Scanning X-ray Microscopy

NEXAFS microscopy is complementary to high chemical content microscopies, such as NMRI, ESRI, /aFTIR, /rRaman, and high spatial resolution microscopies, such as various electron microscopies. While AFM is surface-sensitive, STXM images are bulk-sensitive. 

Scanning transmission X-ray microscopy has been used most extensively for polymer research, e.g. for bulk characterisation of polymeric materials with chemical sensitivity at a spatial resolution of 50 nm [739], STXM has also been used for the analysis (morphology, size distributions, spatial distributions and quantitative chemical compositions) of copolymer polyol-reinforcing particles in polyurethane [740], Pitkethly [741] has reviewed the role of microscopy in the evaluation of fibre/matrix interfacial properties and micromechanical characteristics of fibre-reinforced plastic composites. 

The value of direct chemical-state sensitive NEXAFS type imaging of phase distributions in polymer blends is well known [715]. NEXAFS spectroscopy has been used for blend studies [736] as well as for the quantification of composition in heterogeneous polymers [742]. Characterisation of polymer interfaces is an important analytical need in many areas of technology. STEM and NEXAFS were used 

Ade et al. [11] have studied a multilayer laminate composed of PET/0.3 /u.m PU/1.0 /xm SAN/0.8 /xm CB-PVA (CB is carbon-black) by means of NEX-AFS microscopy using an STXM at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL) with the object of examining the extent of interpenetration of the SAN layer into the porous CB-PVA layer. Each of the four principle layers has a distinctly different NEXAFS spectrum (280-310 eV range). 

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There ate four main approaches to x-ray imaging contact radiography, scanning x-ray microscopy, holographic x-ray microscopy, and shadow projection x-ray microscopy. In the future, there will likely be phase-contrast imaging and photoelectron x-ray microscopy. 

Soft x-rays with wavelengths of 1—10 nm ate used for scanning x-ray microscopy. A zone plate is used to focus the x-ray beam to a diameter of a few tens of nanometers. This parameter fixes and limits the resolution. Holographic x-ray microscopy also utilizes soft x-rays with photoresist as detector. With a strong source of x-rays, eg, synchrotron, resolution is in the 5—20-nm range. Shadow projection x-ray microscopy is a commercially estabflshed method. The sample, a thin film or thin section, is placed very close to a point source of x-rays. The "shadow" is projected onto a detector, usually photographic film. The spot size is usually about 1 ]lni in diameter, hence the resolution cannot be better than that. 

The combination of scanning X-ray microscopy with NEXAFS offers the possibility to map the spatial association between NOM and mineral matter and between NOM compounds on a very hne spatial scale. This requires that the preparation of the specimen preserves the spatial assemblage. Suitable methods for sample preparation are described in Section 17.2.4. 

Takemoto, K., Ueki, T., Fayard, B., Yamamoto, Z Salome, M Scippa, S., Susini, J., Uyama, T, Midiibata, H and Kihara, H. (2003) Local distribution of vanadium in the living blood cells of asddians by fluorescence scanning X-ray microscopy ID21 at ESRF. J. Phys., 104, 333-336. 

NEXAFS experiments on NOM can be conducted in several modes that differ in the type of detected particle and objectives of the experiment transmission (X rays transmitted through the sample), fluorescence (fluorescent X rays due to absorption of the X-ray beam), or electron yield (photo-emitted electron) (Sparks, 2003). Alternatively, the techniques can be divided into full-field applications such as transmission X-ray microscopy (TXM) and X-ray photoemission electron microscopy (PEEM), in comparison to scanning techniques such as scanning transmission X-ray microscopy (STXM) and scanning photoemission microscopy (SPEM) that provide spatial information of elemental forms. 

Brandes, J. A., Lee, C., Wakeham, S., Peterson, M., Jacobsen, C., Wirick,S., and Cody, G. (2004). Examining marine particulate organic matter at sub-micron scales using scanning transmission X-ray microscopy and carbon X-ray absorption near edge structure spectroscopy. Marine Chem. 92,107-121. 

Hitchcock, A. P., Araki, T., Ikeura-Sekiguchi, H., Iwata, N., and Tani, K. (2003). 3d chemical mapping of toners by serial section scanning transmission X-ray microscopy. J. Phys. IV 104, 509-512. 

Rothe, J., Plaschke, M., and Denecke, M. A. (2004). Scanning transmission X-ray microscopy as a speciation tool for natural organic molecules. Radiochim. Acta 92,711-715. 

Schumacher, M., Christl, I., Scheinost, A. C., Jacobsen, C., and Kretzschmar, R. (2005). Chemical heterogeneity of organic soil colloids investigated by scanning transmission X-ray microscopy and C-ls NEXAFS microspectroscopy. Environ. Sci. Technol. 39, 9094-9100. 

PMMA-POSS15 cyclopentyl-POSS) as compatibilizer, using scanning transmission X-ray microscopy (STXM) and scanning probe microscopy (SPM) methods was examined. 

Shimura M, Saito A, Matsuyama S, Sakuma T, Terui Y, Ueno K, Yumoto H, Yamauchi K, Yamamura K, Mimura H, et al. Element array by scanning X-ray fluorescence microscopy after cis-diamminedichloro-plahnum(II) treatment. Cancer Res. 2005 65 4998-5002. 

There has always been a high degree of interest in visualizing not only objects, such as particles, molecules or atoms, but also structure. Scanning X-ray diffraction microscopy (SXDM, also termed X-ray spectromicroscopy), is a derivative of... 

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