Scanning Transmission X-Ray Microscopy At The Canadian Light Source: Progress And Selected Applications In Geosciences

Abstract

Synchrotron-based scanning transmission X-ray microscopy (STXM) efficiently integrates X-ray microscopy and X-ray absorption spectroscopy (XAS) to provide quantitative, chemically specific imaging of elements, functional groups, bonding, and oxidation states in 2D and 3D modes at high spatial resolution (sub-10 to 30 nm), high energy resolution, and low radiation doses. STXM has been increasingly used to study various materials and samples for life, earth, planetary, and environmental sciences. In this progress report and minireview, the STXM principle and instrumentation of conventional STXM and the latest STXM-ptychography at the Canadian Light Source are first discussed. Then, two representative applications of STXM on geoscience-related samples, including magnetotactic bacteria, soil microaggregates, and related systems, are presented to illustrate the strong capabilities and suitability of STXM to elucidate complex systems, processes, and associations in the natural sciences. Finally, the potential applications and prospects of the STXMrelated techniques in characterizing precious extraterrestrial samples (e.g., lunar samples returned by China's Chang'e-5 mission) are briefly discussed.

Intracellular silicification by early-branching magnetotactic bacteria

“…This indicates that type I inclusions are composed of amorphous silica. Synchrotron-based scanning transmission x-ray microscopy (STXM) coupled with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy ( 21 , 28 ) indicate that type II inclusions are elemental sulfur (S 0 ) globules possibly with linear polymeric structures (fig. S3).…”

“…We investigated the chemical composition of the inclusions within WYHC-5 with the use of synchrotron-based STXM. STXM allows imaging and acquisition of NEXAFS spectra at high spectral (~0.1 eV) and spatial (~25 nm) resolution ( 28 ), which is able to provide detailed mapping of biological components ( 28 ). For STXM analyses, about 5 μl of the cell suspension was deposited onto the surface of silicon nitride windows (1.5 mm by 1.5 mm, 50-nm-thick SiN membrane window centered within a 5 mm by 5 mm, 200-μm-thick silicon frame; Norcada Inc., Canada).…”

“…For STXM analyses, about 5 μl of the cell suspension was deposited onto the surface of silicon nitride windows (1.5 mm by 1.5 mm, 50-nm-thick SiN membrane window centered within a 5 mm by 5 mm, 200-μm-thick silicon frame; Norcada Inc., Canada). STXM experiments were carried out on the 10ID-1 soft x-ray spectromicroscopy beamline at the Canadian Light Source ( 28 ), as described previously ( 21 ). The microscope chamber was pumped down to 100 mtorr after sample insertion and then backfilled with one-sixth atm of helium gas.…”

Identification of sulfate‐reducing magnetotactic bacteria via a group‐specific 16S rDNA primer and correlative fluorescence and electron microscopy: Strategy for culture‐independent study

“…This can be achieved by, for example correlative FISH‐SEM and NanoSIMS study of targets on a cover slide to simultaneously identify microbial phylogeny and function (Li et al, 2008; Li et al, 2017). Alternatively (step 5), targets on a standard TEM grid for FISH‐TEM identification are also suitable for coordinated synchrotron‐based STXM, advanced analytical TEM and NanoSIMS analyses (Ito et al, 2020; Wang & Li, 2022). This strategy, although not all‐inclusive, provides a feasible scheme to identify precisely MTB species/strains, and to investigate biomineralization of uncultured MTB in detail.…”

The Chang’e-5 Lunar Samples Stimulate The Development Of Microanalysis Techniques

“…Contributions to the current special issue include (1) a nondestructive study of natural color and the 3D morphology of a lunar meteorite and lunar soil simulant using a high dynamic range, color structured illumination microscope (HDR-C-SIM); 12 (2) improvement of atomic force microscopy (AFM) analytical technique for the accurate measurement of adhesion force in micro-sized lunar dust grains; 13 (3) development of Micro-X-ray diffraction (µXRD) methods for in situ identification of glass and minerals in extraterrestrial samples; 14 (4) development of analytical methods for the precise measurement of major and trace elements and Fe 3+ /∑Fe in geological samples using electron probe microanalysis (EPMA); 15,16 (5) study of the valence states of ironbearing phases in CE-5 lunar soil using advanced transmission electron microscope (TEM) techniques; 17 (6) in situ Rb-Sr dating of lunar meteorites using laser ablation multicollector-inductively coupled plasma mass spectrometer (MC-ICP-MS); 18 (7) development of analytical techniques for the determination of water content in geological samples using secondary ion mass spectrometry (SIMS) and nanoscale SIMS (NanoSIMS); 19 (8) development of the analytical method to measure the water content of a zircon hydrogen isotope using SIMS and the optimization of reference standards; 20 (9) a dedicated review of recent progress and selected applications of synchrotron-based scanning transmission X-ray microscopy (STXM). 21 Below, we summarize each of the contributions to this special issue:…”