# Multiscale study of water condensation on aerosols using in-situ Environmental Scanning and Transmission Electron Microscopies

Eric Ehret, Louis-Marie Lebas, Annie Malchère, Joseph Vas, Francisco Jose

Cadete Santos Aires, Lucian Roiban, Martial Duchamp, Karine

Masenelli-Varlot, Thierry Epicier

► To cite this version:

Eric Ehret, Louis-Marie Lebas, Annie Malchère, Joseph Vas, Francisco Jose Cadete Santos Aires, et al. Multiscale study of water condensation on aerosols using in-situ Environmental Scanning and Transmission Electron Microscopies. The 17th European Microscopy Congress (EMC 2024), Aug 2024, Copenhagen, Denmark. pp.08005, 10.1051/bioconf/202412908005. hal-05382302

HAL Id: hal-05382302

https://hal.science/hal-05382302v1

Submitted on 25 Nov 2025

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Distributed under a Creative Commons Attribution 4.0 International License
Multiscale study of water condensation on
aerosols using in-situ Environmental Scanning and
Transmission Electron Microscopies

Dr Eric Ehret¹, Dr Louis-Marie Lebas², Dr Annie Malchère², Dr Joseph Vas³, Dr Francisco Cadete Santos Aires¹, Dr Lucian Roiban², Dr Martial Duchamp³, Prof Karine Masenelli-Varlot¹, Dr Thierry Epicier¹

¹Universite Claude Bernard Lyon 1, CNRS, IRCELYON, UMR 5256, Villeurbanne, France, ²INSA Lyon, Universite Claude Bernard Lyon 1, CNRS, MATEIS, UMR5510, Villeurbanne, France, ³MajuLab, International Joint Research Unit IRL 3654, CNRS, Université Côte d'Azur, Sorbonne Université, National University of Singapore, Nanyang Technological University, Singapore, Singapore

Background incl. aims

Predicting cloud formation and the arrival of precipitation has always been a
hot topic in meteorology. With global warming and the many ongoing drought
events, this has become a major issue. Environmental scanning and
transmission electron microscopy (respectively ESEM and ETEM) can provide
valuable information to understand how clouds are formed by condensation
of water on submicronic aerosol particles. Indeed, Environmental Electron
Microscopy allows following the structural changes during the condensation
of water droplets, while controlling the relative humidity, from the dry state
up to fully hydrated conditions.

Methods

Sodium chloride particles are used as model marine aerosols. The deliquescence of crystals in the size range 100 nm – 1 µm is studied in ESEM (QuattroS from TFS) equipped with either a commercial Peltier stage (SE imaging) or a home-made tomographic stage (STEM imaging in both BF and DF modes) [1]. The deliquescence of smaller crystals is studied in ETEM (Titan ETEM from FEI/TFS) using either a commercial cryo-holder from Gatan/Ametek or a home-made system based on a Peltier micro-cooler [2]. More realistic aerosols, such as (non-hygroscopic) Arizona dust decorated with (hygroscopic) sodium chloride, are then studied.

Results

The evolution of the crystal facets and corners as a function of relative humidity is studied in ESEM in the SE mode, and is compared with the literature [3]. The measurement of the relative humidity allows a calibration of the other microscopy set-ups. Interestingly, oscillating behaviors at the beginning of deliquescence could be reproduced and followed in real time in STEM and TEM on smaller crystals (see Figure 1). They were found to match 2D simulations based on local fluctuations of the solute content. The
distribution of sodium chloride during hydration/dehydration cycles is also
analyzed.

Electron tomography is also carried out at multi-scale, in ESEM and ETEM on
hydrated samples and quantitative data can be extracted: crystal shape and
size as well as water droplet shape, and the aggregate shape and compound
distribution in the case of salted Arizona dust.

Conclusion

The multi-scale approach combining ESEM and ETEM enable the analysis of salt particles not only in 2D, but also in 3D, for different values of relative humidity. As irradiation damage can have large influence on the observed behavior and kinetics, the electron dose received by the sample is quantified and its effects discussed.

Acknowledgements

This work was funded by the French National Research Agency (project ANR-
20-CE42-0008-02). The authors thank the Consortium Lyon Saint-Etienne de
Microscopy (CLYM) for the access to the microscope. José Ferreira, Erwan
Allain, Christophe Goudin, Victor Trillaud (MATEIS) and Mimoun Aouine
(IRCELYON) are acknowledged for their experimental contribution.

Figure caption

water condensation on aerosols. (a) XY slice of a tomogram obtained in ESEM, showing NaCl crystals within water droplets. (b) Hygroscopic behavior of realistic aerosol (mixed phase Arizona dust and NaCl) with spatial localization and chemical identification of soluble phases during hydration (several T cycles).
**Graphic:**

<figure><img src="image_2.png" /></figure>

**Keywords:**

ETEM, ESEM, in-situ, liquid

**Reference:**

[1] Xiao, J. et al., Micron, 117 (2019), 60.

[2] Vas, J. et al., Microsc. Microanal., 28, S1 (2022), 818.

[3] Langlet, M. et al., Chemical Engineering Science 86 (2013) 78.