Calculating absorption dose when X-ray irradiation modifies material quantity and chemistry

X-ray absorption is a sensitive and versatile tool for chemical speciation. However, when high doses are used, the absorbed energy can change the composition, amount and structure of the native material, thereby changing the aspects of the absorption process on which speciation is based. How can one calculate the dose when X-ray irradiation affects the chemistry and changes the amount of the material? This paper presents an assumption-free approach which can retrieve from the experimental data all dose-sensitive parameters – absorption coefficients, composition (elemental molecular units), material densities – which can then be used to calculate accurate doses as a function of irradiation. This approach is illustrated using X-ray damage to a solid film of a perfluorosulfonic acid fluoropolymer in a scanning transmission soft X-ray microscope. This new approach is compared against existing dose models which calculate the dose by making simplifying assumptions regarding the material quantity, density and chemistry. While the detailed measurements used in this approach go beyond typical methods to experimental analytical X-ray absorption, they provide a more accurate quantitation of radiation dose, and help to understand mechanisms of radiation damage.

Download Full-text

Analysis of Cr(VI) Bioremediation by Citrobacter freundii Using Synchrotron Soft X-ray Scanning Transmission X-ray Microscopy

Quantum Beam Science ◽

10.3390/qubs5040028 ◽

2021 ◽

Vol 5 (4) ◽

pp. 28

Author(s):

Amith G. Anil ◽

Sufal Swaraj ◽

Sankaran Subramanian ◽

Praveen C. Ramamurthy

Keyword(s):

Chemical Speciation ◽

Time Lapse ◽

Gram Negative Bacteria ◽

Citrobacter Freundii ◽

Chemical Mapping ◽

X Ray ◽

Biosorption Process ◽

Scanning Transmission ◽

X Ray Absorption ◽

Absorption Features

Scanning transmission X-ray microscopy (STXM) was utilized for analysing the bioremediation of Cr(VI) by Citrobacter freundii, a species of gram-negative bacteria. The biosorption and bioreduction processes were analysed by the chemical mapping of cells biosorbed at different concentrations of Cr(VI). STXM spectromicroscopy images were recorded at O K-edge and Cr L-edge. A thorough analysis of the X-ray absorption features corresponding to different oxidation states of Cr in the biosorbed cell indicated the coexistence of Cr(III) and Cr(VI) at higher concentrations. This signifies the presence of partially reduced Cr(VI) in addition to biosorbed Cr(VI). In addition, the Cr(III) signal is intense compared with Cr(VI) at different regions of the cell indicating excess of reduced Cr. Speciation of adsorbed Cr was analysed for the spectral features of biosorbed cell and comparison with Cr standards. Analysis of absorption onset, L3/L2 ratio and absorption fine structure concludes that adsorbed Cr is predominantly present as Cr(III) hydroxide or oxyhydroxide. The evolution of absorption features in the duration of biosorption process was also studied. These time lapse studies depict the gradual decrement in Cr(VI) signal as biosorption proceeds. A strong evidence of interaction of Cr with the cell material was also observed. The obtained results provide insights into the biosorption process and chemical speciation of Cr on the cells.

Download Full-text

Chemical and orientational imaging of polymeric samples

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168074 ◽

1994 ◽

Vol 52 ◽

pp. 68-69

Author(s):

H. Ade ◽

B. Hsiao ◽

G. Mitchell ◽

E. Rightor ◽

A. P. Smith ◽

...

Keyword(s):

Ethylene Terephthalate ◽

National Laboratory ◽

Brookhaven National Laboratory ◽

Carbonyl Groups ◽

Aromatic Rings ◽

Edge Structure ◽

X Ray ◽

Scanning Transmission ◽

Polymeric Samples ◽

X Ray Absorption

We have used the Scanning Transmission X-ray Microscope at beamline X1A (X1-STXM) at Brookhaven National Laboratory (BNL) to acquire high resolution, chemical and orientation sensitive images of polymeric samples as well as point spectra from 0.1 μm areas. This sensitivity is achieved by exploiting the X-ray Absorption Near Edge Structure (XANES) of the carbon K edge. One of the most illustrative example of the chemical sensitivity achievable is provided by images of a polycarbonate/pol(ethylene terephthalate) (70/30 PC/PET) blend. Contrast reversal at high overall contrast is observed between images acquired at 285.36 and 285.69 eV (Fig. 1). Contrast in these images is achieved by exploring subtle differences between resonances associated with the π bonds (sp hybridization) of the aromatic groups of each polymer. PET has a split peak associated with these aromatic groups, due to the proximity of its carbonyl groups to its aromatic rings, whereas PC has only a single peak.

Download Full-text

Spatially Resolved Characterization of Biogenic Manganese Oxide Production within a Bacterial Biofilm

Applied and Environmental Microbiology ◽

10.1128/aem.71.3.1300-1310.2005 ◽

2005 ◽

Vol 71 (3) ◽

pp. 1300-1310 ◽

Cited By ~ 94

Author(s):

Brandy Toner ◽

Sirine Fakra ◽

Mario Villalobos ◽

Tony Warwick ◽

Garrison Sposito

Keyword(s):

Careful Consideration ◽

Bacterial Biofilm ◽

Bacterial Cells ◽

X Ray ◽

Spatially Resolved ◽

Nexafs Spectroscopy ◽

Promising Tool ◽

Scanning Transmission ◽

X Ray Absorption

ABSTRACT Pseudomonas putida strain MnB1, a biofilm-forming bacterial culture, was used as a model for the study of bacterial Mn oxidation in freshwater and soil environments. The oxidation of aqueous Mn+2 [Mn+2 (aq)] by P. putida was characterized by spatially and temporally resolving the oxidation state of Mn in the presence of a bacterial biofilm, using scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Mn L2,3 absorption edges. Subsamples were collected from growth flasks containing 0.1 and 1 mM total Mn at 16, 24, 36, and 48 h after inoculation. Immediately after collection, the unprocessed hydrated subsamples were imaged at a 40-nm resolution. Manganese NEXAFS spectra were extracted from X-ray energy sequences of STXM images (stacks) and fit with linear combinations of well-characterized reference spectra to obtain quantitative relative abundances of Mn(II), Mn(III), and Mn(IV). Careful consideration was given to uncertainty in the normalization of the reference spectra, choice of reference compounds, and chemical changes due to radiation damage. The STXM results confirm that Mn+2 (aq) was removed from solution by P. putida and was concentrated as Mn(III) and Mn(IV) immediately adjacent to the bacterial cells. The Mn precipitates were completely enveloped by bacterial biofilm material. The distribution of Mn oxidation states was spatially heterogeneous within and between the clusters of bacterial cells. Scanning transmission X-ray microscopy is a promising tool for advancing the study of hydrated interfaces between minerals and bacteria, particularly in cases where the structure of bacterial biofilms needs to be maintained.

Download Full-text

Diverse Chemical Mixing States of Aerosol Particles in the Southeastern United States

10.5194/acp-2017-1222 ◽

2018 ◽

Cited By ~ 1

Author(s):

Amy L. Bondy ◽

Daniel Bonanno ◽

Ryan C. Moffet ◽

Bingbing Wang ◽

Alexander Laskin ◽

...

Keyword(s):

Chemical Species ◽

Accumulation Mode ◽

X Ray ◽

Internal Mixing ◽

Scanning Transmission ◽

Sea Spray Aerosol ◽

Cloud Activation ◽

Mixing States ◽

X Ray Absorption ◽

Individual Particles

Abstract. Aerosols in the atmosphere are chemically complex with thousands or more chemical species distributed in different proportions across individual particles in an aerosol population. An internal mixing assumption, with species present in the same proportions across all aerosols, is used in many models and calculations of secondary organic aerosol (SOA) formation, cloud activation, and aerosol optical properties. However, many of these effects depend on the distribution of species within individual particles, and important information can be lost when internal mixtures are assumed. Herein, we show that during the Southern Oxidant and Aerosol Study (SOAS) in Centreville, Alabama, at a rural, forested location, that aerosols frequently are not purely internally mixed, even in the accumulation mode (0.2–1.0 µm). A range of aerosol sources and mixing states were obtained using computer controlled scanning electron microscopy with energy dispersive X-ray spectroscopy (CCSEM-EDX) and scanning transmission X-ray microscopy-near-edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS). Particles that were dominated by SOA and inorganic salts were the majority of particles by number fraction from 0.2–5 microns with an average of 78 % SOA in the accumulation mode. However, during certain periods contributions by sea spray aerosol (SSA) and mineral dust were significant to accumulation (22 % SSA and 26 % dust) and coarse mode number concentrations (38 % SSA and 63 % dust). The fraction of particles containing key elements (Na, Mg, K, Ca, and Fe) were determined as a function of size for specific classes of particles. Within internally mixed SOA/sulfate particles

Download Full-text

In situ back-side illumination fluorescence XAFS (BI-FXAFS) studies on platinum nanoparticles deposited on a HOPG surface as a model fuel cell: a new approach to the Pt-HOPG electrode/electrolyte interface

Physical Chemistry Chemical Physics ◽

10.1039/c4cp00265b ◽

2014 ◽

Vol 16 (27) ◽

pp. 13748-13754 ◽

Cited By ~ 14

Author(s):

Hiromitsu Uehara ◽

Yohei Uemura ◽

Takafumi Ogawa ◽

Kentaro Kono ◽

Ryoichi Ueno ◽

...

Keyword(s):

Fine Structure ◽

Fuel Cell ◽

Back Side ◽

New Approach ◽

X Ray ◽

Model Fuel ◽

Fluorescence Xafs ◽

X Ray Absorption ◽

Side Illumination

We measured the in situ polarization-dependent X-ray absorption fine structure of PtNPs deposited on a flat HOPG substrate.

Download Full-text

Chemical Mapping of Polymer Microstructure Using Soft X-ray Spectromicroscopy

Australian Journal of Chemistry ◽

10.1071/ch05054 ◽

2005 ◽

Vol 58 (6) ◽

pp. 423 ◽

Cited By ~ 19

Author(s):

Adam P. Hitchcock ◽

Harald D. H. Stöver ◽

Lisa M. Croll ◽

Ronald F. Childs

Keyword(s):

Protein Interactions ◽

Polymer Surfaces ◽

Chemical Mapping ◽

Polymer Microstructure ◽

X Ray ◽

Potential Control ◽

Sample Data ◽

Scanning Transmission ◽

X Ray Absorption ◽

Conducting Polymer Films

Recently, synchrotron-based soft X-ray spectromicroscopy techniques have been applied to studies of polymer microstructure at the ~50 nm spatial scale. Functional group based chemical speciation and quantitative mapping is provided by near edge X-ray absorption fine structure spectral (NEXAFS) contrast. The techniques, sample data, and analysis methods of scanning transmission X-ray microscopy (STXM) and X-ray photoemission electron microscopy (X-PEEM) are outlined. The capabilities of STXM are illustrated by results from recent studies of (a) controlled release microcapsules and microspheres, (b) microcapsules being developed for gene therapy applications, (c) conducting polymer films studied in the presence of electrolyte and under potential control, and (d) studies of protein interactions with patterned polymer surfaces. In the latter area, the capabilities of STXM and X-PEEM are compared directly.

Download Full-text

High-accuracy X-ray absorption spectra from mMsolutions of nickel (II) complexes with multiple solutions using transmission XAS

Journal of Synchrotron Radiation ◽

10.1107/s1600577515006190 ◽

2015 ◽

Vol 22 (4) ◽

pp. 1008-1021 ◽

Cited By ~ 10

Author(s):

Christopher T. Chantler ◽

M. Tauhidul Islam ◽

Stephen P. Best ◽

Lachlan J. Tantau ◽

Chanh Q. Tran ◽

...

Keyword(s):

Multiple Solutions ◽

High Accuracy ◽

Hybrid Technique ◽

Edge Structure ◽

New Approach ◽

X Ray ◽

Square Planar ◽

Transmission Measurements ◽

First Time ◽

X Ray Absorption

A new approach is introduced for determining X-ray absorption spectroscopy (XAS) spectra on absolute and relative scales using multiple solutions with different concentrations by the characterization and correction of experimental systematics. This hybrid technique is a development of standard X-ray absorption fine structure (XAFS) along the lines of the high-accuracy X-ray extended range technique (XERT) but with applicability to solutions, dilute systems and cold cell environments. This methodology has been applied to determining absolute XAS of bis(N-n-propyl-salicylaldiminato) nickel(II) and bis(N-i-propyl-salicylaldiminato) nickel(II) complexes with square planar and tetrahedral structures in 15 mMand 1.5 mMdilute solutions. It is demonstrated that transmission XAS from dilute systems can provide excellent X-ray absorption near-edge structure (XANES) and XAFS spectra, and that transmission measurements can provide accurate measurement of subtle differences including coordination geometries. For the first time, (transmission) XAS of the isomers have been determined from low-concentration solutions on an absolute scale with a 1–5% accuracy, and with relative precision of 0.1% to 0.2% in the active XANES and XAFS regions after inclusion of systematic corrections.

Download Full-text

Chemical speciation of heterogeneously reduced Pu in synthetic brines

Radiochimica Acta ◽

10.1524/ract.2006.94.5.249 ◽

2006 ◽

Vol 94 (5) ◽

Cited By ~ 4

Author(s):

Mei Ding ◽

James L. Conca ◽

Christophe Den Auwer ◽

Rinat I. Gabitov ◽

Nancy J. Hess ◽

...

Keyword(s):

Fine Structure ◽

New Mexico ◽

Pilot Plant ◽

Chemical Speciation ◽

Speciation Analysis ◽

Waste Isolation Pilot Plant ◽

X Ray ◽

Xafs Spectroscopy ◽

Heterogeneous Reduction ◽

X Ray Absorption

SummaryX-ray absorption fine structure (XAFS) spectroscopy has been used to determine the speciation of Pu precipitates prepared by the heterogeneous reduction of Pu(VI) with Al and Fe in 5 M NaCl and an ERDA-6 brine, a simulant from the Waste Isolation Pilot Plant in Carlsbad, New Mexico. NaOCl was added to some of these solutions to determine its effect on Pu speciation. Analysis of the Pu

Download Full-text

Non-negative matrix analysis for effective feature extraction in X-ray spectromicroscopy

Faraday Discussions ◽

10.1039/c4fd00023d ◽

2014 ◽

Vol 171 ◽

pp. 357-371 ◽

Cited By ~ 10

Author(s):

Rachel Mak ◽

Mirna Lerotic ◽

Holger Fleckenstein ◽

Stefan Vogt ◽

Stefan M. Wild ◽

...

Keyword(s):

Large Scale ◽

Environmental Science ◽

Matrix Analysis ◽

Matrix Approximation ◽

New Approach ◽

X Ray ◽

Rich Information ◽

Preliminary Study ◽

X Ray Absorption ◽

Calculated Image

X-Ray absorption spectromicroscopy provides rich information on the chemical organization of materials down to the nanoscale. However, interpretation of this information in studies of “natural” materials such as biological or environmental science specimens can be complicated by the complex mixtures of spectroscopically complicated materials present. We describe here the shortcomings that sometimes arise in previously-employed approaches such as cluster analysis, and we present a new approach based on non-negative matrix approximation (NNMA) analysis with both sparseness and cluster-similarity regularizations. In a preliminary study of the large-scale biochemical organization of human spermatozoa, NNMA analysis delivers results that nicely show the major features of spermatozoa with no physically erroneous negative weightings or thicknesses in the calculated image.

Download Full-text