Nanoscale observation of ouzo effect: droplet emulsion dynamics

Curious how the ouzo effect manifests at nanoscale?

Maria Vratsanos, Nathan Gianneschi, and their colleagues at Northwestern University and Penn State University, published recent work using their Hummingbird Scientific in-situ liquid flow TEM sample holder to characterize the surfactant-free, spontaneous, liquid-liquid emulsion dynamics of nanoscale structures formed by the ouzo effect. Homogeneously-sized nanoscale droplets formed in ternary systems of ouzo (ethanol and trans-anethole taste molecule) and water. A solution of ethanol and N,N-Dimethylaniline, another molecule that exhibits the ouzo effect, was also studied.

Figures showing a) Schematic of ouzo effect manifesting under bright field TEM. b) Brightfield optical, fluorescence microscopy, and in-situ TEM showing internal structure of trans-anethole droplets. c) Time-lapse micrographs of the evolution of three droplets with plot of the droplet diameter with respect to time in (d). Copyright 2023 The Authors. Published by American Chemical Society.

For the first time, droplet dynamics such as formation, growth, and movement have been observed at the nanoscale using liquid phase transmission electron microscopy (LPTEM). The growth constants and number of droplets were found to be directly proportional to the trans-anethole concentration, and ripening kinetics deviated from established models of Ostwald ripening. LPTEM also allowed characterization of the internal structure of the droplets, another first, demonstrating its utility for examination of soft matter, liquid-liquid phase separation systems, emulsifications, and their evolutions under dynamic conditions.


Maria A. Vratsanos, Wangyang Xue, Nathan D. Rosenmann, Lauren D. Zarzar, and Nathan C. Gianneschi, ACS Cent. Sci. 9 (1) 457-465 (2023) DOI: 10.1021/acscentsci.2c01194

Full paper Copyright © 2023 The Authors. Published by American Chemical Society.


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