Direct electrochemistry of nanoparticulate Fe2O3 in aqueous solution and adsorbed onto tin-doped indium oxide

Nanoparticulate iron oxides occur naturally, for example, in soil, water, and in the cytoplasm of living cells. The redox properties and detection of these nanoparticles are therefore of considerable importance. Understanding and mimicking nanoparticle-based redox reactions may lead to new types of water-based electrochemical processes. In this study, the electrochemical detection of 45 nm diameter Fe2O3 nanoparticles dissolved in aqueous buffer solutions is investigated as a model system. Voltammetric experiments with nanoparticulate Fe2O3 are reported based on two complementary approaches: (i) Fe2O3 nanoparticles adsorbed onto tin-doped indium oxide (ITO) electrodes are shown to give well-defined voltammetric reduction responses and (ii) hydrodynamic voltammety in the presence of fast (24 kHz ultrasound-enhanced) mass transport is shown to allow the direct detection of Fe2O3 nanoparticles in solution. Both the adhesion and the electrochemical reactivity of Fe2O3 nanoparticles at ITO electrode surfaces are strongly affected by the solution composition and the pH.

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Physiochemical Properties of PANI Thin Films

Advances in Chemical and Materials Engineering - Properties, Techniques, and Applications of Polyaniline (PANI) Thin Films ◽

10.4018/978-1-5225-9896-1.ch004 ◽

2020 ◽

pp. 93-137

Keyword(s):

Thin Films ◽

Antioxidant Properties ◽

Redox Properties ◽

Environmental Stability ◽

Physiochemical Properties ◽

Electrochemical Processes ◽

Capacitive Properties ◽

Electrical And Dielectric Properties ◽

Crystalline Nature ◽

High Degree

Good environmental stability, a high degree of processability, and interesting redox properties associated with its chain heteroatom due to this polyaniline (PANI) have been one of the most extensively studied conducting polymers from the last few years. The chemical and electrochemical processes can be used to synthesize PANI. This chapter mainly focused on physiochemical properties of PANI thin films such as conducting properties, optical properties, magnetic properties, electrical and dielectric properties, mechanical properties, crystalline nature, capacitive properties, sensing properties, charge-discharge properties, thermoelectric properties, redox properties, antioxidant properties, anticorrosion properties, etc.

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The Microbiota–Gut–Brain Axis Heart Shunt Part I: The French Paradox, Heart Disease and the Microbiota

Microorganisms ◽

10.3390/microorganisms8040490 ◽

2020 ◽

Vol 8 (4) ◽

pp. 490 ◽

Cited By ~ 1

Author(s):

Mark Obrenovich ◽

Bushra Siddiqui ◽

Benjamin McCloskey ◽

V. Prakash Reddy

Keyword(s):

Heart Disease ◽

Neurodegenerative Diseases ◽

Redox Reactions ◽

Close Association ◽

Cerebrovascular Diseases ◽

Mechanisms Of Action ◽

Whole Grains ◽

Redox Properties ◽

Health Promoting ◽

French Paradox

It has been well established that a vegetarian and polyphenol-rich diet, including fruits, vegetables, teas, juices, wine, indigestible fiber and whole grains, provide health-promoting phytochemicals and phytonutrients that are beneficial for the heart and brain. What is not well-characterized is the affect these foods have when co-metabolized within our dynamic gut and its colonizing flora. The concept of a heart shunt within the microbiota-gut-brain axis underscores the close association between brain and heart health and the so-called “French paradox” offers clues for understanding neurodegenerative and cerebrovascular diseases. Moreover, oxidation-redox reactions and redox properties of so-called brain and heart-protective foods are underappreciated as to their enhanced or deleterious mechanisms of action. Focusing on prodromal stages, and common mechanisms underlying heart, cerebrovascular and neurodegenerative diseases, we may unmask and understanding the means to better treat these related diseases.

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A Critical Evaluation of the Redox Properties of Uranium, Neptunium and Plutonium Ions in Acidic Aqueous Solutions

Pure and Applied Chemistry ◽

10.1351/pac199971091771 ◽

1999 ◽

Vol 71 (9) ◽

pp. 1771-1807 ◽

Cited By ~ 37

Author(s):

Sorin Kihara ◽

Zenko Yoshida ◽

Hisao Aoyagi ◽

Kohji Maeda ◽

Osamu Shirai ◽

...

Keyword(s):

Aqueous Solutions ◽

Redox Reactions ◽

Critical Evaluation ◽

Redox Properties ◽

Redox Processes ◽

Redox Potentials ◽

Electrode Processes ◽

Reversible Redox ◽

Reduction Mechanisms ◽

Current Potential

Standard redox potentials, E0s, and redox processes of U, Np and Pu ions in acidic aqueous solutions are reviewed and evaluated critically. The E0sof reversible redox processes, MO22+/MO2+ and M4+/M3+ (M: U, Np or Pu) adopted are those proposed mainly by Riglet et al. on the basis of the precise correction of formal potentials, E0's, according to the improved theoretical approach to estimate the activity coefficient. Electrode processes of the U, Np and Pu ions are discussed in terms of current-potential curves, measured so far by polarography, voltammetry or flow coulometry. Special attention is payed to the irreversible MO2+/M4+ reactions. Disproportionation reactions of MO2+ are also discussed. New substances are introduced as intermediates during reductions of MO2+ to M4+ or disproportionations of MO2+.CONTENTSIntroductionStandard redox potentials for uranium, neptunium and plutonium ions in acidic aqueous solutions2.1 Evaluation of E0 from E0' determined by electrochemical measurements2.2 Temperature dependence of E0Redox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by polarography or voltammetry3.1 Uranium3.2 Neptunium3.3 Plutonium3.4 Disproportionation of NpO2+, PuO2+, Np4+ and Pu4+3.5 Reduction of MO2+ and reduction intermediatesRedox reactions of uranium, neptunium and plutonium in acidic aqueous solutions investigated by flow coulometry4.1 Electrode processes of the uranium, neptunium and plutonium ions investigated by flow coulometry at the column electrode at the column electrode4.2 Disproportionation of MO2+ during the electrolysis by flow coulometry4.3 Reduction mechanisms of MO2+ (M = Np or Pu) and reduction intermediates investigated by flow coulometryConclusionsList of abbreviationsAppendixReferences

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The effect of pH and complexation on redox reactions between RS• radicals and flavins

Canadian Journal of Chemistry ◽

10.1139/v84-035 ◽

1984 ◽

Vol 62 (1) ◽

pp. 171-177 ◽

Cited By ~ 23

Author(s):

Rizwan Ahmad ◽

David A. Armstrong

Keyword(s):

Redox Potential ◽

Linear Function ◽

Redox Reactions ◽

Flavin Adenine Dinucleotide ◽

Protonated Form ◽

Redox Properties ◽

The Other ◽

Effect Of Ph ◽

Other Hand ◽

High Redox Potential

Elementary considerations indicate that thiol radicals, RS•, should have a high redox potential [Formula: see text][Formula: see text]However, the equilibrium [4],[Formula: see text]which is established in the presence of excess RS−, would convert RS•to [Formula: see text] which is a reducing species. Experimentally it was demonstrated that thiol radicals made by γ radiolysis of β-mercaptoethanol solutions effected two-electron oxidation of dihydroflavin FlH2 at pH 6.3 and of FlH− at pH 8. On the other hand, [Formula: see text] readily reduced Fl to FlH2 or FlH− as expected. At pH 9, photostationary states were established after a few minutes radiolysis and the ratios [FlH−]ss/[Fl]ss were a function of [Formula: see text] The main reactions occurring were:[Formula: see text]The values of k19 and k22 were both large. The ratio k19/k22 was ∼0.8 for lumiflavin and ∼0.3 for flavin adenine dinucleotide. The cyclic disulphide anions of lipoamide and dithiothreitol [Formula: see text] also effected two-electron reductions of flavins. However, the protonated form of [Formula: see text] oxidized FlH2, and the photostationary ratio [FlH−]ss/[Fl]ss was an approximate linear function of [Formula: see text]. The implications of the observed changes in redox properties of sulphur radicals on complexation with RS− and protonation were briefly considered.Des considérations élémentaires indiquent que les radicaux thiyles, RS•, doivent avoir un potentiel rédox élevé [Formula: see text][Formula: see text]

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Use of ‘solid-state’ promoters in the electrochemistry of cytochrome c at a gold electrode

Biochemical Journal ◽

10.1042/bj2730783 ◽

1991 ◽

Vol 273 (3) ◽

pp. 783-786 ◽

Cited By ~ 31

Author(s):

R Santucci ◽

A Faraoni ◽

L Campanella ◽

G Tranchida ◽

M Brunori

Keyword(s):

Cyclic Voltammetry ◽

Solid State ◽

Cytochrome C ◽

Gold Electrode ◽

Direct Electrochemistry ◽

Protoporphyrin Ix ◽

Cellulose Triacetate ◽

Electrode Surfaces ◽

Inert Electrode ◽

Hydrolysis Of

The direct electrochemistry of cytochrome c at a gold electrode was investigated by cyclic voltammetry using, as promoters, microperoxidase (the haem-undecapeptide obtained by hydrolysis of cytochrome c), Fe(III)-protoporphyrin IX or protoporphyrin-IX, all entrapped in a cellulose triacetate membrane. The results indicate that these immobilized systems strongly enhance the rate of electron transfer between the protein in solution and the electrode surface, and thus behave as ‘solid-state’ promoters, though with differing efficiencies. These results are of interest because they raise the possibility of engineering an efficient and versatile promoter active also at inert electrode surfaces.

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In Situ Determination of pH at Nanostructured Carbon Electrodes Using IR Spectroscopy

Materials ◽

10.3390/ma12244044 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4044

Author(s):

Lolade Bamgbelu ◽

Katherine B Holt

Keyword(s):

Ir Spectroscopy ◽

Redox Reactions ◽

Ph Change ◽

Ph Changes ◽

Electrode Surfaces ◽

Phosphate Ions ◽

Phosphate Species ◽

Analytical Importance ◽

Electrode Interface

Changes in pH at electrode surfaces can occur when redox reactions involving the production or consumption of protons take place. Many redox reactions of biological or analytical importance are proton-coupled, resulting in localized interfacial pH changes as the reaction proceeds. Other important electrochemical reactions, such as hydrogen and oxygen evolution reactions, can likewise result in pH changes near the electrode. However, it is very difficult to measure pH changes located within around 100 µm of the electrode surface. This paper describes the use of in situ attenuated total reflectance (ATR) infrared (IR) spectroscopy to determine the pH of different solutions directly at the electrode interface, while a potential is applied. Changes in the distinctive IR bands of solution phosphate species are used as an indicator of pH change, given that the protonation state of the phosphate ions is pH-dependent. We found that the pH at the surface of an electrode modified with carbon nanotubes can increase from 4.5 to 11 during the hydrogen evolution reaction, even in buffered solutions. The local pH change accompanying the hydroquinone–quinone redox reaction is also determined.

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Gold and Nanostructurated Surfaces for Assembling of Electrochemical Biosensors

Research Letters in Nanotechnology ◽

10.1155/2008/789153 ◽

2008 ◽

Vol 2008 ◽

pp. 1-4 ◽

Cited By ~ 1

Author(s):

Antonella Curulli ◽

Daniela Zane

Keyword(s):

Glucose Oxidase ◽

Direct Detection ◽

Direct Electrochemistry ◽

Chemical Species ◽

Electrochemical Biosensors ◽

Gold Nanowires ◽

Nanostructured Surfaces ◽

Full Characterization ◽

Si Substrates ◽

Enzyme Molecules

Devices based on nanomaterials are emerging as a powerful and general class of ultrasensitive sensors for the direct detection of biological and chemical species. In this work, we report the preparation and the full characterization of nanomaterials such as gold nanowires and nanostructured films to be used for assembling of electrochemical biosensors. Gold nanowires were prepared by electroless deposition within the pores of polycarbonate particle track-etched membranes (PTMs). Glucose oxidase was deposited onto the nanowires using self-assembling monolayer as an anchor layer for the enzyme molecules. Finally, cyclic voltammetry was performed for different enzymes to test the applicability of gold nanowires as biosensors. Considering another interesting nanomaterial, the realization of functionalised thin films on Si substrates for the immobilization of enzymes is reported. Glucose oxidase and horseradish peroxidase immobilized onto -based nanostructured surfaces exhibited a pair of well-defined and quasireversible voltammetric peaks. The electron exchange between the enzyme and the electrodes was greatly enhanced in the nanostructured environment. The electrocatalytic activity of HRP and GOD embedded in electrodes toward and glucose, respectively, may have a potential perspective in the fabrication of third-generation biosensors based on direct electrochemistry of enzymes.

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