Moving to STEM of Soft Matter

Session

EMAG - Bio, Cryo & Low-dose EM Imaging

Authors

Prof Andy Brown (1), Dr Martha Ilett (1), Dr Zabeada Aslam (1), Miss Natalia Koniuch (1), Dr Teresa Roncal-Herrero (1), Dr Sean Collins (1), Dr Nicole Hondow (1), Prof Rik Brydson (1)

Affiliations

1. School of Chemical and Process Engineering, University of Leeds

Keywords

STEM, EDX, EELS, cryo, soft matter 

Abstract text

The current generation of (scanning) transmission electron microscopes (S/TEMs) can readily provide atomic scale resolution to study the projected structure and chemistry of inorganic crystals and crystalline surfaces.  Organic compounds and soft matter however are so sensitive to electron irradiation that analysis by S/TEM generally requires limiting damage to the sample while extracting useful information [1].  This leads to the concept of dose limited resolution and informs how we might exploit improvements in detectors and techniques to obtain information at the highest possible spatial resolution in beam sensitive materials. 

 Here, we will explore the use of STEM (TEM/STEM and dedicated STEMs), direct electron detection cameras, EDX, EELS and integrated differential phase contrast plus cryo-transfer to show multi-modal analyse of materials sensitive to radiolysis damage can be invaluable.  We will report STEM enhancement of phase contrast in weakly scattering thin specimens such as zeolites and organic crystals by STEM iDPC and STEM scanning moire fringe imaging respectively [2]. We will discuss what can be achieved on the characterisation of nanoparticle dispersions intended for cellular and tissue applications.  This involves snap-freezing dispersions in vitreous ice and discussion of the challenges of representative analysis under cryo conditions or following vacuum drying [3,4,5].  

 We will demonstrate that these routes open up the possibility of understanding molecular packing and key interfaces in organic compounds and soft matter. This can provide important information in a range of applications for example for pharmaceuticals, in existing formulations such as amorphous solid dispersions and for new drug modalities such as polymer nanoparticle, delivery vectors. 

 

References

[1] Ilett et al. Phil Trans A 2020, 378 (2186), 20190601

[2] S'ari et al. Journal of Microscopy 2020, 279 (3), 197-206

[3] Wills et al. ACS nano 2017, 11 (12), 11986-12000

[4] Ilett et al. Sci Reports 2020 10 (1), 1-6

[5] Riedle et al. Small 2020 16(21) 2000486