Sophie Peulon

Bio: Sophie Peulon is an academic researcher from University of Évry Val d'Essonne. The author has contributed to research in topics: Birnessite & Thin layers. The author has an hindex of 15, co-authored 28 publications receiving 1540 citations. Previous affiliations of Sophie Peulon include University of Western Brittany & Centre national de la recherche scientifique.

Mechanistic Study of Cathodic Electrodeposition of Zinc Oxide and Zinc Hydroxychloride Films from Oxygenated Aqueous Zinc Chloride Solutions

Abstract: Films of zinc oxide and related compounds [ZnO, ZnO x (OH) y , Zn(OH) x Cl y ] are electrodeposited cathodically in aqueous zinc chloride solutions using dissolved oxygen as a precursor. The influence of the precursor concentrations, pH, and deposition temperature on the growth, composition, and properties of the films are investigated by means of in situ techniques : voltammetry, electrochemical quartz-crystal microgravimetry, surface pH, and ex situ techniques: X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. The deposition mechanism is analyzed in terms of electrochemically induced surface precipitation due to an increase of local pH resulting from the oxygen reduction reaction. This approach allows us to explain the formation of either zinc hydroxychloride compounds or zinc oxide from their calculated solubility diagrams. In conditions of the formation of ZnO, a dramatic effect of temperature is observed, with a transition between amorphous insulating zinc oxyhydroxide to well-crystallized and conducting zinc oxide when the temperature increases (T transition 50 °C).

Studies of N-demethylation oxidative and degradation of methylene blue by thin layers of birnessite electrodeposited onto SnO2

Abstract: This paper describes the successful use of thin layers of birnessite to degrade methylene blue (MB) contained in aqueous solutions This dye is a representative of a class of dyestuffs resistant to biodegradation The thin layers of birnessite, electrodeposited onto a cheap transparent semiconductor substrate (SnO 2 ), in neutral aerated sulphate solutions at room temperature, are very homogeneous, adherent and well crystallised We showed that these thin layers can discolor the MB solutions totally at room temperature after only 2 h Total organic carbon (TOC) analyses report the absence of organic compounds in solutions after treatment, in the best conditions Mass spectrometry reveals the presence of intermediate reaction products (azure A, azure B, azure C, and thionin) during interaction confirming the real degradation of dye Nitrate and ammonium ions were quantified showing that thin layer of birnessite can mineralise MB To understand mechanism, interaction experiments were made with each intermediary compound The electron transfers lead to a rapid N-demethylation oxidative reaction to form colored intermediary compounds In all cases, thionin was identified as the last adsorbed organic compound onto the birnessite external surface, which is then mineralised slowly into nitrate and ammonium ions These results suggest that birnessite thin layers may be envisaged as a new non-toxic material for treatment of diluted colored wastewater

Vibrational Spectroscopic Characterization of Hematite, Maghemite, and Magnetite Thin Films Produced by Vapor Deposition

Abstract: Thin films of three iron oxide polymorphs, hematite, maghemite, and magnetite, were produced on KBr substrates using a conventional electron beam deposition technique coupled with thermal annealing. This method allowed for iron oxide thin films free from chemical precursor contaminants. The films were characterized using Fourier-transform infrared spectroscopy (FTIR), Raman microspectroscopy, and ellipsometry. These spectroscopic techniques allowed for a clear assignment of the phase of the iron oxide polymorph films produced along with an examination of the degree of crystallinity possessed by the films. The films produced were uniform in phase and exhibited decreasing crystallinity as the thickness increased from 40 to 250 nm.

Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers.

Abstract: Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal?organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour?liquid?solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro-?and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I?V characteristics of ZnO:P nanowire/ZnO:Ga p?n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence characteristics aimed at the development of white LEDs are demonstrated. Although some of the presented LEDs show visible emission for applied biases in excess of 10 V, optimized structures are expected to provide the same emission at much lower voltage. Finally, lasing from ZnO nanorods is briefly reviewed. An example of a recent whispering gallery mode (WGM) lasing from ZnO is demonstrated as a way to enhance the stimulated emission from small size structures.

Electrochemical Synthesis of Metal Oxides and Hydroxides

Abstract: Emerging electrosynthetic techniques such as electrogeneration of base, anodic oxidation, and ac (alternating current) synthesis provide simple and inexpensive alternative routes to the synthesis of ceramic thin films and coatings, nanoparticulate materials, and metastable phases. In this review, we survey illustrative examples to highlight the potential application of these techniques in meeting the goals of inorganic solid-state synthesis.