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Nanoplastics (NP) are of environmental and human health concern. We tested a novel NP extraction method and scanning transmission X-ray spectro-microscopy (STXM) in combination with near-edge X-ray absorption fine-structure spectroscopy (NEXAFS) to image and identify individual NP in environmental and food matrices. We 1) discussed the potential of STXM compared to other methods potentially suitable for NP analysis, 2) applied the method on NP suspensions of eight of the most common polymers, 3) analyzed environmental water and soil samples spiked with NP and 4) characterized NP in tea water infused in plastic teabags and unspiked soil samples. Here we show that STXM has methodological advantages and that polymers give characteristic spectra, which allows NP identification in environmental and food matrices. For soils we deliver a visual and spectroscopic characterization of NP, proving their presence and highlighting their diversity. Thus, STXM, can be used for the detection and characterisation of NP in different types of matrices.

International audience; Determining the Mn valence variation at the nanometer scale will be an important advance in the study of heterogeneous natural silicates. Here, the potential of the scanning transmission X-ray microscopy at the Mn L2,3-edges (640–655 eV) as a probe for manganese redox state is evaluated. For this purpose, several natural Mn-silicates (rhodonite, ardennite, piemontite, Mn4+-silicate, jacobsite) were analysed to identify the spectral parameters most sensitive to the Mn valence, regardless of the coordination environment, the crystal field strength, the nature and the length of the metal–ligand bonds, and the intra-atomic Coulomb and spin–orbit interactions. Two suitable spectral empirical calibrations are thus proposed, linking the Mn valence to two peak intensity ratios: one ratio of intensities from two energy points of the L2 peak (at 651.7 and 655.2 eV), and one ratio of intensities from one energy point of the L2 peak (at 655.2 eV) and one of the L3 peak (at 641.6 eV). Thank to them, the first quantitative Mn valence maps are constructed, with a high spatial resolution (

The carbon matrix in cell walls of lignocellulosic plants has high recalcitrance to chemical and biological decomposition. Thermal treatments, such as torrefaction and pyrolysis are therefore of in ...

The novel application of scanning transmission X-ray microscopy (STXM) to the microporous layer (MPL) of a polymer electrolyte membrane fuel cell is investigated. A spatially resolved chemical component distribution map is obtained for the MPL of a commercially available SGL 25 BC sample. This is achieved with near edge X-ray absorption fine structure spectroscopic analysis. Prior to analysis the sample is embedded in non-reactive epoxy and ultra-microtomed to a thickness of 100 nm. Polytetrafluoroethylene (PTFE), carbon particle agglomerates, and supporting epoxy resin distributions are identified and reconstructed for a scanning area of 6 μm × 6 μm. It is observed that the spatial distribution of PTFE is strongly correlated to the carbon particle agglomerations. Additionally, agglomerate structures of PTFE are identified, possibly indicating the presence of a unique mesostructure in the MPL. STXM analysis is presented as a useful technique for the investigation of chemical species distributions in the MPL.

LiFePO4 (LFP), the attractive commercial cathode materials, exhibits the phase separation between lithium-poor and lithium-rich phase within individual particles due to the wide miscibility gap. The boundaries between such phases develop large stress, lead to cracks within individual particles, and decay the cycle life. There have been lots of interest in investigating the origin of lithium heterogeneity and manipulating the phase boundaries within the particles during cycling. Previously, we revealed that insertion kinetics is dependent on the local lithium composition from which the hysteresis of lithium spatiodynamics originate. [ref.1] In addition, uniformity of ion insertion kinetics at electrolyte-electrode interface governs lithium heterogeneity and spatiodynamics in ether-based organic electrolyte. [ref.1] However, it remains still unclear how the chemical interaction of lithium ions, electrolyte molecules, and solid electrode controls nanoscale ion insertion kinetics. By developing operando scanning transmission x-ray microscopy (STXM) platform which maps lithium composition within individual LFP particles at 50 nm resolution during cycling, we investigated the interfacial lithium transport in various electrolytes: water, carbonates, and ethers. We synthesized LFP particles with platelet morphology and [010] crystallographic axis, which is fast ion diffusion direction, lied parallel to the monochromatic X-ray allowing to visualize lithium transport in the particles. Herein, we discover that aqueous electrolyte greatly accelerates lithium insertion kinetics, completely redirecting lithium heterogenesity and spatiodynamics compared with organic-based electrolyte. Aqueous environment kinetics show higher exchange current density (~700 mAm-2) than organic EC/DMC (~200 mAm-2) and also higher surface diffusion rate which account for the higher degree of intraparticle phase separation within the particles. By extracting kinetics parameters from our result, we experimentally demonstrate that heterogeneity and spatiodynamics in the single particle kinetics is determined by the strong interaction between the electrolyte molecules and the surface of electrode particles. Ref. 1 J. Lim et al. Science (2016) 353 p566 Figure 1

The main storage components of the maize endosperm are starch, proteins and lipids. Starch and proteins are heterogeneously deposited, leading to the formation of vitreous and floury regions at the periphery and at the centre of the endosperm. The vitreous/floury mass ratio is a key physical parameter of maize end-uses for the food, feed and non-food sectors, as well as for the resistance of seeds to environmental aggressions. To improve maize breeding for vitreousness, one of the main issues is to finely delineate the molecular and physicochemical mechanisms associated with the formation of endosperm texture. In this context, we use scanning transmission X-ray microscopy at the C K-edge on maize endosperm resin-embedded ultrathin sections. The combination of local near edge X-ray absorption fine structure (NEXAFS) spectroscopy and high-resolution images enable us to achieve a quantitative fine description of the spatial distribution of the main components within the endosperm.

We report the design and performance of a 3-electrode device for real time in situ scanning transmission X-ray microscopy studies of electrochemical processes under both static (sealed, non-flow) conditions and with a continuous flow of electrolytes. The device was made using a combination of silicon microfabrication and 3D printing technologies. The performance is illustrated by results of a study of copper deposition and stripping at a gold working electrode. X-ray absorption spectromicroscopy at the Cu 2p edge was used to follow the evolution as a function of potential and time of the spatial distributions of Cu(0) and Cu(i) species electro-deposited from an aqueous solution of copper sulphate. The results are interpreted in terms of competing mechanisms for the reduction of Cu(ii).

Selenium (Se) is an element of growing environmental concern, because low aqueous concentrations can lead to biomagnification through the aquatic food web. Biofilms, naturally occurring microbial consortia, play numerous important roles in the environment, especially in biogeochemical cycling of toxic elements in aquatic systems. The complexity of naturally forming multispecies biofilms presents challenges for characterization because conventional microscopic techniques require chemical and physical modifications of the sample. Here, multispecies biofilms biotransforming selenium oxyanions were characterized using X-ray fluorescence imaging (XFI) and scanning transmission X-ray microscopy (STXM). These complementary synchrotron techniques required minimal sample preparation and were applied correlatively to the same biofilm areas. Sub-micrometer XFI showed distributions of Se and endogenous metals, while Se K-edge X-ray absorption spectroscopy indicated the presence of elemental Se (Se0). Nanoscale carbon K-edge STXM revealed the distributions of microbial cells, extracellular polymeric substances (EPS), and lipids using the protein, saccharide, and lipid signatures, respectively, together with highly localized Se0 using the Se LIII edge. Transmission electron microscopy showed the electron-dense particle diameter to be 50-700 nm, suggesting Se0 nanoparticles. The intimate association of Se0 particles with protein and polysaccharide biofilm components has implications for the bioavailability of selenium in the environment.

Polarization dependent X-ray absorption spectroscopy (XAS) is a powerful probe of the anisotropic electronic structure of bulk single crystals, but its application to nanostructured samples is challenging. Here we describe a method for obtaining linearly polarized XAS spectra along three orthogonal axes of an individual nano-object using scanning transmission X-ray microscopy (STXM). The technique is applied to a single sodium titanate nanoribbon [(Na,H)Ti NR]. Significant linear dichroism is observed at both the Ti 2p and O 1s edges. The experimental results are compared with first-principles calculations; good agreement is achieved. The spectral changes among the three axes are attributed to the anisotropic Ti–O bonding of the various Ti and O sites in the monoclinic crystal structure of the nanoribbon. The methodology for 3D dichroic STXM measurements developed in this study is a powerful way to investigate the anisotropic geometric and electronic structure of nanomaterials.

In this study, bioaccumulation and tissue-level absorption of TiO2 nanoparticles (NPs) in freshwater invertebrates were investigated using transmission electron microscopy (TEM) and scanning transmission X-ray microscopy (STXM). The TiO2 NPs were used to test impacts of core sizes (i.e., 5 ± 2 nm and 23 ± 7 nm for TiO2(SYN) and TiO2(P25), respectively) and agglomerations (i.e., well dispersed vs. highly agglomerated) on the uptake of TiO2 NPs in Daphnia magna (D. magna). Highly agglomerated TiO2 NPs, regardless of their core sizes, were heavily taken up into the digestive tract of D. magna and no detectable penetration of both TiO2 NPs into the gut epithelial cells of D. magna was observed in TEM and STXM images. However, significant damages involving morphological changes in the microvilli and gut epithelial cells (e.g., irregular shaped microvilli, epithelial cell protrusion, and dilatation of cytoplasmic inclusion) were observed only with the commercial TiO2 NPs (TiO2(P25)) with larger core size and mixed crystalline phase, while the laboratory synthesized TiO2 NPs (TiO2(Syn)) with smaller core size and single crystalline phase showed slight morphological changes in the gut microvilli and epithelial cells. In the case of D. magna exposed to the well dispersed synthetic TiO2 NP ((Cit)TiO2(Syn)), only a negligible amount of TiO2 NPs were found within the digestive tract of the D. magna without any significant damages in the gut microvilli and epithelial cells and any detectable penetrations of TiO2 NPs into epithelial cells of D. magna gut. These TEM and STXM observations confirmed us that uptake of NP into D. magna are strongly dependent on their agglomeration (i.e., hydrodynamic sizes), rather than their core sizes, while direct penetration of NPs into tissues of digestive tract seems unlikely without significant morphological changes (e.g., collapse of the epithelial tissue) caused by high toxicity of NPs or released metal ions.

Scanning transmission X-ray microscopy (STXM) combined with an identical region in transmission electron microscopy (TEM) image has been used to detect the interior structure of individual thick multi-walled carbon nanotubes (MWCNTs). Two individual MWCNTs show similar morphology and diameters from the TEM images, while from the STXM spectra their interior structures have significantly different hollow parts. Moreover, the different hollow structures result in obviously different electronic structures which can be detected by X-ray absorption spectroscopy. Our results show an effective way to measure the inside hollow structure of thick MWCNTs.

International audience; Several naturally occurring biological materials, including bones and teeth, pathological calcifications, microbial mineral deposits formed in marine phosphogenesis areas, as well as bio-inspired cements used for bone and tooth repair are composed of Ca-phosphates. These materials are usually identified and characterized using bulk-scale analytical tools such as X-ray diffraction, Fourier transform infrared spectroscopy or nuclear magnetic resonance. However, there is a need for imaging techniques that provide information on the spatial distribution and chemical composition of the Ca-phosphate phases at the micrometer- and nanometer scales. Such analyses provide insightful indications on how the materials may have formed, e.g. through transient precursor phases that eventually remain spatially separated from the mature phase. Here, we present scanning transmission X-ray microscopy (STXM) analyses of Ca-phosphate reference compounds, showing the feasibility of fingerprinting Ca-phosphate-based materials. We calibrate methods to determine important parameters of Ca-phosphate phases, such as their Ca/P ratio and carbonate content at the ∼25 nm scale, using X-ray absorption near-edge spectra at the C K-, Ca L2,3- and P L2,3-edges. As an illustrative case study, we also perform STXM analyses on hydroxyapatite precipitates formed in a dense fibrillar collagen matrix. This study paves the way for future research on Ca-phosphate biomineralization processes down to the scale of a few tens of nanometers.

Scanning Transmission X-ray Microscopy (STXM) at the C 1s, F 1s and S 2p edges has been used to investigate degradation of proton exchange membrane fuel cell (PEM-FC) membrane electrode assemblies (MEA) subjected to accelerated testing protocols. Quantitative chemical maps of the catalyst, carbon support and ionomer in the cathode layer are reported for beginning-of-test (BOT), and end-of-test (EOT) samples for two types of carbon support, low surface area carbon (LSAC) and medium surface area carbon (MSAC), that were exposed to accelerated stress testing with upper potentials (UPL) of 1.0, 1.2, and 1.3 V. The results are compared in order to characterize catalyst layer degradation in terms of the amounts and spatial distributions of these species. Pt agglomeration, Pt migration and corrosion of the carbon support are all visualized, and contribute to differing degrees in these samples. It is found that there is formation of a distinct Pt-in-membrane (PTIM) band for all EOT samples. The cathode thickness shrinks due to loss of the carbon support for all MSAC samples that were exposed to the different upper potentials, but only for the most aggressive testing protocol for the LSAC support. The amount of ionomer per unit volume significantly increases indicating it is being concentrated in the cathode as the carbon corrosion takes place. S 2p spectra and mapping of the cathode catalyst layer indicates there are still sulfonate groups present, even in the most damaged material.

Scanning transmission X-ray microscopy (STXM) has been applied to characterize nano structured thin film (NSTF) catalysts implemented as electrode materials in proton-exchange-membrane (PEM) fuel cells. STXM is used to study all chemical constituents at various stages in the fabrication process, from the perylene red (PR149) starting material, through the formation of the uncoated perylene whiskers, their coated form with Pt-based catalyst, and toward the NSTF anode fully integrated into the catalyst coated membrane (CCM). CCM samples were examined prior to operational testing and after several different accelerated testing protocols: start-up/shut-down (SU/SD), and reversal tests. It was found that, while the perylene support material is present in the pre-test samples, it was completely absent in the post-test samples. We attribute this loss of perylene material to the presence of cracks in the catalyst combined with intensive hydrogenation processes happening at the anode during operation. Despite the loss of the perylene support, the platinum shells forming the NSTF anode catalyst layer performed well during the tests.

International audience; Estimation of Fe3+/ΣFe ratios in materials at the submicrometre scale has been a long-standing challenge in the Earth and environmental sciences because of the usefulness of this ratio in estimating redox conditions as well as for geothermometry. To date, few quantitative methods with submicrometric resolution have been developed for this purpose, and most of them have used electron energy-loss spectroscopy carried out in the ultra-high vacuum environment of a transmission electron microscope (TEM). Scanning transmission X-ray microscopy (STXM) is a relatively new technique complementary to TEM and is increasingly being used in the Earth sciences. Here, we detail an analytical procedure to quantify the Fe3+/ΣFe ratio in silicates using Fe L2,3-edge X-ray absorption near edge structure (XANES) spectra obtained by STXM, and we discuss its advantages and limitations. Two different methods for retrieving Fe3+/ΣFe ratios from XANES spectra are calibrated using reference samples with known Fe3+ content by independent approaches. The first method uses the intensity ratio of the two major peaks at the L3-edge. This method allows mapping of Fe3+/ΣFe ratios at a spatial scale better than 50 nm by the acquisition of 5 images only. The second method employs a 2-eV-wide integration window centred on the L2 maximum for Fe3+, which is compared to the total integral intensity of the Fe L2-edge. These two approaches are applied to metapelites from the Glarus massif (Switzerland), containing micrometre-sized chlorite and illite grains and prepared as ultrathin foils by focused ion beam milling. Nanometre-scale mapping of iron redox in these samples is presented and shows evidence of compositional zonation. The existence of such zonation has crucial implications for geothermometry and illustrates the importance of being able to measure Fe3+/ΣFe ratios at the submicrometre scale in geological samples.

The electronic structure of graphdiyne exposed to air is investigated utilizing X-ray absorption spectroscopy and scanning transmission X-ray microscopy. It is found that carbon–carbon triple bonds at defect sites in graphdiyne have been changed to double bonds after 3 months in air. The experimental results reveal the existence of oxygen and nitrogen functional groups and indicate that the oxidation takes place throughout the aged graphdiyne while the nitrogen contamination is mainly on its surface. Buckling of the aged graphdiyne is observed, resulting from bond length change due to the opening of triple bonds. It is also shown that annealing at a high temperature such as 800 °C may remove most of the functional groups in the aged graphdiyne.

The electronic structure of individual carbon nanotubes (CNTs) with different diameters has been investigated by scanning transmission X-ray microscopy (STXM). Various factors that may alter the STXM spectral features in CNT bundles have been discussed. Tube diameter has been found to be proportional to the spectral intensity, whereas it has negligible effect on the spectral shape. Disordered structure in CNTs introduced in the synthesis process was observed, which significantly affected the X-ray absorption spectrum by a reduction of the π* excitation. Moreover, tube–tube interaction in CNT bundles was detected, which can enhance the π* excitation. Insights into the nature of CNT bundles with various electronic structures may provide a new vision to understand the performance of CNT-based devices.

Quantifying how atmospheric particles interact with water vapor is critical for understanding the effects of aerosols on climate. We present a novel method to measure the mass-based hygroscopicity of particles while characterizing their elemental and carbon functional group compositions. Since mass-based hygroscopicity is insensitive to particle geometry, it is advantageous for probing the hygroscopic behavior of atmospheric particles, which can have irregular morphologies. Combining scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), scanning transmission X-ray microscopy (STXM) analysis, and in situ STXM humidification experiments, this method was validated using laboratory-generated, atmospherically relevant particles. Then, the hygroscopicity and elemental composition of 15 complex atmospheric particles were analyzed by leveraging quantification of C, N, and O from STXM, and complementary elemental quantification from SEM/EDX. We found three types of hygroscopic responses, and correlated high hygroscopicity with Na and Cl content. The mixing state of 158 other particles from the sample broadly agreed with those of the humidified particles, indicating the potential to infer atmospheric hygroscopic behavior from a selected subset of particles. These methods offer unique quantitative capabilities to characterize and correlate the hygroscopicity and chemistry of individual submicrometer atmospheric particles.

The C 1s inner shell excitation spectra of individual metallic and semiconducting single-walled carbon nanotubes (SWCNTs) were measured using high-resolution electron energy loss spectroscopy in an aberration-corrected transmission electron microscope (TEM-EELS). On the basis of its diameter, the metallic SWCNT is most likely a (10,10) sample, whereas (11,12) and a number of other chiral vectors are consistent with the diameter of the semiconducting SWCNTs. The C 1s X-ray absorption spectra of the same electronically pure SWCNT materials were measured as individual bundles or agglomerations of bundles by scanning transmission X-ray microscopy. Spectral differences in the C 1s → π* transitions of metallic and semiconducting species, related to differences in the van Hove singularities in their unoccupied states, are observed by both methods. The fine structure of the C 1s → π* transitions is similar to that recently reported from nonspatially resolved X-ray absorption spectroscopy of ensemble samples of high-purity metallic and semiconducting SWCNTs. The quality of the TEM-EELS spectra of individual SWCNTs is such that the line shape can be used to identify if they are metallic or semiconducting, thereby opening up the possibility to interrogate the electronic state of single-SWCNT devices. A strong X-ray linear dichroism in the C 1s → π* band of both types of SWCNTs was observed.

Scanning transmission X-ray microscopy (STXM) at the C 1s and Cu 2p edges was used to study the fate of Cu nanoparticles, including their sorption–dissolution, speciation and distribution in a complex natural river biofilm exposed to 1 mg L − 1 Cu nanoparticles for 5 min, 3 days or 7 days. The original Cu nanoparticles, ~ 30 nm in diameter, were composed of Cu(I) and Cu(II) species, presumably a Cu(I) core surrounded by oxidized Cu(II). When the Cu nanoparticles were initially added to the biofilm, Cu nanoparticles were occasionally found as individual particles but most frequently were observed as aggregates. The aggregates were in association with diatoms and the extracellular polymeric substances (EPS) of the biofilm. In addition, a new Cu(II) species, as evident from a shift in its peak position (− 0.4 eV) relative to the Cu nanoparticles, was found to be sorbed by the diatoms after 5 min and was still detected after 7 days. Evidently, the Cu nanoparticles had undergone dissolution, followed by sorption of ionic Cu(II) by the diatoms. The bacteria and cyanobacteria in the biofilm did not apparently sorb detectable amounts of Cu at any time. C 1s measurements indicated that the Cu(II) from solution was sorbed by the lipid-rich extracellular polymeric substances associated with the diatoms. These observations demonstrated that both the Cu nanoparticles and dissolution products remained associated with the river biofilm through interactions with specific biopolymers up to 7 days following exposure. Therefore, for some metal nanomaterials, sorption of the solid phase with subsequent dissolution and re-sorption are significant with respect to their chemodynamics and effects on the biofilm, especially when trophic transfer events are considered. Importantly, these interactions provide an entry point for copper into the aquatic food web.

Carbon–TiO 2 nanohybrids (CTs, 5–10 nm TiO 2 nanocrystals evenly dispersed on carbon film) have been successfully prepared via a mild, one-step hydrothermal approach. The interactions and electronic structures of carbon and TiO 2 nanoparticles and the enhanced visible photocatalytic mechanism were investigated by scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry in detail. Meanwhile, it was demonstrated that the as-obtained CTs had a large BET specific surface area of 304.6 m 2 /g and showed excellent photocatalytic abilities towards organic (Rhodamine B, benzene) and inorganic pollutant (K 2 Cr 2 O 7 ) degradation in visible light. This work provided a new approach for the high performance catalyst design towards new energy sources and environmental issues.

Pentacene field-effect transistors were prepared on silicon nitride membranes for scanning transmission X-ray microscopy (STXM) investigations. The membranes were modified by different self-assembled monolayers (SAMs). Pentacene was deposited atop the SAM-treated membrane and the in-plane orientation of the grains were subsequently investigated by polarization dependent STXM measurements. The grain sizes were determined and compared to those obtained from atomic force microscopy (AFM) measurements. Statistical analysis of the grain orientation was correlated with the charge carrier mobility of the films, in which we observed an increase in the mobility with increasing grain size and decreasing surface roughness of the SAM.

We describe a method of quantitative mapping the water content in the catalyst coated membranes (CCM) of proton exchange membrane (PEM) fuel cells with high spatial resolution (~30 nm) using soft X-ray Scanning Transmission X-ray Microscopy. Detailed component chemical maps of CCMs at different environmental conditions (relative humidity (RH)) were generated from O 1s optical density measurements by fitting to the soft X-ray absorption reference spectra for liquid and gaseous water and those of the electrode and membrane materials. Under high RH conditions, different distributions of water (vapor and liquid) were found for the cathode layer and the membrane. These results are related to differences in hydrophilicity / hydrophobicity of different regions.

FT30 type thin film composite membranes used for reverse osmosis water purification are very difficult to analyze. With the remarkably thin polyamide layer and surface modification of the polymers now being reported, a new analytical technique is needed to determine the surface structure and chemical distribution in the active layer. In this study we show that scanning transmission X-ray microscopy (STXM) can be used to determine the spatial distribution of polyamide and polysulfone and we report on the detection of an unexpected new phase. The new phase was identified as a homopolymer of the meta-phenylene diamine (MPD) that forms in MPD solutions and can be incorporated into the discrimination layer during the interfacial reaction with the TMC to produce a mixed polyamide polyMPD layer. The detection of this second phase was only made possible by STXM. At the levels detected in membranes in this study (less than 8%) the second phase had no effect on the flux or salt passage of the membranes, however at higher levels a change in the membrane properties most likely would occur and the quantity of the polyMPD present should be eliminated or controlled.

article i nfo Soft X-ray scanning transmission X-ray microscopy (STXM) was used to measure the Fe L2, 3 X-ray magnetic circular dichroism (XMCD) signal from individual, 30 nm diameter magnetosomes in a magnetotactic bacterium, specifically the marine vibrio strain MV-1. The Fe L2, 3 spectra recorded with circularly polarized X-rays from an elliptically polarizing undulator were very similar in shape and magnitude to those of fully saturated magnetite (Fe3O4). As previously determined by other techniques, our results show that the magnetic moments of individual magnetosomes arranged in linear chains in intact cells of strain MV-1 are all oriented in the same direction. The magnitude of the XMCD signal averaged over a chain of 9 magnetosomes in one cell is similar to that of single crystal magnetite. The spectral shape is slightly different, and indicates that magnetosomes have excess Fe (II)

Diverse microscopy techniques have been extensively used in the past to study the ultrastructure of modern and fossil sporoderms for various purposes such as taxonomic identification or study of sporoderm formation and its evolution in different groups of plants. Optical microscopy and Scanning and Transmission Electron Microscopies (SEM and TEM) have been particularly useful in providing structural information at the μm- and nm-scales. In parallel, chemical analyses have been conducted on bulk samples to document variations in sporopollenin composition between major groups and compositional evolution/preservation during coalification processes . Here, we describe a microscopy tool, Scanning Transmission X-ray Microscopy (STXM), which offers valuable capabilities for palynological studies as demonstrated by applications of this technique to fossil spores over the past decade. This microscopy technique, which uses soft X-rays produced by synchrotron radiation sources, provides 25-nm spatial resolution element-based image contrast, and K or L near-edge X-ray absorption fine structure (NEXAFS) spectra at each 25-nm x 25-nm pixel in a STXM image for a number of key elements (e.g., K-edges of C, N, O, F, Na, Mg, Al, and Si and L-edges of K, Ca, Ti-Zn, Ga, Ge, As, Se, Rb, and Sr). STXM can be performed in situ on thin samples with no need for prior chemical extraction or staining. Comparison with conventional imaging techniques such as optical microscopy and TEM shows that STXM is an ideal complement to these microscopies. We present new STXM data obtained on modern Lilium longiflorum Thunb. pollen grains and on well-preserved lycopsid spores, identified as Annalepis zeilleri (Fliche) Grauvogel-Stamm and Duringer, collected from the Lettenkohle Formation of the Wasselonne Quarry (NE France). Using this technique, different biochemical compounds such as sporopollenin or cellulose can be specifically imaged at the 25-nm scale. Additionally, NEXAFS spectra can provide information on elemental speciation, i.e. the types of C-containing functional groups (e.g., aromatic, aliphatic, carboxylic, alcoholic…) and the redox state of iron and manganese. Based on these analyses, it is possible to document the chemical preservation of fossil spores that experienced diagenesis and possibly metamorphism.

The rates of chemical transformation by radiation damage of polystyrene (PS), poly(methyl methacrylate) (PMMA), and fibrinogen (Fg) in a X-ray photoemission electron microscope (X-PEEM) and in a scanning transmission X-ray microscope (STXM) have been measured quantitatively using synchrotron radiation. As part of the method of dose evaluation in X-PEEM, the characteristic (1/e) sampling depth of X-PEEM for polystyrene in the C 1s region was measured to be 4 ± 1 nm. Critical doses for chemical change as monitored by changes in the X-ray absorption spectra are 80 (12), 280 (40) and 1230 (180) MGy (1 MGy = 6.242*ρ eV/nm3, where ρ is the polymer density in g/cm3) at 300 eV photon energy for PMMA, Fg and PS, respectively. The critical dose for each material is comparable in X-PEEM and STXM and the values cited are thus the mean of the values determined by X-PEEM and STXM. C 1s, N 1s and O 1s spectroscopy of the damaged materials is used to gain insight into the chemical changes that soft X-rays induce in these materials.

The polarization dependence (linear dichroism) of the C 1s X-ray absorption spectrum of individual multi-walled carbon nanotubes (MWCNTs) is measured using scanning transmission X-ray microscopy. A very strong dichroic effect is found in the C 1s --> pi* transition, with almost complete disappearance of this transition when the electric-field (E)-vector is aligned parallel to high-quality (low-defect) MWCNTs and maximum intensity when the E-vector is orthogonal to the tube axis. In contrast, there is very little dichroism in the C 1s --> sigma* transitions. The origin of this polarization effect is explained. The magnitude of the polarization dependence is found to differ in MWCNTs synthesized by different methods (arc discharge versus chemical vapor deposition). This is ascribed to differences in densities of sp(2)-type defects. The potential for use of this signal to characterize defects in single-carbon-nanotube devices is discussed.

An important feature of microbial communities is the spatial heterogeneity of extracellular chemistry. Scanning transmission X-ray microscopy (STXM) was used to map the spatial distribution of iron speciesthroughout Pseudomonas aeruginosa biofilms to assess the influence of chemical heterogeneity on biomineralization. P. aeruginosa biofilms were treated with Fe(III)-amended media. Speciation and quantitative mapping using STXM image sequences in the Fe 2p(3/2) (L3) absorption edge region revealed both Fe(II) and Fe(III) in localized microenvironments. Fe(III) was mainly associated with cell surfaces, while small amounts of Fe(II) was found in the extracellular space. Biofilms were also characterized using C 1s edge STXM image sequences. Anaerobic growth assays and confocal microscopy revealed the inability of P. aeruginosa to directly reduce Fe(III), implicating indirect iron reduction mechanisms in the formation of fine-grained, multivalent minerals. These studies suggest that geochemical microenvironments found throughout microbial communities are even more complex than previously believed.

An azimuthal rotatable sample cell, an electrochemical cell and a controlled humidity cell for in-situ scanning transmission X-ray microscopy (STXM) were developed at UVSOR-III Synchrotron (Okazaki, Japan). By using these sample cells, the polarization dependence of sodium titanate nanoribbons, in-situ electrochemistry of 0.1M FeSO4 solution, and in-situ morphological change of a functional polymer with changing humidity were successfully measured.

Using the scanning transmission X-ray microscope at BESSY II, colloidal structures from a Chernozem soil have been studied with a spatial resolution around 60 nm and a spectral resolution of 1,700 at the K-absorption edge of carbon. Elemental mapping has been used to determine the distribution of organic matter within the colloidal structures. Spectra have been extracted from image stacks to obtain information about the chemical state. For the analysis of the latter, principal component analysis and cluster analysis have been applied. It was possible, for example, to discriminate clay particles against organic components.

A scanning transmission X-ray microscope at the Lawrence Berkeley National Laboratory is used to measure organic functional group abundance and morphology of atmospheric aerosols. We present a summary of spectra, sizes, and shapes observed in 595 particles that were collected and analyzed between 2000 and 2006. These particles ranged between 0. 1 and 12 gm, and represent aerosols found in a large range of geographical areas, altitudes, and times. They include samples from seven different field campaigns: PELTI, ACE-ASIA, DYCOMS II, Princeton, MILAGRO (urban), MILAGRO (C-130), and INTEX-B. At least 14 different classes of organic particles show different types of spectroscopic signatures. Different particle types are found within the same region while the same particle types are also found in different geographical domains. Particles chemically resembling black carbon, humic-like aerosols, pine ultisol, and secondary or processed aerosol have been identified from functional group abundance and comparison of spectra with those published in the literature. (C) 2007 Elsevier Ltd. All rights reserved.

Carbonaceous particles originating from biomass burning can account for a large fraction of organic aerosols in a local environment. Presently, their composition, physical and chemical properties, as well as their environmental effects are largely unknown. Tar balls, a distinct type of highly spherical carbonaceous biomass burn particles, have been observed in a number of field campaigns. The Yosemite Aerosol Characterization Study that took place in summer 2002 occurred during an active fire season in the western United States; tar balls collected during this field campaign are described in this article. Scanning transmission X-ray microscopy and near-edge X-ray absorption fine structure spectroscopy are used to determine the shape, structure, and size-dependent chemical composition of approximately 150 individual spherical particles ranging in size from 0.15 to 1.2 mum. The elemental composition of tar balls is approximately 55% atomic carbon and approximately 45% atomic oxygen. Oxygen is present primarily as carboxylic carbonyls and oxygen-substituted alkyl (O-alkyl-C) functional groups, followed by moderate amounts of ketonic carbonyls. The observed chemical composition, density, and carbon functional groups are distinctly different from soot or black carbon and more closely resemble high molecular weight polymeric humic-like substances, which could account for their reported optical properties. A detailed examination of the carboxylic carbonyl and O-alkyl-C functional groups as a function of particle size reveals a thin oxygenated interface layer. The high oxygen content, as well as the presence of water-soluble carboxylic carbonyl groups, could account for the reported hygroscopic properties of tar balls. The presence of the oxygenated layer is attributed to atmospheric processing of biomass burn particles.

Calcium silicate hydrate (CSH), a new type of bioceramics, has gained significant attention in hard tissue restoration because of their impressive role in the stimulation of osteoblast proliferation and differentiation in vitro. The further development of mesoporous bioceramics opens up new opportunities for drug delivery in hard tissue therapies. In this thesis, interaction mechanisms of drug molecules with CSH of different morphologies and CSH/polymer composites, imaging of drug distributions in CSH carriers in nanoscale, and the biomineralization mechanisms of CSH in vitro during drug release are extensively investigated using X-ray absorption near edge structure (XANES) and scanning transmission X-ray microscopy (STXM). The interactions between different drug molecules and CSH with different morphologies are investigated using XANES. It is found that the morphology and the presence of hydrates of drug carriers influence the drug loading capacities (DLCs). CSH provides active linkage sites (Ca-OH and Si-OH groups) for the acidic functional groups of drug molecules via electrostatic interactions. Besides, it is also found that the stoichiometric ratio of Ca2+ ions of CSH carriers to the functional groups of drug molecules will significantly influence the DLCs.The mapping of an individual CSH microsphere, which was synthesized by a sonochemical method, before and after the loading of ibuprofen (IBU) is recorded by STXM. This STXM-XANES study illustrates the integrity and the homogenously distribution of drug molecules in these drug carriers. The biomineralization of the drug carrier, CSH microspheres upon IBU release, are monitored with XANES and STXM. The biomineralization mechanisms for CSH microspheres loaded with IBU in the SBF solution, which were still controversial before, emerge via STXM mapping, spectral comparisons and fitting analysis. Finally, CSH/polymer composites were synthesized using a controlled precipitation reaction between calcium salt and silicate salt, followed by the addition of various polymer solutions iv at room temperature. The interactions between different polymers and CSH, the interactions between drug molecule IBU and these polymer composites have been extensively studied by XANES. We find that the polymers alter the structure of CSH to various degrees, and that this behaviour further influences the DLCs and drug release kinetics.

In situ characterization of colloidal particles under hydrous conditions is one of the key requirements for understanding their state of aggregation and impact on the transport of pollutants in aqueous environments. Scanning transmission X-ray microscopy (STXM) is one of the few techniques that can satisfy this need by providing element- and chemical-state-specific 2-D maps at a spatial resolution better than 50 nm using soft X-rays from synchrotron radiation wiggler or undulator sources tuned to the absorption edges of different elements. X-ray absorption near-edge structure (XANES) spectra can also be collected simultaneously at a similar spatial resolution and can provide phase identification in many cases. In this study, we report STXM images and XANES spectroscopy measurements at or above the Al K-edge (E = 1559.6 eV) of various Al-containing minerals and synthetic oxides [alpha-Al2O3 (corundum), gamma-Al2O3, gamma-AlOOH (boehmite), alpha-Al(OH)3 (bayerite), KAl2(AlSi3O10)(OH)2 (muscovite), (Al,Mg)8(Si4O10)4(OH)8.nH2O (montmorillonite), and Mg6Al2(OH)16CO3.4H2O (hydrotalcite)] and demonstrate the capability of this spectromicroscopic tool to identify different Al-containing mineral colloids in multiphase mixtures in aqueous solution. We also demonstrate that STXM imaging at or above the C K-edge (E = 284.2 eV) and Al K-edge can provide unique information on the interactions between bacteria and Al-containing nanoparticles in aqueous suspensions. STXM images of a mixture of Caulobacter crescentus and montmorillonite and corundum particles just above the C and Al K-edges show that the mineral particles and bacteria are closely associated in aggregates, which is likely due to the binding of bacteria to clay and corundum particles by extracellular polysaccharides.

We have applied Scanning Transmission Soft X-ray Microscopy (STXM) to investigate the charge state distribution of Mn in two kinds of Mn-biominerals, Mn nodules collected from Lake Michigan sediments and Mn precipitates formed by spores of a marine bacillus SG-1 under transport limited reaction conditions. A data analysis technique was developed, which allows for extraction of spatially resolved 2-d charge state maps of manganese on a submicron level. We find that the charge state of Mn dominates the spectral shape of L-edge spectra of environmentally important single oxidation state Mn minerals and that spectra of mixed oxidation state oxides can be modelled by a combination of appropriate single oxidation state reference spectra. Two-dimensional maps of charge state distributions clearly reveal domains of different oxidation states within single particles of Mn-micronodules. Spots of preferred accumulation of Mn(II) were found, which indicates biogenic precipitation of Mn(II)-species as a first step of nodule formation. The presence of Mn(III) in the studied sediment samples suggests the involvement of one-electron oxidation processes and reaction conditions which inhibit or slow down the disproportionation of Mn(III)-products. Under transport limited conditions, Mn oxidation products formed by spores of the marine bacillus SG-1 can vary from cell to cell. The presence of significant amounts of Mn(III) containing species points to the involvement of one-electron oxidation reactions as in the case of the micro-nodules. Our technique and the results obtained form a new basis for the mechanistic understanding of the formation of Mn biominerals in the environment.

International audience; Iron gall inks have largely been used for writing in European western countries from the Middle Ages to the twentieth century. Yet, their use may significantly damage the paper through acid hydrolysis and iron catalysed oxidation. These phenomena are not only governed by the chemistry of the ink + cellulose system, but also by the penetration of the ink within the paper sheet. Here, we investigate ink penetration at the scale of a paper fibre using synchrotron-based STXM. This technique allows in situ mapping of the iron redox state and carbon speciation down to the sub-micrometre scale. Linen fibres have been impregnated by iron sulphate, gallic acid and gum Arabic; i.e. the three main ingredients of iron gall inks. Soft X-ray transparent ultrathin foils of impregnated fibres have been extracted using FIB milling. The data reported here evidence that ink components do not penetrate through the paper fibres the same way. In the absence of gum Arabic, gallic acid penetrates within the fibre but mostly remains in the outer part of the cell wall. A significant precipitation of Fe(III) gallate occurs during this migration whereas small amounts of iron (mostly Fe(II)) penetrate through the inner part of the fibre. The addition of gum Arabic as a binder makes the ink more viscous and significantly jeopardizes its ability to penetrate the fibre. The ink thus remains at the surface of the fibre. Low amounts of iron, essentially Fe(II), do still penetrate the fibre.

Humic acid (HA) agglomerates formed in aqueous solutions in the presence of trivalent Eu cations were investigated in situ with a combination of atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM). The micromorphologies of both natural HA and a melanoidine based synthetic HA observed by AFM in electrolyte solution are in fair agreement with previous AFM studies on humic substances. STXM micrographs of Eu(III) induced HA agglomeration reveal zones of high and low optical density with markedly distinct C K-NEXAFS, indicative of different humic functionalities. Particulate agglomerates observed by AFM can be correlated to the dense zones, whereas fibrous structures in AFM images can be associated with the low density areas. The Eu cation distribution within the agglomerates cannot be unambiguously deduced from their C K-NEXAFS spectra. The near edge X-ray absorption fine structure spectra can be correlated to a segregation of different HA fractions, possibly due to the presence of humic species with different affinities for metal cation complexation. STXM micrographs of purified Aldrich HA exhibit the presence of other yet unidentified, carbon-rich particles, independent of the addition of Eu(III). Both AFM and STXM results for the synthetic melanoidine based HA demonstrate a homogeneous morphology and chemical structure.

Magnetic iron oxide nanoparticle clusters (mnpc) coated with organic stabilizers were investigated using scanning transmission x-ray microscopy (STXM). Simultaneous surface and bulk sensitive Fe L₃ edge absorption spectra, obtained using a photomultiplier tube and a channeltron, were used to detect subtle changes in the oxidation state in the surface and bulk of Iron Oxide mnpc. The effectiveness of this mode of STXM operation is demonstrated for these nanoparticle clusters.

The autocatalytic growth of arbitrarily shaped nanostructures fabricated by electron beam-induced deposition (EBID) and electron beam-induced surface activation (EBISA) is studied for two precursors: iron pentacarbonyl, Fe(CO)5, and cobalt tricarbonyl nitrosyl, Co(CO)3NO. Different deposits are prepared on silicon nitride membranes and silicon wafers under ultrahigh vacuum conditions, and are studied by scanning electron microscopy (SEM) and scanning transmission X-ray microscopy (STXM), including near edge X-ray absorption fine structure (NEXAFS) spectroscopy. It has previously been shown that Fe(CO)5 decomposes autocatalytically on Fe seed layers (EBID) and on certain electron beam-activated surfaces, yielding high purity, polycrystalline Fe nanostructures. In this contribution, we investigate the growth of structures from Co(CO)3NO and compare it to results obtained from Fe(CO)5. Co(CO)3NO exhibits autocatalytic growth on Co-containing seed layers prepared by EBID using the same precursor. The growth yields granular, oxygen-, carbon- and nitrogen-containing deposits. In contrast to Fe(CO)5 no decomposition on electron beam-activated surfaces is observed. In addition, we show that the autocatalytic growth of nanostructures from Co(CO)3NO can also be initiated by an Fe seed layer, which presents a novel approach to the fabrication of layered nanostructures.

The structural and chemical homogeneity of monolithic columns is a key parameter for high efficiency stationary phases in liquid chromatography. Improved characterization techniques are needed to better understand the polymer morphology and its optimization. Here the analysis of polymer monoliths by scanning transmission X-ray microscopy (STXM) is presented for the first time. Poly(butyl methacrylate-co-ethyleneglycoldimethacrylate) [poly(BuMA-co-EDMA)] monoliths containing encapsulated divinylbenzene (DVB) nanoparticles were characterized by STXM, which gives a comprehensive, quantitative chemical analysis of the monolith at a spatial resolution of 30 nm. The results are compared with other methods commonly used for the characterization of polymer monoliths [scanning electron microscopy (SEM), transmission electron microscopy (TEM), mercury porosimetry, and nitrogen adsorption]. The technique permitted chemical identification and mapping of the nanoparticles within the polymeric scaffold. Residual surfactant, which was used during the manufacture of the nanoparticles, was also detected. We show that STXM can give more in-depth chemical information for these types of materials and therefore lead to a better understanding of the link between polymer morphology and chromatographic performance. Refereed/Peer-reviewed