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Measurements of ion distributions at a charged solid–liquid interface using X-ray standing waves (XSW) are presented. High energy synchrotron radiation (17.48 keV) is used to produce an XSW pattern inside a thin water film on a silicon wafer. The liquid phase is an aqueous solution containing Br and Rb ions. The surface charge is adjusted by titration. Measurements are performed over a pH range from 2.2–9, using the native Si oxide layer and functional (amine) groups as surface charge. The Debye length, indicating the extension of the diffuse layer, could be measured with values varying between 1–4 nm. For functionalized wafers, the pH dependent change from attraction to repulsion of an ion species could be detected, indicating the isoelectric point. In combination with the measurement of the streaming current, the surface charge of the sample could be quantified.
We report the results of an analytical investigation
on 416 silver-copper coins stemming from the Ottoman
Empire (end of 16th and beginning of 17th centuries), using
synchrotron micro X-ray fluorescence analysis (SRXRF).
In the past, analyses had already been conducted with energy
dispersive X-ray fluorescence analysis (EDXRF), scanning
electron microscopy with energy dispersive X-ray spectrometry
(SEM/EDX) and proton induced X-ray emission spectroscopy (PIXE).With this combination of techniques it was
possible to confirm the fineness of the coinage as well as to
study the provenance of the alloy used for the coins.
For the interpretation of the data statistical analysis
(principal component analysis—PCA) has been performed.
A definite local assignment was explored and significant
clustering was obtained regarding the minor and trace elements
composing the coin alloys.
Well-defined and facetted bimetallic gold–palladium nanoalloys have been synthesized and anchored in spherical polyelectrolyte brushes (SPB) as composite particles (AuPd@SPB). These particles are better catalysts in aqueous phase than the pure metals. The atomistic arrangement of these nanoalloys has been analysed by extended X-ray absorption fine structure (EXAFS) spectroscopy at the Au–L3 and the Pd–K absorption edge. The samples with high amounts of gold appear as almost statistically mixed random alloys. Alloy compositions with less gold show slight enrichment of Pd at the surface of the particle. In addition, signals of non-metallic palladium appear at the Pd–K edge which indicate the presence of the Pd2+ species in addition to metallic palladium. The relation of these structural features to the catalytic activity is discussed.
Four hundred and sixteen silver coins stemming from the Ottoman Empire (16th and 17th centuries) were analyzed to confirm the fineness of the coinage as well as to study the provenance of the alloy used for the coins. As most of the coins showed the typical green patina on their surfaces due to corrosion processes that have led to the depletion of copper in the near surface domains of the silver coins in comparison to their core composition, small samples had to be taken, embedded in synthetic resin, and cross sectioned to investigate the true-heart metal composition. µ-synchrotron micro X-ray fluorescence analysis and µ-proton-induced X-ray emission were applied to determine the silver contents as well as the minor and trace elements. The type of the alloy was investigated as well as if coins minted in different locations demonstrated homogeneous traits concerning the predominant impurities (Au and Bi), which could suggest a common ore. Finally, energy-dispersive microanalysis in a scanning electron microscope was applied to study the homogeneity/heterogeneity of the coins and the presence of surface enrichments and to explain differences between the µ-synchrotron micro X-ray fluorescence analysis and µ-proton-induced X-ray emission measurements concerning the main component. In general, the silver content of the analyzed specimen varies between 90 and 95%. These outcomes have not supported the historical interpretations, which predict that during the period studied, a debasement of approximately 44% of the silver content of the coins should have occurred.