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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.
The Color X-ray Camera CXC or SLcam® is an energy-resolving X-ray camera capable of energy- and space-resolved measurements. It consists of a high-speed CCD detector coupled to a polycapil-lary optic that conducts the X-ray photons from the probe to distinct pixels onto the detector. The camera is capable of fast acquisition of spatially and energy resolved fluorescence images. A dedicated software enables the acquisition and the online processing of the spectral data for all 69696 pixels, leading to a real-time visualization of the elements distribution in a sample. It was developed in a joint project with BAM, IFG Berlin and PN Sensors. In this contribution we will mainly discuss the use of the CXC at our beamline, the BAMline at BESSY II and imaging applications of the CXC from different areas, like biology and archaeometry. Additionally new developments for the use of the detector without optics, like wavelength dispersive detection or 1shot-XANES, will be presented.
The Color X-ray Camera CXC or SLcam® is an energy-resolving X-ray camera capable of energy- and space-resolved measurements. It consists of a high-speed CCD detector coupled to a polycapil-lary optic that conducts the X-ray photons from the probe to distinct pixels onto the detector.
The camera is capable of fast acquisition of spatially and energy resolved fluorescence images. A dedicated software enables the acquisition and the online processing of the spectral data for all 69696 pixels, leading to a real-time visualization of the elements distribution in a sample. It was developed in a joint project with BAM, IFG Berlin and PN Sensors.
In this contribution we will mainly discuss the use of the CXC at our beamline, the BAMline at BESSY II and imaging applications of the CXC from different areas, like biology and archaeometry. Additionally new developments for the use of the detector without optics, like wavelength dispersive detection or 1shot-XANES, will be presented.
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.
The gold finds from Bernstorf, in the Freising district of Bavaria, were discovered in 1998, in the area of a Bronze Age settlement. First analyses with X-ray fluorescence (XRF) revealed gold of an unusually high purity grade, which was explained by using cementation techniques.
A newer analysis with laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) indicated an even higher purity. These analytical results were the starting point of an ongoing discussion. The amount and type of the detected contaminants were highly controversial and led to contradictory interpretations.
We reanalysed 11 gold samples with synchrotron radiation induced X-ray fluorescence (SRXRF) at the BAMline at BESSY-II. To reach the desired detection limits a thorough analysis with three different excitation energies and detection conditions were applied to confirm or disprove the previous results.
In this contribution we will get into the details for the need of the different measurement conditions and the virtues of the use of synchrotron radiation. The use and effectiveness of cementation techniques will be addressed. Finally we will present the achieved results and their impact on the discussion.
n this study, two green synthesis routes were used for the synthesis of Ag/ZnO nanoparticles, using cassava starch as a simple and low-cost effective fuel and Aloe vera as a reducing and stabilizing agent. The Ag/ZnO nanoparticles were characterized and used for bacterial dis-
infection of lake water contaminated with Escherichia coli (E. coli). Characterization indicated the formation of a face-centered cubic structure of metallic silver nanoparticles with no insertion of Ag into the ZnO hexagonal wurtzite structure. Physicochemical and bacteriological analyses described in “Standard Methods for the Examination of Water and Wastewater” were used to evaluate the efficiency of the treatment. In comparison to pure ZnO, the synthesized Ag/ZnO nanoparticles showed high efficiencies against Escherichia coli (E. coli) and general coliforms present in the lake
water. These pathogens were absent after treatment using Ag/ZnO nanoparticles. The results indicate that Ag/ZnO nanoparticles synthesized via green chemistry are a promising candidate for the treatment of wastewaters contaminated by bacteria, due to their facile preparation, low-cost synthesis,and disinfection efficiency.
The gold finds from Bernstorf, in the Freising district of Bavaria, were discovered in 1998, in the area of a Bronze Age settlement. First analyses with X-ray fluorescence (XRF) revealed gold of an unusually high purity grade, which was explained by the use of cementation techniques. A newer analysis with laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) indicated an even higher purity. The analytical results were the starting point of an ongoing discussion. In this study, we re-analysed 11 gold samples with Synchrotron radiation–induced X-ray fluorescence at the BAMline at BESSY. In a thorough analysis, different excitation and detection conditions were applied to confirm or disprove the previous results. It was shown that the purity of the gold from the specimen is higher than 99.9%. The main impurities are silver in a range between 20 and 200 μg/g and copper between 1 and 10 μg/g. The results are in very good agreement with the LA–ICP–MS measurements and provide basic information for discussions about provenance, processing techniques or considerations of authenticity.
In the quest for finding the ideal synchrotron-radiation-induced imaging method for the investigation of trace element distributions in human bone samples, experiments were performed using both a scanning confocal synchrotron radiation micro X-ray fluorescence (SR-mXRF) (FLUO beamline at ANKA) setup and a full-field color X-ray camera (BAMline at BESSY-II) setup. As zinc is a trace element of special interest in bone, the setups were optimized for its detection. The setups were compared with respect to count rate, required measurement time and spatial resolution. It was demonstrated that the ideal method depends on the element of interest. Although for Ca (a major constituent of the bone with a low energy of 3.69 keV for its K alpha XRF line) the color X-ray camera provided a higher resolution in the plane, for Zn (a trace element in bone) only the confocal SR-µXRF setup was able to sufficiently image the distribution.
Synchrotron radiation induced X-ray fluorescence for the characterization of ancient gold objects
(2009)
Several glazed ceramic fragments (XVIth to XVIIIth centuries) from two production centers in Portugal (Coimbra and Lisbon) were the object of this study. The ones from Coimbra comprise two sets of samples: faiences and tiles. The ones from Lisbon are only tiles (azulejos, in Portuguese). The three main divisions of such pieces are the ceramic support (body), glaze and surface decoration. The system decoration/glaze is not easy to investigate, due to the high heterogeneity resulting from the mixing procedures and firing temperatures used. Moreover, the ability of the pigment to diffuse into the base glaze varies depending on the composition of both the pigment and the glaze in terms of fusibility. In order to raster these effects, high resolution techniques are required. In this work, synchrotron micro-X-ray fluorescence (µ-XRF) analysis was performed to monitor the profiles of the characteristic elements from the colors used and the glaze in well prepared cross-sections of the samples. Key elements are: Co for blue, Mn for purple, Cu for green, Sb for yellow, Pb for the glaze and Fe for the body. The major difference observed is that faiences have glaze thicknesses between 150 and 200 µm and tiles have glaze thicknesses between 350 and 400 µm. Furthermore, in faiences all the pigments except the yellow ones are well dispersed into the glassy matrix, while in tiles, all of them are just partially diffused throughout the glaze. However, differences between the tiles from Coimbra and Lisbon were observed. In the samples from Lisbon, a higher intake from the pigment throughout the glaze is observed.
We performed spatially resolved synchrotron-induced x-ray fluorescence analyses (SY-XRF) of five silverpoint drawings from the famous `Karlsruhe sketchbook´ and a silverpoint, which is assumed to be an original one used by the Renaissance artist Hans Baldung Grien (1484-1545) himself. The silverpoint, one out of a very small number of ancient styli conserved nowadays, is fixed on the so-called `Karlsruhe sketchbook´. Measurements were executed at the FLUO-TOPO beamline at the electron storage ring ANKA. It has been shown, that SY-XRF at this beamline is nondestructive and sensitive enough for the analysis of minor and major elements in the silver strokes. This study provides new insights into this graphical technique and ancient drawing instruments: results are that three drawings have been created with a common type of silverpoint containing about (10.4 ± 0.7) wt% of Cu. In all the cases, Hg at a 10% level by weight was identified in the strokes. Presence of Hg is not due to the original silver alloy, but is a result of a general alteration phenomenon of silverpoint drawings. This fact is confirmed by the analysis of the original silverpoint, which contains only small traces of Hg. The result for the copper content of the silverpoint (10.4 ± 1.7) wt% is in good agreement with that of these three drawings. It is supposable that the silverpoint found attached today served for the creation of the corresponding drawings. Moreover, the graphical technique of Baldung is found to be continual over three decades. Only one very late drawing dated to 1543 was probably realized with another silverpoint, containing about 3 wt% of Cu. This difference in the chemical composition of drawings from the late period might be used as a more precise dating indicator of Baldung drawings that are not clearly attributed to a certain period.
The color X-ray camera SLcam® is a full-field, single photon detector providing scanning-free, energy and spatially resolved X-ray imaging. Spatial resolution is achieved with the use of polycapillary optics guiding X-ray photons from small regions on a sample to distinct energy dispersive pixels on a charged-coupled device detector. Applying sub-pixel resolution, signals from individual capillary channels can be distinguished. Therefore, the SLcam® spatial resolution, which is normally limited to the pixel size of the charge-coupled device, can be improved to the size of individual polycapillary channels. In this work a new approach to a sub-pixel resolution algorithm comprising photon events also from the pixel centers is proposed. The details of the employed numerical method and several sub-pixel resolution examples are presented and discussed.
In this study the microscopic homogeneity of the newly developed plastic reference materials BAM H001-BAM H010 was investigated. The materials consist of an acrylonitryle-butadien-styrene terpolymer, doped with different amounts of the elements Br, Cd, Cr, Hg and Pb. For the quantitative determination of the degree of homogeneity, a procedure proposed by Kempenaers et al. (Fresenius J. Anal. Chem., 2001, 369, 733-737) was used. On every sample an extensive number of different points were analyzed and standard deviation for every element mentioned above was used to calculate a minimal sampling mass that is necessary to reach a certain level of uncertainty caused by inhomogeneity (mmin,5%). The experiments were taken out with synchrotron µ-XRF (SR µ-XRF) at BESSYII in Berlin and by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS). The calculated values for mmin,5% of both techniques showed comparable results for all elements. It could be shown that the materials are suitable for calibration of micro analytic techniques if at least 64 µg are used.
This paper is an overview of the work developed by our group in the investigations of museum objects and alluvial gold, reflected in a series of studies published between 2000–2011, supplemented with new results, unpublished up-to-date. The X-ray based spectrometric techniques employed range from various X-Ray Fluorescence (XRF) investigations to ion beam analysis, including synchrotron radiation XRF and micro-Particle Induced X-ray Emission. The gold objects discussed are mainly part of the Sarmizegetusa Dacian hoards—spiraled bracelets (armbands) and coins. After obtaining in 2011 the permission of the Romanian authorities to take very small (1–2 mg) samples from the most 'unimportant' areas of the Dacian bracelets and several Koson staters, to analyze them by micro-SR-XRF at BESSY, in February 2012, the investigation of several micro-areas of 17 stater and 28 bracelet samples revealed important micro-structural inhomogeneity, especially in Sn and Cu. The same inhomogeneous micro-structure has been seen in Transylvanian alluvial gold. The analyses revealed details on the fingerprint of geological gold deposits and also the main characteristics of ancient gold metallurgy procedures used by the Dacians: a relatively low temperature (lower than Au melting point) and hammering during heating to obtain an ingot through sintering. The use of the sintering procedure was proved for the spiraled bracelets and the Koson without monogram coins, a tradition starting in the Bronze Age in Transylvanian gold processing. The existence of micro-inclusions of Ta-minerals in alluvial gold was also detected, explaining Ta trace presence in the artifacts from the Pietroasa hoard.
This work presents a complex evaluation of a series of Geto-Thracian silver adornments found on Romanian territory, part of the 4th century BC Agighiol (Northern Dobruja) hoard and of an ingot from the 1st century BC Geto-Dacian Surcea (Transylvania) hoard, using Synchrotron Radiation X-Ray Fluorescence and micro- Proton Induced X-ray Emission analysis and mapping in order to investigate aspects related to the elemental composition of the metal and the metallurgy implied in their manufacture. One of the samples can be linked to Laurion as the source of metal, and several items contain silver probably originated in Macedonia. The set of silver items was found to be heteregenous as composition and microstructure, and corrosion-related elements could be also identified in the X-Ray maps.
BAM line is multipurpose high-energy beamline. To extend studies of multicomponent alloys using EXAFS we perform own research and user experiments requiring multiedge spectroscopy, high-temperature and chemically aggressive sample environments. Our study of multicomponent alloys and high-entropy alloys open new perspectives in understanding their reactivity, corrosion, phase transformations and local ordering.
Strahlenverfahren in Kombination - ein Werkzeug für Analyse und Zertifizierung von Feststoffen
(2002)
For quantitative SRXRF measurements the angle of incidence of the incoming X-ray beam is an important factor. When the sample is focused by a long-range-microscope, the determination of the angle can be automatized using a simple algorithm. This was developed to improve the orientation of especially round or ornate samples. As a side effect the three dimensional surface can be reconstructed, too.
Synchrotron radiation sources with their unique properties in terms of intensity, polarization and adjustability offer a wide range of possibilities in materials research. A basic introduction about the creation and special properties of synchrotron radiation will be given. Examples of current work at BAMline, the high-energy measuring facility of the Federal Institute for Materials Research and Testing at the synchrotron BESSY, are used to illustrate the possibilities and limitations of existing measuring methods.
Synchrotron-induced X-ray fluorescence (Sy-XRF) analysis was used to study the chemical composition of precious Renaissance silverpoint drawings. Drawings by famous artists such as Albrecht Dürer (14711528) and Jan van Eyck (approximately 13951441) must be investigated non-destructively. Moreover, extremely sensitive synchrotron- or accelerator-based techniques are needed since only small quantities of silver are deposited on the paper. New criteria for attributing these works to a particular artist could be established based on the analysis of the chemical composition of the metal points used. We illustrate how analysis can give new art historical information by means of two case studies. Two particular drawings, one of Albrecht Dürer, showing a profile portrait of his closest friend, Willibald Pirckheimer (1503), and a second one attributed to Jan van Eyck, showing a Portrait of an elderly man, often named Niccolò Albergati, are the object of intense art historical controversy. Both drawings show inscriptions next to the figures. Analyses by Sy-XRF could reveal the same kind of silverpoint for the Pirckheimer portrait and its mysterious Greek inscription, contrary to the drawing by Van Eyck where at least three different metal points were applied. Two different types of silver marks were found in this portrait. Silver containing gold marks were detected in the inscriptions and over-subscriptions. This is the first evidence of the use of gold points for metal point drawings in the Middle Ages.
New analyses of a series of very rare silverpoint drawings that were executed by Rembrandt Harmensz. van Rijn (16061669) which are kept today in the Kupferstichkabinett (Museum of Prints and Drawings) of the State Museums of Berlin are reported here. Analysis of these drawings requires particular attention because the study has to be fully non-destructive and extremely sensitive. The metal alloy on the paper does not exceed some hundreds of µg/cm². Therefore, synchrotron radiation induced X-ray fluorescence (SR-XRF) is together with external micro-proton-induced X-ray emission the only well-suited method for the analyses of metalpoint drawings. In some primary work, about 25 German and Flemish metalpoint drawings were investigated using spatially resolved SR-XRF analysis at the BAMline at BESSY. This study enlarges the existing FrenchGerman database of metalpoint drawings dating from the 15th and 16th centuries, as these Rembrandt drawings originate from the 17th century where this graphical technique was even rarer and already obsolete. It also illustrates how SR-XRF analysis can reinforce art historical assumptions on the dating of drawings and their connection.
Slicing - A New Method For Non Destructive 3D Elemental Sensitive Characterization Of Materials
(2013)
Slicing - a new method for non destructive 3D elemental sensitive characterization of materials
(2014)
Recent advances in synchrotron sources and detector technology have led to substantial improvements in spatial resolution and detection limits for X-ray fluorescence analysis (XRF). However, the non-destructive three-dimensional elemental sensitive characterization of samples remains a challenge. We demonstrate the use of the so-called 'Color X-ray Camera' (CXC) for 3D measurements for the first time. The excitation of the sample is realized with a thin sheet-beam. The stepwise movement of the sample allows getting the elemental distribution for each layer with one measurement. These layers can be combined to a full 3D dataset for each element afterwards. Since the information is collected layer by layer, there is no need to apply reconstruction techniques, which quite often are the reason for artifacts in the results achieved by computed tomography (CT). The field of applications is wide, as the 3D elemental distribution of a material contains clues to processes inside the samples from a variety of origins. The technique is of special interest and well suited for biological specimens, because their light matrix minimizes restricting absorption effects. Measurement examples of a hornet and the teeth of a Sorex araneus are shown.
Slicing - A New Method For Non Destructive 3D Elemental Sensitive Characterization Of Materials
(2013)
Slicing - A New Method For Non Destructive 3D Elemental Sensitive Characterization Of Materials
(2014)
Absorption effects in total reflection X-ray fluorescence (TXRF) analysis are important to consider, especially if external calibration is to be applied. With a color X-ray camera (CXC), that enables spatially and energy resolved XRF analysis, the absorption of the primary beam was directly visualized for mL-droplets and an array of pL-droplets printed on a Si-wafer with drop-on-demand technology. As expected, deposits that are hit by the primary beam first shade subsequent droplets, leading to a diminished XRF signal. This shading effect was quantified with enhanced precision making use of sub-pixel analysis that improves the spatial resolution of the camera. The measured absorption was compared to simulated results using three different model calculations. It was found they match very well (average deviation < 10%). Thus errors in quantification due to absorption effects can be accounted for in a more accurate manner.
Shading Effects in SR-TXRF: Calcullations and Experimental Visualization using a Color X-ray Camera
(2014)
Shading Effects in SR-TXRF: Calculations and Experimental Visualization using a Color X-ray Camera
(2014)
Orientierende Versuche zur Schwefelbestimmung in Kraftstoffen haben gezeigt, dass die Röntgenbeamline der BAM bei BESSY II geeignet ist, Schwefel auch in kleinen Konzentrationen zu bestimmen. Da das Verfahren der synchrotronstrahlungsinduzierten Röntgenfluoreszenzanalyse (SYRFA) für den Vor-Ort-Einsatz nicht geeignet ist, ist das Ziel der Untersuchungen, durch Variation von Anregungsenergie und -geometrie mögliche Quellen für systematische Fehler zu untersuchen. Durch geeignete Korrekturfaktoren kann dann die Richtigkeit der Analyseergebnisse gewährleistet werden. Das Verfahren soll dann als Alternative bzw. Ergänzung zu zerstörenden Verfahren der Schwefelanalyse Anwendung finden. Damit wird ein Beitrag zur künftigen Herstellung zertifizierter Referenzmaterialien (ZRM) geleistet.
Naturwissenschaftler arbeiten mit Archäologen, Kunsthistorikern und Restauratoren zusammen, um Materialinformationen über Kunstwerke mit den Erkenntnissen aus Altertumsforschung, Kunstgeschichte und Denkmalpflege zu verbinden. Röntgenfluoreszenz und Röntgenemission sind die Methoden der Wahl, wenn wertvolle und fragile Objekte zerstörungsfrei zu untersuchen sind.
In a color X-ray camera spatial resolution is achieved by means of a polycapillary optic conducting X-ray photons from small regions on a sample to distinct energy dispersive pixels on a CCD matrix. At present, the resolution limit of color X-ray camera systems can go down to several microns and is mainly restricted by Pixel dimensions. The recent development of an efficient subpixel resolution algorithm allows a release from pixel size, limiting the resolution only to the quality of theoptics. In this work polycapillary properties that influence the spatial resolution are systematized and assessed both theoretically and experimentally. It is demonstrated that with the current technological Level reaching one micron resolution is challenging, but possible.
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.
X-ray fluorescence imaging is a well-established tool in materials characterization. In this work, we present the adaption of coded aperture imaging to full-field X-ray fluorescence imaging at the synchrotron. Coded aperture imaging has its origins in astrophysics, and has several advantages: Coded apertures are relatively easy to fabricate, achromatic, allow a high photon throughput, and high angular acceptance. Coded aperture imaging is a two-step-process, consisting of the measurement process and a reconstruction step. Different programs have been written, for the raytracing/forward projection and the reconstruction. Experiments with coded aperture in combination with a Color X-ray Camera and an energy-dispersive area detector, have been conducted at the BAMline. Measured samples were successfully reconstructed, and gave a 9.1-fold increase in count rate compared to a polycapillary optic.
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 (HAuCl4). 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 µL. 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.
A layer of Sb atoms, implanted with an energy of 400 keV and a nominal dose of 5×1016 atoms/cm2 into a high purity silicon wafer, was certified for its areal density (atoms/cm2) using Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA) and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and for its isotope ratio using INAA and ICP-IDMS. Excellent agreement between the results of the different independent methods was found. In the present work, the measurements of the homogeneity of the areal density of Sb, previously determined with RBS in spots having 1 mm diameter, are improved with synchrotron X-ray fluorescence analysis: Higher precision in even smaller sample spots allows to estimate a reduced inhomogeneity of the whole batch of samples of the order of only 0.4%. Thus the uncertainty of the certified value can further be reduced. Down to fractions of a chip with 0.3×0.4 mm2 area, the areal density is now certified as (4.81±0.06)×1016 Sb atoms/cm2, where the expanded uncertainty 0.06 (coverage factor k=2) corresponds to only 1.2%. The relative merits of the different analytical methods are discussed.
Quantitative Analysis and 2D/3D Elemental Imaging of Cocoa Beans Using X‑ray Fluorescence Techniques
(2023)
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.
Quantification of energy dispersive SRXRF for the certification of reference materials at BAMline
(2010)
The certification of reference materials (CRMs) is one of the main tasks of the BAM Federal Institute for Materials Research and Testing. In this context CRMs for analytical chemistry play the dominant role. Traditionally, energy dispersive X-ray fluorescence (EDXRF) has been excluded from the final certification scheme. It has lacked the proof to be reliable enough due to peak overlapping and risks of incorrect background subtraction leading to unacceptable uncertainty and bias of the results. The development described aims at enabling ED-SRXRF to really contribute to certification by the aid of synchrotron radiation. This has been partly shown for macrocontents and has been successfully demonstrated for trace elements and thin layers. The method is based on a combination of measurements of pure elements or stoichiometric compounds as comparator materials and Monte Carlo simulations. Measurements have been performed at the BAMline, the hard X-ray beam line of the BAM at the synchrotron BESSY II in Berlin.
A new setup for fast spatially resolved measurements of elemental trace amounts under total reflection conditions using a new colour X-ray camera is described. Samples prepared on conventional total reflection X-ray fluorescence (TXRF) reflectors were measured at BESSY II synchrotron. A spatial resolution of 50 × 50 µm² was obtained, while the required time for the investigation of a 10 × 10 mm² sample is 30 seconds. The set-up is up to 350 times faster than conventional X-ray fluorescence systems for elemental traces. The major components of the X-ray camera are polycapillary optics and a pn-CCD chip with an active area of 13 × 13 mm². This area is divided into 264 × 264 pixels of 48 × 48 µm². A full X-ray spectrum with a resolution of 152 eV @ 5.9 keV and a chip temperature of 246 K is recorded for each pixel. The chip has a read-out rate of 400 Hz.
The propagation of synchrotron radiation through nanocapillary structures with channel sizes of 200 nm and periods in the micrometer size has been studied experimentally. It was shown that the propagation through individual capillary channels has a mode formation character. Furthermore it was shown that during the propagation through capillary channels the coherence of synchrotron radiation is partially conserved. Interference of beams propagating through different capillary channels is observed which leads to a periodically modulated distribution of the radiation intensity in a plane far from the exit of the structure. These investigations are of high relevance for the understanding of X-ray transmission through nanocapillaries and the appearance of wave properties at this size scale.
Imaging with X-rays is a challenging field, due to the optical properties of X-rays. The fabrication of appropriate optics is usually expensive and requires an elaborate manufacturing process. One simpler and less expensive possibility of imaging high energy radiation is coded aperture imaging, a technique well established in astrophysics and also used in nuclear medicine or radiation detection, e.g., for nuclear decommissioning. Our aim is to adapt coded aperture imaging for X-ray fluorescence spectroscopy in the nearfield. In this work we show theoretical considerations and preliminary simulations of Image formation through a coded aperture and three different reconstruction methods to prepare the experiments. We used a new mask based on an inverted modified uniformly redundant array (MURA) that could be used for the construction of a decoding mask for all investigated geometrical arrangements.
The most commonly used reconstruction method, convoluting the detected image with a Decoding mask, does not always deliver satisfactory results. This is more noticeable for small distances between the object, mask and detector. Hence, we developed two new reconstruction methods, one based on iterative algebraic optimization and another one based on a genetic algorithm. Both show good performance even in those cases where the convolution method fails. This provides a basis for further investigations of the ideal parameters for near field coded aperture imaging and refinements of the algorithms. We performed first measurements with a coded aperture at the BAMline at BESSY II and could successfully reconstruct a test object from the obtained recorded images.
Absorption effects and the impact of specimen shape on TXRF analysis has been discussed intensively. Model calculations indicated that ring shaped specimens should give better results in terms of higher counts per mass signals than filled rectangle or circle shaped specimens. One major reason for the difference in signal is shading effects. Full field micro-XRF with a color X-ray camera (CXC) was used to investigate shading, which occurs when working with small angles of excitation as in TXRF. The device allows monitoring the illuminated parts of the sample and the shaded parts at the same time. It is expected that sample material hit first by the primary beam shade material behind it. Using the CXC shading could be directly visualized for the high concentration specimens.
In order to compare the experimental results with calculation of the shading effect the generation of controlled specimens is crucial. This was achieved by 'drop on demand' technology. It allows generating uniform, microscopic deposits of elements. The experimentally measured shadings match well with those expected from calculation.
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 Fiting (LCF) 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.
Sixteen Ayyubid-Mamluk glazed pottery sherds were analyzed in order to identify and characterize the elemental composition to determine their provenance. The tested sherds were collected from the historical site of Karak Castle, southern Jordan.
Chemical analysis for the sixteen samples has been carried out using Synchrotron Radiation X-ray Fluorescence Spectrometry (SR-XRF) Technique. Furthermore, the semiquantitative analysis of the elements Fe – Cu – Zn – Br – Rb – Sr – Y – Zr – Nb – Mo – Pd – Ag – Cd and Pb has been performed for the samples based on Principal Component Analysis (PCA) and hierarchical Cluster Analysis with Bray-Curtis in order to define grouping of different glazed pottery by obtaining information on their similarity and clustering. The results of chemical analysis provided persuasive evidence that the Karak Castle pottery sherds have at least three different sources of provenance.
News from the BAMline
(2017)
News from the BAMline
(2022)
A set of ten calibration materials based on acrylonitrile-butadiene-styrene terpolymer (ABS) containing the elements Br, Pb, Cd, Cr, and Hg was produced in order to control polymer samples in regard to the restriction on the use of certain hazardous substances (RoHS) directive. The materials were produced with respect to the special demands of X-ray fluorescence analysis (XRF) and inductively coupled plasma mass spectrometry in combination with laser ablation (LA-ICP-MS).
The mass fractions of all elements were 0-1500 mg/kg and the materials were produced as granulates and solid discs with a diameter of 40 mm and thicknesses of 1, 2, and 6 mm. It could be shown that the signals measured by XRF strongly depend on the thickness of polymeric samples.
Macroscopic homogeneity was assessed with XRF measuring a total of 180 samples. The microscopic homogeneities were determined for a material with average elemental mass fractions with the aid of synchrotron radiation (SR) µ-XRF and LA-ICP-MS. Sufficient macroscopic and microscopic homogeneities for all elements could be achieved. It was observed that organic additives show a better homogeneity than oxides.
XRF and LA-ICP-MS were successfully calibrated with the new materials. Limits of detection were in the range of 0.4-22 mg/kg for XRF and 2.3-26.8 mg/kg for LA-ICP-MS. The materials are considered as candidate reference materials (RM) by the Federal Institute of Materials Research and Testing (BAM, Germany).
Although metallic nanoparticles play an important role in the area of nanotechnology, a coherent mechanistic explanation for the evolution of the particles during their chemical synthesis has not yet been provided in many cases. To gain a profound understanding of the growth mechanism of colloidal nanoparticles, new approaches using Small Angle X-Ray Scattering (SAXS) combined with X-ray absorption near-edge structure (XANES) are presented. This combination allows for insights into two prominent syntheses routes of gold nanoparticles (GNP): The 'slow' reaction using sodium citrate (30-90 min) as a reducing agent and the 'fast' reaction employing NaBH4 (within few seconds). In the first case data derived with the coupled XANES and SAXS suggests a four-step particle formation mechanism. For the second system a time resolution in the order of 100-200 ms was achieved by coupling a common laboratory SAXS instrument with a microstructured mixer, which allows data acquisition in a continuous-flow mode. The results indicate a coalescence driven growth process. Based on the capabilities to deduce the size, number and polydispersity of the particles, the results of both methods enable the development of mechanistic schemes explaining the different phases of particle formation and growth, thus providing a basis for improved control over the synthesis processes.
ML@BAMLINE
(2021)
A study regarding the possibility to use compound refractive lenses (CRLs) for X-ray absorption spectroscopy (XAS) was conducted. For XAS measurements the energy of the monochromatic incident beam has to be tuned over an energy range which is broader than the energy bandwidth of a CRL. To prove that µ-XAS with compound refractive lenses is possible, it had to be investigated how changes in the energy influence the beam parameters. This was done by tuning the energy around the nominal energy of the lens and recording images with a high resolution X-ray imaging setup. To investigate the changes in the spot size the scintillator was placed at the nominal focal distance and scans along the beam axis were performed. The effect on the photon flux of the incident beam due to absorption in the lens was investigated by performing XANES measurement on different reference materials with and without CRL. The results of these measurements using a CRL designed for 9 keV are shown and discussed.
In the determination of the provenance of gold in archaeological artifacts, trace elements are more significant than the main components. Several minute fragments of natural Carpathian gold-placer and primary-and some very small (a few milligrams) fragments of archaeological items were studied using micro Synchrotron Radiation X-Ray Fluorescence (micro SR-XRF) at the BESSY Synchrotron Facility in Berlin, Germany. The goal of the study was to identify the trace elements characterizing Carpathian gold, looking especially at Sn, Sb, Pb and Te, and to determine if the gold in the archaeological items is native or refined. Applications to the authentication and provenance of nine Dacian gold bracelets, koson coins and two Bronze Age items are presented.
Trace-elements are more significant for provenancing archaeological metallic artifacts than the main components. For gold, the most promising elements are platinum group elements (PGE), Sn, Te, Sb, Hg and Pb. Several small fragments of natural Transylvanian gold placer and primary were studied by using micro-PIXE technique at the Legnaro National Laboratory AN2000 microbeam facility, Italy and at the AGLAE accelerator, C2RMF, Paris, France and by using micro synchrotron radiation X-ray fluorescence (micro-SR-XRF) at BESSY synchrotron, Berlin, Germany. The goal of the study was to identify the trace-elements, especially Sn, Sb and Te. A spectacular application to five Dacian gold bracelets authentication is presented (Sn and Sb traces).
A set of compound refractive lenses (CRLs), mounted on a silicon wafer, was obtained from the Institut für Mikrostrukturtechnik Karlsruhe. The CRLs were characterized at the BAMline at the synchrotron BESSYII in Berlin. It could be demonstrated that beam diameters below 1 µm can be obtained. The beam size accepted by the lenses is (140 × 140) µm2, thus the intensity gain in the micrometer spot, including absorption, is about 15,000. It is possible to switch between different beam energies within a few minutes. First results of scans and the application of the lenses for MicroXANES (X-ray absorption near-edge structure) measurements are presented in this paper. Also, the possibility of MicroEXAFS (extended X-ray absorption fine structure) measurements is discussed.
Synchrotron radiation sources with their unique properties in terms of intensity, polarization and adjustability offer a wide range of possibilities in materials research. A basic introduction about the creation and special properties of synchrotron radiation will be given. Examples of current work at BAMline, the high-energy measuring facility of the Federal Institute for Materials Research and Testing at the synchrotron BESSY, are used to illustrate the possibilities and limitations of existing measuring methods. It will be shown how the formation of corrosion layers can be tracked, how the abrasion of implants leads to the introduction of heavy metals into the surrounding bone matrix and how the detection of smallest impurities in gold is possible by optimizing the measuring conditions. Finally, an outlook at the hardware and software developments to be expected in the coming years is given.
Various applications for artificial intelligence in the context of spectroscopy will be presented. in particular, examples from BAMline will be presented. After a short introduction to synchrotron radiation, artificial intelligence algorithms for the quantification of X-ray fluorescence measurement are discussed. In the second example, information retrieval by natural language processing is discussed.
In materials science, traditional techniques for analyzing layered structures are essential for obtaining information about local structure, electronic properties and chemical states. While valuable, these methods often require high vacuum environments and have limited depth profiling capabilities. The grazing exit x-ray absorption near-edge structure (GE-XANES) technique addresses these limitations by providing depth-resolved insight at ambient conditions, facilitating in situ material analysis without special sample preparation. However, GE-XANES is limited by long data acquisition times, which hinders its practicality for various applications. To overcome this, we have incorporated Bayesian optimization (BO) into the GE-XANES data acquisition process. This innovative approach potentially reduces measurement time by a factor of 50. We have used a standard GE-XANES experiment, which serve as reference, to validate the effectiveness and accuracy of the BO-informed experimental setup. Our results show that this optimized approach maintains data quality while significantly improving efficiency, making GE-XANES more accessible to a wider range of materials science applications.
In X-ray fluorescence (XRF), a sample is excited with X-rays, and the resulting characteristic radiation is detected to detect elements quantitatively and qualitatively. Quantification is traditionally done in several steps:
1. Normalization of the data
2. Determination of the existing elements
3. Fit of the measured spectrum
4. Calculation of concentrations with fundamental parameters / MC simulations / standard based
The problem with standard based procedures is the availability of corresponding standards. The problem with the calculations is that the measured intensities for XRF measurements are matrix-dependent. Calculations must, therefore, be performed iteratively (= time consuming) in order to determine the chemical composition.
First experiments with gold samples have shown the feasibility of machine learning based quantification in principle. A large number of compositions were simulated (> 10000) and analyzed with a deep learning network. For first experiments, an ANN (Artificial Neural Network) with 3 hidden layers and 33x33x33 neurons was used. This network learned the mapping of spectra to concentrations using supervised learning by multidimensional regression. The input layer was formed by the normalized spectrum, and the output layer directly yielded the searched values. The applicability for real samples was shown by measurements on certified reference materials.
In this talk I’ll describe the use of artificial neural networks (ANN) for quantifying X-ray fluorescence (XRF) measurements. The main idea of this talk is to give an overview of the process needed to generate a model that can then be applied to a specific problem.
In XRF, a sample is excited with X-rays and the resulting characteristic radiation is detected to determine elements quantitatively and qualitatively. This is traditionally done in several time-consuming steps. I’ll show the possibilities and problems of using a neural network to realise a "one-click" quantification. This includes generating training data using Monte Carlo simulation and augmenting the existing data set with an ANN to generate more data. The search for the optimal hyperparameters, manually and automatically, is also described. For the case presented, we were able to train a network with a mean absolute error of 0.1% by weight for the synthetic data and 0.7% by weight for a set of experimental data obtained with certified reference materials.
In this work, we describe the use of artificial neural networks for the quantification of X-ray fluorescence measurements. The training data were generated using Monte Carlo simulation, which avoided the use of adapted reference materials. The extension of the available data set by means of an ANN to generate additional data was demonstrated. Particular emphasis was put on the comparability of simulated and experimental data and how the influence of deviations can be reduced. The search for the optimal hyperparameter, manual and automatic, is also described. For the presented case, we were able to train a network with a mean absolute error of 0.1 weight percent for the synthetic data and 0.7 weight percent for a set of experimental data obtained with certified reference materials.