Low-Dose Elemental Mapping of Light Atoms in Liquid-phase Materials Using Cryo-EELS
Daisuke Unabara1, Yohei K Sato1, Tasuku Hamaguchi1
1Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.
Analytical Chemistry
|July 31, 2025
Summary
This study introduces a new elemental mapping technique using cryo-electron energy loss spectroscopy (cryo-EELS) for nanoparticles in frozen solvents. The method accurately maps elemental composition in materials as small as 10 nm.
Area of Science:
- Materials Science
- Biophysics
- Electron Microscopy
Background:
- Cryogenic transmission electron microscopy (cryo-TEM) visualizes liquid-phase materials and biomaterials under cryogenic conditions.
- Conventional cryo-TEM provides structural data (size, shape, dispersion) but lacks elemental composition information.
- Elemental analysis is crucial for detailed material evaluation.
Purpose of the Study:
- To develop and validate a method for elemental mapping of nanoparticles and soft/biomaterials in frozen solvents using cryo-TEM.
- To integrate electron energy loss spectroscopy (EELS) with energy-filtered (EF) cryo-EM for elemental analysis.
- To achieve accurate and reliable signal extraction while minimizing electron dose.
Main Methods:
- Developed a cryo-EELS method integrated with EF-cryo-EM for elemental mapping.
- Employed the three-window method for cryo-EELS analysis.
- Implemented stage drift alignment and interexposure drift correction during image acquisition.
- Optimized electron dose for accurate signal extraction.
Main Results:
- Successfully generated elemental maps for nanoparticles as small as 10 nm in frozen solvent.
- Extended the technique to analyze protein-coated silica nanoparticles and hydroxyapatite (HAp) nanoparticles in vitrified solvent.
- Mapped silica (cores), carbon (protein shells), and phosphorus/calcium (HAp) within the same imaging area.
Conclusions:
- The developed cryo-EELS method enables high-resolution elemental mapping of nanomaterials in frozen solvents.
- This technique provides detailed compositional insights into complex biological and synthetic nanoparticles.
- The method is valuable for analyzing light elements in biological systems and nanomaterials.
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