Characterization of Fe implanted yttria-stabilized zirconia by cyclic voltammetry

The technique of cyclic voltammetry has been applied to study reduction and oxidation phenomena which are observed at low oxygen partial pressures during steady state current-overpotential measurements of the Au, O2(g)/Fe implanted yttria-stabilized zirconia interface. The redox potential (EO) of the observed redox couple is in close agreement with the thermodynamic potential of coexistent Fe2O3 and Fe3O4 phases. Hence in the forward sweep of the cyclic voltammogram, defined for negatively swept potential, part of the Fe3+ is reduced to Fe2+. The peak currents in the voltammogram result from a redox reaction which is rate limited by the diffusion of electrons or electron holes in the Fe implanted YSZ surface to the implanted Fe ions rather than by the diffusion of the Fe ions themselves

On the use of electrochemical techniques to monitor free oxide content in molten fluoride media

The electrochemical behaviour of oxide ions has been studied in fluoride melts(LiF/NaF eutectic) by cyclic voltammetry, square wave voltammetry and chronopotentiometry. The purpose is to determine whether these techniques can be used for titration of free oxide ions (O2-) in molten fluorides released by lithium oxide additions. Cyclic voltammetry is shown to be unsuitable for this purpose due to oxygen bubbling disturbing the oxidation peak, while square wave voltammetry is far more appropriate because the observed signal is a well defined oxidation peak with a height proportional to the oxide content. Thus, the present work is focused on a strategy of oxide ions titration by square wave voltammetry. In addition, this work allows assessing that the electrochemical reduction of oxide ions proceeds by diffusion of these species, and the O2- diffusion coefficient is estimated by chronopotentiometry

Electrochemical monitoring of the storage or stabilization of archaeological copper based artefacts in sodium sesquicarbonate solutions

Archaeological copper-based artifacts recovered from wet and salty environments are often stored or stabilized in sodium sesquicarbonate solutions. Modification of the natural patina and development of active corrosion can occur during these processes, which implies the need for monitoring storage/stabilization processes. The focus of the study consists of examining how corrosion potential (Ecorr) measurements and voltammetric curves can contribute in providing information on the effectiveness of storage and stabilization treatments. Particular attention is given to side effects such as the transformation of the corrosion layers

Co-reduction of aluminium and lanthanide ions in molten fluorides : application to cerium and samarium extraction from nuclear waste

This work concerns the method of co-reduction process with aluminium ions in LiF–CaF2 medium (79–21 mol.%) on tungsten electrode for cerium and samarium extraction. Electrochemical techniques such as cyclic and square wave voltammetries, and potentiostatic electrolyses were used to study the co-reduction of CeF3 and SmF3 with AlF3. For each of these elements, specific peaks of Al–Ce and Al–Sm alloys formationwere observed by voltammetry aswell as peaks of pure cerium and aluminium, and pure samarium and aluminium respectively. The difference of potential measured between the solvent reduction and the alloy formation suggests expecting an extraction efficiency of 99.99% of each lanthanide by the process. Different intermetallic compounds were obtained for different potentiostatic electrolysis and were characterised by Scanning Electron Microscopy with EDS probe. The validity of the process was verified by carrying out cerium and samarium extractions in the form of Al–Ln alloy; the extraction efficiency was 99.5% for Ce(III) and 99.4% for Sm(III)

Active Carboxylic Acid-Terminated Alkanethiol Self-Assembled Monolayers on Gold Bead Electrodes for Immobilization of Cytochromes c

It is extremely difficult to immobilize cytochrome c (cyt c) on carboxylic acid-terminated alkanethiol self-assembled monolayers (HOOC-SAM) on gold bead electrodes prepared in a hydrogen flame. We found that simple pretreatment of a HOOC-SAM/gold bead electrode by potential cycling in buffer solution in the range ±300 mV prior to immobilization of the protein facilitated stable cyt c binding to HOOC-SAMs. The stability of cyt c on the HOOC-SAMs is independent of the topology of the gold surface

An Overview of Carbon Fiber Electrodes Used in Neurochemical Monitoring

Neurochemistry has always been a topic that many scientists are interested in researching because the brain is such a fascinating and complex organ. Electrochemical methods have proven to be a successful tool for scientists to use for their brain-researching endeavors. Many types of probes and analytical devices have been invented and used in conjunction with electrochemical methods over the past several decades to investigate the inner workings of the brain. In particular, the carbon fiber electrode has become a popular device among scientists due to its favorable qualities.The carbon fiber electrode has several unique characteristics to give it an advantage over other techniques. Carbon fiber electrodes have the ability to monitor in a subsecond time frame and record in real time. Because they are so small, carbon fiber electrodes are also able to sample very small environments, such as a single cell or vesicular volumes, where other devices cannot because they are too big. Evidence has shown that carbon fiber electrodes appear to cause less disruptive tissue damage when implanted into a brain than other devices, for instance a microdialysis probe. On top of that, carbon fiber electrodes are also excellent devices for those seeking greater sensitivity and selectivity by making electrode modifications tailored for the analyte of interest. In addition, carbon fiber electrodes provide a wider range of detectable species, again by simply making slight modifications. One can clearly see that the future for neurochemical monitoring lies heavily in the hands of the carbon fiber electrode. Its advantages over other devices make it superior in many aspects. Researchers will no doubt continue to use the carbon fiber electrode and keep improving it to make it suitable for countless more experiments

Electrostatic Binding of Metal Complexes to Electrode Surfaces Coated with Highly Charged Polymeric Films

Previous reports in which metal complexes have been attached to electrode surfaces coated with polymeric molecules have depended upon the formation of covalent or coordination bonds in the attachment procedure (1-4). Such schemes can be quite successful but depending, as they do, on rather specific surface chemistry, they are not applicable to as wide a variety of metal complexes as might be desirable. We have observed that coating graphite electrodes with polymers bearing charged ionic groups produces surfaces which strongly bind multiply-charged metal complexes bearing charges opposite to that on the attached ionic polymer. By exploiting this observation it is entirely possible that virtually any desired metal ion can be attached in large quantities to electrode surfaces by coordinating the metal ion with ligands that produce a multiply-charged complex ion

Voltammetric determination of the critical micellar concentration of surfactants by using a boron doped diamond anode

The electrochemistry of three surfactants has been studied by voltammetry at boron doped diamond (BDD) electrode in sodium sulphate solutions. The electrochemical behaviour of these surfactants is characterized by an oxidation signal (peak or wave) situated before the electrolyte oxidation. The anodic current is found to follow a linear relation with the concentration of the surfactants; the slope decreases abruptly above the critical micellar concentration (CMC) of the surfactants. The CMC values obtained for an anionic (sodium dodecylbenzenesulfonate, SDBS), a cationic (polyoxyethylene-23-dodecyl ether, BRIJ 35) and a neutral (1-(hexadecyl)trimethylammonium bromide, CTAB) surfactant are found in good agreement with those measured by the classical technique of surface tension. This voltammetric method has the advantage not to require the use of a redox active electrochemical probe

Synthetic and natural iron oxide characterization through microparticle voltammetry

Se presentan los resultados de un estudio sobre el uso de la Voltametría de Micropartículas (VMP), aplicada a la identificación de óxidos y oxihidróxidos de hierro. Mediante esta técnica, fue posible diferenciar hematita, goethita, magnetita y maghemita, en muestras sintéticas y naturales. La medición de pigmentos sintéticos tratados a diferentes temperaturas, evidenció la existencia de un patrón de comportamiento que permite diferenciarlos. Se constató que la ubicación del pico de corriente (valor de potencial), varía en función de la especie mineral, el tamaño de grano y el grado de cristalinidad, el área, en relación con la concentración de especie electroactiva y el ancho, con la distribución de tamaños de partícula. En muestras con elevadas concentraciones de óxidos y oxihidróxidos de hierro, los picos se definieron a corrientes del orden de los mA (miliamperes) y en muestras de paleosuelos con un contenido de hierro total inferior al 6%, los picos se registraron a corrientes del orden de los µA (microamperes). De esta manera, se constata la posibilidad de aplicación de la técnica en estudios ambientales y paleoambientales que tengan en cuenta a estos minerales. Las principales ventajas de la VMP, respecto a los métodos convencionales, se refieren a la rapidez y simplicidad de aplicación y a la posibilidad de procesar pocos microgramos de muestra, sin limitación de su grado de cristalinidad. A diferencia de los métodos magnéticos, fuertemente condicionados por la presencia de magnetita, la VMP resulta altamente sensible a la detección de especies débilmente magnéticas.We are hereby presenting the results obtained from a study on using Microparticle Voltammetry (MPV) for identifying Iron oxides and oxy–hydroxides. This technique allowed us to distinguish different mineral species, such as hematite, goethite, magnetite and maghemite, in both synthetic and natural samples. By measuring synthetic pigments at different temperatures, evidence was found of an electrochemical behavioral pattern which allowed differenciating them. The current peak location (potential value) proved to vary according to the mineral species, grain size and chrystallinity degree. The area varies in terms of electroactive concentration of the species given. Width varies according to particle size distribution. In high iron oxide and oxy–hydroxide concentration samples, peaks were defined at current values of mA (milliampers) and in paleosol samples having an overall iron content lower than 6%, peaks were recorded at currents of µA (microampers). Therefore, a possibility arises of applying this technique to environmental and palaeo–environmental studies of these minerals. MPVs main advantages compared to conventional methods are speed and simplicity as well as the fact that it allows processing a few sample grains, in spite of its chrystallinity degree. Unlike magnetic methods – strongly influenced by the presence of magnetite– MPV is highly sensitive for detecting weakly magnetic species.Fil: Rico, Yamile. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica; ArgentinaFil: Bidegain, Juan Carlos. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica; ArgentinaFil: Elsner, Cecilia Ines. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; Argentin