Exploring the Depths of Corrosion: A Novel GE-XANES Technique for Investigating Compositionally Complex Alloys.

In this study, we propose the use of nondestructive, depth-resolved, element-specific characterization using grazing exit X-ray absorption near-edge structure spectroscopy (GE-XANES) to investigate the corrosion process in compositionally complex alloys (CCAs). By combining grazing exit X-ray fluorescence spectroscopy (GE-XRF) geometry and a pnCCD detector, we provide a scanning-free, nondestructive, depth-resolved analysis in a sub-micrometer depth range, which is especially relevant for layered materials, such as corroded CCAs. Our setup allows for spatial and energy-resolved measurements and directly extracts the desired fluorescence line, free from scattering events and other overlapping lines. We demonstrate the potential of our approach on a compositionally complex CrCoNi alloy and a layered reference sample with known composition and specific layer thickness. Our findings indicate that this new GE-XANES approach has exciting opportunities for studying surface catalysis and corrosion processes in real-world materials.

Quantitative Analysis and 2D/3D Elemental Imaging of Cocoa Beans Using X-ray Fluorescence Techniques.

As an important raw material for the confectionery industry, the cocoa bean (Theobroma cacao L.) has to meet certain legal requirements in terms of food safety and maximum contaminant levels in order to enter the cocoa market. Understanding the enrichment and distribution of essential minerals but also toxic metals is of utmost importance for improving the nutritional quality of this economically important raw food material. We present three X-ray fluorescence (XRF) techniques for elemental bio-imaging of intact cocoa beans and one additional XRF technique for quantitative analysis of cocoa pellets. The interrelation of all the methods presented gives a detailed picture of the content and 3D-resolved distribution of elements in complete cocoa beans for the first time.

Observation of early ZIF-8 crystallization stages with X-ray absorption spectroscopy.

The present study investigates early stages of ZIF-8 crystallization up to 5 minutes post mixing of precursor solutions. Dispersive X-ray Absorption Spectroscopy (DXAS) provides a refined understanding of the evolution of the coordination environment during ZIF-8 crystallization. Linear Combination Analysis (LCA) suggests tetrakis(1-methylimidazole)zinc2+ to be a suitable and stable mononuclear structure analogue for some early stage ZIF-8 intermediates. Our results pave the way for more detailed studies on physico-chemical aspects of ZIF-8 crystallization to better control tailoring ZIF-8 materials for specific applications.

Revealing Silver Nanoparticle Uptake by Macrophages Using SR-µXRF and LA-ICP-MS.

To better study the impact of nanoparticles on both in vitro and in vivo models, tissue distribution and cellular doses need to be described more closely. Here silver nanoparticles were visualized in alveolar macrophages by means of synchrotron radiation micro X-ray fluorescence spectroscopy (SR-µXRF) with high spatial resolution of 3 × 3 µm2. For the spatial allocation of silver signals to cells and tissue structures, additional elemental labeling was carried out by staining with eosin, which binds to protein and can be detected as bromine signal with SR-µXRF. The method was compatible with immunostaining of macrophage antigens. We found that the silver distribution obtained with SR-µXRF was largely congruent with distribution maps from a subsequent laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of the same tissue sites. The study shows a predominant, though not exclusive uptake of silver into alveolar macrophages in the rat lung, which can be modeled by a similar uptake in cultured alveolar macrophages. Advantages and limitations of the different strategies for measuring nanoparticle uptake at the single cell level are discussed.

Advances in Nickel Nanoparticle Synthesis via Oleylamine Route.

Nickel nanoparticles are an active research area due to their multiple applications as catalysts in different processes. A variety of preparation techniques have been reported for the synthesis of these nanoparticles, including solvothermal, microwave-assisted, and emulsion techniques. The well-studied solvothermal oleylamine synthesis route comes with the drawback of needing standard air-free techniques and often space-consuming glassware. Here, we present a facile and straightforward synthesis method for size-controlled highly monodisperse nickel nanoparticles avoiding the use of, e.g., Schlenk techniques and space-consuming labware. The nanoparticles produced by this novel synthetic route were investigated using small-angle X-ray scattering, transmission electron microscopy, X-ray diffraction, and X-ray spectroscopy. The nanoparticles were in a size range of 4‒16 nm, show high sphericity, no oxidation, and no agglomeration after synthesis.

Assessment of Toxic Metals and Hazardous Substances in Tattoo Inks Using Sy-XRF, AAS, and Raman Spectroscopy.

Synchrotron radiation X-ray fluorescence spectroscopy, in conjunction with atomic absorption and Raman spectroscopy, was used to analyze a set of top brand tattoo inks to investigate the presence of toxic elements and hazardous substances. The Cr, Cu, and Pb contents were found to be above the maximum allowed levels established by the Council of Europe through the resolution ResAP(2008)1 on requirements and criteria for the safety of tattoos and permanent makeup. Raman analysis has revealed the presence of a set of prohibited substances mentioned in ResAP(2008)1, among which are the pigments Blue 15, Green 7, and Violet 23. Other pigments that were identified in white, black, red, and yellow inks are the Pigment White 6, Carbon Black, Pigment Red 8, and a diazo yellow, respectively. The present results show the importance of regulating tattoo ink composition.

The crystallisation of copper(ii) phenylphosphonates.

The crystal structures and syntheses of four different copper(ii) phenylphosphonates, the monophenylphosphonates α-, ß-, and γ-Cu(O3PC6H5)·H2O (α-CuPhPmH (1) ß-CuPhPmH (2) and γ-CuPhPmH (3)), and the diphosphonate Cu(HO3PC6H5)2·H2O (CuPhP2mH (4)), are presented. The compounds were synthesized from solution at room temperature, at elevated temperature, under hydrothermal conditions, and mechanochemical conditions. The structures of α-CuPhPmH (1) and CuPhP2mH (4) were solved from powder X-ray diffraction data. The structure of ß-CuPhPmH (2) was solved by single crystal X-ray analysis. The structures were validated by extended X-ray absorption fine structure (EXAFS) and DTA analyses. Disorder of the crystal structure was elucidated by electron diffraction. The relationship between the compounds and their reaction pathways were investigated by in situ synchrotron measurements.

Time- and spatial-resolved XAFS spectroscopy in a single shot: new analytical possibilities for in situ material characterization.

A new concept that comprises both time- and lateral-resolved X-ray absorption fine-structure information simultaneously in a single shot is presented. This uncomplicated set-up was tested at the BAMline at BESSY-II (Berlin, Germany). The primary broadband beam was generated by a double multilayer monochromator. The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by either an energy-sensitive area detector, the so-called color X-ray camera, or by an area-sensitive detector based on a CCD camera, in θ-2θ geometry. The first tests were performed with thin metal foils and some iron oxide mixtures. A time resolution of lower than 1 s together with a spatial resolution in one dimension of at least 50 µm is achieved.

The structure and in situ synthesis investigation of isomorphic mononuclear molecular metal phenylphosphonates.

We describe a fast and effective synthesis for molecular metal phosphonates. Isomorphic compounds [M(ii)(HO3PPh)2(H2O3PPh)2(H2O)2] (M = Mn (1), Co (2), Ni (3); Ph = C6H5) were obtained by grinding. The complexes are mononuclear compounds containing neutral and monodeprotonated phenylphosphonic acid and water as ligands. The crystal structures were determined using powder X-ray diffraction (PXRD) data and validated by extended X-ray absorption fine structure (EXAFS) data. Combined synchrotron XRD measurements and Raman spectroscopy were conducted for investigating the reactions in situ. Based on these data, the intermediates were characterized and the formation mechanism was derived.

Investigation of short-range structural order in Zr69.5Cu12Ni11Al7.5 and Zr41.5Ti41.5Ni17 glasses, using X-ray absorption spectroscopy and ab initio molecular dynamics simulations.

Short-range order has been investigated in Zr69.5Cu12Ni11Al7.5 and Zr41.5Ti41.5Ni17 metallic glasses using X-ray absorption spectroscopy and ab initio molecular dynamics simulations. While both of these alloys are good glass formers, there is a difference in their glass-forming abilities (Zr41.5Ti41.5Ni17 > Zr69.5Cu12Ni11Al7.5). This difference is explained by inciting the relative importance of strong chemical order, icosahedral content, cluster symmetry and configuration diversity.

The structure of AuPd nanoalloys anchored on spherical polyelectrolyte brushes determined by X-ray absorption spectroscopy.

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.

Beyond the Great Wall: gold of the silk roads and the first empire of the steppes.

Fingerprinting ancient gold work requires the use of nondestructive techniques with high spatial resolution (down to 25 µm) and good detection limits (micrograms per gram level). In this work experimental setups and protocols for synchrotron radiation induced X-ray fluorescence (SRXRF) at the BAMline of the Berlin electron storage ring company for synchrotron radiation (BESSY) in Berlin for the measurement of characteristic trace elements of gold are compared considering the difficulties, shown in previous works, connected to the quantification of Pt. The best experimental conditions and calculation methods were achieved by using an excitation energy of 11.58 keV, a silicon drift chamber detector (SDD) detector, and pure element reference standards. A detection limit of 3 µg/g has been reached. This newly developed method was successfully applied to provenancing the Xiongnu gold from the Gol Mod necropolis, excavated under the aegis of the United Nations Educational, Scientific and Cultural Organization (UNESCO). The composition of the base alloys and the presence of Pt and Sn showed that, contrary to what is expected, the gold foils from the first powerful empire of the steppes along the Great Wall were produced with alluvial gold from local placer deposits located in Zaamar, Boroo, and in the Selenga River.

The charge of solid-liquid interfaces measured by x-ray standing waves and streaming current.

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.

Real-time monitoring of copolymer stabilized growing gold nanoparticles.

A great challenge in the production of nanoparticles with defined sizes and properties is to control their growth in situ. We developed a dedicated combined small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) setup to monitor nanoparticle formation in solution. The capabilities of simultaneously deriving particle sizes and oxidation states of atoms/ions are illustrated for the formation of spherical gold nanoparticles by the reduction of hydrogen tetrachloroaureate (HAuCl(4)). Particles with initial radii of 4.60 +/- 0.10 nm and final radii of 5.67 +/- 0.10 nm were produced in a levitated droplet with a volume of 4 microL. An ethylene oxide/propylene oxide triblock copolymer PEO-PPO-PEO (Pluronic F-127) functions as reducing agent and colloidal stabilizer. XANES shows in situ how the gold was reduced in the droplet from Au(III) to Au(0), and simultaneously SAXS recorded the size distribution of the formed nanoparticles. It is shown that the final particle number is reached quickly. Thereafter, only the particles' sizes increase. Comparison of XANES and SAXS shows that the quantity of Au(0) is higher than the quantity of gold located in the nanoparticles while the particles are growing. Finally, all the Au(0) is found in the nanoparticles. We tentatively attribute this finding to the pseudo crown ether effect of the polymer surfactant that kinetically stabilizes gold atoms when formed from gold ions within their protecting cavity. A simple "burst" mechanism for the gold nanoparticle formation is the consequence. The possibility of an inhomogeneous particles structure with an enhanced density near the particle surface is discussed.