Competitive kinetic study of sulfide oxidation by sodium hypochlorite:influence of the pH and the temperature.

International audienceThe kinetics of sulfide oxidn. by sodium hypochlorite was exptl. investigated. The influence of some parameters such as pH (from 3.5 to 11) and the temp. (from 5 to 25°C) using the competitive kinetic method was studied. The sulfite ion was chosen due to the knowledge of its reaction kinetics with sodium hypochlorite. In a first step, sulfide and sulfite ions oxidn. was realized either in pure substance to det. the stoichiometry of each reaction depending on the initial concns. In a second step, the study of the competitive kinetics of sulfides and sulfites allowed to det. the values of the kinetic const. of the oxidn. reaction of chlorine with hydrogen sulfide: 6.3 104 at pH =11 and 8.2 109 at pH = 3.5. [on SciFinder(R)

Photoluminescence Study of Eu+3 doped ZnO Nanocolumns Prepared by Electrodeposition Method

[EN] Europium doped ZnO (ZnO:Eu) nanocolumns were grown on indium tin oxide substrates (ITO) by electrodeposition method in zinc nitrate aqueous solution with different concentration of Eu. According to XRD results electrodeposited ZnO:Eu films exhibit thigh crystalline quality with a preferential orientation parallel to c-axis. Moreover, the (002) peak position shifts toward to lower angles confirming the incorporation of Eu+3 ions into the ZnO lattice. The crystallite size of a pure ZnO decreases when increasing the Eu doping. SEM images reveal a well dense nanocolumns arrays perpendicular to the surface. Furthermore, doping with Eu+3 ions leads to a change in the top of nanocolumns from hexagonal to conic-hexagonal shape. The average diameters of nanocolumns are found to be around 200 nm and 180 nm for undoped ZnO and Eu doped ZnO, respectively. Photoluminescence (PL) emission from ZnO:Eu thin films reveals the typical peaks related to excitons and intrinsic defects in ZnO and four narrow peaks in the red region attributed to 4f-shell transition in Eu+3 ions. As Eu doping increased, PL peaks related to Eu+3 emission showed an increase in intensity and a shift in its wavelength position. A schematic drawing of the excitation mechanism and related emission process is proposed.Nouri, AN.; Beniaiche, AB.; Marí, B.; Guessas, H.; Azizi, A. (2017). Photoluminescence Study of Eu+3 doped ZnO Nanocolumns Prepared by Electrodeposition Method. Optik - International Journal for Light and Electron Optics. 139:104-110. doi:10.1016/j.ijleo.2017.03.075S10411013

Nucleation, growth and properties of Co nanostructures electrodeposited on n-Si(1 1 1)

In the present work, cobalt thin films deposited directly on n-Si(111) surfaces by electrodeposition in Watts bath have been investigated. The electrochemical deposition and properties of deposits were studied using cyclic voltammetry (CV), chronoamperometry (CA), ex situ atomic force microscopy (AFM), X-ray diffraction (XRD) and alternating gradient field magnetometer (AGFM) techniques. The nucleation and growth kinetics at the initial stages of Co studied by current transients indicate a 3D island growth (Volmer-Weber); it is characterized by an instantaneous nucleation mechanism followed by diffusion limited growth. According to this model, the estimated nucleus density and diffusion coefficient are on the order of magnitude of 10(6) cm(-2) and 10(-5) cm(2) s(-1), respectively. AFM characterization of the deposits shows a granular structure of the electrodeposited layers. XRD measurements indicate a small grain size with the presence of a mixture of hcp and fcc Co structures. The hysteresis loops with a magnetic field in the parallel and perpendicular direction and showed that the easy magnetization axis of Co thin film is in the film plane. (C) 2011 Elsevier B.V. All rights reserved