Non-resonant inelastic X-ray scattering for discrimination of pigments.

Inelastic X-ray scattering (IXS) spectroscopy has been used in many fields of solid-state physics and theoretical chemistry as an accurate and quantitative probe of elementary excitations. We show that non-resonant IXS spectra in the energy loss range below 100 eV exhibit a strong contrast across a wide range of commercially available pigments, opening new routes for their discrimination. These signatures combine plasmonic transitions, collective excitations and low energy absorption edges. We have performed IXS to discriminate different artists' pigments within complex mixtures and to quantitatively determine rutile and anatase polymorphs of TiO2. The integration of experimental data on pigment powders with suitable ab initio simulations shows a precise fit of the spectroscopic data both in the position of the resonances and in their relative intensity.

Physicochemical characterization of acrylamide/bisacrylamide hydrogels and their application for the conservation of easel paintings.

Acrylamide chemical gels have been synthesized to obtain systems with mechanic and hydrophilic properties suitable for the cleaning of works of art. The gel characteristics were tailored by changing the polymer percentage present in the final hydrogel formulation from 2 to 10% w/w. Two different hydrogels have been selected in this interval for an in depth characterization (i.e., S 4% w/w and H 6% w/w). Water retention properties of the gels along with the free water index have been determined by the combination of standard dehydration tests and differential scanning calorimetry (DSC) measurements. The gels' structure has been determined by scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS). The water retention capacity of hydrogel, H, was also determined. Cleaning tests on easel painting replicas, performed with both hydrogels loaded with an aqueous detergent system, showed good results in the removal of a widely used synthetic adhesive and hence offered these gels as a real alternative to the widely applied physical gel methodology with the advantage of being a residue-free technique. A preliminary SAXS investigation confirms the persistence of the detergent system nanostructure inside the hydrogel.