Abstract: This work shows the benefits of characterizing historic paintings via compositional and microtextural data from micro-X-ray diffraction (μ-XRD) combined with molecular information acquired with Raman microscopy (RM) along depth profiles in paint stratigraphies. The novel approach was applied to identify inorganic and organic components from paintings placed at the 14th century Islamic UniversityMadrasah Yusufiyyain Granada (Spain), the only Islamic University still standing from the time of Al-Andalus (Islamic Spain). The use of μ-XRD to obtain quantitative microtextural information of crystalline phases provided by two-dimensional diffraction patterns to recognize pigments nature and manufacture, and decay processes in complex paint cross sections, has not been reported yet. A simple Nasrid (14th century) palette made of gypsum, vermilion, and azurite mixed with glue was identified in polychromed stuccos. Here also a Christian intervention was found via the use of smalt, barite, hematite, Brunswick green and gold; oil was the binding media employed. On mural paintings and wood ceilings, more complex palettes dated to the 19th century were found, made of gypsum, anhydrite, barite, dolomite, calcite, lead white, hematite, minium, synthetic ultramarine blue, and black carbon. The identified binders were glue, egg yolk, and oil.

Abstract: Urban atmospheres in modern cities carry characteristic mixtures of particulate pollution which are potentially aggravating for chronic respiratory patients (CRP). Although air quality surveys can be detailed, the obtained information is not always useful to evaluate human health effects. This paper presents a novel approach to estimate particle deposition rates in airways of CRP, based on real air pollution data. By combining computational fluid dynamics with physical-chemical characteristics of particulate pollution, deposition rates are estimated for particles of different toxicological relevance, that is, minerals, iron oxides, sea salts, ammonium salts, and carbonaceous particles. Also, it enables some qualitative evaluation of the spatial, temporal, and patient specific effects on the particle dose upon exposure to the urban atmosphere. Results show how heavy traffic conditions increases the deposition of anthropogenic particles in the trachea and lungs of respiratory patients (here, +0.28 and +1.5 μg·h1, respectively). In addition, local and synoptic meteorological conditions were found to have a strong effect on the overall dose. However, the pathology and age of the patient was found to be more crucial, with highest deposition rates for toxic particles in adults with a mild anomaly, followed by mild asthmatic children and adults with severe respiratory dysfunctions (7, 5, and 3 μg·h1, respectively).

Abstract: The darkening of lead chromate yellow pigments, caused by a reduction of the chromate ions to Cr(III) compounds, is known to affect the appearance of several paintings by Vincent van Gogh. In previous papers of this series, we demonstrated that the darkening is activated by light and depends on the chemical composition and crystalline structure of the pigments. In this work, the results of Part 2 are extended and complemented with a new study aimed at deepening the knowledge of the nature and distribution of Cr and S species at the interface between the chrome yellow paint and the nonoriginal coating layer. For this purpose, three microsamples from two varnished paintings by Van Gogh and a waxed low relief by Gauguin (all originally uncoated) have been examined. Because nonoriginal coatings are often present in artwork by Van Gogh and contemporaries, the understanding of whether or not their application has influenced the morphological and/or physicochemical properties of the chrome yellow paint underneath is relevant in view of the conservation of these masterpieces. In all the samples studied, microscopic X-ray fluorescence (mu-XRF) and X-ray absorption near edge structure (mu-XANES) investigations showed that Cr(III)-based alteration products are present in the form of grains inside the coating (generally enriched of S species) and also homogeneously widespread at the paint surface. The distribution of Cr(III) species may be explained by the mechanical friction caused by the coating application by brush that picked up and redistributed the superficial Cr compounds, likely already present in the reduced state as result of the photodegradation process. The analysis of the XANES profiles allowed us to obtain new insights into the nature of the Cr(III) alteration products, that were identified as sulfate-, oxide-, organo-metal-, and chloride-based compounds. Building upon the knowledge acquired through the examination of original paint samples and from the investigation of aged model paints in the last Part 4 paper, in this study we aim to characterize a possible relation between the chemical composition of the coating and the chrome yellow degradation pathways by studying photochemically aged model samples covered with a dammar varnish contaminated with sulfide and sulfate salts. Cr speciation results did not show any evidence of the active role of the varnish and added S species on the reduction process of chrome yellows.

Abstract: The usefulness of fullerene modified glassy carbon electrode in mediating the reduction of cefitizoxime in solubilized system has been demonstrated. Due to the unique structure and extraordinary properties, fullerene shows higher catalytic efficiency towards cefitizoxime reduction. The kinetic parameters, electron transfer coefficient (α) and rate constant (K0) across the modified electrode are 0.37 and 0.1081/s respectively. The proposed square-wave voltammetric method is linear over the concentration range 1.210.3 µg/mL. The limit of detection (LOD) is found 0.27 ng/mL. High sensitivity and selectivity together with low detection limit of the electrode response make it suitable for the determination of cefitizoxime.

Abstract: There is a growing interest in the technological transfer of highly performing electrochemical sensors within portable analytical devices for the in situ monitoring of environmental contaminants, such as perfluorooctanesulfonic acid (PFOS). In the redesign of biomimetic sensors, many parameters should be taken into account from the working conditions to the electrode surface roughness. A complete characterization of the surface modifiers can help to avoid time-consuming optimizations and better interpret the sensor responses. In the present study, a molecularly imprinted polymer electrochemical sensor (MIP) for PFOS optimized on gold disk electrodes was redesigned on commercial gold screen-printed electrodes. However, its performance investigated by differential pulse voltammetry was found to be poor. Before proceeding with further optimization, a morphological study of the bare and modified electrode surfaces was carried out by scanning electron microscopy-energy-dispersive X-ray spectrometry (SEM-EDS), atomic force microscopy (AFM) and profilometry revealing an heterogeneous distribution of the polymer strongly influenced by the electrode roughness. The high content of fluorine of the target-template molecule allowed to map the distribution of the molecularly imprinted polymer before the template removal and to define a characterization protocol. This case study shows the importance of a multi-analytical characterization approach and identify significant parameters to be considered in similar redesigning studies.

Abstract: Synchrotron radiation (SR)-based X-ray methods are powerful analytical tools for several purposes. They are widely used to probe the degradation mechanisms of inorganic artists' pigments in paintings, including chrome yellows (PbCr1-xSxO4; 0 <= x <= 0.8), a class of compounds often found in Van Gogh masterpieces. However, the high intensity and brightness of SR beams raise important issues regarding the potential damage inflicted on the analyzed samples. A thorough knowledge of the SR X-ray sensitivity of each class of pigment in the painting matrix is therefore required to find analytical strategies that seek to minimize the damage for preserving the integrity of the analyzed samples and to avoid data misinterpretation. Here, we employ a combination of Cr K-edge X-ray absorption near-edge structure spectroscopy, Cr-K-beta X-ray emission spectroscopy, and X-ray diffraction to monitor and quantify the effects of SR X-rays on the stability of chrome yellows and related Cr compounds and to define mitigation strategies. We found that the SR X-ray beam exposure induces changes in the oxidation state and local coordination environment of Cr ions and leads to a loss of the compound's crystalline structure. The extent of X-ray damage depends on some intrinsic properties of the samples (chemical composition of the pigment and the presence/absence and nature of the binder). It can be minimized by optimizing the overall fluence/dose released to the samples and by working in vacuum and under cryogenic conditions.

Abstract: Particulate matter (PM) deposition on urban green enables the collection of particulate pollution from a diversity of contexts, and insight into the physico-chemical profiles of PM is key for identifying main polluting sources. This study reports on the morphological and elemental characterization of PM2-10 deposited on ivy leaves from five different environments (forest, rural, roadside, train, industry) in the region of Antwerp, Belgium. Ca. 40,000 leaf-deposited particles were thoroughly investigated by particle-based analysis using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) and their physico-chemical characteristics were explored for PM source apportionment purposes. The size distribution of all deposited particles was biased towards small-sized PM, with 32% of the particles smaller than 2.5 mu m (PM2.5) and median diameters of 2.80-3.09 mu m. The source type influenced both the particles' size and morphology (aspect ratio and shape), with roadside particles being overall the smallest in size and the most spherical. While forest and rural elemental profiles were associated with natural PM, the industry particles revealed the highest anthropogenic metal input. PM2-10 profiles for roadside and train sites were rather comparable and only distinguishable when evaluating the fine (2-2.5 mu m) and coarse (2.5-10 mu m) PM fractions separately, which enabled the identification of a larger contribution of combustion-derived particles (small, circular, Fe-enriched) at the roadside compared to the train. Random forest prediction model classified the source type correctly for 61-85% of the leaf-deposited PM. The still modest classification accuracy denotes the influence of regional background PM and demands for additional fingerprinting techniques to facilitate source apportionment. Nonetheless, the obtained results demonstrate the utility of leaf particle-based analysis to fingerprint and pinpoint source-specific PM, particularly when considering both the composition and size of leaf-deposited particles.

Abstract: Bilayers of carbon, consisting of a layer of natural carbon and a second layer highly enriched in 13C, were investigated with the LAMMA 500-® instrument. When such a bilayer is perforated by the laser beam, comparable amounts of 12C and 13C are evaporated and partly ionized so that geometry effects and recombination reactions during laser-induced ionization can straightforwardly be studied.

Abstract: A detailed account is given of neutron and γ-ray attenuation effects in 14-MeV neutron activation analysis of oxygen. Appropriate neutron cross-section values have been determined in two different ways and compared with literature values. It appears that the attenuation process is best described in terms of nonelastic scattering cross-sections. It is also shown that the narrow beam total γ-ray attenuation coefficients at 6 MeV, given in the literature are suitable for correction purposes if 16N γ-rays are counted with a window of 4.56.5 MeV. Attention was paid to the contribution of β-rays when the 16N activity is counted in this energy interval with a NaI(Tl) detector.

Abstract: The palaeontological collections of the Muséum national dHistoire naturelle (MNHN, Paris, France) and the Muséum dHistoire naturelle dAutun (MHNA, Autun, France) include many fossil specimens originating from the argillaceous shales of the Autun basin (Saône-et-Loire, France). These fossils are preserved within sedimentary rocks containing unstable sulphide compounds, such as pyrite, which may deteriorate in contact with water and oxygen. This alteration provokes crystalline efflorescence and cracks, thus compromising the preservations of the fossils. This work constitutes the first step of a project that aims to understand the mechanisms of alteration of these materials in order to define conservation guidelines for palaeontological collections. For this purpose, eight damaged specimens originating from the Permian Autun basin (Saône-et-Loire, France) were selected and analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM/EDS) and X-ray absorption spectroscopy at the threshold of the sulphur Kα-edge (XANES). This methodology enabled the characterization of the matrices composition and the chemical nature of the alterations. Subsequently, we have sought to reproduce by artificial ageing the alteration phenomena encountered in the collections. New shale samples were collected on seven outcrops of the same Autun basin. They were analyzed and subjected to artificial ageing at 50% relative humidity (RH) and at temperatures ranging between 40 °C and 90 °C. Our work shows that damaged specimens and newly collected shale have a similar mineralogical composition. Yet the crystalline efflorescence material formed on the surface of damaged specimens belongs to the iron sulphate group whereas gypsum predominates on artificially aged shale samples. Reproducing the alterations observed on specimens by artificial ageing remains therefore problematic. Additionally, it appears that the temperature of ageing controls the nature of the damage: at 40 °C, many samples are mechanically damaged whereas no or minor crystalline efflorescence occurs. At 90 °C, it is the opposite tendency that is observed. Finally, mechanical damages do not seem to be correlated with the development of the efflorescence: samples with efflorescent crystals generally do not show clearly visible cracks; those that seem most fragmented do not show any visible efflorescence.

Abstract: In this study, the results of analysing of a series of 16th-19th century painted enamel objects of the Limoges School currently in collections in three Dutch and Flemish museums by means of portable and micro x-ray fluorescence analysis (PXRF and µ-XRF) and electron probe micro analysis (EPMA) are presented. The aim of the investigation was the authentication of specific pieces. Therefore, the glass compositions as well as the (glass) colouring agents used by the Limoges' artists were studied as a function of the age of the objects. Due to the evolution of these properties, it is possible to approximately date these objects based on their chemical composition. The complete émail peint collection of the Museum Boijmans-Van Beuningen (Rotterdam, The Netherlands), consisting of 20 émail peint plaques, was analysed with µ-XRF. Quantitative information was obtained by EPMA analysis of 15 enamel fragments of objects from museum and private collections in the Low Countries. PXRF analyses were performed on the painted enamel collection of the Antwerp Vleeshuis Museum (13 objects) and the Mayer van den Bergh Museum (4 objects) and on a set of 18 plaques that were donated to the Boijmans-Van Beuningen Museum by a private collector. The results obtained by means of EPMA, µ-XRF and PXRF proved to be useful in the discrimination of 16th century painted enamel objects from those of the19th century. From a total of 70 objects examined, 2 objects (OM964A and OM993) featured a chemical signature that deviated from the published literature composition and pigment use consistent with its presumed period of manufacture.

Abstract: Previous investigations about the darkening of chrome yellow pigments revealed that this form of alteration is attributable to a reduction of the original Cr(VI) to Cr(III), and that the presence of sulfur-containing compounds, most often sulfates, plays a key role during this process. We recently demonstrated that different crystal forms of chrome yellow pigments (PbCrO4 and PbCr1xSxO4) are present in paintings by Vincent van Gogh. In the present work, we show how both the chemical composition and the crystalline structure of lead chromate-based pigments influence their stability. For this purpose, oil model samples made with in-house synthesized powders of PbCrO4 and PbCr1xSxO4 were artificially aged and characterized. We observed a profound darkening only for those paint models made with PbCr1xSxO4, rich in SO42 (x ≥ 0.4), and orthorhombic phases (>30 wt %). Cr and S K-edge micro X-ray absorption near edge structure investigations revealed in an unequivocal manner the formation of up to about 60% of Cr(III)-species in the outer layer of the most altered samples; conversely, independent of the paint models chemical composition, no change in the S-oxidation state was observed. Analyses employing UVvisible diffuse reflectance and Fourier transform infrared spectroscopy were performed on unaged and aged model samples in order to obtain additional information on the physicochemical changes induced by the aging treatment.