Julia Sedlmair

Characterization of refractory organic substances by NEXAFS using a compact X-ray source

PurposeWe present the characterization of environmental samples using near-edge X-ray absorption fine structure (NEXAFS) spectra recorded with an in-house device. We want to point out the feasibility of such an easily accessed complementary technique, if not sometimes alternative to NEXAFS studies performed with synchrotron radiation, as the number of compact setups is increasing.Materials and methodsThe experiments were carried out using a laser-driven plasma source. We studied heterogeneous samples like refractory organic substances to demonstrate the potential of NEXAFS spectra, achieved by such an instrument, concerning specimens of high chemical complexity.Results and discussionFrom the respective resonance peaks in the spectra, the presence of certain functional groups, such as aromatic or carbonyl groups, is verified, and the elemental composition is estimated. The results of the reference samples are consistent with the literature. For the environmental samples, external influences of the extraction solvent or fertilizers can be determined from the spectra.ConclusionsThis could provide the possibility to perform test experiments with samples, which are later studied in more detail with synchrotron light and might as well give an impulse on the broader spread of the application of NEXAFS spectroscopy.

Laboratory x-ray micro imaging: Sources, optics, systems and applications

We summarize the recent progress in laboratory-scale soft and hard x-ray micro imaging in Stockholm. Our soft x-ray work is based on liquid-jet laser-plasma sources which are combined with diffractive and multilayer optics to form laboratory x-ray microscopes. In the hard x-ray regime the imaging is based on a liquid-metal-jet electron-impact source which provides the necessary coherence to allow phase-contrast imaging with high fidelity.

Imaging of Vascular Smooth Muscle Cells with Soft X-Ray Spectromicroscopy

Using X-ray microscopy and spectromicroscopy, vascular smooth muscle cells (VSMCs) were imaged, prepared without using additional embedding material or staining, but by applying simple, noncryo fixation techniques. The cells were imaged with a compact source transmission X-ray microscope and a scanning transmission X-ray microscope (STXM). With the STXM, spectromicroscopy was performed at the C K-edge and the Ca L(III,II)-edges. VSMCs were chosen because of their high amount of actin stress fibers, so that the actin cytoskeleton should be visible. Other parts of the cell, such as the nucleus and organelles, were also identified from the micrographs. Both in the spectra and the images, the effects of the different preparation procedures were observable. Furthermore, Ca hotspots were detected and their density is determined.

Near-edge X-ray absorption fine structure measurements using a laser plasma XUV source

We present a compact setup for near-edge x-ray absorption spectroscopy at the carbon K-edge based on a laser-driven plasma source. Thin polymer films were investigated, showing good agreement with corresponding synchrotron data. Furthermore we have examined the carbon near-edge structure of phospholipids and fulvic acids, providing detailed information on intermolecular binding states.

X-Ray Spectromicroscopy Studies of Nanoparticles in Aqueous Media

X-ray microscopy is capable of imaging particles in the colloidal size range directly in their aqueous environment with high spatial resolution. It is possible to combine this with high spectral resolution for spectromicroscopy studies. Two types of microscopes are common in X-ray microscopy, the transmission X-ray microscope and the scanning transmission X-ray microscope; their setups are shown in this chapter. While the former takes high resolution images from an object within seconds or faster, the latter as an analytical instrument is suited for spectromicroscopy. As examples for visualization of the morphology, zinc containing particles and samples of clay and soil have been imaged with a transmission X-ray microscope. Images are shown from a cryo-tomography experiment based on X-ray microscopy images to obtain information about the three-dimensional structure of clusters of humic substances. The analysis of a stack of images taken with a scanning transmission X-ray microscope to bring together morphology and chemistry within a soil sample is shown.

X-ray stereo microscopy for investigation of dynamics in soils

X-ray stereo microscopy for investigation of dynamics in soils S-C Gleber 1 , J Sedlmair 1 , M Bertilson 3 , O von Hofsten 3 , S Heim 4 , P Guttmann 1 c/o 4 , H Hertz 3 , P Fischer 2 , and J Thieme 1 Institut f¨ r R¨ ntgenphysik, Georg-August-Universit¨ t G¨ ttingen, Friedrich-Hund-Pl.1, 37077 u o a o Gttingen, Germany Center for X-Ray Optics, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA 94720, USA Biomedical and X-ray Physics, Department of Applied Physics, Royal Institute of Technology, AlbaNova, SE-10691 Stockholm, Sweden Berliner Elektronenspeicherring Gesellschaft f¨ r Synchrotronstrahlung m.b.H, u Albert-Einstein-Str. 15, 12389 Berlin, Germany E-mail: sgleber@gwdg.de Abstract. The here presented combination of stereo imaging and elemental mapping with soft X-ray microscopy reveals the spatial arrangement of naturally aqueous colloidal systems, e. g. iron oxides in soil colloid clusters. Changes in the spatial arrangement can be induced by manipulating the sample mounted to the X-ray microscope and thus be investigated directly. 1. Introduction Due to its high spatial and spectral resolution, X-ray microscopy is an important instrument for investigation of colloidal systems, e.g. from environmental sciences [1]. Taking advantage of the natural contrast mechanism, sample preparation is not necessary, it can be imaged in transmission within its original aqueous media up to 10 µm thickness with a resolution in the range of 20-50 nm. In soil science, the element distribution within soil colloid clusters is of great interest [2]. With images taken above and below an absorption edge, distribution maps of the corresponding element are achieved. Thus, the iron distribution in colloidal samples from the environment has been determined. By tilting the object, stereo pairs of images have been taken. The here presented combination of elemental mapping with X-ray microscopy and stereo imaging provides a tool for that and reveals the spatial arrangement of e. g. iron oxides in soil colloid clusters. Changing the chemical conditions of aqueous medium leads to changes in the spatial arrangement, which can be done directly in the X-ray microscope. Since many of the so induced morphological changes are much slower than the time required even for taking stereo pairs, these changes can be investigated.Since many of the so induced morphological changes are much slower than the time required even for taking stereo pairs, these changes can be investigated. Theory and results of such experiments at three different setups will be presented briefly. 2. Parallax equation based stereo reconstruction Stereo calculations are based on the parallax equation [3]. It relates the parallax ∆ Y to the vertical distance h and the tilt angle 2θ (θ is the stereo angle). Thus, for a tilt by θ 2 − θ 1 = θ

High-resolution imaging of soil colloids in aqueous media with a compact soft X-ray microscope

Colloids play an important role when describing parameters of and processes within soils, sediments or aquifers due to their abundance and their high specific surface area. It is of great importance to visualize the morphology of the structures formed by these particles as close as possible to environmental conditions. With X-ray microscopy colloids from the environment can be imaged directly in aqueous media with high spatial resolution. We demonstrate the first use of a compact laboratory x-ray microscope for studies of colloids from the environment, namely aqueous suspensions of clays and soils. The microscope is based on a high-brightness laser-produced-plasma X-ray source, a multilayer mirror and diffractive optics. The experiments show that such compact X-ray microscopes are reaching the image quality and operational maturity to make a significant impact in fields like environmental sciences.

X‐Ray Spectromicroscopy of Biomolecular Matter and Soils

The aim of this study is the comparison of samples at dry and aqueous ambient conditions. Especially in biological and environmental sciences, x‐ray spectromicroscopy is a powerful tool for investigating key questions, e.g., the study of structures in soil samples or cells showing dimensions on the nanoscale, concurrently gaining insight into chemical interactions. The spectral range around the C K‐edge, in the so‐called water window (285 eV–523 eV), is especially well suited for the samples mentioned above, since it allows for working under aqueous and natural conditions. Exemplarily we present x‐ray spectromicroscopy experiments of three different samples of high carbon content to demonstrate the importance of a sample environment as close to natural conditions as possible.