Yellow pyroantimonates Pb-Sb, Pb-Sb-Sn and Pb-Sb-Zn were synthesized by solid-state reactions at high temperature and characterized by X-ray diffraction and Raman spectroscopy. The lattice size of cubic pyrochlores increases with Sn and Zn doping and with Pb overstoichiometry, indicating the replacement of Sb 5+ by the larger cations. This fact permits the understanding of the corresponding Raman spectral modifications as a consequence of the changes in the local symmetry of the Sb-O polyhedra, justifying the exploitation of Raman spectroscopy to noninvasively identify structural modifications of pyroantimonate pigments in artworks.

The topic of the review is the electrochemical analysis of solids aimed to identify or determine their phase or elemental composition, analyse the composition of solid mixtures, characterise their electrochemistry-related properties and analyse the redox state of the constituent elements. The ways of the electrode preparation are discussed with a special attention paid to compact and composite electrodes including carbon-paste electrodes, and direct immobilisation of powders on a working electrode. Examples are given of simultaneous electrochemical measurements combined with X-ray diffraction, optical or atomic force microscopy, and mass measurement by quartz microbalance. The state-of-art of voltammetric analysis of inorganic and organic solids achieved in the last two decades is systematically reviewed with the aim to find cases, when electrochemistry can compete successfully with other analytical techniques as for sensitivity, specificity, and sample consumption. Electrochemical methods are shown to be a perspective tool for redox analysis of catalysts, combined elemental and phase analysis of inorganic pigments and minerals, characterisation of solid solutions, metalloorganic and organic solids. A review with 196 references.

The effectiveness of Raman spectroscopy (using a bench-top system on standard pigments) for the characterisation of modified lead antimonate yellows was demonstrated in the already published Part I. The knowledge gained is employed here for the study of yellow glazes on genuine Renaissance plates with the aim of identifying non-invasively lead pyroantimonate compounds by portable micro-Raman equipment. The investigation was carried out directly on site, at the Victoria and Albert Museum (London, UK) and at the Museo Statale d'Arte Medievale di Arezzo (Arezzo, Italy), combining Raman and X-ray fluorescence analyses. In addition to the spectral features of both unmodified Naples yellow and Sn-and Zn-modified lead antimonatecompounds, the Raman patterns related to partially modified pyrochlore structures were observed. For this reason, the possible Sn-induced modification of Naples yellow by cassiterite (SnO 2 ), present within the glaze as opacifier was explored on lead antimonate yellow glaze mock-ups fired at different temperatures.

BackgroundGraphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties.ResultsTiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer–Emmett–Teller surface area and Barrett–Joiner–Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 μm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase.ConclusionsThe best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light.

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