Analysis, field emission SEM, elemental-analysis and cyclic voltammetry. Crystallography investigation exhibits that two main factors which are the numerous number of hydrogen bonding between organic and inorganic species and π-π stacking interaction between two adjacent imidazole rings a have crucial role in 1 formation. In addition, three types of imidazole exist in 1 structure in terms of different kind of hydrogen bonding among [BW12O40]5- clusters and imidazole cations. Furthermore, the electrochemical and photochemical attributes of 1 have been considered, and the outcomes present that compound owns privileged electrocatalytic activity against the reduction of nitrite ions as well as an appropriate photochemical effect on methylene blue (MB) dye depredation. Because of the use of catalyst 1 in the form of modified carbon paste electrode (MCPE) to reduce nitrite ions, and of course its ability to recover and reuse repeatedly in the degradation of MB, this catalyst can be classified in green chemistry domain.

Nitrite Reduction Cycle on a Dinuclear Ruthenium Complex Producing Ammonia.

The fundamental biogeochemical cycle of nitrogen includes cytochrome c nitrite reductase, which catalyzes the reduction of nitrite ions to ammonium with eight protons and six electrons (NO2- + 8H+ + 6e- → NH4+ + 2H2O). This reaction has motivated researchers to explore the reduction of nitrite. Although a number of electrochemical reductions of NO2- have been reported, the synthetic nitrite reduction reaction remains limited. To the best of our knowledge, formation of ammonia has not been reported. We report a three-step nitrite reduction cycle on a dinuclear ruthenium platform {(TpRu)2(μ-pz)} (Tp = HB(pyrazol-1-yl)3), producing ammonia. The cycle comprises conversion of a nitrito ligand to a NO ligand using 2H+ and e-, subsequent reduction of the NO ligand to a nitrido and a H2O ligand by consumption of 2H+ and 5e-, and recovery of the parent nitrito ligand. Moreover, release of ammonia was detected.

Electrochemical Chelation and Reduction of Nitrate Ion on EDTA Modified Carbon Paste Electrode

The aim of this work is to combine two methods for removing nitrate ions from concentrated aqueous solutions. This involves chelating and then reducing NO3- by EDTE modified carbon paste electrode (EDTA-CPE). We find that in the absence of EDTA on the carbon paste electrode surface, the nitrate reduction is almost impossible. The reduction of nitrate ions was invested on the surface of the EDTA-CPE, the cyclic voltammograms recorded in electrolytic medium 0.1 M KCl, shows two reduction peaks, the first at -0.2 V, attributed to the reduction of nitrite ions (NO2-) and the second one at 0.8 V which corresponds to the reduction of nitrate to nitrite ions.

Portable Nitric Oxide (NO) Generator Based on Electrochemical Reduction of Nitrite for Potential Applications in Inhaled NO Therapy and Cardiopulmonary Bypass Surgery.

A new portable gas phase nitric oxide (NO) generator is described for potential applications in inhaled NO (INO) therapy and during cardiopulmonary bypass (CPB) surgery. In this system, NO is produced at the surface of a large-area mesh working electrode by electrochemical reduction of nitrite ions in the presence of a soluble copper(II)-ligand electron transfer mediator complex. The NO generated is then transported into gas phase by either direct purging with nitrogen/air or via circulating the electrolyte/nitrite solution through a gas extraction silicone fiber-based membrane-dialyzer assembly. Gas phase NO concentrations can be tuned in the range of 5-1000 ppm (parts per million by volume for gaseous species), in proportion to a constant cathodic current applied between the working and counter electrodes. This new NO generation process has the advantages of rapid production times (5 min to steady-state), high Faraday NO production efficiency (ca. 93%), excellent stability, and very low cost when using air as the carrier gas for NO (in the membrane dialyzer configuration), enabling the development of potentially portable INO devices. In this initial work, the new system is examined for the effectiveness of gaseous NO to reduce the systemic inflammatory response (SIR) during CPB, where 500 ppm of NO added to the sweep gas of the oxygenator or to the cardiotomy suction air in a CPB system is shown to prevent activation of white blood cells (granulocytes and monocytes) during extracorporeal circulation with cardiotomy suction conducted with five pigs.

Green synthesis of silver nanoparticles using water extract of Salvia leriifolia: Antibacterial studies and applications as catalysts in the electrochemical detection of nitrite

Here, a green method is described for the biosynthesis of Ag nanoparticles (Ag NPs) using aqueous extracts of the leaf of Salvia leriifolia as reducing and stabilizing agent. Various techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were employed for the characterization of the structure and morphology of bio‐synthesized AgNPs. The results reveal that AgNPs synthesized with uniform spherical morphology and average diameters of 27 nm. The AgNPs as a green and efficient heterogeneous catalyst presented superior antibacterial activity. Direct electrochemistry studies of the synthesized AgNPs confirmed that nanoparticles retained their direct electrochemical activity. This is mainly attributed to the proper biosynthesis process, the large specific surface area and the good conductivity of the synthesized nanoparticles. Hence, the present synthesized AgNPs displayed good electrocatalytic activity to the reduction of nitrite ions. The proposed method is highly recommended as a novel platform for the development of electrochemical sensors which can further expand the applications of AgNPs. Antibacterial activity of the synthesized AgNPs was evaluated against nine microorganisms. AgNPs prevented the growth of all selected bacteria. The nanoparticles inhibited the growth of Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus coagulase, Acinetobacter baumannii, and Streptococcus pneumonia more than antibiotic of vancomycin, however, the ability of AgNPs against Echerishia coli and Serratia marcescens was less than the antibiotic. On the other hand AgNPs were active against Citrobacter frurdii, while the antibiotic was inactive.

Polyoxometalate [PMo11O39]7−/carbon nanocomposites for sensitive amperometric detection of nitrite

The polyoxometalate [PMo11O39]7− was synthesized and used as catalyst for the reduction of nitrite ions. This mono-lacunary keggin anion, cited as PMo11, was confined within a matrix of either oxidized single-walled carbon nanotubes (ox-SWCNTs) or reduced graphene oxide (rGO) on glassy carbon (GC) electrodes to improve the electron transfers. Five different configurations were characterized using cyclic voltammetry and evaluated in an amperometric sensor setup for nitrite detection where the amount of the different components were optimized. The configuration using only ox-SWCNTs and PMo11 on GCE showed best sensitivities of up to 44.41mALmol−1 and a satisfying reproducibility (RSD: ∼2.64% for four identic electrodes). Furthermore, a linear range between 3.0×10−5molL−1 and 1.6×10−2molL−1 with a detection limit of 3.0×10−5molL−1 was obtained. The final sensor setup also showed good selectivity towards interfering ions.

N-Shaped Negative Differential Resistance in Nitrate Reduction Reactions on Cu Electrode

Nitrate ions, NO3 -, cause environmental problems such as water pollution and health problems including cancer and diabetes. The removal of nitrate ions from water by electrochemical reactions has been researched for many years, because the electrochemical treatment, which does not require any chemicals, is an environmentally friendly method of removing the nitrate ions from water. Thus, the electrochemical reduction of NO3 - has been extensively studied as summarized in literatures [1, 2]. The studies have revealed that Cu is an excellent catalyst for the electrochemical reduction [2]. We have reported [3, 4] that the nitrate reduction on Cu exhibits three types of electrochemical oscillations, named oscillations I, II and III, both under potential and current controlled conditions and also that the oscillations are accompanied by the hydrogen evolution reaction (HER). As can be seen in Figure 1 (which shows the current (I) – potential (E) curves for a Cu-wire electrode), which oscillation appeared depended on the solution acidity: oscillation I appeared when the nitrate reduction occurred in acidic solutions (panels a and b), oscillation II appeared independently of the solution acidity (a, b, and d), and oscillation III appeared when the solution was basic (c and d). It is well accepted that N-shaped negative differential resistance (N-NDR) plays an important role in most of electrochemical oscillations. This is because an N-NDR causes a positive feedback mechanism that is essential for the appearance of an electrochemical oscillation. The nitrate reduction was thought to be suprressed by adsorbed hydrogen atoms on Cu surface, i.e., by the reaction intermediates for the HER, and thus the N-NDR that induced oscillation I was ascribed to the suppression of the nitrate reduction [3]. On the other hand, although an N-NDR was observed at aroud -1.4 V for basic solutions (panel c), i.e., at potentials within the potential range of oscillation II (compare panel c with d), the factor causing the N-NDR was not identified. Recently, in order to identify the factor, we studied the reduction of nitrite ions, NO2 -, in basic solutions. Similarly to the nitrate reduction, an N-NDR was observed under potential controlled conditions (panel e) and an oscillation appeared under current controlled conditions (f). The oscillation was identified as oscillation II because it had the typical feature of oscillation II: the electrode potential oscillated synchronousely with the behavior of hydrogen bubble evolution. Thus, the appearance of oscillation II was thought to be independent of the kind of reactive species, which led to the conclusion that the bubble evolution played an essential role in oscillation II. In this presentation, we will show how and why the bubble evolution induces the N-NDR that causes oscillation II, and also discuss the mechasnim of oscillation II. REFERENCES [1] C. Milhano and D. Pletcher, in Modern Aspects of Electrochemistry 45, R. E. White, Editor, p. 1, Springer, New York (2009). [2] V. Rosca, M. Duca, M. T. de Groot and M. T. M. Koper, Chem. Rev. 109, 2209 (2009). [3] Y. Mukouyama, S. Yamamoto, R. Nakazato, S. Nakanishi and H. Okamoto, ECS Trans., 50 (48) 61-70, (2013). [4] Y. Mukouyama, S. Yamamoto, S. Nakanishi and H. Okamoto, ECS Trans., 58 (25) 85-97, (2014). FIGURE CAPTION Figure 1. The I – E curves for (a, b) 0.1 M H2SO4 + 0.1 M KNO3, (c, d) 0.2 M NaOH + 0.2 M KNO3, and (e, f) 0.2 M NaOH + 0.2 M NaNO2, measured (left) under potential controlled conditions and (right) under current controlled conditions. Figure 1

Electrochemically Modulated Nitric Oxide Release From Flexible Silicone Rubber Patch: Antimicrobial Activity For Potential Wound Healing Applications.

Herein, we report a novel design and the antimicrobial efficacy of a flexible nitric oxide (NO) releasing patch for potential wound healing applications. The compact sized polydimethylsiloxane (PDMS) planar patch generates NO via electrochemical reduction of nitrite ions mediated by a copper(II)-ligand catalyst using a portable power system and an internal gold coated stainless steel mesh working electrode. Patches are fabricated via soft lithography and 3-D printing. The devices can continuously release NO over 4 days and exhibit potent bactericidal effects on both Escherichia coli and Staphylococcus aureus. The device may provide an effective, safe, and less costly alternative for treating chronic wounds.

Electrochemistry Investigation of the Monolacunary and Their Transition Metal Substituent Keggin-Type Polyoxometalates

The electrochemical and electrocatalytic behaviors of [XW11O39] n− and [XW11M(H2O)O39] m− (X = B, Si, and P; MII = Mn, Co, and Ni) polyoxometalates were studied with specific emphasis on the tungsten centers by cyclic voltammetry in aqueous solution. Electrochemical studies show the two or three stepwise cathodic/anodic peaks corresponding to the redox processes of WVI centers. The reversibility of redox peaks increases for [SiW11M(H2O)O39]6− and [PW11M(H2O)O39]5− polyoxometalates; however, that of [BW11M(H2O)O39]7− maintains quasi-reversible. The redox waves of the W-O framework for all polyoxometalates are pH- and scan rate-dependent. The tungsten-centered waves for these compound show a classical potential shift as a function of acidity at pH = 2.2–4.2. The electrocatalysis behaviors of these compounds toward the reduction of nitrite ions have been studied in details. The plots of catalytic efficiency versus γ for [XW11O39] n− and [XW11M(H2O)O39] m− (X = B, Si, P; MII = Mn, Co, Ni) show the catalytic efficiency of [BW11O39]9− and [BW11M(H2O)O39]7− (M = Mn, Co, Ni) more than that of the other compounds which are mentioned in this article.

Improved in vivo performance of amperometric oxygen (PO2) sensing catheters via electrochemical nitric oxide generation/release.

A novel electrochemically controlled release method for nitric oxide (NO) (based on electrochemical reduction of nitrite ions) is combined with an amperometric oxygen sensor within a dual lumen catheter configuration for the continuous in vivo sensing of the partial pressure of oxygen (PO2) in blood. The on-demand electrochemical NO generation/release method is shown to be fully compatible with amperometric PO2 sensing. The performance of the sensors is evaluated in rabbit veins and pig arteries for 7 and 21 h, respectively. Overall, the NO releasing sensors measure both venous and arterial PO2 values more accurately with an average deviation of −2 ± 11% and good correlation (R2 = 0.97) with in vitro blood measurements, whereas the corresponding control sensors without NO release show an average deviation of −31 ± 28% and poor correlation (R2 = 0.43) at time points >4 h after implantation in veins and >6 h in arteries. The NO releasing sensors induce less thrombus formation on the catheter surface in both veins and arteries (p < 0.05). This electrochemical NO generation/release method could offer a new and attractive means to improve the biocompatibility and performance of implantable chemical sensors.