From paints and inks to catalysts and drug-delivery materials, many advanced technologies rely on substances dispersed in organic solvents. Yet directly observing these materials in their native liquid environments has remained a major challenge, limiting scientists’ ability to understand how microscopic structures and elemental distributions influence performance. Researchers at Tohoku University have now overcome this barrier by extending cryo-electron transmission microscopy (cryo-TEM) to frozen methanol, opening a new avenue for studying materials under conditions much closer to their real-world operating environments.
Cryo-TEM is widely used to observe biological specimens in their native solution states and has recently been applied to non-biological materials dispersed in water. However, extending the technique to organic solvents has proven difficult because conventional sample-preparation methods were developed for aqueous systems. Rapid evaporation often causes organic solvent films to dry out or become too thick for observation, preventing the reproducible preparation of vitrified thin films suitable for cryo-TEM analysis.
To address this challenge, the research team developed a new sample-preparation technique called “gradient blotting.” Rather than blotting the entire TEM grid with filter paper, the method contacts only half of the grid, creating a gradual thickness variation across the grid. This approach consistently produces regions with optimal film thicknesses of approximately 100-300 nanometers for cryo-TEM observation.
The researchers also found that freezing methanol with liquid nitrogen often resulted in crystallization rather than vitrification. By instead using liquid ethane, commonly employed for aqueous cryo-TEM samples, they successfully produced amorphous vitrified methanol films.
Using these vitrified methanol films, the researchers evaluated resistance to electron-beam irradiation and found that the frozen methanol samples exhibited tolerance comparable to vitrified water. Electron energy-loss spectroscopy (EELS) successfully detected and visualized carbon and oxygen distributions originating from methanol, demonstrating that elemental mapping can be performed directly within frozen organic solvent environments.
The team further applied the technique to methanol solutions containing mesoporous silica nanoparticles. Cryo-TEM imaging clearly revealed the morphology and dispersion state of the nanoparticles embedded within the vitrified methanol films. By combining the new preparation method with a previously developed low-dose elemental mapping technique, the researchers also clearly visualized silicon distributions while minimizing beam damage.
The achievement expands the applicability of cryo-TEM beyond water-based systems and provides a new analytical tool for investigating materials under realistic processing conditions. Because organic solvents play central roles in numerous industrial and functional materials, the method could support the development and quality evaluation of paints, inks, coatings, catalysts, and drug-delivery materials.
Details of the findings were published in the journal Microscopy on May 29, 2026.
- Publication Details:
Title: Cryo-EELS elemental mapping of organic-solvent systems
Authors: Daisuke Unabara, Yohei K. Sato, Tasuku Hamaguchi, and Koji Yonekura
Journal: Microscopy
DOI: doi.org/10.1093/jmicro/dfag027
