Chemical Mapping of Polymer Microstructure Using Soft X-ray Spectromicroscopy

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.

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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.

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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.

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Exploiting Soft and Hard X-Ray Absorption Spectroscopy to Characterize Metallodrug/Protein Interactions: the Binding of [trans-RuCl4(Im)(dimethylsulfoxide)][ImH] (Im = imidazole) to Bovine Serum Albumin

Inorganic Chemistry ◽

10.1021/ic8001477 ◽

2008 ◽

Vol 47 (19) ◽

pp. 8629-8634 ◽

Cited By ~ 39

Author(s):

Isabella Ascone ◽

Luigi Messori ◽

Angela Casini ◽

Chiara Gabbiani ◽

Antonella Balerna ◽

...

Keyword(s):

Bovine Serum Albumin ◽

Serum Albumin ◽

Absorption Spectroscopy ◽

Protein Interactions ◽

Bovine Serum ◽

X Ray ◽

X Ray Absorption

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Chemical mapping with x-ray absorption spectroscopy

Biomineralization Sourcebook ◽

10.1201/b16621-6 ◽

2014 ◽

pp. 73-94

Author(s):

Yannicke Dauphin ◽

Murielle Salomé

Keyword(s):

Absorption Spectroscopy ◽

Chemical Mapping ◽

X Ray ◽

X Ray Absorption

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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.

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X-Ray Absorption Studies of Ti/Polymer and Cr/Polymer Interfaces

MRS Proceedings ◽

10.1557/proc-304-111 ◽

1993 ◽

Vol 304 ◽

Cited By ~ 1

Author(s):

R. L. Opila ◽

K. Konstadinidis ◽

A. O. Ibidunni ◽

A. J. Davenport ◽

H. S. Isaacs

Keyword(s):

Absorption Spectroscopy ◽

Polymer Surfaces ◽

Polymer Interfaces ◽

Final Reaction Product ◽

X Ray ◽

Metal Atoms ◽

Absorption Studies ◽

In Situ Heating ◽

X Ray Absorption

AbstractThe interface formed between metals, Ti and Cr, and polymers, epoxy and triazine, have been studied, nondestructively, using x-ray absorption spectroscopy. The metals were sputtered onto the polymer surfaces. Titanium reacts extensively, up to Ti thicknesses of 100 Å while Cr remains primarily metallic. In situ heating at 200°C increases the extent of reaction for both metals. Heating has a greater effect on metal/epoxy interfaces than metal/triazine. Titanium and Cr were ion implanted into the polymer in order to determine the interactions of isolated metal atoms with the polymer. Titanium and Cr appear to form oxides as the final reaction product, and the Ti is tetrahedrally coordinated.

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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

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