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The kinetics of tarnishing formation was examined on a polished silver dipped in a 10 mM Na2S. The recovery of an initial bright surface was then obtained by cathodic reduction of the tarnish layer in a 5% sesqui-carbonate solution. Two protection methods to prevent a further formation of a dark deposit were tested: an electrodeposited poly(amino-triazole) film and the surface treatment in hexadecane-thiol. The protection by poly(amino-triazole) is not reliable for all nuances of silver. In contrast, the film formed with hexadecane-thiol showed satisfactory properties. The formations of tarnish and protective films were examined by electrochemical methods, the reflectance measurements, and the quartz crystal microbalance.

Novel, composite silver/titania immobilized on glass substrates were prepared, characterized and their photocatalytic activity was evaluated. The undoped original material consists of rough, high surface area nanocrystalline titanium dioxide (TiO2) thin films. To increase their efficiency, the TiO2films were modified by silver cations deposition and subsequent UV-C irradiation. SEM pictures confirmed the existence of an open porous network of interconnected titania particles on the semiconductor surface. AFM analysis proved the presence of spherical silver particles on the catalyst surface and provided quantitative surface parameters as fractal dimension, surface roughness and mean particle diameter. Spectroreflectometry showed the presence of an increase in optical absorbance attributed to plasmon resonance absorption of the silver clusters. The photocatalytic properties of the surface modified materials were investigated through photodegradation of Methyl Orange. The silver deposition conditions were optimized for maximum photocatalytic efficiency and crucial parameters such as dipping period, UV irradiation time, and concentration of the dipping solution were determined. The optimum silver nitrate concentration of the dipping solution was found to be10-3M. This silver doped photocatalyst decomposes the azo-dye pollutant 3-times faster than the un-doped Degussa P25TiO2film. A concentration increase results in a decrease of the films photocatalytic performance. Strength and reproducibility tests proved that the photocatalytic activity of the silver doped titania was perfectly reproducible.

Semi-transparent microporous TiO 2 films on SnO 2 -coated conductive glass were prepared by applying a sol–gel process. Surface topography analysis was conducted with atomic force microscopy, which revealed a highly textured and rough surface, possessing a high capacity for adsorption of a diverse variety of compounds. Surface modification of the films with ascorbic acid results in the formation of a stable, coloured surface complex which red shifts the absorption threshold of TiO 2 , enhancing utilisation of the solar spectrum. Upon illumination in a liquid electrochemical cell, ascorbic acid injects electrons into the conduction band of the semiconductor, giving rise to electrical current. The incident-photon-to-current efficiency presents a maximum at 415 nm (5.29%).

Electrochemical reactivities and structural properties of several nickel hydroxide powders were analysed by X-ray diffraction, Raman spectroscopy and extended X-ray absorption fine structure (EXAFS). It is shown that the electrochemical efficiency of β-Ni(OH) 2 is associated with the amount of proton vacancies included in the crystal lattice. The number of those proton vacancies increases when the crystallite size decreases or when the ratio of co-precipitated cobalt increases. Proton vacancies shift the oxidation potential of β-Ni(OH) 2 towards less anodic values and, therefore, improve the chargeability and the electrochemical efficiency of nickel hydroxide. It is shown that both Raman spectroscopy and X-ray diffraction techniques can be used to predict effectively the electrochemical efficiency of β-Ni(OH) 2 hydroxide. EXAFS results indicate also that the oxidation level of nickel atoms inside the hydroxide is not modified by the existence of proton vacancies. It means probably that to maintain the electroneutrality in the whole crystal induces others singularities. Finally, the influence of co-precipitated additives such as cadmium and cobalt on the rate of defects has been investigated.

Hollow sea urchin shaped nanostructured polypyrrole powder was successfully synthesized chemically in an acidic medium through a core-shell redox mechanism by using a nanostructured MnO2 powder as oxidizing agent and sacrificial template simultaneously. The morphology and the structure of MnO2 powder based reactant and produced polypyrrole powder were characterized respectively by using FEG-SEM, TEM, EDX and XRD techniques, which led us to demonstrate clearly the formation of hollow and open microparticles of polypyrrole with the presence of nanotubes on their surface. Nanostructured polypyrrole powder was found to be rather amorphous even though the shape of the polypyrrole particles was induced by the crystalline and nanostructured sea urchin shaped MnO2 powder on which they grew. In addition, neither MnO2 nor any manganese based species were found within the produced polypyrrole powder, which ruled out the production of composite materials. Moreover, Raman technique showed that the synthesized PPy powder was produced in the oxidized and thus conducting state. It actually possesses a 0.31 doping level and a 0.05 S cm(-1) conductivity, as shown by XPS and impedance spectroscopy measurements respectively. Cyclic voltammetry and UV-vis spectroscopy studies allowed us to identify the oxidation mechanism of pyrrole by our MnO2 powder through the detection of soluble Mn2+ cations as reaction products isolated after filtration of the reaction medium. (c) 2013 Elsevier B.V. All rights reserved.

Five Ni-Cr industrial dental alloys, containing or not containing beryllium, have been studied by cyclic voltammetry and in situ Raman spectroscopy, in electrolytic solutions with or without chloride. In the absence of chloride, the five samples behave similarly, but in KCl solution, localized corrosion appearing as “black dots” is particularly evident in the case of the Be-containing alloys. Raman spectroscopy allows the identification of these local corrosion products as different forms of molybdates and chromates, together with some other unidentified compounds.

The corrosion of zinc-coated steel sheets was studied by Raman spectroscopy. In aerated 0.03 M NaCl solutions, a large variety of corrosion products were identified in situ on unpainted sheets after 7 days of immersion. Zinc oxide, zinc hydroxychloride and zinc hydroxide were observed. For painted specimens, two main products, zinc oxide and zinc hydroxychloride, have been identified under paint blisters. It appeared that a different type of corrosion process is occurring under a paint film. It is hypothesized that the barrier properties of the paint are capable of modifying the mechanisms and thus the nature of the corrosion products. However, for both unpainted and painted specimens the nature of the corrosion products seems to depend on the local pH values in relation to chloride concentrations.

Objective:To report the rationale, recruitment, design, dietary intervention and baseline characteristics of participants in the Medi-RIVAGE study (Mediterranean Diet, Cardiovascular Risks and Gene Polymorphisms).Design:A randomised, parallel trial comparing a new nutritional programme with a conventional programme.Setting:Centre for Detection and Prevention of Arteriosclerosis, Timone University Hospital, Marseille, France, and collaborating teams.Subjects:Two hundred and twelve male and female volunteers with at least one cardiovascular risk factor.Intervention:A Mediterranean-type diet characterised mainly by the quality of fatty acids, amount of fish, vegetable foodstuffs and fibre was proposed and compared with a usually prescribed, low-fat/cholesterol diet. Body mass index, fasting lipids and lipoproteins, apolipoproteins, glucose, insulin and homocysteine were the main outcome measures. Gene polymorphisms of interest were determined.Results:Characteristics of men in the two arms were comparable with regard to sociodemographic variables, and clinical and biological cardiovascular risk factors. There were few differences between the groups of women (cholesterol-related parameters,P< 0.05). There was no difference between arms in allelic distribution of the gene polymorphisms studied. Saturated fat and protein intakes were high while carbohydrate and fibre intakes were low, but with no difference between arms. Overall, the nutritional markers were comparable in both arms with few exceptions. Correlations between nutritional intakes and plasma nutrient levels ranged from 0.19 (β-carotene) to 0.47 (folate).Conclusions:The comparability of the two arms is notable and warrants a low risk of biases. Current diet departs from the traditional Mediterranean one. The assessment of nutritional intake is validated by correlations obtained between dietary intake and relevant biomarkers. This will be important to estimate participant compliance and to analyse intervention data.