Quantitative Mapping of Structured Polymeric Systems Using Singular Value Decomposition Analysis of Soft X-ray Images

Abstract

The distribution of poly(acrylic acid) in a microporous polypropylene support membrane has been measured quantitatively by scanning transmission X-ray microscopy (STXM). Singular value decomposition analysis of X-ray microscopy images recorded at carefully selected photon energies was used to obtain quantitative maps of the polypropylene membrane and the poly(acrylic acid) gel, the two components of this system. The sample was studied fully hydrated in order to perform the quantitative mapping when the membrane is the same as in its state of application. Optimum strategies of data acquisition for quantitative X-ray microscopy analysis of radiation sensitive materials are discussed, along with a brief comparison of this technique to alternative methods of mapping the chemical components of structured multicomponent polymeric systems.

Speciation and Quantitative Mapping of Metal Species in Microbial Biofilms Using Scanning Transmission X-ray Microscopy

“…In addition to the two Fe chloride reference spectra, the stack fit included a reference spectrum without an Fe 2p signal (Figure 1b) that was extracted from a region in the biofilm (Figure 1c) where there was no detectable Fe signal. The resulting "Fe(II)-like" and "Fe(III)-like" component maps from this initial fit were then analyzed using threshold masking (33) to extract spectra corresponding to Fe(II)-rich and Fe(III)-rich regions. Analysis of the "constant" term component map or the residual did not indicate the presence of additional Fe species.…”

“…The quantitative Fe(II)-rich, Fe(III)-rich, and non-Fe spectra were used in the SVD procedure (33) (5), and 0.3-(2) µm, respectively. The cited uncertainties are associated with pixel-to-pixel variations due to inhomogeneous spatial distributions.…”

Quantitative Compositional Mapping of Core−Shell Polymer Microspheres by Soft X-ray Spectromicroscopy

“…29 Quantitative component maps for 10-90% (v/v) EDMA shell compositions are shown in Figure 3. These were derived using singular value decomposition (SVD) 29,40,41 of images at 285.1, 288.4, and 305.1 eV for each species. These results were carefully checked for reproducibility and sensitivity to small changes in the energy and intensity scales of the reference samples.…”

“…The incident flux, measured before or after each series of images, was used to convert the images to optical density. 29 …”

“…Since NEXAFS spectra for pure materials can be easily converted to accurate mass absorption scales, STXM can be used for quantification at submicron scales. 29 While radiation damage is still a concern, for equivalent spatially resolved analysis, it has been shown to be about 2 orders of magnitude lower in STXM than in analytical electron microscopy. 30 The present paper reports a study of the chemical composition of the 400-900 nm wide shell region of a particular family of microspheres, carried out to investigate the precision of STXM quantification.…”