ESEM (Environmental Scanning Electron Microscopy) allows the observation of liquids under specific conditions of pressure and temperature. Moreover, when working in the transmission mode, i.e. in STEM (Scanning Transmission Electron Microscopy), nano-objects can be analyzed inside a liquid. Those acquired images are quite similar to those obtained in TEM (Transmission Electron Microscopy) using a closed cell [1]. By implementing a Peltier stage in the tomography device which was developed for the characterization of the 3D structure of non-conductive and low-contrast materials [2], the acquisition of image series of wet samples (wet-STEM tomography) [3]. Moreover, in situ evaporation of water can be performed to study the materials evolution from the wet to the dry state.

  In our experiment, SBA-PMMA, a copolymer derived from styrene and metacrylic acid esters in aqueous solution, is chosen as the sample. A 3% PMMA shell, which plays the role of steric surfactant, has already included in the SBA particles. Some other surfactants can be introduced to further stabilize the latex for some special applications [4].

  We first present measurements of the sample temperature using different experimental conditions, to show that the sample can be preserved in the dry state. Then, we show series of tilted images that are acquired during in situ hydration / dehydration experiments. Reconstructed volumes are obtained using the image processing softwares etomo and Fiji (see Figure 1), and the resolution is calculated using Fourier Shell Correlation (FSC). The influence of irradiation damage on the reconstructed volumes are discussed.

  Afterwards, the volumes are segmented (see Figure 2) and quantified to follow the evolution of the microstructural parameters during water evaporation.  This shows the potentialities of wet-STEM tomography for the characterization of suspensions from the wet to the dry state.

[1] de Jonge, N., Ross, F.M. Nature Nanotechnology, 6, 695-704 (2011)

[2] Jornsanoh, P. Ultramicroscopy, 111, 1247-1254(2011)

[3] Masenelli-Varlot, K., Malchère, A. Microscopy and Microanalysis, 20, 366-375(2014)

[4] Faucheu, J., et al. Langmuir, 25, 10251-10258(2009)

Acknowledgements

The authors acknowledge the Consortium Lyon-Saint Etienne de Microscopie (CLYM) for the access to the microscope, the China Scholarship Council (CSC) and Institut Universitaire de France for financial support.

Figures:

Figure 1. XY slice obtained on an area containing different layers of latex particles.

Figure 2. 3D arrangement of the latex particles obtained by segmentation of the reconstructed volume.

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EMC Abstracts - https://emc-proceedings.com/abstract/environmental-tomography-of-liquid-latex-suspensions-in-stem/