Combined X-ray Fluorescence Research Articles

Development of a combined XRF/XPS surface-analysis system for the surface-layer quantification of 28Si spheres

<p class="Abstract">To achieve a new kilogram definition using the X-ray crystal density method, the Center for Measurement Standards, Industrial Technology Research Institute in Taiwan has established the combined XRF (X-ray fluorescence)/XPS (X-ray photoelectron spectroscopy) surface analysis system for the quantitative surface-layer analysis of Si spheres. The surface layer of a Si sphere is composed primarily of an oxide layer, carbonaceous contamination and physisorbed/chemisorbed water. This newly combined instrument has been implemented to measure the XRF for the direct determination of the mass deposition of oxygen (ng/cm<sup>2</sup>) with a calibrated silicon drift detector and the XPS for the ratio between the elements (O, Si, C) and composition identification. These two complementary methods of X-ray metrology allow an accurate determination of the surface-layer mass of the Si sphere. In this paper, the construction of a combined XRF/XPS surface-analysis system is reported, including the surface characterisation method, the assembly of parts of the load-lock chamber and ultra-high-vacuum analysis chamber, the vacuum-system design, hardware integration and the intended research on surface-layer measurement. It is anticipated that the measured surface-layer mass will be combined with the core mass of the Si sphere.</p>

Quantitative depth-profile analysis of transition metal nitride materials with combined grazing-incidence X-ray fluorescence and X-ray reflectometry analysis

Refractory transition metal nitrides are attracting attention in many microelectronics research and development fields. Their different applications and desired performances require a precise control of the film thickness and elemental depth profile. This information can be non-destructively obtained combining Grazing-Incidence X-ray Fluorescence (GIXRF) and X-ray Reflectometry (XRR) analysis. GIXRF-XRR joint analysis can be performed following a reference-free approach, which requires the knowledge of the whole experimental system. However, such a rigorous metrological approach cannot be easily applied to in-lab or in-fab tools due to the difficulty to access the various experimental set-up parameters, therefore another approach is needed.In this paper, we used a reference-based method consisting in the use of known standard samples, close in composition and structure with respect to the samples to analyse, to deduce the key parameters of the instrumental setup. These are then used to perform quantitative GIXRF-XRR combined analysis of the samples of interest. We applied this method to titanium tungsten nitride thin films elaborated by Physical Vapour Deposition (PVD). Our results show that the reference-based method, using carefully determined instrumental functions, can meet the requirement for both qualitative and quantitative depth-profiling analysis. The reference-based approach result easier to implement into labs and fabs than the reference-free method.

Design of a combined X-ray fluorescence Computed Tomography (CT) and photon-counting CT table-top imaging system

This paper demonstrates the capability of a table-top x-ray imaging system to simultaneously image a small animal phantom loaded with Gd and Au contrast agents with photon-counting computed tomography (PCCT) and x-ray fluorescence CT (XFCT). Our table-top system consisted of a diagnostic x-ray tube, translation and rotation stages, a 330 μm-pitch cadmium zinc telluride (CZT) photon-counting detector with six energy bins, and two CdTe spectrometers which detected fluorescent x-rays in 0.5 keV bins. The energy bin thresholds on the CZT detector matched the contrast agent K-edge energies, enabling K-edge PCCT. A 3 cm-diameter phantom containing vials of 1% and 5% Gd and Au solutions by weight, including a mixed 1% Gd/Au vial, was scanned with 0.5 mm Cu-filtered 120 kVp x-rays at 2 mA. A pencil beam geometry was used with 33 translation and 30 rotation steps to form XFCT and K-edge PCCT images. A cone beam geometry with 180 rotation steps was used to form higher-resolution K-edge PCCT images. Three mice were each injected post-mortem with 0.2 mL of 5% Gd, Au, or mixed Gd/Au solutions in the upper torso and imaged similarly to the phantom. The lowest detectable concentration based on the Rose criterion for Gd and Au phantom data was 0.75% and 3.0% for XFCT, 0.81% and 0.82% for pencil beam K-edge PCCT, and 0.79% and 1.5% for cone beam K-edge PCCT. However, cone beam K-edge PCCT images have a much higher spatial resolution than the pencil beam images. The mixed 1% Gd/Au signal was diminished in the K-edge PCCT phantom images. Preliminary mouse images of Gd and Au among the imaging techniques were similar in image quality as the phantom images. This is the first demonstration of simultaneously-acquired XFCT and PCCT of both Gd and Au in a phantom on a table-top imaging system. On our system, cone beam PCCT is best for imaging Gd, pencil beam PCCT is best for imaging Au, and pencil beam XFCT is better suited toward resolving mixtures of contrast agents.

Combined micro X-ray fluorescence and micro computed tomography for the study of extraterrestrial volcanic rocks. The case of North West Africa (NWA) 8657: A shergottite martian meteorite

The combined potentiality of benchtop micro X-ray fluorescence spectroscopy (μ-XRF) and micro computed tomography (μ-CT) has been applied to describe microstructures, type and distribution of mineralogical phases as well as geological constraints on the history of the North West Africa (NWA) 8657 shergottite Martian meteorite. The 3D rendering of the sample was used to compute its vesiculation, infer the presence of cracks and reveal different shapes in its crystal habits including subhedral pyroxene phases and rounded sulphide and/or sulphates minerals. Phase discrimination was achieved by comparing chemical information about element distribution with mineral classes segmented as a function of their relative density. In particular, the relationships between the plagioclase/maskelynite phase and other minerals such as Ca-phosphates, the chemical zoning of Ca-pyroxenes and maskelynite and the presence of S-bearing phases in the form of K-sulphates and Fe-sulphides were revealed, which allowed reconstructing satisfactorily meteorite history. The successful performance of the combined approach used in this work shows promising for further application to other types of meteorites.

Cryo-nanoimaging of Single Human Macrophage Cells: 3D Structural and Chemical Quantification.

X-ray microscopy is increasingly used in biology, but in most cases only in a qualitative way. We present here a 3D correlative cryo X-ray microscopy approach suited for the quantification of molar concentrations and structure in native samples at nanometer scale. The multimodal approach combines X-ray fluorescence and X-ray holographic nanotomography on "thick" frozen-hydrated cells. The quantitativeness of the X-ray fluorescence reconstruction is improved by estimating the self-attenuation from the 3D holography reconstruction. Applied to complex macrophage cells, we extract the quantification of major and minor elements heavier than phosphorus, as well as the density, in the different organelles. The intracellular landscape shows remarkable elemental differences. This novel analytical microscopy approach will be of particular interest to investigate complex biological and chemical systems in their native environment.

Multimodal X-ray imaging of nanocontainer-treated macrophages and calcium distribution in the perilacunar bone matrix

Studies of biological systems typically require the application of several complementary methods able to yield statistically-relevant results at a unique level of sensitivity. Combined X-ray fluorescence and ptychography offer excellent elemental and structural imaging contrasts at the nanoscale. They enable a robust correlation of elemental distributions with respect to the cellular morphology. Here we extend the applicability of the two modalities to higher X-ray excitation energies, permitting iron mapping. Using a long-range scanning setup, we applied the method to two vital biomedical cases. We quantified the iron distributions in a population of macrophages treated with Mycobacterium-tuberculosis-targeting iron-oxide nanocontainers. Our work allowed to visualize the internalization of the nanocontainer agglomerates in the cytosol. From the iron areal mass maps, we obtained a distribution of antibiotic load per agglomerate and an average areal concentration of nanocontainers in the agglomerates. In the second application we mapped the calcium content in a human bone matrix in close proximity to osteocyte lacunae (perilacunar matrix). A concurrently acquired ptychographic image was used to remove the mass-thickness effect from the raw calcium map. The resulting ptychography-enhanced calcium distribution allowed then to observe a locally lower degree of mineralization of the perilacunar matrix.

Tracking the first bronze metallurgists of Western Europe: combined use-wear analysis and X-ray fluorescence synchrotron spectroscopy of a stone toolkit from Ploneour-Lanvern (Brittany)

At the turn of the second millennium BC in Europe, the development of copper and bronze metallurgies stimulated major economic shifts, with the emergence of elites and far-reaching diffusion networks. However, the exact organization, techniques, processes, and equipment employed in this early copper and bronze metallurgy still remain poorly understood. In this context, our aim has been to identify the first stone toolkits used by Early Bronze Age metallurgists on a site in western Brittany (France), a region connected to the so-called Atlantic complex. The combination of use-wear analysis and Synchrotron X-ray fluorescence spectroscopy (XRF) imaging highlights a correlation between the distribution of diagnostic use-wear traces (smoothing and micropolishes) related to metal ore processing or metal objet shaping and elemental residues of copper and zinc. These results demonstrate the existence of copper ore processing in western Brittany during the Early Bronze Age (2200–1900 BC). They also highlight the diversity of the stone tools involved in metal production. Finally, this comprehensive methodology underlines the potential of functional analysis of macrolithic tools to reveal the existence of metal production. This is particularly relevant for archeological sites where the structures of metallurgical production are barely visible and often unrecognizable and where metallic objects are rare due to their intensive recycling and diffusion.

Combined micro X-ray absorption and fluorescence spectroscopy to map phases of complex systems: the case of sphalerite

Combining micro-X-ray absorption spectroscopy (μXAS) and micro-X-ray fluorescence spectroscopy (μXRF) is a promising approach for the investigation of complex multi-phase systems. In this work, we have employed this approach to investigate natural sphalerite, the most common form of Zinc Sulfide. Spatially resolved elemental distribution maps of common 3d metal atoms (Zn, Cu, Ni, Co, and Fe) are superimposed with chemical speciation and structural parameter maps in order to understand the sphaleriteore-formation process and metamorphosis. Chemical speciation and structural parameters have been obtained by analyzing the μXAS spectra collected in several representative points of the sample, after μXRF mapping. In the present case, this X-ray based approach has permitted to determine the spatial distribution of the Zn species in sphalerite. The presence of two main zincite and smithsonite inclusions has been established, with the latter located close to copper impurity center. Since copper is known to remarkably reduce the corrosion resistance of zinc, resulting in the formation of carbonate as the corrosion product, this implies a possible role of Cu in the growth of the carbonate inclusions. The results obtained highlight the efficiency of this method in univocally identifying the spatial distribution of phases in complex systems, thanks to the simultaneous access to complementary information.

Synchrotron Radiation Research and Analysis of the Particulate Matter in Deep Ice Cores: An Overview of the Technical Challenges

Airborne dust extracted from deep ice core perforations can provide chemical and mineralogical insight into the history of the climate and atmospheric conditions, with unrivalled temporal resolution, time span and richness of information. The availability of material for research and the natural complexity of the particulate, however, pose significant challenges to analytical methods. We present the developments undertaken to optimize the experimental techniques, materials and protocols for synchrotron radiation-based analysis, in particular for the acquisition of combined Synchrotron Radiation X-Ray Fluorescence and X-ray Absorption Spectroscopy data.

Provenance of uranium particulate contained within Fukushima Daiichi Nuclear Power Plant Unit 1 ejecta material

Here we report the results of multiple analytical techniques on sub-mm particulate material derived from Unit 1 of the Fukushima Daiichi Nuclear Power Plant to provide a better understanding of the events that occurred and the environmental legacy. Through combined x-ray fluorescence and absorption contrast micro-focused x-ray tomography, entrapped U particulate are observed to exist around the exterior circumference of the highly porous Si-based particle. Further synchrotron radiation analysis of a number of these entrapped particles shows them to exist as UO2—identical to reactor fuel, with confirmation of their nuclear origin shown via mass spectrometry analysis. While unlikely to represent an environmental or health hazard, such assertions would likely change should break-up of the Si-containing bulk particle occur. However, more important to the long-term decommissioning of the reactors at the FDNPP (and environmental clean-upon), is the knowledge that core integrity of reactor Unit 1 was compromised with nuclear material existing outside of the reactors primary containment.

New Insight into Hellenistic and Roman Cypriot Wall Paintings: An Exploration of Artists’ Materials, Production Technology, and Technical Style

A recent scientific investigation on Hellenistic and Roman wall paintings of funerary and domestic contexts from Nea (‘New’) Paphos, located in the southwest region of Cyprus, has revealed new information on the paintings’ constituent materials, their production technology and technical style of painting. Nea Paphos, founded in the late 4th century BC, became the capital of the island during the Hellenistic period (294–58 BC) and developed into a thriving economic center that continued through the Roman period (58 BC–330 AD). A systematic, analytical study of ancient Cypriot wall paintings, excavated from the wealthy residences of Nea Paphos and the surrounding necropoleis, combining complementary non-invasive, field-deployable characterization techniques, has expanded the scope of analysis, interpretation and access of these paintings. The results from in situ analyses, combining X-ray fluorescence (XRF) and fiber-optic reflectance spectroscopy (FORS), forensic imaging in reflectance and luminescence, and digital photomicrography, were informative on the raw materials selection, application technique(s) and extent of paintings beyond the visible. Data collected through the integration of these techniques were able to: (1) show an intricate and rich palette of pigments consisting of local and foreign natural minerals and synthetic coloring compounds applied pure or in mixtures, in single or multiple layers; (2) identify and map the spatial distribution of Egyptian blue across the surface of the paintings, revealing the extent of imagery and reconstructing iconography that was no longer visible to the naked eye; and (3) visualize and validate the presence of Egyptian blue to delineate facial contours and flesh tone shading. This innovation and technical characteristic in the manner of painting facial outlines and constructing chiaroscuro provides a new insight into the artistic practices, inferring artists/or workshops’ organization in Cyprus during the Roman period.

Three-Dimensional Correlative Imaging of a Malaria-Infected Cell with a Hard X-ray Nanoprobe.

Benefiting from the recent advances of synchrotron X-ray nanoprobes, we demonstrate three-dimensional (3D) correlative nanoimaging on malaria-infected human red blood cells. By combining X-ray fluorescence tomography and phase contrast nanotomography on the same cell with sub-100 nm pixel size, we establish a routine workflow from the data acquisition, data processing, to tomographic reconstruction. We quantitatively compare the elemental volumes obtained with different reconstruction methods, with the total variation minimization giving the most satisfactory results. We reveal elemental correlations in different cell compartments more reliably on reconstructions as opposed to 2D projections. Finally, we determine for the first time the 3D mass fraction maps of multiple elements at the subcellular level. The estimated total number of Fe atoms and the total mass of red blood cells show very good agreement with previously reported values.

X-ray fluorescence imaging

Over the past two decades, numerous X-ray micro-beam studies have been published addressing the nondestructive investigation of chemical element distribution in condensed heterogeneous media. Based on this literature, some aspects of the field are discussed in this paper, including X-ray focusing methods and various elemental imaging techniques: scanning and confocal X-ray fluorescence microscopy, full-field X-ray fluorescence microscopy, X-ray fluorescence tomography, and prospects for combining X-ray fluorescence imaging with other physical methods rested on using synchrotron radiation.

COUPLING LITHIC SOURCING WITH LEAST COST PATH ANALYSIS TO MODEL PALEOINDIAN PATHWAYS IN NORTHEASTERN NORTH AMERICA

Projections of Paleoindian range mobility in the late Pleistocene are typically inferred from straight-line distances between toolstone sources and sites where artifacts of these raw materials have been found. Often, however, these sourcing assessments are not based on geologic analysis, raising the issue of correct source ascription. If sites of similar age can be linked to a toolstone source through geologic study, and direct procurement of toolstone can be inferred, geographic information systems (GIS) modeling of travel routes between the source and those sites can reveal route segments of annual rounds and aspects of landscape use. In the Hudson Valley of eastern New York, Paleoindian peoples exploited Normanskill chert outcrops for toolstone during the late Pleistocene. Here, we combine X-ray fluorescence sourcing results that link Normanskill chert artifacts at Paleoindian sites to the West Athens Hill source outcrop in the Hudson Valley with GIS least cost path analysis to model seasonal pathways of late Pleistocene peoples in northeastern North America.

Characterization of breast tissues combining x-ray fluorescence and scattering spectroscopy: A Monte Carlo computational study

The study of spectroscopic techniques that allow obtaining information about breast tissues can be useful for understanding the relationship between tissue composition and the carcinogenic process. In addition, the study of these techniques can serve as a basis for the development of new imaging techniques to complement the diagnosis of breast cancer. Therefore, the objective of the present work is to study by Monte Carlo computational simulation the possibility of mapping breast tissues samples, combining x-ray fluorescence and scattering techniques, exploring the complementarity and ability of these techniques for obtaining morphological and chemical information of the samples.Fluorescence spectra obtained by the simulations were used for mapping the spatial distributions of trace elements (Ca, Fe Cu, Zn) in the simulated sample. In addition, the scattering spectra were used to produce images based on Rayleigh to Compton scattering ratio (R/C) and on the full width at half maximum (FWHM) of the Compton scattering spectrum.The results showed that the fluorescence and scattering techniques are complementary and can produce images that allow distinguishing between the various breast tissues regions inside the sample. Fluorescence technique showed to be sensitive to the typical concentrations of the investigated trace elements while the R/C and FWHM techniques allowed mapping spatial information related to the effective atomic number, being particularly sensitive to differences of oxygen and carbon percentage of the tissues. Finally, the results showed that as higher the incident energy as higher the contrast of the R/C and FWHM scattering images. When compared to conventional transmission images, R/C images presented better contrast for incident energies above ≈ 23 keV while FWHM images presented lower contrast for all the investigated energy range.

Integrated X-ray fluorescence and diffuse visible-to-near-infrared reflectance scanner for standoff elemental and molecular spectroscopic imaging of paints and works on paper

Prior studies have shown the improved ability to identify artists’ pigments by combining results from X-ray fluorescence (XRF), which provides elemental information, with reflectance spectroscopy in the visible to near infrared (400–1000 nm) that provides information on electronic transitions. Extending the spectral range of reflectance spectroscopy into the UV, 350–400 nm, allows identification of several white pigments since their electronic transitions occur in this region (e.g., zinc white and rutile and anatase forms of titanium white). Extending the range further into the infrared, out to 2500 nm, provides information on vibrational transitions of various functional groups, such as hydroxyl, carbonate, and methyl groups. This allows better identification of mineral-based pigments and some paint binders. The combination of elemental information with electronic and vibrational transitions provides a more robust method to identify artists’ materials in situ. The collection of both sets of spectral information across works of art, such as paintings and works on paper, allows generating a more complete map of artists’ materials. Here, we describe a 2-D scanner that simultaneously collects XRF spectra and reflectance spectra from 350 to 2500 nm across the surfaces of works of art. The scanner consists of a stationary, single pixel XRF spectrometer and fiber optic reflectance spectrometer along with a 2-D position-controlled easel that moves the artwork in front of the two detection systems. The dual-mode scanner has been tested on a variety of works of art from illuminated manuscripts (0.1 × 0.1 m2) to paintings as large as 1.7 × 1.9 m2. The scanner is described and two sets of results are presented. The first is the XRF scanning of a large warped panel painting by Andrea del Sarto titled Charity. The second is a combined XRF and reflectance scan of Georges Seurat’s painting titled Haymakers at Montfermeil. The XRF was collected at 1 mm spatial sampling and the reflectance spectral data at 3 mm. Combining the results from the data sets was found to enhance the identification of pigments as well as yield distribution maps, in spite of the relatively low reflectance spatial sampling. The elemental and reflectance maps allowed the identification and mapping of lead white, cobalt blue, viridian, ochres, and likely chrome yellow. The maps also provide information on the mixing of pigments. While the reflectance image cube has 10–20× larger spatial samples than desired, the elimination of having to use two hyperspectral cameras to cover the range from 400 to 2500 nm makes for a low cost dual modality scanner.

Determination of coal ash content by the combined x-ray fluorescence and scattering spectrum.

An alternative method is proposed for the determination of the inorganic constituent mass fraction (ash) in solid fuel by the ratio of Compton and Rayleigh X-ray scattering peaks IC/IR subject to the iron fluorescence intensity. An original X-ray optical scheme with a Ti/Mo (or Sc/Cu) double-layer secondary radiator allows registration of the combined fluorescence-and-scattering spectrum at the specified scattering angle. An algorithm for linear calibration of the Compton-to-Rayleigh IC/IR ratio is proposed which uses standard samples with two certified characteristics: mass fractions of ash (Ad) and iron oxide (WFe2O3 ). Ash mass fractions have been determined for coals of different deposits in the wide range of Ad from 9.4% to 52.7% mass and WFe2O3 from 0.3% to 4.95% mass. Due to the high penetrability of the probing radiation with energy E > 17 keV, the sample preparation procedure is rather simplified in comparison with the traditional method of Ad determination by the sum of fluorescence intensities of all constituent elements.

Archaeometric analysis for provenance and content of roman amphorae from the site of SA mesquida (Mallorca, Spain)

This paper presents the results of an inorganic and organic approach to Roman amphorae found at the rural Roman site of Sa Mesquida (Mallorca). A set of amphorae were discovered in some rooms of the earlier phases of the villa. These amphorae were assigned to a general Tarraconensian and Italic provenance on a macroscopic level. In order to verify this and to accurately determine the provenance an archaeometric characterization was carried out on twelve amphorae. The analytical approach combined wavelength dispersive X-ray fluorescence (WD-XRF) for the chemical analysis, as well as powder x-ray diffraction (XRD) and optical microscopy by thin-section analysis (OM) for the mineralogical and petrographic characterization. In addition, organic residue analysis by gas-chromatography mass spectrometry (GC-MS) was applied to investigate the content of some of the amphorae for which wine was suggested on an archaeological basis. The results have allowed for a better provenance determination identifying some amphorae from specific workshops or micro-regions within ancient Tarraconensis, as well as a better definition of the Italic materials. The organic analysis has confirmed the presence of wine in the analysed samples.

Single cell versus large population analysis: cell variability in elemental intracellular concentration and distribution.

The quantification of elemental concentration in cells is usually performed by analytical assays on large populations missing peculiar but important rare cells. The present article aims at comparing the elemental quantification in single cells and cell population in three different cell types using a new approach for single cells elemental analysis performed at sub-micrometer scale combining X-ray fluorescence microscopy and atomic force microscopy. The attention is focused on the light element Mg, exploiting the opportunity to compare the single cell quantification to the cell population analysis carried out by a highly Mg-selective fluorescent chemosensor. The results show that the single cell analysis reveals the same Mg differences found in large population of the different cell strains studied. However, in one of the cell strains, single cell analysis reveals two cells with an exceptionally high intracellular Mg content compared with the other cells of the same strain. The single cell analysis allows mapping Mg and other light elements in whole cells at sub-micrometer scale. A detailed intensity correlation analysis on the two cells with the highest Mg content reveals that Mg subcellular localization correlates with oxygen in a different fashion with respect the other sister cells of the same strain. Graphical abstract Single cells or large population analysis this is the question!

Inert Gas Deactivates Protein Activity by Aggregation

Biologically inert gases play important roles in the biological functionality of proteins. However, researchers lack a full understanding of the effects of these gases since they are very chemically stable only weakly absorbed by biological tissues. By combining X-ray fluorescence, particle sizing and molecular dynamics (MD) simulations, this work shows that the aggregation of these inert gases near the hydrophobic active cavity of pepsin should lead to protein deactivation. Micro X-ray fluorescence spectra show that a pepsin solution can contain a high concentration of Xe or Kr after gassing, and that the gas concentrations decrease quickly with degassing time. Biological activity experiments indicate a reversible deactivation of the protein during this gassing and degassing. Meanwhile, the nanoparticle size measurements reveal a higher number of “nanoparticles” in gas-containing pepsin solution, also supporting the possible interaction between inert gases and the protein. Further, MD simulations indicate that gas molecules can aggregate into a tiny bubble shape near the hydrophobic active cavity of pepsin, suggesting a mechanism for reducing their biological function.