MM-2004 (Savannah, GA, Aug 1-4, 2004) Methods and Examples of Quantitative Chemical Mapping using Synchrotron Soft X-ray Spectromicroscopy A.P. Hitchcock*, C. Morin*, L. Li*, J. Brash*, A. Scholl**, A. Doran** * Brockhouse Institute of Materials Research, McMaster University, Hamilton, Ontario, L8S 4M1 ** Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 Soft X-ray spectromicroscopy, also known as NEXAFS microscopy, is a powerful tool for quantitative chemical analysis. Due to its high chemical sensitivity, ability to penetrate water, and lower radiation damage than electron beam techniques, scanning transmission X-ray microscopy (STXM) is an ideal tool to study soft matter such as polymer, biological, and environmental systems [1]. While STXM is primarily a bulk probe, it has been used for some surface studies, such as protein adsorption on polymers [2]. Figure 1 illustrates C 1s STXM mapping of fibrinogen, a blood protein, on a polyurethane sample with two different types of aromatic filler particles. In this case the sample consisted of a ~150 nm thick microtomed section with selectively absorbed fibrinogen, and ~2 microns overlayer of water, sandwiched between two100 nm thick silicon nitride windows. Despite the relatively small amounts of protein, selective adsorption at the edges of the SAN particles is clearly identified and documented by the spectral fit to the extracted signal. X-ray photoemission electron microscopy (X-PEEM) is very surface sensitive. It is being used to analyze surfaces of polymers and biomaterials [3,4], despite challenges of radiation damage and sample charging. Figure 2 illustrates X-PEEM mapping of fibrinogen (Fg) on a thin film blend of polystyrene and polymethylmethacrylate (Fg-PS/PMMA) [4]. Here the spectral basis for the analysis is fully documented. Fg adsorbs selectively on the PS domains at sub-monolayer coverage. The near edge X-ray absorption fine structure (NEXAFS) signal provides the basis for detailed, quantitative speciation in both STXM and X-PEEM. However high quality spectromicroscopy data and accurate reference spectra are required for meaningful results. The aXis2000 package [5] provides a user friendly platform to derive quantitative chemical maps from a variety of types of X- ray spectromicroscopy data sets, including image sequences (also known as stacks [6]), linescan spectra, and point spectra. Tools and procedures to evaluate the precision and quantitative accuracy of a given analysis are incorporated in aXis2000. Methods for deriving quantitative maps will be illustrated with examples from STXM and PEEM studies of protein adsorption on polymers (e.g. Figs. 1 & 2), biofilms for environmental remediation, and industrial polymer samples. The capabilities and pitfalls of presently implemented methods will be outlined and challenges, along with potential opportunities for further development of analysis modalities, will be discussed. [7]. 1. H. Ade et al., “Chemical Appl. of Synchrotron Radiation” T. K. Sham, ed., World Scientific, 2002. 285. 2. A.P. Hitchcock, et al. J. Biomaterials Science, Polymer Ed. 13 (2002) 919. 3. C. Morin et al. J. Electron Spectroscopy 121 (2001) 203. 4. C. Morin et al. J. Electron Spectrosc. (2004) in press. 5. aXis2000 is written in Interactive Data Language (IDL), and is available from http://unicorn.mcmaster.ca/aXis2000.html 6. C. Jacobsen, S. Wirick, G. Flynn and C. Zimba, J. Microscopy 197 (2000) 173. 7. Measurements at 5.3.2 STXM and 7.3.1 PEEM at the Advanced Light Source, funded by DoE under contract DE- AC03-76SF00098. Research supported by NSERC (Canada) and the Canada Research Chair program. Microsc Microanal 10(Suppl 2), 2004 Copyright 2004 Microscopy Society of America DOI: 10.1017/S1431927604886926 1050