Chemical Contrast in X-Ray Microscopy and Spatially Resolved XANES Spectroscopy of Organic Specimens

Abstract

The scanning transmission x-ray microscope at the National Synchrotron Light Source has been used to record x-ray absorption near-edge structure (XANES) spectra from 0.01-square-micrometer regions of organic specimens. The spectral features observed reflect the molecular structure of the dominant absorbing atoms and provide the contrast mechanism for high-resolution imaging with chemical sensitivity. This technique was used with x-ray energies near the carbon K absorption edge to identify and map separate phases in various polymer blends and to map the DNA distribution in chromosomes with a spatial resolution of 55 nanometers.

On Source Identification and Alteration of Single Diesel and Wood Smoke Soot Particles in the Atmosphere; An X-Ray Microspectroscopy Study

“…Combining NEXAFS spectroscopy and zone plate imaging, scanning transmission X-ray microscopes (STXMs) provide both high chemical sensitivity and a spatial resolution less than 40 nm which allows gaining more detailed information on the variation in structures of single soot particles depending on the combustion source. First C(1s) NEXAFS spectra were collected with X-ray microscopy in the early nineties (8). Twelve years later the technique was first used to characterize the chemical structure of soot particles from diesel combustion (9).…”

Physical and chemical changes in polystyrene during electron irradiation using EELS in the TEM: contribution of the dielectric function

“…X-ray absorption spectroscopy (XAS) and electron energy-loss spectroscopy (EELS) are powerful techniques used to probe the local chemical and electronic structure of carbon-based materials at a submicrometre spatial resolution (Isaacson & Johnson, 1985;Outka & Stöhr, 1988;Sawyer & Grubb, 1996). XAS is estimated to produce three orders of magnitude less damage than does EELS, and its energy resolution is excellent (a few meV), but its spatial resolution is limited (Ϸ 50 nm with the synchrotron radiation; Ade et al, 1992;Ade, 1994). By contrast, EELS coupled with TEM can have an excellent spatial resolution (a few angstroms) and a rather good energy resolution (about 0·6 eV with a fieldemission gun), which allows chemical imaging at high spatial resolution (Susnitski et al, 1994;Martin et al, 1996); however, it produces severe irradiation damage as far as polymers are concerned.…”

Synchrotron‐Based Near‐Edge X‐Ray Spectroscopy of Natural Organic Matter in Soils and Sediments

“…A general challenge is posed by the heterogeneity of environmental materials (Hitchcock et al, 2005a), which often contain not only biological but also mineral matter. Ade et al (1992) recommended a sample thickness between 40 and 800 nm for biological materials. When minerals are present or when carbon is present in high concentrations, samples should preferably have a thickness of less than 200 nm, whereas analyses of the mineral elements (Al, Si) may require slightly thicker samples.…”

“…What has proved especially useful is the coupling of NEXAFS with imaging in an approach called spectromicroscopy in X-ray imaging (Ade et al, 1992;Jacobsen et al, 2000;Hitchcock et al, 2008; detailed description in Section 2.3) or spectrum imaging in electron microscopy (Jeanguillaume and Colliex, 1989;Hunt and Williamds, 1991). With spectromicroscopy, entire areas of soils and sediments can be measured by NEXAFS with very high spatial resolution .…”

“…NEXAFS spectroscopy, microspectroscopy and the development of NEXAFS spectromicroscopy (explained in Section 2.3) have been one of the most promising tools for the study of soils and sediments since its development in the 1980s (Kirz et al, 1995;Ade and Urquhart, 2002), but was only more widely used for investigations of NOM since the mid-1990s. The scope of studies has included contaminant and metal speciation, uptake, and distributions (Schulze et al, 1995), model humic and natural substances (Vairavamurthy et al, 1997;Plaschke et al, 2004Plaschke et al, 2005Rothe et al, 2004), microorganisms (Thieme et al, 1994;Lawrence et al, 2003;Liang et al, 2006), soils (Schmidt et al, 2003;Kinyangi et al, 2006;Schumacher et al, 2005;Lehmann et al, 2007;Wan et al, 2007) and soil extracts (Solomon et al, 2005a(Solomon et al, 2007a, dissolved organic matter (DOC) (Schumacher et al, 2006), sediments Benzerara et al, 2006;Haberstroh et al, 2006, Brandes et al, 2007 or aquatic colloids (Niemeyer et al, 1994;Thieme et al, 1998;Rothe et al, 2000;Brandes et al, 2004), and DNA (Ade et al, 1992). NEXAFS has also been successfully used for the environmental study of coal (Cody et al, 1998), plant fossils (Boyce et al, 2002) or soot (Braun et al, 2007), which are not the subject of this contribution.…”